Project description:Inhibitors of checkpoint kinase 1 (CHK1),a central component of DNA damage and cell cycle checkpoint response, represent a promising new cancer therapy, but the global cellular functionsthey regulate through phosphorylationare poorly understood. To elucidate the CHK1-regulated phosphorylation network, we performed a global quantitative phosphoproteomics analysis, which revealed 142 phosphositeswhose phosphorylation levels were significantly different following treatment with the CHK1 inhibitor SCH 900776.
Project description:Disease frameshift mutations of calreticulin (CALR) are the second most prevalent driver mutations in essential thrombocythemia (ET) and primary myelofibrosis (PMF). To identify potential targeted therapies for CALR mutated myeloproliferative neoplasms, we aimed to search for small molecule drugs that selectively inhibit the growth of CALR mutated cells using high-throughput drug screening. We investigated 89,172 compounds using isogenic cell lines and identified several hits targeting the ATR-CHK1 pathway. The selective inhibitory effect of these candidate compounds was validated in a co-culture assay of CALR mutated and wild type cells. Of the tested hit compounds, CHK1 inhibitors potently depleted CALR mutated cells, allowing CALR wild type cell dominance in the co-culture over time. Neither CALR deficient cells nor JAK2V617F mutated cells showed hypersensitivity to the drug treatment, suggesting that the vulnerability to ATR-CHK1 inhibition is specifically caused by the oncogenic activation by the mutant CALR. CHK1 inhibitors induced replication stress in CALR mutated cells revealed by elevated pan-nuclear staining for γH2AX and hyperphosphorylation of RPA2. They also promoted S-phase cell cycle arrest and blocked the completion of DNA replication in CALR mutated cells. Transcriptomic and phosphoproteomic analyses revealed a replication stress signature caused by the oncogenic CALR mutation, suggesting an intrinsic vulnerability of these cells to CHK1 perturbation. This study indicates that ATR-CHK1 pathway is a potential therapeutic target in CALR mutated hematopoietic cells.
Project description:Splicing factor SF3B1 mutations are frequent somatic lesions in myeloid neoplasms that transform hematopoietic stem cells (HSCs) by inducing mis-splicing of target genes. However, the molecular and functional consequences of SF3B1 mutations in human HSCs remain unclear. Here, we identify the mis-splicing program in human HSCs as a targetable vulnerability by precise gene editing of SF3B1 K700E mutations in primary CD34+ cells. Mutant SF3B1 induced pervasive mis-splicing and reduced expression of genes regulating mitosis in single cell transcriptomics, critically BUBR1 and CDC27, leading to altered differentiation and delayed G2/M progression. Mutant SF3B1 mis-splicing or reduced expression of BUBR1 and CDC27 was sufficient to delay G2/M transit, leading to activation of CHK1, sensitizing cells to CHK1 inhibition. Clinical CHK1 inhibitor prexasertib selectively targeted SF3B1-mutant HSCs and abrogated engraftment in vivo. These findings identify mis-splicing of mitotic regulators in SF3B1-mutant HSCs as a targetable vulnerability engaged by pharmacological CHK1 inhibition.
Project description:Splicing factor SF3B1 mutations are frequent somatic lesions in myeloid neoplasms that transform hematopoietic stem cells (HSCs) by inducing mis-splicing of target genes. However, the molecular and functional consequences of SF3B1 mutations in human HSCs remain unclear. Here, we identify the mis-splicing program in human HSCs as a targetable vulnerability by precise gene editing of SF3B1 K700E mutations in primary CD34+ cells. Mutant SF3B1 induced pervasive mis-splicing and reduced expression of genes regulating mitosis in single cell transcriptomics, critically BUBR1 and CDC27, leading to altered differentiation and delayed G2/M progression. Mutant SF3B1 mis-splicing or reduced expression of BUBR1 and CDC27 was sufficient to delay G2/M transit, leading to activation of CHK1, sensitizing cells to CHK1 inhibition. Clinical CHK1 inhibitor prexasertib selectively targeted SF3B1-mutant HSCs and abrogated engraftment in vivo. These findings identify mis-splicing of mitotic regulators in SF3B1-mutant HSCs as a targetable vulnerability engaged by pharmacological CHK1 inhibition.
