EBAG9/RCAS1 expression enhances tumor growth in renal cell carcinoma

前言与目的：EBAG9基因是一种雌激素应答基因，最近发现EBAG9基因与RCAS1基因相同，可以诱导T、B、NE细胞等免疫细胞的凋亡，使肿瘤细胞逃避免疫监视。在本研究中，我们利用动物模型提供了EBAG9/RCAS1可能调控肿瘤进展的潜在机制的证据。方法：我们在体内外比较了EBAG9转染人RencA细胞和空载体转染人RencA克隆的细胞生长情况。我们进一步用免疫组织化学方法检测了78例肾癌组织中EBAG9/RCAS1的表达。统计分析EBAG9/RCAS1表达与临床病理特征的相关性。结果：EBAG9过表达对细胞培养中的Renca克隆生长无促进作用。另一方面，将EBAG9基因转导的RencA细胞接种于Balb/c小鼠的侧翼，建立S…与载体对照组相比，肿瘤明显增大(1712.1±506.4 mm^3比366.2±110.1 mm^3，p=0.0055)。携带EBAG9转基因Renca细胞肿瘤的小鼠的存活率明显低于携带对照肿瘤的小鼠。在Balb/c小鼠体内生长的EBAG9表达肿瘤的组织学检查中，TUNEL法未见凋亡淋巴细胞阳性染色。免疫组织化学显示肿瘤周围CD8淋巴细胞数量减少(10.0个/10HPF比5.8/10HPF)。以上结果提示，EBAG9在肿瘤细胞中的表达可能通过抑制肿瘤浸润性CD8淋巴细胞而发挥免疫抑制作用。免疫组织化学分析显示，78例原发性肾细胞癌中68例(87.2%)胞浆内可见强而弥漫免疫染色。与之相反，EBAG9/RCAS1在邻近正常组织中表达较弱。EBAG9/RCAS1阳性表达与T分期和血管侵犯显著相关(p=0.0017和p=0.0109)。EBAG9/RCAS1高表达患者的肿瘤特异性生存率明显低于EBAG9/RCAS1低表达患者。多因素分析显示EBAG9/RCAS1高表达是影响肿瘤特异性生存的独立预后因素(p=0.0485)。结论：EBAG9/RCAS1在大多数人肾细胞癌中表达，EBAG9/RCAS1高表达与肿瘤侵袭性和预后不良有关。较少

Introduction and Objectives : The EBAG9 was previously identified as an estrogen responsive gene, and it was lately revealed that the EBAG9 is identical with RCAS1 which induces apoptosis of immune cells such as T, B, and NE cells, and which allows tumor cells to escape of tumors from immune surveillance. In this study, we provide evidence that EBAG9/RCAS1 may modulate the potential mechanism of tumor progression using animal models.Methods : We compared the cell growth of human EBAG9-transfected renca cells with empty vector-transfected renca clones in vitro and in vivo. We further examined expression of EBAG9/RCAS1 immunohistochemically in 78 renal cell carcinoma specimens. We statistically analyzed correlation between EBAG9/RCAS1 expression and clinicapathological characteristics.Results : Overexpression of EBAG9 had no stimulatory effect on the growth of renca clones in cell culture. On the other hand EBAG9-transfected renca cells implanted in the flank of Balb/c mice established s … More ignificantly enlarged tumors compared with vector controls (1712.1±506.4 mm^3 vs. 366.2±110.1 mm^3, p=0.0055). Mice bearing tumors of EBAG9-transfected renca cells had significantly worse survival than animals bearing control tumors. Histological examination of EBAG9-expressing tumors grown in Balb/c mice did not show apoptotic lymphocytes positively stained by TUNEL assay. However, immunohistochemiclal analysis revealed the number of CD8 lymphocytes around tumors decreasing (10.0 vs. 5.8 /10HPF). These data suggested that EBAG9 expression in tumor cells may contribute to the suppression of immune response by inhibiting tumor-infiltrating CD8 lymphocytes without apoptosis. Immunohistochemical analysis showed that strong and diffuse immunostaining in the cytoplasm was identified in 68/78 (87.2%) of primary renal cell carcinoma cases. In contrast, weak-EBAG9/RCAS1 expression was observed in the adjacent normal tissue. Positive EBAG9/RCAS1 immunostaining in the primary cancers significantly correlated with advanced pathological T stages and vascular infiltration (p=0.0017 and p=0.0109, respectively). Patients with high EBAG9/RCAS1 immunoreactivity had significantly worse cancer-specific survival than those with low EBAG9/RCAS1 expression. Multivariate analysis revealed that high EBAG9/RCAS1 expression was an independent prognostic predictor for cancer-specific survival (p=0.0485).Conclusions : EBAG9/RCAS1 is expressed in the majority of human renal cell carcinomas and high EBAG9/RCAS1 immunoreactivity is associated with tumor aggressiveness and unfavorable prognosis. Less