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Plasma Cell Karyotype in Multiple Myeloma By James Gould, Raymond Alexanian, Angela Goodacre, Sen Pathak, Barbara HeCht, and Bart Barlogie Karyotypic abnormalities were studied in multiple myeloma and were correlated with clinical features. Among 115 evaluable patients. 46% had an abnormal karyotype. Tn- somy 3. 5. 9. and 1 5 and monosomy 1 3 and 1 6 were the most common clonal abnormalities. Translocations de- scnibed previously in other B cell malignancies occurred in nine patients. including four with t(8;14)(q24;q32) translo- cations. The association of all t(8;14) abnormalities with M ULTIPLE MYELOMA is a malignant disorder of plasma cells that secrete monocbonal immunoglobu- bin. Cytogenetic studies in this disease have been largely unsuccessful because of bow tumor proliferative activity.' Most commonly reported abnormalities were structural changes of chromosomes 1 and 14, as well as a variety of monosomies and tnisomies.2' ` Translocations of t(1 1 ; 14) have also been reported,3'9"#{176} as has one patient each with t(8;l4) and t(14;18) translocation.'2"3 This report describes the cytogenetic findings in a large number of patients with plasma cell myeloma and reveals an association of certain chromosomal anomalies with myeloma protein type. METHODS Between February 1985 and December 1986, 153 bone marrow samples from 140 patients with unequivocal plasma cell myeloma were submitted for both cytogenetic and flow cytometnic analysis. Cytogenetic studies were conducted on marrow aspirates collected in RPMI 1640 growth medium with hepanin and colcemid (0.04 zg/mL) without mitogens. Following 20 minutes of hypotonic treatment in 0.06 mob/L KCL, several changes of 3: 1 methanol:gla- cial acetic acid fixative were used to fix and to eliminate RBCs. Air-dried slides were prepared using the cell pellet resuspended in methanol:glaciab acetic acid mixture (1 :1 by volume). Q-, G-, and/or C-bandings were performed according to standard methods.'4 Iden- tical abnormalities in two or more cells defined a cbonal population, except for monosomies or deletions, where three or more cells with identical aberrations were required' In samples showing karyotypic heterogeneity, ties detected. the reported karyotype included all clonal abnonmaliA normal karyotype was confirmed when no cbonal abnormality was detected among 15 metaphases examined. Excluded from the analysis were I 3 patients studied during remis- sion with less than 1% monocbonal plasma cells in the marrow on flow cytometry and a normal karyotype; I 2 patients with less than IS metaphases and no clonal abnormality were also excluded. Flow cytometnic analyses were conducted ofceblubar DNA, RNA, and cytoplasmic immunoglobulin content,'6'7 The DNA index was defined from the ratio of fluorescence intensities of tumor Gl/0 cells to normal peripheral blood lymphocytes." Tumor mass and response to therapy were defined by standard cnitenia.'9'#{176S}tatistical compani- sons were conducted by chi-square tests. RESULTS Of I 1 5 patients with evaluable metaphases, 46% showed an abnormal kanyotype, which was more likely in patients with IgA or relapsing myeloma (Table 1). The frequency of abnormalities was unrelated to age, sex, tumor mass, or the degree of marrow plasmacytosis (Fig 1). Chromosomal abnormalities were usually complex, with multiple structural changes (translocations, derivatives, de- letions) occurring in 90% and numerical deviations in 86% of IgA protein type suggested a pathogenetic relationship between a specific karyotypic abnormality and myeloma protein type. Hypodiploidy occurred mainly in patients with only Bence Jones protein. was associated with resistance to therapy. and justified the early consideration of investi- gational therapies. S 1988 by Grune & Stratton, Inc. Table 1 . Patient Characteristics Disease status at cytogenetic At diagnosis Unresponsive Relapsing Remission Protein type IgG IgA Light chain only Nonsecretory DNA ploidy Hypodiploid Diploid Hyperdiploid study No. Patients 115 31 44 30 10 60 30 22 3 5 25 85 % Abnormal Karyotype 46 36 45 60 (P = .12) 40 42 63(P41 0 .05) 40 40 48 patients. tnisomies Hyperdiploid and tetnasomies samples commonly of chromosomes showed multiple ,3, 5, 