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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.

SUBMITTER: Tang YA

PROVIDER: S-EPMC6042102 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Hypoxic tumor microenvironment activates GLI2 via HIF-1α and TGF-β2 to promote chemoresistance in colorectal cancer.

Tang Yen-An YA Chen Yu-Feng YF Bao Yi Y Mahara Sylvia S Yatim Siti Maryam J M SMJM Oguz Gokce G Lee Puay Leng PL Feng Min M Cai Yu Y Tan Ern Yu EY Fong Sau Shung SS Yang Zi-Huan ZH Lan Ping P Wu Xiao-Jian XJ Yu Qiang Q

Proceedings of the National Academy of Sciences of the United States of America 20180611 26

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-1α) and cancer-associated fibroblasts (CAFs)-secreted TGF-β2 converge to activate the expression of hedgehog transcrip ...[more]

PMID: 29891662

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Project description:The aim of the present study was to explore the effects of BRAF-activated non-protein coding RNA (BANCR) on pancreatic microlymphangiogenesis in pancreatic cancer (PC) and its molecular mechanism under hypoxic conditions. Reverse transcription-quantitative PCR (RT-qPCR) was used to detect the expression of BANCR in SW1990 and PANC-1 PC cell lines under normoxic and hypoxic conditions. Subsequently, the expression of BANCR in the PC cells was knocked down using small interfering RNAs (siRNAs). Western blotting and RT-qPCR analyses were performed to detect the expression of hypoxia-inducible factor (HIF-1α), VEGF-C and VEGFR-3 in the transfected cells. In addition, the transfected PC cells were co-cultured with human lymphatic endothelial cells and the lymphatic microvessel density (MLVD) was detected under normal and hypoxic conditions. Furthermore, HIF-1α expression in the PC cells was knocked down using siRNAs, and VEGF-C and VEGFR-3 mRNA expression in the HIF-1α knockdown cells was detected using RT-qPCR. The results showed that the expression of BANCR in the SW1990 and PANC-1 PC cell lines was significantly higher than that in human pancreatic duct endothelial cells. Additionally, the expression of BANCR was significantly increased in PC cells under hypoxic conditions compared with normoxic conditions. The MLVD of PC cells under hypoxic conditions was significantly higher compared with that under normoxic conditions, and the MLVD in the si-BANCR group was lower than that in the si-NC group, indicating that si-BANCR downregulated MLVD. These results indicate that BANCR positively regulated the expression of HIF-1α in PC cells at the transcriptional and translational levels. Finally, the expression levels of VEGF-C and VEGFR-3 in PC cells were significantly reduced when BANCR or HIF-1α expression was knocked down. In conclusion, the results demonstrate that the expression of BANCR in PC cells was significantly increased under hypoxic conditions and suggest that BANCR promoted tumor cell lymphangiogenesis by upregulating the HIF-1α/VEGF-C/VEGFR-3 pathway, which plays an important role in the process of PC lymph node metastasis.

Dataset Information

Hypoxic tumor microenvironment activates GLI2 via HIF-1? and TGF-?2 to promote chemoresistance in colorectal cancer.

Publications

Hypoxic tumor microenvironment activates GLI2 via HIF-1α and TGF-β2 to promote chemoresistance in colorectal cancer.

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