Document x5BeKY2r4Rvk6vbYDr7kMJLz1

1' "I-The Process of Leukemogenesis 6 Pichard D. Irons1f2and Wayne S. Stillman' ` School of Pharmacy; 2CancerCenter, University of Colorado Health Sciences Center, Denver, Colorado -5~lkemiasare monoclonal diseases that arise from cells in the hematopoietic stem and Ercgenitor cell compartment. Consistent with emerging models of carcinogenesis. wkemogenesis is an evoiutionary process that involves multiple independent genetic and ?=!genetic events. Over ths last halfcentuw a predominant paradigm has emerged to describe +xemia developing seconaary to alkylating drug therapy or exposure to benzene in which t zcressive dysplastic changes, accompanied by a distinct pattern of clonal cytogenetic ::-xmalities. give rise to acute myelogenous leukemia. Characterization of these clonal :.:3mosomal aberrations, together with observed alterations in other growth-promoting genes, -z-cvides a useful framework for studying chemical leukemogenesis ana for use in understanding :ne origins and development of ieukemia in general. Environ Health Perspect 104(Suppl 3:1239-1246 (1996) <si words: myelodysplastrc synarorne. acute myelogenous leukemia, leukemogenesis, ceizene best understood example of carcinogenesis in a normal, rapidly proliferaring tissue is carcinoma of the colon, in which ic appears that as many as five independent genetic and epigenetic changes may be required for the progression of a normal epithelial cell to a carcinoma cell (6.7)(Figure 1). This model is based on the seminal observation bv Vogelstein et al. that the incidence of ras-gene mutations increased dramatically as a function of the size and malignant phenotype of the tumor and that four molecular alterations accumulated in a. manner that paralleled the clinical and histopathological progression of the tumor (I).In addition to illuscrating the multifactorial nature of cancer development, these correlative studies reveal that the precise sequence of events is not a constant but chat individual cumors can vary in h e i r evolution. ?recess of Leukemogenesis Regulation of Hematopoiesis A grex deal of evidence suggess chat proto- - d i e m i a s are monoclonal diseases that into tissues, a n d the ability to grow in oncogenes and ocher growth-promoting originate from individual cells in the bone semisolid media. O n t h e o t h e r h a n d , genes such as chose encoding for cyrokines marrow. Like other cancers, leukemias leukemic cells often d o nor exhibit total or their receptors play an imporcant role in oken exhibit a progression in h e i r namral growth-factor independence w h e n first carcinogenesis and malignant transforma- history from cells that possess a phenotype introduced into culture. tion. Recent advances in cell and molecular xhibiting some remnant of normal differ- Consistent with present models for the biology have revolutionized our under- ;.ntiation to the progressive loss of matura- origin a n d progression of neoplasia, standing of the regulation of growth in ion ability and the development of an leukemia development has l o n g been normal hematopoiesis. Thereiore, a brief .gpressive undifferentiated malignant phe- thought to be a multistep process. Foulds summary of the functions of cyrokines in :iotype ( I ) . h common characteristic of first proposed a multistep progression in regulating normal hematopoiesis provides a mdignant neoplasms, including leukemias, which a normal cell must pass through a logical foundation for a discussion of the is abnormal regulation of cell growth. A n u m b e r o f distinct intermediate stages mechanisms of altered cell growh and dif- particular challenge to understanding the before a frank malignancy develops (2.3). ferentiation occurring in leukemogenesis. :ole of altered regulation of cell growth in Since that time. a variety of independent Three fundamental cellular processes that :he development of leukemia is that differ- observations have emerged to support the define hematopoietic cells are survival, pro- :nces in the behavior berween normal and conclusion that cancer in general is an evo- liferation, and differentiation. The survival n a l i g n a n t hematopoietic cells are often lutionary process in which multiple events and proliferation of hematopoietic progen- ubtle. For example, normal hematopoi- involving independent genetic alterations itor cells (HPC) are controlled by multiple ::ic progenitor cells possess some charac- in protooncogenes o r suppressor genes growrh factors or cyrokines with overlap- zeristics c o m m o n t o malignant cells, together with epigenetic or environmental ping functions chat act individually or in imong them: the abiliry to proliferate, sur- factors contribute to the development of combination to regulate hematopoiesis ( 8 ) . -.+e intravascular transit, and transmigrate the full malignant phenotype (4,5).T h e Recent studies support the conclusion chiit either interleukin-3 (IL-3) or granulo- cyre/macrophage-colony-stimulating hcror (GM-CSF) are required ro sustain chc via- -"!s Daper was presented at Benzene `95. An International Conference on the Toxici~v.Carcinogenesis. and --I3:oembology of Benzene held 17-20 June 1995 in Piscataway. New Jersey. blanuscripr received 16 January 2-6. rnanuscnpt accepted 10 June 1996. h p p o n e d by grants from the National Institutes of Health (ES06258). the American Petroleum Institute, and -5 University of Colorado Cancer Center Core grant P30 CA46934 Address correscmndence 10 Dr. 8.0 Irons. MTEHS Program C-235. University of Colorado Health Sciences :enter. 