Enhanced DNA repair and genomic stability identify a novel HIV-related diffuse large B-cell lymphoma signature

Abstract

Diffuse large B-cell lymphoma (DLBCL) is up to 17-fold more likely to occur, follows a more aggressive clinical course and frequently presents at advanced stages in HIV infected (+) individuals compared to HIV negative (−) individuals. However, the molecular pathology underpinning the clinical features of DLBCL in HIV(+) patients relative to the general population is poorly understood. We performed a retrospective study examining the transcriptional, genomic and protein expression differences between HIV(+) and HIV(−) germinal center B-cell (GCB) DLBCL cases using digital gene expression analysis, array comparative genomic hybridization (CGH) and immunohistochemistry (IHC). Genes associated with cell cycle progression (CCNA2, CCNB1, CDC25A, E2F1), DNA replication (MCM2, MCM4, MCM7) and DNA damage repair, including eight Fanconi anemia genes (FANCA, FANCD1/BRCA2, FANCE, FANCG, FANCR/RAD51, FANCS/BRCA1, FANCT/UBE2T, FANCV/MAD2L2), were significantly increased in HIV(+) GCB-DLBCL tumors compared to HIV(−) tumors. In contrast, genes associated with cell cycle inhibition (CDKN1A, CDKN1B) as well as apoptosis regulating BCL2 family members (BCL2, BAX, BIM, BMF, PUMA) were significantly decreased in the HIV(+) cohort. BCL2 IHC confirmed this expression. Array CGH data revealed that HIV(+) GCB-DLBCL tumors have fewer copy number variations than their HIV(−) counterparts, indicating enhanced genomic stability. Together, the results show that HIV(+) GCB-DLBCL is a distinct molecular malignancy from HIV(−) GCB-DLBCL; with an increased proliferative capacity, confirmed by Ki67 IHC staining, and enhanced genomic stability, the latter of which is likely related to the enhanced expression of DNA repair genes.