RESUMEN
Chemoresistance in multidrug-resistant (MDR) cells over expressing P-glycoprotein (P-gp) encoded by the MDR1 gene, is a major obstacle to successful chemotherapy for colorectal cancer. Previous studies have indicated that sinomenine can enhance the absorption of various P-gp substrates. In the present study, we investigated the effect of sinomenine on the chemoresistance in colon cancer cells and explored the underlying mechanism. We developed multidrug-resistant Caco-2 (MDR-Caco-2) cells by exposure of Caco-2 cells to increasing concentrations of doxorubicin. We identified overexpression of COX-2 and MDR-1 genes as well as activation of the NF-κB signal pathway in MDR-Caco-2 cells. Importantly, we found that sinomenine enhances the sensitivity of MDR-Caco-2 cells towards doxorubicin by downregulating MDR-1 and COX-2 expression through inhibition of the NF-κB signaling pathway. These findings provide a new potential strategy for the reversal of P-gp-mediated anticancer drug resistance.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Antibióticos Antineoplásicos/farmacología , Doxorrubicina/farmacología , Resistencia a Múltiples Medicamentos/genética , Resistencia a Antineoplásicos/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Morfinanos/farmacología , Células CACO-2 , Celecoxib , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Neoplasias del Colon/genética , Neoplasias del Colon/metabolismo , Ciclooxigenasa 2/genética , Ciclooxigenasa 2/metabolismo , Dinoprostona/metabolismo , Humanos , FN-kappa B/metabolismo , Pirazoles/farmacología , Transducción de Señal , Sulfonamidas/farmacologíaRESUMEN
The binding mode of (-)-zampanolide (ZMP) to tubulin was investigated using docking, molecular dynamics (MD) simulation, and binding free-energy calculations. The docking studies validated the experimental results indicating that the paclitaxel site is the binding site for (-)-ZMP. The 18 ns MD simulation shows the docking mode has changed a lot, whereas it offers more reliable binding data. MM-PBSA binding free-energy calculations further confirmed the results of the MD simulation. The study revealed that hydrophobic interactions play an important role in stabilizing the binding, and the strong hydrogen bond formed with Asp224 enhances the affinity for tubulin. Meanwhile, the results support the assumption that (-)-ZMP can be attacked by His227, leading to a nucleophilic reaction and covalent binding. These theoretical results lead to a greater understanding of the mechanism of action of binding to tubulin, and will therefore aid the design of new compounds with higher affinities for tubulin.
Asunto(s)
Macrólidos/química , Simulación del Acoplamiento Molecular , Simulación de Dinámica Molecular , Sitios de Unión , Enlace de Hidrógeno , Unión Proteica , Termodinámica , Tubulina (Proteína)/químicaRESUMEN
The molecular docking, MD simulation and binding free energy calculation were performed to explore the probable binding modes between PLA and tubulin. Through docking study, three possible binding sites for PLA were speculated as follows: the taxane site, the alternative site and a new site in α-tubulin. Then, 12.0 ns MD simulations show that these binding modes predicted by docking have been changed more or less, whereas the MD simulations offer more reliable binding details. The MM-PBSA binding free-energy calculations reasonably identify that the taxane site is the most favorable binding site of PLA and the alternative site is the secondary one, which can be used to explain some experimental facts. These studies theoretically resolve the priority of binding sites for PLA and offer the reliable binding modes between PLA and tubulin, and thus help to understanding the action mechanism for this kind of inhibitor.