Normalization of tumor microenvironment in HCC

Hepatocellular carcinoma (HCC) represents the third most common cause of cancer-related death since most patients are diagnosed at advanced tumor stages. The multikinase inhibitor sorafenib remains the only therapeutic option in patients with advanced HCC with yet limited efficacy in terms of survival. Thus, the continuous investigation of more effective therapeutic strategies represents an unmet clinical need to improve the outcome of this fatal disease. Profound abnormalities of the tumor vasculature and the extracellular matrix (ECM) have been found to promote tumor progression, metastasis, immunosuppression, as well as resistance to treatment. In various tumor entities the normalization of this hostile tumor microenvironment improved treatment response and survival in preclinical cancer models as well as in clinical studies. Importantly, HCC usually develops in patients with liver cirrhosis. Liver cirrhosis per se is a severe disease and largely determines the prognosis of HCC patients. Yet, it remains to be explored how the abnormalities of both, the cirrhotic microenvironment and the HCC tumors, can be effectively targeted. The extent of hepatic fibrosis also promotes the progression of HCC as shown by recent data of the Steele Lab (host institution). Additional work revealed that combining a nanoparticle formulation of the anti-fibrotic drug losartan (nano-losartan) in combination with low-dose sorafenib reverted the abnormalities of the cirrhotic microenvironment by blocking ECM deposition and normalizing the hepatic sinusoidal vasculature. Notably, preliminary data also showed efficacy of immunotherapy in experimental HCC models. In line with the concept of normalizing tumor microenvironment, we hypothesize that reducing intratumoral fibrosis by nano-losartan in combination with normalization of the HCC tumor vasculature by low-dose sorafenib could facilitate delivery and improve efficacy of immunotherapy. Additionally, the beneficial effects of nano-losartan and low-dose sorafenib on the pathologic microenvironment of the cirrhotic liver could further delay tumor progression and improve efficacy of immunotherapy. The ultimate goal of this research proposal is to assess if anti-fibrotic nanotherapy in combination with vascular normalization can optimize the efficacy of immunotherapy for HCC. We will test these treatments in murine models of advanced cirrhosis and orthotopic HCC tumors. Dynamic changes of both the cirrhotic host liver and the tumor microenvironment will be longitudinally monitored by advanced intravital imaging technologies developed at the Steele lab. We will also use standard lab techniques including immunohistochemistry or western blotting. The project is novel and unique since the concept of normalizing tumor microenvironment has not been tested in HCC so far. Furthermore, it will reveal deeper insights into the role of immunotherapy for HCC and might help to improve the future development of immunotherapeutic strategies with regard to the unique pathological characteristics of HCC.

Both fibrogenesis and angiogenesis play an important role in the pathophysiology of liver cirrhosis and its complications. HCC usually develops in patients with liver cirrhosis and complications of liver cirrhosis are a main cause of death in patients with HCC. Thus, improving the underlying liver disease may ultimately improve the prognosis of HCC.In a retrospective cohort of 156 patients with HCC and well-preserved liver function we found that the use of renin-angiotensin system inhibitors (RASi) treatment was associated with improved survival and remained a significant prognostic factor upon multivariate analysis. In subgroup analysis, patients treated with the multityrosine kinase inhibitor sorafenib plus RASi had a better survival compared to those who received only sorafenib, the standard of care for patients with advanced HCC. The beneficial effect of RASi on survival was confirmed in an independent cohort of 76 patients treated with sorafenib. Hence, RASi may be a potential adjuvant to standard treatment of HCC, and prospective studies are warranted.Based on these findings, we hypothesized that the main mechanism of action was an improvement of underlying liver cirrhosis due to antifibrotic and anti-portal hypertensive effects, even though RASi are also well-known for having direct anti-tumor activity. Beside its anti-proliferative effects, sorafenib has also antiangiogenic properties.In a murine model of chemically-induced liver cirrhosis we investigated the effect of the angiotensin receptor blocker telmisartan in combination with sorafenib on vascular remodeling and fibrogenesis. There was no effect of any treatment on liver vasculature in terms of vessel diameter or tortuosity as assessed by intravital imaging with optical frequency domain imaging (OFDI). We also found no differences regarding liver fibrosis/cirrhosis. Despite these disappointing results, we wanted to test our hypothesis by using an angiotensin II type 1 receptor (AT1R) knockout model, the strongest inhibition of the profibrotic angiotensin II/AT1R axis. Hence, we chemically induced liver fibrosis in AT1R knock-out (KO) and wild-type (WT) mice and added sorafenib after cirrhosis was established. Again, neither AT1R KO nor sorafenib treatment had any beneficial effects on liver fibrosis or liver vasculature.In conclusion, these findings suggest that targeting angiogenesis and fibrogenesis may not be effective in advanced stages of fibrosis/cirrhosis since fibrosis resolution and remodeling become more difficult due to established collagen cross-linking. Thus, the beneficial effects of RASi use on survival of HCC patients may rather result from its direct anti-tumor effects.