Gelatinase A expression and localization in human breast cancers. An in situ hybridization study and immunohistochemical detection using confocal microscopy.

The gelatinase A (72 kDa type IV collagenase) is a matrix metallo-proteinase which degrades basement membrane collagens. Various studies emphasize its role in stromal invasion of cancers, but there is some controversy about its origin. Gelatinase A was localized by immunohistochemistry using confocal microscopy in 15 human mammary carcinomas. In addition, the cells responsible for the synthesis of this enzyme were detected by in situ hybridization. Most invasive and non-invasive tumour cells were labelled by immunohistochemistry. Of particular interest was the pattern observed in some pre-invasive areas. Gelatinase A was found in fibroblasts in close contact with pre-invasive tumour clusters. Confocal observation allowed a more precise localization of gelatinase A to the periphery of tumour clusters along the basement membranes and in peritumour fibroblasts. The malignant epithelial cells were negative by immunohistochemistry in these areas. By in situ hybridization, mRNAs encoding gelatinase A were detected only in fibroblasts in close contact with pre-invasive and well differentiated tumour clusters. These findings support the hypothesis that peritumour fibroblasts produce gelatinase A and that breast cancer cells may bind this enzyme to their cell surface and/or internalize it.