HIF1A and neoplasm: Bortezomib (PS-341) is a proteasome inhibitor that inhibits HIF-1α activity by inhibiting the recruitment of P300 coactivators.461 A phase II trial showed that Bortezomib is ineffective in metastatic colon cancer but alters tumor response to hypoxia.462 The in vivo experiments of xenograft-bearing mice showed that bortezomib strongly inhibits VEGF production by up to 90%.