4200 East 9th Avenue. Oenver. CO 80262. Telephone: 1303) 315-7170. Fax: (303) 315-7223. E-mail. .:?ard.irons@uchsc.edu Abbreviations used: AML. x u t e myelogenous leukemia; p2AR. b2-adrenergic receptor: CKL. C-kir ligand: bility of stem cells or early HPC. Early HPC can also be recruited into active cycle in response to these same cyrokines or a sec- ond stimulus such as c-kir ligand (CKL), IL-6, or granulocyte colony-stimulating hccor (C-CSF) (9-11). Later c o m m i t t e d progenitor cells are controlled by linsllge- -`vlL. chronlc myelogenous ieultemia; ECGF, endothelial cell growth faaor: EGRl, early growth response 1 : G- 3,granulocyte colony-stimulating factor: GM-CSF. granulocyte/macrophagecolony-stimulanng facror; HPC, .enatopoietrc progenitor cells: IL. Interleukin: MCSF. macrophage colony-stimulating factor; MDS. myelodys: jstic syndrome: POGFR, plateletderived growth factor receptor: Rb. retinoblastoma: s. secondary. specific cytokines such as erythropoietin, macro p hage co lony-st i rnul a ring f:ist o r (M-CSF), G-CSF, and IL-5. Populations of Environmental Health Perspectives Vol 104.Supplement 6 December 1996 I239 IRONS AND STILLMAN DNA hypomethylation Chromosome: Alteration: Gene: 5q loss APC 1 2P activation K-ras II 1Bq 17P loss loss DCC P53 I Normal epithelium Hyperplastic epithelium Early adenoma Intermediate adenoma Late Carcinoma Figure 1. Changes that occur during the evolution of a typical colorectal carcinoma Schematlc reDresentationof a model of tumor progression in which indepenoent steps are required. leading to the activation of at least one protooncogene couoled with the successive loss of several tumor suppressor genes Adapted from Varmus and Weinberg (61 early H P C responding to IL-3 a n d GM- CSF exhibit extensive overlap. Although IL-3 or GM-CSF is required to sustain survival of early dormant progenitor cells (12),IL-3 apparently stimulates cells at an earlier stage of differentiation than GM-CSF (13).Early IL-3 responding populations support the development of T- and B- lymphocyte progeny as well as myeloid and erythroid lineages ( I 4 1 G ) . Because IL3 responsiveness is a characteristic of H P C at multiple levels of differentiation, H P C responsive to GM- CSF may represent a subpopulation of multipotential cells that respond to IL-3 ( 1 7 ) .The processes that govern differentiation of H P C are less well understood and are thought by many to be governed via stochastic mechanisms. Neverrheless, it is reasonable to infer that differentiation and lineage commitment are at least indirectly influenced by envi- ronmental factors (e+. cytokines). The role of altered regulation of cyrokine expressioniresponse in leukemogenesis is complex, with consistent enhanced expression of GM-CSF or IL-3. resulting in profound myelodysplastic changes (18-20). Altered regulation of clonogenic response to GM- CSF features prominently in both human and murine myeloproliferative disorders and is a frequent early obsenation in the development of acute myelogenous leukemia (AML) (5,21).Repeated exposure of mice to benzene in vivo enhances GM- CSF response (.?2),a n d chronic exposure to high concentrations induces a per s is t en t m y el op ro 1i fer a t i ve disorder (23.24).Moreover, the benzene merabolire, hydroquinone, selectively enhances donogenic response to GM- CSF in murine and human bone marrow cells (25-27).To date, alterations in expression ofM-CSF/FMS have not yet been shown to result in abnormal myeloid proliferation. Relationship between Leukemia, Preleukemia, and Myelodysplastic Syndrome It is generally recognized that chromosomal aberrations or deletions can alter the regulation and function of protooncogenes and other growth-promoting series. This, together with our growing knowledge of the function and role of cyrokines, their receptors, prorooncogenes, and suppressor genes. provides a useful framework for analysis of the respective roles of altered cell growth and differentiation in chemical leukemogenesis. To this end, an impressive literature exists that describes the natural history of leukemia secondary to alklaring drug or occupational exposure in which the development of AML is a ) preceded by progressive dysplastic or "preleukemic" changes, and 6) accompanied by a distinct pattern of clonal Togenetic abnormalities. The concept of preleukemia originated around the turn of the century with the observation that AML could be preceded by a y o p e n i c dysplasia involving one or more hematopoietic cell lines (28).However, preleukemia was nor generally accepted as a clinical entity until the widespread introduction of radiation and chemotherapy in the treatment of other y p e s of cancer. It is now widely recognized that persistent cyropenias and other blood dyscrasias, including dyserythropoiesis, dysgranulopoiesis, and dysrnegakaryopoiesis, frequently precede the onset of leukemia in patients developing AML secondan to exposure co benzene or alkylating agents (1,29-32).Over the past decade the term preleukemia has been largely supplanted by the more functional classification of the myelodysplastic syndromes (MDS) by the fast atom bombardment (FAB) ( 3 3 ) .Differences in growth and differentiation between MDS and AML find analogy in the progre!,silr: solid tissue tumors from metaplasi,i -,.: dysplasia to carcinoma. This ohser\.aI:,,:, together with the frequent prog:essiol: secondary s-MDS to frank A,,tL. lead. : the inescapable conclusion that ,/. AML should be considered a sincic di.. continuum when viewed in thr i c j l l ( y chemical leukemogenesis. As a secondary malignant!., .L. clearly dominates the leukemia liter:]:..-. At present, the world literature conr..::. approximately 38,000 cases of indiviiL,,. treated with alkylating agents or radia:;,,:, for primary malignancies or immune di,,.:. ders that have been followed for dcvc: . ment of secondary malignancies. chc .' prominent of which is AML. . cally involve M1, M2, M4.L i b . bu: M 3 or M j subtypes of AML, based OP ., FAB classification system (34',3.i1F.F\,:: these studies at least 1321 cases oc .A\:. and 320 cases of MDS have been rcpor!:.: (29,30,36-57).If one includes all ;.:.;. attributed to solvent exposure in gene:.,. - benzene specifically, whether anccciur..' reported in case-control or coho:; ire, the total number of secondan- icxic- approaches 2100, over 9696 of wiiici- .:. MDS/AML (44,58-70).The frequenq ; secondary AiMLlMDS varies markc,,. depending on individual therapeutic r"'- men bur historically has ranged Sera.::.:. 0.6 and 17%, with relative risks averagir.g about 100-fold (range 9-320 X'!T.h y ; : srudies establish a consistent and very st:. ; panern in which the developmenr of .:- :1 is preceded by a period of preleukernia ir ' to 80% of the cases and is accompanied Y clonal yogeneric abnormalities involvr.; loss of all or parr of chromosomes j a n i - (Table 1).O n average the frequency of dek- [ions or loss of chromosomes 5 and - .:i studies of patients who develop ,LID.( :>: AML after antineoplastic therapy rar- :. between 85 and 95% (71-76). T h e 5. .. - yogeneric abnormalities occur much : frequently in a% novo .WL:in 6GO d;. cases chromosomes j and 7 were obscn.;. in 4.2 and 4.4%, respectively, and simu1::- ., neously in 3.2% (77,78).consistent \vi::. the evolution of s-AML described pr.i.