Mitochondrial topoisomerase IB (TOP1MT) is a nuclear-encoded topoisomerase, exclusively localized to mitochondria, which resolves topological stress generated during mtDNA replication and ...transcription. Here, we report that TOP1MT is overexpressed in cancer tissues and demonstrate that TOP1MT deficiency attenuates tumor growth in human and mouse models of colon and liver cancer. Due to their mitochondrial dysfunction, TOP1MT-KO cells become addicted to glycolysis, which limits synthetic building blocks and energy supply required for the proliferation of cancer cells in a nutrient-deprived tumor microenvironment. Mechanistically, we show that TOP1MT associates with mitoribosomal subunits, ensuring optimal mitochondrial translation and assembly of oxidative phosphorylation complexes that are critical for sustaining tumor growth. The TOP1MT genomic signature profile, based on Top1mt-KO liver cancers, is correlated with enhanced survival of hepatocellular carcinoma patients. Our results highlight the importance of TOP1MT for tumor development, providing a potential rationale to develop TOP1MT-targeted drugs as anticancer therapies.
MicroRNA-122 (miR-122), which accounts for 70% of the liver's total miRNAs, plays a pivotal role in the liver. However, its intrinsic physiological roles remain largely undetermined. We demonstrated ...that mice lacking the gene encoding miR-122a (Mir122a) are viable but develop temporally controlled steatohepatitis, fibrosis, and hepatocellular carcinoma (HCC). These mice exhibited a striking disparity in HCC incidence based on sex, with a male-to-female ratio of 3.9:1, which recapitulates the disease incidence in humans. Impaired expression of microsomal triglyceride transfer protein (MTTP) contributed to steatosis, which was reversed by in vivo restoration of Mttp expression. We found that hepatic fibrosis onset can be partially attributed to the action of a miR-122a target, the Klf6 transcript. In addition, Mir122a(-/-) livers exhibited disruptions in a range of pathways, many of which closely resemble the disruptions found in human HCC. Importantly, the reexpression of miR-122a reduced disease manifestation and tumor incidence in Mir122a(-/-) mice. This study demonstrates that mice with a targeted deletion of the Mir122a gene possess several key phenotypes of human liver diseases, which provides a rationale for the development of a unique therapy for the treatment of chronic liver disease and HCC.
miR-122, an abundant liver-specific microRNA (miRNA), regulates cholesterol metabolism and promotes hepatitis C virus (HCV) replication. Reduced miR-122 expression in hepatocellular carcinoma (HCC) ...correlates with metastasis and poor prognosis. Nevertheless, the consequences of sustained loss of function of miR-122 in vivo have not been determined. Here, we demonstrate that deletion of mouse Mir122 resulted in hepatosteatosis, hepatitis, and the development of tumors resembling HCC. These pathologic manifestations were associated with hyperactivity of oncogenic pathways and hepatic infiltration of inflammatory cells that produce pro-tumorigenic cytokines, including IL-6 and TNF. Moreover, delivery of miR-122 to a MYC-driven mouse model of HCC strongly inhibited tumorigenesis, further supporting the tumor suppressor activity of this miRNA. These findings reveal critical functions for miR-122 in the maintenance of liver homeostasis and have important therapeutic implications, including the potential utility of miR-122 delivery for selected patients with HCC and the need for careful monitoring of patients receiving miR-122 inhibition therapy for HCV.
