PTGDR and gastric cancer: LncRNAs regulate cell cycle in gastric cancer cells by epigenetically silencing several cyclin-dependent protein kinase inhibitors (CKIs), including p15, p16, p21, p27 and p57. LncRNAs, such as PVT1 (Plasmacytoma variant translocation 1), LINC00668, LINC00152, TUG1 and FEZF1-AS1, contribute to cell cycle progression in GC cells (Figure 3).