Expression of human macrophage metalloelastase (MMP-12) by tumor cells in skin cancer

Matrix metalloproteinases play an essential role in tumor growth and invasi on. Different matrix metalloproteinases are often expressed in cancers with distinct patterns. To investigate the role of human macrophage metalloelas tase (MMP-12) in epidermal tumors, we studied human macrophage metalloelast ase mRNA and protein expression in malignant squamous cell and basal cell c arcinomas, and in premalignant Bowen's disease. Human macrophage metalloela stase was detected in 11 of 17 squamous cell carcinomas in epithelial cance r cells, whereas macrophages were positive in 15 of 17 samples. In basal ce ll carcinomas, human macrophage metalloelastase was more often found in mac rophages (seven of 19) than in cancer cells (four of 19). Human macrophage metalloelastase mRNA was also detected in three cell lines derived from squ amous cell carcinomas of the head and neck and in transformed HaCaT cells, whereas premalignant tumors and primary keratinocytes were negative for hum an macrophage metalloelastase mRNA. Western analysis revealed human macroph age metalloelastase protein in squamous cell carcinoma cells. Our results s how that human macrophage metalloelastase can be expressed in vivo and in v itro by transformed epithelial cells and indicate that the level of human m acrophage metalloelastase expression correlates with epithelial dedifferent iation and histologic aggressiveness.