Targeting PTBP1 blocks glutamine metabolism to improve the cisplatin sensitivity of hepatocarcinoma cells through modulating the mRNA stability of glutaminase

Abstract

Hepatocellular carcinoma (HCC) is a frequently diagnosed malignancy with a high mortality rate. Cisplatin (CDDP) is a widely applied anti-cancer drug. However, a large population of liver cancer patients developed CDDP resistance. The polypyrimidine tract binding protein (PTBP1) is an RNA-binding protein involving in progressions of diverse cancers. Here we report PTBP1 was significantly upregulated in liver tumors and cell lines. Silencing PTBP1 effectively sensitized HCC cells to CDDP. From the established CDDP-resistant HCC cell line (HepG2 CDDP Res), we observed that CDDP-resistant cells were more sensitive to CDDP under low glutamine supply compared with that in HCC parental cells. CDDP-resistant HCC cells displayed elevated glutamine metabolism rate. Consistently, PTBP1 promotes glutamine uptake and the glutamine metabolism key enzyme, glutaminase (GLS) expression. Bioinformatics analysis predicted that the 3′-UTR of GLS mRNA contained PTBP1 binding motifs which were further validated by RNA immunoprecipitation and RNA pull-down assays. PTBP1 associated with GLS 3′-UTR to stabilize GLS mRNA in HCC cells. Finally, we demonstrated that the PTBP1-promoted CDDP resistance of HCC cells was through modulating the GLS–glutamine metabolism axis. Summarily, our findings uncovered a PTBP1-mediated CDDP resistance pathway in HCC, suggesting that PTBP1 is a promisingly therapeutic target to overcome chemoresistance of HCC.

Keywords

• hepatocellular carcinoma
• ptbp1
• rna-binding protein
• glutamine metabolism
• glutaminase
• chemosensitivity
• cddp resistance