pPe <italic>O</italic>p inhibits HGC-27 cell proliferation, migration and invasion by upregulating miR-30b-5p and down-regulating the Rac1/Cdc42 pathway

Gastric cancer is the fifth most frequently occurring and the fourth most lethal malignant cancer worldwide. A bioactive protein (pPe <i>O</i>p) from <i>Omphalia lapidescens</i> exhibits significant inhibitory effects on gastric cancer cells. miRNA deep sequencing analysis shows that miR-30b-5p is significantly upregulated in HGC-27 cells treated with pPe <i>O</i>p. Verification results show that the expression level of miR-30b-5p is significantly increased in HGC-27 cells after pPe <i>O</i>p treatment. Additionally, miR-30b-5p is significantly downregulated in clinical gastric cancer tissues compared to that in adjacent normal tissues. Following pPe <i>O</i>p treatment and/or transfection with miR-30b-5p mimic, the proliferation, migration, and invasion of HGC-27 cells are significantly impaired. Immunofluorescence microscopy shows that pPe <i>O</i>p and/or miR-30b-5p destroy(s) microfilaments and microstructures and inhibit(s) the formation of pseudopodia. Bioinformatics analysis, dual-luciferase reporter assay, and western blot analysis confirm that miR-30b-5p downregulates Rac1/Cdc42 expression and activation by targeting RAB22A. Available data indicate that miR-30b-5p plays an anti-gastric cancer role in mediating pPe <i>O</i>p. pPe <i>O</i>p upregulates miR-30b-5p expression, which in turn inhibits RAB22A expression, resulting in a reduction in the expression and activation of Rac1 and Cdc42 and their downstream targets, thus destroying the cytoskeletal structure and inhibiting the proliferation, migration, and invasion of cancer cells.