Antitumor activity and antioxidant role of a novel water-soluble carboxymethyl chitosan-based copolymer

In this study, a natural polymer, chitosan (CS) has been converted through modified procedures to produce a water-soluble nontoxic form that has been evaluated as a novel potential antitumor drug. CS was carboxymethylated and then further modified in mild aqueous medium via graft copolymerization using a new simple and reproducible method. The synthesized new derivative of carboxymethylated CS (DCMC) was fully characterized by numerous techniques including Fourier transform infrared spectroscopy (FT-IR), elemental analyzer (EA), scanning electron microscopy (SEM), two-dimensional wide-angle X-ray scattering (2D-WAXS), and differential scanning calorimetry (DSC). The anticancer activity of the DCMC was investigated using mice bearing Ehrlich ascites tumor cells (EAC) at different doses dissolved in isotonic saline. It has been found that treatment with DCMC significantly inhibited tumor growth in a dose-dependent manner. To better understand the molecular mechanism explaining the DCMC effect on cancer cells, we tested the response of EAC cells in vivo to DCMC using flow cytometry cell cycle analysis. The cell cycle analysis revealed a G₂/M phase accumulation as well as a significant increase in sub-G₁ phase cells after treatment with DCMC. This indicates an induction of apoptosis in EAC cells associated with a highly significant decrease in tumor volume. In general, our results indicated that the DCMC is a regulator of tumor cell growth and differentiation not only by causing G₂/M cell cycle arrest but also inducing their apoptotic death. Moreover, the estimated hematological profile such as hemoglobin, RBCs, as well as WBCs counts revealed normal levels in mice treated with DCMC, indicating the possibility of using the DCMC in cancer chemotherapy without causing anemia like other drugs. Biochemical assays also revealed that treatment with DCMC has led to an augmentation of the antioxidant defense system without affecting lipid peroxidation in EAC-bearing mice.