Aim: The CD133 antigen has been identified as a putative stem cell marker in colorectal cancer tissues. The aim of this study was to investigate the cell cycle state of CD133(+) and CD133(-) cells, isolated from primary human colorectal tumors.
Materials and methods: After mechanical and enzymatic dissociation of the tumor samples, CD133(+) and CD133(-) subsets were identified and separated by magnetic cell sorting. Flow cytometric analysis was performed to compare the cell cycle of both CD133(+) and CD133(-) cells isolated from primary and liver metastatic cancer cells.
Results: The results indicated that CD133(+) cells isolated from both primary and liver metastatic colorectal cancers were found in higher percentage in the G0/G1 phases. However, the CD133(-) cells isolated from primary colorectal cancers were predominantly found in the S and G2/M phases. Surprisingly, the CD133(-) cells isolated from liver metastatic colorectal cancers were mostly found in the G0/G1 phase.
Conclusion: The present study provides evidence that CD133(+) cells are in a quiescent state in colorectal cancer, representing a mechanism that would at least partially explain chemotherapy resistance and tumor recurrence in post-therapy patients.