Loss of KDM6B epigenetically confers resistance to lipotoxicity in nonalcoholic fatty liver disease-related HCC

BACKGROUND

NAFLD caused by abnormalities in hepatic lipid metabolism is associated with an increased risk of developing HCC. The molecular mechanisms underlying the progression of NAFLD-related HCC are not fully understood. We investigated the molecular mechanism and role of KDM6B downregulation in NAFLD-related HCC after the KDM6B gene was identified using microarray analysis as commonly downregulated in mouse NAFLD-related HCC and human nonhepatitis B and nonhepatitis C viral-HCC.

METHODS

The 5-hydroxymethylcytosine levels of KDM6B in HCC cells were determined using glycosylated hydroxymethyl-sensitive PCR. Microarray and chromatin immunoprecipitation analyses using KDM6B-knockout (KO) cells were used to identify KDM6B target genes. Lipotoxicity was assessed using a palmitate-treated cell proliferation assay. Immunohistochemistry was used to evaluate KDM6B expression in human HCC tissues.

RESULTS

KDM6B expression levels in HCC cells correlated with the 5-hydroxymethylcytosine levels in the KDM6B gene body region. Gene set enrichment analysis revealed that the lipid metabolism pathway was suppressed in KDM6B-KO cells. KDM6B-KO cells acquired resistance to lipotoxicity (p < 0.01) and downregulated the expression of G0S2, an adipose triglyceride lipase/patatin like phospholipase domain containing 2 (ATGL/PNPLA2) inhibitor, through increased histone H3 lysine-27 trimethylation levels. G0S2 knockdown in KDM6B-expressed HCC cells conferred lipotoxicity resistance, whereas ATGL/PNPLA2 inhibition in the KDM6B-KO cells reduced these effects. Immunohistochemistry revealed that KDM6B expression was decreased in human NAFLD-related HCC tissues (p < 0.001), which was significantly associated with decreased G0S2 expression (p = 0.032).

CONCLUSIONS

KDM6B-disrupted HCC acquires resistance to lipotoxicity via ATGL/PNPLA2 activation caused by epigenetic downregulation of G0S2 expression. Reduced KDM6B and G0S2 expression levels are common in NAFLD-related HCC. Targeting the KDM6B-G0S2-ATGL/PNPLA2 pathway may be a useful therapeutic strategy for NAFLD-related HCC.

Loss of SFXN1 mitigates lipotoxicity and predicts poor outcome in non-viral hepatocellular carcinoma

Hepatocellular carcinoma (HCC) imposes a huge global burden, arising from various etiological factors such as hepatitis virus infection and metabolic syndrome. While prophylactic vaccination and antiviral treatment have decreased the incidence of viral HCC, the growing prevalence of metabolic syndrome has led to an increase in non-viral HCC. To identify genes downregulated and specifically associated with unfavorable outcome in non-viral HCC cases, screening analysis was conducted using publically available transcriptome data. Among top 500 genes meeting the criteria, which were involved in lipid metabolism and mitochondrial function, a serine transporter located on inner mitochondrial membrane SFXN1 was highlighted. SFXN1 protein expression was significantly reduced in 33 of 105 HCC tissue samples, and correlated to recurrence-free and overall survival only in non-viral HCC. Human HCC cells with SFXN1 knockout (KO) displayed higher cell viability, lower fat intake and diminished reactive oxygen species (ROS) production in response to palmitate administration. In a subcutaneous transplantation mouse model, high-fat diet feeding attenuated tumorigenic potential in the control cells, but not in the SFXN1-KO cells. In summary, loss of SFXN1 expression suppresses lipid accumulation and ROS generation, preventing toxic effects from fat overload in non-viral HCC, and predicts clinical outcome of non-viral HCC patients.

RTP4 silencing provokes tumor-intrinsic resistance to immune checkpoint blockade in colorectal cancer

BACKGROUND

Recent advances in immune checkpoint blockade (ICB) have improved patient prognosis in mismatch repair-deficient and microsatellite instability-high colorectal cancer (dMMR/MSI-H CRC); however, PD-1 blockade has faced a challenge in early progressive disease. We aimed to understand the early event in ICB resistance using an in vivo model.

METHODS

We subcutaneously transplanted the MC38 colon cancer cells into C57BL/6 mice, intraperitoneally injected anti-PD-1 antibody and then isolated ICB-resistant subclones from the recurrent tumors.

