Fibroblast gene expression profile reflects the stage of tumor progression in oral squamous cell carcinoma

Oral cancer is a highly aggressive malignancy with poor prognosis. This study examined the behaviour of fibroblast strains from normal oral mucosa, dysplastic epithelial tissue and genetically stable (minimal copy number alterations-CNA; minimal loss of heterozygosity-LOH; wild type p53; wild type p16INK4A) and unstable (extensive CNA and LOH; inactivation of p53 and p16INK4A) oral squamous cell carcinoma (OSCC). Fibroblasts from genetically unstable OSCC relative to the other fibroblast subtypes grew more slowly and stimulated the invasion of a non-tumorigenic keratinocyte cell line into fibroblast-rich collagen gels. To understand these findings, genome wide transcriptional profiles were generated using the GeneChipR cDNA whole transcript microarray platform. Principal Component Analysis showed that the fibroblasts could be distinguished according to the stage of tumour development. Tumour progression was associated with down-regulation of cell cycle- and cytokinesis-related genes and up-regulation of genes encoding transmembrane proteins including cell adhesion molecules. Gene expression was validated in independent fibroblast strains using qRT-PCR. Gene connectivity and interactome-transcriptome associations were determined using a systems biology approach to interrogate the gene expression data. Clusters of gene signatures were identified that characterised genetically unstable and stable OSCCs relative to each other and to fibroblasts from normal oral mucosa. The expression of highly connected genes associated with unstable OSCCs, including those that encode α-SMA and the integrin α6, correlated with poor patient prognosis in an independent dataset of head and neck cancer. The results of this study demonstrate that fibroblasts from unstable OSCCs represent a phenotypically distinguishable subset that plays a major role in oral cancer biology.