m6A Methyltransferase METTL14-Mediated Upregulation of Cytidine Deaminase Promoting Gemcitabine Resistance in Pancreatic Cancer

Abstract

ObjectivePancreatic cancer is one of the most lethal human malignancies. Gemcitabine is widely used to treat pancreatic cancer, and the resistance to chemotherapy is the major difficulty in treating the disease. N6-methyladenosine (m6A) modification, which regulates RNA splicing, stability, translocation, and translation, plays critical roles in cancer physiological and pathological processes. METTL14, an m6A Lmethyltransferase, was found deregulated in multiple cancer types. However, its role in gemcitabine resistance in pancreatic cancer remains elusive.MethodsThe mRNA and protein level of m6A modification associated genes were assessed by QRT-PCR and western blotting. Then, gemcitabine‐resistant pancreatic cancer cells were established. The growth of pancreatic cancer cells were analyzed using CCK8 assay and colony formation assay. METTL14 was depleted by using shRNA. The binding of p65 on METTL14 promoter was assessed by chromatin immunoprecipitation (ChIP) assay. Protein level of deoxycytidine kinase (DCK) and cytidine deaminase (CDA) was evaluated by western blotting. In vivo experiments were conducted to further confirm the critical role of METTL14 in gemcitabine resistance.ResultsWe found that gemcitabine treatment significantly increased the expression of m6A methyltransferase METTL14, and METTL14 was up-regulated in gemcitabine-resistance human pancreatic cancer cells. Suppression of METTL14 obviously increased the sensitivity of gemcitabine in resistant cells. Moreover, we identified that transcriptional factor p65 targeted the promoter region of METTL14 and up-regulated its expression, which then increased the expression of cytidine deaminase (CDA), an enzyme inactivates gemcitabine. Furthermore, in vivo experiment showed that depletion of METTL14 rescue the response of resistance cell to gemcitabine in a xenograft model.ConclusionOur study suggested that METTL14 is a potential target for chemotherapy resistance in pancreatic cancer.

Functions, mechanisms, and therapeutic implications of METTL14 in human cancer

“…In the treatment of AML, all-trans retinoic acid/arsenic trioxide (ATO) [ 152 ], differentiation inducers (OP9 medium) [ 153 ], PMA [ 154 ], and all-trans retinoic acid (ATRA) [ 155 ] have been reported to significantly reduce m 6 A levels and the expression of METTL14, thereby promoting myeloid differentiation and inhibiting leukemia growth [ 156 ]. In pancreatic cancer, knockout of METTL14 enhances the sensitivity of cancer cells to cisplatin by inducing apoptosis and autophagy through the mTOR signaling pathway [ 157 ] and inhibits the expression of cytidine deaminase (CDA), improving the sensitivity of drug-resistant cells to gemcitabine [ 158 ]. These studies demonstrate the importance of METTL14 inhibitors in the treatment of tumors.…”

Insights into roles of METTL14 in tumors

“…In gemcitabine‐resistant pancreatic cancer cells, METTL14 is regulated by P65, a transcriptional factor binding to METTL14 promoter region, and elevates the transcript stability of CDA, which causes gemcitabine inactivation, and ultimately developments gemcitabine resistance of pancreatic cancer cells in vitro and in vivo. 48 These results suggest that METTL14 may possess feasibility in treating chemotherapy‐resistant pancreatic cancer.…”

“…Upregulated METTL14 hampers the attenuation of cytidine deaminase (CDA) transcript, enhances its stability, and induces chemotherapy resistance of pancreatic cancer cells. 48 Non‐coding RNAs (ncRNAs) also play a role in regulation of METTL14 expression. In breast cancer, the stability and expression of METTL14 are positively regulated by LNC942, which elevates the m6A content in downstream targets CXCR4 and CYP1B1, stabilizes protein expression and translation, and further promotes tumorigenesis.…”

Alcohol-induced C/EBP β-driven KIAA1429 decreases oxidative stress and promotes pancreatic cancer growth and metastasis via the m6A/YTHDF2/SLC43A2 pathway

“…1A-E). Previous studies have demonstrated that METTL14 promotes PC progression [16,17] and chemoresistance [18,19]. Several studies have implicated KIAA1429 in the regulation of multiple tumors [9,10,[20][21][22]; however, the role of KIAA1429 in PC is unclear.…”