\-.- ously, most patients presenting \rich clo:;L. chromosomal aberrations involving rht. -of all or part of chromosomes 5 or e A . . a preleukemic phase prior to the OIISC AML (79).Analysis of the specific pat;--:- of cytogenetic involvement in AML do.,. oping secondary to benzene exposure. :* complicated by the ambiguities common associated with the characterization 1240 Environmental Health Perspectives Vol 104, Supplement 6 9 December 1996 n SECONDARY LEUKEMOGENESIS Table 1. Cytogenetic characteristicsof secondary acute myelogenous leukemia of these diseases. A number of gene loci Clonal aberrations De novo Secondary -5. -7, sq-, 7q- orboth have been mapped to chromosome 7; how- De novo Secondary ever, t h e i r f u n c t i o n ( s ) remains IargeIy 3:udv AML. Yo AML. % AML. Oo' AML,yo unknown (80.However. recent progress in the mapping of genes to the region of chro- .'XL (77) :3eau et al. (731 ;Jwley et al (72) 54 56 - 73 97 96 12 16 - mosome 5 involved in s-MDS/AML. pro92 vides a l o g i d scarring point for a discussion 3wIey et al. (71) - 100 - 90 of possible mechanisms of leukemogenesis. "dersen-Blergaard et al [ 121) ,Vald and Conner ( 722) - 86 87 -- 89 Deletions of all or parr of chromosmes 5 or 80 7 a_r-e t-he earliest clonal dtentions that have 'Jiteiman et a1 (59) 3 o m b et al (617) 3gioli er al 1611 24 29 83 75 88 1-2 20 84 been detected in MDS/A,LIL. Deletions 67 46 associared with Sq- in s-MDSIAML are usuallv intersticiai without uanslocation of the dlleted material (73,8/3.The variabil- .:cposure in occupational ,and retrospective aberrations involving bands 1l q 2 3 a n d ity o f the breakpoints, together w i t h ..:dies. Issues related to the specificity and 21q22 (84).Although it has been hypothe- identification of the critical region (Sq311, incensity of benzene exposure notwith- sized that benzene metabolites may inter- suggests that the relevant genscic event mav standing, the classic pattern involving a fere with topoisomerase I1 (85),the pattern be the deletion of a critical gene sequence high frequency of loss of all o r part of of leukemias and chromosomal aberrations rather than consistent juxrsposition of chromosomes 5 and/or 7 is also observed typically associated with inhibition of this D N A sequences that may occur in chromo- in studies o f patients occupationally enzyme has yet to be observed in occupa- some translocation (Figure ?) (73).A clus- exposed to benzene specifically or solvents tionally exposed populations. ter ofgenes involved in the regulation of m o n g which benzene is the only recogr.ized leukemogen (58-6I,G3,65,80,81). Ths consistency of this pattern is all the 5-/5q-: A Model for the Pathogenesis of Leukemia hematopoiesis is louted at qj1 on chromosome j (Figure 3 ) . These include GM-CSF, 1L-3, IL-4, IL-5, CD14 (which inore impressive when one considers chat T h e pattern of reoccurring chromosomal encodes a myeloid-specific surfice molecuie the association between exposure and "0- abnormalities associated with the develop- that has structural characrerisdcs of a recep- genetic abnormalities in occupational ment of leukemia can be used as a guide in tor), and early growth response 1 (EGR1) studies is invariably diluted; i.e., studies understanding the etiology and pathogenesis (an EGR gene with @$-like properties) (88). providing the grearest detad on cytogenetic abnormalities are weakest in the characteri- zation of exposure criteria. Independently, ::cent studies of peripheral lymphocyes in Chromosome 5 knzene-exposed individuals in China have :tiown that benzene exposure induces aneu- ploidy of C-group chromosomes, with an ispecially strong effect on chromosome 7. Both hyper- and hypodiploidy of chromo- 5ome 7 occurred more frequently in benzene-exposed workers than in matched 12 Lontrols (52). Other nonrandom clonal ihromosomal abnormalities, such as +8 or - 1 i , have been observed to be increased in . [her exposed or nonexposed populations, 1 -..cpending on the studv (58-60,62,81). I hese observations suggest that although Gome chromosomes other than 5 or 7 cm be involved in the pathogenesis of hiML iecondary to exposure to benzene or dwnotherapeutic alkylating agents, they ..re not useful in discriminating benveen J tiouo and S-AML (83).More recently, a :brinct pattern of secondary AML has I"' x n observed following therapy with drugs :irgeting DNA-topoisomerase 11. The pat- 7 . m of ;LLlL developing as a consequence I qjr'sxposure to these agents, examples of '.viiich include ecoposide and teniposide. 7 ::lsludss t h e notable absence of P Figure 2. Fragile site on cnromosome 5 associatedwith region of critical deletion in patients .vith t-AML Ven:c3l .releukemic phase, frequent presentation of bars indicate deleted segmenrs and numbers indicate number of pattents with same delerion. Oashed bars 1x11t 1 113 subtype. and balanced chromosome cate smallest overlapping region of 5q31 Reproduced from Rowley and Le Beau(881, with permission Environmenml Healrh Perspectives 9 Vol I 04, Supplement 6 December 1996 124' IRONS AND STILLMAN Chromosome 74 :HP 1 --%2 1 31 I GM-CSF !E - ~-~ ~ Figure 3. Genetic map of genes located in and adjacent to the 5q31- critical region deleted in patients with t-AML. Modified from Rowley and Le Beau (881.Abbreviations: PPAR. P2-adrenergic receptor; ECGF, endothelial cell growth factor: PDGFR. platelet-derived growth factor recePtor. There is no evidence for homozygous dele- don of any of these genes in AML, such as has been described for retinoblastoma in which the absence of one allele of retinoblastoma gene is followed by a second somatic mutation, resulting in loss of both copies of the gene (89).T h e most consistent deletion associated with 5q31- appears to involve the loss of one allele encoding either GM-CSF or EGRl (88). Close to, but lying ourside of, the critical region is the procooncogene, c-fms, the receptor for M-CSF rhar acts exclusively on cells of monomacrophage lineage (PO). Ostensibly, a critical role for c-fmz in the development of AML is an attractive hypothesis in that it encodes a cytokine receptor. However, the weight of evidence suggests that c-fjns is probably nor involved in early events in AML development. M-CSF and c-fms lie ourside the critical deletion region at 5q31 (881, and