Diosmetin inhibits tumor development and block tumor angiogenesis in skin cancer

Diosmetin is a natural flavonoid obtained from citrus fruits and some medicinal herbs. Previous studies have reported the anti-cancer activity of diosmetin in some types of tumors. However, it is still unclear whether diosmetin exerts anti-cancer effects, particularly anti-angiogenic effects, in skin cancer. In this study, we used B16F10 melanoma cells and human umbilical vein endothelial cells to investigate the inhibitory effect of diosmetin on cell proliferation, migration and tube formation in vitro. Rat aorta ring assays were performed to determine the effect of diosmetin on ECs sprouting ex vivo. Furthermore, a B16F10 mouse melanoma model was used to observe the effect of diosmetin on tumor growth, angiogenesis, and metastasis in vivo. Our results showed that diosmetin not only suppressed tumor cell proliferation and migration but also induced cell apoptosis via the caspase pathway in B16F10 cells, and potently inhibited tube formation and cell migration in HUVECs. Rat aorta ring assays showed that diosmetin attenuated the ECs sprouting. Moreover, the mouse melanoma model showed that diosmetin significantly delayed tumor growth by inhibiting tumor vessels sprouting and expansion during tumor progression. Notably, diosmetin induced the normalization of tumor vasculature through the downregulation of angiopoietin-2 and the improvement of pericyte coverage, leading to suppression of metastasis formation in lungs and lymph nodes. In conclusion, our results demonstrate that diosmetin suppresses tumor progression and metastasis by inducing tumor cell death and inhibiting tumor angiogenesis as well as normalizing the defective tumor vasculature, suggesting that diosmetin is a potential adjuvant chemotherapy agent.