Project description:We designed two different BCL2 deregulation models in transgenic mice, whereby the oncogene was either associated with the IgH3′RR superenhancer, as in t(14;18), or inserted into the kappa light chain locus. We compared the impact of these models on B-cell fate and lymphoid tissues. Linkage to the IgH superenhancer showed a quite specific impact on germinal center B cell populations. The Ig kappa model was much less specific and strongly boosted the plasma cell in-flow and the accumulation of long-lived plasma cells.
Project description:We designed two different BCL2 deregulation models in transgenic mice, whereby the oncogene was either associated with the IgH3′RR superenhancer, as in t(14;18), or inserted into the kappa light chain locus. We compared the impact of these models on B-cell fate and lymphoid tissues. Linkage to the IgH superenhancer showed a quite specific impact on germinal center B cell popu-lations. The Ig kappa model was much less specific and strongly boosted the plasma cell in-flow and the accumulation of long-lived plasma cells.
Project description:Upregulated expression of the anti-apoptotic BCL2 oncogene is a common feature of various types of B-cell malignancies, from lymphoma to leukemia or myeloma. It is currently unclear how the various patterns of deregulation observed in pathology eventually impact the phenotype of malignant B cells and their microenvironment. Follicular lymphoma (FL) is the most common non-Hodgkin lymphoma arising from malignant germinal center (GC) B-cells, and its major hallmark is the t(14:18) translocation occurring in B cell progenitors and placing the BCL2 gene under the control of the immunoglobulin heavy chain locus regulatory region (IgH 3'RR), thus exposing it to constitutive expression and hypermutation. Translocation of BCL2 onto Ig light chain genes, BCL2 gene amplification, and other mechanisms yielding BCL2 over-expression are, in contrast, rare in FL and rather promote other types of B-cell lymphoma, leukemia, or multiple myeloma. In order to assess the impact of distinct BCL2 deregulation patterns on B-cell fate, two mouse models were designed that associated BCL2 and its full P1-P2 promoter region to either the IgH 3'RR, within a "3'RR-BCL2" transgene mimicking the situation seen in FL, or an Ig light chain locus context, through knock-in insertion at the Igκ locus ("Igκ-BCL2" model). While linkage to the IgH 3' RR mostly yielded expression in GC B-cells, the Igκ-driven up-regulation culminated in plasmablasts and plasma cells, boosting the plasma cell in-flow and the accumulation of long-lived plasma cells. These data demonstrate that the timing and level of BCL2 deregulation are crucial for the behavior of B cells inside GC, an observation that could strongly impact the lymphomagenesis process triggered by secondary genetic hits.
Project description:Activation of the MYC oncogene is common in B-cell lymphomas, and frequently associated with compensatory events that dampen Myc-induced apoptosis, such as over-expression of anti-apoptotic Bcl2-family proteins. For example, concurrent translocations of MYC and BCL2 in a subset of Diffuse large B-cell lymphoma (DLBCL) lead to the high-grade “double-hit” lymphoma subtype (DHL), characterized by dismal prognosis in the face of current front-line regimens, thus calling for the pursuit of tailored therapeutic strategies. Here, we show that Myc and Bcl2 modulate the sensitivity of B-cells to IACS-010759, a selective inhibitor of mitochondrial respiratory complex I. Myc activation in non-transformed lymphoid precursors suppressed endogenous Bcl2 and sensitized the cells to IACS-010759-induced apoptosis. Treatment with the Bcl2 inhibitor venetoclax also sensitized to IACS-010759, while overexpression of Bcl-2 was protective. IACS-010759 engaged an ATF4-driven Integrated Stress Response (ISR) with dual anti- and pro-apoptotic effects, the latter mediated by the CHOP transcription factor, which contributed to selective killing of Myc-overexpressing cells. In line with the above data, IACS-010759 and venetoclax synergized in killing human DHL cells, and showed strong combinatorial effects in a pre-clinical setting. In a Bcl2-negative Burkitt’s lymphoma cell line, instead, IACS-010759 synergized with the Mcl-1 inhibitor S63845. Altogether, our data point to the combination of IACS-010759 with distinct Bcl2-family inhibitors for therapeutic reactivation of the intrinsic apoptotic pathway in Myc-associated B-cell lymphomas
Project description:Mouse fetal liver-derived primary B-cells exogenously expressing various combinations of Bcl2, Myc and Ccnd1 were compared with each other.
