PVT1 and gastric cancer: lncRNA plasmacytoma variant translocation 1 (PVT1), encoded by the human PVT1 gene, is abnormally expressed in many tumors, and aberrantly altered expression of PVT1 has been closely associated with tumorigenesis in a variety of tumors, such as pancreatic, pulmonary, hepatocellular, cervical, and gastric cancer [9–13].