Liver Cancer Gene Discovery Using Gene Targeting, Sleeping Beauty, and CRISPR/Cas9

Organoid-guided precision hepatology for metabolic liver disease

Metabolic dysfunction-associated steatotic liver disease affects millions of people worldwide. Progress towards a definitive cure has been incremental and treatment is currently limited to lifestyle modification. Hepatocyte-specific lipid accumulation is the main trigger of lipotoxic events, driving inflammation and fibrosis. The underlying pathology is extraordinarily heterogenous, and the manifestations of steatohepatitis are markedly influenced by metabolic communications across non-hepatic organs. Synthetic human tissue models have emerged as powerful platforms to better capture the mechanistic diversity in disease progression, while preserving person-specific genetic traits. In this review, we will outline current research efforts focused on integrating multiple synthetic tissue models of key metabolic organs, with an emphasis on organoid-based systems. By combining functional genomics and population-scale en masse profiling methodologies, human tissues derived from patients can provide insights into personalised genetic, transcriptional, biochemical, and metabolic states. These collective efforts will advance our understanding of steatohepatitis and guide the development of rational solutions for mechanism-directed diagnostic and therapeutic investigation.

Emerging and potential use of CRISPR in human liver disease

CRISPR is a gene editing tool adapted from naturally occurring defense systems from bacteria. It is a technology that is revolutionizing the interrogation of gene functions in driving liver disease, especially through genetic screens and by facilitating animal knockout and knockin models. It is being used in models of liver disease to identify which genes are critical for liver pathology, especially in genetic liver disease, hepatitis, and in cancer initiation and progression. It holds tremendous promise in treating human diseases directly by editing DNA. It could disable gene function in the case of expression of a maladaptive protein, such as blocking transthyretin as a therapy for amyloidosis, or to correct gene defects, such as restoring the normal functions of liver enzymes fumarylacetoacetate hydrolase or alpha-1 antitrypsin. It is also being studied for treatment of hepatitis B infection. CRISPR is an exciting, evolving technology that is facilitating gene characterization and discovery in liver disease and holds the potential to treat liver diseases safely and permanently.

A Therapeutically Targetable TAZ-TEAD2 Pathway Drives the Growth of Hepatocellular Carcinoma via ANLN and KIF23

BACKGROUND & AIMS

Despite recent progress, long-term survival remains low for hepatocellular carcinoma (HCC). The most effective HCC therapies target the tumor immune microenvironment (TIME), and there are almost no therapies that directly target tumor cells. Here, we investigated the regulation and function of tumor cell-expressed Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in HCC.

METHODS

HCC was induced in mice by Sleeping Beauty-mediated expression of MET, CTNNB1-S45Y, or TAZ-S89A, or by diethylnitrosamine plus CCl4. Hepatocellular TAZ and YAP were deleted in floxed mice via adeno-associated virus serotype 8-mediated expression of Cre. TAZ target genes were identified from RNA sequencing, confirmed by chromatin immunoprecipitation, and evaluated in a clustered regularly interspaced short palindromic repeats interference (CRISPRi) screen. TEA domain transcription factors (TEADs), anillin (ANLN), Kif23, and programmed cell death protein ligand 1 were knocked down by guide RNAs in dead clustered regularly interspaced short palindromic repeats-associated protein 9 (dCas9) knock-in mice.

RESULTS

YAP and TAZ were up-regulated in murine and human HCC, but only deletion of TAZ consistently decreased HCC growth and mortality. Conversely, overexpression of activated TAZ was sufficient to trigger HCC. TAZ expression in HCC was regulated by cholesterol synthesis, as demonstrated by pharmacologic or genetic inhibition of 3-hydroxy-3-methylglutaryl- coenzyme A reductase (HMGCR), farnesyl pyrophosphate synthase, farnesyl-diphosphate farnesyltransferase 1 (FDFT1), or sterol regulatory element-binding protein 2 (SREBP2). TAZ- and MET/CTNNB1-S45Y-driven HCC required the expression of TEAD2 and, to a lesser extent, TEAD4. Accordingly, TEAD2 displayed the most profound effect on survival in patients with HCC. TAZ and TEAD2 promoted HCC via increased tumor cell proliferation, mediated by TAZ target genes ANLN and kinesin family member 23 (KIF23). Therapeutic targeting of HCC, using pan-TEAD inhibitors or the combination of a statin with sorafenib or anti-programmed cell death protein 1, decreased tumor growth.

