Immunohistochemical features of post-radiation vaginal recurrences of endometrioid carcinomas of the endometrium: role for proteins involved in resistance to apoptosis and hypoxia

Aims: Endometrioid carcinoma of the endometrium (EEC) is treated with surgery and radiotherapy. Postradiation recurrences are associated with increased risk of metastases. Comparison of the expression of genes important in the development and progression of EEC, and others involved in resistance to apoptosis and hypoxia and adaptation to radiation, was performed between post-radiation vaginal recurrences (PVRs) and primary EECs. We tried to reproduce the results by exposing an EEC cell line to hypoxia and radiation. Methods and results: Immunohistochemistry and tissue microarrays were used to compare 24 PVRs with 82 primary EECs. PVRs exhibited increased expression of p53 (P < 0.0001), cytoplasmic FLICE-inhibitory protein (FLIP) (P < 0.0001), and Ki67 (P < 0.0001), and nuclear staining for FLIP, nuclear factor kappaB (NF-kappa B) family members (p50, P < 0.0001; c-Rel, P = 0.0077; RelB, P = 0.0157), and beta-catenin (P = 0.0001). Differences regarding p50, hypoxia-inducible factor 1 alpha (HIF-1 alpha), and cytoplasmic FLIP were statistically significant when PVRs and primary EECs were matched for histological grade. Exposure of the EEC cell line to hypoxia induced nuclear expression of beta-catenin, FLIP, and HIF-1 alpha, as well as increased NF-kappa B activity. No changes in FLIP, HIF-1 alpha or NF-kappa B were seen when cells were exposed to radiation. Nuclear expression of b-catenin was seen at 3 Gy, but not at 1 Gy. Conclusions: Genes involved in resistance to hypoxia are expressed in PVRs, and may play a role in the development of post-radiation recurrences.