| 摘要: | 腎臟癌是世界性的健康問題，2012年有338,000例新病例，約100,000例死亡（世界癌症研究基金國際）。腎臟癌無法治愈。傳統的放射療法和化學療法對腎癌無效。由於缺乏早期症狀，早期發現也很困難。 40-50％的腎癌患者發生轉移性疾病，其5年存活率僅為〜10％。因此我們迫切需要更深入了解腎臟癌的生物學。 研究ccRCC腫瘤形成的最佳模型之一是缺乏腫瘤抑制基因von Hippel Lindau（VHL）的細胞或組織。過去研究發現VHL基因的突變會引起囊性腎病和大部分透明細胞腎細胞癌（ccRCC）。高達70％的家族VHL突變攜帶者會得ccRCC。另外，在70-90％的偶發性ccRCC中有VHL功能喪失，包括體細胞突變和表觀遺傳缺陷。 因此，我們使用HOXB7-Cre-GFP驅動器在部分腎小管細胞中產生Vhlh（小鼠VHL基因名）的條件性剔除，其導致包含典型ccRCC的異常透明細胞的增生性病變。未預期的結果是，這些增生性病變伴有嚴重的發炎反應和纖維化。因此，這個小鼠模式為組織發炎症性腎病是RCC生成之風險因子的觀點提供了支持。最近我們又發現，Vhlh基因剔除腎臟中的組織炎症至少部分是VHL功能喪失細胞中代謝異常的結果。這種代謝異常導致內質網壓力和衍生的發炎反應。在上述研究期間，我們還注意到ITPR2基因功能可能是這種異常代謝誘導的腫瘤發生中的重要因子。 ITPR2是位於內質網膜上肌醇1,4,5-三磷酸（IP3）的受體。所以這是我們過去的研究的一個邏輯延伸，可將RCC發展與內質網壓力聯繫起來。通過它作為鈣從ER流向細胞質的流道功能，ITPR2是 內質網壓力的重要調節劑。 內質網中的鈣減少可以加重內質網壓力，因為內質網內特殊的chaperone需要鈣，所以鈣含量減少會使內質網壓力增大。重要的是，ITPR2最近被幾項研究指出為ccRCC的易感基因位點。我們相信我們最近的發現為這種關聯提供了機制理論基礎。因此我們提出四個具體目標來證明我們的假說：1.闡明ITPR2在VHL功能喪失的細胞中誘導內質網壓力和發炎反應中的作用。 2.闡明ITPR2在體細胞突變在腎細胞發炎反應中的功能意義。 3.闡明在VHL功能喪失細胞中誘導發炎反應的細胞因子機制。 4.闡明ITPR2在VHL突變體誘導的炎症和瘤形成中的體內作用。隨著我們不斷的研究，我們應該能進一步確定ccRCC啟動的關鍵組成部分，這可能成為可用藥目標。 ;Kidney cancer is a worldwide health concern, with 338,000 new cases diagnosed in 2012, and ~100,000 deaths (World Cancer Research Fund International). Kidney cancer has no cure. Traditional radiation- and chemo-therapies are ineffective against kidney cancer. Early detection is also difficult because of a lack of early symptoms. 40-50% of kidney cancer patients develop metastatic disease, for whom the 5-year survival rate is only ~10%. There is an urgent need for better understanding of the kidney cancer biology. One of the best models for studying ccRCC tumor formation are cells or tissues lacking the tumor suppressor gene von Hippel Lindau (VHL). Mutations of VHL gene have been shown to cause cystic kidney disease and a majority of the clear-cell renal cell carcinoma (ccRCC). Up to 70% of the carriers of germ line VHL mutations develop ccRCC. In addition, loss of VHL function, including somatic mutations and epigenetic defects, is found in 70-90% of sporadic ccRCC. We therefore generated conditional knockout of Vhlh （the mouse VHL locus) in a subset of kidney tubule cells using the HOXB7-Cre-GFP driver, which resulted in hyperplastic lesions containing abnormal clear cells typical of the ccRCC. Surprisingly, these hyperplastic lesions were accompanied by severe inflammation and fibrosis. It thus provides support for the notion that inflammatory kidney disease is a risk factor for RCC development. More recently we have also shown that the tissue inflammation in Vhlh knockout kidney is at least in part the result of metabolic abnormality in VHL loss-of-function cells. Such abnormality leads to ER stress and subsequent inflammatory response. During the study described above, we also noted the IPTR2 gene function that may be an important player in this abnormal metabolism-induced tumorigenesis. ITPR2 is the ER membrane-localized receptor of inositol 1,4,5-trisphosphate (IP3). This is a logical extension of our previous study in which we linked RCC development to ER stress, and ITPR2 is an important modulator of ER stress via its function as a calcium gate that allows calcium to flow from ER to the cytoplasm. Reduced calcium in the ER can exacerbate ER stress because ER-specific chaperon activity requires calcium. Importantly, ITPR2 has recently been noted as a susceptibility locus for ccRCC by several studies. We believe our recent findings provide a mechanistic base for such association. Four Specific Aims are proposed: 1. To elucidate the role of ITPR2 in VHL loss-of-function-induced ER stress and inflammatory responses in vitro. 2. To elucidate the functional significance of ITPR2 somatic mutations and germline polymorphism in inflammatory response in kidney cells. 3. To elucidate the cytokine program that induce the inflammatory response in VHL loss-of-function cells. 4. To elucidate the in vivo role of ITPR2 in VHL mutant-induced inflammation and neoplasia. With our continuing study, we should further identify critical components in ccRCC initiation, which may serve as druggable targets. |
