BLU enhances the effects of anti-angiogenic activity in combination with gemcitabine-based chemotherapeutic agents

BLU is a tumor suppressor protein that is down-regulated in ovarian and cervical cancers. Its cellular biological functions appear related to cancer inhibition. We presently demonstrate that BLU has direct anti-tumor and anti-angiogenic effects on ovarian carcinoma and human umbilical vein endothelial cells in vitro by the arrest of the cell cycle and induction of apoptosis. BLU in combination with gemcitabine arrested the cell cycle at the G1-G0 phase and induced apoptosis. BLU actively contributed to cell growth by enhancing gemcitabine-inhibited cell migration and tubule formation in angiogenesis and tumorigenesis. The combined treatment with BLU and gemcitabine further activated p53 and p21 expression, whereas the productions of Bcl-2, Bcl-xL, and nuclear factor-kappa B proteins were decreased, with BLU possibly being more effective in the treatment of ovarian cancer when given in combination with gemcitabine, rather than as a single agent. Furthermore, as expected, BLU plus gemcitabine significantly inhibited the phosphorylation of signaling modulators downstream of phosphoinositide 3-kinase, such as phospho-phosphoinositide-dependent protein kinase 1, Akt, and mammalian target of rapamycin, as well as hypoxia-inducible factor-1α and vascular endothelial growth factor. Taken together, our results provide evidence that BLU can effectively regulate the pro-apoptotic and anti-angiogenic activity of gemcitabine through the direct interaction with vascular endothelial growth factor receptor-2, as well as the up-regulation of p21 and p53 expression.