Modulation of invasive properties of murine squamous carcinoma cells by heterologous expression of cathepsin B and cystatin C

Murine SCC-VII squamous carcinoma cells have the capacity to penetrate reco nstituted basement membranes (Matrigel) in vitro. The invasion of Matrigel layers by SCC-VII cells was significantly reduced by E-64, a specific inhib itor of lysosomal cysteine proteinases, The cathepsin-B-selective E-64 deri vative, CA-074, inhibited penetration of Matrigel by SCC-VII cells to the s ame extent, indicating a major role for this particular lysosomal enzyme in extracellular-matrix degradation during squamous-carcinoma-cell invasion. SCC-VII cells were stably transfected with a cDNA encoding human procatheps in B, in an attempt to modulate the invasive properties of the cell line. T he transfected cells expressed the heterologous gene, secreted increased am ounts of procathepsin B and displayed enhanced invasive potential, In vivo, the activity of cathepsin B is strictly regulated by endogenous inhibitors . SCC-VII cells were therefore also stably transfected with a cDNA encoding human cystatin C, the most potent cysteine-proteinase inhibitor in mammali an tissues. The expression of this transgene resulted in the production of active recombinant cystatin C and a pronounced reduction in Matrigel invasi on. These studies demonstrate that the invasive properties of squamous-cell carcinomas can be changed by modulation of the balance between cathepsin B and its endogenous inhibitors, and provide further evidence for the involv ement of this lysosomal cysteine proteinase in tumour invasion and metastas is. Int. J. Cancer, 83:526-531, 1999. (C) 1999 Wiley-Liss, Inc.