The insulin-like growth factor (IGF) signaling axis and hepatitis C virus-associated carcinogenesis (review)

Signaling pathways in liver cancer: pathogenesis and targeted therapy

Liver cancer remains one of the most prevalent malignancies worldwide with high incidence and mortality rates. Due to its subtle onset, liver cancer is commonly diagnosed at a late stage when surgical interventions are no longer feasible. This situation highlights the critical role of systemic treatments, including targeted therapies, in bettering patient outcomes. Despite numerous studies on the mechanisms underlying liver cancer, tyrosine kinase inhibitors (TKIs) are the only widely used clinical inhibitors, represented by sorafenib, whose clinical application is greatly limited by the phenomenon of drug resistance. Here we show an in-depth discussion of the signaling pathways frequently implicated in liver cancer pathogenesis and the inhibitors targeting these pathways under investigation or already in use in the management of advanced liver cancer. We elucidate the oncogenic roles of these pathways in liver cancer especially hepatocellular carcinoma (HCC), as well as the current state of research on inhibitors respectively. Given that TKIs represent the sole class of targeted therapeutics for liver cancer employed in clinical practice, we have particularly focused on TKIs and the mechanisms of the commonly encountered phenomena of its resistance during HCC treatment. This necessitates the imperative development of innovative targeted strategies and the urgency of overcoming the existing limitations. This review endeavors to shed light on the utilization of targeted therapy in advanced liver cancer, with a vision to improve the unsatisfactory prognostic outlook for those patients.

Human umbilical cord mesenchymal stem cells protect against ferroptosis in acute liver failure through the IGF1-hepcidin-FPN1 axis and inhibiting iron loading

Acute liver failure (ALF) is a significant global issue with elevated morbidity and mortality rates. There is an urgent and pressing need for secure and effective treatments. Ferroptosis, a novel iron-dependent regulation of cell death, plays a significant role in multiple pathological processes associated with liver diseases, including ALF. Several studies have demonstrated that mesenchymal stem cells (MSCs) have promising therapeutic potential in the treatment of ALF. This study aims to investigate the positive effects of MSCs against ferroptosis in an ALF model and explore the underlying molecular mechanisms of their therapeutic function. Our results show that intravenously injected MSCs protect against ferroptosis in ALF mouse models. MSCs decrease iron deposition in the liver of ALF mice by downregulating hepcidin level and upregulating FPN1 level. MSCs labelled with Dil are mainly observed in the hepatic sinusoid and exhibit colocalization with the macrophage marker CD11b fluorescence. ELISA demonstrates a high level of IGF1 in the CCL 4+MSC group. Suppressing the IGF1 effect by the PPP blocks the therapeutic effect of MSCs against ferroptosis in ALF mice. Furthermore, disruption of IGF1 function results in iron deposition in the liver tissue due to impaired inhibitory effects of MSCs on hepcidin level. Our findings suggest that MSCs alleviate ferroptosis induced by disorders of iron metabolism in ALF mice by elevating IGF1 level. Moreover, MSCs are identified as a promising cell source for ferroptosis treatment in ALF mice.

Hepatocellular carcinoma: signaling pathways, targeted therapy, and immunotherapy

Hepatocellular carcinoma (HCC) is the most common primary liver cancer with a high mortality rate. It is regarded as a significant public health issue because of its complicated pathophysiology, high metastasis, and recurrence rates. There are no obvious symptoms in the early stage of HCC, which often leads to delays in diagnosis. Traditional treatment methods such as surgical resection, radiotherapy, chemotherapy, and interventional therapies have limited therapeutic effects for HCC patients with recurrence or metastasis. With the development of molecular biology and immunology, molecular signaling pathways and immune checkpoint were identified as the main mechanism of HCC progression. Targeting these molecules has become a new direction for the treatment of HCC. At present, the combination of targeted drugs and immune checkpoint inhibitors is the first choice for advanced HCC patients. In this review, we mainly focus on the cutting-edge research of signaling pathways and corresponding targeted therapy and immunotherapy in HCC. It is of great significance to comprehensively understand the pathogenesis of HCC, search for potential therapeutic targets, and optimize the treatment strategies of HCC.

