Synergistic anti-hepatoma effect of bufalin combined with sorafenib via mediating the tumor vascular microenvironment by targeting mTOR/VEGF signaling

Abstract

Sorafenib inhibits tumor growth primarily by inhibiting vessel formation, however, its efficacy requires improvement, therefore, the development of strategies which augment its antiangiogenic effect are of primary concern. Bufalin inhibits tumor cell proliferation and metastasis, and induces apoptosis. In our previous study, it was demonstrated that the antiangiogenic effect of sorafenib was improved by bufalin in human umbilical vein endothelial cells (HUVECs). However, whether bufalin synergizes with sorafenib by affecting the tumor vascular microenvironment remains to be elucidated. In the present study, it was found that hepatocellular carcinoma (HCC) cell proliferation was inhibited by either bufalin or sorafenib following incubation for 24 h, and the inhibition was enhanced upon treatment with a combination of the two. Conditioned medium (CM), comprising supernatant from HCC cells was collected from each of the treatment groups. The migration and tubule formation were suppressed the most in the combination-CM treated HUVECs. The secretion of vascular endothelial growth factor (VEGF) was decreased in HCC cells treated with the combination-CM, as determined by an angiogenesis array, enzyme-linked immunosorbent assay (ELISA) and western blot analysis. The inhibition of tube formation in HUVECs treated with the combination-CM was reversed by incubation with VEGF. The in vivo experiments demonstrated that subcutaneous HCC cell tumors from mice treated with the combination treatment expressed the lowest levels of VEGF, as evidenced by immunohistochemistry and ELISA. Additionally, the level of phosphorylated mechanistic target of rapamycin (mTOR) was reduced in HUVECs pretreated with the phosphoinositide 3-kinase inhibitor PI103. Furthermore, the migration of HCC cells and HUVEC tube formation were attenuated by PI103 pretreatment. In conclusion, the results revealed a synergistic anti-hepatoma effect of bufalin combined with sorafenib via affecting the tumor vascular microenvironment by targeting mTOR/VEGF signaling.

The Role of Angiogenesis in Hepatocellular Carcinoma

“…New agents or combinations of synergizing agents with differing or broader selectivity to inhibit a variety of angiogenic pathways, or targeting agents to specific populations with a sensitizing mutation may potentially overcome initial or acquired resistance to initial antiangiogenic inhibitor treatment. Some agents are already demonstrating encouraging results in the laboratory and clinic (13,36,43,(77)(78)(79).…”

New therapeutic aspects of steroidal cardiac glycosides: the anticancer properties of Huachansu and its main active constituent Bufalin

“…It not only provides oxygen and extra nutrient, maintains the high proliferation rate of cancer cells, but also promotes local and distant metastasis of malignant cells [62]. Bufalin had been reported to inhibit cancer cell migration and invasion in liver cancer and lung cancer cell lines by down-regulating vascular endothelial growth factor (VEGF), which plays a major role in tumor angiogenesis [46, 63, 64]. Anti-angiogenic drugs, such as Sorafenib, may be complicated by relatively easy-acquired drug resistance, rapid onset of relapse after discontinuation, and the potential for tumor metastasis.…”

“…A previous study revealed that Bufalin enhances the anti-angiogenic effect of Sorafenib via AKT/VEGF signaling [64]. The co-administration of Bufalin and Sorafenib provides a novel therapeutic option for patients with advanced HCC and is worthy for further in-depth investigations [63, 64].…”

Effect of CELSR3 on the Cell Cycle and Apoptosis of Hepatocellular Carcinoma Cells

“…International Publisher sorafenib has become the first-line treatment and made the long-term survival of patients possible to some extent. Even so, with the problems of disease progression, drug-resistance, and adverse drug reaction as the therapy progresses, the urgent need for a more potent novel, targeted drug to replace sorafenib remains an increasingly prominent issue [11][12][13][14][15].…”