Signal Transducers and Activators of Transcription (STAT) Regulatory Networks in Marine Organisms: From Physiological Observations towards Marine Drug Discovery

Part of our ocean’s richness comes from its extensive history of supporting life, resulting in a highly diverse ecological system. To date, over 250,000 species of marine organisms have been identified, but it is speculated that the actual number of marine species exceeds one million, including several hundreds of millions of species of marine microorganisms. Past studies suggest that approximately 70% of all deep-sea microorganisms, gorgonians, and sea sponges produce secondary metabolites with anti-cancer activities. Recently, novel FDA-approved drugs derived from marine sponges have been shown to reduce metastatic breast cancer, malignant lymphoma, and Hodgkin’s disease. Despite the fact that many marine natural products have been shown to possess a good inhibition potential against most of the cancer-related cell signaling pathways, only a few marine natural products have been shown to target JAK/STAT signaling. In the present paper, we describe the JAK/STAT signaling pathways found in marine organisms, before elaborating on the recent advances in the field of STAT inhibition by marine natural products and the potential application in anti-cancer drug discovery.     

家蚕JAK/STAT信号通路相关基因克隆与分析

【目的】鉴定家蚕JAK/STAT信号通路组成原件,并预测家蚕JAK/STAT信号通路主要相关基因的功能。【方法】在电子克隆的基础上,通过RT-PCR获得家蚕JAK/STAT信号通路的主要相关基因;利用在线软件对相关蛋白进行结构域分析;基于microarray数据库或qPCR分析各基因的组织表达特征。【结果】克隆了家蚕JAK/STAT信号通路主要相关基因,包括BmSTAT、BmHOP、BmSOCS2、BmSOCS5A、BmSOCS5B、BmSOCS6、BmDRK、Bmken、BmPIAS1、BmPIAS2以及BmPI3K,但没有能克隆到果蝇Upd1、Upd2和Upd3的同源体基因。序列分析显示BmHOP具CRD_FZ、Kringle、转膜区域和PKc超家族蛋白激酶催化结构域TyrKc;BmSTAT有2种亚型,均具SH2、STAT_bind、STAT_int和STAT_alpha结构域;在克隆的BmSOCS家族的3个基因中,BmSOCS2A和BmSOCS6A具典型的SH2和SOCS结构域;BmDRK由SH3和SH2两种结构域形成了SH3-SH2-SH3串联结构;BmKen存在BTB和锌指结构域,BmPIAS1和BmPIAS2具有LCR结构域,BmPI3K具有2个SH2结构域。【结论】成功克隆了家蚕JAK/STAT信号通路主要相关基因。相关蛋白的保守结构域分析显示,在家蚕JAK/STAT信号通路中,BmHOP是JAK激酶的一种,可以磷酸化BmSTAT转录因子,激活靶基因转录;BmSOCS、Bmken、BmPIAS1以及BmPIAS2对JAK/STAT通路起负反馈作用。     

miR-24-3p targeting KLF6 gene affects viability and apoptosis of esophageal cancer cells via IL-6/STAT3 signaling pathway

AIM: To investigate the effect of microRNA-24-3p (miR-24-3p) on the viability and apoptosis of esophageal cancer cells. METHODS: The expression of miR-24-3p and KLF6 mRNA in the esophageal cancer cells TE11, Eca109 and EC9706 were detected by RT-qPCR. The protein expression of KLF6 was determined by Western blot. EC9706 cells were transfected with anti-miR-24-3p and KLF6 siRNA. The cell viability was measured by MTT assay, the apoptotic rate was analyzed by flow cytometry, and the proliferation, apoptosis and IL-6/STAT3 signaling pathways related proteins were determined by Western blot. The level of IL-6 was measured by ELISA. The dual luciferase reporter gene assay was used to verify the relationship between miR-24-3p and KLF6. RESULTS: The levels of miR-24-3p were up-regulated in the esophageal cancer cells TE11, Eca109 and EC9706 (P < 0.05), and the expression of KLF6 at mRNA and protein levels was down-regulated (P < 0.05). Knock-down of miR-24-3p expression inhibited the cell viability, induced apoptosis, and inhibited the protein levels of CDK4, cyclin D1, CDC25A, p-STAT3, Bcl-2 and IL-6, and promoted the protein expression of caspase-3 and Bax in EC9706 cells. CONCLUSION: miR-24-3p targets KLF6 gene to affect the viability and apoptosis of esophageal cancer cells by regulating IL-6/STAT3 signaling pathway.     