although FMS expression can be detected on leukemia cells in approximately 30% of AVLs. abnormal myeloid proliferation has yer to be demonstrated as a result of inappropriate expression of M-CSF or FMS ( 5 ) .Nevertheless, the incidence of point murations in the c-fms gene in AML or hlDS has been reponed to be 13% in one series, suggesting that subtle changes in c-jvs expression may contribute in some way to the development of the malignant phenotype (31). At present. there are at least two molecular hypotheses for the role of jq- abnormalities in the development of MDSIAML. First is the loss of a single allele of a heretofore unidentified rumor suppressor gene that results in production of a nonfunctional protein; chis would bc analogous to the inactivation of p53 by point mutation. The second hypochesis is that loss of a single allele leads to altered gene dosage and a reduction in the level of gene product, such as GM- CSF. A third possibility is that involvement of intact genes adjacent ro the intersririal deletion cannot at this time be entirely excluded since their &; tion could ostensibly be influenced b!structural changes that have occurrrd ill the chromosome. In addition to early involvernrn: (,i genes on chromosome 5 , a growin; nui:-. ber of prorooncogenes have been rc?cl:. i to undergo structural or functionai %:, ations in AML with widely differing quency. These have becn the subiec: ., number of reviews (592-94). T o datc. :III single or consistent pattern of protoonc(,. gene involvement has been associated \vi& h l L development, suggesting that muiri- ple genes may inreract via differenr ,L-xc.~~ways in the evolution of the diseasc. discussion will focus only on a sma!: 2,. bcr of these genes. T h e human r,i: g. encode p21 proteins that appear to pi;. .. important role as second messengzr. :E ryrosine kinase receptor-mediated sig::a: rransducrion (95).I t has been h!.?orht-sized char ras mutations may tc2:ur: prominentlv in the development of c - . i i ! I (36).However, what role ras m u t a : i , ~ ; ~ \ play in the development of either n':or s-AML remains uncertain. Ir. .: .. .' number of studies, ras procooncog=-.: . . sarion, principally N-R4S, has bezr. . ously reporred to occur in about 2 5 " cases of de aovo AML (9295).H o ~ t ~ c : . clonal chromosomal aberrations have bcrn demonstrated to precede ras involsemenr in the evolution of the disease (97,PP and. when identified, ras mutations rend ;c 5: present only in subclones of the I c s k : : - : ~ cells (97,YY). T o date, RAS invol.-:z. ::: has nor proven to be either a propc?,:': indicator or to correlate with FAB subr.-?~. From these studies it appears [ha: ~(7: mutation is an unlikely early event in . U l L and is insufficient to cause t h e ~ S C ~ S K . However, ras activation can occur a: a number of stages in the developmcr,: 01' .LVL and it cannot be excluded thzr may play a role in the evolution or ?re; .- sion of at leasr some cases of AM!- ,' ' The p53 gene encodes a phosphopiri:::rl nuclear transcription factor char is spri:i~ll! regulated within the cell during the cycle. T h e wild-type protein is kno\Yrl 10 limit cell growth apparently by nvo in&pendent mechanisms: mediating aFo?r[":\ and as a checkpoint, regulating rh;. it of GI (101). OFcen referred to as ri 51: suppressor gene, inactivation of p;." : .!n important event in the rransform.iric1: (11 many tumors and is the most frrqu:nrl! encountered gene mutation in hum.]" cancer (IO?). Inactivarion oi p 5 3 15 involved in the progression to blast crisi? in 1242 Environmenral Yealth Perspectives Vol 104. Supplement 6 December I996 SECONDARY LEUKEMOGENESIS r 30 co 3096 ofchronic myelogenous leukemia CML) cases, but it is only encountered in a in few percent of IMDSIAML cases (103). \Xithin this small subset of AMLs, p53 Enhanced GM-CSF response 5qloss GM-CSF EGRl? increased Activation stromal N-ras GM-CSF C-fmS 17P loss p5YRb activation c-rnyc of .-ac:ivation is a late event and is apparently m- . ,ociated with loss of a differentiated cell 1 11 I red :,isnotype, aggressive course. and a poor er- irognosis. T h e retinoblastoma (Rb) gene re- ..vas the first identified tumor suppressor IFa gene and like p53 encodes a phosphonuclear 1 I I I IHyperplasia Metaplasia dependence Dysplasia . I no protein that is involved in regulating critical -0- events in the cell cycle (IU4,105).Absent or Figure 4. Hvpothetical model for the evolution of secondary leukemia involving 5q- Schematic representationof a ith decreased expression of Rb protein is model of abnormal myeloproliferative progression in which early events, including alterations in cytokine response ,ti- .,bserved in approximately 3096 of XvIL and loss of heterozygosity (5q-). are followed by activation of at least one protooncogene coupled with the suc- :hn, i.s - i s s and is associated with a particularly cessive loss of a tumor suppressor gene ..!smal response to therapy (106107). mies A Modelfor Leukemogenesis than the exception in the evolution of exogenous GM-CSF occurring in physs-Ah4L, and abnormal y o k i n e production iologic response to increased apoptosis an Up to this point the discussion has focused is f r e q u e n t l y e n c o u n t e r e d in cases o f would drive cell proliferation, leading to an in exclusively on the role of clonal hemato- MDS/AML (113-116). increase in overall cell turnover in the nal poietic stem and progenitor cell abnormali- Alternatively, o n e c a n p r o p o s e a n affected clone. This model is consistent with le- ties in the development and evolution of integrative model of leukemogenesis that is the regulatory paradox in MDS in which i r e LLDSIAML. Another hypothesis has been compatible with boch clonal and microenvi- bone marrow hyperplasia is accompanied by YIL :roposed in which altered growth factor ronmental involvement in the development ineffective hematopoiesis and cytopenias. )ns xoduction by fibroblasts, endothelial cells, and progression of these myeloproliferative Subsequent events involving genes linked 7vo ;nd macrophages may feature prominently disorders. In hematopoiesis, there is con- directly or indirectly to cell survival and rge in the development of leukemias (108).As siderable evidence that cell viability and macuracion (e.g., ras. p53. or Rb) could 3.1- the basis for a stand-alone theory of leuke- cell growrh are functions that can be &so- enable the escape of the subclone from the iri- mogenesis, each of these alternatives pos- ciated ( I 17).Raza et d. ( I 18,119) have apoptotic treadmill and development of J c sesses individual strengths and weaknesses. recently reported an increase in both cell frank XML (Figure 4). 