PTEN and gastric cancer: LncRNA growth arrest-specific transcript 5 (GAS5) belongs to the GAS family, and acts as a tumor suppressor in gastric cancer, hepatocellular carcinoma, renal cell carcinoma and many other tumors by interacting with p53, phosphatase and tensin homolog (PTEN), E2F transcription factor 1 and mechanistic target of rapamycin complex 1 (mTORC1) [114,115,116,117].