BCL2mRNA or protein abundance is superior to gene rearrangement status in predicting clinical outcomes in patients with diffuse large B‐cell lymphoma

Abstract

Introduction: BCL2 is important in lymphomagenesis and represents a candidate biomarker in DLBCL. However, the optimal approach for ascertaining BCL2 status in biopsy specimens is uncertain. Here, we determined BCL2 rearrangement status by fluorescence in situ hybridization (FISH), mRNA abundance by NanoString, and protein abundance by immunohistochemistry (IHC) or quantitative immunofluorescence (IF) in pretreatment FFPE biopsy specimens to ascertain the most clinically meaningful measures. Methods: We identified 56 cases of de novo DLBCL treated with R-CHOP from which pretreatment FFPE biopsy samples were available. To quantify BCL2 expression by IF, digital images were created by scanning histology sections coimmunostained for BCL2 and CD20, then BCL2 fluorescence signals were quantified objectively in CD20-positive cells. Results: BCL2 rearrangement or, interestingly, increased copy number of BCL2 was associated with greater mRNA and protein abundance according to either IHC or IF (P < .005 for all comparisons). BCL2 mRNA abundance was associated with elevated protein abundance by IHC (P < .0001) and IF (rs = 0.65; P < .0001) (Figure 1). In contrast, MYC gene rearrangement, but not increased copy number, was associated with more MYC mRNA and more protein based on IHC (P < .005 for all comparisons). Elevated BCL2 expression was associated with a reduced complete response rate to R-CHOP (mRNA, P = .002; IHC, P = .03; IF, P = .03) and reduced overall survival (OS; mRNA, P = .045; Figure 1), whereas neither BCL2 rearrangement (P = .48), MYC rearrangement (P = .83), MYC mRNA (P = .08) or protein expression (P = .56), MYC/BCL2 “double-hit” (P = .75), nor “dual expression” status (P = .41) was associated with reduced OS. Keywords: “double-hit” lymphomas; BCL2; diffuse large B-cell lymphoma (DLBCL)