CONCLUSIONS

Our results suggest the cholesterol-TAZ-TEAD2-ANLN/KIF23 pathway as a mediator of HCC proliferation and tumor cell-intrinsic therapeutic target that could be synergistically combined with TIME-targeted therapies.

Lipid Nanoparticle Delivery of Small Proteins for Potent In Vivo RAS Inhibition

Mutated RAS proteins are potent oncogenic drivers and have long been considered "undruggable". While RAS-targeting therapies have recently shown promise, there remains a clinical need for RAS inhibitors with more diverse targets. Small proteins represent a potential new therapeutic option, including K27, a designed ankyrin repeat protein (DARPin) engineered to inhibit RAS. However, K27 functions intracellularly and is incapable of entering the cytosol on its own, currently limiting its utility. To overcome this barrier, we have engineered a lipid nanoparticle (LNP) platform for potent delivery of functional K27-D30─a charge-modified version of the protein─intracellularly in vitro and in vivo. This system efficiently encapsulates charge-modified proteins, facilitates delivery in up to 90% of cells in vitro, and maintains potency after at least 45 days of storage. In vivo, these LNPs deliver K27-D30 to the cytosol of cancerous cells in the liver, inhibiting RAS-driven growth and ultimately reducing tumor load in an HTVI-induced mouse model of hepatocellular carcinoma. This work shows that K27 holds promise as a new cancer therapeutic when delivered using this LNP platform. Furthermore, this technology has the potential to broaden the use of LNPs to include new cargo types─beyond RNA─for diverse therapeutic applications.

MYC and MET cooperatively drive hepatocellular carcinoma with distinct molecular traits and vulnerabilities

Enhanced activation of the transcription factor MYC and of the receptor tyrosine kinase MET are among the events frequently occurring in hepatocellular carcinoma (HCC). Both genes individually act as drivers of liver cancer initiation and progression. However, their concomitant alteration in HCC has not been explored, nor functionally documented. Here, we analysed databases of five independent human HCC cohorts and found a subset of patients with high levels of MYC and MET (MYC^high/MET^high) characterised by poor prognosis. This clinical observation drove us to explore the functionality of MYC and MET co-occurrence in vivo, combining hydrodynamic tail vein injection for MYC expression in the R26^stopMet genetic setting, in which wild-type MET levels are enhanced following the genetic deletion of a stop cassette. Results showed that increased MYC and MET expression in hepatocytes is sufficient to induce liver tumorigenesis even in the absence of pre-existing injuries associated with a chronic disease state. Intriguingly, ectopic MYC in MET tumours increases expression of the Mki67 proliferation marker, and switches them into loss of Afp, Spp1, Gpc3, Epcam accompanied by an increase in Hgma1, Vim, and Hep-Par1 levels. We additionally found a switch in the expression of specific immune checkpoints, with an increase in the Ctla-4 and Lag3 lymphocyte co-inhibitory responses, and in the Icosl co-stimulatory responses of tumour cells. We provide in vitro evidence on the vulnerability of some human HCC cell lines to combined MYC and MET targeting, which are otherwise resistant to single inhibition. Mechanistically, combined blockage of MYC and MET converts a partial cytostatic effect, triggered by individual blockage of MYC or MET, into a cytotoxic effect. Together, these findings highlight a subgroup of HCC characterised by MYC^high/MET^high, and document functional cooperativity between MYC and MET in liver tumorigenesis. Thus, the MYC-R26^Met model is a relevant setting for HCC biology, patient classification and treatment.

rtcisE2F promotes the self-renewal and metastasis of liver tumor-initiating cells via N6-methyladenosine-dependent E2F3/E2F6 mRNA stability

