Regulation of iron metabolism-related genes in diethylnitrosamine-induced mouse liver tumors

Iron metabolism in a mouse model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains the most prevalent type of primary liver cancer worldwide. p53 is one of the most frequently mutated tumor-suppressor genes in HCC and its deficiency in hepatocytes triggers tumor formation in mice. To investigate iron metabolism during liver carcinogenesis, we employed a model of chronic carbon tetrachloride injections in liver-specific p53-deficient mice to induce liver fibrosis, cirrhosis and subsequent carcinogenesis. A transcriptome analysis of liver carcinoma was employed to identify p53-dependent gene expression signatures with subsequent in-depth analysis of iron metabolic parameters being conducted locally within liver cancers and at systemic levels. We show that all mutant mice developed liver cancer by 36-weeks of age in contrast to 3.4% tumors identified in control mice. All liver cancers with a p53-deficient background exhibited a local iron-poor phenotype with a "high transferrin receptor 1 (Tfr1) and low hepcidin (Hamp)" signature. At systemic levels, iron deficiency was restricted to female mice. Additionally, liver tumorigenesis correlated with selective deficits of selenium, zinc and manganese. Our data show that iron deficiency is a prevalent phenomenon in p53-deficient liver cancers, which is associated with alterations in Hamp and Tfr1 and a poor prognosis in mice and patients.

Prognostic 7-SLC-Gene Signature Identified via Weighted Gene Co-Expression Network Analysis for Patients with Hepatocellular Carcinoma

Background

Solute carrier (SLC) proteins play an important role in tumor metabolism. But SLC-associated genes' prognostic significance in hepatocellular carcinoma (HCC) remained elusive. We identified SLC-related factors and developed an SLC-related classifier to predict and improve HCC prognosis and treatment.

Methods

From the TCGA database, corresponding clinical data and mRNA expression profiles of 371 HCC patients were acquired, and those of 231 tumor samples were derived from the ICGC database. Genes associated with clinical features were filtered using weighted gene correlation network analysis (WGCNA). Next, univariate LASSO Cox regression studies developed SLC risk profiles, with the ICGC cohort data being used in validation.

Result

Univariate Cox regression analysis revealed that 31 SLC genes (P < 0.05) were related to HCC prognosis. 7 (SLC22A25, SLC2A2, SLC41A3, SLC44A1, SLC48A1, SLC4A2, and SLC9A3R1) of these genes were applied in developing a SLC gene prognosis model. Samples were classified into the low-andhigh-risk groups by the prognostic signature, with those in the high-risk group showing a significantly worse prognosis (P < 0.001 in the TCGA cohort and P=0.0068 in the ICGC cohort). ROC analysis validated the signature's prediction power. In addition, functional analyses showed enrichment of immune-related pathways and different immune status between the two risk groups.

Conclusion

The 7-SLC-gene prognostic signature established in this study helped predict the prognosis, and was also correlated with the tumor immune status and infiltration of different immune cells in the tumor microenvironment. The current findings may provide important clinical indications for proposing a novel combination therapy consists of targeted anti-SLC therapy and immunotherapy for HCC patients.

