After subcutaneous injection of Lewis lung carcinoma (LLC) or B16-BL6 melanoma tumors, Pik3c2a endothelial-restricted knock-out mice had reduced tumor volumes/weights compared to control, suggesting that the in vivo pro-angiogenetic function of PI3K-C2α is required for tumor growth and maintenance. The gene discussed is PIK3CA; the disease is neoplasm.