Effect of all-transretinoic acid on differentiation of cancer stem cells in colorectal cancer

Abstract

Objective To detect the promoting effects of all- trans retinoic acid(ATRA)on differentiation of cancer stem cells(CSCs)of colorectal cancer and the mechanism. Methods In order to enrich CSCs, magnetic activated cell sorting(MACS) was used to purify CD133+ CSCs from SW620 cell line. The proportion of CD133+ cells in purified CSCs was measured after treatment with 1.0×10-6 mol/ L ATRA or dimethylsurfoxide(DMSO)for 3 days by flow cytometry. The inhibitory effect of selfrenewing ability of CSCs induced by 1.0×10-6 mol/L ATRA was evaluated by sphere formation assay. Phosphorylation and degradation of β- catenin induced by 1.0×10-6 mol/L ATRA was confirmed by Western blotting. Results CD133+ SW620 cells effectively enrich CSCs. The rate of tumor spheres of CD133+ and CD133- cells was(51.00±7.67)% and(4.58±2.52)%, respectively (P< 0.01). After treatment with 1.0×10-6 mol/L ATRA, the proportion of CD133+ cells was (47.90±7.87)%,and that in the control group was(95.33±2.24)%, respectively(P< 0.01). Interestingly, the rate of tumor spheres was decreased from(53.66±6.03)% to(19.33±2.52)% (P< 0.01). Western blotting indicated that ATRA induced degradation of β- catenin by Thr41/ Ser45 phosphorylation. Conclusion ATRA induces differentiation of colorectal CSCs, and inhibits their self- renewing ability by suppression of Wnt/β- catenin pathway. Key words: All-trans retinoic acid; Colorectal cancer; Cancer stem cells; Cell differentiation