7, 9, 1 1 15, 1 8, 1 9, and 2 1 ; monosomies typically involved chromosomes 8, 13, 16, 20, or 22 (Fig 2). Structural changes of chromo- some 1 were found in 49% of patients but without a consis- tent breakpoint or a common region of deletion (Fig 3). In contrast, 1 3 of I 8 patients with structural anomalies of chromosome 14 had a breakpoint at q32; the remaining five patients showed breakpoints at sites between q22 and q3 1 (Fig 3). One individual with a prior history of large cell lymphoma showed both t(8;l4)(q24,q32) and t(1 l;14)(q13;q32) in the same metaphases. On flow cytometny studies, 78% of the patients had hyperdipboidy (Table 1). There was a linear, statistical From the University ofTexas, M.D. Anderson Hospital & Tumor Institute at Houston; and the Genetics Center of the Southwest Biomedical Research Institute, Scottsdale, AZ. Submitted June 29, 1987; accepted October 8, 1987. Supported by Grants No. CA 37161 and CA 28771 from the National Cancer Institute and by a grant from the Cullen Trust Foundation. Address reprint requests to Bart Barlogie. MD. Professor of Medicine, U. T. M.D. Anderson Hospital & Tumor Institute, Department ofHematology (Box 55). 1515 Holcombe Blvd. Hous- ton. TX 77030. The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. 1734 solely to indicate this fact. 1 988 by Grune & Stratton. Inc. 0006-4971/88/7102-0026$3.00/0 Blood, Vol 71, No 2 (February), 1988: pp 453-456 453 454 GOULD ET AL 00 80 Inii11m C e-io "-20 21-30 31-40 41-50 `50 S MARROW PLASMACYTOSIS Fig 1 . Similar frequency of abnormal karyotype with ing marrow plasmacytosis defined either morphologically abnormal DNA/RNA content. 0 Marrow differential; Cytometry. increasor by B Flow correlation between DNA-derived ploidy (DNA index) and modal chromosome number expressed as a karyotype index (modal chromosome number divided by 46; Fig 4). Among 53 patients with evaluable karyotypes, chromosomal hypo- dipboidy occurred in 1 1%, but low DNA content was observed in only 4% (P = .01). Two patients showed concon- dant DNA indices and karyotypes in the tetraploid range with some chromosome rearrangements present in both copies. One patient showed a near haploid chromosome number. Of four patients with t(8;14)(q24;q32), all produced IgA myeloma protein (Table 2, Fig 5). Other translocations associated with B cell malignancy were also found, including four patients with t(1 l;14)(q13;q32). A hypodiploid karyo- type or a t(l 1 ;14) translocation was present in eight of nine patients with only light chain production. Only three of 13 hypodiploid patients (23%) responded to chemotherapy either prior or subsequent to study, in comparison with responses in 29 of 40 other patients with abnormal cytogenet- ics(73%,P= .01). No apparent relationship was noted between specific chromosomal abnormalities and disease manifestations, such as bone disease or tumor mass. In contrast to the report by Dune et al,2' only four patients showed a deletion of the long arm of chromosome 6, and all showed bone destruction. Monosomy 1 3 occurred in 19 of 43 patients who had received prior chemotherapy but not in any of ten previously untreated patients (P = .02). No difference was evident in chromosome number between untreated patients and those who had prior chemotherapy. U) C `S a`S- 0 U) U) 0 -C ij!.. 2U --- U -`-I 1U U 2 II -1i!:f' I 8 11 14 Fig 3. Composite ideogram showing distribution of clonal breakpoints on the chromosomes affected mostly with structural aberrations. Each symbol represents one patient with a breakpoint at this locus. DISCUSSION Cytogenetic studies of myeloma have been difficult to perform, probably due to low tumor-proliferative activity. Prior flow cytometnic analyses of myeloma marrow have revealed aneuploidy in about 80% of patients,' suggesting that karyotypic abnormalities should be identified more frequently than the 30% to 50% incidence found in this and other studies.2" This discrepancy suggested that normal marrow cells accounted for the normal kanyotype found in patients with cytometric aneupboidy. These findings high- light the greater sensitivity of flow cytometny in assessing ploidy in tumors with low proliferative activity. Among patients with an abnormal kanyotype, a close relationship was usually observed between DNA content as determined by cytogenetics (modal chromosome number) and flow cytometry (DNA ploidy). This correlation indicates that the identified karyotype was indeed that of the abnormal cell population. Hypodiploidy was found more than twice as frequently by cytogenetics than by flow cytometry. This discrepancy can be attributed to the insensitivity of DNA flow cytometry in detecting deletions of small chromosomes and/or the presence of high DNA complement despite low [2.0 1.6 1.4 .s#{149} SC 0 12 ;s#{149}s#{149} 1.0 s-#.. 