RESUMO
Paclitaxel (Taxol) is a chemotherapeutic agent that prevents disassembly of microtubular polymers, causing a growth arrest in the G2-M phase of the cell cycle and leading to apoptotic death. Paclitaxel has remarkable efficacy against fast-growing tumors but possesses major drawbacks, such as poor solubility and lack of tumor selectivity. Conversely, monoclonal antibodies usually have low therapeutic efficacy but are highly soluble and selectively target tumor markers overexpressed in cancer cells. Therefore, to improve the therapeutic index of taxanes as chemotherapeutics, the high toxicity of paclitaxel was combined with the high selectivity and solubility of monoclonal antibodies as targeting agents. We report the chemical coupling and characterization of paclitaxel-antibody conjugates for treatment of neuroectoderm-derived tumors. Paclitaxel-antibody conjugates afforded selective toxicity toward cells expressing the target marker and were more cytotoxic in vitro than equimolar concentrations of free paclitaxel or free paclitaxel plus free antibody. In an in vivo model of xenografted tumors, systemic administration of paclitaxel-antibody conjugates prevented tumor growth and prolonged survival of mice better than free drugs. In addition, paclitaxel-antibody conjugates were highly soluble in water and stable at -20 degrees C for at least 3 months. These studies may lead to an increase or an improvement of the armamentarium and selectivity of cytotoxic agents.
Assuntos
Anticorpos Monoclonais/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Paclitaxel/farmacologia , Receptor de Fator de Crescimento Neural/imunologia , Receptor trkA/imunologia , Células 3T3 , Animais , Anticorpos Monoclonais/química , Anticorpos Monoclonais/metabolismo , Especificidade de Anticorpos , Relação Dose-Resposta a Droga , Feminino , Humanos , Imunoconjugados/metabolismo , Imunoconjugados/farmacologia , Cinética , Camundongos , Camundongos Nus , Transplante de Neoplasias , Paclitaxel/química , Ligação Proteica , Receptor de Fator de Crescimento Neural/metabolismo , Receptor trkA/metabolismo , Sensibilidade e Especificidade , Solubilidade , Resultado do Tratamento , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
We have developed a rapid and sensitive radioimmunoassay for the measurement of paclitaxel and related taxanes in biological specimens using commercially available reagents. The presence of paclitaxel competitively inhibited the binding of radioactive paclitaxel to polyclonal anti-taxane antibody or anti-taxane monoclonal antibody. When using polyclonal antibody, this method detected paclitaxel in concentrations as low as 0.87 nM and was also effective in 20% methanol. This radioimmunoassay is useful for the measurement of paclitaxel and taxanes in biological specimens like culture medium of paclitaxel-producing microorganisms and may be useful for the measurement of paclitaxel and related compounds in other potential natural sources.
Assuntos
Hidrocarbonetos Aromáticos com Pontes/análise , Paclitaxel/análise , Radioimunoensaio , Taxoides , Animais , Anticorpos , Hidrocarbonetos Aromáticos com Pontes/imunologia , Humanos , Paclitaxel/imunologia , Sensibilidade e EspecificidadeRESUMO
A rapid and very sensitive enzyme immunoassay was developed for the measurement of paclitaxel and related taxanes in crude extracts of Taxus sp., in human serum and in culture medium of paclitaxel-producing microorganisms such as Erwinia taxi. For the ELISA, paclitaxel was chemically modified by the introduction of an amine to enable coupling with biotin. The presence of paclitaxel or related taxanes competitively inhibited the binding of paclitaxel-biotin to anti-taxane monoclonal antibody. This method detected paclitaxel in concentrations as low as 33 pM; the affinity of the antibody was higher for paclitaxel than for cephalomanine, baccatin and DAB. The sensitivity of this assay makes it useful for estimating the paclitaxel and taxanes content of Taxus sp. extracts, monitoring the paclitaxel serum level of paclitaxel treated patients and in other biological fluids.
