ArRESTing oral cancer progression

Oral squamous cell carcinomas (OSCC) account for 40% of head and neck cancers and continue to have a poor prognosis. The molecular changes underlying OSCC development and progression are relatively poorly understood. Aberrant expression or function of transcription factor regulating genes involved in cell:extracellular matrix (ECM) interactions are implicated in many cancers. One transcription factor, the RE-1-silencing transcription factor (REST), is frequently down-regulated in solid tumours, leading to up-regulation of pro-tumourigenic target genes. Nothing is known of the expression or role of REST in OSCC.

Objectives: The objective of this Yorkshire Cancer Research funded study was to test the hypothesis that REST may act as a tumour suppressor in the oral epithelium.

Methods: qRT-PCR was used to examine REST transcript levels in a range of primary normal oral keratinocytes and cell lines derived from oral dysplastic lesions, squamous cell carcinomas and metastatic lesions. REST was heterologously expressed by transient transfection or suppressed by siRNA in vitro and the functional effect of this was analysed using adhesion assays employing MTS, and migration assays using transwells.

Results: REST expression levels were found to be altered in a number of cell lines compared to normal oral keratinocytes. H357 and B16, OSCC-derived cell lines which express low and high REST levels, respectively, were selected for functional assays. Heterologous, dose–responsive, over-expression of REST in H357 resulted in 44% reduction in migration (p<0.001) and a 4.7 fold increase in adhesion to fibronectin (p=0.016). Conversely, suppression of REST expression by siRNA in B16 produced a 62% increase in migration (p<0.001) and a 2 fold decrease in adhesion (p=0.014).

Conclusion: The results presented here suggest, for the first time, that REST may act as a tumour suppressor in oral cancer by influencing the expression of genes regulating interaction with the ECM and thereby reducing cell motility.