Expression of transforming growth factor α antisense mRNA inhibits the estrogen‐induced production of TGFα and estrogen‐induced proliferation of estrogen‐responsive human breast cancer cells

Abstract

To ascertain if 17 beta-estradiol (E2)-induced proliferation could be attenuated by blocking the expression of endogenous transforming growth factor alpha (TGF alpha), estrogen receptor (ER)-positive, estrogen-responsive MCF-7 or ZR-75-1 cells and ER-negative, estrogen-nonresponsive MDA-MB-468 or HS-578T cells were infected with a recombinant amphotropic, replication-defective retroviral expression vector containing a 435 base pair (bp) Apa1-Eco R1 coding fragment of the human TGF alpha cDNA oriented in the 3' to 5' direction and under the transcriptional control of an internal heavy metal-inducible mouse metallothionein (MT-1) promoter and containing the neomycin (neo) resistance gene. E2-stimulated expression of endogenous TGF alpha mRNA was inhibited by 4-5-fold, and the production of TGF alpha protein was inhibited by 50-80% when M-1 mass-infected MCF-7 or MZ-1 mass-infected ZR-75-1 cells were treated with 0.75-1 microM CdCl2, whereas in comparably treated parental MCF-7 or ZR-75-1 cells there was no significant effect upon these parameters. E2-stimulated anchorage-dependent growth (ADG) and anchorage-independent growth (AIG) of the M-1 or MZ-1 cells was inhibited by 60-90% following CdCl2 treatment. In contrast, neither the ADG nor AIG of the parental noninfected MCF-7 or ZR-75-1 cells that were maintained in the absence or presence of E2 was affected by comparable concentrations of CdCl2. The ADG and AIG of TGF alpha antisense MD-1 mass-infected MDA-MB-468 cells that express high levels of endogenous TGF alpha mRNA were also inhibited by 1 microM CdCl2, whereas the ADG and AIG of MH-1 mass-infected HS-578T cells, a TGF alpha-negative cell line, were unaffected by CdCl2 treatment. These results suggest that TGF alpha may be one important autocrine intermediary in regulating estrogen-induced cell proliferation.

Transcriptional activation of transforming growth factor alpha by estradiol: requirement for both a GC-rich site and an estrogen response element half-site

“…E2 induced DNA synthesis and growth of stably transfected T47D cells; however, cotreatment with cadmium increased expression of antisense TGF mRNA and decreased hormone-induced mitogenic activity. The data confirmed results of an earlier study showing that antisense TGF mRNA oligonucleotide inhibited comparable E2-induced responses in breast cancer cells (Kenney et al 1993).…”

Cripto: roles in mammary cell growth, survival, differentiation and transformation

“…We found that Cr-1 was expressed at higher levels when cells were stimulated to grow and differentiate to lactogenic phenotypes (in the presence of lactogenic hormones and extracellular matrix), similar to pregnant glands in vivo (Figure 1). This strengthens the hypothesis that these hormones upregulate Cr-1 expression as they do amphiregulin (Martinez-Lacaci et al, 1995) and TGFa (Kenney et al, 1993;Reddy et al, 1994) in mammary tissue. Kenney et al (1995) showed by RT ± PCR, the presence of Cr-1 mRNA in the virgin mouse mammary gland, although 24 or 26 kDa proteins were not observed using an anti-human Cr-1 antibody.…”

Inhibition of epidermal growth factor receptor gene expression and function decreases proliferation of head and neck squamous carcinoma but not normal mucosal epithelial cells

“…The ligand-receptor interaction, therefore, may occur either in the cytoplasm, as has been previously suggested (Massague, 1990;Laird et al, 1994;Kenney et al, 1993), or on the cell surface. To dierentiate between an intracrine and a juxtacrine or external autocrine pathway, we treated SCCHN cells with two dierent monoclonal antibodies known to block EGFR ligand-binding.…”