Methylxanthine derivatives promote autophagy in gastric cancer cells targeting PTEN.

Methylxanthine derivatives, such as caffeine and theophylline, enhance cell apoptosis and autophagy and reportedly induce the activity of phosphatase and tensin homologue (PTEN) and inhibit the mammalian target of rapamycin (mTOR). This study investigated the impacts of caffeine and theophylline on gastric cancer cell apoptosis and autophagy using a gastric cancer cell line (MGC-803) and a nude mouse model. Peritumoural and tumour tissues were collected from five patients diagnosed with gastric carcinoma who underwent laparoscopic radical gastrectomy at our hospital. Autophagy was suppressed in gastric cancer tumour tissue compared with peritumoural tissue. In vitro, both caffeine and theophylline effectively suppressed MGC-803 cell proliferation and migration and induced autophagy. To assess the involvement of PTEN in caffeine-mediated and theophylline-mediated gastric cancer cell death, we transiently transfected MGC-803 cells with an siRNA targeting PTEN. PTEN knockdown impaired the methylxanthine derivative-mediated inhibition of PI3K/Akt/mTOR signalling. In nude mice treated with caffeine or theophylline, MGC-803 cell tumours injected with siPTEN were larger than those injected with negative control siRNA. These results show that the methylxanthine derivatives (caffeine and theophylline) effectively induce gastric cancer cell apoptosis and autophagy by PTEN activation and PI3K/Akt/mTOR pathway suppression and strongly support the use of methylxanthine derivatives as potential anticancer therapeutics.