Liver cancer is highly heterogeneous, and the tumor tissue harbors a variety of cell types. Liver tumor initiating cells (TICs) well contribute to tumor heterogeneity and account for tumor initiation and metastasis, but the molecular mechanisms of liver TIC self-renewal are elusive. Here, we identified a functional read-through rt-circRNA, termed rtcisE2F, that is highly expressed in liver cancer and liver TICs. rtcisE2F plays essential roles in the self-renewal and activities of liver TICs. rtcisE2F targets E2F6 and E2F3 mRNAs, attenuates mRNA turnover, and increases E2F6/E2F3 expression. Mechanistically, rtcisE2F functions as a scaffold of N-methyladenosine (m⁶A) reader IGF2BP2 and E2F6/E2F3 mRNA. rtcisE2F promotes the association of E2F6/E2F3 mRNAs with IGF2BP2, and inhibits their association with another m⁶A reader, YTHDF2. IGF2BP2 inhibits E2F6/E2F3 mRNA decay, whereas YTHDF2 promotes E2F6/E2F3 mRNA decay. By switching m⁶A readers, rtcisE2F enhances E2F6/E2F3 mRNA stability. E2F6 and E2F3 are both required for liver TIC self-renewal and Wnt/β-catenin activation, and inhibition of these pathways is a potential strategy for preventing liver tumorigenesis and metastasis. In conclusion, the rtcisE2F-IGF2BP2/YTHDF2-E2F6/E2F3-Wnt/β-catenin axis drives liver TIC self-renewal and initiates liver tumorigenesis and metastasis, and may provide a strategy to eliminate liver TICs.

Nanoscale delivery of phytochemicals targeting CRISPR/Cas9 for cancer therapy

BACKGROUND

With growing global prevalence, cancer is a major cause of disease-related deaths. The understanding of the fundamental tumor pathology has contributed to the development of agents targeting oncogenic signaling pathways. Although these agents have increased survival for defined cancers, the therapeutic choices are still limited due to the development of drug resistance. CRISPR/Cas9 is a powerful new technology in cancer therapy by facilitating the identification of novel treatment targets and development of cell-based treatment strategies.

PURPOSE

We focused on applications of the CRISPR/Cas9 system in cancer therapy and discuss nanoscale delivery of cytotoxic phytochemical targeting the CRISPR/Cas9 system.

RESULTS

Genome engineering has been significantly accelerated by the advancement of the CRISPR/Cas9 technique. Phytochemicals play a key role in treating cancer by targeting various mechanisms and pathways.

CONCLUSIONS

The use of CRISPR/Cas9 for nanoscale delivery of phytochemicals opens new avenues in cancer therapy. One of the main obstacles in the clinical application of CRISPR/Cas9 is safe and efficient delivery. As viral delivery methods have certain drawbacks, there is an urgent need to develop non-viral delivery systems for therapeutic applications.

Exploring liver cancer biology through functional genetic screens

As the fourth leading cause of cancer-related death in the world, liver cancer poses a major threat to human health. Although a growing number of therapies have been approved for the treatment of hepatocellular carcinoma in the past few years, most of them only provide a limited survival benefit. Therefore, an urgent need exists to identify novel targetable vulnerabilities and powerful drug combinations for the treatment of liver cancer. The advent of functional genetic screening has contributed to the advancement of liver cancer biology, uncovering many novel genes involved in tumorigenesis and cancer progression in a high-throughput manner. In addition, this unbiased screening platform also provides an efficient tool for the exploration of the mechanisms involved in therapy resistance as well as identifying potential targets for therapy. In this Review, we describe how functional screens can help to deepen our understanding of liver cancer and guide the development of new therapeutic strategies.

circular RNA cia-MAF drives self-renewal and metastasis of liver tumor-initiating cells via transcription factor MAFF

