Abstract
We have examined the effect of neutralizing TGF-beta antibodies on cisplatin-mediated cytotoxicity against MDA-231 human breast tumor cell spheroids. These tridimensional in vitro systems have been shown to recapitulate the drug sensitivity pattern of tumor cells in vivo. MDA-231 tumor cell spheroids exhibit higher protein levels of the cyclin-dependent kinase (Cdk) inhibitors p21 and p27 and >10-fold lower Cdk2 activity compared to adherent cell monolayers, as well as pRb hypophosphorylation, a predominant G1 population, and a cisplatin 1-h IC50 of approximately 100 microM. Treatment of MDA-231 cells in monolayer with cisplatin for 1 h, subsequently grown as spheroids, increased steady-state TGF-beta1 mRNA levels, secretion of active TGF-beta, cellular Cdk2 activity, pRb phosphorylation, and p21 protein levels, while downregulating p27. Accumulation of cells in G2M and progression into S were noted 48 h after treatment with 100 microM cisplatin. We tested whether drug-induced upregulation of TGF-beta1 and p21, perhaps by preventing cell cycle progression, were protective mechanisms against drug-mediated toxicity by using neutralizing anti-TGF-beta antibodies. Anti-TGF-beta antibodies diminished the induction of p21, enhanced the activation of Cdk2, and facilitated progression into S and G2M following cisplatin treatment. This resulted in a >twofold enhancement of drug-induced DNA fragmentation and a shift in the cisplatin 1-h IC50 from 100 to <10 microM. These data suggest that tumor cell TGF-beta1 may protect from DNA damage and that postchemotherapy administration of TGF-beta inhibitors may facilitate progression beyond G1/S, potentially increasing the efficacy of cytotoxic chemotherapy.
Copyright 1998 Academic Press.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Antineoplastic Agents / pharmacology*
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Antineoplastic Agents / therapeutic use
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Breast Neoplasms / drug therapy*
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Breast Neoplasms / pathology
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Breast Neoplasms / physiopathology
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CDC2-CDC28 Kinases*
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Cell Aggregation / drug effects
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Cell Cycle / drug effects*
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Cell Cycle Proteins*
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Cell Death / drug effects
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Cisplatin / pharmacology*
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Cisplatin / therapeutic use
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclin-Dependent Kinase Inhibitor p27
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Cyclin-Dependent Kinases / antagonists & inhibitors
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Cyclin-Dependent Kinases / metabolism
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Cyclins / metabolism
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DNA Fragmentation / drug effects
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Gene Expression Regulation, Neoplastic / drug effects
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Humans
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Immunoglobulin G / pharmacology
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Inhibitory Concentration 50
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Microtubule-Associated Proteins / metabolism
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Phosphorylation / drug effects
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Protein-Serine-Threonine Kinases / antagonists & inhibitors
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Protein-Serine-Threonine Kinases / metabolism
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Proteins
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Retinoblastoma Protein / metabolism
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Transforming Growth Factor beta / antagonists & inhibitors*
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Transforming Growth Factor beta / genetics
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Transforming Growth Factor beta / immunology
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Transforming Growth Factor beta / metabolism
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Tumor Cells, Cultured
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Tumor Suppressor Proteins*
Substances
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Antineoplastic Agents
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CDKN1A protein, human
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Cell Cycle Proteins
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins
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Immunoglobulin G
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Microtubule-Associated Proteins
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Proteins
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Retinoblastoma Protein
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Transforming Growth Factor beta
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Tumor Suppressor Proteins
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Cyclin-Dependent Kinase Inhibitor p27
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Protein-Serine-Threonine Kinases
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CDC2-CDC28 Kinases
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CDK2 protein, human
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Cyclin-Dependent Kinase 2
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Cyclin-Dependent Kinases
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Cisplatin