Expressions of Insulin-like Growth Factor System among Different Breeds Impact Piglets' Growth during Weaning

The present study investigated the insulin-like growth factors (IGFs) and their receptors and binding proteins among three pig breeds during weaning. Sixty Duroc (DR), Taoyuan black (TYB), and Xiangcun black (XCB) piglets (20 piglets per breed) were selected at 21 and 24 (3 days of post-weaning) days of age to analyze organ indices, plasma concentrations of IGF and IGF-binding proteins (IGFBPs) using ELISA kits, and gene expression of IGF-system-related components in different tissues. The plasma IGFBP-3 concentration in TYB piglets was higher (p > 0.05) than in the XCB and DR piglets at 21 days of age. At 21 days of age, compared with the DR piglets, the IGF-1 expression was lower (p < 0.05) in the kidney, but it was higher (p < 0.05) in the spleen of XCB and TYB piglets. At 24 days of age, the IGF-1 expression was higher (p < 0.05) in the kidney of TYB piglets than in the XCB and DR piglets, while IGFBP-3 in the stomach and IGFBP-4 in the liver of XCB and TYB piglets were lower (p < 0.05) compared with the DR piglets. Weaning down-regulated (p < 0.05) IGF-1 expression in the jejunum, spleen, and liver of piglets, while it up-regulated (p < 0.05) IGFBP-3 expression in the stomach, IGFBP-4 in the liver, IGFBP-5 in the ileum, and IGFBP-6 in the jejunum of DR piglets. Spearman's correlation analysis showed a negative correlation (p < 0.05) between plasma IGFBP-2 and IGFBP-5 concentration and the organ indices of piglets. Collectively, there were significant differences in the IGF system components among the three pig breeds. The IGF system components were altered during weaning, which might be involved in weaning stress to decrease the growth of piglets.

Metabolic Impact of MKP-2 Upregulation in Obesity Promotes Insulin Resistance and Fatty Liver Disease

The mechanisms connecting obesity with type 2 diabetes, insulin resistance, nonalcoholic fatty liver disease, and cardiovascular diseases remain incompletely understood. The function of MAPK phosphatase-2 (MKP-2), a type 1 dual-specific phosphatase (DUSP) in whole-body metabolism, and how this contributes to the development of diet-induced obesity, type 2 diabetes (T2D), and insulin resistance is largely unknown. We investigated the physiological contribution of MKP-2 in whole-body metabolism and whether MKP-2 is altered in obesity and human fatty liver disease using MKP-2 knockout mice models and human liver tissue derived from fatty liver disease patients. We demonstrate that, for the first time, MKP-2 expression was upregulated in liver tissue in humans with obesity and fatty liver disease and in insulin-responsive tissues in mice with obesity. MKP-2-deficient mice have enhanced p38 MAPK, JNK, and ERK activities in insulin-responsive tissues compared with wild-type mice. MKP-2 deficiency in mice protects against diet-induced obesity and hepatic steatosis and was accompanied by improved glucose homeostasis and insulin sensitivity. Mkp-2^−/− mice are resistant to diet-induced obesity owing to reduced food intake and associated lower respiratory exchange ratio. This was associated with enhanced circulating insulin-like growth factor-1 (IGF-1) and stromal cell-derived factor 1 (SDF-1) levels in Mkp-2^−/− mice. PTEN, a negative regulator of Akt, was downregulated in livers of Mkp-2^−/− mice, resulting in enhanced Akt activity consistent with increased insulin sensitivity. These studies identify a novel role for MKP-2 in the regulation of systemic metabolism and pathophysiology of obesity-induced insulin resistance and fatty liver disease.

Type 2 diabetes mellitus increases liver transplant-free mortality in patients with cirrhosis: A systematic review and meta-analysis

BACKGROUND

The impact of type 2 diabetes mellitus (T2DM) on the prognosis and complications of liver cirrhosis is not fully clarified.

AIM

To clarify the mortality and related risk factors as well as complications in cirrhotic patients with T2DM.

METHODS

We searched PubMed, EMBASE, and the Cochrane Library from their inception to December 1, 2020 for cohort studies comparing liver transplant-free mortality, hepatocellular carcinoma (HCC), ascites, spontaneous bacterial peritonitis (SBP), variceal bleeding, and hepatic encephalopathy (HE) in cirrhotic patients with vs without T2DM. Odds ratios (ORs) were combined by using fixed-effects or random-effects models with RevMan software.

