R-2HG downregulates ERα to inhibit cholangiocarcinoma via the FTO/m6A-methylated ERα/miR16-5p/YAP1 signal pathway

Isocitrate dehydrogenase (IDH) mutations increase (R)-2-hy-droxyglutarate (R-2HG) production; however, functional mechanisms of R-2HG in regulating cholangiocarcinoma (CCA) development remain to be further investigated. We first applied the CRISPR-Cas9 gene-editing system to create IDH1R132H-mutated CCA cells. Interestingly, our data showed that R-2HG could function through downregulating estrogen receptor alpha (ER alpha) and Yes-associated protein 1 (YAP1) pathways to decrease CCA growth. Detailed mechanistic studies revealed that R-2HG could target and degrade the fat mass and obesity-associated protein (FTO), the first identified mRNA demethylase. This reduced FTO can increase the N-6-methyladenosine (m6A) to methylate the mRNA of ER alpha, and consequently decrease protein translation of the ER alpha. Further mechanistic studies revealed that ER alpha could transcriptionally suppress miR-16-5p expression, which could then increase YAP1 expression due to the reduced miR-16-5p binding to the 30 UTR of YAP1. Furthermore, data from the pre-clinical animal model with implantation of IDH1R132H QBC939 cells demonstrated that R-2HG generated by the IDH1 mutation could downregulate ER alpha and YAP1 to suppress CCA tumor growth. Taken together, our new findings suggested that IDH1 mutation-induced R-2HG could suppress CCA growth via regulating the FTO/m6A-methylated ER alpha/miR16-5p/YAP1 signaling pathway. Upregulating R-2HG or downregulating the ER alpha signal by short hairpin RNA ERa (shER alpha) or antiestrogen could be effective strategies to inhibit CCA.

Automated summary

Mutations in Isocitrate dehydrogenase (IDH) increase production of (R)-2-hy-droxyglutarate (R-2HG), which has been shown to suppress cholangiocarcinoma (CCA) growth by regulating the FTO/m6A-methylated ER alpha/miR16-5p/YAP1 signaling pathway. Upregulating R-2HG or downregulating ER alpha may be effective strategies to inhibit CCA.