Section of Urology, Department of Surgery, The University of Chicago, Chicago, IL 60637, USA.
Urol Oncol. 2012 Jul-Aug;30(4):415-20. doi: 10.1016/j.urolonc.2010.03.002. Epub 2011 Dec 11.
The stress-activated MAP kinases (SAPK) signaling pathways play a critical role in the cellular response to toxins and physical stress, mediate inflammation, and modulate carcinogenesis and tumor metastasis. The stress-activated MAP kinases (MAPK) c-Jun N-terminal kinase (JNK) and p38 are activated upon phosphorylation by a widely expressed and conserved family of upstream MAP kinase kinases (MAP2K). Signaling mediated by p38 and JNK has well-established importance in cancer, yet the contribution of this pathway in urothelial bladder cancer is not understood. This study evaluated stress-activated MAP kinase pathway expression in cell lines derived from human urothelial carcinomas.
Total protein lysates from a panel of human urothelial bladder cancer cell lines (RT4, T24, UMUC-3, J82, 5637, 253J, and 253J-BV) were analyzed by immunoblotting for the JNK and p38 MAPKs, as well as MKK3, MKK4, MKK6, and MKK7. Quantitative real time PCR was utilized to determine mRNA expression levels of the MAP2Ks. Stress stimuli (sorbitol, hydrogen peroxide, and UV irradiation) were used to active p38, which was measured by phospho-antibody.
Although protein levels were variable, all cell lines expressed p38 and JNK. On the other hand, with the exception of the well-differentiated cell line RT4, each cell line had a reduction or absence of expression of one or more MAP2K. 253J and 253J-BV exhibited no expression of MKK6, even when an excess of protein was queried. mRNA levels indicated that both transcriptional and post-transcriptional mechanisms are involved in the regulation of MAP2Ks. Decreased MAP2K expression correlated with decreased ability to activate p38 in response to stress stimuli.
Aberrant MAP2K protein expression indicates that altered cellular signal transduction mediated via JNK and p38 may be common in bladder cancer. Down-regulation of MAP2Ks likely occurs at both the transcriptional and post-transcriptional levels. Consistent with the known function of p38 and JNK in apoptosis, defects in normal pathway function caused by decreased expression of upstream MAP2Ks may provide a survival advantage to bladder cancer cells. Further investigations should focus on identifying a functional role for these pathways in bladder cancer development.
应激激活的丝裂原活化蛋白激酶（SAPK）信号通路在细胞对毒素和物理应激的反应中起着关键作用，介导炎症，并调节致癌作用和肿瘤转移。应激激活的丝裂原活化蛋白激酶（MAPK）c-Jun N-末端激酶（JNK）和 p38 通过广泛表达和保守的上游 MAP 激酶激酶（MAP2K）家族的磷酸化而被激活。p38 和 JNK 介导的信号转导在癌症中具有重要的作用，然而在尿路上皮膀胱癌中，该途径的作用尚不清楚。本研究评估了源自人尿路上皮膀胱癌细胞系的细胞中应激激活的 MAP 激酶通路表达。
用人尿路上皮膀胱癌细胞系（RT4、T24、UMUC-3、J82、5637、253J 和 253J-BV）的蛋白提取物进行免疫印迹分析，以检测 JNK 和 p38 MAPK 以及 MKK3、MKK4、MKK6 和 MKK7 的表达。利用定量实时 PCR 确定 MAP2Ks 的 mRNA 表达水平。用 sorbitol、H2O2 和 UV 照射等应激刺激物激活 p38，并用磷酸化抗体测量 p38 的活性。
尽管蛋白水平存在差异，但所有细胞系均表达 p38 和 JNK。另一方面，除了分化良好的细胞系 RT4 外，每个细胞系都减少或缺乏一种或多种 MAP2K 的表达。253J 和 253J-BV 甚至在大量蛋白被检测时也没有表达 MKK6。mRNA 水平表明，MAP2Ks 的调控涉及转录和转录后机制。MAP2K 表达降低与应激刺激后 p38 激活能力降低相关。
异常的 MAP2K 蛋白表达表明，通过 JNK 和 p38 介导的细胞信号转导改变可能在膀胱癌中很常见。MAP2Ks 的下调可能发生在转录和转录后水平。与 p38 和 JNK 在细胞凋亡中的已知功能一致，上游 MAP2Ks 表达减少导致正常通路功能缺陷，可能为膀胱癌细胞提供生存优势。进一步的研究应集中于确定这些通路在膀胱癌发展中的功能作用。