Loss of SLC46A1 decreases tumor iron content in hepatocellular carcinoma

It is interesting that high iron is an independent inducer or cofactor of hepatocellular carcinoma (HCC) while the amount of iron is decreased in the liver tumor tissues. Due to the previous findings that iron deficiency promoted HCC metastasis, it is of significance to identify the underlying mechanism of iron deficiency in HCC. The tumor iron content and expressions of iron-metabolic molecules were observed in the primary liver cancers of rats and mice. The molecules that changed independently of iron were identified by comparing the expression profiles in the human HCC tissues and iron-deprived HCC cells. The downstream effects of these molecules on regulating intracellular iron content were investigated in vitro and further validated in vivo. Both in primary liver cancers of rats and mice, we confirmed the decreased iron content in tumor tissues and the altered expressions of iron-metabolic molecules, including transferrin receptor 1 (TfR1), six-transmembrane epithelial antigen of prostate 3 (STEAP3), divalent metal transporter 1 (DMT1), SLC46A1, ferroportin, hepcidin, and ferritin. Among these, STEAP3, DMT1, and SLC46A1 were altered free of iron deficiency. However, only silence or overexpression of SLC46A1 controlled the intracellular iron content of HCC cells. The interventions of STEAP3 or DMT1 could not change the intracellular iron content. Lentivirus-mediated regain of SLC46A1 expression restored the iron content in orthotopically implanted tumors, with correspondingly changes in the iron-metabolic molecules as iron increasing. Conclusion: Taken together, these results suggest that the loss of SLC46A1 expression leads to iron deficiency in liver tumor tissues, which would be an effective target to manage iron homeostasis in HCC.

Hepcidin in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common reasons for cancer-related deaths. Excess iron increases HCC risk. Inevitably, hepcidin, the iron hormone that maintains systemic iron homoeostasis is involved in HCC pathology. Distinct from other cancers that show high hepcidin expression, HCC patients can show low hepcidin levels. Thus, it is of immense clinical benefit to address the regulation and action of hepcidin in HCC as this may help in identifying molecular targets for diagnosis, prognosis, and therapeutics. Accordingly, this review explores hepcidin in HCC. It presents the levels of tissue and serum hepcidin and explains the mechanisms that contribute to hepcidin reduction in HCC. These include downregulation of HAMP, TfR2, HJV, ALK2 and circular RNA circ_0004913, upregulation of matriptase-2 and GDF15, inactivation of RUNX3 and mutation in TP53. The enigmas around mir-122 and the functionalities of two major hepcidin inducers BMP6 and IL6 in relation to hepcidin in HCC are discussed. Effects of hepcidin downregulation are explained, specifically, increased cancer proliferation via activation of CDK1/STAT3 pathway and increased HCC risk due to reduction in a hepcidin-mediated protective effect against hepatic stellate cell activation. Hepcidin–ferroportin axis in HCC is addressed. Finally, the role of hepcidin in the diagnosis, prognosis and therapeutics of HCC is highlighted.

Solute carriers as potential oncodrivers or suppressors: their key functions in malignant tumor formation

Solute carrier (SLC) transporters are primarily known for their function in the transportation of various exogenous/endogenous substances via influx/efflux mechanisms. In addition to their diverse role in several tumor-modulating functions, such as proliferation, migration, angiogenesis, epithelial-mesenchymal transition (EMT), epigenetic modification, chemoresistance, immunoregulation, and oncometabolism, influx/efflux-independent contributions of SLCs in the activation of various signaling network cascades that might drive metastatic tumor formation have also been uncovered. Disappointingly, even after two decades and the discovery of >450 SLCs, many of their members remain orphans in terms of cancer pathogenesis. In this review, we summarize the current understanding of the tumor-modulating functions, mechanisms, and complexity of SLCs, as well as their potential as targets for cancer therapy.

Molybdate Attenuates Lipid Accumulation in the Livers of Mice Fed a Diet Deficient in Methionine and Choline

Both lipid accumulation and oxidative stress are major pathologic contributors to the development of hepatic steatosis. Treatment with molybdate reduces hepatic levels of lipids in diabetic rats. Potential activities of molybdate as an antioxidant have also been demonstrated in various animal models. In the present study, we evaluated the effects of sodium molybdate dihydrate (SM) on hepatic steatosis and associated disturbances in a widely used mouse model of the metabolic disease. Male C57Bl/6 mice at 10 weeks of age were fed a diet deficient in methionine and choline (MCD) and bottled water containing SM for four weeks. The SM treatment markedly attenuated MCD-induced accumulation of lipids, mainly triglycerides, in the liver. Lipid catabolic autophagic pathways were activated by SM in the MCD-fed mouse livers, as evidenced by a decreased level of p62 expression. MCD-induced oxidative damage, such as lipid and protein oxidation, was also alleviated by SM in the liver. However, the level of MCD-induced hepatocellular damage was not affected by SM. Taken together, these findings suggest that molybdate can be used in the treatment and prevention of hepatic steatosis without inducing adverse effects in the liver. To the best of our knowledge, this is the first experimental study to investigate the effects of molybdate in non-alcoholic fatty liver disease, and also the first that demonstrates molybdate-induced autophagy.

