Clinical Implications of Cancer Stem Cell Properties in Oral Squamous Cell Carcinoma.

Abstract

CD44 has been described as a marker of cancer stem cells in oral squamous cell carcinoma (OSCC). The main objective of this study was to characterise expression of CD44 in both fresh samples of human OSCC and in cell lines generated from them, and to examine its correlation with selected clinicopathological parameters of the tumours of origin. The epithelial fraction in 20 fresh OSCC samples was identified by the standard method using the negative selection technique with antibodies against non-tumour cells. A novel method of identifying the epithelial fraction, termed positive selection, was also developed and used for analysis of 14 additional OSCC samples. This new method, using epithelial-specific antibodies, led to a considerable improvement in the efficiency and the accuracy of the procedure. The frequency of CD44+ cells in the epithelial fraction of the tumour specimens was assessed by FACS and varied widely (3-97%). High frequency of CD44+ cells in tumour samples was found to be associated with high tumour grade, discohesive invasion front and presence of lymph node metastases (p<0.01, as calculated with Spearman’s ranked test and Fisher’s exact test). It was also observed, that the percentage of CD44+ cells changes when cells isolated from tumour samples are propagated in culture. Nearly all cells in cell lines generated from OSCC samples showed CD44 expression when analysed by FACS. However, a markedly higher level of CD44 expression (as assessed by median fluorescence intensity for cell surface CD44) was found for early passage cell lines generated from metastatic OSCC and lymph node metastases as compared to cell lines generated from nonmetastatic OSCC. These findings show that a high frequency of CD44+ cells in fresh OSCC tissue and a high level of CD44 expression in cultured OSCC cells correlate 11 with more aggressive tumour behaviour. These results might provide important information of prognostic and therapeutic value.