探討CD74誘導人類透明細胞型腎細胞癌之增殖與轉移角色及調控機轉:促進D型血管內皮生長因子過度表現

Effects of CD74 on Proliferation and Metastasis in Human clear Cell Renal Cell Carcinoma: Involvement of Vascular Endothelial Growth Factor-D Upregulation

呂郁蕙(Yu-Huei Liu)

指導教授 ： 林榮耀

國立臺灣大學/醫學院/生物化學暨分子生物學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.10128

摘要

根據國際癌症研究署 (International Agency for Research on Cancer, IARC) 於 2002 年發表全球癌症發生率、死亡率及及盛行率統計資料 GLOBALCAN 2002，估計腎臟癌於 2002 年新增病例達 208,000 例，佔全世界罹癌人口數1.9%；同時 2002 年因腎臟癌死亡的病例達 102,000 例。腎臟癌在澳洲、歐洲與美洲有最高的發生率。其好發程度，歐洲國家發生率佔排名第九位，美國成年男性排名第七位、成年女性排名第九位。在台灣，根據行政院衛生署2007年度統計資料，有 522 例死於腎臟癌, 其好發程度於成年男性排名第十三位、成年女性排名第十四位。比較全世界腎臟癌發生率與死亡率人口分佈結果發現，成年男性罹癌人口約為成年女性 1.5 倍。雖然已有報告認為吸煙、肥胖、以及環境因子，如砷皆與腎臟癌發生有關，但真正的罹癌原因仍有待研究。
透明細胞型腎細胞癌是主要的成年癌症型態，約佔總腎臟癌發生率的約70 %，透明細胞型腎細胞癌以腫瘤細胞引起的血管新生以及其高密度的微小血管網為特點。研究已經揭示引起透明細胞型腎細胞癌的主要的原因是由於 von Hippel-Lindau (VHL) 抑癌因子的突變，引起缺氧因子 hypoxia-inducible factor-α(HIF-α)的過度活化，進而導致 A 型血管表皮生長因子的過度表現。然而目前標的於表皮生長因子接受器 (EGFR) 或 A 型血管表皮生長因子 (VEGF-A) 的臨床試驗用藥其抑癌作用有限。此外，近來陸續發表的研究認為腎臟癌的發生與慢性發炎反應有關，但目前機制仍眾說紛紜。儘管如此，發現癌症治療的新標的，並針對該新標的設計新癌症療法或複合療法，成為目前生物醫學研究重點之一。
CD74 的過度表現與許多人類癌症有關，其中包括透明細胞型腎細胞癌，然而其間的關聯性仍屬未知之數。在本篇論文中。為了釐清 CD74 在透明細胞型腎細胞癌致癌過程中所扮演的角色，我們將 CD74 穩定表現於人類腎臟胚胎細胞株 HEK293 中，或抑制人類轉移性透明細胞腎臟細胞株 Caki-1 中高度表現之 CD74，藉以探討 CD74 致癌潛力。結果顯示 CD74 調控 D 型血管表皮生長因子 (VEGF-D) 表現，於人類透明細胞型腎細胞癌組織中發現其二者表現呈現顯著正相關 (r = 0.65，p<0.001). 小鼠實驗中並發現 CD74 促進腫瘤增生、增加腫瘤細胞引起的血管新生，並且促進腫瘤細胞轉移。細胞實驗顯示抑制 CD74 或 VEGF-D 表達導致抑制細胞增生、侵犯以及癌細胞引起的血管內皮細胞遷移。進一步探討 CD74 促進VEGF-D 過度表現之機制發現 CD74 藉由活化 PI3K/AKT 及 MEK/ERK 途徑而促使NF-kB 轉錄因子轉位至細胞核中，結合 VEGF-D 促進子而活化 VEGF-D 的表現。這些結果表明 VEGF-D 對 CD74 引起的人類透明細胞型腎細胞癌之增生與轉移至關重要。

關鍵字

CD74 ； D 型血管表皮生長因子 ； 人類透明細胞型腎細胞癌

並列摘要

According to GLOBALCAN 2002, the recent estimates of the cancer incidence, mortality and prevalence of all the countries of the world, worldwide about 208,000 new cases of kidney cancer have been diagnosed (1.9% of the world total), and 102,000 persons died because of kidney cancer in 2002. Kidney cancer has the highest rates in America, Australia and Europe. Kidney cancer is the 9th most common cancer in the European Union and the 7th most common cancer in men and the 9th in women in the United States. In Taiwan, there are 522 persons died because of kidney cancer in 2007, which is the 14th most common cause of cancer death in men and the 13th in women. Incidence and mortality rates are approximately 1.5 fold as high for men as for women worldwide. Although some factors, such as tobacco smoking, obesity, and environmental chemicals especially arsenic have been thought to be involved in tumorigenesis of kidney cancer, the precise mechanism needs to be identified.
Clear cell renal cell carcinoma (ccRCC) is the most common kidney cancer (~70%) in adults, which characterized by a high microvascular density produced by tumor-induced neoangiogenesis. Studies have revealed that the major cause of ccRCC is due to loss of the von Hippel-Lindau (VHL) gene, which causes an upregulation of hypoxia-inducible factor-alpha (HIF-alpha) activity, and subsequencely leads to overexpression of VEGF-A. The other groups suggest that link between chronic inflammation and carcinogenesis may play an important role in renal cell carcinoma (RCC), but are not well understood. The undergoing therapies for metastatic ccRCC that include the use of the tyrosine kinase inhibitors as well as anti-EGFR and anti-VEGF agents demonstrate minimal efficacy, therefore to discover new targets for combined cancer therapy is required.
Elevation of CD74 is associated with a number of human cancers, including clear cell renal cell carcinoma (ccRCC). To understand the role of CD74 in the oncogenic process of ccRCC, we ectopically expressed CD74 in human embryonic kidney 293 cells (HEK/CD74) and evaluated its oncogenic potential. By overexpression of CD74 in HEK293 and Caki-2 cells, and downregulation of CD74 in Caki-1 cells, we show that VEGF-D expression is modified accordingly. A significant, positive correlation between CD74 and VEGF-D is found in human ccRCC tissues (Pearson’s correlation, r= 0.65, p<0.001). In HEK/CD74 xenograft mice, CD74 significantly induced the formation of tumor masses, increased tumor-induced angiogenesis, and promoted cancer cell metastasis. Blockage of VEGF-D expression by small interference RNA resulted in a decrease in cell proliferation, invasion and cancer cell-induced HUVEC migration enhanced by CD74. Furthermore, we provide evidence that the intracellular signaling cascade responsible for VEGF-D upregulation by CD74 is both PI3K/AKT- and MEK/ERK-dependent, both of which are associated with NF-kappaB nuclear translocation and DNA-binding activity. These results suggest that VEGF-D is crucial for CD74-induced human renal carcinoma cancer cell tumorigenesis.

並列關鍵字

CD74 ； VEGF-D ； clear cell renal cell carcinoma

參考文獻

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