Tumor nercrosis factor-related apoptosis-inducing ligand (TRAIL)可以專一性的毒殺腫瘤細胞，而不會影響正常細胞，所以被認為是一個具有研究價值的抗癌藥物。TRAIL所引起的凋亡作用是透過與腫瘤細胞表面 DR4 和 DR5 等死亡受器的結合，但是存在於腫瘤細胞表面的 DcR1 與 DcR2 等干擾受器 (decoy receptor) 則會降低 TRAIL 對腫瘤細胞的毒殺作用。許多研究已經證實 PKC 活化對於保護細胞抵抗 TRAIL 引起的細胞凋亡扮演著重要的角色。在本實驗室先前研究分析了九株人類非小型肺癌細胞株對於 human recombinant TRAIL 的敏感程度，發現在 H1355 和 H520 對於 TRAIL 較不敏感的細胞株之中其 PKCε 有高度的表現量，然而在對 TRAIL 較具敏感性的 H460 和 H358 細胞株之中，其 PKCε 的表現量則相對降低。有文獻指出 PKCε 是一個致癌基因，為了更了解 PKCε 在肺癌細胞對 TRAIL 的敏感性中所扮演的角色，本實驗室先前研究發現在 H1355 和 H520 細胞株中抑制PKCε的表現量之後，會增加細胞對於 TRAIL 的敏感性。在本實驗之中，我們想更進一步了解 PKCε 在肺癌細胞株中所扮演的角色。首先我們將內生性 PKCε 表現量較低的 H460 肺癌細胞株轉染 Myr-PKCε 載體，發現增加 PKCε 的表現量會促進 survivin 的表現，同時會降低肺癌細胞株受到 TRAIL 所誘發的細胞凋亡比率，也會促進細胞的生長能力。在動物實驗中，我們得到促進腫瘤生長的相似結果。接著利用 siRNA 抑制 survivin 的表現後，恢復了 H460Myr-PKCε 細胞株對TRAIL 毒殺的感受性。綜合以上的結果推論，在 H460 細胞株中，過度表現 PKCε 可能會透過調控 survivin 的表現進而降低 TRAIL 所誘發的細胞凋亡。
Tumor nercrosis factor-related apoptosis-inducing ligand ( TRAIL ) is a promising anticancer agent as it selectively kills tumor cells but spares normal cells. TRAIL-induced apoptosis is mediated by binding with death receptors, DR4 and DR5, but the decoy receptors ( DcR1 and DcR2 ) expressed on the surface of tumor cells could interfere TRAIL-mediated apoptosis. Some reports indicated that PKC activation was an important factor for cell to protect apoptosis from TRAIL. Previously, we analyzed the sensitivity of nine human non-small lung cancer ( NSCLC ) cell lines to TRAIL. We found the protein expressions of PKCε are higher in TRAIL-resistant cell lines ( H1355 and H520 ). However, TRAIL-sensitive cell lines ( H460 and H358 ) express low levels of PKCε. Our previous studies demonstrated that down-regulation of PKCε expression by siRNA resulted in enhanced sensitivity to TRAIL in H1355 and H520 cell lines. In this research, we continued to investigate the role of PKCε in TRAIL-induced apoptosis of lung cancer cells. First of all, we transfected Myr-PKCε plasmid into H460 cell line in which endogenous PKCε expression is lower than other lung cancer cell lines tested. Then we found that overexpression of PKCε up-regulated survivin expression and reduced TRAIL-induced apoptosis. Furthermore, it would promote cell growth. Moreover, the similar tumor growth results were observed in animal model. Finally, we used siRNA to block survivin expression in H460 Myr-PKCε, The findings indicate that down-regulation of survivin confers sensitivity of H460Myr-PKCε cells to TRAIL. Thus, our results suggest that overexpression of PKCε decreased TRAIL-induced apoptosis in H460 lung cancer cells may via modulation of survivin expression.
