Oncoprotein expression in human breast epithelial cells transformed by high-LET radiation

Purpose: The aim of the present work was to analyze the expression of oncoproteins that are frequently altered in breast cancer with specific phenotypic stages in the neoplastic process. Materials and methods: Expression of c-myc, c-jun, c-Ha-ras and the tumor suppressor gene p53 oncoproteins were examined by immunohistochemical staining coupled with confocal microscopy in transformed and tumorigenic human breast epithelial cells induced by high-LET α-particles (150 keV/μm). Results: MCF-10F cells, irradiated with single and double doses of 60 cGy α-particles and subsequently treated with estrogen, showed gradual phenotypic changes including altered morphology, increased cell proliferation relative to control, anchorageindependent growth, invasive capabilities and tumorigenicity in nude mice. MCF-10F cells irradiated with a second dose of 60 cGy α-particles after estrogen treatment (60 cGy + E/60 cGy + E) showed tumorigenicity, both in SCID and nude mice. Alterations in the protein expression of several oncogenes including c-myc, c-jun, c-Ha-ras and the tumor suppressor gene p53 were detected in α-particle-irradiated cells and in those cells subsequently cultured in the presence of estrogen. The expression level of these oncoproteins correlated with the progressive nature of the neoplastic process. Conclusion: These studies suggest that overexpression of several oncoproteins is important in the neoplastic transformation of human breast epithelial cells induced by high-LET radiation. In addition, use of endocrine factors such as estrogen allows the examination of various aspects of protein expression providing the basis for understanding the complex interactions of hormones and genes.