Mechano-Signaling Aspects of Hepatocellular Carcinoma

USP40 promotes hepatocellular carcinoma progression through a YAP/USP40 positive feedback loop

Yes-associated protein (YAP) is an essential driver of hepatocellular carcinoma (HCC) progression and the ubiquitin-proteasome system controls its abundance. However, the role of ubiquitin-specific protease 40 (USP40) in YAP stability remains unclear. Here, USP40 was first identified as a novel regulator of YAP abundance and its target genes in HCC cells. USP40 interacted with YAP to remove the lysine 48 (K48)-linked polyubiquitination of YAP at K252 and K315 sites, thereby maintaining YAP stability. USP40 facilitated the proliferation, colony formation, migration and spheroid formation of HCC cells in vitro and promoted HCC growth in vivo in a YAP-dependent manner. In turn, YAP transcriptionally activated USP40 expression in HCC cells. RNA sequencing analysis showed that about 37% of USP40-regulated genes overlapped with YAP-regulated genes. Interestingly, stiffness-induced USP40 upregulation was abolished by YAP knockdown, and USP40 knockdown attenuated stiffness-induced YAP accumulation in HCC cells. Clinical data demonstrated that USP40 was positively associated with YAP expression in HCC tissues and its high expression indicated a poor prognosis. In conclusion, the USP40/YAP positive feedback loop contributes to HCC progression, suggesting that USP40 may be a promising drug target for anti-HCC.

RGD density along with substrate stiffness regulate hPSC hepatocyte functionality through YAP signalling

Human pluripotent stem cell-derived hepatocytes (hPSC-Heps) may be suitable for treating liver diseases, but differentiation protocols often fail to yield adult-like cells. We hypothesised that replicating healthy liver niche biochemical and biophysical cues would produce hepatocytes with desired metabolic functionality. Using 2D synthetic hydrogels which independently control mechanical properties and biochemical cues, we found that culturing hPSC-Heps on surfaces matching the stiffness of fibrotic liver tissue upregulated expression of genes for RGD-binding integrins, and increased expression of YAP/TAZ and their transcriptional targets. Alternatively, culture on soft, healthy liver-like substrates drove increases in cytochrome p450 activity and ureagenesis. Knockdown of ITGB1 or reducing RGD-motif-containing peptide concentration in stiff hydrogels reduced YAP activity and improved metabolic functionality; however, on soft substrates, reducing RGD concentration had the opposite effect. Furthermore, targeting YAP activity with verteporfin or forskolin increased cytochrome p450 activity, with forskolin dramatically enhancing urea synthesis. hPSC-Heps could also be successfully encapsulated within RGD peptide-containing hydrogels without negatively impacting hepatic functionality, and compared to 2D cultures, 3D cultured hPSC-Heps secreted significantly less fetal liver-associated alpha-fetoprotein, suggesting furthered differentiation. Our platform overcomes technical hurdles in replicating the liver niche, and allowed us to identify a role for YAP/TAZ-mediated mechanosensing in hPSC-Hep differentiation.

Influence of extracellular matrix composition on tumour cell behaviour in a biomimetic in vitro model for hepatocellular carcinoma

The tumor micro-environment (TME) of hepatocellular carcinoma (HCC) consists out of cirrhotic liver tissue and is characterized by an extensive deposition of extracellular matrix proteins (ECM). The evolution from a reversible fibrotic state to end-stage of liver disease, namely cirrhosis, is characterized by an increased deposition of ECM, as well as changes in the exact ECM composition, which both contribute to an increased liver stiffness and can alter tumor phenotype. The goal of this study was to assess how changes in matrix composition and stiffness influence tumor behavior. HCC-cell lines were grown in a biomimetic hydrogel model resembling the stiffness and composition of a fibrotic or cirrhotic liver. When HCC-cells were grown in a matrix resembling a cirrhotic liver, they increased proliferation and protein content, compared to those grown in a fibrotic environment. Tumour nodules spontaneously formed outside the gels, which appeared earlier in cirrhotic conditions and were significantly larger compared to those found outside fibrotic gels. These tumor nodules had an increased expression of markers related to epithelial-to-mesenchymal transition (EMT), when comparing cirrhotic to fibrotic gels. HCC-cells grown in cirrhotic gels were also more resistant to doxorubicin compared with those grown in fibrotic gels or in 2D. Therefore, altering ECM composition affects tumor behavior, for instance by increasing pro-metastatic potential, inducing EMT and reducing response to chemotherapy.

Multiscale biomechanics and mechanotransduction from liver fibrosis to cancer

A growing body of multiscale biomechanical studies has been proposed to highlight the mechanical cues in the development of hepatic fibrosis and cancer. At the cellular level, changes in mechanical microenvironment induce phenotypic and functional alterations of hepatic cells, initiating a positive feedback loop that promotes liver fibrogenesis and hepatocarcinogenesis. Tumor mechanical microenvironment of hepatocellular carcinoma facilitates tumor cell growth and metastasis, and hinders the drug delivery and immunotherapy. At the molecular level, mechanical forces are sensed and transmitted into hepatic cells via allosteric activation of mechanoreceptors on the cell membrane, leading to the activation of various mechanotransduction pathways including integrin and YAP signaling and then regulating cell function. Thus, the application of mechanomedicine concept in the treatment of liver diseases is promising for rational design and cell-specific delivery of therapeutic drugs. This review mainly discusses the correlation between biomechanical cues and liver diseases from the viewpoint of mechanobiology.