RESULTS

The database search generated a total of 17 cohort studies that met the inclusion criteria. Among these studies, eight reported the risk of mortality, and eight reported the risk of HCC. Three studies provided SBP rates, and two documented ascites rates. Four articles focused on HE rates, and three focused on variceal bleeding rates. Meta-analysis indicated that T2DM was significantly associated with an increased risk of liver transplant-free mortality [OR: 1.28, 95% confidence intervals (CI): 1.16-1.41, P < 0.0001] and HCC incidence (OR: 1.82, 95%CI: 1.32-2.51, P = 0.003). The risk of SBP was not significantly increased (OR: 1.16 95%CI: 0.86-1.57, P = 0.34). Additionally, T2DM did not significantly increase HE (OR: 1.31 95%CI: 0.97-1.77, P = 0.08), ascites (OR: 1.11 95%CI: 0.84-1.46, P = 0.46), and variceal bleeding (OR: 1.34, 95%CI: 0.99-1.82, P = 0.06).

CONCLUSION

The findings suggest that cirrhotic patients with T2DM have a poor prognosis and high risk of HCC. T2DM may not be associated with an increased risk of SBP, variceal bleeding, ascites, or HE in cirrhotic patients with T2DM.

Insulin-Like Growth Factor 2 As a Possible Neuroprotective Agent and Memory Enhancer-Its Comparative Expression, Processing and Signaling in Mammalian CNS

A number of studies performed on rodents suggest that insulin-like growth factor 2 (IGF-2) or its analogs may possibly be used for treating some conditions like Alzheimer’s disease, Huntington’s disease, autistic spectrum disorders or aging-related cognitive impairment. Still, for translational research a comparative knowledge about the function of IGF-2 and related molecules in model organisms (rats and mice) and humans is necessary. There is a number of important differences in IGF-2 signaling between species. In the present review we emphasize species-specific patterns of IGF-2 expression in rodents, humans and some other mammals, using, among other sources, publicly available transcriptomic data. We provide a detailed description of Igf2 mRNA expression regulation and pre-pro-IGF-2 protein processing in different species. We also summarize the function of IGF-binding proteins. We describe three different receptors able to bind IGF-2 and discuss the role of IGF-2 signaling in learning and memory, as well as in neuroprotection. We hope that comprehensive understanding of similarities and differences in IGF-2 signaling between model organisms and humans will be useful for development of more effective medicines targeting IGF-2 receptors.

GHRH-SST-GH-IGF axis regulates crosstalk between growth and immunity in rainbow trout (Oncorhynchus mykiss) infected with Vibrio anguillarum

An energy trade-off is existed between immunological competence and growth. The axis of growth hormone releasing hormone, somatostatin, growth hormone, insulin-like growth factor (GHRH-SST-GH-IGF axis) regulates growth performances and immune competences in rainbow trout (Oncorhynchus mykiss). The salmonid-specific whole genome duplication event is known to result in duplicated copies of several key genes in GHRH-SST-GH-IGF axis. In this study, we evaluated the physiological functions of GHRH-SST-GH-IGF axis in regulating crosstalk between growth and immunity. Based on principal components analysis (PCA), we observed the overall expression profiles of GHRH-SST-GH-IGF axis were significantly altered by Vibrio anguillarum infection. Trout challenged with Vibrio anguillarum showed down-regulated igf1s subtypes and up-regulated igfbp1a1. The brain sst genes (sst1a, sst1b, sst3b and sst5) and igfpbs genes (igfbp4s and igfbp5b2) were significantly affected by V. anguillarum infection, while the igfbp4s, igfbp5s, igfbp6s and igf2bps genes showed significant changes in peripheral immune tissues in response to V. anguillarum infection. Gene enrichment analyses showed functional and signaling pathways associated with apoptosis (such as p53, HIF-1 or FoxO signaling) were activated. We further proposed a possible model that describes the IGF and IGFBPs-regulated interaction between cell growth and programmed death. Our study provided new insights into the physiological functions and potentially regulatory mechanisms of the GHRH-SST-GH-IGF axis, indicating the pleiotropic effects of GHRH-SST-GH-IGF axis in regulating crosstalk between growth and immunity in trout.

Downregulation of IGF2 expression in third trimester placental tissues from Zika virus infected women in Brazil

OBJECTIVES

Screening for genes differentially expressed in placental tissues, aiming to identify transcriptional signatures that may be involved in ZIKV congenital pathogenesis.

