SPARC基因表達在鼻咽癌和肝癌中之功能分析

Abstract

為了研究鼻咽癌的腫瘤形成機制 (tumorigenicity)，我們使用互補去氧核糖核酸微矩陣分析 (cDNA microarray analysis) 訊息核糖核苷酸 (mRNA) 在鼻咽癌細胞和正常鼻黏膜上皮細胞之間的表現量。我們找出了一些有差異性表現的基因。SPARC (也稱做骨連接蛋白) 是在這些非常有趣的基因群的其中一個。用及時定量聚合酶連鎖反應 (quantitative real-time RT-PCR) 和西方墨點法分析SPARC的訊息核糖核苷酸及蛋白質在鼻咽癌、肝癌和其他腫瘤細胞株、正常上皮細胞的表現情況，並用外科手術取下的檢體做免疫染色，我們發現SPARC的訊息核糖核苷酸及蛋白質在鼻咽癌和肝癌細胞株及外科手術檢體的腫瘤細胞表現相當的少，但在正常上皮細胞及一些間質細胞有適當的表現。當藉由四環黴素 (Tetracyclin) 去誘導的 (Tet-On) 載體 (pBIG2i) 含有SPARC的互補去氧核糖核酸建構，去感染鼻咽癌和肝癌的細胞而建立之穩定細胞株，去研究SPARC的蛋白質在這些細胞株的功能。可以發現這個基因在體外培養及動物體內實驗都會部分的抑制腫瘤細胞的生長、侵犯和誘導死亡。然而，在帶有SPARC基因表現的免疫不全老鼠中，這個基因只能輕微的抑制腫瘤轉移的活性。SPARC會抑制腫瘤細胞的生長及轉移的調控是藉由提高RECK基因表現，及降低bFGF基因的表現。由此可下個推論，SPARC基因在鼻咽癌和肝癌的腫瘤形成機制中扮演一個類似抑制制癌基因的角色。

To investigate nasopharyngeal carcinoma (NPC) tumorigenicity, we used cDNA microarray analysis of mRNA expression between NPC cell lines and normal nasal mucosa epithelial cells. We have identified some altered expressed genes. In which one of the very interested genes is SPARC (also called osteonectin). By quantitative real-time RT-PCR and Western blot analysis of SPARC mRNA and protein expressions in NPC, HCC and other tumor cell lines, normal epithelial cell types, and immunostaining of surgical specimens, we found that SPARC mRNA and protein expressions are relatively weakly expressed in NPC and HCC cell lines and tumor cells in surgical specimens, but well expressed in normal epithelial cells and some stromal cells. When a tet-on plasmid (pBIG2i) containing SPARC-cDNA was constructed and transfected to the NPC and HCC cells to establish the stable lines, the function of SPARC protein in these lines were investigated. It was found that this gene could partially inhibit tumor cell proliferation, invasion and induce apoptosis in vitro and in vivo. However, in SCID mice bearing SPARC (+) NPC xenograft, tumor metastatic activity was mildly inhibited by this gene. The regulation of suppressive effect of SPARC on tumor cell proliferation and invasion is due to up-regulation of RECK and down-regulation of bFGF gene expression. It is concluded that SPARC gene play a role as an oncosuppressor-like gene in NPC and HCC tumorigenesis.