Role of matriptase-2 in human prostate cancer migration and invasion.

癌症轉移是導致癌症病人預後不佳及死亡率上升的主要原因。第二型細胞間質蛋白酶[(Matriptase-2 (MTX2)]，隸屬於第二型穿膜絲胺酸蛋白酶家族(TTPSs)，與第一型細胞間質蛋白酶[(Matriptase (MTX)]具高度相似性。先前報導指出MTX2可能抑制癌症細胞功能，然而其詳細的機制仍然不清楚。為了進一步探討MTX2如何抑制攝護腺癌細胞的移動與侵襲能力，我大量表達Matriptase-2在攝護腺癌細胞中(PC3 和DU-145)，並發現此蛋白酶可明顯地降低攝護腺癌細胞的侵襲和移動能力。因先前報導指出上皮細胞轉形成間葉細胞的過程(epithelial mesenchymal transition (EMT))在癌症的轉移進程中扮演重要的角色。利用QRT-PCR得知，在表達MTX2之PC3細胞中，EMT相關的轉錄因子基因(Twist, SIP-1)表現量都下降，且 MMP9 (Matrix metallopeptidase 9)的基因和活化程度也隨之降低，這些結果顯示MTX2可藉由改變EMT來抑制攝護腺癌細胞的移動能力。轉化生長因子β（TGF-β）已被報導為強效性的EMT促進者。而利用西方點墨法發現典型的TGF-β訊息傳導下游的Smad2及Smad3之蛋白質量和磷酸化程度因MTX-2的表達而下降。此外，上皮生長因子受體(EGFR)的磷酸化程度也隨之下降，因此而探討MTX-2是否可影響其他膜上蛋白酶，進而降低癌細胞的侵襲力，由於先前研究指出MTX與攝護腺癌細胞的轉移有很大的關係，我也探討MTX2和MTX之間是否會影響。結果顯示在表達MTX2的PC3細胞，MTX的基因和蛋白質表現量都是明顯的下降。同時MTX2會促進MTX被分泌到細胞外。綜合以上結果，MTX2可藉由降低TGF-β訊息路徑下游分子之活化，抑制EGFR磷酸化以及MTX的表達，故MTX2扮演具抑制攝護腺癌細胞侵襲的角色。Metastasis is often associated with a poor prognosis and isa leading cause of cancer mortality in prostate cancer. Matriptase-2 (MTX2) is a member of the type II transmembrane serine protease (TTSP) family and has a similar domain structure to matriptase which can enhance cancer cell invasion and migration. Some research results have indicated that MTX2 functions as a tumor suppressor. However, the molecular mechanisms by which MTX2 plays a negative role in prostate cancer are still unclear. In this study, examination the role of MTX2 in prostate cancer cell migration and invasion by ectopic expression of MTX2 in prostate cancer cells (PC3 and DU145). Data suggested that MTX2 reduced cell invasion and migration of PC3 and DU-145 cells. Moreover, MTX2 could down-regulate the mRNA levels of Twist, SIP-1, and the expression and gelatinolytic activity of MMP9, suggesting the involvement of MTX2 in altering an epithelial mesenchymal transition (EMT)-like event. Moreover, to further analyze if MTX2 was involved in modulating the TGF-β signaling pathway, a strong EMT inducer, we found that both protein and phosphorylation levels of TGF/BMP signaling effectors, Smad2 and Smad3, were decreased in MTX2-overexpressing cells. Furthermore, the ectopic expression of MTX2 also decreased the phosphorylation levels of epidermal growth factor receptor (EGFR), and was concurrent with a reduction of the gene and protein levels of matriptase, an oncogenic membrane-anchored serine protease in prostate cancer PC3 cells. Taken together, the data indicate that MTX2 functions as a suppressor of prostate cancer cell migration and invasion, at least in part via reducing the protein and phosphorylation levels of Smad2 and Smad3, the phosphorylation of EGFR, or the expression and activated levels of MTX