Blockade of transforming growth factor-beta signaling does not abrogate antiestrogen-induced growth inhibition of human breast carcinoma cells.
We have studied the role of autocrine transforming growth factor-beta (TGF-beta) signaling on antiestrogen-mediated growth inhibition of hormone-dependent T47D and MCF-7 human breast carcinoma cells. Tamoxifen treatment increased the secretion of TGF-beta activity into serum-free cell medium and the cellular content of affinity cross-linked type I and III TGF-beta receptors in both cell lines. Anti-pan-TGF-beta antibodies did not block anti-estrogen-induced recruitment in G1 and inhibition of anchorage-dependent and -independent growth of both cell lines. Early passage MCF-7 cells, which exhibit detectable type II TGF-beta receptors at the cell surface and exquisite sensitivity to exogenous TGF-beta1, were transfected with a tetracycline-controllable dominant-negative TGF-betaRII (DeltaRII) construct. Although the TGF-beta1 response was blocked by removal of tetracycline in MCF-7/DeltaRII cells, tamoxifen-mediated suppression of Rb phosphorylation, recruitment in G1, and inhibition of cell proliferation were identical in the presence and absence of tetracycline. TGF-beta1 treatment up-regulated the Cdk inhibitor p21 and induced its association with Cdk2 in MCF-7 cells; these responses were blocked by the DeltaRII transgene product. In MCF-7 cells with a functional TGF-beta signaling pathway, tamoxifen did not up-regulate p21 nor did it induce association of p21 with Cdk2, suggesting alternative mechanisms for antiestrogen-mediated cytostasis. Finally, transfection of late-passage, TGF-beta1 unresponsive MCF-7 cells with high levels of TGF-betaRII restored TGF-beta1-induced growth inhibition but did not enhance tamoxifen response in culture. Taken together these data strongly argue against any role for TGF-beta signaling on tamoxifen-mediated growth inhibition of hormone-dependent breast cancer cells.
Koli
K M
KM
Department of Medicine,Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Ramsey
T T
TT
Ko
Y
Y
Dugger
T C
TC
Brattain
M G
MG
Arteaga
C L
CL
D001943:Breast Neoplasms / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D004965:Estrogen Antagonists / Q000494:pharmacology*; D005260:Female; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D004965:Estrogen Antagonists; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D013629:Tamoxifen; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II