Inter- and intratumoral heterogeneity of BCL2 correlates with IgH expression and prognosis in follicular lymphoma

Abstract

Most follicular lymphomas (FLs) are genetically defined by the t(14;18)(q32;q21) translocation that juxtaposes the BCL2 gene to the immunoglobulin heavy chain (IgH) 3' regulatory regions (IgH-3'RRs). Despite this recurrent translocation, FL cases are heterogeneous in terms of intratumoral clonal diversity for acquired mutations and variations in the tumor microenvironment. Here we describe an additional mechanism that contributes to inter- and intratumoral heterogeneity in FLs. By applying a novel single-molecule RNA fluorescence-based in situ hybridization (FISH) technique to detect mRNA molecules of BCL2 and IgH in single cells, we found marked heterogeneity in the number of BCL2 mRNA transcripts within individual lymphoma cells. Moreover, BCL2 mRNA molecules correlated with IgH mRNA molecules in individual cells both in t(14;18) lymphoma cell lines and in patient samples. Consistently, a strong correlation between BCL2 and IgH protein levels was found in a series of 205 primary FL cases by flow cytometry and immunohistochemistry. Inter- and intratumoral heterogeneity of BCL2 expression determined resistance to drugs commonly used in FL treatment and affected overall survival of FL patients. These data demonstrate that BCL2 and IgH expressions are heterogeneous and coregulated in t(14;18)-translocated cells, and determine the response to therapy in FL patients.

Correlation between glycolytic activity on [18F]‐FDG‐PET and cell density on diffusion‐weighted MRI in lymphoma at staging

“…Findings suggestive of the latter were observed in several types of tumor, such as breast cancer, head and neck squamous cell carcinoma, and primary rectal cancer . In lymphomas, there is an additional, strong heterogeneity in NHL due to the considerable number of histological subtypes, which further increases the tumor tissue heterogeneity between patients, adds to the biological complexity, and may be chiefly responsible for the variability detected in our study, as well as in previous studies …”

“…Findings suggestive of the latter were observed in several types of tumor, such as breast cancer, head and neck squamous cell carcinoma, and primary rectal cancer. [8][9][10][11][12] In lymphomas, there is an additional, strong heterogeneity in NHL due to the considerable number of histological subtypes, [33][34][35][36] which further increases the tumor tissue heterogeneity between patients, adds to the biological complexity, and may be chiefly responsible for the variability detected in our study, as well as in previous studies. 3,15,16,19,25,37 Moreover, the quantitative ADC and SUV data are also influenced by several technical factors, such as the selection of the b-values, acquisition technique (EPI-SPAIR or STIR-based; free-breathing, breath-hold, or respiratory triggered), and the presence of artifacts for DWI.…”

Intratumoral genetic heterogeneity and number of cytogenetic aberrations provide additional prognostic significance in chronic lymphocytic leukemia

“…By taking note of the nonequilibrium percentages of tumor cells and the different cytogenetic aberrations involved, ITH can be analyzed using FISH, which was utilized in this study as reported previously. 30,31 In this study, we found that two genetic subclones could be distinguished in the presence of two or more aberrations detected by FISH. In patients with unfavorable clones (i.e., containing del 11q/del 17p), three genetic subclones could be defined.…”

Die-hard survivors: heterogeneity in apoptotic thresholds may underlie chemoresistance

“…Within a tumor, there may be great variability among cells in the levels of pro- and anti-apoptotic factors, with certain clones being more apoptosis reluctant than others. In support of this notion, it was recently discovered that extensive intratumor heterogeneity exists in Bcl-2 transcript levels in follicular lymphoma as assessed at the single-cell level [22]. Patient-derived lymphoma cells that expressed higher levels of Bcl-2 were more resistant to the cytotoxin doxorubicin.…”