Project description:Pancreatic ductal adenocarcinoma (PDA) is characterized by abundant desmoplasia and poor tissue perfusion. These features are proposed to limit access of therapies to neoplastic cells and blunt treatment efficacy. Indeed, several agents that target the PDA microenvironment promote chemotherapy delivery and improve anti-neoplastic responses in murine models of PDA. Here, we employed the FG-3019 monoclonal antibody directed against the pleiotropic matricellular signaling molecule connective tissue growth factor (CTGF/CCN2). FG-3019 treatment increased PDA cell killing and led to a dramatic tumor response without altering gemcitabine delivery. Microarray expression profiling revealed the down-regulation by FG-3019 of several anti-apoptotic transcripts, including the master regulator Xiap, down-regulation of which has been shown to sensitize PDA to gemcitabine. Decreases in XIAP protein by FG-3019 in the presence and absence of gemcitabine were confirmed by immunoblot, while increases in XIAP protein were seen in PDA cell lines treated with recombinant CTGF. Therefore, alterations in survival cues following targeting of tumor microenvironmental factors may play an important role in treatment responses in animal models and, by extension, PDA patients. Total RNA was isolated from KPC mouse PDA tumors 9 days after initiation of treatment with IgG (n=7 biological replicates), FG-3019 (n=5), IgG + gemcitabine (n=6), or FG-3019 + gemcitabine (n=6) and hybridized to Affymetrix 430A 2.0 microarrays. CEL files were processed by GC-RMA and rescaled using median per-gene normalization in GeneSpring GX 7.3.1.
Project description:Purpose: Gemcitabine is most commonly used for pancreatic cancer (PC). However, the molecular features and mechanisms of the frequently occurred resistance remain unclear. This work aims at exploring the molecular features of gemcitabine resistance and identifying candidate biomarkers and combinatorial targets for the treatment. Experimental Design: In present study, we established 66 patient-derived xenografts (PDXs) based on clinical PC specimens and treated them with gemcitabine. We generated multi-omics data (including whole exome-seq, RNA-seq, miRNA-seq and DNA methylation array) of 15 drug sensitive and 13 resistant PDXs before and after the gemcitabine treatment. We performed integrative computational analysis to identify the molecular networks related to gemcitabine intrinsic and required resistance. Then, shRNA-based high-content screening was implemented to validate the function of the de-regulated genes. Results: The comprehensive multi-omics analysis and functional experiment revealed that MRPS5 and GSPT1 had strong effects on cell proliferation, and CD55 and DHTKD1 contributed to gemcitabine resistance in PC cells. Moreover, we found miR-135a-5p was significantly associated with the prognosis of PC patients and could be a candidate biomarker to predict gemcitabine response. Comparing the molecular features before and after the treatment, we found that PI3K-Akt, p53, HIF-1 pathways were significantly altered in multiple patients, providing candidate target pathways for reducing the acquired resistance. Conclusions: This integrative genomic study systematically investigated the predictive markers and molecular mechanisms of chemoresistance in pancreatic cancer and provide potential therapy targets for overcoming gemcitabine resistance.
Project description:Purpose: Gemcitabine is most commonly used for pancreatic cancer (PC). However, the molecular features and mechanisms of the frequently occurred resistance remain unclear. This work aims at exploring the molecular features of gemcitabine resistance and identifying candidate biomarkers and combinatorial targets for the treatment. Experimental Design: In present study, we established 66 patient-derived xenografts (PDXs) based on clinical PC specimens and treated them with gemcitabine. We generated multi-omics data (including whole exome-seq, RNA-seq, miRNA-seq and DNA methylation array) of 15 drug sensitive and 13 resistant PDXs before and after the gemcitabine treatment. We performed integrative computational analysis to identify the molecular networks related to gemcitabine intrinsic and required resistance. Then, shRNA-based high-content screening was implemented to validate the function of the de-regulated genes. Results: The comprehensive multi-omics analysis and functional experiment revealed that MRPS5 and GSPT1 had strong effects on cell proliferation, and CD55 and DHTKD1 contributed to gemcitabine resistance in PC cells. Moreover, we found miR-135a-5p was significantly associated with the prognosis of PC patients and could be a candidate biomarker to predict gemcitabine response. Comparing the molecular features before and after the treatment, we found that PI3K-Akt, p53, HIF-1 pathways were significantly altered in multiple patients, providing candidate target pathways for reducing the acquired resistance. Conclusions: This integrative genomic study systematically investigated the predictive markers and molecular mechanisms of chemoresistance in pancreatic cancer and provide potential therapy targets for overcoming gemcitabine resistance.
Project description:Pancreatic ductal adenocarcinoma (PDAC) often presents at late clinical stages, and most patients are managed solely through palliative chemotherapy. With no approved treatment modalities for patients who progress on broad-spectrum chemotherapy, we set to identify druggable targets to prevent or reverse resistance to the first line anti-neoplastic Gemcitabine. In our first experiment, we used the well-established Panc1 cell line as an in vitro model of PDAC. Panc1 cells were incubated with a tolerable dose of Gemcitabine in vitro, and examined alterations in gene expression via single cell RNA sequencing. In our subsequent studies, we incubated Panc1 cells with increasing doses of Gemcitabine for several passages, until viable in approximately 10x the known IC50 value. These cells were designated Panc1-GR. Based on our observations in the prior experiment, Panc1-GR cells were compared to those treated with wither the Calmodulin inhibitor W-7, Calcium chelator BAPTA-AM, or the calcium channel blocker Amlodipine. Through these efforts, we hope to better understand the mechanisms of Gemcitabine resistance in PDAC, as well as introduce new therapeutic strategies to reverse drug resistant phenotypes in the clinic.