The functional analysis of Erc gene encoding GPI anchor protein

ERC(在肾癌中表达)是Eker(TSC2突变体)大鼠肾癌发生过程中的一个可诱导基因，是人间皮蛋白基因的同源基因。在TSC2基因敲除(KO)小鼠的肾癌细胞系中，ERC也过表达。为了阐明ERC在肾癌发生和间皮瘤中的功能重要性，我们在TSC2KO和ERC KO小鼠之间进行了基因交叉实验。然后，我们研究了ERC基因对TSC2杂合突变小鼠肾癌发生的影响。在携带野生型ERC的雄性和雌性TSC2杂合突变小鼠中，分别有32%和20%的小鼠在18个月龄时发生直径为4~30 mm的肾癌。相反，在ERC同源突变的TSC2杂合突变小鼠中，所有肾癌的直径都等于或小于2 mm。TSC2异源突变/ERC野生型小鼠与TSC2异源突变/ERC野生型小鼠肾脏肿瘤大小差异无统计学意义。这些结果提示ERC可能在肿瘤的增殖中起重要作用。此外，我们还建立了TSC2/ERC缺陷型肾癌细胞系，并将ERC-表达系统转入其中。通过过度表达ERC蛋白，细胞系与胶原涂层平板的粘附性增强。另一方面，当ERC的表达被RNA干扰抑制时，细胞的粘附性变差，这表明ERC在细胞与底物的粘连中发挥了作用。现在，我们正在通过将肾癌细胞系移植到裸鼠体内来进一步研究ERC的体内功能。

The Erc (expressed in renal carcinoma) was identified as an inducible gene during the renal carcinogenesis of the Eker (Tsc2 mutant) rat and is a homologue of the human Mesothelin gene. Erc is also overexpressed in the renal carcinoma cell line of the Tsc2 knockout (KO) mouse. To elucidate functional importance of Erc in renal carcinogenesis as well as in mesothelioma, we have performed genetic cross experiments between Tsc2 KO and Erc KO mice. Then we examined influence of the Erc genotype on the development of renal carcinomas in the Tsc2 hetero-mutant mouse. In 32% of male and 20% of female Tsc2 hetero-mutant mice with wild-type Erc, renal carcinomas with a diameter ranging from 4 to 30mm were developed by the age of 18 months. In contrast, all of the renal carcinomas in Tsc2 hetero-mutant mice with Erc homo-mutation had a diameter equal to or less than 2mm. There was no remarkable difference in the size of renal tumors between Tsc2 hetero-/Erc hetero-mutant and Tsc2 hetero-mutant/Erc wild-type mice. These results suggest that Erc may play an important role for tumor proliferation. In addition, we established Tsc2/Erc-deficient renal carcinoma cell lines and then transferred Erc-expression system into them. Adhesion of cell lines to the collagen-coated plate became stronger by overexpression of Erc protein. On the other hand, cell adhesive property was deteriorated when Erc expression was inhibited by RNA interference, suggesting that Erc has a role in the cell-substrate adhesion. Now we are further investigating in vivo function of Erc by implanting the renal carcinoma cell lines into the nude mouse.