Project description:Intratumor heterogeneity (ITH) in oncogene expression is common in cancer, but it is not known if oncogenes exert combinatorial effects at the single cell level to influence clinical outcome. We address this question using quantitative spectral imaging to simultaneously measure the cellular co-expression of the oncogenes MYC, BCL2 and BCL6 in clinically annotated cohorts of Diffuse Large B-Cell Lymphoma (DLBCL). Unlike in non-malignant lymphoid tissue, where the co-expression of these oncogenes is spatially constrained, DLBCL samples show multiple permutations of oncogenic co-expression at the single cell level. Oncogene co-expression follows clustered and non-random spatial distribution, and is typically stable across different regions of a tumour. Interestingly, we noted that the extent of cells with the unique oncogene combination MYC+BCL2+BCL6- (M+2+6-) associates consistently with patient survival across three independent DLBCL cohorts. We then show that the fraction of M+2+6- co-expressing cells can be inferred from quantitative single oncogene data, as the overall frequencies of co-expression of these oncogenes are stochastic. Predicted values of M+2+6- cellular co-expression frequency from immunohistochemistry of MYC/BCL2/BCL6 (n=316) and multiple independent gene expression datasets (n=2522; 8 cohorts) consistently correlate with survival after R-CHOP chemotherapy, offering a novel strategy for identification of high-risk DLBCL. Finally, we use comparative RNAseq analysis of patient-derived M+2+6+ and M+2+6- B-cells to identify cyclin D2 as a potential BCL6-repressed mediator of the aggressive behavior of M+2+6- population. Overall, our work demonstrates that patterns of oncogene co-expression analyzed at single-cell resolution are clinically relevant, with implications for both diagnostics and target discovery in other cancer types.
Project description:Identification of novel vulnerabilities in the context of therapeutic resistance is emerging as key challenge for cancer treatment. Recent studies have detected pervasive aberrant splicing in cancer cells, supporting its targeting for treatment of hematological malignancies.We here evaluated the expression of several spliceosome machinery components in primary multiple myeloma (MM) cells and the impact of splicing modulations on MM cell growth and viability.Our comprehensive gene expression analysis confirmed deregulation of spliceosome machinery components in MM cells compared to normal plasma cells (PCs) from healthy donors, while pharmacological and genetic modulation of splicing confirmed significant impact on growth and survival of MM cell lines and patient-derived malignant PCs. Transcriptomic analysis revealed deregulation of BCL2 family membersincluding decrease of proapoptotic long form of myeloid cell leukemia-1 (MCL1) expression in cells treated with splicing inhibitors. This caused a shift in the apoptotic priming resulting in improved BCL2-dependenceand increased sensitivity to Venetoclax, a BCL2 small molecule inhibitor, in vitro and in vivo. Overall, our data provide a rationale for supporting clinical use of splicing modulators as strategy to reprogram apoptotic dependencies, making MM patients more vulnerable to BCL2 inhibitors.
Project description:SOX9 was identified as a prognostic biomarker particularly in IGH-BCL2 translocated germinal center B cell (GCB) subtypes of the diffuse large B cell lymphoma (DLBCL) and plays a vital role in lymphomagenesis. However, the molecular mechanism that modulating the aberrant expression of SOX9 in this DLBCL subset remains unknown. We have demonstrated that SOX9 enhanced IGH-BCL2 positive DLBCL subset resistance to either chemotherapy or BCL2 inhibitor. Moreover, we found that inhibition of BCL2 downregulates SOX9 in IGH-BCL2 positive DLBCL subset. We further identified that IRF4 is a key regulator to mediate BCL2 induced SOX9 expression, alongside with the chip-seq confirmed that IRF4 is a key transcription factor for SOX9 in DLBCL. In addition, BCL2 promote IRF4 entry into the nucleus by enhancing its protein stability, via downregulating of proteosome ubiquitination process, and, therefore, enforce SOX9-mediated phenotypes. Finally, we showed in DLBCL cell lines and xenografted mice model that in vivo inhibition of IRF4 with hIRF4 antisense oligonucleotide (ASO) repressed lymphomagenesis and DLBCL chemoresistance. Altogether, our data support the conclusion that IRF4 plays an essential role in BCL2 induced upregulation of SOX9 expression, and targeting IRF4 may represent a promising therapeutic strategy to cure relapse and refractory DLBCL in the future.