Long intergenic non-protein coding RNA 1273 confers sorafenib resistance in hepatocellular carcinoma via regulation of methyltransferase 3

Hepatocellular carcinoma (HCC) is often diagnosed in patients with advanced disease who are ineligible for curative surgical therapies. Sorafenib is a first-line agent approved for the treatment of advanced HCC. However, the frequent resistance of HCC cells to sorafenib greatly reduces its efficacy. Herein, we describe a novel long non-coding RNA (lncRNA) conferring sorafenib resistance. Long intergenic non-protein coding RNA 1273 (LINC01273) was significantly overexpressed in human HCC and sorafenib-resistant tissues, linking it to poor overall and relapse-free survival. We established sorafenib-resistant Huh7 (Huh7-SR) and SMMC-7721 (SMMC-7721-SR) cells, and found that the knockdown of LINC01273 repressed the viability, colony formation, and DNA synthesis rate of Huh7-SR and SMMC-7721-SR cells. The level of N6-methyladenosine (m(6)A) in sorafenib-resistant HCC cells was significantly decreased, which was rescued by LINC01273 silencing. Mechanistically, LINC01273 complementarity bound to miR-600, served as a ‘reservoir’ increasing miR-600 stability, and facilitating miR-600 targeting methyltransferase 3 (METTL3), a m(6)A ‘writer’, resulting in reducing METTL3 level. In addition, LINC01273 was modified with m(6)A, METTL3 increased LINC01273 m(6)A modification, followed by LINC01273 decay in the presence of YTHDF2, a m(6)A ‘reader’. Our findings reveal the key role of LINC01273 in sorafenib-resistant HCC cells, and targeting of the newly identified LINC01273/miR-600/METTL3 feedback regulatory axis may be a promising effective intervention for HCC patients with sorafenib resistance.