Changes in in vitro growth behaviour of the mammary epithelial cell line NMuMG caused by the v‐fos oncogene

Abstract

A defective retrovirus was constructed to investigate the effect of the expression of the v‐fos oncogene from FBJ‐MSV on the in vitro growth properties of the mammary epithelial cell line NMuMG. Clearly visible areas of overgrowth in monolayer cultures of NMuMG were seen in cells infected with the v‐fos‐containing retrovirus but not in cells infected with control virus which did not contain an oncogene. Two cell lines, representing two morphological types of infected cell, were isolated from a morphologically altered region and further characterized. Fos.3.1.NMuMG grew as very spindly cells, achieving a higher density than control cells in 5% foetal calf serum (FCS) but growing very poorly in 1% FCS or in soft agar. Fos.3.3.NMuMG grew to a high density in 5% FCS and to a limited extent in low serum. This cell line also grew in soft agar. Fos.3.3.NMuMG seemed to be more transformed than fos.3.1.NMuMG using the criteria of growth in soft agar and low serum. All the cells used in this study were shown to retain epithelial characteristics by staining for cytokeratins and to contain at least one viral genome by Southern blotting. fos mRNA expression was raised over control levels in the two transformed cell lines.

Lonidamine and domperidone inhibit expansion of transformed cell areas by modulating motility of surrounding nontransformed cells

“…Cells transformed by accumulated genetic mutations proliferate and push out surrounding nontransformed cells, forming a cell mass called a focus in vitro . Focus formation assays utilizing this property have been widely used to identify oncogenes ( 5 ). We previously established a focus formation assay using normal mouse mammary epithelial cells (NMuMG) and identified several novel oncogenes ( 6 , 7 , 8 ).…”

Transformation of a mammary epithelial cell line by the v‐raf and v‐mos oncogenes

“…Northern analysis of the #43raf lines showed only one detectable transcript, but was not able to exclude expression from rearranged proviruses. Rearrangement of retroviral vectors has frequently been observed (Laker et al, 1987;Bradbury and Edwards, 1988;Gonda et al, 1989). In our hands, both YR and MPSVneo have shown a tendency to rearrange, an instability which should be considered when these or similar vectors are used.…”

“…We chose oncogenes which might have been expected to affect mammary epithelium. Previous reports have shown that some oncogenes cause easily observed morphological changes in certain types of epithelial cell (Fusco et al, 1985;Bradbury and Edwards, 1988;Giinzburg et al, 1988) while others do not (Giinzburg et al, 1988;Redmond et al, 1988). In the work reported here, both rufand rnos altered the morphology of the mammary epithelial cell line #43, and infected polyclonal cultures showed distinct areas of multilayering.…”

“…ras (Redmond et al, 1988), myc, src (Macauley and Pawson, 1988). int-1, fos (Bradbury andEdwards, 1988), mil (Giinzburg et al, 1988), raf (Rapp et al, 1985), and mos (Fusco et al, 1985) are oncogenes which have been shown to affect the growth of at least one type of epithelial cell in v i m . In many of these examples only some of the changes that are commonly shown by transformed fibroblasts (transformed morphology, increased saturation density, reduced serum requirement, anchorage-independent growth) have been seen, and it is not known if any of these criteria correlate with in vivo tumorigenicity in epithelial systems.…”

“…In several cases, cell lines have shown altered morphology, growth rates in vitro or tumorigenicity in vivo after an oncogene has been inserted. In the case of mammary epithelium, the putative mammary oncogene int-1 produced morphological changes in 2 mammary cell lines, although only one became tumorigenic; v-fos changed the morphology and growth behaviour of a mouse mammary epithelial cell line (Bradbury and Edwards, 1988); and another mammary epithelial cell line containing v-mil was tumorigenic in vivo although its morphology in vitro was unchanged (Giinzburg et al, 1988). We decided to investigate the oncogenes v-raf and v-mos, since both were good candidates for oncogenes which would transform epithelial cells.…”