1,3-Bis(2-chloroethyl)-1-nitrosourea enhances the inhibitory effect of Resveratrol on 5-fluorouracil sensitive/resistant colon cancer cells

AIM:To study the mechanism of 5-fluorouracil(5-FU)resistance in colon cancer cells and to develop strategies for overcoming such resistance by combination treatment.METHODS:We established and characterized a 5-FU resistance(5-FU-R)cell line derived from continuous exposure(25μmol/L)to 5-FU for 20 wk in 5-FU sensitive HCT-116 cells.The proliferation and expression of different representative apoptosis and anti-apoptosis markers in 5-FU sensitive and 5-FU resistance cells were measured by the MTT assay and by Western blotting,respectively,after treatment with Resveratrol(Res)and/or 1,3-Bis(2-chloroethyl)-1-nitrosourea(BCNU).Apoptosis and cell cycle arrest was measured by 4',6'-diamidino-2-phenylindole hydrochloride staining and fluorescence-activated cell sorting analysis,respectively.The extent of DNA damage was measured by the Comet assay.We measured the visible changes in the DNA damage/repair cascade by Western blotting.RESULTS:The widely used chemotherapeutic agents BCNU and Res decreased the growth of 5-FU sensitive HCT-116 cells in a dose dependent manner.Combined application of BCNU and Res caused more apoptosis in5-FU sensitive cells in comparison to individual treatment.In addition,the combined application of BCNU and Res caused a significant decrease of major DNA base excision repair components in 5-FU sensitive cells.We established a 5-FU resistance cell line(5-FU-R)from 5-FU-sensitive HCT-116(mismatch repair deficient)cells that was not resistant to other chemotherapeutic agents(e.g.,BCNU,Res)except 5-FU.The 5-FU resistance of 5-FU-R cells was assessed by exposure to increasing concentrations of 5-FU followed by the MTT assay.There was no significant cell death noted in5-FU-R cells in comparison to 5-FU sensitive cells after5-FU treatment.This resistant cell line overexpressed anti-apoptotic[e.g.,AKT,nuclear factorκB,FLICE-like inhibitory protein),DNA repair(e.g.,DNA polymerase beta(POL-β),DNA polymerase eta(POLH),protein Flap endonuclease 1(FEN1),DNA damage-binding protein 2(DDB2)]and 5-FU-resistance proteins(thymidylate synthase)but under expressed pro-apoptotic proteins(e.g.,DAB2,CK1)in comparison to the parental cells.Increased genotoxicity and apoptosis were observed in resistant cells after combined application of BCNU and Res in comparison to untreated or parental cells.BCNU increased the sensitivity to Res of 5-FU resistant cells compared with parental cells.Fifty percent cell death were noted in parental cells when 18μmol/L of Res was associated with fixed concentration(20μmol/L)of BCNU,but a much lower concentration of Res(8μmol/L)was needed to achieve the same effect in 5-FU resistant cells.Interestingly,increased levels of adenomatous polyposis coli and decreased levels POL-β,POLH,FEN1 and DDB2 were noted after the same combined treatment in resistant cells.CONCLUSION:BCNU combined with Res exerts a synergistic effect that may prove useful for the treatment of colon cancer and to overcome drug resistance.

Synthesis and Characterization of Chitosan-Polyvinyl Alcohol Blended with Cloisite 30B for Controlled Release of the Anticancer Drug Curcumin

In the present research program, polymer nanocomposites have been used as the drug carrier for delivery systems of anticancer drug. Chitosan (Cs) and Polyvinyl Alcohol (PVA) with different ratios were blended with different wt% of Cloisite 30B solution by solvent casting method. Glutaraldehyde with different wt% was added to the blended solution as a crosslinking agent. Cloisite 30B was incorporated in the formulation as a matrix material component which also plays the role of a co-emulsifier in the nanocomposite preparation. Curcumin with different concentrations were loaded with CS-PVA/ C 30B nanocomposites for studying the in-vitro drug delivery systems. Morphology and structure characterization of nanocomposites were investigated by fourier transmission infra red spectroscopy (FTIR), scanning electron microscope (SEM), tensile strength and water uptake capacity. The drug release was studied by changing time, pH and drug concentrations. The kinetics of the drug release was studied in order to ascertain the type of release mechanism. Based on the diffusion as well as the kinetics, the mechanism of the drug release from the composite matrix has been reported.