| Summary: | Basal cell carcinoma (BCC) is the most common skin cancer in humans. The demonstration of genetic and protein alterations has, so far, had limited correlation with either biological behaviour or histological classification of these tumours. It was observed that Glil-overexpressing keratinocytes express elevated levels of genes known to be associated with neuronal development, including p-tubulin III, GAP-43, Arc and neurofilament. It was proposed that these genes may similarly be overexpressed in BCCs and that different levels of expression may be present in different BCC subtypes Immunohistochemistry of BCCs demonstrated that neuronal differentiation marker proteins are expressed in BCCs, but that this expression is significantly reduced in tumours that behave aggressively. Elevated neuronal differentiation marker gene expression was shown in BCCs. Again, expression was more prominent in tumour types that behave indolently. Results were obtained for tumour samples processed by laser capture microdissection, needle microdissection and homogenised tissue. Expression of neuronal differentiation marker genes in Gli-overexpressing keratinocytes was examined by semi-quantitiative PCR. Neuronal differentiation marker expression was associated with GUI and GH2 over-expression in some cases {P-tubulin III and Arc). GUI and GH2 also promoted the expression of each other in a positive-feedback loop. Expression of these markers was examined in archival tumours for which the clinical outcome was known in terms of recurrence. In completely excised tumours P-tubulin III was significantly reduced in tumours that went on to subsequently recur. Other markers were not expressed in significantly different amounts. In summary, I have shown that expression of markers associated with neuronal development is a feature of Basal Cell carcinoma, and that the expression of these markers correlates strongly with the tumour histological subtype but only weakly with tumour recurrence. More work will be required to discover further alterations in BCC molecular biology that impact significantly on tumour behaviour.
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