Abstract

The neoplastic conversion of a normal cell to a malignant one is a multistage process that occurs after a series of molecular alterations. Several chemical and physical agents can alter the morphology of different types of cells. Scanning and transmission electron microscopy have been valuable in evaluating changes that occur in the progression of transformation. MCF-10F, a spontaneously immortalized human breast epithelial cell line (Soule et al., 1990), was treated with benz(alpha)pyrene (BP) (Calaf and Russo, 1993) and then transfected with the c-Ha-ras oncogene (Calaf et al., 1995). The phenotypic changes of breast cancer progression were studied through the use of scanning and transmission electron microscopy. Activated oncogenes have been detected in a variety of malignant tumors and the altered expression of certain genes seems to play a role in the cancer process. Carcinogen-treated and transfected cells showed a progression of changes in the morphology, anchorage independent growth, invasiveness and capability of tumor formation in the SCID mice. This in vitro cancer model can parallel the progression of breast cancer seen through molecular changes that occur and have been observed during the natural development of this disease.