'er , .A diverse set of observacions argues persua- turnover and apoptosis in bone marrow of Ths model is only one possible explana- ten sively chat the ultimate clonal derivation of patients with MDS relative to normal bone tion for the origins a n d progression o f cnt most cases of AML and M D S are HPC marrow chat is in sharp contrast to A M L , leukemia that is compatible with roles for nd, sentially restricted to the myeloid lineage in which proliferation is high but the fre- both clonal and microenvironmental events. be I103-112). Superficially, a clonal lesion quency of apopcotic cells is low. A chromo- The earliest observations associated with the nic \vould appear to be incompatible with the somal aberration in an early progenitor cell development of MDSIAML suggest that a ent n o t i o n that persistent a n d progressive c o u l d result i n allelic d e l e t i o n o f o n e relatively small number of alternative events ,tlC myeloproliferative disease could arise as a GM-CSF gene, resulting in a commensu- predispose the development of leukemia. Pee consequence of alcered microenvironmen- rate decrease in intracellular GM- CSF. These most likely involv: a clonal chromoras tal influences that are ostensibly indepen- Using antisense technology, Pech and co- somal abnormality together with alcered b1L dent and oligoclonal. On the other hand, workers provide evidence that low-level regulation of cyrokine response. However, .se. how allelic deletion of a cyrokine gene such autocrine reqdation of GM-CSF may- -reg- the diversity of gene involvemenr in later t a .IS GM-CSF in a single clone of progenitor date surviva in early progenitor cells inde- stages of AML progression is consistent of i d s can predispose to a series of events that pendent o f exogenous GM- CSF that is wirh an emerging pattern in cancer biology AS utlimately leads to AML remains a niggling associared with proliferation (120).If intra- in which multiple alternative genetic path- -es- cnigma. T h e basis for the argument for a cellular GM-CSF were insufficienr ro ways converge in the development of a J0). stromal origin is that multiple peripheral suppress apoptosis in maturing cells of the specific tumor r p e . cin qnopenias and dysplasias are che d e rather affected clone. ;f corresponding increase in dly ;ell to de- REFERENCES oris gth nor 1. Foucar K, McKenna R W . Bloomfield C D , Bowers TK. Brunning RD. Therapv-related leukemia. Cancer 43:1285-1296 ( 1979). 5 . Willman CL, Whittaker ,MH.The molecular biolog of acute myeloid leukemia. Proro-oncogene expression and tunction in n o r m a l and neoplastic myeloid cells. Clin LAb Med , an 2. Foulds L. Nroplasric Development. New York:Academic Press. 10:769-796 (1990). 1 of 1969. 6. Varmus H, Weinberg RA. Genes and rhe Biology of Cancer. 1clv 3 . Foulcis L. T h e experimental study of tumor progression: New York:Scientific American Library. 1993. Id1 i IS .Ireview. Cancer Res 14:327-339 (1954). 4. L n d H, Parada LF. Weinberg RA. Tumorigenic conversion of primary embryo fibroblasts requires at least two cooperxing 7 . Vogelsrein B. Fearon ER, Hamilton SR, Kcrn SE. Preisinser AC, Leppert M, Nakamura Y, White R, Smits Aklkf, BOSJL. Genetic alterations during colorecrsl-rumor drvelopmcnc. 5 in oncogenes. Nature 304:596-602 (1983). N Engl J bled 3I9(9):525-532 ( I 988). Environmental Health Perspecnves Vol 104. Supplement 6 December 1996 I243 IRONS AND STILLMAN li 8. Leary AG. Zeng H Q , Clark SC, Ogawa M. Growth factor 27. Irons RD. Stillman K'S. Impact of benzene metabolires on requirements for survival in Go and enrry into the cell cycle of ferentiation of bone marrow progenitor cells. In: Benzene 'I primitive human hemopoietic progenitors. Proc Natl Acad Sci International Conference on the Toxicity. Carcinogenesis. A;,<; USA 89:4013-4017 (1992). E idemioloq of Benzene, 17-20 July 1995. Piscata~ray.1 9. Ikebuchi K , Clark SC, Ihle J N , Souza LM, Ogawa M. J s r r a c t. Granulocyte colony-stimulating factor enhances interleukin 3- 28. Laycon DM, Mufti GJ. Myelodysplastic syndromes: [heir hi.- dependenr proliferation of multipotential hemopoietic progeni- to?, evolution and relation to acute myeloid leukaemia. Ri;: tors. Proc Natl Acad Sci USA 85:3445-3449 (1988). 53:423-436 (1986). 10. Ogawa M, Matsuzaki Y, Nishikawa S, Hayashi S-I. Kunisada "3. Casciato DA. Scott JL. Acute leukemia following prololl; T, Sudo T, Kina T, Nakauchi H, Nishikawa S-I. Expression cytotoxic agent therapy. btedicine 58(1):32-47 (1979). and function of r-kit in hemopoietic progenitor cells. J Exp 30. Anderson RL. Bagbp G C Jr. Richert-Boe K. Magenih 1. Med 174:63-71 (1991). Koler RD. Therapy-relared preleukemic syndrome. Can, 11. Bodine DM, Orlic D. Birkett NC, Seidel NE, Zsebo KM. 47: 1867-1871 (1981). Stem cell factor increases colony-forming unit-spleen number 31. Coltman CA. Dahlberg S. Treatment-related leukemia. N En,. in v i m in synergy with inrerleukin-6, and in vivo in SLNd mice J Med 323:52-53 (1990,. as a single factor. Blood 79:913-9 19 (1992). 32. Advani SH. Doval DC. Gopal R, Nair C N , Kurry P\:. 12. Gibson FM, Bagnara M,loannidou E, Gordon-Smith EC. Therapy-relared leukemia. Oncology 40268-272 (1983). Interacrion of granulocyre-macrophage colony-stimulating fac- 33. Bennett JM, Catovsky D. Daniel MT,Flandrin G. Galr,?:. tor and interleukin-3 in human long-term bone marrow cul- DAG, Gralnick HR, Sulran C. Proposals for the classitica~i,,- ture. Exp Hematol 2 0 2 35-240 (1992). of the myelodysplastic Tndromes. Br J Haematol 5 1:1Si-: 13. Leary GA, Yang YC, Clark SC, Gasson JC, Golde DW, Ogawa (1982). M. Recombinanr gibbon interleukin-3 supports formation of 34. Bennett JM, Catovsky D, Daniel MT, Flandrin G. Gal: human multilineage colonies and blast cell colonies in culture: DAG, Gralnick HR, Sultan C. Proposed revised criteria tor .. : comparision with recombinant human granulocyte-macrophage classification of acute myeloid leukemia. Ann Intern .:Li\ colony-stimulating factor. Blood 70:1343-1348 (1987). 103:626629 (1985). 