Project description:Oncogenic KRAS mutations underlie some of the deadliest human cancers. Genetic or pharmacological KRAS inactivation produces mixed outcomes, ranging from complete regression to frequent relapse. Mechanisms underpinning the resistance of cancer cells to KRAS inactivation remain to be understood. Here we investigate a conceptual framework of pancreatic ductal adenocarcinoma showing that CRISPR-mediated KRAS ablation impedes tumor growth contingent on the concomitant inactivation of the STAT3 transcription factor. Mechanistically, the incurred losses of KRAS and STAT3 disrupt a temporal balance between tumor cell differentiation, proliferation, and self-renewal. This in turn impairs tumor growth in mice and enhances their immune rejection, resulting in tumor clearance. Our findings identify a specific role for STAT3 in supporting cancer cell fitness with a particular focus on KRAS-inhibited tumors and provide a rationale for developing therapies targeting mutant KRAS and STAT3.
Project description:Oncogenic STAT3 functions are known in various malignancies. We found that STAT3 plays an unexpected tumor suppressive role in KRAS-mutant non-small-cell-lung cancer (NSCLC). In mice, tissue-specific inactivation of Stat3 resulted in increased Kras (G12D)-driven NSCLC initiation and malignant progression leading to markedly reduced survival. Clinically, low STAT3 expression levels correlate with poor survival in human lung adenocarcinoma patients with smoking history. Consistently, KRAS-mutant lung tumors showed reduced STAT3 levels. Mechanistically, we show that STAT3 controls NFκB-induced IL-8-expression by sequestering NFκB in the cytoplasm while IL-8 in turn regulates myeloid tumor infiltration and tumor vascularization thereby promoting tumor progression. These results identify a novel STAT3-NFκB-IL-8 axis in KRAS-mutant NSCLC with therapeutic and prognostic relevance WT: Control lung; KRAS: Lung tumors expressing KRAS G12D; KRAS STAT3 KO: Lung tumors expressing KRAS G12D- STAT3 deficient; tumors of four mice pooled per sample
Project description:Oncogenic STAT3 functions are known in various malignancies. We found that STAT3 plays an unexpected tumor suppressive role in KRAS-mutant non-small-cell-lung cancer (NSCLC). In mice, tissue-specific inactivation of Stat3 resulted in increased Kras (G12D)-driven NSCLC initiation and malignant progression leading to markedly reduced survival. Clinically, low STAT3 expression levels correlate with poor survival in human lung adenocarcinoma patients with smoking history. Consistently, KRAS-mutant lung tumors showed reduced STAT3 levels. Mechanistically, we show that STAT3 controls NFκB-induced IL-8-expression by sequestering NFκB in the cytoplasm while IL-8 in turn regulates myeloid tumor infiltration and tumor vascularization thereby promoting tumor progression. These results identify a novel STAT3-NFκB-IL-8 axis in KRAS-mutant NSCLC with therapeutic and prognostic relevance
Project description:We have previously shown that Kras mutant-induced lung tumors in CCSPCre/LSL-K-rasG12D mice (CC-LR) exhibited Stat3 activation. Here we sought to study the role of epithelial Stat3 in Kras-mutant lung tumor oncogenesis through derivation of a lung epithelial specific CC-LR/Stat3 conditional knockout (LR/Stat3D/D or LRDD) model. Analysis of tumor burdens revealed marked gender disparity following epithelial Stat3 deletion, LRDD males exhibited increased tumor burdens compared to male CC-LR animals whereas female LRDD mice displayed attenuated tumor development when compared to female CC-LR littermates. We then performed RNA-sequencing of whole lungs from the mice in order to understand global expression programs that may underlie this gender-specific effect of epithelial Stat3 deletion.
