BTB and CNC homology 1 (Bach1) induces lung cancer stem cell phenotypes by inducing CD44 expression

Abstract

Background Growing evidence suggests that CSCs are responsible for cancer initiation in tumors. Bach1 has been identified to contribute to several tumor progression, including lung cancer. The role of Bach1 in CSCs remains poorly known. Therefore, the function of Bach1 on lung CSCs was focused currently. Methods The expression of Bach1, CD133, CD44, Sox2, Nanog and Oct4 mRNA was assessed using RT-qPCR. Protein expression of Bach1, CD133, CD44, Sox2, Nanog and Oct4 was analyzed by western blotting. EdU, colony formation, Flow cytometry analysis and transwell invasion assay were carried out to analyze cell proliferation, apoptosis and invasion. Tumor sphere formation assay was utilized to evaluate spheroid capacity. The relationship between Bach1 and CD44 was verified using ChIP-qPCR and dual-luciferase reporter assay. Ki-67 expression was determined by flow cytometry and IHC assay. Results The ratio of CD44 + CSCs from A549 and SPC-A1 cells were significantly enriched. Tumor growth of CD44 + CSCs was obviously suppressed in vivo. Bach1 expression was obviously increased in CD44 + CSCs. Then, via using the in vitro experiment, it was observed that CSC growth and invasion were greatly reduced by the down-regulation of Bach1. Loss of Bach1 was able to repress tumor-sphere formation and tumor-initiating CSC markers via acting as a transcription inducer of CD44. A repression of CSCs growth and metastasis of shRNA-Bach1 was confirmed using xenograft models. Furthermore, MAPK signaling pathway was selected and we proved the effects of Bach1 on lung CSCs were associated with the activation of the MAPK pathway. Inhibition of MAPK signaling remarkably restrained lung CSCs growth and CSCs properties. Conclusion In summary, our findings reveal that Bach1 positively regulated CD44 + lung cancer CSCs growth and we imply that Bach1 demonstrates great potential for the treatment of lung cancer metastasis and recurrence via regulating CD44 and MPAK signaling.