RESULTS

Comparative gene expression analysis discovered seven genes significantly downregulated in the ICB-resistant cells. Tumorigenicity assay of the MC38 cells knocked out each of the seven candidate genes into C57BL/6 mice treated with anti-PD-1 antibody and bioinformatics analysis of the relationship between the expression of the seven candidate genes and the outcome of cancer patients receiving immunotherapy identified Rtp4, an interferon-stimulated gene and a chaperon protein of G protein-coupled receptors, as a gene involved in ICB resistance. Immunohistochemical analysis of transplanted tumor tissues demonstrated that anti-PD-1 antibody failed to recruit T lymphocytes in the Rtp4-KO MC38 cells. Mouse and human RTP4 expression could be silenced via histone H3 lysine 9 (H3K9) trimethylation, and public transcriptome data indicated the high expression level of RTP4 in most but not all of dMMR/MSI-H CRC.

CONCLUSIONS

We clarified that RTP4 could be silenced by histone H3K9 methylation as the early event of ICB resistance. RTP4 expression could be a promising biomarker for predicting ICB response, and the combination of epigenetic drugs and immune checkpoint inhibitors might exhibit synergistic effects on dMMR/MSI-H CRC.

Identification of a novel target of SETD1A histone methyltransferase and the clinical significance in pancreatic cancer

Although histone H3K4 methyltransferase SETD1A is overexpressed in various cancer types, the molecular mechanism underlying its overexpression and its target genes in pancreatic ductal adenocarcinoma (PDAC) remain unclarified. We conducted immunohistochemical staining for SETD1A in 105 human PDAC specimens to assess the relationship between SETD1A overexpression and clinicopathological features. The function and target genes of SETD1A were investigated using human pancreatic cancer cell lines. SETD1A expression was upregulated in 51.4% of patients with PDAC and was an independent prognostic factor associated with shorter disease-free survival after resection (p < 0.05). Knockdown and overexpression of SETD1A showed that SETD1A plays a crucial role in increasing the proliferation and motility of PDAC cells. SETD1A overexpression increased tumorigenicity. RNA sequencing of SETD1A-knockdown cells revealed downregulation of RUVBL1, an oncogenic protein ATP-dependent DNA helicase gene. ChIP analysis revealed that SETD1A binds to the RUVBL1 promoter region, resulting in increased H3K4me3 levels. Knockdown of RUVBL1 showed inhibition of cell proliferation, migration, and invasion of PDAC cells, which are similar biological effects to SETD1A knockdown. High expression of both SETD1A and RUVBL1 was an independent prognostic factor not only for disease-free survival but also for overall survival (p < 0.05). In conclusion, we identified RUVBL1 as a novel downstream target gene of the SETD1A-H3K4me3 pathway. Co-expression of SETD1A and RUVBL1 is an important factor for predicting the prognosis of patients with PDAC.

Inhibition of acid ceramidase elicits mitochondrial dysfunction and oxidative stress in pancreatic cancer cells

Although the inhibition of acid ceramidase (AC) is known to induce antitumor effects in various cancers, there are few reports in pancreatic cancer, and the underlying mechanisms remain unclear. Moreover, there is currently no safe administration method of AC inhibitor. Here the effects of gene therapy using siRNA and shRNA for AC inhibition with its mechanisms for pancreatic cancer were investigated. The inhibition of AC by siRNA and shRNA using an adeno-associated virus 8 (AAV8) vector had antiproliferative effects by inducing apoptosis in pancreatic cancer cells and xenograft mouse model. Acid ceramidase inhibition elicits mitochondrial dysfunction, reactive oxygen species accumulation, and manganese superoxide dismutase suppression, resulting in apoptosis of pancreatic cancer cells accompanied by ceramide accumulation. These results elucidated the mechanisms underlying the antitumor effect of AC inhibition in pancreatic cancer cells and suggest the potential of the AAV8 vector to inhibit AC as a therapeutic strategy.

Molecular and immunological paradigms of hepatocellular carcinoma: Special reference to therapeutic approaches

The development of hepatocellular carcinoma (HCC) is a multistep process with a complex interaction of various genetic backgrounds and the tumor microenvironment. In addition to the development of rational approaches to epidemiologic research, early detection, and diagnosis, considerable progress has been made in systemic treatment with molecular-targeted agents for patients with advanced HCC. Moreover, encouraging reports of recent clinical trials of combination therapy with immune-checkpoint inhibitors (ICIs) has raised high hopes. Each HCC is the result of a unique combination of somatic alterations, including genetic, epigenetic, transcriptomic, and metabolic events, leading to conclusive tumoral heterogeneity. Recent advances in comprehensive genetic analysis have accelerated molecular classification and defined subtypes with specific characteristics, including immune-associated molecular profiles reflecting the immune reactivity in the tumor. In considering the development of therapeutic strategies in combination with immunotherapy, proper interpretation of molecular pathological characterization could lead to effective therapeutic deployment and enable individualization of the management of HCC. Here, we review distinctive molecular alterations in the subtype classification of HCC, current therapies, and representative clinical trials with alternative immune-combination approaches from a molecular pathological point.

