Down-regulating Of Cathepsin L Suppresses Cancer Invasion And Migration Via Inhibiting EMT

Objective: In this study, we clarify the mechanism of Cathepsin L in modulatingTGF-β–induced cell migration and invasion via the regulation of EMT.Methods: Besides cells treated with appropriate dose of TGF-β or not, we establishedCathepsin L knockdown A549and MCF-7cell lines by transfecting cells with Cathepsin LshRNA plasmids. Cell ability to migrate was measured by wound migration assay, and cellinvasion was detected by transwell invasion assay. The actin remodeling of tumor cells wasassessed with phalloidi. Reverse transcription-PCR (RT-PCR) and western blot served tostudy treatment effects on E-cadherin, N-cadherin and several signaling associated withEMT. Mice in tumor analysis group were sacrificed and tumors were removed for theexperiments. The expression level of E-cadherin and N-cadherin in transplantable tumorwas analyzed by immunohistochemical staining.Results: Wound migration and transwell invasion assays showed that silencing ofCathepsin L blocked TGF-β–induced cell migration, invasion. Moreover, we observed thatsuppression of Cathepsin L also noticeably suppressed TGF-β induced actin remodelingassociated with cell motility. The immunofluorescence (IF) and western blot analysisrevealed that the expression of E-cadherin decreased, while that of N-cadherin increased inTGF-β-treated cells, which showing the induction of EMT by TGF-β. Interestingly, EMT,induced by TGF-β, was clearly inhibited by Cathepsin L knockdown. Reversetranscription-PCR (RT-PCR) and western blot indicated that Cathepsin L knockdowninhibits EMT in A549and MCF-7cells, leading to the suppression of cell migration andinvasion. The mechanism of how Cathepsin L knockdown regulates EMT could beexplained by the suppression of EMT-inducing molecules, such as Snail, which isassociated with the PI3K-AKT and Wnt signaling pathways. In vivo studies, our resultsshowed that Cathepsin L knockdown significantly inhibited the xenograft tumor growth.Immunohistochemical staining showed that the expression of E-cadherin was increasedand N-cadherin was decreased, and the apoptosis was also increased in Cathepsin Lknock-down (shCathepsin L) tumor tissue. Conclusions: The effect of Cathepsin L knockdown on the suppression ofTGF-β–induced cell migration and invasion is associated with its regulation of EMT, andits mechanism could be explained by the suppression of EMT-inducing molecules, such asSnail, which is associated with the PI3K-AKT and Wnt signaling pathways.