Regulation of surface‐differentiation molecules by epidermal growth factor, transforming growth factor alpha, and hydrocortisone in human mammary epithelial cells transformed by an activated c‐Ha‐ras proto‐oncogene

Abstract

Spontaneously immortalized human mammary epithelial cells MCF-10A were transfected with an activated c-Ha-ras oncogene. Transfected cells (MCF-10T) acquire a malignant phenotype, as already reported. Studies of 125I-2'-deoxyuridine incorporation in cultures given graded doses of hydrocortisone (HC), cholera toxin (CT), epidermal growth factor (EGF), and transforming growth factor alpha (TGF-alpha) showed that though MCF-10T had become almost independent on exogenous EGF and TGF-alpha, they continued to respond to the synergistic effect of HC and CT plus EGF. Both lines were phenotypically characterized with an immunoradiometric assay in live cells. Expression of MHC class-I molecules, human milk-fat-globule-I antigen, and EGF receptor was reduced in ras-transfected cells, although other differentiation markers were unchanged. Exogenous EGF down-regulated the expression of functional EGF-R, selectively in transformed cells. TGF-alpha failed to modulate EGF-R. In contrast, HC strongly stimulated the expression of EGF-R while depressing MHC class-I molecules. Thus, it appears that in vivo HC may co-operate with TGF-alpha and EGF in promoting the growth of transformed mammary cells. This hormone might also favor the escape from immune surveillance by reducing the expression of surface differentiation markers.

Downregulation of aryl hydrocarbon receptor function and cytochrome P450 1A1 induction by expression of ha-ras oncogenes

“…Conversely, introduction of an AHR antisense expression construct into 1c1c7 cells prolongs G 1 [42]. We have found, as has been previously reported [17], that the doubling time of MCF10A-NeoT cells grown under optimal conditions was not significantly different from that of the parental MCF10A line (Reiners JJ, Jr, unpublished data). Hence, if the AHR does play a role in cell-cycle control, the role appears to be independent of the enhancer activity of the AHR-ARNT heterodimer because the heterodimer's activity is ablated in MCF10A-neoT cells.…”

“…The derivation and characterization of these cells and their p21-ras contents have been described elsewhere [15,16]. With the exception of the EGF content being increased from 10 to 20 ng/mL, the cells were cultured in the supplemented Dulbecco's modified Eagle's medium/F12 medium described by Basolo et al [17] in a humidified atmosphere of 95% air and 5% CO 2 at 37°C. Subconfluent cultures were treated with TCDD dissolved in dimethyl sulfoxide (DMSO) (absolute volume of solvent less than 0.1% of medium volume).…”

Epidermal growth factor (EGF) suppresses staurosporine-induced apoptosis by inducing mcl-1 via the mitogen-activated protein kinase pathway

“…However, the antiapoptotic e ect reached a plateau at 30 ng/ml (5610 79 M). In EGF receptor-overexpressing Rat-1 cells (Osterop et al, 1994) and a human breast epithelial cell line MCF-10A (Basolo et al, 1992), a signi®cantly higher mitogenic e ect was seen after the addition of 10 710 M rather than 10 79 M EGF. Thus, EGF may utilize high a nity or low a nity receptors to transduce mitogenic or survival signals, respectively.…”

Phorbol Ester Activation of a Proteolytic Cascade Capable of Activating Latent Transforming Growth Factor-β

“…2 MCF10A-Neo cells were cultured in supplemented Dulbecco's modified Eagle's medium/Ham's F-12 medium as previously described (30). The supplements consisted of human insulin (10 g/ml), epidermal growth factor (10 ng/ml), cholera toxin (100 ng/ml), hydrocortisone (0.5 g/ml), 100 units/ml penicillin G, 100 g/ml streptomycin sulfate, and 5% horse serum.…”