PTENP1 and gastric cancer: Fer-1-like family member 4 (pseudogene) (FER1L4), cancer upregulated drug-resistant (CUDR) gene, long stress-induced noncoding transcript 5 (LSINCT-5), and phosphatase and tensin homolog pseudogene 1 (PTENP1) are the main downregulated circulating lncRNAs in GC [56].