Interactions between Malignant Keratinocytes and Fibroblasts Studies in Head and Neck Squamous Cell Carcinoma

Abstract: Carcinoma growth requires a supportive tumor stroma. The concept of reciprocal interactions between tumor and stromal cells has become widely acknowledged and the connective tissue activation seen in the malignant process has been likened to that of a healing wound. Little is, however, known about the specific characteristics of these interactions, distinguishing them from the interplay occurring between epithelial and stromal cells in wound healing. In order to study differences in the humoral effects of malignant and benign epithelial cells on fibroblasts, we used an in vitro coculture model with human oral squamous cell carcinoma cells (SCC) or normal oral keratinocytes (NOK) on one side of a semi-permeable membrane and fibroblasts seeded in gels on the other. Pro-collagens ?1(I) and ?1(III) were more downregulated in NOK cocultures compared to SCC cocultures. IL-1? was identified as a major keratinocyte-derived soluble factor behind the effects observed. We concluded that SCC are less antifibrotic compared to NOK. There was also a differential expression among enzymes involved in ECM turnover. The urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) were both upregulated by NOK, but not by SCC. Here, rIL-1ra caused further upregulation of PAI-1. Global gene expression in fibroblasts was assessed using Affymetrix™ arrays. In total, 82 transcripts were considered differentially expressed; 52 were up- and 30 were downregulated in SCC compared to NOK cocultures. Among the differentially expressed genes there was an enrichment of genes related to collagens and to a nonspecific, innate-type response. The innate response marker pentraxin (PTX3) was upregulated by keratinocyte-derrived IL-1? in both NOK and SCC cocultures. We observed a considerably higher IL-1? / IL-1ra quotient in SCC cocultures, however, while PTX3 mRNA upregulation was higher in SCC cocultures, there was no difference in the level of PTX3 secreted protein. Taken together, we concluded that NOK and SCC regulate genes important for ECM composition and for the innate immune-response differentially. IL-1? was identified as one important mediator of the observed effects. In general, SCC appeared to be more profibrotic in their effects on fibroblasts.