Loss of miR-100 and miR-125b results in cancer stem cell properties through IGF2 upregulation in hepatocellular carcinoma

Stemness factors control microRNA expression in cancer stem cells. Downregulation of miR-100 and miR-125b is associated with tumor progression and prognosis of various cancers. Comparing miRNA profiling of patient-derived tumorsphere (TS) and adherent (2D) hepatocellular carcinoma cells, miR-100 and miR-125b are identified to have association with stemness. In TS cells, miR-100 and miR-125b were downregulated comparing to 2D cells. The finding was reproduced in Hep3B cells. Overexpression of stemness factors NANOG, OCT4 and SOX2 by introduction of gene constructs in Hep3B cells suppressed these two miRNA expression levels. Treatment of chromeceptin, an IGF signaling pathway inhibitor, decreased numbers of TS and inhibited the AKT/mTOR pathway. Stable cell line of miR-100 and miR-125b overexpression decreased IGF2 expression and inhibited tumor growth in the xenograft model. In conclusion, miR-100 and miR-125b have tumor suppressor role in hepatocellular carcinoma through inhibiting IGF2 expression and activation of the AKT/mTOR pathway.

Loss of ARID1A induces a stemness gene ALDH1A1 expression with histone acetylation in the malignant subtype of cholangiocarcinoma

Genomic analyses have recently discovered the malignant subtype of human intrahepatic cholangiocarcinoma (ICC) characterized by frequent mutations of chromatin remodeling gene ARID1A; however, the biological and molecular functions still remain obscure. We here examined the clinical and biological significances of ARID1A deficiency in human ICC. Immunohistochemical analysis demonstrated that the loss of ARID1A was an independent prognostic factor for overall survival of ICC patients (P = 0.023). We established ARID1A-knockout (KO) cells by using the CRISPR/Cas9 system from two human cholangiocarcinoma cell lines. ARID1A-KO cells exhibited significantly enhanced migration, invasion, and sphere formation activity. Microarray analysis revealed that ALDH1A1, a stemness gene, was the most significantly elevated genes in ARID1A-KO cells. In addition, ALDH enzymatic activity as a hallmark of cancer stem cells was markedly high in the KO cells. ARID1A and histone deacetylase 1 were directly recruited to the ALDH1A1 promoter region in cholangiocarcinoma cells with undetectable ALDH1A1 expression by chromatin immunoprecipitation assay. The histone H3K27 acetylation level at the ALDH1A1 promoter region was increased in cells when ARID1A was disrupted (P < 0.01). Clinically, inverse correlation between ARID1A and ALDH1A1 expression was also identified in primary ICC (P = 0.018), and ARID1A-negative and ALDH1A1-positve ICCs showed worse prognosis than only ARID1A-negative cases (P = 0.002). In conclusion, ARID1A may function as a tumor suppressor in ICC through transcriptional downregulation of ALDH1A1 expression with decreasing histone H3K27 acetylation. Our studies provide the basis for the development of new epigenetic approaches to ARID1A-negative ICC. Immunohistochemical loss of ARID1A is an independent prognostic factor in intrahepatic cholangiocarcinoma patients. ARID1A recruits HDAC1 to the promoter region of ALDH1A1, a stemness gene, and epigenetically suppresses ALDH1A1 expression with decreasing histone H3K27 acetylation in cholangiocarcinoma cells.

Classification of primary liver cancer with immunosuppression mechanisms and correlation with genomic alterations

BACKGROUND

The tumor microenvironment can be classified into immunologically active "inflamed" tumors and inactive "non-inflamed" tumors based on the infiltration of cytotoxic immune cells. Previous studies on liver cancer have reported a superior prognosis for inflamed tumors compared to non-inflamed tumors. However, liver cancer is highly heterogeneous immunologically and genetically, and a finer classification of the liver cancer microenvironment may improve our understanding of its immunological diversity and response to immune therapy.

