PIK3R1 and gastric cancer: Conversely, miR-21 was transferred from alternatively activated macrophages to gastric cancer cells through exosomes and inhibited the apoptosis of gastric cancer cells by regulating PTEN/phosphoinositide-3-kinase regulatory subunit 1 (Pik3r1, also known as PI3K)/Akt signaling and anti-apoptotic Bcl2 expression, leading to aggravated tumor growth [151].