Hypoxia inducible factor (HIF-1a and HIF-2a) expression in early esophageal cancer and response to photodynamic therapy and radiotherapy

Hypoxia inducible factor 1a and 2a (HIF-1a and HIF-2a) are key proteins reg ulating cellular response to hypoxia, Because the efficacy of photodynamic therapy (PDT) is dependent on the presence of oxygen, the assessment of HIF -1a and HIF-2a expression may be of value in predicting clinical response t o PDT, Using recently produced MoAbs, we examined the expression of HIF1a a nd HIF2a in a series of 37 early-stage esophageal cancers treated with PDT and with additional radiotherapy in case of incomplete response after PDT, Strong expression of the HIF1a and of HIF2a proteins in all optical fields examined was noted in 51% and in 13% of cases, respectively. High expressio n was associated with a low complete response (CR) rate and with the absenc e of bcl-2, protein expression, On the contrary, bcl-2 expression was assoc iated with a high CR rate. Combined analysis of HIF1a and bcl-2 protein exp ression revealed that of 16 cases with high HIF1a expression and the absenc e of bcl-2 reactivity, only 1 (7%) responded completely to PDT (P = 0.007). Bivariate analysis showed that HIF1a expression was independently related to response to PDT (P = 0.04; t ratio = 2.8), whereas bcl-2 approached sign ificance (P = 0.07; t-ratio = 1.8). The final response to radiotherapy was high (70%) and independent of the HIF1a and bcl-2 status, which may be a re sult of reoxygenation after cellular depletion mediated by PDT, The present study suggests that assessment of HIF and of bcl-2 expression are importan t predictors of in vivo sensitivity to PDT, Modulation of PDT response with bioreductive drugs and/or drugs targeting bcl-2 (i.e,, taxanes) may prove of significant therapeutic importance in a subgroup of patients with high H IF expression.