Liver tumor-initiating cells (TICs) are involved in liver tumorigenesis, metastasis, drug resistance and relapse, but the regulatory mechanisms of liver TICs are largely unknown. Here, we have identified a functional circular RNA, termed circRNA activating MAFF (cia-MAF), that is robustly expressed in liver cancer and liver TICs. cia-MAF knockout primary cells and cia-maf knockout liver tumors harbor decreased ratios of TICs, and display impaired liver tumorigenesis, self-renewal and metastatic capacities. In contrast, cia-MAF overexpression drives liver TIC propagation, self-renewal and metastasis. Mechanistically, cia-MAF binds to the MAFF promoter, recruits the TIP60 complex to the MAFF promoter, and finally promotes MAFF expression. Loss of cia-MAF function attenuates the combination between the TIP60 complex and the MAFF promoter. MAFF is highly expressed in liver tumors and liver TICs, and its antisense oligo (ASO) has therapeutic potential in treating liver cancer without MAFA/MAFG gene copy number alterations (CNAs). This study reveal an additional layer for liver TIC regulation as well as circRNA function, and also provide an additional target for eliminating liver TICs, especially for liver tumor without MAFA/MAFG gene CNAs.

Insight Into the Prospects for RNAi Therapy of Cancer

RNA interference (RNAi), also known as gene silencing, is a biological process that prevents gene expression in certain diseases such as cancer. It can be used to improve the accuracy, efficiency, and stability of treatments, particularly genetic therapies. However, challenges such as delivery of oligonucleotide drug to less accessible parts of the body and the high incidence of toxic side effects are encountered. It is therefore imperative to improve their delivery to target sites and reduce their harmful effects on noncancerous cells to harness their full potential. In this study, the role of RNAi in the treatment of COVID-19, the novel coronavirus disease plaguing many countries, has been discussed. This review aims to ascertain the mechanism and application of RNAi and explore the current challenges of RNAi therapy by identifying some of the cancer delivery systems and providing drug information for their improvement. It is worth mentioning that delivery systems such as lipid-based delivery systems and exosomes have revolutionized RNAi therapy by reducing their immunogenicity and improving their cellular affinity. A deeper understanding of the mechanism and challenges associated with RNAi in cancer therapy can provide new insights into RNAi drug development.

Multiple Roles for Hepatitis B and C Viruses and the Host in the Development of Hepatocellular Carcinoma

Chronic hepatitis B and C viral infections are major risk factors for hepatocellular carcinoma (HCC) in the United States and worldwide. Direct and indirect mechanisms of viral infection lead to the development of HCC. Chronic viral infection leads to inflammation and liver damage, culminating in cirrhosis, the penultimate step in the progression toward HCC. Host, viral, and environmental factors likely interact to promote oncogenesis. Clinical considerations include recommendations for screening for HCC in persons at risk, treatment with antivirals, and an emerging role for immunotherapy in HCC. We pose unanswered questions regarding HCC susceptibility and pathogenesis in the setting of chronic hepatitis B and C.

A peptide-functionalised dendronised polymer for selective transfection in human liver cancer cells

A dendronised polymer functionalised with SP94 targeting peptide achieves highly selective transient transfection of liver cancer cells over normal non-transformed hepatocytes.

CRISPR/Cas9: A powerful genome editing technique for the treatment of cancer cells with present challenges and future directions

Cancer is one of the most leading causes of death and a major public health problem, universally. According to accumulated data, annually, approximately 8.5 million people died because of the lethality of cancer. Recently, a novel RNA domain-containing endonuclease-based genome engineering technology, namely the clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein-9 (Cas9) have been proved as a powerful technique in the treatment of cancer cells due to its multifunctional properties including high specificity, accuracy, time reducing and cost-effective strategies with minimum off-target effects. The present review investigates the overview of recent studies on the newly developed genome-editing strategy, CRISPR/Cas9, as an excellent pre-clinical therapeutic option in the reduction and identification of new tumor target genes in the solid tumors. Based on accumulated data, we revealed that CRISPR/Cas9 significantly inhibited the robust tumor cell growth (breast, lung, liver, colorectal, and prostate) by targeting the oncogenes, tumor-suppressive genes, genes associated to therapies by inhibitors, genes associated to chemotherapies drug resistance, and suggested that CRISPR/Cas9 could be a potential therapeutic target in inhibiting the tumor cell growth by suppressing the cell-proliferation, metastasis, invasion and inducing the apoptosis during the treatment of malignancies in the near future. The present review also discussed the current challenges and barriers, and proposed future recommendations for a better understanding.

