Gene transfer of antisense hypoxia inducible factor-1 alpha enhances the therapeutic efficacy of cancer immunotherapy

Solid tumors meet their demands for nascent blood vessels and increased gly colysis, to combat hypoxia, by activating multiple genes involved in angiog enesis and glucose metabolism. Hypoxia inducible factor-1 (HIF-1) is a cons titutively expressed basic helix-loop-helix transcription factor, formed by the assembly of HIF-1 alpha and HIF-1 beta (Amt), that is stabilized in re sponse to hypoxia, and rapidly degraded under normoxic conditions. It activ ates the transcription of genes important for maintaining oxygen homeostasi s. Here, we demonstrate that engineered down-regulation of HIF-1 alpha by i ntratumoral gene transfer of an antisense HIF-1 alpha plasmid leads to the down-regulation of VEGF, and decreased tumor microvessel density. Antisense HIF-1 alpha monotherapy resulted in the complete and permanent rejection o f small (0.1 cm in diameter) EL-4 tumors, which is unusual for an anti-angi ogenic agent where transient suppression of tumor growth is the norm. It in duced NK cell-dependent rejection of tumors, but failed to stimulate system ic T cell-mediated anti-tumor immunity, and synergized with B7-1-mediated i mmunotherapy to cause the NK cell and CD8 T cell-dependent rejection of lar ger EL-4 tumors (0.4 cm in diameter) that were refractory to monotherapies. Mice cured of their tumors by combination therapy resisted a rechallenge w ith parental tumor cells, indicating systemic antitumor immunity had been a chieved. in summary, whilst intensive investigations are in progress to tar get the many HIF-1 effecters, the results herein indicate that blocking hyp oxia-inducible pathways and enhancing NK-mediated antitumor immunity by tar geting HIF-1 itself may be advantageous, especially when combined with canc er immunotherapy.