CONTRIBUTION OF ARRAY COMPARATIVE GENOMIC HYBRIDIZATION TO PROGNOSTIC STRATIFICATION IN DIFFUSE LARGE B-CELL LYMPHOMA

Sborník

Background. Diffuse large B-cell lymphoma (DLBCL), a heterogeneous clinicopathologic entity, accounts for up to 40% of non-Hodgkin’s lymphomas. Gene expression profiling confirmed the presence of three molecular prognostic subgroups - germinal center B-cell-like (GCB), activated B-cell-like (ABC) and primary mediastinal B-cell lymphoma (PMBL). Nevertheless, there is a need to identify genes with a critical function in DLBCL to stratify patients into prognostic subgroups without expression profiling. Aims. To study copy number alterations (CNAs) in DLBCL patients and to correlate them with cytogenetic and other molecular cytogenetic results to define the optimal approach for prognostic stratification. Methods. A single-center study comprising 51 DLBCL patients (24 males; median age at diagnosis 49 years). Thirty-two patients were histopathologically diagnosed as DLBCL, 18 patients as PMBL and one patient as gray zone lymphoma. ArrayCGH with BAC microarrays was used in 26 patients (Bluegnome, Cambridge, UK; K3 Leiden, Netherlands) and oligonucleotide microarrays 4x44K (Bluegnome and Agilent, Santa Clara, USA) were applied in 25 patients. Fifty patients were examined by conventional cytogenetics; FISH with different probes was applied in all patients. Results. Stratification criteria published by Staudt and Dave (2005) were used. Array- CGH revealed CNAs in 28 (55%) patients. The most frequent losses were detected on chromosomes 1q, 4q, 6q, 13 and 17p; the most frequent gains on chromosomes 7, 8q, 9p and 12. Based on the results, all 28 patients were stratified into molecular subgroups. Using conventional cytogenetics, chromosomal changes were detected in 26 (51%) patients. The most frequent balanced chromosomal change was t(14;18) confirmed in 6 patients. BCL2 duplication was confirmed in 5 patients. FISH analysis of 45 patients with locus-specific probes LSI IGH/MYC,CEP8 and/or LSI MYC DC (Abbott Molecular, Illinois, USA) revealed low frequency of translocations (1 patient) in the cohort but frequent presence of CMYC gene duplication (11/45 patients). The overall survival of patients with CMYC aberrations was shorter compared with those without them but a larger cohort is needed. The gain of the JAK2 gene was studied in 25 patients with locus-specific probes ON JAK2 (9p24) Break (Kreatech, Amsterdam, Netherlands). Duplication and amplification were confirmed in 5 and 7 PMBL patients, respectively. Conventional cytogenetics, FISH and arrayCGH enabled detection of 28 (55%) patients with a complex karyotype. With all results obtained from cytogenetic and molecular cytogenetic methods, a total of 45 (88%) patients could be stratified. There were 11, 14 and 20 patients in the ABC, GCB and PMBL subgroups, respectively. Conclusions. Prognostic stratification based on arrayCGH was performed in 55% of patients. With a combination of all cytogenetic and molecular cytogenetic methods, a total of 45 (88%) patients were stratified. The results confirmed the benefit of arrayCGH for detecting CNAs in DLBCL for prognostic stratification but also to the necessity to supplement the result by FISH and cytogenetics to detect balanced changes of prognostic and stratification importance. The detection of all as well as cryptic copy number changes could possibly reveal differences in the oncogenic mechanisms in DLBCL.

Supported by MZČR IGA NT 11103.

Haematologica, 2012; 97(s1):  644