The Prognostic Significance Of Hypoxia Inducible Factor-2 Alpha In Primary Breast Cancer

22081 Background: We investigated the relationship between the two hypoxia-inducible-factor-α (HIF-α) subunits in invasive breast cancer in vivo and their specific correlations to clinicopathological parameters, survival, and VEGF expression. Methods: We first conducted immunohistochemical analyses of HIF-1α, HIF-2α, and VEGF expression in tissue microarrays with tumours from 512 consecutive breast cancer patients with long-term follow-up. HIF-1α and HIF-2α and their impact on survival were then verified in another cohort of 179 patients. HIF-α protein andHIF-αand VEGFmRNA levels after hypoxic induction and knock-down experiments in cultured breast cancer cell lines were studied by Western blot and Q-PCR techniques. Results: We found no correlation between HIF-1α and HIF-2α expression and HIF-α subtype specific correlations to clinicopathological parameters and VEGF. HIF-2α was an independent prognostic factor whereas HIF-1α exhibited variable, non-significant correlation to survival. Culture for 4 or 24 hours at 21%, 5%, and 1% oxygen levels resulted in varying HIF- α protein levels, thereby verifying hypoxia level and time dependent induction of HIF-1α and HIF-2α. Knock-down experiments showed a subtype specific, time dependent utilization of the two transcription factors in hypoxia induced VEGF expression. Conclusions: Our in vitro and in vivo results show evidence for differential regulation and utilization of the two HIF- α subunits and that high protein expression associates to adverse outcome and distant metastasis in breast cancer. No significant financial relationships to disclose.