2015年10月13日,國際著名學術期刊The Journal of Clinical Investigation於在線發表了中國科學院上海生命科學研究院生物化學與細胞生物學研究所王紅豔研究組的最新研究成果「STK4 regulates TLR pathways and protects against chronic inflammation–related hepatocellular carcinoma」(highlighted in JCI)。該工作揭示巨噬細胞利用激酶STK4抑制Toll-樣受體(TLR)介導的炎症反應,降低慢性炎症導致肝癌的發生發展;並創新性提出巨噬細胞內STK4作為炎性肝癌的診斷標誌物,相關工作已經申請中國專利。
肝癌是世界上發病高、嚴重影響生存質量的一類癌症。其中,慢性遷延性炎症和抑癌基因的缺失是導致肝癌發生的重要原因。前期鑑定的眾多抑癌基因調控肝癌細胞增殖或凋亡的機理已經明確。鑑於一些抑癌基因同樣在免疫細胞中表達,王紅豔研究組致力於篩選出在免疫細胞和腫瘤細胞中兼具抑炎抑癌雙重功能的重要基因,進而通過靶向免疫細胞和腫瘤細胞中共同的信號分子,發揮高效阻斷炎癌變(尤其是炎症相關肝癌的)的發生發展。
在王紅豔研究員的指導下,博士生李偉芸、肖俊等檢測了病原微生物感染的原代巨噬細胞內抑癌基因的表達情況,發現絲氨酸和蘇氨酸激酶STK4(又稱Mst1)的表達顯著下調。STK4通過結合和磷酸化IRAK1,促進IRAK1降解,從而抑制NF-kB的活化及下調促炎因子IL-6、IL-1b和腫瘤壞死因子α(TNFα)的產生。此外,STK4促進抗病毒I型幹擾素的產生。而且,通過分析大量臨床病人數據,發現肝癌病人的腫瘤組織出現大量的巨噬細胞浸潤,並且腫瘤浸潤巨噬細胞或外周血中的巨噬細胞中低水平的STK4與高水平的IRAK1的表達亦呈現負相關;與血清IL-6低水平的肝癌病人相比,僅血清IL-6高水平的病人的巨噬細胞特異性的下調STK4的表達。
在利用致癌劑DEN、CCl4結合LPS或E.coli誘導的慢性炎症相關肝癌的小鼠模型中,在巨噬細胞特異性敲除STK4的小鼠顯著促進炎症因子的表達,加重肝功能損傷,進而在晚期引起小鼠肝纖維化,促進肝腫瘤形成。更重要的發現是利用IRAK1抑制劑處理的小鼠,明顯降低由於STK4缺失導致的慢性炎症和肝癌的發生發展。此工作指出將STK4-IRAK1作為阻斷炎性肝癌發生的新靶點,並首次提出通過監測外周血巨噬細胞內STK4水平,輔助早期診斷炎性肝癌的新策略。
本研究工作的合作者包括武漢病毒研究所魏濱研究員、復旦大學陶無凡教授、上海生化與細胞所惠利健研究員、湖北腫瘤醫院聶磊醫生、上海仁濟醫院季福醫生和東方肝膽外科醫院張海濱醫生。該工作得到了自然科學基金委、科技部、中科院研究經費的支持。
在外界細菌感染的情況下,巨噬細胞中STK4表達降低,引起IRAK1不能被磷酸化降解而持續性活化下遊的NF-κB信號通路,並抑制IRF-3活化,最終導致炎症因子上調和IFN-β表達下降,進一步促進炎性肝癌發生發展的過程。(生物谷Bioon.com)
生物谷推薦的英文文獻:
doi:10.1172/JCI81203.
STK4 regulates TLR pathways and protects against chronic inflammation–related hepatocellular carcinoma
Weiyun Li1, Jun Xiao1, Xin Zhou1, Ming Xu2, Chaobo Hu1, Xiaoyan Xu1, Yao Lu1, Chang Liu1, Shengjie Xue1, Lei Nie3, Haibin Zhang4, Zhiqi Li5, Yanbo Zhang1, Fu Ji2, Lijian Hui1, Wufan Tao6, Bin Wei7,8, and Hongyan Wang1
Hepatocellular carcinoma (HCC) is frequently associated with pathogen infection–induced chronic inflammation. Large numbers of innate immune cells are present in HCCs and can influence disease outcome. Here, we demonstrated that the tumor suppressor serine/threonine-protein kinase 4 (STK4) differentially regulates TLR3/4/9-mediated inflammatory responses in macrophages and thereby is protective against chronic inflammation–associated HCC. STK4 dampened TLR4/9-induced proinflammatory cytokine secretion but enhanced TLR3/4-triggered IFN-β production via binding to and phosphorylating IL-1 receptor–associated kinase 1 (IRAK1), leading to IRAK1 degradation. Notably, macrophage-specific Stk4 deletion resulted in chronic inflammation, liver fibrosis, and HCC in mice treated with a combination of diethylnitrosamine (DEN) and CCl4, along with either LPS or E. coli infection. STK4 expression was markedly reduced in macrophages isolated from human HCC patients and was inversely associated with the levels of IRAK1, IL-6, and phospho-p65 or phospho-STAT3. Moreover, serum STK4 levels were specifically decreased in HCC patients with high levels of IL-6. In STK4-deficient mice, treatment with an IRAK1/4 inhibitor after DEN administration reduced serum IL-6 levels and liver tumor numbers to levels similar to those observed in the control mice. Together, our results suggest that STK4 has potential as a diagnostic biomarker and therapeutic target for inflammation-induced HCC.