Advancing Key Gaps in the Knowledge of Plasmodium vivax Cryptic Infections Using Humanized Mouse Models and Organs-on-Chips

Plasmodium vivax is the most widely distributed human malaria parasite representing 36.3% of disease burden in the South-East Asia region and the most predominant species in the region of the Americas. Recent estimates indicate that 3.3 billion of people are under risk of infection with circa 7 million clinical cases reported each year. This burden is certainly underestimated as the vast majority of chronic infections are asymptomatic. For centuries, it has been widely accepted that the only source of cryptic parasites is the liver dormant stages known as hypnozoites. However, recent evidence indicates that niches outside the liver, in particular in the spleen and the bone marrow, can represent a major source of cryptic chronic erythrocytic infections. The origin of such chronic infections is highly controversial as many key knowledge gaps remain unanswered. Yet, as parasites in these niches seem to be sheltered from immune response and antimalarial drugs, research on this area should be reinforced if elimination of malaria is to be achieved. Due to ethical and technical considerations, working with the liver, bone marrow and spleen from natural infections is very difficult. Recent advances in the development of humanized mouse models and organs-on-a-chip models, offer novel technological frontiers to study human diseases, vaccine validation and drug discovery. Here, we review current data of these frontier technologies in malaria, highlighting major challenges ahead to study P. vivax cryptic niches, which perpetuate transmission and burden.

Polyisocyanide hydrogels with tunable nonlinear elasticity mediate liver carcinoma cell functional response

Hepatocellular carcinoma development is closely related to the changes in tissue mechanics induced by excess collagen deposition and crosslinking, which leads to liver fibrosis and malignant progression. The role of matrix stiffness has been widely assessed using various linearly elastic materials. However, the liver, like many soft tissues, also exhibits nonlinear elasticity by strain-stiffening, allowing cells to mechanically interact with their micromilieus which has attracted much attention in cellular processes recently. Here, we use a biomimetic hydrogel grafting of GRGDS peptide with tunable nonlinear mechanical properties, polyisocyanides (PIC), to investigate the influence of strain-stiffening on HepG2 liver cancer cell behavior by tuning PIC polymer length. Compared to short PIC polymer with lower critical stress, PIC hydrogels composed of long polymer with higher critical stress promote the motility and invasiveness of HepG2 cells, and induce more actin stress fibers and higher expression level of mechanotransducer YAP and its nuclear translocation. Strikingly, the expression of calcium-activated potassium channel KCa3.1, an important biomarker in hepatocellular carcinoma, is also affected by the mechanical property of PIC hydrogels. It was also shown that downregulating the KCa3.1 channel can be achieved by inhibiting the formation of actin fibers. Our findings imply that the strain-stiffening property of PIC hydrogels affects the expression of KCa3.1 potassium channel via mediating cytoskeletal stress fiber formation, and ultimately influences the liver carcinoma cell functional response. STATEMENT OF SIGNIFICANCE: The effect of nonlinear elasticity by strain-stiffening, is assessed in HepG2 liver cancer cell behavior by using a biomimetic hydrogel with tunable mechanical properties, polyisocyanides (PIC). PIC gels with higher critical stress promote the motility and invasiveness of HepG2 cells and induce upregulated expression levels of KCa3.1 potassium channel and YAP, but which can be suppressed by inhibiting the formation of actin fibers. Our findings imply that the strain-stiffening property of PIC gels influences the expression of KCa3.1 potassium channel via mediating cytoskeletal stress fiber formation and, ultimately affects the liver carcinoma cell functional response.

Parafibromin Is Highly Expressed in Hepatocellular Carcinoma and Its Expression Correlates with Poor Prognosis

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. Much progress has been made regarding the understanding of hepatocarcinogenesis, yet the long-term survival rate of HCC patients remains poor. Recent efforts have shown parafibromin has a pathologic role in many human cancers, but little is known about the effects of parafibromin in HCC. This study aimed to investigate the pattern of parafibromin expression and its clinicopathologic significance in human HCC. Immunohistochemical analysis of HCC and matched non-tumor liver tissues from 50 HCC patients showed that the nuclear expression of parafibromin was higher in HCC tissues (50/50 cases) than in non-tumor liver tissues (17/50 cases). Moreover, elevated parafibromin expression was found to be significantly correlated with the presence of microvascular invasion (p = 0.017), hepatitis virus infection-induced occurrence (p = 0.005), and poorer tumor differentiation (Edmondson-Steiner grade; p = 0.000). Kaplan-Meier analysis showed that HCC patients with elevated parafibromin expression had poorer recurrence-free (p = 0.014, log-rank test = 6.079) and overall survival (p = 0.036, log-rank test = 4.414). These findings indicate parafibromin may be related to the pathogenesis of HCC and a potential prognostic marker for HCC patients after hepatectomy.