Project description:Unresectable hepatic metastasis of colorectal cancer (CRC) responds poorly to existing therapies and is the leading cause of CRC mortality. Runt-related transcription factors (RUNXs) have recently come to prominence because of their important, at times paradoxical, roles in tumor development. However, the expression status, biological function and underlying mechanism of RUNX1 in human CRC remain unknown.
Project description:CDK8 Mediator kinase is amplified and overexpressed in colon cancers; elevated CDK8 expression is associated with shorter patient survival. Nevertheless, CDK8 kinase inhibitors do not generally suppress colon cancer growth. We addressed this paradox by investigating the effects of CDK8 knockdown or a CDK8 kinase inhibitor on tumor growth at primary and metastatic sites. CDK8 knockdown or inhibition had no significant effect on primary tumors but suppressed the growth of hepatic metastases in murine and human colon cancer models. The effect of CDK8 inhibition on liver metastasis is mediated by upregulation of matrix metalloproteinase (MMP) inhibitor TIMP3 and downregulation of several MMPs.
Project description:CDK8 Mediator kinase is amplified and overexpressed in colon cancers; elevated CDK8 expression is associated with shorter patient survival. Nevertheless, CDK8 kinase inhibitors do not generally suppress colon cancer growth. We addressed this paradox by investigating the effects of CDK8 knockdown or a CDK8 kinase inhibitor on tumor growth at primary and metastatic sites. CDK8 knockdown or inhibition had no significant effect on primary tumors but suppressed the growth of hepatic metastases in murine and human colon cancer models. The effect of CDK8 inhibition on liver metastasis is mediated by upregulation of matrix metalloproteinase (MMP) inhibitor TIMP3 and downregulation of several MMPs.
Project description:CDK8 Mediator kinase drives colon cancer hepatic metastasis by regulating gene expression of the matrix metalloproteinase network [Illumina]
Project description:The Mediator complex is an evolutionarily conserved regulator of gene expression, influencing chromatin structure and RNA polymerase II-mediated transcription. Its activity is modulated by a protein kinase module, which includes cyclin-dependent kinases 8 and 19, that phosphorylate RNA polymerase II and transcription factors to regulate gene expression. CDK8 exhibits both oncogenic and tumour-suppressive activities depending on the cellular context, while the contributions of CDK19 remain less well understood. Based on prior data with our CDK8/19 inhibitor - 3,4,5-trisubstituted pyridine compound CCT251545 - we selected the human colorectal cancer cell line COLO205 for profiling experiments. This model is highly dependent on mutant BRAF and oncogenic β-catenin-driven WNT signaling and exhibits high basal β-catenin-dependent TCF/LEF promoter activity, which is sensitive to CDK8/19 inhibition in vitro and in vivo.
Project description:We use biochemically reconstituted transcription initiation components including the Mediator core and Cdk8 kinase modules (CKM) to investigate the function of the CKM in regulating the Mediator-RNA polymerase II interaction in a highly purified system. We use cross-linking coupled to mass spectrometry to map the interaction of the CKM and core Mediator, and in vitro phosphorylation assays followed by phosphopeptide enrichment coupled to mass spectrometry to identify Cdk8 phosphorylation targets in this context and biochemically dissect their functions. Finally, we investigate the function of phosphorylation by Cdk8 on transcription in vivo. Based on that, we propose a model to integrate the phosphorylation-dependent and -independent functions of the CKM in transcription initiation.
Project description:Triple-negative breast cancer (TNBC) is an aggressive malignant disease that is responsible for approximately 15% of breast cancers. The standard of care relies on surgery and chemotherapy but the prognosis is poor and there is an urgent need for new therapeutic strategies. Recent in silico studies have revealed an inverse correlation between recurrence-free survival and the level of cyclin- dependent kinase 8 (CDK8) in breast cancer patients. CDK8 is known to have a role in natural killer (NK) cell cytotoxicity, but its function in TNBC progression and immune cell recognition or escape has not been investigated. We have used a murine model of orthotopic breast cancer to study the tumor-intrinsic role of CDK8 in TNBC. Knockdown of CDK8 in TNBC cells impairs tumor regrowth upon surgical removal and prevents metastasis. In the absence of CDK8, the epithelial-to-mesenchymal transition (EMT) is impaired and immune-mediated tumor-cell clearance is facilitated. CDK8 drives EMT in TNBC cells in a kinase-independent manner. In vivo experiments have confirmed that CDK8 is a crucial regulator of NK-cell-mediated immune evasion in TNBC. The studies also show that CDK8 is involved in regulating the checkpoint inhibitor programmed death-ligand 1 (PD-L1). The CDK8–PD-L1 axis is found in mouse and human TNBC cells, underlining the importance of CDK8-driven immune cell evasion in these highly aggressive breast cancer cells. Our data link CDK8 to PD-L1 expression and provide a rationale for investigating the possibility of CDK8-directed therapy for TNBC.
Project description:Hormone therapy targeting estrogen receptor (ER) is the principal treatment for ER-positive breast cancers but many cancers develop resistance to anti-estrogens. Cyclin-dependent kinase 8 (CDK8) is a transcriptional regulator of several oncogenic pathways. Expression levels of CDK8 and ERα are inversely correlated in breast cancers suggesting a functional association between CDK8 and ER. CDK8 inhibition by selective small-molecule inhibitors, by shRNA knockdown or by CRISPR-Cas9 knockout suppressed estrogen-induced transcription, with no significant effects on ERα protein expression or phosphorylation. CDK8 inhibition also abrogated the mitogenic effect of estrogen on ER-positive breast cancer cells and potentiated growth inhibition by the ER antagonist fulvestrant. In vivo, administration of a CDK8 inhibitor suppressed ER-positive breast cancer xenograft growth and augmented the effects of fulvestrant with no apparent toxicity. CDK8 inhibitors also suppressed the development of estrogen independence in ER-positive breast cancer cells. These results identify CDK8 as a novel drug target for breast cancer therapy.
Project description:This SuperSeries is composed of the following subset Series: GSE30815: CDK8 knockdown in HT-29 human colon cancer cells GSE30816: CDK8 and MED12 knockdown in R1 mouse ES cells Refer to individual Series