Expression of the oncogenes mil and ras abolishes the in vivo differentiation of mammary epithelial cells

Abstract

Three carcinoma-associated oncogenes, two of which have been strongly implicated in human mammary tumorigenesis, have been introduced into a novel mouse mammary epithelial cell line, EF43, that retains many differentiated functions. The effect of oncogene expression upon classical transformation parameters as well as parameters specific for mammary epithelial cells such as growth in three-dimensional collagen matrices and the ability to repopulate the cleared mammary fat pad and to form alveolar structures in vivo has been investigated. Expression of \-myc in EF43 cells results in no obvious phenotypk changes, and does not confer tumorigenic potential upon the cells. Expression of v-Ha-ras confers upon EF43 cells the ability to grow rapidly, grow in an anchorageindependent manner, results in tumor formation in nude and syngeneic animals, abolishes their ability to repopulate the mammary gland and, instead, results in rapid induction of anaplastic tumors. The v-mil oncogene, an avian homolog of the mouse \-mht and human c-raf oncogenes, previously thought to be non-transforming in the absence of a cooperating oncogene, transforms EF43 cells, allowing them to grow in an anchorage-independent manner, form tumors in nude mice and abolishes their ability to repopulate the cleared mammary fat pad. In contrast to v-ras, however, the tumors arising from \-mil expression have a differentiated morphology, typical of adenocarcinomas. Thus, different oncogenes show varying degrees of inhibition of the differentiation of mammary epithelial cells in vivo. IntroductionNeoplastic transformation of the mammary gland proceeds via a multistep pathway involving the tumorigenic conversion of one or a number of mammary cell types. The identity of the cell types involved in this process, their interaction during the conversion and the identity of the cellular genes which are deregulated is open both to speculation and investigation.Transfection of DNA from the human mammary tumor derived cell line MCF-7 into NIH/3T3 fibroblasts has identified potential mammary oncogenes (1). Additionally, the Ha-ras oncogene has been found activated or overexpressed in some human mammary•Abbreviations: EGF, epidermal growth factor, HANs, hyperplastic alveolar nodules.tumors (2 -4) and a human mammary tumor cell line (5,6). Two erb-B related genes, the human epidermal growth factor (EGF*) receptor gene (7,8) and the neu oncogene (9) have been found amplified in human mammary carcinoma derived cell lines. More recently, the neu oncogene has been shown to be amplified in primary mammary tumors (10). Similarly, the c-myc gene has been found to be amplified (11) and overexpressed in some human primary breast carcinomas (12).In the mouse, depending upon strain, either plaques or hyperplastic alveolar nodules (HANs) represent the first visible preneoplastic lesion. HANs, and less frequently plaques, may eventually progress to overt mammary tumors (13). During this progression a number of genes may become activated including the putative mammary oncogenes, in...

A Novel Pathway for Mammary Epithelial Cell Invasion Induced by the Helix-Loop-Helix Protein Id-1

“…Id-1-expressing SCp2 cells did not grow in an anchorage-independent manner and did not form detectable tumors in nude mice. Thus, Id-1 differs from oncogenes such as v-Ha-ras, which converts mouse mammary epithelial cells into invasive but also tumorigenic cells (13). Furthermore, Id-1 did not induce an invasive phenotype by converting cells to a stromal or mesenchymal phenotype.…”

Neoplastic transformation of mouse mammary epithelial cells by deregulated myc expression.

“…We used electroporation as the mode of gene transfer into the MMEC. Because most epithelial cells are poorly transfectable by the conventional calcium phosphate technique (Redmond et al, 1988), many investigators have used retrovirus-mediated gene transfer to transfect epithelial cells (Gunzberg et al, 1988;Redmond et al, 1988;Ball et al, 1988). We have demonstrated high-efficiency, stable gene transfer by electroporation into a variety of cell types, including epidermal keratinocytes (Reiss et al, 1986), bone marrow cells ), neuronal cells (Ito et al, 1989), as well as many different primary cell types (Narayanan, unpublished observations).…”

The Nogo-B receptor promotes Ras plasma membrane localization and activation

“…Therefore, upregulation of normal Ras activity by receptor tyrosine kinases (RTK), such as the EGF receptor family, is a major focus for breast cancer research 23, 30 . Introduction of activated H-Ras into certain mouse or human breast epithelial cells results in acquisition of a transformed phenotype in vitro (such as increased anchorage independent growth) and in vivo , as shown by the ability to form tumors in nude mice 10, 15, 48 . In addition, a large number of clinical studies have demonstrated overexpression of Ras in breast cancers 12, 34, 64 .…”