Basal caspase-3 activity promotes migration, invasion, and vasculogenic mimicry formation of melanoma cells.

Melanoma is the least common but most serious form of skin cancer. The leading cause of death in melanoma patients is widespread metastasis caused by increased cell motility and a rich blood supply for tumor cells. A unique form of microcirculation called vasculogenic mimicry, which efficiently supplies blood to tumor cells, has been reported recently. Apoptosis-related protein performs a nonapoptotic function to promote migration and invasion of tumor cells. This study focuses on the nonapoptotic role of caspase-3 in melanoma and its effects on the migration, invasion, and vasculogenic mimicry formation of melanoma cells. Human melanoma samples were used to detect active caspase-3 expression and determine its relationship with clinicopathologic parameters. In addition, a human melanoma A375 cell line was used to determine the role of caspase-3 in migration and invasion using z-DEVD-fmk, a selective caspase-3 inhibitor, to inhibit caspase-3 activity. The findings suggest that active caspase-3 is expressed in nonapoptotic melanoma cells and is related to metastasis and vasculogenic mimicry formation in patients with melanoma. Low doses of caspase-3 inhibitor reduced caspase-3 activity without affecting cell apoptosis. Inhibition of caspase-3 activity using low-dose z-DEVD-fmk decreased the migration, invasion, and vasculogenic mimicry formation of melanoma cells in vitro. Similarly, downregulation of caspase-3 by specific small interfering RNA also inhibited the migratory, invasive, and tube-forming potential of melanoma cells. The caspase-3-mediated promotion of melanoma cell motility may be because of the cleavage of matrix metalloproteinase-2.