Immunochemical analysis of protein expression in breast epithelial cells transformed by estrogens and high linear energy transfer (LET) radiation.

Breast cancer is a complex disease involving numerous genetic aberrations. Immunochemical analysis of protein expression is presented in a human breast epithelial cell line neoplastically transformed by high linear energy transfer (LET) alpha particle radiation in the presence of 17beta estradiol (E) and in the parental human breast epithelial cell line (MCF-10F) which served as a non-tumorigenic control. The aim of this work was to determine the levels of mRNA and protein expression in control and transformed cells at various stages of the neoplastic process. The levels of mRNA and protein expression of PCNA, c-fos, JNK2 and Fra-1 were increased in the transformed cell line compared to the levels in non-tumorigenic control cells. The transforming factor Rho A was significantly increased only in the tumor cell line. Furthermore, the levels of mRNA and protein expression of ErbB2 were significantly increased in the transformed cell line and in tumor cells derived from the transformed cells after injecting them into nude mice. A decrease in RbA/p48 protein expression and mRNA levels was observed in cells treated with double doses of alpha particle radiation in the presence of estrogen, regardless of tumorigenicity. Such expression was lower than that in the control untreated MCF-10F cells. In summary, these studies show that estrogen and high LET-radiation induce changes in oncoprotein expression and mRNA levels of human breast cell lines. These changes are indicative of a cascade of events that characterize the process of cell transformation in breast cancer. These results provide evidence that multiple steps with consecutive changes are involved when normal cells become tumorigenic cells as a result of alpha particle irradiation and estrogen treatments.