14. Tsunoda J-I, Okada S, Suda J. Nagayoshi K, Nakauchi H , 35. Levine EG, Bloomfield CD. Leukemias and myelodysplac:;, Hatake K, Miura Y, Suda T. In vivo stem cell function of inter- syndromes secondan ro drug, radiation, and environmcn:;, leukin-3-induced blast cells. Blood 78:3 18-321 (199 1). exposure. Semin Oncol 19(,1jA7-84 (1992). 15. Wood PMD, Jordan RK, Givan AL, Brooks CG. IL-3 and 36. AIlan WSA. Acure m!-eloid leukaemia after creatmenr {I;:: IL-4 affecr thymocyte differentiation in organ culture. cyrosratic agents. Lancer October 10:775 (1970). Immunology 71:83-89 (1990). 37. Barrolucci A\, Liu C. Duranr JR, Gams RA. Acute ni!.r;c,_ 16. Soloff RS, Dempsey D, Jennings SR, Wolcocr RAl, Chervenak nous leukemia as a second rnalignanr neoplasm follo\vin; R. Characterization of the progeny of pre-T cells maintained in successful rrearment of advanced Hodgkin's disease. h:... v i m by IL-3: appearance in rhe periphery and Vb utilization in j2:209-22 13 (1983t. vzvu. Cell Immunol 135:132-142 (1991). 38. Boivin J-F, Hutchison GB. Leukemia and other cancers 3;;;- 17. Koike K, Ogawa M, Ihle JX, A4iyake T, Shimizu T, Miyajima radiotherapy and chemocheiapy for Hodgkin's disease. .ISA:. A, Yokota T, .4rai K-I. Recombinant murine granulocyte- Cancer Insr 67(4):,j1--60 (1981). macro hage (GM) colon!--stimulating factor supports forma- 39. Coleman CN, Williams CJ. Flinr A, Glarstein EJ, Rosenbc:; tion oPGM and mulriporential blast cell colonies in culture: SA, Kaplan HS. Hematologic neoplasia in patients [teared fa: comparison with the effects of interleukin-3. J Cell Physiol Hodgkin's disease. X Engl I Lied 297:1249-1252 (13-71 1313458-464 (1987). 18. Chang JM, Metcalf D, Lang RA, Gonda TJ, Johnson GR. 40. Devereux S. Therapr associated leukaemia. Blood Rc I. 5:138-145 (1991). Nonneo lastic hemaro oieric myeloproliferarive syndrome 41. Greene MH. Harris EL. Gershenson DM, Malkasran GC - induced %y dysregulate! mulri-CSF (IL-3) expression. Blood Melton LJ 111, Dembo -41. Bennett JM, Moloney WC. E' : 73:1487-1497 (1989). 19. Lang RA. Metcalf D , Gough NM, Dunn AR, Gonda TJ. Expression of a hemopoieric growrh facror cDNA in a facror- ,TD- Ir. MelDhalan mar be a more uotent leukemogen r-: Bcyckphos Lamide. ,inn intern Med \05:360-367 (1986). 42. Grunwal H W , Rosnei F. Acute myeloid leukemia follon.ins dependent cell line results in autonomous growch and tumori- treatment of Hodghn's disease: a review. Cancer 50:676-6S? eniciry. Cell 43531-54' (1985). (1982). 20. !toclung C, Loliger C, Kawai M. Suciu S, Gough N, Osterrag 43. Grunwald HW, Rosner F. ..\cure leukemia and immunosuc- W. Identification of genes involved in growth autonomy of pressive drug use: a rmiew of patients undergoing immunosu:-- hematopoietic cells by ana+ of iacror-independent mutanrs. pressive therapy for non-neoplastic diseases. Arch Intern J:.-i Cell 532369-879 (1988). 21. Young KM. Myeloproliferarive disorders. Ver Clin N Am: Small h i m Prac 15:769-'S1 (1985). 139:461-466 (1979). 44. Hoppe RT. Secondary leukemia and myelodysplastic syndr( . after rreatmenr for Hodgkin's disease. Leukemia 6 :.SL. ~ 22. Dempsrer AM, Snyder C.4. Short term benzene exposure pro- 4):155-157 (1992). vides a growrh advantage for gtanulopoiecic progenitor cells 45. Kantarjian HM, KeatinS MJ, Xalrers RS, Smith TL. Cor: over erythroid progeniror cells. Arch Tosicol 64:539-544 McCredie KB, Freireich EJ. Therapy-related leukemia .liiL (1990). myelodysplasric syndrome: clinical, qogeneric. and p r o g i i ~ ~ ~ ~ - 23. Farris GM, Everirr JI, Irons RD, Popp JA. Carcino enicinr of features. J Clin Oncol 1+(12):1748-1757 (1986). inhaled benzene in CBA mice. Fundam Appf T O X ~ C O4~6. Kyle RA, G e r a MA. Second malignancies after chemorhcri?,.. 20:503--507 (1 993). In: T h e Chemotherapy Source Book (Perry hlC. :.. 24. Cronkite EP, Drew RT, Inoue T, Hirabayashi Y, Bullis JE. Baltimore:Williams &Wilk?ins. 1i992; 689-702. Hematotoxicity and carcinogeniciry of inhaled benzene. 47. Kyle RA. Second malipancies associated with chemorher:ii. . Environ Health Perspect 81:97-108 (1989). 25. Irons RD, Stillman WS. Colagiovanni DB. Henry VA. Synergistic action of the benzene metabolite hydroquinone on tic agenrs. Semin Oncol9(1):131-142 (1982). .. 48. Lishner M, Slingerland J, Barr J, Panzarella T, Degencior:. Sutcliffe S. Second malignant neoplasms in patients wirn :: - myelopoietic stimulating acriviry of granuloc).re/macrophage Hodgkin's lymphoma. Hematol Oncol 9:169-179 (1 99 1 i . colony-srimulating facror in virru. Proc Natl Acad Sci USA 49. Pedersen-Bjergaard 1 . Larsen SO. Incidence of acute ncml\~::- 89:3691-36?5 (1992). phocytic leukemia. preleukemia, and acute mveloprolifer;l::',. 26. Irons RD, Stillman WS. Cell proliferation and differentiation syndrome up to 10 years afrer treatment ot Hodgkin's di\cl.- in chemical leukemogenesis. Stern Cells 11935-242 (1993). N Engl J Med 307:965-971 (1982). 1244 Environmental Health Perspectives VoI 104. Supplement 6 = Decernbe: I996 SECONDARY LEUKEMOGENESIS d" anr NJ. huBlur lged RE, ncer 2nd 'M. icon Lcion -199 iron r the bled mic mal .with oge:the ncer &, h berg ;f for Rev 3 Jr. 3oice rhan wing -683 ,sup,supbled rome UPPl rk A, and lOStlC rapy. ed). 3peu- fer P, non- dyr rat1 sese. I Pedersen-Bjer aard J. Radiotherapy- and chemotherapyinduced myelo&plasia and acute myeloid leukemia. A review. Leuk Res 16:61-65 (1992). Pedersen-Bjergaard J, Nissen NI, Sorensen HIM, Hou-Jensen K, Larsen MS, Ernst P. Ersbol J. Knudrzon S, Rose C. Acute non-lymphocyric leukemia in pacienrs wich ovarian carcinoma following long-term treatment wirh rreosulfan (=dihydron- busulfan). Cancer 45: 19-29 (1980). Rosner F, Grunwald HW. Hodgkin's disease and acute leukemia: report of eighr cases and review of the literacure. .im J hied 58:339-3 53 (1975). Rosner F. Grunwald HW. Mulriple myeloma terminating in acure leukemia. iim J bled 57:927-939 (1974). Kaldor JM, Day NE, Petcersson F, Clarke EA, Pedersen D. Mehnerr W, Bell J, Host H. Prior P, Karjalainen S, Ned F, Koch M,Band P. Choi W, Kirn VP, Arslan A, Zaren 8, Belch AR, Storm H , Kicrelmann B, Fraser P, Srovall ,M. Leukemia Following chemorherapy For ovarian cancer. N Engl J &led 323~1-6(1990). Smic CGS, Meyler L. Acure myeloid leukaemia after treacmenr with qrosratic agents. Lancet Seprember 26:671-673 (1970). Trump DL. Cowall DE. Acure myelogenous leukemia as a late complication of rhe mulrimoddiry rherapy for Hodgkin's disease. Johns Hopkins bled J 141249-251 (1977). Tucker MA, Coleman CN. Cox