Hou Ruida, Alemozaffar Mehrdad, Yang Baoxue, Sands Jeff M, Kong Xiangbo, Chen Guangping
Department of Urology, China-Japan Union Hospital, Jilin UniversityChangchun, China.
Department of Physiology, Emory University School of MedicineAtlanta, GA, USA.
Front Physiol. 2017 Apr 28;8:245. doi: 10.3389/fphys.2017.00245. eCollection 2017.
The urea transporter UT-B is widely expressed and has been studied in erythrocyte, kidney, brain and intestines. Interestingly, UT-B gene has been found more abundant in bladder than any other tissue. Recently, gene analyses demonstrate that SLC14A1 (UT-B) gene mutations are associated with bladder cancer, suggesting that urea transporter UT-B may play an important role in bladder carcinogenesis. In this study, we examined UT-B expression in bladder cancer with human primary bladder cancer tissues and cancer derived cell lines. Human UT-B has two isoforms. We found that normal bladder expresses long form of UT-B2 but was lost in 8 of 24 (33%) or significantly downregulated in 16 of 24 (67%) of primary bladder cancer patients. In contrast, the short form of UT-B1 lacking exon 3 was detected in 20 bladder cancer samples. Surprisingly, a 24-nt in-frame deletion in exon 4 in UT-B1 (UT-B1Δ24) was identified in 11 of 20 (55%) bladder tumors. This deletion caused a functional defect of UT-B1. Immunohistochemistry revealed that UT-B protein levels were significantly decreased in bladder cancers. Western blot analysis showed a weak UT-B band of 40 kDa in some tumors, consistent with UT-B1 gene expression detected by RT-PCR. Interestingly, bladder cancer associate UT-B1Δ24 was barely sialylated, reflecting impaired glycosylation of UT-B1 in bladder tumors. In conclusion, SLC14A1 gene and UT-B protein expression are significantly changed in bladder cancers. The aberrant UT-B expression may promote bladder cancer development or facilitate carcinogenesis induced by other carcinogens.
尿素转运体UT - B广泛表达，已在红细胞、肾脏、大脑和肠道中进行了研究。有趣的是，已发现UT - B基因在膀胱中的含量比任何其他组织都要丰富。最近，基因分析表明SLC14A1（UT - B）基因突变与膀胱癌相关，这表明尿素转运体UT - B可能在膀胱癌发生过程中起重要作用。在本研究中，我们用人原发性膀胱癌组织和癌衍生细胞系检测了膀胱癌中UT - B的表达。人UT - B有两种异构体。我们发现正常膀胱表达长形式的UT - B2，但在24例原发性膀胱癌患者中有8例（33%）缺失，或在24例中有16例（67%）显著下调。相比之下，在20个膀胱癌样本中检测到了缺少外显子3的短形式UT - B1。令人惊讶的是，在20个膀胱肿瘤中有11个（55%）鉴定出UT - B1外显子4中有一个24个核苷酸的框内缺失（UT - B1Δ24）。这种缺失导致了UT - B1的功能缺陷。免疫组织化学显示膀胱癌中UT - B蛋白水平显著降低。蛋白质印迹分析显示在一些肿瘤中有一条40 kDa的微弱UT - B条带，与通过逆转录 - 聚合酶链反应检测到的UT - B1基因表达一致。有趣的是，膀胱癌相关的UT - B1Δ24几乎没有唾液酸化，这反映了膀胱肿瘤中UT - B1的糖基化受损。总之，SLC14A1基因和UT - B蛋白表达在膀胱癌中发生了显著变化。UT - B的异常表达可能促进膀胱癌的发展或促进由其他致癌物诱导的致癌作用。
