The
actin-binding protein,
gelsolin, is a well known regulator of
cancer cell invasion. However, the mechanisms by which
gelsolin promotes invasion are not well established. As
reactive oxygen species (ROS) have been shown to promote
cancer cell invasion, we investigated on the hypothesis that
gelsolin-induced changes in ROS levels may mediate the invasive capacity of
colon cancer cells.Herein, we show that increased
gelsolin enhances the invasive capacity of
colon cancer cells, and this is mediated via
gelsolin's effects in elevating intracellular
superoxide (O2.-) levels. We also provide evidence for a novel physical interaction between
gelsolin and Cu/ZnSOD, that inhibits the enzymatic activity of Cu/ZnSOD, thereby resulting in a sustained elevation of intracellular O2.-. Using microarray data of human
colorectal cancer tissues from Gene Omnibus, we found that
gelsolin gene expression positively correlates with
urokinase plasminogen activator (uPA), an important matrix-degrading
protease invovled in
cancer invasion. Consistent with the in vivo evidence, we show that increased levels of O2.- induced by
gelsolin overexpression triggers the secretion of uPA. We further observed reduction in invasion and intracellular O2.- levels in
colon cancer cells, as a consequence of
gelsolin knockdown using two different siRNAs. In these cells, concurrent repression of Cu/ZnSOD restored intracellular O2.- levels and rescued invasive capacity.Our study therefore identified
gelsolin as a novel regulator of intracellular O2.- in
cancer cells via interacting with Cu/ZnSOD and inhibiting its enzymatic activity. Taken together, these findings provide insight into a novel function of
gelsolin in promoting
tumor invasion by directly impacting the cellular redox milieu.