Abstract

No abstract

(Background and purpose) Recently, many reports suggest that a limited population of tumor cells have the capability of tumorigenesis. These cells, called cancer stem cells (CSCs) or tumor initiating cells, are suggested to be involved in tumor recurrence after long interval as well as in chemo-resistance. There are several CSC markers, including CD44 and CD133. CD133, originally a hematopoietic stem cell marker, was identified also as a stem cell marker for various tumor types. In the present study, we aimed to compare the characteristics of CD133+ and CD133- colorectal cancer cells to test the hypothesis of CD133 being a potential specific marker for colorectal CSCs. (Methods) Using auto magnetic activated cell sorting (MACS), the human colon cancer cell line LoVo was separated into CD133+ and CD133- cell subpopulations, and their sensitivity to 5-FU, specially focusing on apoptosis and autophagy inductions were investigated. The sensitivity of CD133+ and - cells to 5-FU was tested by the MTS assay. And the induction of apoptosis was analyzed by flow-cytometry, after double-staining with annexin V-FITC/PI. The expression of β1-integrins was analyzed by flow-cytometry, and their ability to bind extracellular matrix (ECM) proteins was evaluated by the adhesion assay. Induction of autophagy was investigated by flow-cytometry after staining with acridine orange, and by Western blot for the expressions of the LC3 protein. (Results) After MACS isolation, CD133+ and CD133- cells were separately cultured. The purity of the obtained cell populations was more than 98%. After several days of culture, the proportion of CD133+ and CD133- cells was not changed in both cell populations during about a month. CD133- cells showed higher resistance to 5-FU than CD133+cells, in vitro. It was dependent on the higher induction of apoptosis in CD133+ cells. CD133+ cells had lower expression of β1-integrins compared with CD133- cells, and consequently, their ability to adhere ECM proteins was weaker. Additionally, AVOS formation was weaker in CD133+ cells, as well as the expression of LC3-II. (Discussion) CD133+ cells were more sensitive to 5-FU than CD133- cells, and it may be dependent on the higher ability of CD133- cells to induce autophagy in response to 5-FU. Additionally, CD133- cells had higher ability to adhere to ECM proteins through β1-integrins, and it may be another mechanism of chemo-resistance. Taking these results, higher ability to adhere to ECM proteins may confer resistance to 5-FU by improving the ability of cells to induce autophagy as a cell survival mechanism. Presently, there is controversy regarding CD133 as a specific marker of CSCs, but from our results, CD133- cells are more resistant to chemotherapy, one typical feature of CSCs. Therefore, we concluded that CD133 may not be used as a single CSC marker, but on the other hand, it may be a potential marker for the prediction of chemo-sensitivity in colorectal cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3367.