AUTHOR=Yeon Minjeong , Kim Youngmi , Pathak Deepak , Kwon Eunju , Kim Dong Young , Jeong Myeong Seon , Jung Hyun Suk , Jeoung Dooil 

TITLE=The CAGE–MiR-181b-5p–S1PR1 Axis Regulates Anticancer Drug Resistance and Autophagy in Gastric Cancer Cells

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2021.666387

DOI=10.3389/fcell.2021.666387

ISSN=2296-634X

ABSTRACT=CAGE, a cancer/testis antigen, has been known to promote anti-cancer drug resistance. Since the underlying mechanisms of CAGE-promoted anti-cancer drug-resistance are poorly understood, we established anti-cancer drug-resistant gastric cancer cells to better elucidate possible mechanisms. Anti-cancer drug-resistant gastric cancer cells (AGSR) showed an increased expression level of CAGE and autophagic flux compared with anti-cancer drug-sensitive parental gastric cancer cells (AGS cells). AGSR cells showed higher invasion potential, growth rate, tumor spheroid formation, and angiogenic potential than AGS cells. CAGE exerted effects on the response to anti-cancer drugs and autophagic flux. CAGE was shown to bind to Beclin1, a mediator of autophagy. Overexpression of CAGE increased autophagic flux, invasion potential, but inhibited the cleavage of PARP in response to anti-cancer drugs in CAGE CRISPR-Cas9 cell lines. TargetScan analysis was utilized to predict binding of miR-302b-5p to the promoter sequences of CAGE and the results show that MiR-302b-5p directly regulated CAGE expression as illustrated by luciferase activity. MiR-302b-5p regulated autophagic flux and the response to anti-cancer drugs. CAGE was shown to bind the promoter sequences of miR-302b-5p. The culture medium of AGSR cells increased CAGE expression and autophagic flux in AGS cells. ImmunoEM showed CAGE was present in the exosomes of AGSR cells; exosomes of AGSR cells and human recombinant CAGE protein increased CAGE expression, autophagic flux, and resistance to anti-cancer drugs in AGS cells. MicroRNA array revealed miR-181b-5p as a potential negative regulator of CAGE. MiR-181b-5p inhibitor increased the expression of CAGE and autophagic flux in addition to preventing anti-cancer drugs from cleaving Poly (ADP-ribose) polymerase (PARP) in AGS cells. TargetScan analysis predicted sphingosine 1-phosphate receptor 1 (SIPR1) as a potential target for miR-181b-5p. CAGE showed binding to the promoter sequences S1PR1. The downregulation or inhibition of S1PR1 led to decreased autophagic flux, but enhanced the sensitivity to anti-cancer drugs in AGSR cells. This study presents a novel role of CAGE-miR-181b-5p-S1PR1 axis in anti-cancer drug resistance and autophagy.