METHODS

Transcriptome data from placental tissues of pregnant women naturally infected with Zika virus during the third trimester were compared to those from women who tested negative for Zika infection. The findings were validated using both a cell culture model and an immunohistochemistry/morphological analysis of naturally infected placental tissues.

RESULTS

Transcriptome analysis revealed that Zika virus infection induces downregulation of insulin-like growth factor II (IGF2) gene, an essential factor for fetal development. The Caco-2 cell culture model that constitutively expresses IGF2 was used for the transcriptome validation. Asiatic and African Zika virus strains infection caused downregulated IGF2 gene expression in Caco-2 cells, whereas other flaviviruses, such as dengue serotype 1, West Nile and wild-type yellow fever viruses, had no effect on this gene expression. Immunohistochemical assays on decidual tissues corroborated our transcriptome analysis, showing that IGF2 is reduced in the decidua of Zika virus-infected women.

CONCLUSIONS

Our results draw attention to IGF2 modulation in uterine tissues, and this finding is expected to support future studies on strategies to ameliorate the harmful effects of Zika virus infection during pregnancy.

Increased expression of insulin-like growth factor-1 receptor predicts poor prognosis in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a lethal disease worldwide. In this study, we sought to explore the expression of insulin-like growth factor-1 receptor (IGF-1R) and its prognostic value in HCC.The expressions of IGF-1R mRNA and protein were estimated using quantitative real-time polymerase chain reaction and immunohistochemistry assays, respectively. The association between IGF-1R expression and clinicopathologic characteristic of patients with HCC was analyzed through Chi-squared test. Kaplan-Meier analysis and multivariate Cox analysis were performed to analyze prognostic value of IGF-1R in HCC.The IGF-1R was significantly upregulated in HCC tissues at both mRNA and protein levels compared with adjacent normal ones (P < .01). Its expression was associated with tumor node metastasis stage (P = .037) and lymph node metastasis (P = .027) of patients with HCC. Patients with HCC with high expression of IGF-1R had worse overall survival than those with low expression. IGF-1R might be a potential prognostic biomarker for HCC (hazard ratio [HR] = 1.912, 95% confidence interval [CI]: 1.023-3.572, P = .042).The IGF-1R expression level is upregulated in HCC tissues and may act as a prognostic biomarker for the disease.

Ghrelin Promotes Proliferation and Inhibits Differentiation of 3T3-L1 and Human Primary Preadipocytes

Objective

Ghrelin is a 28-amino-acid peptide that regulates energy hemostasis, glucose and lipid metabolism. We aimed to explore the effects of ghrelin on the proliferation and differentiation of 3T3-L1 and human primary preadipocytes.

Methods

3-(4,5-Dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT) spectrophotometry, Oil Red O staining, intracellular glycerol-3-phosphate dehydrogenase (G-3-PDH) assays and semiquantitative reverse transcription polymerase chain reaction were used to investigate the action of ghrelin.

Results

Ghrelin (0.01–1000 ng/ml) significantly increased the numbers of 3T3-L1 cells, and the maximum stimulatory effect was observed with the 10 ng/ml ghrelin treatment for 24 h (p < 0.05). Ghrelin also promoted the proliferation of human primary preadipocytes from 24 h (p < 0.05) to 48 h (p < 0.05) at a concentration of 1000 ng/ml. Further investigation showed that IGF-1 levels were notably increased in ghrelin-treated 3T3-L1 and human preadipocytes, and IGF-1 antibody was capable to attenuate this stimulatory action of ghrelin (all p < 0.05). Additionally, ghrelin significantly suppressed the differentiation of 3T3-L1 and human primary preadipocytes; 10 ng/ml ghrelin notably downregulated G-3-PDH activities in 3T3-L1 cells on day 3 and in human cells from days 4 to 12 following differentiation (all p < 0.05), and the intracellular lipoprotein lipase mRNA levels were lower than that of the controls (p < 0.05). Further investigation showed that the mRNA levels of peroxisome proliferator-activated receptor γ2 (PPARγ2) and CCAAT/enhancer binding protein α (C/EBPs) were also suppressed in ghrelin-treated human differentiating adipocytes.

Conclusion

Ghrelin promotes the proliferation of 3T3-L1 and human primary preadipocytes by increasing the expression of IGF-1. Ghrelin inhibits murine and human adipocyte differentiation by downregulating PPARγ2 and C/EBPα levels, consequently leading to decreased lipid accumulation and lipogenic enzymes expression.

