Over Expression of BMI-1 and ABCG2 in Oral Cancer

Objectives: The cancer stem cell (CSC) hypothesis suggests that only a specific subpopulation of self-sustaining cancer cells have the exclusive ability to maintain the tumour. Although there has not been a well-defined set of markers defined for CSCs in oral squamous cell carcinoma, several studies have been conducted and a number of markers proposed. The objective of this research was to investigate the expression of reported stem cell markers ABCG2 and Bmi-1 in oral squamous cell carcinoma using immunohistochemistry. Furthermore, expression of ABCG2 and Bmi-1 will be investigated in cell lines derived from normal oral mucosa and oral squamous cell carcinoma.

Methods: Expression of ABCG2 and Bmi-1 was investigated in 270 human tissue biopsies comprising oral squamous cell carcinoma (120), severely dysplastic oral mucosa (20), mildly dysplastic oral mucosa (60) and normal oral mucosa (70) via immunohistochemistry. Furthermore, qPCR was undertaken to investigate the expression of ABCG2 and Bmi-1 in a number of cell lines (OKF6, DOK, POE, PJ15, SCC04, SCC09, SCC15 and SCC25). 

Results: IHC revealed strong Bmi-1 expression in basal cells. It was also found to be over-expressed in dysplastic and cancerous cell lines as compared to normal. In addition, the same cell lines over-expressed ABCG2.

Conclusions: The investigation of expression of Bmi-1 and ABCG2 in this sample of human biopsies and cell lines has provided valuable information regarding carcinogenesis of oral squamous cell carcinoma. It suggests that Bmi-1 and ABCG2 may be useful as cancer stem cell markers. Further research is required in this area in order to identify the true role of these markers.