β-elemene Ameliorates Cisplatin Resistance of Gastric Cancer via Regulating Exosomal METTL3-m6A-ARF6 Axis.

The medial overall survival is low in patients with gastric cancer (GC) at advanced stage, in which drug resistance plays an important role. β-elemene has been established as the suppressed role on GC cell proliferation, however, the concrete mechanism of it remains unclear in cisplatin (DDP)-resistance GC. Cell counting kit-8 (CCK8) assay was used to measure the half maximal inhibitory concentration (IC) values of DDP in DDP-resistance GC cell lines. Cell apoptotic rates and invasive ability were tested by flow cytometry and transwell assay. Western blot and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) were utilized to detect the protein and mRNA levels of methyltransferase like-3 (METTL3) and ADP ribosylation factor 6 (ARF6). SRAMP websites and methylated RNA immunoprecipitation (MeRIP) assay were applied to predicted m6A sites and verified m6A levels of ARF6 respectively. RNA immunoprecipitation (RIP) was used to explore the interaction between these two molecules. Xenograft tumor models were constructed to demonstrate the effects of β-elemene in vivo. β-elemene improved drug sensitivity and curbed malignant cell activities of DDP-resistance GC cells in vitro. ARF6 was upregulated in DDP-resistance GC cells and tissues, and its overexpression could abrogate the effects on DDP-resistant GC cells mediated by β-elemene treatment. Intracellular and exosomal METLL3 expression were elevated in and from DDP-resistance GC cell lines. Exosomal METTL3 released from DDP-resistance GC cells could counteract the effects of β-elemene on DDP-resistance GC cells partly via regulating ARF6 expression in the m6A-dependent manner. β-elemene could suppress DDP-resistance tumor growth in vivo. In conclusion, β-elemene could repress tumor growth and drug resistance via exosomal METTL3-m6A-ARF6 axis.