Growth factor involvement in the multihormonal regulation of MCF-7 breast cancer cell growth in soft agar

Abstract

The hormone dependency of the MCF-7 breast cancer cell line, while extensively tested in liquid culture, has not been previously evaluated under conditions of anchorage-independent growth in serum-free media. Using the soft agar clonogenic assay, we demonstrate that physiologically relevant concentrations of estradiol (E2), progesterone (Pg), and prolactin (PRL) similarly stimulated MCF-7 cell colony formation in the absence of serum. Addition of an anti-insulin-like growth factor-I (IGF-I) antibody inhibited E2- and Pg-stimulated growth, while PRL action was not affected. Similar results were obtained with an anti-IGF-I receptor antibody, except that its inhibitory effect on Pg-induced colony formation was modest and not statistically significant. Administration of either an anti-transforming growth factor-alpha (TGF-alpha) antibody or an anti-epidermal growth factor (EGF) receptor antibody similarly inhibited E2-stimulated MCF-7 cell growth in soft agar, while neither antibody influenced Pg or PRL effects. Addition of TGF-beta 1, -beta 2, -beta 3 similarly suppressed MCF-7 cell colony formation in a dose dependent manner to a degree comparable to that observed with 4-OH-tamoxifen (4-OH-T). Furthermore, the growth inhibitory effect of 4-OH-T was completely reversed by an anti-TGF-beta antibody. We conclude that IGFs and TGF-alpha are important mediators of E2-stimulated MCF-7 cell growth in soft agar. IGFs may also be playing a role in Pg action, while neither growth factor is involved in PRL-stimulated colony formation. Finally, TGF-beta appears to be an important mediator of antiestrogen-induced inhibition of tumor growth.

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

“…These conclusions are in agreement with previous data showing that either neutralizing anti-TGFa antibodies and/or blocking anti-EGFR antibodies are able to produce a 50-75% inhibition of the E2-stimulated growth of MCF-7 cells that have been propagated under either ADG or AIG conditions (Bates et al, 1988;Eppstein et al, 1989;Manni et al, 1991). The specificity of these antibodies on MCF-'7 cells was confirmed by their ability to inhibit either EGF-or TGFa-stimulated ADG (Bates et al, 1988;Eppstein et al, 1989;Manni et al, 1991). In addition to these results, the basal or E2-stimulated clonogenicity of some primary human breast tumor cells in soft agar can be inhibited by either anti-TGFa neutralizing antibodies or by anti-EGFR-blocking antibodies (Ahmed et al, 1991).…”

Prognostic Significance of TGF-α Expression in Breast Cancer

“…In many of these studies, however, the number of patients was fairly small, which may limit their power. In breast cancer cell lines in vitro, TGF-a has mostly emerged as a growth stimulator of cancer cells (1,2,22). Consonant with these observations, the positive expression of TGF-a was significantly related to a low survival probability in univariate survival analysis.…”

Relationship between tamoxifen-induced transforming growth factor beta 1 expression, cytostasis and apoptosis in human breast cancer cells

“…ER( + ) MCF-7 breast cancer cells (Roberts et al, 1985;Knabbe et al, 1987), and four ER( -) breast cancer cell lines including MDA-231 (Arteaga et al, 1988) secrete and are inhibited by TGF-pl. It also appears that TGF-P, may be a mediator of TAMinduced cytostasis (Manni et al, 1991). Anti-oestrogens induce TGF-P3 activity in ER( +) MCF-7 cells in vitro (Knabbe et al, 1987), in ER( -) human fetal fibroblast in vitro (Colletta et al, 1990), and in both ER( + ) and ER( -) human breast cancer in vivo (Butta et al, 1992).…”