Background & Aims The mechanisms of hypoxia-induced tumor growth remain unclear. Hypoxia induces intracellular translocation and release of a variety of damage associated molecular patterns (DAMPs) ...such as nuclear HMGB1 and mitochondrial DNA (mtDNA). In inflammation, Toll-like receptor (TLR)-9 activation by DNA-containing immune complexes has been shown to be mediated by HMGB1. We thus hypothesize that HMGB1 binds mtDNA in the cytoplasm of hypoxic tumor cells and promotes tumor growth through activating TLR9 signaling pathways. Methods C57BL6 mice were injected with Hepa1-6 cancer cells. TLR9 and HMGB1 were inhibited using shRNA or direct antagonists. HuH7 and Hepa1-6 cancer cells were investigated in vitro to determine how the interaction of HMGB1 and mtDNA activates TLR9 signaling pathways. Results During hypoxia, HMGB1 translocates from the nucleus to the cytosol and binds to mtDNA released from damaged mitochondria. This complex subsequently activates TLR9 signaling pathways to promote tumor cell proliferation. Loss of HMGB1 or mtDNA leads to a defect in TLR9 signaling pathways in response to hypoxia, resulting in decreased tumor cell proliferation. Also, the addition of HMGB1 and mtDNA leads to the activation of TLR9 and subsequent tumor cell proliferation. Moreover, TLR9 is overexpressed in both hypoxic tumor cells in vitro and in human hepatocellular cancer (HCC) specimens; and, injection in mice to knockdown either HMGB1 or TLR9 from HCC cells suppressed tumor growth in vivo. Conclusions Our data reveals a novel mechanism by which the interactions of HMGB1 and mtDNA activate TLR9 signaling during hypoxia to induce tumor growth.
MYC oncoproteins are involved in the genesis and maintenance of the majority of human tumors but are considered undruggable. By using a direct in vivo shRNA screen, we show that liver cancer cells ...that have mutations in the gene encoding the tumor suppressor protein p53 (Trp53 in mice and TP53 in humans) and that are driven by the oncoprotein NRAS become addicted to MYC stabilization via a mechanism mediated by aurora kinase A (AURKA). This MYC stabilization enables the tumor cells to overcome a latent G2/M cell cycle arrest that is mediated by AURKA and the tumor suppressor protein p19(ARF). MYC directly binds to AURKA, and inhibition of this protein-protein interaction by conformation-changing AURKA inhibitors results in subsequent MYC degradation and cell death. These conformation-changing AURKA inhibitors, with one of them currently being tested in early clinical trials, suppressed tumor growth and prolonged survival in mice bearing Trp53-deficient, NRAS-driven MYC-expressing hepatocellular carcinomas (HCCs). TP53-mutated human HCCs revealed increased AURKA expression and a positive correlation between AURKA and MYC expression. In xenograft models, mice bearing TP53-mutated or TP53-deleted human HCCs were hypersensitive to treatment with conformation-changing AURKA inhibitors, thus suggesting a therapeutic strategy for this subgroup of human HCCs.
Sorafenib is the recommended treatment for patients with advanced hepatocellular carcinoma. We aimed to compare the efficacy and safety of sorafenib to that of selective internal radiotherapy (SIRT) ...with yttrium-90 (90Y) resin microspheres in patients with hepatocellular carcinoma.
SARAH was a multicentre, open-label, randomised, controlled, investigator-initiated, phase 3 trial done at 25 centres specialising in liver diseases in France. Patients were eligible if they were aged at least 18 years with a life expectancy greater than 3 months, had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, Child-Pugh liver function class A or B score of 7 or lower, and locally advanced hepatocellular carcinoma (Barcelona Clinic Liver Cancer BCLC stage C), or new hepatocellular carcinoma not eligible for surgical resection, liver transplantation, or thermal ablation after a previously cured hepatocellular carcinoma (cured by surgery or thermoablative therapy), or hepatocellular carcinoma with two unsuccessful rounds of transarterial chemoembolisation. Patients were randomly assigned (1:1) by a permutated block method with block sizes two and four to receive continuous oral sorafenib (400 mg twice daily) or SIRT with 90Y-loaded resin microspheres 2–5 weeks after randomisation. Patients were stratified according to randomising centre, ECOG performance status, previous transarterial chemoembolisation, and presence of macroscopic vascular invasion. The primary endpoint was overall survival. Analyses were done on the intention-to-treat population; safety was assessed in all patients who received at least one dose of sorafenib or underwent at least one of the SIRT work-up exams. This study has been completed and the final results are reported here. The trial is registered with ClinicalTrials.gov, number NCT01482442.