Solute carrier transporters: potential targets for digestive system neoplasms

Digestive system neoplasms are the leading causes of cancer-related death all over the world. Solute carrier (SLC) superfamily is composed of a series of transporters that are ubiquitously expressed in organs and tissues of digestive systems and mediate specific uptake of small molecule substrates in facilitative manner. Given the important role of SLC proteins in maintaining normal functions of digestive system, dysregulation of these protein in digestive system neoplasms may deliver biological and clinical significance that deserves systemic studies. In this review, we critically summarized the recent advances in understanding the role of SLC proteins in digestive system neoplasms. We highlighted that several SLC subfamilies, including metal ion transporters, transporters of glucose and other sugars, transporters of urea, neurotransmitters and biogenic amines, ammonium and choline, inorganic cation/anion transporters, transporters of nucleotide, amino acid and oligopeptide organic anion transporters, transporters of vitamins and cofactors and mitochondrial carrier, may play important roles in mediating the initiation, progression, metastasis, and chemoresistance of digestive system neoplasms. Proteins in these SLC subfamilies may also have diagnostic and prognostic values to particular cancer types. Differential expression of SLC proteins in tumors of digestive system was analyzed by extracting data from human cancer database, which revealed that the roles of SLC proteins may either be dependent on the substrates they transport or be tissue specific. In addition, small molecule modulators that pharmacologically regulate the functions of SLC proteins were discussed for their possible application in the treatment of digestive system neoplasms. This review highlighted the potential of SLC family proteins as drug target for the treatment of digestive system neoplasms.

Cardiovascular, liver, and renal toxicity associated with an intravenous ferric carboxymaltose similar versus the originator compound

Background

Ferric carboxymaltose (FCM) is a stable, non-dextran-based intravenous iron complex used to treat iron deficiency of various etiologies. As FCM is a nonbiological complex drug and cannot be fully characterized by physicochemical analyses, it is important to demonstrate in nonclinical models that FCM similars (FCMS) have similar biodistribution.

Materials and methods

A total of 30 nonanemic rats were treated weekly with 40 mg iron/kg body weight intravenous FCM, FCMS, or isotonic saline (controls) for 4 weeks. Blood pressure, liver enzymes, and renal function were evaluated. In liver, heart, and kidney tissue, markers for oxidative stress (malondialdehyde to assess lipid peroxidation and antioxidant enzymes) and inflammation (TNFα and IL6) were measured. Iron deposits were localized.

Results

The FCMS-treated group had significantly lower blood pressure, higher liver enzymes, increased proteinuria, and reduced creatinine clearance versus the FCM and control groups by day 29. Serum iron and transferrin saturation were significantly higher with FCMS versus FCM or controls. Iron deposition was altered in FCMS-treated animals, with decreased ferritin deposits and iron deposition outside the physiological storage compartments. Markers for lipid peroxidation and antioxidant-enzyme activity were significantly increased after FCMS administration versus FCM and controls, as were inflammatory markers.

Conclusion

Results from this blinded nonclinical study demonstrated significant differences between the originator FCM and this FCMS.

Effects of an oral iron chelator, deferasirox, on advanced hepatocellular carcinoma

AIM

To evaluate the inhibitory effects of deferasirox (DFX) against hepatocellular carcinoma (HCC) through basic and clinical studies.

