Pyruvate kinase M2 (PKM2) has been studied for decades on its role in cancer metabolism. Recently, PKM2 is highlighted again for its new function: promoting gene transcription by acting as a protein kinase. Moreover, the PKM2 levels in patient circulation have been used as a diagnostic marker for many types of cancers. However, it remains unclear whether PKM2 in blood circulation has any physiological or pathological function. In my dissertation, I demonstrate that PKM2 released from cancer cells facilitates tumor growth by promoting tumor angiogenesis. Our experiments show that PKM2 promotes endothelial cell proliferation, migration and survival. Only the dimeric PKM2, not the tetrameric PKM2 possesses the activity in angiogenesis promotion. Our results further indicate that PKM2 regulates angiogenesis by integrin αvβ3 activation and integrin redistribution. I also found that PKM2 enhances drug resistance of cancer cells expressing integrin αvβ3.