PD-1 immune checkpoint inhibitors have produced encouraging results in patients with hepatocellular carcinoma (HCC). However, what determines resistance to anti-PD-1 therapies is unclear. We created a novel genetically engineered mouse model of HCC that enables interrogation of how different genetic alterations affect immune surveillance and response to immunotherapies. Expression of exogenous antigens in MYC;Trp53 −/− HCCs led to T cell-mediated immune surveillance, which was accompanied by decreased tumor formation and increased survival. Some antigen-expressing MYC;Trp53 −/− HCCs escaped the immune system by upregulating the β-catenin (CTNNB1) pathway. Accordingly, expression of exogenous antigens in MYC;CTNNB1 HCCs had no effect, demonstrating that β-catenin promoted immune escape, which involved defective recruitment of dendritic cells and consequently impaired T-cell activity. Expression of chemokine CCL5 in antigenexpressing MYC;CTNNB1 HCCs restored immune surveillance. Finally, β-catenin-driven tumors were resistant to anti-PD-1. In summary, β-catenin activation promotes immune escape and resistance to anti-PD-1 and could represent a novel biomarker for HCC patient exclusion. SIGNIFICANCE: Determinants of response to anti-PD-1 immunotherapies in HCC are poorly understood. Using a novel mouse model of HCC, we show that β-catenin activation promotes immune evasion and resistance to anti-PD-1 therapy and could potentially represent a novel biomarker for HCC patient exclusion.

See Covering the Cover synopsis on page 1997. BACKGROUND AND AIMS: The pattern of genetic alterations in cancer driver genes in patients with hepatocellular carcinoma (HCC) is highly diverse, which partially explains the low efficacy of available therapies. In spite of this, the existing mouse models only recapitulate a small portion of HCC intertumor heterogeneity, limiting the understanding of the disease and the nomination of personalized therapies. Here, we aimed at establishing a novel collection of HCC mouse models that captured human HCC diversity. METHODS: By performing hydrodynamic tail-vein injections, we tested the impact of altering a well-established HCC oncogene (either MYC or bcatenin) in combination with an additional alteration in one of eleven other genes frequently mutated in HCC. Of the 23 unique Gastroenterology 2020;159:2203-2220 BASIC AND TRANSLATIONAL LIVER pairs of genetic alterations that we interrogated, 9 were able to induce HCC. The established HCC mouse models were characterized at histopathological, immune, and transcriptomic level to identify the unique features of each model. Murine HCC cell lines were generated from each tumor model, characterized transcriptionally, and used to identify specific therapies that were validated in vivo. RESULTS: Cooperation between pairs of driver genes produced HCCs with diverse histopathology, immune microenvironments, transcriptomes, and drug responses. Interestingly, MYC expression levels strongly influenced b-catenin activity, indicating that inter-tumor heterogeneity emerges not only from specific combinations of genetic alterations but also from the acquisition of expression-dependent phenotypes. CONCLUSIONS: This novel collection of murine HCC models and corresponding cell lines establishes the role of driver genes in diverse contexts and enables mechanistic and translational studies.

Preclinical models of cancer based on the use of human cancer cell lines and mouse models have enabled discoveries that have been successfully translated into patients. And yet the majority of clinical trials fail, emphasising the urgent need to improve preclinical research to better interrogate the potential efficacy of each therapy and the patient population most likely to benefit. This is particularly important for liver malignancies, which lack highly efficient treatments and account for hundreds of thousands of deaths around the globe. Given the intricate network of genetic and environmental factors that contribute to liver cancer development and progression, the identification of new druggable targets will mainly depend on establishing preclinical models that mirror the complexity of features observed in patients. The development of new 3D cell culture systems, originating from cells/tissues isolated from patients, might create new opportunities for the generation of more specific and personalised therapies. However, these systems are unable to recapitulate the tumour microenvironment and interactions with the immune system, both proven to be critical influences on therapeutic outcomes. Patient-derived xenografts, in particular with humanised mouse models, more faithfully mimic the physiology of human liver cancer but are costly and time-consuming, which can be prohibitive for personalising therapies in the setting of an aggressive malignancy. In this review, we discuss the latest advances in the development of more accurate preclinical models to better understand liver cancer biology and identify paradigm-changing therapies, stressing the importance of a bi-directional communicative flow between clinicians and researchers to establish reliable model systems and determine how best to apply them to expanding our current knowledge.

