PGP and gastric cancer: In addition, miR-19a/b (23), miR-508-5p (34), miR-30a (35), miR-21 (36) and miR-361-3p (37) have also been proved to increase the excretion of chemotherapy drugs by regulating the expression of P-gp on the membranes of GC cells, resulting in decreased sensitivity to chemotherapy.