Inhibitory effect of ophiopogonin B on tumor growth in gastric tumor-bearing rats by regulating Rho A/ROCK1 signaling pathway

Objective To investigate the effect of ophiopogonin B (OP-B) on tumor growth in gastric tumor-bearing rats and its underlying mechanism. Methods Sixty-six SPF SD rats (half male and female, 6 weeks old, 180~200 g) were randomly divided into model group, low-, medium- and high-dose OP-B groups, and activator group, with 10 rats in each group. The gastric tumor-bearing model was established by orthotopic transplantation of Walker-256 tumor tissue. The rats in the 3 doses groups were given 17.5, 35 and 70 mg/kg OP-B, respectively, by gavage and intraperitoneal injection of the same amount of normal saline, and the rats in the activator group were intragastrically administered with 70 mg/kg OP-B and intraperitoneally injected with 1 mg/kg Rho A/ROCK1 signaling pathway activator, lysophosphatidic acid (LPA). The weight and volume of transplanted tumor were recorded to calculate the tumor inhibitory rate. The morphology of tumor tissue was observed with HE staining. The apoptosis of tumor cells were detected by TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining. The expression of proliferating cell nuclear antigen 67 (Ki-67) and cleavage cysteine aspartic acid proteolytic enzyme-3 (Cleaved Caspase-3) in tumor tissues were detected by immunohistochemical staining. RT-qPCR and Western blotting were utilized to measure the expression of Ras homologous gene family member A (Rho A) and Rho-associated coiled-coil forming protein kinase1(ROCK1) at mRNA and protein levels. Results Compared with the model group, the tumor weight and volume, mRNA and protein levels of Ki-67, Rho A and ROCK1 were significantly decreased, and the tumor inhibitory rate, tumor cell apoptotic rate and Cleaved Caspase-3 protein level were obviously increased in the low-, medium- and high-dose OP-B groups (P < 0.05). The activator group had heavier tumor weight and larger volume, increased mRNA and protein expression levels of Ki-67, Rho A and ROCK1, and lower tumor inhibitory rate and apoptotic rate and reduced Cleaved Caspase-3 expression when compared with the high-dose OP-B group (P < 0.05). Conclusion OP-B may suppress the tumor growth of gastric tumor-bearing rats by inhibiting the activation of Rho A/ROCK1 signaling pathway.