Between Dec 5, 2011, and March 12, 2015, 467 patients were randomly assigned; after eight patients withdrew consent, 237 were assigned to SIRT and 222 to sorafenib. In the SIRT group, 53 (22%) of 237 patients did not receive SIRT; 26 (49%) of these 53 patients were treated with sorafenib. Median follow-up was 27·9 months (IQR 21·9–33·6) in the SIRT group and 28·1 months (20·0–35·3) in the sorafenib group. Median overall survival was 8·0 months (95% CI 6·7–9·9) in the SIRT group versus 9·9 months (8·7–11·4) in the sorafenib group (hazard ratio 1·15 95% CI 0·94–1·41 for SIRT vs sorafenib; p=0·18). In the safety population, at least one serious adverse event was reported in 174 (77%) of 226 patients in the SIRT group and in 176 (82%) of 216 in the sorafenib group. The most frequent grade 3 or worse treatment-related adverse events were fatigue (20 9% vs 41 19%), liver dysfunction (25 11% vs 27 13%), increased laboratory liver values (20 9% vs 16 7%), haematological abnormalities (23 10% vs 30 14%), diarrhoea (three 1% vs 30 14%), abdominal pain (six 3% vs 14 6%), increased creatinine (four 2% vs 12 6%), and hand-foot skin reaction (one <1% vs 12 6%). 19 deaths in the SIRT group and 12 in the sorafenib group were deemed to be treatment related.
In patients with locally advanced or intermediate-stage hepatocellular carcinoma after unsuccessful transarterial chemoembolisation, overall survival did not significantly differ between the two groups. Quality of life and tolerance might help when choosing between the two treatments.
Sirtex Medical Inc.
MAF bZIP transcription factor G (MAFG) is activated by the farnesoid X receptor to repress bile acid synthesis. However, expression of MAFG increases during cholestatic liver injury in mice and in ...cholangiocarcinomas. MAFG interacts directly with methionine adenosyltransferase α1 (MATα1) and other transcription factors at the E-box element to repress transcription. We studied mechanisms of MAFG up-regulation in cholestatic tissues and the pathways by which S-adenosylmethionine (SAMe) and ursodeoxycholic acid (UDCA) prevent the increase in MAFG expression. We also investigated whether obeticholic acid (OCA), an farnesoid X receptor agonist, affects MAFG expression and how it contributes to tumor growth in mice.
We obtained 7 human cholangiocarcinoma specimens and adjacent non-tumor tissues from patients that underwent surgical resection in California and 113 hepatocellular carcinoma (HCC) specimens and adjacent non-tumor tissues from China, along with clinical data from patients. Tissues were analyzed by immunohistochemistry. MAT1A, MAT2A, c-MYC, and MAFG were overexpressed or knocked down with small interfering RNAs in MzChA-1, KMCH, Hep3B, and HepG2 cells; some cells were incubated with lithocholic acid (LCA, which causes the same changes in gene expression observed during chronic cholestatic liver injury in mice), SAMe, UDCA (100 μM), or farnesoid X receptor agonists. MAFG expression and promoter activity were measured using real-time polymerase chain reaction, immunoblot, and transient transfection. We performed electrophoretic mobility shift, and chromatin immunoprecipitation assays to study proteins that occupy promoter regions. We studied mice with bile-duct ligation, orthotopic cholangiocarcinomas, cholestasis-induced cholangiocarcinoma, diethylnitrosamine-induced liver tumors, and xenograft tumors.
