Hypoxic tumor microenvironment activates GLI2 via HIF-1? and TGF-?2 to promote chemoresistance in colorectal cancer.
ABSTRACT: Colorectal cancer patients often relapse after chemotherapy, owing to the survival of stem or progenitor cells referred to as cancer stem cells (CSCs). Although tumor stromal factors are known to contribute to chemoresistance, it remains not fully understood how CSCs in the hypoxic tumor microenvironment escape the chemotherapy. Here, we report that hypoxia-inducible factor (HIF-1?) and cancer-associated fibroblasts (CAFs)-secreted TGF-?2 converge to activate the expression of hedgehog transcription factor GLI2 in CSCs, resulting in increased stemness/dedifferentiation and intrinsic resistance to chemotherapy. Genetic or small-molecule inhibitor-based ablation of HIF-1?/TGF-?2-mediated GLI2 signaling effectively reversed the chemoresistance caused by the tumor microenvironment. Importantly, high expression levels of HIF-1?/TGF-?2/GLI2 correlated robustly with the patient relapse following chemotherapy, highlighting a potential biomarker and therapeutic target for chemoresistance in colorectal cancer. Our study thus uncovers a molecular mechanism by which hypoxic colorectal tumor microenvironment promotes cancer cell stemness and resistance to chemotherapy and suggests a potentially targeted treatment approach to mitigating chemoresistance.
Project description:Microenvironment has been suggested as an important factor contributing to how the colorectal cancer cells escape therapy, but the exact mechanism leading to chemoresistance remains elusive. Here, through modeling in vitro by cocultivation of patient-derived cancer associated fibroblasts (CAFs) with cancer stem cells (CSCs), we show that CAFs-secreted TGF-β2 is a key stromal factor that coordinates with hypoxia to promote CSC stemness and resistance to chemotherapy. GLI2, a key transcription factor of Hedgehog pathway, was identified as both necessary and sufficient in this process in which TGF-β and hypoxia-inducible factor (HIF-1α) synergize to directly induce GLI2 expression. Conversely, CSC-secreted TGF-β is also important to support the growth of CAFs but instead induce death of normal fibroblasts, suggesting a reciprocal mechanism to selectively support the CAF-CSC interaction. Small molecule inhibition of both TGF-β and GLI2 effectively reversed the chemoresistance. Finally, expression of TGFB2/HIF1A/GLI2 gene signature as a functional readout of this resistance pathway defines worse clinical outcomes and predicts patients relapse. Our observations uncover a key role of TGF-β/HIF-1α/GLI2 in microenvironment-mediated chemoresistance and reveal novel biomarker and targeting strategies to identify and treat the high risk CRC patients.
Project description:Colorectal cancer stem cells (CSCs), characterized by self-renewal ability and high expression of proliferative genes, contribute to the chemoresistance of colorectal cancer (CRC). We aimed to identify the molecular mechanisms underlying CRC chemoresistance through comprehensive bioinformatics screenings and experimental confirmation of gene functions. We found that high expression of FGF1 intracellular binding protein (FIBP) was correlated with chemoresistance and poor prognosis in CRC patients. Therefore, the chemoresistant CRC cell line HCT116-CSC with high expression of the stem cell markers CD44 and CD133 was established for further phenotypic tests. FIBP knockdown inhibited proliferation, enhanced chemotherapy effects, and attenuated the stemness markers of CRC cells in vivo and in vitro. Through RNA-seq and gene set enrichment analysis, we identified cyclin D1 as a key downstream target in FIBP-regulated cell cycle progression and proliferation. Moreover, FIBP bound to GSK3?, inhibited its phosphorylation at Tyr216, and activated ?-catenin/TCF/cyclin D1 signaling in HCT116-CSCs. Additional GSK3? knockdown reversed the FIBP silencing-induced inhibition of proliferation and decreased stemness marker expression in HCT116-CSCs. Furthermore, DNA methylation profiling suggested that FIBP regulated the stemness of CRC cells via methylation activity that was dependent on GSK3? but independent of ?-catenin signaling. Our data illuminate the potential of FIBP as a novel therapeutic target for treating chemoresistant CRC through inhibition of GSK3?-related signaling.
