Mutual paracrine effects of oral squamous cell carcinoma cells and normal oral fibroblasts: induction of fibroblast to myofibroblast transdifferentiation and modulation of tumor cell proliferation.

Several lines of evidence demonstrated that the stroma surrounding the tumors plays an important role in the growth and progression of several neoplasms, including oral squamous cell carcinomas (OSCC). We evaluated the presence of myofibroblasts in OSCC and determined whether their presence is associated with clinicopathological features of the tumors. We also investigated the mutual paracrine effects of tumor cells and myofibroblasts on fibroblast-myofibroblast transdifferentiation and tumor cell proliferation. Immunohistochemical analysis showed the approximately 60% of the OSCCs contained myofibroblasts in the stroma of the tumor. Abundant presence of myofibroblasts significantly correlated with N stage, disease stage, regional recurrence, and proliferative potential of the tumor cells. Using OSCC cell lines and primary oral normal fibroblasts (ONF), we demonstrated that tumor cells induced transdifferentiation of ONFs to myofibroblasts via secretion of transforming growth factor-beta 1 (TGF-beta 1). In turn, myofibroblasts secreted factors that stimulated OSCC cell proliferation, as revealed by measuring BrdU incorporation and Ki67 expression. The results of the study suggest that during tumor invasion OSCC-derived TGF-beta 1 promote fibroblast-myofibroblast transdifferentiation, and that tumor cellular proliferation can be induced by factors released from myofibroblasts, which may favor tumor growth.

Heterogeneous presence of myofibroblasts in hereditary gingival fibromatosis.

BACKGROUND/AIM: Hereditary gingival fibromatosis (HGF) fibroblasts are characterized by an increased production of collagen and transforming growth factor-beta1 (TGF-beta1), resulting in a fibrotic enlargement of the gingiva of affected patients. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. The goal of this article is to describe the presence of myofibroblasts in HGF in order to elucidate the mechanisms underlying HGF gingival overgrowth. MATERIALS AND METHODS: Fibroblast cell lines and gingival samples from patients of two distinct families affected by HGF and from normal gingiva (NG) were included in this study. To characterize the presence of myofibroblasts, the expression of specific myofibroblast marker smooth muscle isoform of alpha-actin (alpha-SMA) was examined by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and flow cytometric analysis. Immunohistochemistry against the alpha-SMA antigen was performed in the gingival tissue samples. RESULTS: Our results demonstrated a significant increase in the expression of the myofibroblast marker alpha-SMA in cells from one HGF family (designed as HGF Family 2), which are also characterized by an elevated expression of type I collagen, TGF-beta1 and connective tissue growth factor (CTGF). Additionally, alpha-SMA-positive cells were broadly detected in the gingival tissue samples from HGF Family 2 patients. In contrast, alpha-SMA expression by HGF Family 1 cells was quite similar to NG cells and no myofibroblasts were detected immunohistochemically, despite the higher levels of TGF-beta1 and type I collagen in HGF Family 1 fibroblasts than in NG cells. The expression of CTGF, which has been considered a key molecule to promote the transdifferentiation of myofibroblasts via TGF-beta1 activation, by HGF Family 1 cultures was significantly lower compared with HGF Family 2 and similar to NG control cells. CONCLUSIONS: Our results suggest that the presence of myofibroblasts in HGF could be dependent on CTFG expression levels, and different biological mechanisms may account for the gingival overgrowth observed in HGF patients. This could be an underlying reason for the high variable clinical expressivity of disease.