Technologies for targeting DNA methylation modifications: Basic mechanism and potential application in cancer

DNA methylation abnormalities are regarded as critical event for cancer initiation and development. Tumor-associated genes encompassing aberrant DNA methylation alterations at specific locus are correlated with chromatin remodeling and dysregulation of gene expression in various malignancies. Thus, technologies designed to manipulate DNA methylation at specific loci of genome are necessary for the functional study and therapeutic application in the context of cancer management. Traditionally, the method for DNA methylation modifications demonstrates an unspecific feature, adversely causing global-genome epigenetic alterations and confusing the function of desired gene. Novel approaches for targeted DNA methylation regulation have a great advantage of manipulating gene epigenetic alterations in a more specific and efficient method. In this review, we described different targeting DNA methylation techniques, including both their advantages and limitations. Through a comprehensive understanding of these targeting tools, we hope to open a new perspective for cancer treatment.

Using CRISPR/Cas9 to model human liver disease

CRISPR/Cas9 gene editing has revolutionised biomedical research. The ease of design has allowed many groups to apply this technology for disease modelling in animals. While the mouse remains the most commonly used organism for embryonic editing, CRISPR is now increasingly performed with high efficiency in other species. The liver is also amenable to somatic genome editing, and some delivery methods already allow for efficient editing in the whole liver. In this review, we describe CRISPR-edited animals developed for modelling a broad range of human liver disorders, such as acquired and inherited hepatic metabolic diseases and liver cancers. CRISPR has greatly expanded the repertoire of animal models available for the study of human liver disease, advancing our understanding of their pathophysiology and providing new opportunities to develop novel therapeutic approaches.

The Dynamic Chromatin Architecture of the Regenerating Liver

BACKGROUND & AIMS

The adult liver is the main detoxification organ and routinely is exposed to environmental insults but retains the ability to restore its mass and function upon tissue damage. However, extensive injury can lead to liver failure, and chronic injury causes fibrosis, cirrhosis, and hepatocellular carcinoma. Currently, the transcriptional regulation of organ repair in the adult liver is incompletely understood.

METHODS

We isolated nuclei from quiescent as well as repopulating hepatocytes in a mouse model of hereditary tyrosinemia, which recapitulates the injury and repopulation seen in toxic liver injury in human beings. We then performed the assay for transposase accessible chromatin with high-throughput sequencing specifically in repopulating hepatocytes to identify differentially accessible chromatin regions and nucleosome positioning. In addition, we used motif analysis to predict differential transcription factor occupancy and validated the in silico results with chromatin immunoprecipitation followed by sequencing for hepatocyte nuclear factor 4α (HNF4α) and CCCTC-binding factor (CTCF).

RESULTS

Chromatin accessibility in repopulating hepatocytes was increased in the regulatory regions of genes promoting proliferation and decreased in the regulatory regions of genes involved in metabolism. The epigenetic changes at promoters and liver enhancers correspond with the regulation of gene expression, with enhancers of many liver function genes showing a less accessible state during the regenerative process. Moreover, increased CTCF occupancy at promoters and decreased HNF4α binding at enhancers implicate these factors as key drivers of the transcriptomic changes in replicating hepatocytes that enable liver repopulation.

CONCLUSIONS

Our analysis of hepatocyte-specific epigenomic changes during liver repopulation identified CTCF and HNF4α as key regulators of hepatocyte proliferation and regulation of metabolic programs. Thus, liver repopulation in the setting of toxic injury makes use of both general transcription factors (CTCF) for promoter activation, and reduced binding by a hepatocyte-enriched factor (HNF4α) to temporarily limit enhancer activity. All sequencing data in this study were deposited to the Gene Expression Omnibus database and can be downloaded with accession number GSE109466.