The amount and proteolytic content of vesicles shed by human cancer cell lines correlates with their in vitro invasiveness

Cancer cells are known to shed extracellular membrane vesicles both in vitr o and in vivo. To analyse their possible involvement in the metastatic beha viour of tumours, we measured the Matrigel invasion capability and amounts of vesicles shed by four human tumour cell lines (8701-BC, MCF-7, MDA-MB-23 1 and HT-1080), and by MCF-10A, an immortalised human breast cell line. The proteolytic activity content of vesicles was analysed by gelatin and casei n zymographies. While MCF-10A cells do not release a measurable amount of v esicles, all tumour lines analysed, when cultured in presence of serum, she d vesicles rich in MMP-9. Other vesicle-associated proteinases include MMP- 2 and uPA. Amounts and proteolytic activities of shed vesicles correlate wi th the in vitro invasiveness of cells. Since vesicles appear to promote the proteolytic cascade required for the localised degradation of the extracel lular matrix their shedding from cancer cells might represent an important feature of tumour progression.