Impact of Tumor Infiltrating T Cells in Patients with Diffuse Large B-Cell Lymphoma

Abstract 1572

Previous studies have demonstrated the importance of the non-malignant tumor-infiltrating immune cells in the tumor microenvironment at diagnosis in patients with non-Hodgkin's lymphoma (NHL). We aimed to investigate the molecular mechanisms whereby tumor infiltrating T cells (TILs) are altered in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). We used gene expression profiling of highly purified CD4 and CD8 infiltrating T-cells (TILs) from FL patients and reported that PMCH, ETV1 and NAMPT are highly expressed in both CD4 and CD8 TILs and showed in tissue microarrays (TMA) that expression of pro-melanin-concentrating hormone (PMCH), ets variant 1 (ETV1) and nicotinamide phosphoribosyltransferase (NAMPT) in T-cells have prognostic impact in disease specific survivals (DSS) and time to transformation (TT) in patients with FL. In addition, PMCH and NAMPT were shown to be independently significant in TT in multivariate analysis.

We next examined expression of these gene products in T cells in FL samples before and after transformation to DLBCL (n=29). Comparing total number of positive cells for expression of proteins of interest, we demonstrate there is a significant decline in PMCH (p=0.035), EVT1 (p=0.018) and NAMPT (p=0.0136) expressing cells after transformation. We further investigated the prognostic impact of expression of these proteins in T cells in patients with DLBCL in two treatment groups, those receiving rituximab (n=68) and in a historic non-rituximab (n=130) treated cohort. By assessing the number of positive cells and the impact on survival using Kaplan-Meier analysis, we now show that the T-cell expressed genes PMCH, ETV1 and NAMPT have prognostic significance for overall survival (OS) in patients with DLBCL. Patients with higher number of PMCH expressing T-cells showed significant longer survivals in both rituximab (p=0.027) and non-rituximab (p=0.033) treated groups. In contrast to PMCH, and in line with our previous data in FL, patients with higher number of NAMPT expressing cells showed significantly shorter OS in the rituximab (p=0.046) treated group, with a trend towards shorter OS in non-rituximab (p=0.064) treated group. Patients with higher percentage of ETV1 expressing cells had longer OS in the non-Rituximab group (p=0.008), with only a trend towards OS with rituximab treatment (p=0.067). We are examining this further in a larger cohort of rituximab treated patients.

Our previous data has indicated that TILs in patients with FL are abnormal in terms of their gene expression and function. We now show that changes in protein expression in TILs have an impact on transformation in patients with FL and on survival in both FL and DLBCL. We are further characterizing the mechanisms of gene expression alteration in TILs of patients with FL and DLBCL and its functional consequences in the biology and of the disease. It appears that altered gene expression in TILs plays a fundamental role in transformation and may be important in the survivals and biology of NHL. Since non-malignant infiltrating immune cells have a crucial role in the outcome of patients with FL and DLBCL, understanding the nature and impact of the abnormalities induced in TILs in these patients is crucial before any immunotherapeutic strategies can be implemented to attempt to alter the immune microenvironment in NHL.