High Resolution Array-CGH in Splenic Marginal Zone B-Cell Lymphoma: Correlation of Copy Number Imbalances with HCV Status and Prognostic Categories.

In splenic marginal zone B-cell lymphoma (SMZL) no specific genetic alterations are known. Abnormalities of chromosome 7p and of p53 are reported as adverse prognostic factors. In a recent multicentre study (Arcaini et al Blood 2006), a prognostic model based on hemoglobin, albumin and LDH identified 3 risk categories. HCV infection was present in nearly 20% of patients (pts). At now, no data are available on genetic alterations in the HCV-positive subset of SMZL and in the different prognostic categories. The aims of the study were: a) to analyze copy number alterations (CNAs) by means of array comparative genomic hybridization (array-CGH) with a resolution of ∼100 kb; b) to compare CNAs in HCV-positive and HCV-negative pts; c) to identify potential genetic alterations related to the clinical features and to the prognostic categories. We analyzed marrow and blood samples from 34 pts with SMZL: 22 were HCV-negative (serology and HCV-RNA) and 12 were HCV-positive (genotype 2a/2c in 10 pts, genotype 1 in 2). DNA was extracted from bone marrow (16) and peripheral blood lymphocytes (18) and was hybridized with pooled blood lymphocyte reference DNA on Agilent’s 44K oligonucleotide microarray (kit 44B). Images and data were analyzed using Agilent’s Feature Extraction (v9.1) and CGH analytics (v3.4.27) softwares. Ten cases (4 HCV+ and 6 HCV-) did not show CNAs. A single alteration was present in 7 pts, 2 to 5 alterations in 11 and >5 in 6. All CNAs were detected in mosaicism (from 20% to 90%). A median of 5.6 (range 1 to 20) and 3.8 (range 1 to 13) CNAs were detected in HCV+ and in HCV- cases, respectively. The most frequent CNAs were hetereogeneous in size with the following common regions: losses of 1p36.21-p35.3 (3 pts), 7q31.1-q32.3 (7 pts), 8p21.3-p12 (6 pts), 13q14.2-q14.3 (6 pts), 14q32.12-q32.13 (4 pts) and 17pter-p12 (8 pts); gains of 3q21.1-q29 (5 pts), 12q13.1-q21.31 (5 pts), 17q24.1-qter (4 pts), Xpter-p11.23 (4pts). A homozygous 13q14.2 deletion, overlapping that found in CLL and including Rb1 gene, was found in one HCV- pt. The del(7)(q31.1-q32.3) was the more frequent and it ranges from 14,1Mb to 34Mb. No difference in number of CNAs and in specific common regions alterations was found between HCV+ and HCV- cases except for dup(X)(pter-p11.23) (p=0.01, 4 HCV+ pts and none HCV- pt). High-risk prognostic category was significantly associated with del(7)(q31.1-q32.3) (p=0.01) and del(17)(pter-p12) (p=0.02). Mutational status of immunoglobulin variable heavy-chain gene was related to del(7)(q31.1-q32.3) (p=0.04) and dup(12)(q13.1-q21.31) (p=0.03). The presence of villous lymphocytes was associated with del(1)(p36.21-p35.3) (p=0.02); del(8)(p21.3–p12) was related to an autoimmune background in the HCV+ subset (p=0.04). The number of CNAs was associated to leukemic disease (p=0.02) and to the presence of villous lymphocytes (p=0.04). In conclusion, array-CGH in SMZL does not show specific genetic abnormalities for pts with HCV-positive or HCV-negative SMZL. 7q and 17p deletions are significantly associated with the high-risk prognostic category, clinically and biologically identifying a group of pts with aggressive disease.