Project description:The requirement for the B cell transcription factor OCT2 (encoded by Pou2f2) in germinal center B cells has proved controversial. Here, we report that germinal center B cells are formed normally after depletion of OCT2 in a conditional knockout mouse but that their proliferation is reduced and in vivo differentiation to antibody-secreting plasma cells is blocked. This led us to examine the role of OCT2 in germinal center derived lymphomas. ShRNA knockdown showed that almost all DLBCL cell lines are addicted to the expression of OCT2 and its co-activator OCA-B. Genome-wide chromatin Immunoprecipitation analysis and gene expression profiling revealed the broad transcriptional program regulated by OCT2 that includes the expression of STAT3, IL10, ELL2, XBP1, MYC, TERT and ADA. Importantly, genetic alteration of OCT2 is not a requirement for cellular addiction in DLBCL. However, we detected amplifications of the POU2F2 locus in DLBCL tumor biopsies as well as a recurrent mutation of threonine 223 in the DNA binding domain of OCT2. This neomorphic mutation subtly alters the DNA binding preference of OCT2 leading to the transactivation of novel target genes including HIF1a and FCRL3. Finally, by introducing mutations designed to disrupt the OCT2-OCA-B interface we reveal a requirement for this protein-protein interface that might ultimately be exploited therapeutically. Our findings, combined with the predominantly B cell restricted expression of OCT2 and the absence of systemic phenotype in our knockout mice, suggest that an OCT2-targeted therapeutic strategy would be efficacious in both major subtypes of DLBCL whilst avoiding systemic toxicity.
Project description:The requirement for the B cell transcription factor OCT2 (encoded by Pou2f2) in germinal center B cells has proved controversial. Here, we report that germinal center B cells are formed normally after depletion of OCT2 in a conditional knockout mouse but that their proliferation is reduced and in vivo differentiation to antibody-secreting plasma cells is blocked. This led us to examine the role of OCT2 in germinal center derived lymphomas. ShRNA knockdown showed that almost all DLBCL cell lines are addicted to the expression of OCT2 and its co-activator OCA-B. Genome-wide chromatin Immunoprecipitation analysis and gene expression profiling revealed the broad transcriptional program regulated by OCT2 that includes the expression of STAT3, IL10, ELL2, XBP1, MYC, TERT and ADA. Importantly, genetic alteration of OCT2 is not a requirement for cellular addiction in DLBCL. However, we detected amplifications of the POU2F2 locus in DLBCL tumor biopsies as well as a recurrent mutation of threonine 223 in the DNA binding domain of OCT2. This neomorphic mutation subtly alters the DNA binding preference of OCT2 leading to the transactivation of novel target genes including HIF1a and FCRL3. Finally, by introducing mutations designed to disrupt the OCT2-OCA-B interface we reveal a requirement for this protein-protein interface that might ultimately be exploited therapeutically. Our findings, combined with the predominantly B cell restricted expression of OCT2 and the absence of systemic phenotype in our knockout mice, suggest that an OCT2-targeted therapeutic strategy would be efficacious in both major subtypes of DLBCL whilst avoiding systemic toxicity.
Project description:B-cell receptor (BCR) signaling promotes the survival of malignant B cells, such as Burkitt’s lymphoma (BL) and the activated B-cell-like subtype of diffuse large B cell lymphoma (ABC-DLBCL). In contrast to ABC DLBCL, where malignant cells require chronic activation of the BCR for their survival, BL cells are dependent on tonic BCR signaling that is antigen-independent. Elucidation and systematic comparison of tonic and activated BCR signaling led to the identification of novel signaling effectors, among them ACTN4 and ARFGEF2, which were identified as regulators of BL cell survival. As tonic and activated BCR signaling are relevant for important aspects of B cell biology, our study helps in gaining an understanding of BCR-induced processes not only in malignant but potentially also physiological settings.
Project description:The Homeobox (HOX) family of genes encodes transcription factors involved in basic developmental processes, most notably during embryogenesis. A possible HOX gene link between development and oncogenesis has recently been described. Dysregulation of HOX genes may be an early event in malignant transformation likely to induce antibody response and thus provide a potential marker for early diagnosis of cancer. Ovarian cancer is characterized by poor early detection and serves as an excellent model system to develop potential markers for early diagnosis. In this study we begin to characterize HOX gene expression in malignant tumors of the ovary and analyze the potential role of HOX genes as biomarkers for early detection of ovarian cancer. Microarray analysis of mRNA from human ovarian tissues was performed on 65 samples of normal, benign, borderline malignant and malignant ovarian tissue. These samples were analyzed using the Affymetrix Human Genome Focus GeneChip (HG-Focus) microarray to distinguish the differential pattern of mRNA expression between the four types of samples. Real-time reverse transcription PCR was utilized to confirm up-regulation of HOX genes as determined by microarray analysis. Our results demonstrate multiple HOX genes to be up-regulated in ovarian cancer. We have shown stepped increase in HOX expression comparing normal, benign neoplastic, and malignant human ovarian tissue samples. This suggests dysregulation of HOX genes may be an early event in malignant transformation and warrants additional studies to validate HOX gene products as potential markers for early detection of ovarian cancer. Experiment Overall Design: 67 samples were analyzed. 4 groupings based on pathology (normal, benign, borderline malignant, malignant). An average of normal samples was used as controls. Cell lines were used as ovarian cancer control samples.