Project description:Colorectal cancer (CRC) patients develop recurrence after chemotherapy owing to the survival of stem cell-like cells referred to as cancer stem-like cells (CSCs). The origin of CSCs is linked to the epithelial-mesenchymal transition (EMT) process. Currently, it remains poorly understood how EMT programmes enable CSCs residing in the tumour microenvironment to escape the effects of chemotherapy. This study identifies a key molecular pathway that is responsible for the formation of drug-resistant CSC populations. Using a modified yeast-2-hybrid system and 2D gel-based proteomics methods, we show that the E3-ubiquitin ligase FBXW7 directly binds and degrades the EMT-inducing transcription factor ZEB2 in a phosphorylation-dependent manner. Loss of FBXW7 induces an EMT that can be effectively reversed by knockdown of ZEB2. The FBXW7-ZEB2 axis regulates such important cancer cell features, as stemness/dedifferentiation, chemoresistance and cell migration in vitro, ex vivo and in animal models of metastasis. High expression of ZEB2 in cancer tissues defines the reduced ZEB2 expression in the cancer-associated stroma in patients and in murine intestinal organoids, demonstrating a tumour-stromal crosstalk that modulates a niche and EMT activation. Our study thus uncovers a new molecular mechanism, by which the CRC cells display differences in resistance to chemotherapy and metastatic potential.
Project description:High tumor recurrence is frequently observed in patients with urinary bladder cancers (UBCs), with the need for biomarkers of prognosis and drug response. Chemoresistance and subsequent recurrence of cancers are driven by a subpopulation of tumor initiating cells, namely cancer stem-like cells (CSCs). However, the underlying molecular mechanism in chemotherapy-induced CSCs enrichment remains largely unclear. In this study, we found that during gemcitabine treatment lncRNA-Low Expression in Tumor (lncRNA-LET) was downregulated in chemoresistant UBC, accompanied with the enrichment of CSC population. Knockdown of lncRNA-LET increased UBC cell stemness, whereas forced expression of lncRNA-LET delayed gemcitabine-induced tumor recurrence. Furthermore, lncRNA-LET was directly repressed by gemcitabine treatment-induced overactivation of TGF?/SMAD signaling through SMAD binding element (SBE) in the lncRNA-LET promoter. Consequently, reduced lncRNA-LET increased the NF90 protein stability, which in turn repressed biogenesis of miR-145 and subsequently resulted in accumulation of CSCs evidenced by the elevated levels of stemness markers HMGA2 and KLF4. Treatment of gemcitabine resistant xenografts with LY2157299, a clinically relevant specific inhibitor of TGF?RI, sensitized them to gemcitabine and significantly reduced tumorigenecity in vivo. Notably, overexpression of TGF?1, combined with decreased levels of lncRNA-LET and miR-145 predicted poor prognosis in UBC patients. Collectively, we proved that the dysregulated lncRNA-LET/NF90/miR-145 axis by gemcitabine-induced TGF?1 promotes UBC chemoresistance through enhancing cancer cell stemness. The combined changes in TGF?1/lncRNA-LET/miR-145 provide novel molecular prognostic markers in UBC outcome. Therefore, targeting this axis could be a promising therapeutic approach in treating UBC patients.
Project description:Krüppel-like factor 4 (KLF4) was closely associated with epithelial-mesenchymal transition and stemness in colorectal cancer stem cells (CSCs)-enriched spheroid cells. Nonetheless, the underlying molecular mechanism is unclear. This study showed that KLF4 overexpression was accompanied with stemness and mesenchymal features in Lgr5<sup>+</sup> CD44<sup>+</sup> EpCAM<sup>+</sup> colorectal CSCs. KLF4 knockdown suppressed stemness, mesenchymal features and activation of the TGF-?1 pathway, whereas enforced KLF4 overexpression activated TGF-?1, phosphorylation of Smad 2/3 and Snail expression, and restored stemness and mesenchymal phenotypes. Furthermore, TGF-?1 pathway inhibition invalidated KLF4-facilitated stemness and mesenchymal features without affecting KLF4 expression. The data from the current study are the first to demonstrate that KLF4 maintains stemness and mesenchymal properties through the TGF-?1/Smad/Snail pathway in Lgr5<sup>+</sup> CD44<sup>+</sup> EpCAM<sup>+</sup> colorectal CSCs.
