RESUMEN
Stathmin is a p53-regulated protein known to influence microtubule dynamics. Because several chemotherapeutic agents used to treat breast cancer alter the dynamic equilibrium of tubulin polymerization, stathmin may play an important role in determining the sensitivity to these drugs. Therefore, we evaluated the effect of stathmin expression on the action of taxanes and Vinca alkaloids using a panel of human breast cancer cell lines. Cell lines harboring mutant p53 expressed high levels of stathmin. Two cell lines with different levels of endogenous stathmin expression and isogenic-paired cell lines transfected to overexpress stathmin were used to determine whether or not stathmin modulated the sensitivity to drugs. Overexpression of stathmin decreased polymerization of microtubules, markedly decreased binding of paclitaxel, and increased binding of vinblastine. Stathmin overexpression decreased sensitivity to paclitaxel and, to a lesser extent, to vinblastine. In contrast, stathmin content had no significant effect on the sensitivity to chemotherapeutic drugs that do not target microtubules. Cell lines overexpressing stathmin were more likely to enter G(2) but less likely to enter mitosis as determined by fluorescence-activated cell sorting and mitotic index. This effect was magnified when stathmin-overexpressing cells were treated with vinblastine as measured by the detection of proteins phosphorylated in early mitosis. These data suggest that the action of antimicrotubule drugs can be affected by stathmin in at least two ways: (a) altered drug binding; and (b) growth arrest at the G(2) to M boundary. Mutant p53 breast cancers exhibiting high levels of stathmin may be resistant to antimicrotubule agents.
Asunto(s)
Antineoplásicos Fitogénicos/farmacología , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Proteínas de Microtúbulos , Paclitaxel/farmacología , Fosfoproteínas/fisiología , Vinblastina/farmacología , Antineoplásicos Fitogénicos/metabolismo , Western Blotting , Neoplasias de la Mama/genética , Ciclo Celular/fisiología , Humanos , Microtúbulos/efectos de los fármacos , Microtúbulos/metabolismo , Mutación , Paclitaxel/metabolismo , Fosfoproteínas/biosíntesis , Fosfoproteínas/genética , Estatmina , Transfección , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/biosíntesis , Proteína p53 Supresora de Tumor/genética , Vinblastina/metabolismoRESUMEN
PURPOSE: Few molecular determinants of sensitivity to cancer chemotherapy exist. In experimental systems, p53 regulates the sensitivity to antimicrotubule drugs through its effect on microtubule-associated protein 4 (MAP4). MAP4 is the major microtubule-associated protein in nonneuronal tissues and promotes microtubule polymerization. We reported that wild-type p53 induction by doxorubicin in C127 breast cancer cells repressed MAP4, decreased microtubule polymerization, and increased Vinca alkaloid sensitivity. The goals of this Phase I/pilot clinical trial were to determine: (a) the safety of delivering a DNA-damaging agent (doxorubicin) followed in sequence by treatment with an antimicrotubule drug (vinorelbine); and (b) the feasibility of detecting activation of p53 and repression of MAP4 in patients' tissues. EXPERIMENTAL DESIGN: Peripheral blood mononuclear cells (PBMNCs) and tumor were obtained from 16 women with locally advanced (stage IIIb) or metastatic (stage IV) breast cancer before doxorubicin treatment and immediately before treatment with vinorelbine 24 or 48 h later. RESULTS: After doxorubicin treatment, p53 increased in 12 of 14 PBMNC and 4 of 10 tumor samples. Changes in MAP4 were variable; however, in samples in which p53 was induced, MAP4 decreased in 7 of 12 PBMNC and 3 of 4 breast cancer specimens. Immunohistochemistry confirmed lower MAP4 expression in tumor cells after doxorubicin treatment. Seven of 16 patients had a partial response, and treatment was well tolerated. CONCLUSIONS: These data demonstrate the ability to detect the activation of p53 and the repression of MAP4 in normal and malignant tissues in patients treated with a DNA-damaging agent, and that an antimicrotubule drug can be administered safely at a time when cells may be more sensitive to treatment.