Tissue Rebuilding During Spontaneous Regression of Melanoma in the Melanoma-bearing Libechov Minipig.

Melanoma is a cancer disease with increasing incidence in the Caucasian population. It is often accompanied by spontaneous regression (SR), probably due to high immunogenicity. Understanding of this phenomenon could allow its induction in clinical practice, but detailed study in humans is impossible for ethical reasons. The aim of this study was to determine the role of fibronectin, tenascin C, and MMP-2 in the process of SR. Time-lapse study of SR was performed in the MeLiM (Melanoma-bearing Libechov Minipig) model. Skin melanomas were taken from 3 weeks to 8 months of age and immunohistochemically processed for fibronectin, tenascin C and matrix metalloproteinase-2 (MMP-2). Expression of all studied proteins increased up to the 10th week of age. Two structurally different areas were distinguishable from the 3rd month of age. MPP-2 expression predominated in areas with melanoma cells, whereas fibronectin and tenascin-C prevailed in the forming fibrous tissue. Rebuilding of melanoma into the fibrous tissue during SR was connected with a general rise in fibronectin and tenascin C expression.