Human Immunodeficiency Virus (HIV) Status Drives Diffuse Large B Cell Lymphoma through Oncogenic Signaling Pathways

Introduction:

Diffuse Large B cell Lymphoma (DLBCL) is up to 80-fold more likely to occur and follows a more aggressive clinical course in HIV positive (+) individuals compared to HIV negative (-) individuals. Moreover, the vast majority frequently present at advanced stages with high tumor burdens with poor prognosis. The molecular pathology underpinning the clinical features of DLBCL in HIV(+) patients relative to the general population is poorly understood; however, it is suspected to depend on decreased host immune surveillance and alternative mechanisms of tumorogenesis. In this study, we sought to identify the differences in gene expression between HIV(+) and HIV(-) DLBCL cohorts that may contribute to the unique features of HIV(+) DLBCL.

Methods:

We performed a retrospective gene expression profiling (GEP) study using a total of 70 DLBCL cases, 31 HIV(+) obtained from AIDS Cancer Specimen Resource Network (https://acsr.ucsf.edu/) and 39 HIV(-) institutional cases. The H&Es for all cases were reviewed by a hematopathologist and tumor content determined. Cases that did not meet the minimum tumor content threshold of 70% were macro-dissected. RNA was extracted from 4x 5µm formalin fixed, paraffin embedded (FFPE) sections using the Qiagen AllPrep DNA/RNA FFPE Kit and quantified using a NanoDrop. The Lymph2Cx assay, which accurately subtypes DLBCL in FFPE tissues (Scott et al 2014), was used to determine the cell of origin (COO) subtypes: Germinal Center B cell (GCB), Activated B cell (ABC) and Unclassifiable (UNC). Digital GEP was performed using the NanoString PanCancer Pathways and Immunology panels, targeting a total of over 1300 genes with known roles in cancer or immune signaling.

Results:

Of the 31 HIV(+) cases, Lymph2Cx subtyping showed 74% (23/31) were GCB, 13% (4/31) were ABC and 13% (4/31) were UNC. In a similar distribution to the HIV(+), and comparable to prior literature, 54% (21/39) of HIV(-) cases were GCB, 31% (12/39) were ABC and 15% (6/39) were UNC. Differential gene expression was observed between HIV(+) and HIV(-) cases, but no association with COO subtype was found. When the data was re-analyzed within the GCB subtype alone, stratification by HIV status was observed. Particularly, reduced expression of genes associated with immune regulation was observed in HIV(+) GCB cases compared to HIV(-) GCB cases. In contrast, expression of genes associated with cell cycle regulation and homologous recombination (the predominate double stranded DNA repair pathway employed during the cell cycle), were higher in HIV(+) cases compared to HIV(-) GCB cases.

Conclusions:

The results show, that within the GCB subtype, marked differences in gene expression are associated with HIV status. Our results suggest that the aggressive nature of DLBCL in HIV(+) patients may, in part, be mediated by enhanced cell proliferation potentiated by aberrant DNA repair.