Expression profiling of microdissected cell populations selected from basal cells in normal epidermis and basal cell carcinoma

Background Basal cell carcinomas (BCCs) are prevalent tumours with uniform histology that develop without any known precursor lesion. Alterations in the sonic hedgehog–patched1 signalling pathway are accepted as necessary events for tumorigenesis, and mutations in the patched1 gene are frequently present in tumours. Objectives To analyse transcript profiles in BCC. Methods We used laser‐assisted microdissection to isolate and collect cell populations defined under the microscope. Peripheral cells from nests of BCC were selected to represent tumour cells, and normal keratinocytes from epidermis basal layer were used as control. Extracted RNA was amplified and hybridized on to a cDNA microarray. Results Our results show that BCC cells express a transcript signature that is significantly different from that of normal keratinocytes, and over 350 genes with various functions were identified as differentially expressed. The compiled data suggest an upregulation of the Wnt signalling pathway as a major event in BCC cells. Furthermore, tumour cells appear to have an increased sensitivity to oxygen radicals and dysregulated genes involved in antigen presentation. Results were validated at both the transcriptional level using real‐time polymerase chain reaction and at the protein level using immunohistochemistry. Conclusions We show that microdissection in combination with robust strategies for RNA extraction, amplification and cDNA microarray analysis allow for reliable transcript profiling and that antibody‐based proteomics provides an advantageous strategy for the analysis of corresponding differentially expressed proteins. We found that expression patterns were significantly altered in BCC cells compared with basal keratinocytes and that the Wnt signalling pathway was upregulated in tumour cells.