Characterization of the conversion between CD133⁺ and CD133^- cells in colon cancer SW620 cell line

Abstract

The state of cancer stem cells (CSC) under reversible fluctuations, which has been revealed in breast cancer cells most recently, suggests that subpopulations with distinct phenotypes and functions within cancer cells can undergo inter-conversion. To investigate the possibility in colon cancer cells, we employed CD133 as the CSC marker, and characterized CD133 expression pattern and the biological features of the CD133⁺ and CD133^- subsets. Flow cytometry revealed that CD133 was bimodally expressed in SW620 cells among eight colon cancer cell lines. The CD133⁺ clonal SW620 cells displayed a differential gene expression profile, higher cellular reactive oxygen species (ROS), enhanced tumorigenesis and resistance to 5-fluorouracil. The conversion in term of the CD133 phenotype of the sorted cells was observed in vitro and in vivo. The fraction of the CD133⁺ cells decreased from 99% to 80% in the sorted CD133⁺ population while rising from 5 to 10% in the sorted CD133^- population during the first 20-day cultivation and then stayed almost unchanged. A fraction (about 20%) of the CD133⁺ clonal cells lost their CD133 marker while about 10% of the CD133^- clonal cells acquired the CD133 marker. 5-Azacytidine enhanced the fraction of the CD133⁺ cells in both of the CD133⁺ and CD133^- clonal cells. Our data demonstrate that CD133 expression is dynamic and reversible, and reveal the inter-conversion between the CD133⁺ and the CD133^- SW620 cells, suggesting that the CD133 phenotype of SW620 cell population is retained by the conversion between the two cell subsets.

Keywords: :

• CD133
• SW620
• cancer stem cells
• colon cancer
• conversion

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We sincerely thank Mrs. Li-Juan Lu, Mr. Yong Xi and Miss Yan-Yan Shen for their technical supports in animal experiments. This study was supported by grants from the National Natural Science Foundation of China (No. 81025020 and No. 81021062), the National Basic Research Program of China (No. 2012CB932502), the National Science and Technology Major Project of China (No. 2012ZX09301–001–002), the “Interdisciplinary Cooperation Team” Program for Science and Technology Innovation of the Chinese Academy of Sciences, and the Science and Technology Commission of Shanghai Municipality (STCSM) (No. 09540704100). The funding agencies had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.