Methods: Real-time Polymerase Chain Reaction (PCR), tissue microarrays and immunohistochemistry were used.
Results: We have shown that depletion of the retinoblastoma protein (Rb) in stromal fibroblasts promotes epithelial invasion and so we have investigated whether Rb-depleted fibroblasts behave like myofibroblasts. Firstly, differentiation markers such as various cytoskeletal actins and extracellular matrix proteins were identified in primary human fibroblasts treated with TGFβ. We observed that Rb-depletion enhanced expression of actins and fibronectins suggesting Rb regulates the differentiation process.
Secondly, we investigated the consequences of myofibroblast differentiation in Head and Neck cancer. 120 oropharyngeal tumour cores in tissue microarrays were stained for smooth muscle actin (SMA), as a marker of myofibroblasts, and we show a strong correlation between high expression of SMA (myofibroblasts) and recurrent disease.
Currently, patients with recurrent Head and Neck cancer show a good response to EGFR inhibitors so investigations are under way to determine if SMA levels could be used to identify patients at risk of recurrence and perhaps use EGFR treatment at an earlier stage.
Conclusions: Rb is involved in myofibroblast differentiation and these cells show a strong association with recurrent disease.
Keywords: Oropharyngeal cancer, myofibroblasts, Retinoblastoma tumor suppressor gene (Rb)