Project description:Long non-coding RNAs (lncRNAs) are involved in the pathology of various tumors, including colorectal cancer (CRC). The crosstalk between carcinoma- associated fibroblasts (CAFs) and cancer cells in the tumor microenvironment promotes tumor development and confers chemoresistance. In this study, we further investigated the underlying tumor-promoting roles of CAFs and the molecular mediators involved in these processes. <b>Methods:</b> The AOM/DSS-induced colitis-associated cancer (CAC) mouse model was established, and RNA sequencing was performed. Small interfering RNA (siRNA) sequences were used to knock down H19. Cell apoptosis was measured by flow cytometry. SW480 cells with H19 stably knocked down were used to establish a xenograft model. The indicated protein levels in xenograft tumor tissues were confirmed by immunohistochemistry assay, and cell apoptosis was analyzed by TUNEL apoptosis assay. RNA-FISH and immunofluorescence assays were performed to assess the expression of H19 in tumor stroma and cancer nests. The AldeRed ALDH detection assay was performed to detect intracellular aldehyde dehydrogenase (ALDH) enzyme activity. Isolated exosomes were identified by transmission electron microscopy, nanoparticle tracking and Western blotting. <b>Results:</b> H19 was highly expressed in the tumor tissues of CAC mice compared with the expression in normal colon tissues. The up-regulation of H19 was also confirmed in CRC patient samples at different tumor node metastasis (TNM) stages. Moreover, H19 was associated with the stemness of colorectal cancer stem cells (CSCs) in CRC specimens. H19 promoted the stemness of CSCs and increased the frequency of tumor-initiating cells. RNA-FISH showed higher expression of H19 in tumor stroma than in cancer nests. Of note, H19 was enriched in CAF-derived conditioned medium and exosomes, which in turn promoted the stemness of CSCs and the chemoresistance of CRC cells <i>in vitro</i> and <i>in vivo</i>. Furthermore, H19 activated the ?-catenin pathway via acting as a competing endogenous RNA sponge for miR-141 in CRC, while miR-141 significantly inhibited the stemness of CRC cells. <b>Conclusion:</b> CAFs promote the stemness and chemoresistance of CRC by transferring exosomal H19. H19 activated the ?-catenin pathway via acting as a competing endogenous RNA sponge for miR-141, while miR-141 inhibited the stemness of CRC cells. Our findings indicate that H19 expressed by CAFs of the colorectal tumor stroma contributes to tumor development and chemoresistance.
Project description:Tumors comprise cancer stem cells (CSCs) and their heterogeneous progeny within a stromal microenvironment. In response to transforming growth factor-? (TGF-?), epithelial and carcinoma cells undergo a partial or complete epithelial-mesenchymal transition (EMT), which contributes to cancer progression. This process is seen as reversible because cells revert to an epithelial phenotype upon TGF-? removal. However, we found that prolonged TGF-? exposure, mimicking the state of in vivo carcinomas, promotes stable EMT in mammary epithelial and carcinoma cells, in contrast to the reversible EMT induced by a shorter exposure. The stabilized EMT was accompanied by stably enhanced stem cell generation and anticancer drug resistance. Furthermore, prolonged TGF-? exposure enhanced mammalian target of rapamycin (mTOR) signaling. A bitopic mTOR inhibitor repressed CSC generation, anchorage independence, cell survival, and chemoresistance and efficiently inhibited tumorigenesis in mice. These results reveal a role for mTOR in the stabilization of stemness and drug resistance of breast cancer cells and position mTOR inhibition as a treatment strategy to target CSCs.
