Reversibility of liver cirrhosis

Liver cirrhosis is a leading causes of death worldwide and although treatment options are available for some etiologies (e.g. antiviral therapies) cirrhosis is not reversed and most patients face end- stage liver failure or hepatocellular carcinoma. Liver transplantation is currently the only cure for these patients, but donor organs are limited and mortality on liver transplant waiting lists remains high. Antifibrotic strategies have shown promise in animal models but have not yet demonstrated significant efficacy in patients. A critical fibrogenic pathway upregulated during progression of liver disease is the renin-angiotensin system (RAS). The promising therapeutic potential of targeting the RAS has been demonstrated in several fibrotic diseases and desmoplastic cancers. However, despite positive results in preclinical models, targeting the RAS with angiotensin receptor blockers (ARBs) was ineffective and showed systemic toxicity in cirrhotic patients. This inconsistency might be caused by the difference of disease severity: while human cirrhosis is diagnosed when collagen fibers are mature and septal regions are thick and acellular, most experimental models mimic early stages of fibrosis. We propose to use animal models recapitulating advanced human liver disease. Moreover, dosing of ARBs at levels that are sufficient to inhibit liver fibrosis is not feasible in cirrhotic patients who present with profound hemodynamic alterations because of dose-limiting systemic side effects such as arterial hypotension and renal dysfunction. We propose to overcome this limitation by using a novel nanotechnology platform to deliver high doses of antifibrotic nanoARBs selectively to hepatic stellate cells at sites of active fibrogenesis. We will evaluate these agents using advanced intravital imaging technologies such as optical frequency domain imaging and multiphoton microscopy. In addition, even if potent and selective agents show anti-fibrotic activity, their efficacy in reversing cirrhosis will be largely dependent on their delivery and distribution. Thus, in a complementary approach, we will evaluate the effects of normalizing the remodeled hepatic vasculature in cirrhosis with anti-angiogenic therapy. To this end, we will first test a drug previously approved for liver cancer, sorafenib, which has anti-VEGF and PDGF receptor activity, in established models of cirrhosis. Finally, because sorafenib has significant off-target effects, we propose to develop a strategy to specifically target the abnormal angiocrine signaling responsible for remodeling of the sinusoidal vasculature in cirrhosis. Based on exciting preliminary data, we will dissect the paracrine interactions between liver sinusoidal endothelial cells and hepatic stellate cells with an initial focus on the role of angiopoietins. Our ultimate goal is to identify a more specific and effective anti-angiogenic strategy than sorafenib to reversing cirrhosis in combination with targeted nano-ARBs in clinically relevant models of cirrhosis. These novel approaches of normalizing the pathologic sinusoidal vasculature along with with targeted antifibrotic nanotherapy may yield translatable therapeutic strategies for patients with cirrhosis.

Chronic liver diseases ultimately lead to liver cirrhosis and liver cancer (hepatocellular carcinoma, HCC). Liver cirrhosis is characterized by extensive fibrosis of the organ and impaired hepatic function. Liver cancer almost exclusively develops in cirrhotic livers and represents a highly-vascularized tumor and the anti-angiogentic drug sorafenib is currently the only approved drug for medical treatment of patients with HCC. It is not fully understood to what extent fibrosis itself contributes to the development of HCC and which molecular mechanisms contribute to fibrosis of the liver and of HCC tumors and if fibrosis represents a resistance mechanism to sorafenib treatment.In order to study the role of fibrosis in HCC, we established a clinically relevant liver cancer model in mice that offered several advantages as compared to other traditional models: First, it is an orthotopic model, meaning that the HCC tumor was implanted in the liver and not like in various other models under the skin (subcutaneous models). Second, it is a syngeneic model using HCC tumor cells derived from the same mouse strain in which the tumor is then implanted. In most other models, human tumor cell lines or cell lines from other mouse strains are used and implanted in mice that are immunodeficient in order to allow growths of tumors without immune reaction against the tumor cells. Third, we implanted the tumor cells in mice with diseased (i.e. fibrotic) livers. This is important since the growth of liver tumors and the response to treatments is different depending on the severity of the underlying liver disease. The fibrotic microenvironment in the liver recapitulates more closely the clinical setting since most patients with HCC tumors have underlying liver cirrhosis.Using this novel mouse model we were able to show that the molecule stromal-derived growth factor 1 alpha (SDF1a) and its chemokine receptor CXCR4 promotes fibrosis in the liver and also fibrosis within the HCC tumors. The SDF1a/CXCR4 pathway was even more upregulated after treatment with sorafenib and represented a resistance mechanism to sorafenib treatment. With additional blockade of the SDF1a/CXCR4 pathway during sorafenib treatment HCC tumor fibrosis was decreased and the efficacy of sorafenib was increased in terms of delayed HCC growth in the orthotopic mouse model of HCC.In addition, the upregulation of SDF1a/CXR4 pathway during sorafenib treatment lead to infiltration of immunosuppressive cells and increased expression of the immune checkpoint inhibitor programmed death ligand-1 (PD-L1). Interestingly, the combination of SDF1a/CXCR4 pathway alone prevented the immunosuppressive environment in HCC tumors after sorafenib treatment, but only the additional blockade of the immune checkpoint receptor (PD-1) boosted an antitumor response by promoting cytotoxic CD8+ T-lymphocyte infiltration in HCC tumors.