Investigation Of The Role And Mechanism Of IL6、TNFα And TNFR1 In Oval Cell Proliferation And Inflammation-associated HCC

Section 1 Investigation of the role and mechanism of IL6 and TN FR1 mediated signaling pathway in liver regeneration of DDB1F/F, Mx1-Cre+/- mouseLiver is an solid organ with high capability of regeneration. Through the live r parenchymal cells, hepatocytes, could re-enter cell cycle and mediate liver rege neration. Under most pathological conditions, the regeneration capability of hepat ocytes is impaired. Therefore, liver progenitor cells, also termed oval cells, were induced and differentiated into hepatocytes and biliary cells to replenish liver ma ss Previous studies suggested IL6, TNFa and its receptor TNFR1 are involved in oval cell mediated liver regeneration. But controversial results always exist. Con ventionally, chemical reagents were used to induce oval cells proliferation in mo use. However, these traditional methods have some defects for investigating oval cells. Furthermore, recent studies demonstrated that liver regeneration is mediated by hepatocytes rather than oval cells in chemicals injury models. In present wor k, we revaluated the role of IL6, TNFa and its receptor TNFR1 in oval cell pro liferation and liver regeneration using DDB1F/F,Mx1-Cre+/- mouse model. The resu Its showed that upregulation of IL6 in the regenerative course of DDB1F/F,Mxl-C re+/-mouse. Significantly restricted oval cell proliferation was observed in DDB1F /F, Mx1-Cre+/-,IL6-/- mouse. And newborn DDB1 positive hepatocytes were also si gnificantly reduced at 4 and 6 weeks after poly(I:C) injection in DDB1F/F,Mxl-Cr e+/-,IL6-/- mouse. Q-PCR results suggested one way by which IL6 promotes oval cells proliferation was upregulating TWEAK and HGF, who are important for ov al cell activation and proliferation. In contrast to IL6, TNFR1 knockout did not affect oval cell proliferation and liver regeneration in DDB1F/F,Ax1-Cre+/- mouse. TNFa, the major ligand of TNFR1, its expression was also not varied much post poly(I:C) injection. Therefore, TNFa/TNFRl signaling pathway is not associated with oval cell proliferation and liver regeneration in DDB1F/F,Mcl-Cre+/- mouse.Section 2 Investigation of the role and mechanism of IL6, TNFa and TNFRl in HCC development of DDB1F/F,Alb-Cre+/- mouseHCC is a kind of malignant cancer with high incidence. It is the second dea dly cancer and more than 50% HCC patients lived in China. Therefore, it is val uable to understand the mechanism and factors contribute to HCC pathology. The development of HCC is highly correlated with inflammation, about 90% HCC d eveloped in the context of chronic hepatitis. Cytokines, which are important in i nflammation, whose dyregulation in HCC patients has been observed. Among the m, TNFa and IL6 are paid more anttention and widely investigated.The role and function of IL6, TNFa and TNFR1 in HCC were systematic inv estigated in chemical-induced murine HCC model. However, HCC developed with out preceeding inflammation is a main defect of this model. Especially consideri ng the involvement of IL6, TNFa and TNFR1 in inflammation. By knocking out or overexpressing certain genes, inflammation-associated HCC models have been established, including mdr2-/- mouse, LTα/β transgenic mouse and our DDB1F/F,A lb-Cre+/- mouse model. In present work, we explored the role and underlying me chanism of IL6, TNFα and TNFR1 in HCC development in DDB1F/F,Alb-Cre+/-mouse. The results showed that more DDB1F/F,Alb-Cre+/-,IL6-/- mice developed vi sible tumors at the age of 18 months, implies that IL6 knockout could accelerate HCC development. Through no difference of tumor incidence was observed bet ween DDB1F/F,Alb-Cre+/-,IL6-/- and DDB1F/F,Alb-Cre+/- mouse at the age of 21 m onths. The maximum tumor size was significantly increased DDB1F/F,Alb-Cre+/-,IL 6-/- mouse. Further analysis suggested IL6 suppresses HCC by NK cells mediated tumor immunosurveillance. Deletion of TNFR1 decreased HCC incidence in DD B1F/F,Alb-Cre+/- mouse. The levels of apoptosis, compensatory proliferation and p hospho-ERK were also reduced in DDB1F/F,Alb-Cre+/-,TNFR1-/- mouse. Intriguingl y, TNFα knockout accelerated HCC development, which suggested the oncogenic role of TNFR1 mediated signaling pathway is independent of TNFα.