Project description:The hotspot c.7541_7542delCT NOTCH1 mutation has been proven to have a unfavorable clinical impact in chronic lymphocytic leukemia (CLL). The aim of our study was to investigate the influence of NOTCH1 mutation(c.7541_7542delCT) on NOTCH1 signaling in CLL cells using Gene Expression Profiling.
Project description:Functional studies to investigate gene mutations recurrent in B cell lymphoma have been hampered by the inability to genetically manipulate primary cells, attributed to low transduction efficacy and procedure-associated toxicity. Alternative approaches utilize cell lines and mouse models, which often only poorly represent the genomic complexity and biology of the primary malignancy. To overcome these limitations, we have developed a method to retrovirally transfer genes into primary malignant B cells with high transduction efficacy and minimal toxicity. Using this method, we investigated the functions of NOTCH1, the most commonly mutated gene in CLL, by generating isogenic primary tumor cells from patients with Chronic Lymphocytic Leukemia (CLL) and Mantle Cell Lymphoma (MCL), differing only in their expression of NOTCH1. Our data demonstrate that NOTCH1 facilitates immune escape of malignant B cells by up-regulating PD-L1, partly dependent on autocrine interferon-g signaling. In addition, NOTCH1 causes silencing of the entire HLA-class II locus via suppression of the transcriptional co-activator CIITA. These NOTCH1-mediated immune escape mechanisms are associated with the expansion of CD4+ T cells in vivo, further contributing to the poor clinical outcome of NOTCH1-mutated CLL and MCL
Project description:NOTCH1 is mutationally activated in ~15% of cases of chronic lymphocytic leukaemia (CLL), but its role in B-cell development and leukemogenesis is not known. Here, we report that the active intracellular portion of NOTCH1 (ICN1) is detectable in ~50% of peripheral blood CLL cases lacking gene mutations. We identify a ‘NOTCH1 CLL gene expression signature’ in CLL cells, and show that this signature is significantly enriched in primary CLL cases expressing ICN1, independent of NOTCH1 mutation. NOTCH1 target genes include key regulators of B-cell proliferation, survival and signal transduction physiology. In particular, we show that MYC is a direct target of NOTCH1 via B-cell specific distal regulatory elements, thus implicating this oncogene in the pathogenesis of the disease.
Project description:NOTCH1 is mutationally activated in ~15% of cases of chronic lymphocytic leukaemia (CLL), but its role in B-cell development and leukemogenesis is not known. Here, we report that the active intracellular portion of NOTCH1 (ICN1) is detectable in ~50% of peripheral blood CLL cases lacking gene mutations. We identify a ‘NOTCH1 CLL gene expression signature’ in CLL cells, and show that this signature is significantly enriched in primary CLL cases expressing ICN1, independent of NOTCH1 mutation. NOTCH1 target genes include key regulators of B-cell proliferation, survival and signal transduction physiology. In particular, we show that MYC is a direct target of NOTCH1 via B-cell specific distal regulatory elements, thus implicating this oncogene in the pathogenesis of the disease.
Project description:Despite an intensive search for non-coding cancer drivers, only a few have been discovered to date and none have been found among the RNAs contributing to the spliceosome. Here we report a highly recurrent A>C somatic mutation at the third base of U1 spliceosomal RNA in several tumour types. This mutation changes the preferential A-U base-pairing between U1 and 5′ splice site to C-G base-pairing, thereby creating novel splice junctions and altering the splice pattern of multiple genes, including those related to cancer. Clinically, the A>C mutation is associated with alcohol consumption in hepatocellular carcinoma and the aggressive IGHV unmutated subtype of chronic lymphocytic leukaemia (CLL). The U1 hotspot mutation confers an adverse prognosis to CLL patients independently, and may represent a new target for treatment. Our study demonstrates one of the first non-coding drivers in spliceosomal RNAs and reveals a novel mechanism of aberrant splicing in human cancer.
Project description:<p><b>Analysis of the chronic lymphocytic leukemia coding genome: role of NOTCH1 mutational activation</b></p> <p>The pathogenesis of chronic lymphocytic leukemia (CLL), the most common leukemia in adults, is still largely unknown since the full spectrum of genetic lesions that are present in the CLL genome, and therefore the number and identity of dysregulated cellular pathways, have not been identified. By combining next-generation sequencing and copy number analysis, we show here that the typical CLL coding genome contains less than 20 clonally represented gene alterations/case, including predominantly non-silent mutations and fewer copy number aberrations. These analyses led to the discovery of several genes not previously known to be altered in CLL. While most of these genes were affected at low frequency in an expanded CLL screening cohort, mutational activation of NOTCH1, observed in 8.3% of CLL at diagnosis, was detected at significantly higher frequency during disease progression toward Richter transformation (31.0%) as well as in chemorefractory CLL (20.8%). Consistent with the association of NOTCH1 mutations with clinically aggressive forms of the disease, NOTCH1 activation at CLL diagnosis emerged as an independent predictor of poor survival. These results provide initial data on the complexity of the CLL coding genome and identify a dysregulated pathway of diagnostic and therapeutic relevance.</p> <p><b>Genetic Lesions associated with Chronic Lymphocytic Leukemia transformation to Richter Syndrome</b></p> <p>Richter syndrome (RS) derives from the rare transformation of chronic lymphocytic leukemia (CLL) into an aggressive lymphoma, most commonly of the diffuse large B cell type (DLBCL). The molecular pathogenesis of RS is only partially understood. By combining whole-exome sequencing and copy-number analysis of 9 CLL-RS pairs and of an extended panel of 43 RS cases, we show that this aggressive disease typically arises from the predominant CLL clone by acquiring an average of ~20 genetic lesions/case. RS lesions are heterogeneous in terms of load and spectrum among patients, and include those involved in CLL progression and chemorefractoriness (TP53 disruption and NOTCH1 activation) as well as some not previously implicated in CLL or RS pathogenesis. In particular, disruption of the CDKN2A/B cell cycle regulator locus is associated with ~30% of RS cases. Finally, we report that the genomic landscape of RS is significantly different from that of de novo DLBCL, suggesting that they represent distinct disease entities. These results provide insights into RS pathogenesis, and identify dysregulated pathways of potential diagnostic and therapeutic relevance.</p>