PDK1 Signaling Towards PLK1-Myc Activation Confers Oncogenic Transformation and Tumor Initiating Cell Activation and Resistance to mTOR-targeted Therapy.
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ABSTRACT: Although 3-Phosphoinositide-dependent protein kinase-1 (PDK1) has been predominately linked to PI3K-AKT pathway, it may also evoke additional signaling outputs to promote tumorigenesis. Here we report that PDK1 directly induces phosphorylation of Polo-like kinase 1 (PLK1), which in turn induces Myc phosphorylation and protein accumulation. We show that PDK1-PLK1-Myc signaling is critical for cancer cell growth and survival and small molecule inhibition of PDK1/PLK1 provides an effective approach for therapeutic targeting Myc-dependency. Intriguingly, PDK1-PLK1-Myc signaling induces an embryonic stem cell-like gene signature associated with aggressive tumor behaviors and is a robust signaling axis driving cancer stem cell (CSC) self renewal. Finally, we show that PLK1 inhibitor synergizes with mTOR inhibitor to induce synergistic anti-tumor effect in colorectal cancer by antagonizing a compensatory Myc induction. These findings identify a novel pathway in human cancer and CSC activation and provide a therapeutic strategy for targeting Myc-associated tumorigenesis and therapeutic resistance.
Project description:Although 3-Phosphoinositide-dependent protein kinase-1 (PDK1) has been predominately linked to PI3K-AKT pathway, it may also evoke additional signaling outputs to promote tumorigenesis. Here we report that PDK1 directly induces phosphorylation of Polo-like kinase 1 (PLK1), which in turn induces Myc phosphorylation and protein accumulation. We show that PDK1-PLK1-Myc signaling is critical for cancer cell growth and survival and small molecule inhibition of PDK1/PLK1 provides an effective approach for therapeutic targeting Myc-dependency. Intriguingly, PDK1-PLK1-Myc signaling induces an embryonic stem cell-like gene signature associated with aggressive tumor behaviors and is a robust signaling axis driving cancer stem cell (CSC) self renewal. Finally, we show that PLK1 inhibitor synergizes with mTOR inhibitor to induce synergistic anti-tumor effect in colorectal cancer by antagonizing a compensatory Myc induction. These findings identify a novel pathway in human cancer and CSC activation and provide a therapeutic strategy for targeting Myc-associated tumorigenesis and therapeutic resistance. Gene expression profiling of Human Embryonic Kidney Cells (HEK-TERV) under different conditions: PMN, PDK1, MYC and E545K
Project description:The role of PDK1 on mammary tumorigenesis and its interaction with PPARdelta, was assessed. Transgenic mice were generated in which PDK1 was expressed in the mammary epithelium. We used microarrays to analyse global gene expression changes in MMTV-PDK1 transgenic mice versus wild-type mice and determine any differential responses to GW501516 treatment.
Project description:The role of PDK1 on mammary tumorigenesis and its interaction with PPARdelta, was assessed. Transgenic mice were generated in which PDK1 was expressed in the mammary epithelium. We used microarrays to analyse global gene expression changes in MMTV-PDK1 transgenic mice versus wild-type mice and determine any differential responses to GW501516 treatment. RNA was isolated (RNeasy Mini Kit, Qiagen) from mammary gland tissue from nulliparious transgenic and wild-type mice maintained on normal rodent chow or a diet supplemented with GW501516 for 1 week.
Project description:Gene expression profiling was performed to access the changes in gene expression in melanomas from Pdk1-inactivated Brafv600E::Pten-/- mice. The expression profiles of the BrafV600E::Pten-/-::Pdk1-/- were compared to the BrafV600E::Pten-/-::Pdk+/+ genotypes. The analysis has identified several important signaling pathways in Pdk1-dependent melanomagenesis. Melanoma tumors from the BrafV600E::Pten-/-::Pdk1+/+ and BrafV600E::Pten-/-::Pdk1-/- genotypes were harvested and mRNA from each group was pooled to enable four biologically replicates analysis.
Project description:Gene expression profiling was performed to access the changes in gene expression in melanomas from Pdk1-inactivated Brafv600E::Pten-/- mice. The expression profiles of the BrafV600E::Pten-/-::Pdk1-/- were compared to the BrafV600E::Pten-/-::Pdk+/+ genotypes. The analysis has identified several important signaling pathways in Pdk1-dependent melanomagenesis.
Project description:This project consisted of three HDX-MS experiments. First, we compared the dimeric PDK1(SKD-PIF) to monomeric PDK1(SKD) and mapped the differences in deuterium incorporation onto the dimer model. We then compared the deuterium incorporation kinetics for the kinase (PDK1(SKD)) and PH (PDK1(PH) domains of PDK1 with full-length PDK1 (PDK1(FL)) in pairwise experiments.
Project description:Dysfunction of cell cycle genes can lead to mitosis disruption and chromosomal instability (CIN), which is blamed for poor prognosis in colorectal cancer (CRC) patients, no matter with chemotherapy or not. Discovery therapeutic targets to abnormal cell cycle pathways in CRC may help to improve current therapy. By genome-widely profiling of differential expressed genes in 54 pairs of human colorectal tumor with matched normal mucosa, we found a functional enrichment in PLK1 signaling. Tumors with enriched PLK1 signaling are accompanied with dysfunction pathways related to cell cycle. Total PLK1 and phosphorylated PLK1 protein expression are associated with tumor recurrence and poor overall survival in a cohort of CRC patients. Combining PLK1 inhibitor with oxaliplatin shows a synergize effect to suppress the growth of CRC cell lines, xenograft tumors, preclinical patient-derived organoid and patient-derived xenograft tumors. RNA-seq data reveals that the cell cycle pathways were activated in oxaliplatin group but inhibited after PLK1 inhibitor treatment. CDC7 may be a key downstream effector of PLK1 induced oxaliplatin resistance and can be druggable. Further investigation showed that PLK1 inhibitor suppress the CDC7 expression via c-MYC transcriptional control. A strong positive correlation between PLK1 and CDC7 has been further confirmed in patients. Strikingly, functional studies confirm that combining CDC7 inhibitor with oxaliplatin can recapitulate the synergize effect in various CRC models, highlighting pharmacological target PLK1-MYC-CDC7 signaling as a potential therapeutic strategy for oxaliplatin based chemotherapy.
Project description:Follicular helper T (Tfh) cells, as important effector CD4+ T cells, are able to regulate antigen-specific B cell immunity in vivo. It is well characterized that transcription factors, cytokines, microRNA, epigenetic modifications exerts important roles in Tfh differentiation and function. Howerer, the regulatory mechanism of the major signaling pathways driving Tfh cell differentiation remains unclear. Multiple mice models were used by a series of experimental approaches to illustrate PDK1 signaling programs Tfh differentiation and function.