人類攝護腺癌細胞中ErbB-2訊息活化間質蛋白酶原之研究

Abstract

隨著攝護腺癌的病期演進，原本較為良性的癌細胞會變得更加惡性，引發癌細胞轉移以及賀爾蒙非依賴型性，進而造成癌症治療上的困難。過去的臨床研究顯示，ErbB家族中的酪氨酸激酶受體，ErbB-2，在攝護腺癌與其他各種癌症的病期演變中，扮演促進細胞癌化的角色。在攝護腺癌細胞株中，ErbB-2活化程度在代表攝護腺癌晚期、賀爾蒙非依賴型的LNCaP C-81細胞中較高，而在代表攝護腺癌早期、賀爾蒙依賴型的LNCaP C-33細胞中則較低，與臨床研究結果相符合。有趣的是，第二型穿膜絲氨酸蛋白酶–間質蛋白酶，其活化程度同樣在LNCaP C-81細胞中較高，而在LNCaP C-33細胞中則較低；此結果說明間質蛋白酶在攝護腺癌的病期演變中可能扮演著重要角色，並且也暗示著ErbB-2訊息傳遞與間質蛋白酶原活化之間的關聯性。 在本研究中，我們發現在LNCaP C-33細胞中大量表現ErbB-2時，會導致間質蛋白酶的活化增加；而降低LNCaP C-81細胞中ErbB-2的表現量與活性時，則會使間質蛋白酶的活化下降。此外，我們更進一步利用PI3K與MEK的抑制劑去研究ErbB-2下游的路徑，結果顯示，在大量表現ErbB-2的LNCaP C-33細胞中，PI3K的抑制劑LY294002能夠有效抑制間質蛋白酶的活化；反之，使用MEK的抑制劑PD98059則沒有顯著的效果。另外，在細胞生長曲線、傷痕實驗、細胞遷移與細胞侵襲實驗中，我們觀察到當間質蛋白酶的表現與活化受到抑制時，大量表現ErbB-2的LNCaP C-33細胞的侵入能力會明顯降低，但其生長力與移動力卻沒有顯著變化。綜合上述結果，我們可以得知，在人類攝護腺癌細胞中，ErbB-2的訊息能透過PI3K/Akt路徑而促進間質蛋白酶的活化，並因此而增加細胞的侵襲能力。

During prostate cancer progression, cancer benign cells are able to convert into malignancy with an increase in tumorigenicity, metastasis and androgen-independence, leading to a poor prognosis. It has been shown that ErbB-2, a receptor tyrosine kinase of the ErbB family, plays a carcinogenic role in progression of a variety of cancers including prostate cancer. The tyrosine phosphorylation of ErbB-2 increases in androgen-independent LNCaP C-81 cells, compared to androgen-dependent LNCaP C-33 cells. Interestingly, activation of matriptase, a type II transmembrane serine protease, is up-regulated in LNCaP C-81 cells rather than LNCaP C-33 cells, which implies the role of matriptase in prostate cancer progression and a correlation between the ErbB-2 signaling and matriptase activation. In the studies, we observed that the activation status of matriptase is elevated in ErbB-2-overexpressing LNCaP C-33 cells, and knockdown of endogenous ErbB-2 in LNCaP C-81 cells was able to decrease matriptase activation. In further investigation of downstream pathways, the results showed that a PI3K inhibitor LY294002 but not a MEK inhibitor PD98059 suppressed matriptase activation in ErbB-2-overexpressing LNCaP C-33 cells. Moreover, in the cell growth curve, wound healing assay, transwell migration and invasion assay, we found that matriptase knockdown in ErbB-2-overexpressing LNCaP C-33 cells was able to reduce cell invasion but had no significant effect on their cell proliferation and cell motility. Taken together, these results suggest that ErbB-2 signaling promotes matriptase zymogen activation through PI3K/Akt pathway in human prostate cancer cells, which contributes to an invasive ability.