0.8 Fig 2. Frequency and distribution patients with abnormal karyotype. only. of numeric abnormalities in B IgA; 0 IgG; U light chain 0.6 0.8 1.0 1.2 1.4 1.6 (KARYOTYPE INDEX Modal No. ----, 2.0 Fig 4. Direct relationship between DNA and karyotype in myeloma patients with abnormal karyotype. index CYTOGENETICS IN MYELOMA Table 2. Myeloma Karyot ype and Ig Phenotype No. IgG IgA Only BJP B cell translocations (8;14)(q24;q32)' (11;14)(q13;q32)' (14;18)(q32,q21) Hypodiploidyfl Other anomalies 4 0 4 OP= .001 4 1 12 1 1 00 13 3 4 6P= .001 34 2 1 1 2 1 `.t4. Two abnormalities gammopathy and one patient were present with only BJP. in two patients with IgA 455 chromosome number.22 These findings stress the complemen- tany power of the two techniques in tumor cell analysis, with cytogenetics assessing dividing cells and flow cytometry describing the entire cell population. This study confirms prior reports of complex numerical and structural kanyotype abnormalities in multiple myeboma, especially gains of chromosomes 3, 5, and 9; loss of chromo- some I 3; and rearrangement of chromosome 1 23 However, no consistent structural rearrangements were identified other than those associated with B cell neoplasms. Transloca- (tions 1 1 ; 1 4) have been described,3'9"0 as have single patients with t(8;14) or t(14;18)(12,13). In addition, important asso- ciations with immunoglobulin phenotype were observed, such as the exclusive association of t(8;14) with IgA myeloma protein and the prevalence of hypodiploidy in patients with only Bence Jones proteinunia. The lower response rate among patients with chromosomal hypodi- ploidy was consistent with the drug resistance described previously in patients with low DNA content.' The presence of hypodiploidy by either technique should help identify patients who might benefit from the early application of innovative therapies, such as high-dose melphalan, which has been effective in many patients resistant to standard treat- ment.24'25 Specific translocations have been linked to oncogene acti- vation in certain human mabignancies.262' Thus the t(8; 1 4)(q24;q32) translocation, typically associated with Burkitt's lymphoma, dysregulates myc gene expression by its juxtaposition to the immunoglobulin heavy chain gene.29 Fig 5. trisomies translocation. 0-banded karyotype and t(8;14)(q24;q32). t(8;14). is marked of a marrow cell showing multiple A typical Burkitt's lymphoma-like by arrows. Enchanced myc RNA expression was present in about one fourth of our patients with advanced myeloma studied by Northern analysis, two of whom showed rearrangement of the myc gene.3#{176B}oth t(8;14) and myc gene anomalies have occurred preferentially with IgA myeloma. Despite seem- ingly identical cytogenetic aberrations and myc involvement in Burkitt's lymphoma and IgA myeloma, molecular differ- ences must be postulated to explain the different clinical features of these B cell malignancies. Thus different sites of the myc gene locus may be affected, depending on whether the translocation occurred at an early phase of B cell commitment (ie, during immunoglobulin V-D-J joining) and leading to endemic Burkitt's lymphoma or at a later phase (ie, during isotype switching) and leading to sporadic Bun- kitt's lymphoma or IgA myeloma.3' REFERENCES .I Barbogie B, Alexanian R, Dixon D, Smith L, Smallwood L, 8. Lewis iP, MacKenzie MR: Non-random chromosomal aberra- Delasalle K: Prognostic implications of tumor cell DNA and RNA content in multiple myeboma. Blood 66:338, 1985 tions associated 1984 with multiple myeloma. Hematol Oncob 2:307, 2. Philip P. Dnivshobm A: G-banding analysis of complex aneu- pboidy in multiple myeboma bone marrow cells. 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