METHODS

In the basic study, the effect of DFX was investigated in three hepatoma cell lines (HepG2, Hep3B, and Huh7), as well as in an N-nitrosodiethylamine-induced murine HCC model. In the clinical study, six advanced HCC patients refractory to chemotherapy were enrolled. The initial dose of DFX was 10 mg/kg per day and was increased by 10 mg/kg per day every week, until the maximum dose of 30 mg/kg per day. The duration of a single course of DFX therapy was 28 consecutive days. In the event of dose-limiting toxicity (according to the Common Terminology Criteria for Adverse Events v.4.0), DFX dose was reduced.

RESULTS

Administration of DFX inhibited the proliferation of hepatoma cell lines and induced the activation of caspase-3 in a dose-dependent manner in vitro. In the murine model, DFX treatment significantly suppressed the development of liver tumors (P < 0.01), and significantly upregulated the mRNA expression levels of hepcidin (P < 0.05), transferrin receptor 1 (P < 0.05), and hypoxia inducible factor-1α (P < 0.05) in both tumor and non-tumor tissues, compared with control mice. In the clinical study, anorexia and elevated serum creatinine were observed in four and all six patients, respectively. However, reduction in DFX dose led to decrease in serum creatinine levels in all patients. After the first course of DFX, one patient discontinued the therapy. We assessed the tumor response in the remaining five patients; one patient exhibited stable disease, while four patients exhibited progressive disease. The one-year survival rate of the six patients was 17%.

CONCLUSION

We demonstrated that DFX inhibited HCC in the basic study, but not in the clinical study due to dose-limiting toxicities.

Dietary Deficiency of Calcium and/or Iron, an Age-Related Risk Factor for Renal Accumulation of Cadmium in Mice

The major route of cadmium (Cd) intake by non-smokers is through food ingestion. Cd is a non-essential metal absorbed through one or more transporters of essential metal ions. Expression of these transporters is affected by nutritional status. To investigate the risk factors for Cd toxicity, the effects of deficiency of essential metals on hepatic and renal accumulation of Cd were studied in mice of different ages. Mice were administered a control diet or one of the essential metal-deficient diets, administered Cd by gavage for 6 weeks, and killed; then, Cd accumulation was evaluated. Iron deficiency (FeDF) or calcium deficiency (CaDF) resulted in remarkable increases in hepatic and renal Cd accumulation compared with control-diet mice and other essential metal-deficient mice. Cd accumulation in hepatic and renal tissue was increased significantly at all ages tested in FeDF and CaDF mice. Renal Cd concentrations were higher in 4-week-old mice than in 8- and 25-week-old mice. Increase in intestinal mRNA expression of calcium transporter (CaT)1, divalent metal ion transporter-1, and metallothionein (MT)1 was also higher in 4-week-old mice than in other mice. Renal accumulation of Cd showed strong correlation with intestinal mRNA expression of CaT1 and MT1. These data suggest that CaDF and FeDF at younger ages can be a risk factor for Cd toxicity.

Clinical features of nonalcoholic fatty liver disease-associated hepatocellular carcinoma

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), especially nonalcoholic steatohepatitis, is a recognized risk factor for hepatocellular carcinoma (HCC). However, detailed analysis of the clinical features in patients with NAFLD and their association with HCC is lacking. This study aimed to update the clinical features of patients with NAFLD-associated HCC.

DATA SOURCES

The clinical data of patients with NAFLD-associated HCC from 25 studies published between 1990 and 2010 in the Pubmed database were comprehensively reviewed.

