Oral administration of an estrogen metabolite-induced potentiation of radiation antitumor effects in presence of wild-type p53 in non-small-cell lung cancer

Purpose: The purpose of this study was to investigate the efficacy of 2-methosyestradiol as an antitumor and radiosensitizing agent for the treatment of human malignancy. Methods and Materials: Two cancer cell lines with wild-type p53 status were exposed first to irradiation and then to an oral formulation of the nontoxic metabolite 2-methoxyestradiol (2ME) to stabilize p53 levels. Results: Cell growth was inhibited via G1 growth and apoptosis, Subsequent irt vitro growth and Tunel assays indicated that this combination was superior to radiation alone at inducing p53 protein accumulation, stabilizing p53 protein levels, and substantially reducing long-term tumor cell growth (similar to 80%) and colony formation (similar to 95%) in vitro, and inducing apoptosis, However, harboring mutated p53, H322 cell line, was relatively insensitive to such a treatment regimen, Western blot analysis revealed that growth inhibition was associated with increased levels of p53 and p21 protein accumulation. Experiments with subcutaneous tumor in a nu/nu mouse showed the combination treatment to be superior to radiation alone at reducing tumor growth (similar to 50% reduction as compared to radiation alone) in vivo. Conclusion: Thus, our studies confirmed a unique strategy whereby oral administration of a nontoxic estrogen metabolite, 2ME, significantly enhanced the radiation effect on a subcutaneous tumor without any toxicity and suggesting that this strategy mag be clinically useful as an adjuvant therapy. (C) 2000 Elsevier Science Inc.