IL6-mediated inflammatory loop reprograms normal to epithelial-mesenchymal transition + metastatic cancer stem cells in preneoplastic liver of transforming growth factor beta-deficient β2-spectrin +/- mice.

Hepatocellular carcinoma (HCC) is the second-leading cause of cancer-related deaths worldwide with a poor survival rate. As many as 40% of HCCs are clonal, with alteration of key tumor-suppressor pathways in stem cells as the primary cause of HCC initiation. However, mechanisms that generate metastatic stem cells in preneoplastic liver tissue are not well understood. We hypothesized that chronic inflammation is a major driver of the transformation of genetically defective liver stem cells (LSCs) into highly metastatic liver cancer cells in premalignant liver tissue. We developed models of chronic inflammation in wild-type (WT) and β2-spectrin (β2SP)+/- (SPTBN1) mice. CD133+ LSCs derived from preneoplastic livers of β2SP+/- mice treated with interleukin-6 (pIL6; IL6 β2SP+/- LSCs) were highly tumorigenic and metastatic, whereas those derived from WT mice treated with pIL6 (IL6 WT LSCs) had significantly less proliferation and no tumorigenic properties. IL6 β2SP+/- LSCs not only exhibited nuclear localization of Twist and Slug, markers of epithelial-mesenchymal transition (EMT), but also constitutive activation of nuclear factor kappa B (NFκB; RELA). Knockdown of NFκB decreased the EMT phenotypes and metastatic capacity of these cells. NFκB in IL6 β2SP+/- LSCs was activated by transforming growth factor β (TGFβ)-activated kinase 1 (TAK1; MAP3K7), which is associated with poor survival in HCC and interleukin-6 (IL6) expression. The amount of constitutively activated NFκB increased dramatically from normal to cirrhotic to HCC tissues from human patients.

CONCLUSION: IL6-mediated inflammation programs constitutive activation of the TAK1-NFκB signaling cascade in CD133+ LSCs, and this program interacts with deficient TGFβ signaling, thereby accelerating the transformation of normal LSCs to metastatic cancer stem cells (mCSCs). Indeed, this study delineates the development of EMT-positive mCSCs in HCC-free liver tissue upon chronic inflammation. (Hepatology 2017;65:1222-1236).