Project description:<h4>Background</h4>TP53 is one of the most frequently mutated genes among all cancer types, and TP53 mutants occur more than 60% in colorectal cancer (CRC). Among all mutants, there are three hot spots, including p53-R175H, p53-R248W and p53-R273H. Emerging evidence attributes cancer carcinogenesis to cancer stem cells (CSCs). Long noncoding RNAs (lncRNAs) play crucial roles in maintaining the stemness of CSCs. However, it is unknown if mutant p53-regulated lncRNAs are implicated in the maintenance of CSC stemness.<h4>Methods</h4>RNA-sequencing (RNA-seq) and ChIP-sequencing (ChIP-seq) were used to trace the lncRNA network regulated by p53-R273H in HCT116 endogenous p53 point mutant spheroid cells generated by the somatic cell knock-in method. RT-qPCR was used to detect lncRNA expression patterns, verifying the bioinformatics analysis. Transwell, spheroid formation, fluorescence activated cell sorter (FACS), xenograft nude mouse model, tumor frequency assessed by extreme limiting dilution analysis (ELDA), Western blot assays and chemoresistance analysis were performed to elucidate the functions and possible mechanism of lnc273-31 and lnc273-34 in cancer stem cells.<h4>Results</h4>p53-R273H exhibited more characteristics of CSC than p53-R175H and p53-R248W. RNA-seq profiling identified 37 up regulated and 4 down regulated differentially expressed lncRNAs regulated by p53-R273H. Combined with ChIP-seq profiling, we further verified two lncRNAs, named as lnc273-31 and lnc273-34, were essential in the maintenance of CSC stemness. Further investigation illustrated that lnc273-31 or lnc273-34 depletion dramatically diminished colorectal cancer migration, invasion, cancer stem cell self-renewal and chemoresistance in vitro. Moreover, the absence of lnc273-31 or lnc273-34 dramatically delayed cancer initiation and tumorigenic cell frequency in vivo. Also, lnc273-31 and lnc273-34 have an impact on epithelial-to mesenchymal transition (EMT). Finally, lnc273-31 and lnc273-34 were significantly highly expressed in CRC tissues with p53-R273H mutation compared to those with wildtype p53.<h4>Conclusions</h4>The present study unveiled a high-confidence set of lncRNAs regulated by p53-R273H specific in colorectal CSCs. Furthermore, we demonstrated that two of them, lnc273-31 and lnc273-34, were required for colorectal CSC self-renewal, tumor propagation and chemoresistance. Also, the expression of these two lncRNAs augmented in colorectal cancer patient samples with p53-R273H mutation. These two lncRNAs may serve as promising predictors for patients with p53-R273H mutation and are vital for chemotherapy.
Project description:Ovarian cancer stem cells (OCSCs) are sources of tumor chemoresistance and recurrence. A hypoxic microenvironment contributes to the chemoresistance of cancer stem cells (CSCs), but the underlying mechanism is not fully understood yet. Here, we show that increased HIF-2? expression is associated with enhanced stemness of OCSCs and poor outcomes in ovarian cancer patients. OVCAR-3 and CAOV-3 sphere-forming (OVCAR-3 S and CAOV-3 S) cells with OCSC-like properties showed strong resistance to adriamycin (ADR). Hypoxia (1% O2 ) induced high expression of both HIF-1? and especially HIF-2?, and increased the resistance of OVCAR-3 S and CAOV-3 S cells to ADR. Notably, treatment with ADR further increased the expression of HIF-2?, but not that of HIF-1?. Knockdown of HIF-2? expression substantially attenuated the resistance of OVCAR-3 S and CAOV-3 S cells to ADR, and the HIF-2? overexpression had the opposite effect. Furthermore, in mouse models xenografted with OCSCs, HIF-2? depletion significantly inhibited tumor growth and sensitized OCSCs to ADR in vivo. Mechanistically, HIF-2? directly promotes transcription/expression of BCRP, a gene encoding a transporter protein responsible for pumping drugs (e.g., ADR) out of cells, which in turn increases drug resistance due to increased drug transportation. Collectively, our studies reveal a novel drug-resistant mechanism in ovarian cancer by which hypoxia (and ADR treatment)-induced HIF-2? overexpression endows OCSCs with resistance to ADR by promoting BCRP expression and ADR transportation. Therefore, targeting the HIF-2?/BCRP axis holds therapeutic potential for treating drug-resistant ovarian cancer.
Project description:Cancer stem cells (CSCs) are critical for cancer progression and chemoresistance. How lipid metabolism regulates CSCs and chemoresistance remains elusive. Here, we demonstrate that JAK/STAT3 regulates lipid metabolism, which promotes breast CSCs (BCSCs) and cancer chemoresistance. Inhibiting JAK/STAT3 blocks BCSC self-renewal and expression of diverse lipid metabolic genes, including carnitine palmitoyltransferase 1B (CPT1B), which encodes the critical enzyme for fatty acid ?-oxidation (FAO). Moreover, mammary-adipocyte-derived leptin upregulates STAT3-induced CPT1B expression and FAO activity in BCSCs. Human breast-cancer-derived data suggest that the STAT3-CPT1B-FAO pathway promotes cancer cell stemness and chemoresistance. Blocking FAO and/or leptin re-sensitizes them to chemotherapy and inhibits BCSCs in mouse breast tumors in vivo. We identify a critical pathway for BCSC maintenance and breast cancer chemoresistance.