Funakoshi-Tago Megumi, Moriwaki Takuro, Ueda Fumihito, Tamura Hiroomi, Kasahara Tadashi, Tago Kenji
Department of Hygienic Chemistry, Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan.
Department of Hygienic Chemistry, Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan.
Cell Signal. 2017 Feb;31:41-57. doi: 10.1016/j.cellsig.2016.12.008. Epub 2016 Dec 28.
The JAK2 V617F mutant-mediated aberrant signaling pathway is a hallmark of myeloproliferative neoplasms (MPNs). Although cytokine-inducible Src homology 2 protein (CIS) and suppressors of cytokine signaling (SOCS) are negative regulators of the JAK-STAT pathway, the functional role of CIS/SOCS family members in the JAK2 V617F mutant-induced oncogenic signaling pathway has not yet been elucidated. In this study, we found that the expression of CIS and SOCS1 was induced through the activation of signal transducer and activator of transcription 5 (STAT5) in not only the cells stimulated with Epo or IL-3 but also the cells transformed by the JAK2 V617F mutant. Cell proliferation and tumor formation in nude mice induced by the JAK2 V617F mutant were significantly enhanced when the expression of CIS was silenced using an RNA interference technique, whereas the knockdown of SOCS1 had no effect. The enforced expression of CIS caused apoptotic cell death in the transformed by JAK2 V617F mutant and drastically inhibited the JAK2 V617F mutant-induced tumor formation. CIS interacted with phosphorylated EpoR at Y401, which was critical for the activation of STAT5 and ERK. Whereas the activation of STAT5 and ERK in the transformed cells by JAK2 V617F mutant was increased by the knockdown of CIS, the enforced expression of CIS reduced the activation of these molecules. Furthermore, these anti-tumor effects of CIS required the function of SH2 domain and its tyrosine phosphorylation at Y253. We herein elucidated the mechanism by which CIS functions as a novel type of tumor suppressor in JAK2 V617F mutant-induced tumorigenesis.
JAK2 V617F突变介导的异常信号通路是骨髓增殖性肿瘤（MPN）的一个标志。尽管细胞因子诱导的Src同源2蛋白（CIS）和细胞因子信号抑制因子（SOCS）是JAK-STAT通路的负调节因子，但CIS/SOCS家族成员在JAK2 V617F突变诱导的致癌信号通路中的功能作用尚未阐明。在本研究中，我们发现，不仅在用促红细胞生成素（Epo）或白细胞介素-3（IL-3）刺激的细胞中，而且在由JAK2 V617F突变转化的细胞中，CIS和SOCS1的表达都是通过信号转导和转录激活因子5（STAT5）的激活来诱导的。当使用RNA干扰技术使CIS表达沉默时，JAK2 V617F突变诱导的裸鼠细胞增殖和肿瘤形成显著增强，而敲低SOCS1则没有效果。CIS的强制表达导致JAK2 V617F突变转化的细胞发生凋亡性细胞死亡，并显著抑制JAK2 V617F突变诱导的肿瘤形成。CIS与Y401位点磷酸化的促红细胞生成素受体（EpoR）相互作用，这对STAT5和细胞外信号调节激酶（ERK）的激活至关重要。虽然敲低CIS可增加JAK2 V617F突变转化细胞中STAT5和ERK的激活，但CIS的强制表达则降低了这些分子的激活。此外，CIS的这些抗肿瘤作用需要SH2结构域的功能及其Y253位点的酪氨酸磷酸化。我们在此阐明了CIS在JAK2 V617F突变诱导的肿瘤发生中作为一种新型肿瘤抑制因子发挥作用的机制。
