Expression of gelatinase A and TIMP-2 mRNAs in desmoplastic fibroblasts in both mammary carcinomas and basal cell carcinomas of the skin.

AIMS To compare the localisation of mRNAs for the basement membrane degrading enzyme gelatinase A (72 kilodalton type IV collagenase) and its inhibitor TIMP-2 in carcinomas of the breast and basal cell carcinomas of the skin which have little or no ability to metastasize. METHODS In situ hybridisation was performed on formalin fixed, paraffin wax embedded blocks using 35S-labelled riboprobes on 16 mammary carcinomas, three fibroadenomas, and a benign phyllodes tumour, and on 15 basal cell carcinomas of the skin (BCC). RESULTS Labelling for both mRNAs was detectable in 14 of 16 mammary carcinomas and in 13 of 15 BCC, most often over organising desmoplastic fibroblasts in the stroma around invasive epithelial aggregates. Some sparse labelling was seen over malignant epithelial cells in six of the mammary carcinomas but not in the BCC. Some expression of gelatinase A mRNA was also seen in fibroblasts of breast lobules adjacent to the mammary carcinomas and around engulfed adnexal elements in the BCC, but not in unaffected breast tissues, fibroadenomas, the phyllodes tumour or unaffected skin. CONCLUSIONS Maximal expression of gelatinase A and TIMP-2 mRNAs occurs in malignant neoplasms as part of the host response to the presence of established neoplastic cells rather than as an initial response to invasion. The degree to which this is present suggests this may be a highly relevant mechanism modulating tumour differentiation, growth and progression, possibly entailing uptake via specific receptors on the tumour cell surface.