Insulin-like growth factor-1 attenuates oxidative stress-induced hepatocyte premature senescence in liver fibrogenesis via regulating nuclear p53-progerin interaction

Stress-induced premature senescence (SIPS), a state of cell growth arrest due to various stimuli, is implicated in the pathogeneses of hepatic fibrogenesis. Progerin, a permanently farnesylated mutant lamin A protein, likely leads to premature senescence to influent liver diseases. The previous reports showed that activation of insulin-like growth factor-1 (IGF-1) signaling could enhance cell longevity and attenuate liver fibrosis. However, the underlying mechanisms about hepatocyte premature senility in liver fibrosis, and how IGF-1 regulates cell premature aging and fibrogenesis, remain poorly understood. In the present study, we found the augment of hepatocyte oxidation and premature aging, along with the decrease of plasm IGF-1 level in patients with liver fibrosis and CCl₄-induced liver injury rat models. Nevertheless, IGF-1 gene transfer to CCl₄ rats to overexpress intrahepatic IGF-1 relieved hepatocyte oxidative stress and premature senescence, which was likely mediated by the p53/progerin pathway, to improve hepatic steatosis and fibrogenesis. In vitro, H₂O₂ caused abnormal accumulation of progerin in nuclear and activation of nuclear p53–progerin interaction to trigger primary rat hepatocyte premature senescence through the p21-independent pathway; while these effects were rescued by prolonged exogenous IGF-1 or the IGF-1 adenovirus vector. Furthermore, the IGF-1 adenovirus vector, transfected to H₂O₂-treated hepatocytes, reversed oxidative stress-induced premature senescence via enhancing cytoplasmic AKT1–p53 interaction and subsequently inhibiting nuclear p53–progerin interaction. Consequently, our data illuminate a novel role of IGF-1 in regulating stress-induced hepatocyte premature senescence in liver fibrosis: prolonged IGF-1 relieves oxidative stress-initiated hepatocyte premature senescence via inhibition of nuclear p53–progerin interaction to ameliorate hepatic steatosis and fibrogenesis.

Catalase and nonalcoholic fatty liver disease

Obesity and insulin resistance are considered the main causes of nonalcoholic fatty liver disease (NAFLD), and oxidative stress accelerates the progression of NAFLD. Free fatty acids, which are elevated in the liver by obesity or insulin resistance, lead to incomplete oxidation in the mitochondria, peroxisomes, and microsomes, leading to the production of reactive oxygen species (ROS). Among the ROS generated, H₂O₂ is mainly produced in peroxisomes and decomposed by catalase. However, when the H₂O₂ concentration increases because of decreased expression or activity of catalase, it migrates to cytosol and other organelles, causing cell injury and participating in the Fenton reaction, resulting in serious oxidative stress. To date, numerous studies have been shown to inhibit the pathogenesis of NAFLD, but treatment for this disease mainly depends on weight loss and exercise. Various molecules such as vitamin E, metformin, liraglutide, and resveratrol have been proposed as therapeutic agents, but further verification of the dose setting, clinical application, and side effects is needed. Reducing oxidative stress may be a fundamental method for improving not only the progression of NAFLD but also obesity and insulin resistance. However, the relationship between NAFLD progression and antioxidants, particularly catalase, which is most commonly expressed in the liver, remains unclear. Therefore, this review summarizes the role of catalase, focusing on its potential therapeutic effects in NAFLD progression.

Diabetes and hepatocellular carcinoma: A pathophysiological link and pharmacological management

Both diabetes mellitus (DM) and cancer are multifarious, dissimilar, and long-lasting, fatal diseases with a remarkable influence on health worldwide. DM is not only related to cardiovascular diseases, neuropathy, nephropathy, and retinopathy, but also related to a number of liver diseases such as nonalcoholic fatty liver disease, steatohepatitis, and liver cirrhosis. Recently, it is hypothesized that DM has a greater risk for many forms of cancer, such as breast, colorectal, endometrial, pancreatic, gallbladder, renal, and liver cancer including hepatocellular carcinoma (HCC). Both DM and cancer have many common risk factors, but the association between these two is poorly stated. Several epidemiologic studies have revealed the association between pathogenic and prognostic characteristics of DM and a higher incidence of HCC, thus representing DM as an independent risk factor for HCC development. The etiological and pathophysiological relationship between DM and HCC has been presented in this review by linking hyperglycemia, hyperinsulinemia, insulin resistance, and activation of insulin-like growth factor signaling pathways and pharmacological management of HCC associated with DM.

