Oncoprotein BMI-1 Induces the Malignant Transformation of HaCaT Cells

BMI-1 (B-cell-specific Moloney murine leukemia virus integration site 1), a novel oncogene, has attracted much attention in recent years for its involvement in the initiation of a variety of tumors. Recent evidence showed that BMI-1 was highly expressed in neoplastic skin lesions. However, whether dysregulated BMI-1 expression is causal for the transformation of skin cells remains unknown. In this study, we stably expressed BMI-1 in a human keratinocyte cell line, HaCaT. The expression of wild-type BMI-1 induced the malignant transformation of HaCaT cells in vitro. More importantly, we found that expression of BMI-1 promoted formation of squamous cell carcinomas in vivo. Furthermore, we showed that BMI-1 expression led to the downregulation of tumore suppressors, such as p161NK4a and p14ARF, cell adhesion molecules, such as E-Cadherin, and differentiation related factor, such as KRT6. Therefore, our findings demonstrated that dysregulated BMI-1 could indeed lead to keratinocytes transformation and tumorigenesis, potentially through promoting cell cycle progression and increasing cell mobility. J. Cell. Biochem. 106: 16-24, 2009. (C) 2008 Wiley-Liss, Inc.