RS, Varghese A, Rosenberg SA. Risk of second cancers after rreacmenr for Hodgkin's dism e . N Engl J bled 318(2):76-81 (1988). Mirelman F, Nilsson PG, Brandt L.Alimena G. Gastaldi R. Dallapiccola B. Chromosome panern. occu arion and clinical fearures in patients wich acute non1ympPhocyt:c leukemia. Cancer Genet Cyrogenet 4197-214 (1981). hlicelman F, Brandr L, Nilsson PG. Relarion among occupa- tional exposure co orential muragenic/carcinogenic agents, clinical findings. a n 1bone marrow chromosomes in acme non- lynphocycic leukemia. Blood 52:1239-1237 (1978). Golomb HM, Alimena G, Rowley JD, Vardiman JW, Testa JR, Sovik C. Correlacion ofoccuparion and karyotype in adulrs with acure nonlymphocyric leukemia. Blood 60:4044 11 (1982). Fagioli F, Cuneo .i,Piva N.Cadi MG. Previaci R, Balboni hi. Tomasi P, Cariani D, Scapoli G, Casroldi G. Distinct q-cogeneric and clinicopathologic fearures in acuce myeloid leukemia h e r occuparional exposure ro pesticides and or"ganic solvents. Cancer 70377-85 (1992). Crane M M . Keaino MI. Truiillo TIM. Labarrhe DR. 2626346639 (1989). ,. , Narod SA, Dube ID. Occuparional history and involvement of chromosomes j and 7 in Bcuce nonlymphocyric leukemia. Cancer Gener Cyrogener 38261-269 (1989). Michels SD. .McKenna RW, Arthur DC, Brunning RD. Therapy-relaced acme myeloid leukemia and myelodysplasric svndrome: a clinical and morpholoeic scudv of 65 cases. Blood . I 636): 1364-1372 (1985). Cuneo A, Facioli F, Pazzi I. Tallarico A. Previati R, Piva X. Cadi GM. BJboni bt. Casroldi G. Morphologic. immunologic and cytogenetic srudies in acuce myeloid leukemia follo\ving occupational exposure ro pesricides and organic solvenrs. Leuk Res 16:789-796 (1992). Xliller JS, Arthur DC, Lin CE. Neglia JP,Miller WJ, Weisdort` DJ. Myelodysplastic syndrome after aurologous bone marrow rransplancation: an addirional late complicarion ot curzti\-e cancer rherapy . Blood 833750-3786 (1994). .iksov M. Benzene Carcinoe"enicitv. Boca Raton. FL:CRC Press, 1988. L'ieliani EC. Forni A. Benzene and leukemia. Environ Res I 11:111-127 (1976). Forni A. Viglidni EC. Chemical leukemogenesis in man. Szmin Hematol 7(2):?11-223 (1974). DccouHe P. Blarrner WA, Blair A. Morralirr among chemical workers e r p o w i co benzene and other ~ g e n r s .Environ Res 30:16-25 (1383). Abstract. 71. Rowley JD. Golomb HM, Vardiman J. Nonrandom chromo- somai abnormaliries in acute nonlymphocytic leukemia in patients created for Hodgkins disease and non-Hodgkins lym- phomas. Blood 50:759-770 (1977). 72. Rowley JD. Golomb HM, Vandiman JW. Nonrandom chro- mosome abnormalities in icure leukemia and dysmyelopoieric syndromes in patients with previously treated malignant dis- case. Blood j8:?59-767 (1981). 73. Le Beau ,MM. Albain KS. Larson RA. Vardiman JW, Davis EM, Blough RR. Golomb HIM, Rowley JD. Clinical and cyogeneric correlacions in 63 pariencs with rherapy-relaced myelodysplasric syndromes and acute nonlymphocyric leukemia: turther evidence for characterisric abnormaliries of chromosomes no. 5 and 7. J Clin Oncol4(3):325-345 (1986). 74. Pedersen-Bjerpaard J, Philip P. Perdersen NT, Hou-Jensen K. Svejgaard A, Jensen G. Nissen NI. hcuce nonlymphocytic leukemia, preleukemia, and acute myeloproliferarive syndrome secondary to rreatment of other malignant diseases. Cancer 54452-462 (1984). 75. Johansson B, ,Mertens F, Heim S, Kristoffersson U, Mirelman F. Cytogenerics of secondary myelodysplasia (slCiDS) and acure nonlymphocytic leukemia (AVLL). Eur J Haemarol 47:17-17 (1991). . 76. Bitter MA, Le Beau Mbi, Rowley JD, Larson Ri, Golomb H,M, Vardiman JW. Associarions benveen morphology. kary- otvpe. and clinical fearures in myeloid leukemias. Hum Parhol 18211-215 (198;). 77. Fourth International Workshop on Chromosomes in Leukemia 1983. The correlation of karyotype and occuparional exposure to porential mutagenicicarcinogenic agenrs in acute nonlynphocyric leukemia. Cancer Cener Cytogener 11:3?6-33 1 (1984). 78. Bloomfield CD. Goldman A. Hossfeld D. de la Chapelle A. Clinical significance of chromosomal abnormalities in acure non1vmohobIascic leukemia. Cancer Genet Cv. toe-enet 11:332-550 (1984). 79. Pedersen-Bjergaard J, Philip P, Morrensen BT. Ersboll J. Tensen G. Panduro I1.. Thomsen M.Acute nonlvmuhocvric leukemia. 'preleukemia, and acure mye1oproliferaci;e ;yndrome secondary ro rrearmenr of ocher malignant diseases. Clinical and Togeneric characrerisrics and results of in cino culture of bone marrow and H L i typing. Blood 57(4):712-723 (1981). 80. Smith MT, Zhang L, Rorhman N, Wang Y. Hayes RB. Li GL. Yin SN. Interphase cytogenetics of workers exposed to benzene. Toxicologisr 15:87 (1995).Absrracc. 81. Van den Berghe H. Louwagie A, Broeckaerr-Van Orshoven A, David G, Verwilghen R. Chromosome analysis in rwo unusual malignanc blood disorders presumably induced by benzene. Blood 53558-566 (1979). 82. Zhang L, Rothman N, Wang Y, Haves RB. Yin S-N, Holland N,Dosemeci M.Wang Y-Z, Kolachana P, Xi L-Q, Li G-L. Smirh MT. Aneuploidy of chromosomes 7 , 8 and 9 detected by fluorescence in f z h d hybridization in workers exposed ro benzene. Proc Natl Acad Sci USA 92:40694073 (1995). (Absrracr). 83. Le Beau MiM, Rowlev JD. Chromosomal dbnormalicics in leukemia and lymphoma: clinical and biological significance. Adv Hum Csner 15:1-54 (1986). 84. Stone R, Neubrrg D, SoitFer R. Wfielan M,Leavirt P, h e r J, Takvorian R. Rabinowe S, Ricz J , Frerdmzn A, Nudler L. Myelodyspluscicsyndrome (MDS) as a complication aher iurologous bone marrow transplancarion (ABMT) for non Hodgkin's lymphoma (NHL). Blood Y2:196a (1913). Abscracr. 85. Chen HLV,Francz C, Eastmond DA. Inhibition o f ropoiso- mcrase enzymes by phenolic metabolices: i porential mechanism for benzrne's clasrogenic effects. In: Benzene `95: International Conference on the Toxicity. Carcinogenesis. and Epidemiology o f Benzene, 17-20 July 1995. Pisiarawav. NJ. Abstracr. 86. Luna-Fincman S, Shannon LM,Lange BJ. Chilclhoocl mono- somy 7: epidemiology, biology, and mechanistic implicarions. Blood 85: 1985-1999 (1995). 87. v:in clcn Berghe H , Vermaelen K, btccucci C. Barbicri [I. Environmental Health Perspectives Vol 104, Supplement 6 December 1996 1245 IRONS AND STILLMAN 1 Tricot G. T h e 54- anomaly. Cancer Gcner Cy. rog-enet 17:I 89-225 (1985): 88. Rowlw ID, Le Beau MM. Cvrownetic and molecular analvsis of theiapy-related leukemia. 'Ani NY Acad Sci 567:130-i40 (1989). 