Clin. Exp. Metastasis, 1993, 11, 183-189 Expression of activated gelatinase in human invasive breast carcinoma P. D. Brown, R. E. Bloxidge, E. Anderson* and A. Howellt British Bio-technology Ltd, Oxford and *Tumour Biochemistry Laboratory and "~CRC Department of Medical Oncology, Christie Hospital, Manchester, UK (Received 11 June 1992; accepted in revised form 10 November 1992) The expression of both 92- and 72-kDa gelatinases has been studied in 20 samples of human breast carcinoma by the technique of gelatin zymography. This technique allowed the relative amount of each gelatinase to be determined in small samples of tissue (<10 mg). More importantly, active and latent forms of the two gelatinases were resolved. Two samples (10-20 mg) were cut from each piece of tumour in order to monitor the variability of gelatinase distribution within that section of tumour. The 72-kDa latent progelatinase was present in 15 of the 20 tumours, with trace amounts in two others. The 62-kDa activated form of this gelatinase was detected in all 15 of the tumours in which the latent form was present. The 92-kDa latent progelatinase was present in 11 of the 20 tumours, with trace amounts in four others. However, the 82-kDa activated form of this gelatinase was only clearly detected in two tumours, although three others showed the presence of trace amounts. The ratio of active to latent forms of the 72-kDa gelatinase ranged from 0.9 to 3.6. There were no marked correlations between gelatinase expression and established staging and prognostic markers. Analysis of three samples of fibroadenoma revealed only very low levels of gelatinase expression. On the basis of these results, activation of the 72-kDa progelatinase appears to be a more common event in invasive breast carcinoma than activation of the 92-kDa progelatinase. However, neither proteinase showed a correlation with metastatic progression, as measured by lymph node involvement. Keywords: collagenase, human carcinoma, matrix metalloproteinase, metastasis Introduction Matrix metalloproteinases have been linked to the invasive phenotype of tumour cells through both correlative and functional studies, and it has been proposed that these enzymes are responsible for the breakdown and remodelling of basement mem- brane and interstitial matrix that is an integral part of tumour invasion and metastasis [1,2]. The ex- pression of matrix metalloproteinase activity is tightly regulated. Net activity is determined by the amount of proenzyme expressed, the extent to which this proenzyme is activated, and the local Address correspondence to: Dr P. D. Brown, British Bio- technology Ltd, Watlington Road, Cowley, Oxford OX4 5LY, UK. Tel: (0865) 748747; fax: (0865) 781115. concentration of native inhibitors, tissue inhibitor of metalloproteinases, TIMP-1 and TIMP-2 [3]. Matrix metalloproteinase expression has been de- monstrated in a variety of human tumours, inclu- ding breast carcinoma, by both immunohisto- chemical analysis [4] and mRNA hybridization [5,6]. Although these studies have shown the presence of matrix metalloproteinase in invasive carcinoma, neither technique is able to resolve the activated species from latent proenzyme. The tech- nique of zymography offers a simple yet sensitive means of resolving these forms, and thereby pro- vides additional data on the relationship between metalloproteinase activity and tumour progression. The principle of the technique is the separation of proteinases according to molecular weight, © 1993 Rapid Communications of Oxford Ltd Clinical & Experimental Metastasis Vol 1! No 2 183