ObjectiveTo explore the mechanism by which the tumor suppressor gene Testin affects the proliferation, migration, and invasive biological activity of lung adenocarcinoma cell lines by regulating the RhoA pathway. MethodThe cbioportal tumor gene expression was used to screen for genes with high correlation with TES gene expression in lung adenocarcinoma, and the 200 genes with the highest correlation were selected for pathway enrichment analysis. Upload these 200 genes to the David gene annotation tool for GO_Biological Process pathway analysis, GO Molecular Function pathway analysis, KEGG pathway analysis, and Reactome pathway analysis. The lung adenocarcinoma cell line H1299 was cultured, and an overexpression Testin plasmid was constructed and transfected into H1299 cells. The mRNA and protein expression of RhoA, Rac1, and Cdc42 were detected using qRT PCR and western blot. On the basis of downregulating RhoA expression through overexpression of Testin, the overexpression plasmid of RhoA (TES+RhoA) was transfected simultaneously to induce a downregulation of RhoA expression, and the changes in malignant phenotype of lung adenocarcinoma cells were detected. The biological activity changes of adenocarcinoma cell lines after the above intervention were verified through CCK-8 experiment, Transwell experiment, and Matrigel experiment. Results The results of pathway analysis prediction showed that Testin may be involved in regulating the Rho GTPase signaling pathway. Overexpression of Testin did not affect the mRNA levels of RhoA, Rac1, and Cdc42 (all P>0.05), nor did it affect the protein expression levels of Rac1 and Cdc42 (all P>0.05), but it significantly reduced the protein level of RhoA (P<0.05). Knocking down RhoA in lung adenocarcinoma cell H1299 can significantly inhibit cell proliferation, migration, and invasion ability (all P<0.05). Simultaneously transfecting RhoA overexpression plasmid on the basis of overexpression of Testin can downregulate RhoA expression, but does not affect Testin expression. ConclusionsRhoA plays a pro-cancer role in lung adenocarcinoma, and Testin can inhibit RhoA expression. Overexpression of RhoA can rescue Testin's effect on lung adenocarcinoma cell proliferation, migration, and invasion. Testin exerts its anti-cancer biological activity by regulating RhoA.