Insulin-Like Growth Factor (IGF) System in Liver Diseases

Hepatocyte differentiation, proliferation, and apoptosis are affected by growth factors produced in liver. Insulin-like growth factor 1 and 2 (IGF1 and IGF2) act in response to growth hormone (GH). Other IGF family components include at least six binding proteins (IGFBP1 to 6), manifested by both IGFs develop due to interaction through the type 1 receptor (IGF1R). The data based on animal models and/or in vitro studies suggest the role of IGF system components in cellular aspects of hepatocarcinogenesis (cell cycle progression, uncontrolled proliferation, cell survival, migration, inhibition of apoptosis, protein synthesis and cell growth), and show that systemic IGF1 administration can reduce fibrosis and ameliorate general liver function. In epidemiologic and clinicopathological studies on chronic liver disease (CLD), lowered serum levels, decreased tissue expression of IGF1, elevated production of IGF1R and variable IGF2 expression has been noted, from the start of preneoplastic alterations up to the developed hepatocellular carcinoma (HCC) stage. These changes result in well-known clinical symptoms of IGF1 deficiency. This review summarized the current data of the complex role of IGF system components in the most common CLD (nonalcoholic fatty liver disease, cirrhosis, and hepatocellular carcinoma). Better recognition and understanding of this system can contribute to discovery of new and improved versions of current preventive and therapeutic actions in CLD.

IGF-II induced by hepatitis B virus X protein regulates EMT via SUMO mediated loss of E-cadherin in mice

Hepatocellular carcinoma (HCC) is one of the most common cancers and a leading cause of cancer mortality. Prognosis of this disease largely depends on its stage. An Enlarged liver, due to dysplasia, may be a critical point in the multi-step progression to HCC. The mechanism underlying hepatomegaly in human and mouse models are poorly understood. We previously reported we observed enlarged liver in hepatitis B virus X protein (HBx) expressing mice (HBx mice). Here we identify the critical role of HBx induced IGF-II in hepatomegaly in mice and abnormal cell growth in human hepatoma cells. We found that HBx induced IGF-II is essential to induce epithelial-mesenchymal transition (EMT) through loss of E-cadherin. In mouse liver, loss of E-cadherin was mediated by post-translational regulation, at least in part, by protease and SUMOylation not by transcriptional regulation. In contrast, in hepatoma cell line (HepG2 cells) Akt signal pathway controls the mRNA expression level of EMT-related transcription factors, especially Twist, in addition to post- translational modification through SUMOylation. Thus, IGF-II-mediated loss of E-cadherin is central in developing hepatomegaly in mice and abnormal cell growth in the hepatoma cell line. HBx induced IGF-II represents a potential biomarker, which is also a therapeutic target in HCC.

Insulin Receptor Isoforms in Physiology and Disease: An Updated View

The insulin receptor (IR) gene undergoes differential splicing that generates two IR isoforms, IR-A and IR-B. The physiological roles of IR isoforms are incompletely understood and appear to be determined by their different binding affinities for insulin-like growth factors (IGFs), particularly for IGF-2. Predominant roles of IR-A in prenatal growth and development and of IR-B in metabolic regulation are well established. However, emerging evidence indicates that the differential expression of IR isoforms may also help explain the diversification of insulin and IGF signaling and actions in various organs and tissues by involving not only different ligand-binding affinities but also different membrane partitioning and trafficking and possibly different abilities to interact with a variety of molecular partners. Of note, dysregulation of the IR-A/IR-B ratio is associated with insulin resistance, aging, and increased proliferative activity of normal and neoplastic tissues and appears to sustain detrimental effects. This review discusses novel information that has generated remarkable progress in our understanding of the physiology of IR isoforms and their role in disease. We also focus on novel IR ligands and modulators that should now be considered as an important strategy for better and safer treatment of diabetes and cancer and possibly other IR-related diseases.

