SUMMARYTumor cell-derived collagenase stimulatory factor (TCSF) stimulates in vitro the biosynthesis of various matrix metalloproteinases involved in tumor invasion, such as interstitial collagenase, gelatinase A, and stromelysin 1. The expression of TCSF mRNAs was studied in vivo, using in situ hybridization and Northern blotting analysis, in seven normal tissues and in 22 squamous cell carcinomas of the lung, and in seven benign proliferations and in 22 ductal carcinomas of the mammary gland. By in situ hybridization, TCSF mRNAs were detected in 40 of 44 carcinomas, in pre-invasive and invasive cancer cells of both lung and breast cancers. TCSF mRNAs and gelatinase A mRNAs were both visualized in the same areas in serial sections in breast cancers, and were expressed by different cells, tumor cells, and fibroblasts. The histological results were confirmed by Northern blot analysis, which showed a higher expression of TCSF mRNAs in cancers than in benign and normal tissues. These observations support the hypothesis that TCSF is an important factor in lung and breast tumor progression.

The expression of various matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in 88 primary bronchopulmonary cancers and in 13 neighbouring pulmonary parenchyma samples was quantified by Northern-blot analysis, and morphologically examined by in situ hybridization and immunohistochemistry in order to evaluate the involvement of MMPs in the pathophysiology of these carcinomas and to look for potential markers of aggressivity of lung tumours. Northern-blot analysis showed that the predominantly expressed MMPs in bronchopulmonary cancers were gelatinase A (66%), its activator MT1-MMP (membrane-type-1 matrix metalloproteinase) (56%) and stromelysin-3 (61%). MMP expression frequencies and mRNA levels increased progressively with malignant phenotype, lack of differentiation and TNM stage of the tumours, whereas TIMP expression decreased very early during tumour progression. Moreover, the principal MMPs were significantly co-expressed in primary tumours, suggesting their co-regulation. Morphological studies revealed the expression of MMPs and TIMPs essentially in stromal cells in close contact with tumour clusters. These results indicate that tumour progression in bronchopulmonary carcinomas implies a progressive disruption of the MMP/TIMP balance leading to an excess of several MMPs that act in concert in vivo. Furthermore, the fact that stromal cells are the principal source of MMPs emphasizes the close cooperation between host cells and cancer cells in tumour invasion.

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