Chemoresistance is a major obstacle to prolonging pancreatic ductal adenocarcinoma (PDAC) patient survival. TET1 is identified as the most important epigenetic modification enzyme that facilitates chemoresistance in cancers. However, the chemoresistance mechanism of TET1 in PDAC is unknown. This study aimed to determine the role of TET1 in the chemoresistance of PDAC. TET1-associated chemoresistance in PDAC was investigated in vitro and in vivo. The clinical significance of TET1 was analyzed in 228 PDAC patients by tissue microarray profiling. We identified that TET1 downregulation is caused by its promoter hypermethylation and correlates with poor survival in PDAC patients. In vitro and in vivo functional studies performed by silencing or overexpressing TET1 suggested that TET1 is able to suppress epithelial-mesenchymal transition (EMT) and sensitize PDAC cells to 5FU and gemcitabine. Then RNA-seq, whole genome bisulfite sequencing (WGBS) and ChIP-seq were used to explore the TET1-associated pathway, and showed that TET1 promotes the transcription of CHL1 by binding and demethylating the CHL1 promoter, which consequently inhibits the Hedgehog pathway. Additionally, inhibiting Hedgehog signaling by CHL1 overexpression or the Hedgehog pathway inhibitor, GDC-0449, reversed the chemoresistance induced by TET1 silencing. Regarding clinical significance, we found that high TET1 and high CHL1 expression predicted a better prognosis in resectable PDAC patients. In summary, we demonstrated that TET1 reverses chemoresistance in PDAC by downregulating the CHL1-associated Hedgehog signaling pathway. PDAC patients with a high expression levels of TET1 and CHL1 have a better prognosis.
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We thank Wei Jin and Long-Yun Ye for technical assistance.
This work was supported by grants from the National Science Foundation for Distinguished Young Scholars of China ; the National Natural Science Foundation of China [81871941, 81872366, 81827807, 81802675, 81702341, and 81802380]; the Outstanding Academic Leader Program of the “Technological Innovation Action Plan” in Shanghai Science and Technology Commission [18XD1401200]; Scientific Innovation Project of Shanghai Education Committee (2019-01-07-00-07-E00057) and the Young Talented Specialist Training Program of Shanghai. The funding agencies had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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Li, H., Jiang, W., Liu, X. et al. TET1 downregulates epithelial-mesenchymal transition and chemoresistance in PDAC by demethylating CHL1 to inhibit the Hedgehog signaling pathway. Oncogene 39, 5825–5838 (2020). https://doi.org/10.1038/s41388-020-01407-8