Project description:Breast Cancer (BC) has been associated with alterations in signaling through a number of growth factor and hormone regulated pathways. Mouse models for metastatic BC have been developed using oncoproteins that activate PI3K, Stat3 and Ras signaling. To determine the role of each pathway, we analyzed mouse mammary tumor formation when they were activated singly or pairwise. We used microarrays to detect differentially expressed genes in the KRas(G12D/+);CreT and R26(H1047R/+);KRas(G12D/+);CreT tumors Total RNA was extracted from tumors developed by Qiagen RNAeasy kit and hybridized on Affymetrix microarrays.
Project description:Metabolic reprogramming is an active regulator of stem cell fate choices, and successful stem cell differentiation in different compartments requires the induction of oxidative phosphorylation. However, the mechanisms that promote mitochondrial respiration during stem cell differentiation are poorly understood. Here we demonstrate that Stat3 promotes muscle stem cell myogenic lineage progression by stimulating mitochondrial respiration. We identify Fam3a, a cytokine-like protein, as a major Stat3 downstream effector in muscle stem cells. We demonstrate that Fam3a is required for muscle stem cell commitment and skeletal muscle development. We show that myogenic cells secrete Fam3a, and exposure of Stat3-ablated muscle stem cells to recombinant Fam3a in vitro and in vivo rescues their defects in mitochondrial respiration and myogenic commitment. Together, these findings indicate that Fam3a is a Stat3-regulated secreted factor that promotes muscle stem cell oxidative metabolism and differentiation, and suggests that Fam3a is a potential tool to modulate cell fate choices.
Project description:Evaluation of the role of RIP4 in lung adenocarcinoma revealed that RIP4 inhibits STAT3 signaling in vitro and in vivo. Repression of RIP4 enhanced STAT3 signaling activation in KRAS LSL/G12D/wt; p53flox/flox murine tumors. This promoted cancer dedifferentiation through ECM remodeling
Project description:Breast Cancer (BC) has been associated with alterations in signaling through a number of growth factor and hormone regulated pathways. Mouse models for metastatic BC have been developed using oncoproteins that activate PI3K, Stat3 and Ras signaling. To determine the role of each pathway, we analyzed mouse mammary tumor formation when they were activated singly or pairwise. We used microarrays to detect differentially expressed genes in the KRas(G12D/+);CreT and R26(H1047R/+);KRas(G12D/+);CreT tumors
Project description:Colorectal cancer (CRC) tumors start as precancerous polyps on the inner lining of the colon or rectum, where they are exposed to the mechanics of colonic peristalsis. Our previous work leveraged a custom-built peristalsis bioreactor to demonstrate that colonic peristalsis led to cancer stem cell enrichment in colorectal cancer cells. However, this malignant mechanotransductive response was confined to select CRC lines that harbored an oncogenic mutation in the KRAS gene. In this work, therefore, we explored the involvement of activating KRAS mutations on peristalsis-associated mechanotransduction in CRC. Peristalsis enriched the cancer stem cell marker LGR5 in KRAS mutant (G13D, etc.) lines, in a Wnt-independent manner. Conversely, LGR5 enrichment in wild type KRAS lines exposed to peristalsis were minimal. LGR5 enrichment downstream of peristalsis translated to increased tumorigenicity in vivo in KRAS mutant vs. wild type lines. Differences in mechanotransduction response was additionally apparent via unbiased gene set enrichment analysis, where many unique pathways were enriched in wild type vs. mutant lines, in response to peristalsis. Interestingly, peristalsis also triggered β-catenin nuclear localization independent of Wnt, particularly in KRAS mutant lines. The central involvement of KRAS in the mechanotransductive responses was validated via gain and loss of function strategies. β-catenin activation and LGR5 enrichment downstream of peristalsis converged to the activation of the MEK/ERK kinase cascade, that remains active in cells that harbor oncogenic KRAS mutations. Taken together, our results demonstrated that oncogenic KRAS mutations conferred a unique peristalsis-associated mechanotransduction response to colorectal cancer cells, resulting in cancer stem cell enrichment and increased tumorigenicity. These mechanosensory connections can be leveraged in improving the sensitivity of emerging therapies that target oncogenic KRAS.