Clusterin 是一種分泌型的醣蛋白，具有增加細胞聚集的能力，普遍存在於組織及人類體液中。在我們的研究結果得知，clusterin 表現高的 H1355 肺癌細胞株對化療藥物 Doxorubicin、Gemcitabine 及 Taxotere 的感受性呈現較不敏感的反應。而後，利用短暫轉染 clusterin siRNA 的方法，抑制了 H1355 細胞株的 clusterin 蛋白表現，則會使 H1355 細胞株對化療藥物的感受性變為較敏感的情形，可見細胞死亡率增加。接著，我們篩選出穩定大量表現 clusterin 的 H1299 和 A549 肺癌細胞株，亦發現對化療藥物 Doxorubicin 具低感受性的情形。為了得知影響肺癌細胞對化療藥物的感受性為位在細胞質中的 sCLUc 蛋白還是成熟會分泌到細胞外的 sCLUs 蛋白的作用，則利用 clusterin 表現低的 H1299 細胞株，分為控制組是不含 sCLUs 蛋白的新鮮培養液及實驗組是含有 sCLUs 蛋白的 H1355 之 conditioned medium，處理化療藥物，觀察 H1299 細胞株對化療藥物 Doxorubicin、Gemcitabine 及 Taxotere 的感受性變化，實驗結果間接證明了是分泌至細胞外的 clusterin 蛋白 (sCLUs) 具有保護細胞的作用，使得肺癌細胞對化療藥物感受性變差，而我們有純化出 sCLUs 蛋白，之後可外加至細胞培養液中，直接證明就是 sCLUs 蛋白的作用，保護細胞對化療藥物感受性低。另外，我們也利用穩定大量表現 clusterin 的 H1299 和 A549 細胞株，探討 clusterin 對肺癌細胞移行的影響。從實驗結果得知，clusterin 會抑制肺癌細胞的爬行能力，特別是在 H1299 細胞株較有明顯的移行能力受抑制的情形。
我們認為 clusterin 在肺癌治療及轉移上扮演著重要的角色，或許將來可當作在肺癌臨床上的指標蛋白之一，而對於 clusterin 之作用機制尚未清楚，是值得往後再深入探討的方向。
Clusterin is a secretory glycoprotein that can be found in all human fluids and enhances protection as well as aggregation of a variety of cells in vitro. To investigate the role of clusterin in lung cancer, the expression of clusterin was examined with various lung cancer cell lines followed by drug sensitivity assay. We found that H1355 cells which express a large amount of clusterin were less sensitized to doxorubicin, gemcitabine and taxotere. Inhibition of H1355 cells clusterin expression by transiently transfected clusterin siRNA resulted in enhanced chemosensitivity to doxorubicin, gemcitabine and taxotere in vitro. The clusterin stably overexpression clones of H1299 and A549 cells were selected by G418 antibiotics and treated with chemotherapeutic drugs for cytotoxicity assay. Our data showed that the clusterin stably overexpression cells reduced sensitive to doxorubicin. To study whether secreted clusterin protein has a protection role in cancer cells, conditioned medium that contained clusterin was collected from H1355 cells and combined with chemotherapeutic drugs to treated H1299 cells. The results indicated that H1299 cells in conditioned medium were less sensitive to doxorubicin, gemcitabine and taxotere than in fresh medium. Therefore, indirect evidences showed that secreted clusterin is protective and decreased the cytotoxicity of chemotherapeutic drugs for lung cancer cells. Moreover, we also purified secreted clusterin protein to confirm the protective function of secreted clusterin directly. In addition, we investigated the effect of clusterin in cell migration and found that the clusterin stably overexpression clones migrated slowly. The data indicated that high amount of clusterin expression may inhibit lung cancer cells migration.
Our data suggested that clusterin plays an important role in the drug susceptibility and metastasis of lung cancer cells. Clusterin could be a target protein for lung caner therapy. However, the regulation mechanism of clusterin in lung cancer is not clear that deserve further investigation.