METHODS

We characterized the immune gene signatures of 234 primary liver cancers, mainly virus-related, from a Japanese population using RNA-Seq of tumors and matched non-tumorous hepatitis livers. We then compared them with the somatic alterations detected using the whole-genome sequencing.

FINDINGS

Liver cancers expressed lower levels of immune marker genes than non-tumorous hepatitis livers, indicating immunosuppression in the tumor microenvironment. Several immunosuppression mechanisms functioned actively and mutually exclusively, resulting in four immune subclasses of liver cancer: tumor-associated macrophage (TAM), CTNNB1, cytolytic activity (CYT), and regulatory T cell (Treg). The CYT and Treg subclasses represented inflamed tumors, while the TAM and CTNNB1 subclasses represented non-inflamed tumors. The TAM subclass, which comprised 31% of liver cancers, showed a poor survival, expressed elevated levels of extracellular matrix genes, and was associated with somatic mutations of chromatin regulator ARID2. The results of cell line experiments suggested a functional link between ARID2 and chemokine production by liver cancer cells.

INTERPRETATION

Primary liver cancer was classified into four subclasses based on mutually exclusive mechanisms for immunosuppression. This classification indicate the importance of immunosuppression mechanisms, such as TAM and Treg, as therapeutic targets for liver cancer.

FUNDING

The Japan Agency for Medical Research and Development (AMED).

Classification of primary liver cancer with immunosuppression mechanisms and correlation with genomic alterations

BACKGROUND

The tumor microenvironment can be classified into immunologically active "inflamed" tumors and inactive "non-inflamed" tumors based on the infiltration of cytotoxic immune cells. Previous studies on liver cancer have reported a superior prognosis for inflamed tumors compared to non-inflamed tumors. However, liver cancer is highly heterogeneous immunologically and genetically, and a finer classification of the liver cancer microenvironment may improve our understanding of its immunological diversity and response to immune therapy.

METHODS

We characterized the immune gene signatures of 234 primary liver cancers, mainly virus-related, from a Japanese population using RNA-Seq of tumors and matched non-tumorous hepatitis livers. We then compared them with the somatic alterations detected using the whole-genome sequencing.

FINDINGS

Liver cancers expressed lower levels of immune marker genes than non-tumorous hepatitis livers, indicating immunosuppression in the tumor microenvironment. Several immunosuppression mechanisms functioned actively and mutually exclusively, resulting in four immune subclasses of liver cancer: tumor-associated macrophage (TAM), CTNNB1, cytolytic activity (CYT), and regulatory T cell (Treg). The CYT and Treg subclasses represented inflamed tumors, while the TAM and CTNNB1 subclasses represented non-inflamed tumors. The TAM subclass, which comprised 31% of liver cancers, showed a poor survival, expressed elevated levels of extracellular matrix genes, and was associated with somatic mutations of chromatin regulator ARID2. The results of cell line experiments suggested a functional link between ARID2 and chemokine production by liver cancer cells.

INTERPRETATION

Primary liver cancer was classified into four subclasses based on mutually exclusive mechanisms for immunosuppression. This classification indicate the importance of immunosuppression mechanisms, such as TAM and Treg, as therapeutic targets for liver cancer.

FUNDING

The Japan Agency for Medical Research and Development (AMED).

Upregulation of cancer-associated gene expression in activated fibroblasts in a mouse model of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH), characterized by chronic inflammation and fibrosis, is predicted to be the leading cause of cirrhosis and hepatocellular carcinoma (HCC) in the next decade. Although recent evidence suggests the importance of fibrosis as the strongest determinant of HCC development, the molecular mechanisms underlying NASH-induced carcinogenesis still remain unclear. Here we performed RNA sequencing analysis to compare gene expression profiles of activated fibroblasts prepared from two distinct liver fibrosis models: carbon tetrachloride–induced fibrosis as a model without obesity and HCC and genetically obese melanocortin 4 receptor–deficient (MC4R-KO) mice fed Western diet, which develop steatosis, NASH, and eventually HCC. Our data showed that activated fibroblasts exhibited distinct gene expression patterns in each etiology, and that the ‘pathways in cancer’ were selectively upregulated in the activated fibroblasts from MC4R-KO mice. The most upregulated gene in these pathways was fibroblast growth factor 9 (FGF9), which was induced by metabolic stress such as palmitate. FGF9 exerted anti-apoptotic and pro-migratory effects in fibroblasts and hepatoma cells in vitro and accelerated tumor growth in a subcutaneous xenograft model. This study reveals upregulation of cancer-associated gene expression in activated fibroblasts in NASH, which would contribute to the progression from NASH to HCC.