Background and Objectives:Laparoscopic inguinal hernia repair has become increasingly popular as an alternative to open surgery. The purpose of this study was to evaluate the safety and effectiveness of the laparoscopic total extraperitoneal procedure with the use of staple fixation and polypropylene mesh.Methods:A retrospective chart review examined outcomes of 1240 laparoscopic hernia operations in 783 patients, focusing on intraoperative and early postoperative complications, pain, and time until return to work and normal physical activities.Results:There were no intraoperative complications in this series; 106 patients experienced early postoperative complications across 8 evaluated categories: urinary retention (4.1%), seroma (3.0%), testicular/hemiscrotal swelling (1.9%), testicular atrophy (0%), hydrocele (0.6%), mesh infection (0.1%), and neurological symptoms (transient, 1.0%; persistent, 0.2%). Patients used an average of 5.6 Percocet pills after the procedure, and mean times until return to work and normal activities, including their routine exercise regimen, were 3.0 and 3.8 days, respectively.Conclusion:Complication rates and convalescence times were considered equivalent or superior to those found in other studies assessing both laparoscopic and open techniques. The usage of multiple Endostaples did not result in increased neurologic complications in the early postoperative period when compared with findings in the literature. In the hands of an experienced surgeon, total extraperitoneal repair is a safe, effective alternative to open inguinal hernia repair.

Self-gripping mesh can be safely used during laparoscopic TEP inguinal hernia repairs; our cohort had a rapid recovery, and at the 1-year follow-up visit, there were no recurrences and no patients reported any chronic pain as defined by a CCS™ > 1.

High-energy charged particles are considered particularly hazardous components of the space radiation environment. Such particles include fully ionized energetic nuclei of helium, silicon, and oxygen, among others. Exposure to charged particles causes reactive oxygen species production, which has been shown to result in neuronal dysfunction and myelin degeneration. Here we demonstrate that mice exposed to high-energy charged particles exhibited alterations in dendritic spine density in the hippocampus, with a significant decrease of thin spines in mice exposed to helium, oxygen, and silicon, compared to sham-irradiated controls. Electron microscopy confirmed these findings and revealed a significant decrease in overall synapse density and in nonperforated synapse density, with helium and silicon exhibiting more detrimental effects than oxygen. Degeneration of myelin was also evident in exposed mice with significant changes in the percentage of myelinated axons and g-ratios. Our data demonstrate that exposure to all types of high-energy charged particles have a detrimental effect, with helium and silicon having more synaptotoxic effects than oxygen. These results have important implications for the integrity of the central nervous system and the cognitive health of astronauts after prolonged periods of space exploration.

Cancer testis antigens (CTAs) are an extensive gene family with a unique expression pattern restricted to germ cells, but aberrantly reactivated in cancer tissues. Studies indicate that the expression (or re-expression) of CTAs within the MAGE-A family is common in hepatocellular carcinoma (HCC). However, no systematic characterization has yet been reported. The aim of this study is to perform a comprehensive profile of CTA de-regulation in HCC and experimentally evaluate the role of MAGEA3 as a driver of HCC progression. The transcriptomic analysis of 44 multi-regionally sampled HCCs from 12 patients identified high intra-tumor heterogeneity of CTAs. In addition, a subset of CTAs was significantly overexpressed in histologically poorly differentiated regions. Further analysis of CTAs in larger patient cohorts revealed high CTA expression related to worse overall survival and several other markers of poor prognosis. Functional analysis of MAGEA3 was performed in human HCC cell lines by gene silencing and in a genetic mouse model by overexpression of MAGEA3 in the liver. Knockdown of MAGEA3 decreased cell proliferation, colony formation and increased apoptosis. MAGEA3 overexpression was associated with more aggressive tumors in vivo. In conclusion MAGEA3 enhances tumor progression and should be considered as a novel therapeutic target in HCC.

Liver cancer is the fourth-leading cause of cancer-related mortality worldwide and incidence is on the rise. HCC is the most common form of liver cancer, with a complex etiology and limited treatment options. The standard of care treatment for advanced HCC patients is sorafenib, a tyrosine kinase inhibitor that offers limited survival benefit. In the past years, therapeutic options for the treatment of advanced HCC have increased substantially, including additional multikinase inhibitors as well as immune-checkpoint inhibitors. Nivolumab and pembrolizumab were approved in 2017 and 2018, respectively, as second-line treatment in advanced HCC. These drugs, both targeting the programmed death-1 (PD-1) pathway, demonstrate unprecedented results, with objective response rates of approximately 20%. However, the majority of patients do not respond, necessitating the identification of biomarkers of response and resistance to immunotherapy. With the recent success of immunotherapies in oncology, mouse models that better recapitulate the human disease and anti-tumor immune response are needed. This review lists ongoing clinical trials testing immunotherapy in HCC, briefly discusses the unique immunosuppressive environment of the liver, then delves into the most applicable current murine model systems to study oncoimmunology within the context of HCC, including syngeneic, genetically-engineered, and humanized models.