STEM CELLS AND HEPATOCARCINOGENESIS

描述(来自申请者)：在最频繁研究的致癌模型之一--化学肝癌发生中，一个长期悬而未决的问题是，肝细胞癌的起源细胞是什么？Emmanuel Farber倡导的经典细胞途径是，肝细胞癌从改变的肝细胞逐渐发展到病灶和癌前结节。然而，对早期出现在肝癌发生过程中的卵圆细胞的研究表明，肝细胞癌可能起源于位于末端导管内的“两极”肝祖细胞或位于导管附近的多能前体细胞。此外，最近对接受男性捐赠者骨髓移植的雌性小鼠和大鼠的研究表明，肝干细胞有两种可能的来源：来自末端导管中的双极祖细胞或来自导管周围干细胞。进一步推测，这些导管周围祖细胞可能来源于循环中的骨髓干细胞，或者分化为肝细胞，或者骨髓细胞与肝细胞融合。在具体目标1中，申请人建议建立一种表达绿色荧光蛋白的转基因Fischer大鼠系，作为骨髓移植研究的供体。在具体目标2中，三种癌变模型：a.连续DEN，其特征是肝细胞癌之前的改变的肝细胞灶很少或没有卵圆形细胞，将被用来确定肝细胞癌是否起源于肝细胞；b.Solt-Farber模型，其特征是导管内卵圆形细胞的显著增殖，以确定肝癌是否起源于双极导管前体细胞；c.胆碱缺乏-乙硫氨酸模型，其特征是卵圆细胞在导管周围的增殖，将被用于确定癌前病变或肝癌是否起源于门静脉周卵圆细胞。在每一种方案中，DDPIV-(管状酶)雌性大鼠将接受DDPIV+，EGFP+，男性捐赠者的骨髓移植。对增殖有反应的细胞群体的来源将通过供体或受体标记的存在以及适当时通过肝脏谱系和沿海细胞标记识别的细胞类型来确定。在具体目标3中，将测试供体骨髓干细胞与受体肝细胞融合的可能性，并确定在肝细胞癌的病因、进展或转移方面融合的可能性。了解癌症的细胞起源对于了解癌症如何演变和制定预防策略至关重要。

Description (from applicant): One of the long standing unanswered questions in one of the most frequently studied models of carcinogenesis, chemical hepatocarcinogenesis, is what is the cell of origin of hepatocellular carcinomas (HCC)? The classic cellular pathway, championed by Emmanuel Farber, is that HCC develop from altered hepatocytes progressively through foci and preneoplastic nodules. However, studies on oval cells, which appear early during hepatocarcinogenesis, indicate that HCC may arise from "bipolar" liver progenitor cells located within terminal ducts or from pluripotent progenitor cells located adjacent to the ducts. In addition, recent studies on female mice and rats receiving bone marrow transplants from male donors indicated two possible origins of liver stem cells: from bipolar progenitor cells in the terminal ducts or from periductal stem cells. It is further postulated that these periductal progenitor cells may arise from circulating bone marrow stem cells either by differentiation into liver cells or that bone marrow cells may fuse with liver cells. In Specific Aim 1, the applicant proposes to develop a transgenic Fischer rat line expressing EGFP which can be used as a donor for bone marrow transplantation studies. In Specific Aim 2, three models of carcinogenesis: a. Continuous DEN, which features foci of altered hepatocytes preceding HCC with little or no oval cells will be used to determine if HCC arise from hepatocytes; b. Solt-Farber model, which features prominent proliferation of ductal oval cells to determine if HCC arise from bipolar ductal precursor cells; c. Choline-deficiency-ethionine, a model which features periductular proliferation of oval cells will be used to determine if preneoplastic lesions or HCC arise from periportal oval cells. In each of these protocols, DDPIV- (canalicular enzyme) female rats will receive a bone marrow transplant from DDPIV+, EGFP+, male donors. The origin of the populations of cells responding by proliferation will be identified by the presence of donor or recipient markers, and the types of cells identified through labeling with both liver lineage and littoral cell markers, when appropriate. In Specific Aim 3, the possibility of fusion of donor bone marrow stem cells with recipient liver cells will be tested and the possibility of fusion in etiology, progression or metastasis of HCC determined. Knowledge of the cellular origin of cancer is critical for understanding how cancer evolves and for developing prevention strategies.