LCA activated expression of MAFG in HepG2 and MzChA-1 cells, which required the activator protein-1, nuclear factor–κB, and E-box sites in the MAFG promoter. LCA reduced expression of MAT1A but increased expression of MAT2A in cells. Overexpression of MAT2A increased activity of the MAFG promoter, whereas knockdown of MAT2A reduced it. MAT1A and MAT2A had opposite effects on the activator protein-1, nuclear factor–κB, and E-box–mediated promoter activity. Expression of MAFG and MAT2A increased, and expression of MAT1A decreased, in diethylnitrosamine-induced liver tumors in mice. SAMe and UDCA had shared and distinct mechanisms of preventing LCA-mediated increased expression of MAFG. OCA increased expression of MAFG, MAT2A, and c-MYC, but reduced expression of MAT1A. Incubation of human liver and biliary cancer cells lines with OCA promoted their proliferation; in nude mice given OCA, xenograft tumors were larger than in mice given vehicle. Levels of MAFG were increased in human HCC and cholangiocarcinoma tissues compared with non-tumor tissues. High levels of MAFG in HCC samples correlated with hepatitis B, vascular invasion, and shorter survival times of patients.
Expression of MAFG increases in cells and tissues with cholestasis, as well as in human cholangiocarcinoma and HCC specimens; high expression levels correlate with tumor progression and reduced survival time. SAMe and UDCA reduce expression of MAFG in response to cholestasis, by shared and distinct mechanisms. OCA induces MAFG expression, cancer cell proliferation, and growth of xenograft tumors in mice.
DNA damage triggers diverse cancers, particularly hepatocellular carcinoma (HCC), but the intrinsic link between DNA damage and tumorigenesis remains unclear. Because of its role as an epigenetic and ...transcriptional regulator, histone deacetylase 3 (HDAC3) is essential for DNA damage control and is often aberrantly expressed in human HCC. In this study, we used individual class I HDAC member-deficient mice to demonstrate that K9 in histone H3 (H3K9), which is the critical site for the assembly of DNA damage response complexes, is exclusively targeted by HDAC3. Ablation of HDAC3 disrupted the deacetylation and consequent trimethylation of H3K9 (H3K9me3), the first step in double-strand break repair, and led to the accumulation of damaged DNA. Simultaneously, hyperacetylated H3K9 (H3K9ac) served as a transcriptional activator and enhanced multiple signaling pathways to promote tumorigenesis. Together, these results show that HDAC3 targets the H3K9ac/H3K9me3 transition to serve as a critical regulator that controls both DNA damage repair and the transcription of many tumor-related genes. Moreover, these findings provide novel insights into the link between DNA damage and transcriptional reprogramming in tumorigenesis. SIGNIFICANCE: These findings show that HDAC3 exclusively regulates H3K9ac in response to DNA damage, and loss of HDAC3 activity shifts the balance from DNA damage control to protumorigenic transcriptional activity.
The liver is the sixth most common site of primary cancer in humans, and generally arises in a background of cirrhosis and inflammation. Moreover, the liver is frequently colonized by metastases from ...cancers of other organs (particularly the colon) because of its anatomical location and organization, as well as its unique metabolic and immunosuppressive environment. In this Review, we discuss how the hepatic microenvironment adapts to pathologies characterized by chronic inflammation and metabolic alterations. We illustrate how these immunological or metabolic changes alter immunosurveillance and thus hinder or promote the development of primary liver cancer. In addition, we describe how inflammatory and metabolic niches affect the spreading of cancer metastases into or within the liver. Finally, we review the current therapeutic options in this context and the resulting challenges that must be surmounted.
The burden of hepatocellular carcinoma (HCC), the most common form of liver cancer, is steadily growing because obesity, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD) are replacing ...viral- and alcohol-related liver disease as major pathogenic promoters. The most worrisome aspects of these new risk factors are their large spread in the general population and their link with HCC arising in noncirrhotic livers. HCC may be the presenting feature of an asymptomatic nonalcoholic steatohepatitis (NASH), the progressive form of NAFLD. The HCC risk connected to metabolic factors has been underestimated so far, and a poorer surveillance has prevented an adequate treatment. Systemic and hepatic molecular mechanisms involved in obesity- and NAFLD-induced hepatocarcinogenesis as well as potential early markers of HCC are being extensively investigated. This review summarizes current evidence linking obesity, NAFLD and liver cancer, discusses its clinical impact and describes the main mechanisms underlying this complex relationship.
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