RESULTS

In a total of 169 patients with NAFLD-associated HCC, 72.8% were male. The median age at abnormal liver function tests and diagnosis of NAFLD and HCC was 60, 64 and 67 years, respectively. Most patients were obese (75%) and diabetic (59.8%), 32.3% had dyslipidemia, and 53% had hypertension. Nearly all patients (98.6%, 71/72) were complicated with at least one metabolic disorder. The majority (76%) of the HCC patients had a solitary tumor nodule, with the tumor size ranging from 0.8 to 20 cm in diameter (mean 3.4 cm). Most (61.1%) of the patients had moderately-differentiated HCC. In 40.2% of the patients, HCC occurred in the absence of cirrhosis. Among 130 patients, 57.7% underwent hepatectomy and 14.6% received liver transplantation. The mean follow-up of the treated patients for 25 months showed that 32.4% (24/74) died and 18.8% (9/48) had recurrence.

CONCLUSIONS

Patients with NAFLD-associated HCC are usually accompanied with metabolic disorders. Regular surveillance in patients with NAFLD for HCC is necessary, especially for elderly men with metabolic syndrome.

Human O6 -methylguanine-DNA methyltransferase containing C145A does not prevent hepatocellular carcinoma in C3HeB/FeJ transgenic mice

The prevalence of hepatocellular carcinoma (HCC) was diminished from 60% to 18% at 15 months of age in C3HeB/FeJ male transgenic mice expressing hMGMT in our previous studies. To directly test if the methyltransferase activity is required for diminished tumor prevalence, two separate lines of transgenic mice bearing an enzymatically inactive form of hMGMT were used. In these lines, cysteine 145 was substituted with alanine (C145A). Expression of the hMGMT C145A transgene in liver was demonstrated by Northern blots and Western blots. Immunohistochemistry revealed predominantly nuclear localization of the hMGMT C145A protein. hMGMT C145A transgenic mice were crossed with lacI transgenic mice to assess mutant frequencies in the presence of the mutant protein. Mutant frequencies were similar among livers of lacI × hMGMT C145A bi-transgenic mice and lacI × wild-type (WT) mice. DNA sequence analysis of recovered lacI mutants revealed similar mutation spectra for hMGMT C145A and WT mice. The prevalence of HCC was also similar for the two tested lines of hMGMT C145A mice, 45% and 48% prevalence with median tumor sizes of 11 and 8 mm, and WT mice, 40% prevalence and median tumor size of 10 mm. These results provide evidence that residue C145 in hMGMT is required to reduce the prevalence of HCC in C3HeB/FeJ mice transgenic for hMGMT.

Chronic administration of 2-acetylaminofluorene alters the cellular iron metabolism in rat liver

Dysregulated intracellular iron homeostasis has been found not only in rodent and human hepatocellular carcinomas but also in several preneoplastic pathological states associated with hepatocarcinogenesis; however, the precise underlying mechanisms of metabolic iron disturbances in preneoplastic liver and the role of these disturbances remain unexplored. In the present study, using an in vivo model of rat hepatocarcinogenesis induced by 2-acetylaminofluorene, we found extensive alterations in cellular iron metabolism at preneoplastic stages of liver carcinogenesis. These were characterized by a substantial decrease in the levels of cytoplasmic non-heme iron in foci of initiated hepatocytes and altered expression of the major genes responsible for the proper maintenance of intracellular iron homeostasis. Gene expression analysis revealed that the decreased intracellular levels of iron in preneoplastic foci might be attributed to increased iron export from the cells, driven by upregulation of ferroportin (Fpn1), the only known non-heme iron exporter. Likewise, increased Fpn1 gene expression was found in vitro in TRL1215 rat liver cells with an acquired malignant phenotype, suggesting that upregulation of Fpn1 might be a specific feature of neoplastically transformed cells. Other changes observed in vivo included the downregulation of hepcidin (Hamp) gene, a key regulator of Fpn1, and this was accompanied by decreased levels of CCAAT/enhancer binding proteins alpha and beta, especially at the Hamp promoter. In conclusion, our results demonstrate the significance of altered intracellular iron metabolism in the progression of liver carcinogenesis and suggest that correction of these alterations could possibly affect liver cancer development.