Roles of PI3K/Akt and JAK2/STAT3 signaling pathways in protection of SO2 against limb ischemia/reperfusion-induced acute lung injury in rats

AIM: To investigate the role of PI3K/Akt and JAK2/STAT3 pathways in the protection of sulfur dioxide (SO₂) against limb ischemia/reperfusion (I/R)-induced acute lung injury (ALI) in rats. METHODS: ALI was induced by limb I/R in the SD rats. Na₂SO₃(0.54 mmol/kg, ip)/NaHSO₃ (0.18 mmol/kg, ip) as SO₂ donor was injected at 20 min before reperfusion. The inhibitors of JAK2/STAT3 and PI3K/Akt pathways, Stattic (3 mg/kg, iv) and LY294002(40 mg/kg, iv), respectively, were injected at 1 h before reperfusion. Peripheral blood and lung tissues were collected for determining the contents of the cytokines, the protein levels of the molecules related to the signaling pathways, apoptosis and histopathologic changes by ELISA, TUNEL and Western blot. RESULTS: Compared with control group, the content of MDA, the activity of MPO, lung coefficient, apoptotic index, cytokine expression, and the protein levels of p-Akt and p-STAT3 in I/R group all increased significantly, and administration of Na₂SO₃/NaHSO₃ attenuated the damage in the lung. Besides, the results of Western blot showed that the rat lung tissues expressed p-STAT3 protein and p-Akt protein. After I/R, the protein levels of p-STAT3 and p-Akt were increased. After using Na₂SO₃/NaHSO₃, p-Akt was increased, but p-STAT3 was decreased (P<0.05). CONCLUSION: Both JAK2/STAT3 and PI3K/Akt pathways are likely involved in the protective effect of SO₂ against limb I/R-induced ALI in rats. The activation of JAK2/STAT3 signaling pathway increases I/R injury. Reversely, the activation of PI3K/Akt signaling pathway reduces I/R injury. Besides, JAK2/STAT3 and PI3K/Akt signaling pathways may have crosstalk during I/R-induced ALI and JAK2/STAT3 pathway may have an impact on the P13K/Akt pathway.     

Proportion of CD14+CD16+ monocytes in peripheral blood from patients with type 2 diabetic mellitus and effect of LPS and IL-15 on expression of STAT5 in monocytes

AIM: To characterize the proportion of CD14⁺CD16⁺ monocytes in peripheral blood from type 2 diabetes (T2DM) patients and to observe the response of CD14⁺CD16⁺ monocytes to lipopolysaccharide (LPS) and interleukin-15 (IL-15) for further exploring the potential mechanism of inflammatory immune response in the pathogenesis of T2DM. METHODS: Twenty-eight patients with T2DM and 20 healthy volunteers were enrolled in the study. The peripheral blood was collected for determining the percentage of CD14⁺CD16⁺ monocytes by flow cytometry. The peripheral blood mononuclear cells (PBMC) were isolated and subject to stimulation with LPS and IL-15 for 4 h. The protein expression of STAT5 was detected by Western blotting and the phosphorylated (p)-STAT5 was determined by Western blotting and immunofluorescence. Serum levels of 25-hydroxyvitamin D₃ and IL-6, and the concentrations of IL-6 and monocyte chemoattractant protein-1(MCP-1) in the culture supernatants were assessed by ELISA. Serum level of C-reactive protein (CRP) was measured by immunoturbidimetry. RESULTS: There were positive correlations between the quantity of CD14⁺CD16⁺ monocytes and serum levels of CRP and IL-6 (r=0.394, P<0.05 and r=0.741, P<0.01), while serum 25 (OH) D₃ was negatively correlated with the quantity of CD14⁺CD16⁺ monocytes (r=-0.409, P<0.01), serum CRP(r=-0.479,P<0.01) and serum IL-6 (r=-0.774,P <0.01). After stimulated with LPS and IL-15, PBMC showed significant up-regulation of p-STAT5 protein expression, and significant increases in the supernatant levels of IL-6 and MCP-1 were observed (P<0.05). The expression of p-STAT5 existed in the nucleus.CONCLUSION: These findings suggest that the functional disturbance in monocytes occurs in T2DM, which may be related to insufficiency of vitamin D₃. The aberrant activation of STAT5 signaling pathway underlies the functional abnormalities of the monocytes in T2DM.