Objective: The aim of the study was to observe the effect of Bmi1 reduction on the self-renewal and tumorigenicity ability of lung cancer stem cells (LCSCs) in human lung adenocarcinoma. Methods: Human lung adenocarcinoma cells A549 were consecutively passaged in NOD/SCID mice treated with Paclitaxel weekly. The proportions of LCSCs in A549 cells and the cells from the third passage (A549-3rd) were compared. The expression of Bmi1 in LCSCs was silenced by intratumoral injection with lentivirus-delivered Bmi1 small hairpin RNA (shRNA). RT-PCR and Western blot were used to test the mRNA and protein expressions of Bmi1 in LCSCs. The protein level of p16INK4A was analyzed by Western blotting. The self-renewal and tumorigenicity ability of LCSCs were evaluated by counting the sphere formation rate in serum-free medium and the tumor formation rate in NOD/SCID mice. Results: In vivo passaging of A549 cells under chemotherapy pressure enriched for LCSCs. The expression of Bmi1 in LCSCs increased. Down-regulation of Bmi1 by RNA interference resulted in reduced self-renewal and tumorigenicity ability of LCSCs and paralleled the increased expression of p16INK4A, a Bmi1 target. Conclusion: Bmi1 regulates self-renewal and tumorigenicity of LCSCs by silencing some target genes, including p16INK4A.
