Mechanisms of the In Vivo Antitumor Activity of Polyalthia longifolia Leaf Extract Against HeLa Cell Xenograft Tumor: A Microscopic-Based Histological and Immunohistochemical Microanalyses

The present study investigated the effects of Polyalthia longifolia leaf extract against the growth of HeLa cell xenograft tumor in nude mice and its underlying mechanism. The nude mice xenografted with HeLa cells were treated with 5% DMSO (vehicle control), 20 mg/kg/body weight of etoposide (positive control), and 500 and 1000 mg/kg/body weight of leaf extract, respectively. Antitumor activity was evaluated with apoptosis, proliferation, and angiogenesis using microscopic-based histological and immunohistochemical microanalyses. The tumor tissue histological and immunohistochemical analyses showed that the HeLa tumor cell death was associated with apoptosis and decreased (p < 0.05) expression of Ki-67 in tumor tissues. The extract also inhibits tumor angiogenesis by downregulating (p < 0.05) the expression of VEGF and CD31 in tumor tissues after treatment for 35 days. Conclusively, the P. longifolia leaf extract effectively inhibited HeLa cell xenograft growth in nude mice. The possible mechanism was related to induction of apoptosis, inhibition of tumor HeLa cell proliferation by decreasing the Ki-67 protein expression, and prevention of tumor angiogenesis by reducing VEGF and CD31 protein expression in HeLa cells.