| 摘要: | 腎細胞癌是腎臟最常見的惡性腫瘤，其中腎臟亮細胞癌 (clear cell renal cell carcinoma) 佔了大多數的腎細胞癌(75%)，而且超過30%的亮細胞癌病人常常在診斷時已經是晚期或者是合併其他器官轉移，除了臨床症狀不明顯之外，導致亮細胞癌高轉移發生率的詳細生理機轉並不清楚。本篇研究目的在於探討乳鐵蛋白在腎臟亮細胞癌中扮演的角色。藉由基因體計畫圖譜資料庫(The Cancer Genome Atlas, TCGA)，我們發現到乳鐵蛋白(Lactotransferrin)的基因(LTF)在腎臟亮細胞癌病人的腫瘤組織中出現明顯的下降，特別是在轉移的腎臟亮細胞癌組織中下降程度更為顯著。另外，從該資料庫中亦發現到組織中乳鐵蛋白表現量降低也是腎臟亮細胞癌預後不佳因子之一。為了探討乳鐵蛋白和腫瘤轉移相關性及機轉，利用細胞實驗進一步發現，乳鐵蛋白過度表現(overexpression)會降低高轉移特性的腎臟亮細胞癌細胞株ACHN的轉移能力，如果進行乳鐵蛋白基因抑制(knockdown)反而會增加低轉移特性細胞株A498的轉移能力。深入探討相關機轉部分，透過Gene set enrichment analysis(GSEA)分析和比較TCGA資料庫中低乳鐵蛋白表現合併淋巴轉移去對照高乳鐵蛋白表現但沒有淋巴轉移的腎臟亮細胞癌，將其相關機轉的高通量資料分析發現低乳鐵蛋白表現量合併淋巴移轉腫瘤組織中的上皮間質轉化(Epithelial-Mesenchymal Transition, EMT)路徑存在高度活化，在細胞實驗中也能印證相同的結論和發現。另外藉由實驗得知，不論是注射合成乳鐵蛋白在動物體內或是在細胞實驗中使用，都能有效地降低腎臟亮細胞癌的轉移能力，但若是在細胞實驗中敲除乳鐵蛋白的受體之一的低密度蛋白受器相關蛋白 (Lipoprotein receptor-related protein 1 , LRP1)，會進而導致先前所述的乳鐵蛋白抑制轉移能力會減弱。在TCGA資料庫中同樣也看到低乳鐵蛋白合併高LRP1表現會降低腎臟亮細胞癌病人存活率。總而言之，本篇研究創新發現乳鐵蛋白表現量對於腎臟亮細胞癌的轉移能力的影響以及可能透過LRP1受器去做調控，進而為未來腎臟亮細胞癌的治療帶來一線曙光。
Clear cell renal cell carcinoma (ccRCC) makes up near 75% of all renal cell carcinoma (RCC) cases, which is the most common type of kidney malignancy. More than 30% of RCC patients were diagnosed with metastasis causing significantly poor survival outcomes and poor response to the current therapeutic options. However, the molecular mechanism of high metastatic incidence in RCC patients remains unclear. Herein we introduced, LTF, encoding lactotransferrin, which was downregulated in primary ccRCC, and further suppressed in advanced ccRCC as well, compared to normal tissues derived from patients in The Cancer Genome Atlas (TCGA) database. Meanwhile, LTF downregulation is also referred to as a low prognostic factor in ccRCC patients. To further discover the mechanism of LTF downregulation promoting ccRCC metastasis, we demonstrated LTF downregulation inversely associated with the activation of the Epithelial-mesenchymal Transition (EMT) pathway in ccRCC patients by using Gene Set Enrichment Analysis (GSEA). In vitro, LTF overexpression suppressed the migration ability in high metastatic potential ccRCC cells (ACHN), while LTF knockdown enhanced cellular migration ability in A498 cells with less metastatic potential.
Furthermore, we also demonstrated recombinant LTF protein administration significantly inhibited the metastatic ability of ccRCC in vitro and in vivo, which its effect was prominently blocked by knockdown of lipoprotein receptor-related protein 1 (LRP1), in vitro. In addition, combined signature of downregulation of LTF and upregulation of LRP1 predicted poor overall survival in ccRCC patients from TCGA database. Our results showed the novelty with a potential mechanism which LTF may interact with LRP1 to inhibit ccRCC metastasis and revealed therapeutic potential of LTF protein in treating ccRCC patients. |