89. Murphree AL, Benedicr WF. Retinoblastoma: clues ro human oncogenesis. Science 223: 1028-1033 (1984). 90. Nimer S D , Golde D W . T h e 5q- abnormaliry. Blood 70:1705-1712 (1987). 91. Ridge SA, Wonvood M, Oscier D, Jacobs A, Padua RA. FMS mutations in mvelodysplasric, leukemic. and normal subjecrs. Proc Narl Acad Sci USA 87:1377-1380 (1990). 92. Radich JP, Kopecky KJ, Appelbaum F. Willman CL, Collins SJ. N-ras mutations in acute myelogenous leukemia: a review of the currenr literature and an update of rhe Southwesr O n c o l o p Group experience. Leuk Lymphoma 6:325-334 (1992). 93. Liu ET. The role of ras gene mutarions in rnyeloproliferarive disorders. Clin Lab Med 10:797-807 (1990). 94. b r a n MB, Srrauss LC, Civin CI. The role of hematopoieric growth facrors and oncogenes in leukemogenesis. hJ Pediatr Hemarol Oncol 11:249-267 (1389). 95. Needleman SW. Ras prorooncogene activarion in acute myeloid leukemia and relared disorders. Leuk Lymphomz 5~85-91 (1991). 96. Taylor JA, Sandlcr DP, Bloomfield CD, Shore DL, Ball ED, Neubauer A, McIntyre OR, Liu E. Rac oncogene activation and occupational exposures in acure myeloid leukemia. J Narl Cancer Insc 84:1626-1632 (1992). 97. Kubo K,Naoe T , Kiyoi H, Fukurani H , Karo Y. Oguri T. Yamamori S, Akarsuka Y, Kodera Y, Ohno R. Clonal analysis of mulriple point murarions in rhe N-rasgene in patients with acure myeloid leukemia. Jpn J Cancer Res 84:379-387 (1993). 98. Hirai H, Okada M, Mizoguchi H , Mano H, Kobayashi Y, Nishida J, Takaku F. Relarionship beween an acrivared W-ras oncogene and chromosomal abnormality during leukemic progression from rnyelodysplasric syndrome. Blood 71:156-258 (1988). 99. Toksoz D, Farr CJ, Marshall CJ. Ras gene activarion in a minor proponion of rhe blast popularion in acute myeloid leukemia. Oncogene 13409413 (1987). 100. Farr CJ, Saiki RK, Erlich HA, McCorrnick F, Marshall CJ. Analysis of R/IS gene mutarions in acure myeloid leukemia by polymerase chain reacrion and oligonucleoride probes. Proc Nad Acad Sci USA 85:1629-1633 (1988). 101. Chen C-Y, Oliner JD, Zhan Q, Fornace .4J Jr, Vogelstrin B, b r a n MB. Inreracrions berween p53 and MDM? in a mammalian cell cvcle checkpoint parhwav. Proc Nad Acad Sci USA 9 1 2 6 8 4 2 6 8 8 (1994): 102. Hollsrein M, Sidransky D , Vogelstein.B, Harris CC. p5 3 Murarions in human cancers. Science 253:49-53 (1991). 103. Soussi T, Jonveaux P. p53 Gene alterarions in human hemaro- logical malignancies: a review. N o u v Rev Fr Hemarol 33y47-480 (T991). 104. Knudson AG. Heredirary cancers disclose a class of cancer genes. Cancer 6331888-1831 (1983). 105. beinberg Rh. The rerinoblastorna prorein and cell cycle con- trol. Cell 81:323-330 (1995). 106. Kornblau S, Xu H-J, del Giglio A, Hu S-X.Zhang W. Calvert L. Beran M,Esrey E, Andreeff M. Trujillo J, Cork MA. Smith TL. Renedicr WF, Deisserorh AB. Clinical implications of decreased rerinoblascoma prorein expression in acure rnveloge- nous leukemia. Cancer Res 51:4587-4590 (1992). 107. Furukawa Y, DeCaprio IA4,Belvin M. Griffin J D . Hererogeneous expression of rhe producr of the rerinoblasroma susceptibiliry gene in primary human leukemia cells. Oncogc! 6: 1343-1346 (1991). 108. Bagby GC, Wilkinson B, ,McCall E, Lee IM.Abnormalities (1:' the hemaropoietic regulatory network. Adv Exp Med Bio. 24 1 255-264 (1988). 109. Foon KA, Champlin RE. Gale RP. Acute myelogenot!< leukemia and rhe myelodysplasric syndromes. In: Cancc. Treatmenr (Haskcll C.M. ed). Philadelphia:\X'.B. Saunder. 1990; 589-606. 110. Holden JT, Geller RB, Farhi DC, Holland HK. Stempora 1 Phillips CN, Bray RA. Characterization of Thy-1 (CDw9, expression in CD34- acutc leukemia. Blood 86:60-65 (1995 1 11. Sawada I<, Saro N,Notoya A, Tarumi T, Hirayama S, Takan,, H , Koizumi K, Yasukouchi T , Yamaguchi iM,Koike 7.. Proliferation and differenriarion of myelodysplastic CD3-cells: phenorvpic subpopulations of marrow CD34' cells. Blood'85:19&202 !l9%f. 112. Kroef MJPL, Fibbe WE. Mour R, Jansen RPM, Haak H! Messels IW, Van Kamo H. Willemze R, Landegenr 1' Myeloid bur nor lymphdid cells carry rhe 5q delerign: p i : merase chain reacrion analysis of loss of hererozygosin usi' mini-repear sequences on highly purified cell fracrions. Blo, 81: 1849-1854 (1993). 113. Young DC, Wagner K,Griffin JD. Constitutive cxpression ot` the granulocyre-macrophage colony-srimularing factor gene in acute myeloblasric leukemia. J Clin Invesr 79:100-106 ( 19s- , 114. Zwierzina H , Scholienberger S. Herold M, Schrnalz! F. .-Besemer J. Endogenous serum levels and surface recepro: expression of GM-CSF and IL-3 in patients wirh rnyeloai plasric syndromes. Leuk Res 1 6 1181-1186 (1993). 115. Courinho LH, G e a y CG, Chang J, Harrison C, Test2 \! Functional studies of bone marrow haernopoieric and srror: cells in rhe rnyelodysplastic syndrome (MDS). Br J Hae-i. 51G-25 (19901. 116. Greenberg BR, Wilson FD, Woo L. Granulopoieric effects .r< human bone marrow fibroblastic cells and abnormaliries in rnc "granulopoieric microenvironmcnr." Blood 58:557-5& (1981). 117. Sachs L, Lorern J. Conuol of programmed cell death in normi and leukemic cells: new implicarions for therapy. Sioct 82:15-21 (1993). 118. Raza A, iMundle S. Ikikhar A, Gregory S, Marcus B, K h ~ n-' Alvi S, Sherry V, Dameron S, Wrighr V, Adler S, Loew .' Shorr S, Ali Sh', Preisler H. Simulraneous assessment o i L.. kinetics and programmed cell dearh in bone marrow biopsie: ;/ myelodysplasrics reveals exrensive apoprosis as rhe proba:: basis for ineffective hematopoiesis. h J Hematol 48:14%! ;: (1995). 119. Raza A, G a e r S, Mundle S, Gao X-Z, Avi S, Borok R. Rifkc S, Iftikhar A, Sherry i:,Parcharidou A, Loew J, Marcus 3. Khan Z, Chaney C. Showel J, Gregory S, Preisler H. Apopro.!? in bone marrow biopsv samples involving stromal 2 - 2 hematopoieric cells in 50 patienrs wirh myelodysplastic <. - dromes. Blood 86:268-276 (1995). 120. Pech N, Hermine 0. Goldwasser E. Further study of inrz... .-I autocrine regularion of rnultiporenr hemaropoieric cells. Bi. 1:, 82: 1502-1556 (1993). 121. Pedersen-Biergaard J. Philip P,Larsen SO, Jensen G. Bvrtr.:?; K. Chromosome aberrations and orognostic facrors in the::.r. . IV related myelodvsplasia and acure nonlvmphocyric leuken::.: Blood 76:1083-1091 (1990). .,122. Wald N,Conner 11K.Induced chromosome darnagc J:*:: irradiarion and cyrorosic drugs. Hernarology 8: 1 iq--. (1988). I246 -Environmental Health Perspectlves Vol 104, Supplement 6 December I996