Quercetin Reverses Rat Liver Preneoplastic Lesions Induced by Chemical Carcinogenesis

Quercetin is a flavonoid widely studied as a chemopreventive agent in different types of cancer. Previously, we reported that quercetin has a chemopreventive effect on the liver-induced preneoplastic lesions in rats. Here, we evaluated if quercetin was able not only to prevent but also to reverse rat liver preneoplastic lesions. We used the modified resistant hepatocyte model (MRHM) to evaluate this possibility. Treatment with quercetin was used 15 days after the induction of preneoplastic lesions. We found that quercetin reverses the number of preneoplastic lesions and their areas. Our results showed that quercetin downregulates the expression of EGFR and modulates this signaling pathway in spite of the activated status of EGFR as detected by the upregulation of this receptor, with respect to that observed in control rats. Besides, quercetin affects the phosphorylation status of Src-1, STAT5, and Sp-1. The better status of the liver after the treatment with quercetin could also be confirmed by the recovery in the expression of IGF-1. In conclusion, we suggest that quercetin reversed preneoplastic lesions by EGFR modulation and the activation state of Src, STAT5, and Sp1, so as the basal IGF-1.

Pathophysiological aldosterone levels modify the secretory activity of cardiac progenitor cells

Cardiac progenitor cells (CPCs) trigger regenerative processes via paracrine mechanisms in response to changes in their environment. In the present study we explored alterations in the secretory activity of CPCs induced by raised aldosterone levels symptomatic for heart failure. The cytokine profile of the supernatant of CPCs that were treated with the mineralocorticoid showed an induction of interleukin-6 secretion. Mass spectrometric analyses revealed an increase in the abundance of secreted proteins associated with regeneration and cell migration like gelsolin and galectin-1. Differential regulation of proteins associated with the extracellular matrix further points to an activation of cell migration. In response to supernatant, migration and proliferation were induced in CPCs, indicating a potential role of paracrine factors in the activation of CPCs from other regions of the heart or extra-cardiac sources. Changes in the secretory activity of CPCs might aim to compensate for the detrimental actions of aldosterone in heart failure.

Insulin-like growth factor (IGF) axis in cancerogenesis

Determination of the role of insulin-like growth factor (IGF) family components in carcinogenesis of several human tumors is based on numerous epidemiological and pre-clinical studies, experiments in vivo and in vitro and on attempts at application of drugs affecting the IGF axis. Investigative hypotheses in original studies were based on biological functions manifested by the entire family of IGF (ligands, receptors, linking proteins, adaptor molecules). In the context of carcinogenesis the most important functions of IGF family involve intensification of proliferation and inhibition of cell apoptosis and effect on cell transformation through synthesis of several regulatory proteins. IGF axis controls survival and influences on metastases of cells. Interactions of IGF axis components may be of a direct or indirect nature. The direct effects are linked to activation of PI3K/Akt signaling pathway, in which the initiating role is first of all played by IGF-1 and IGF-1R. Activity of this signaling pathway leads to an increased mitogenesis, cell cycle progression, and protection against different apoptotic stresses. Indirect effects of the axis depend on interactions between IGF and other molecules important for cancer etiology (e.g. sex hormones, products of suppressor genes, viruses, and other GFs) and the style of life (nutrition, physical activity). From the clinical point of view, components of IGF system are first of all considered as diagnostic serous and/or tissue biomarkers of a given cancer, prognostic factors and attractive target of modern anti-tumor therapies. Several mechanisms in which IGF system components act in the process of carcinogenesis need to be clarified, mainly due to multifactorial etiology of the neoplasms. Pin-pointing of the role played in carcinogenesis by any single signaling pathway remains particularly difficult. The aim of this review is to summarize the current data of several epidemiological studies, experiments in vitro and on animal models, to increase our understanding of the complex role of IGF family components in the most common human cancers.

Insulin-like growth factor-1 mRNA isoforms and insulin-like growth factor-1 receptor mRNA expression in chronic hepatitis C

AIM: To evaluate the expression of different insulin-like growth factor (IGF)-1 mRNA isoforms and IGF-1 receptor (IGF-1R) mRNA in hepatitis C virus (HCV)-infected livers.

METHODS: Thirty-four liver biopsy specimens from chronic hepatitis C (CH-C) patients were obtained before anti-viral therapy. Inflammatory activity (grading) and advancement of fibrosis (staging) were evaluated using a modified point scale of METAVIR. The samples were analyzed using quantitative real-time PCR technique. From fragments of liver biopsies and control liver that were divided and ground in liquid nitrogen, RNA was isolated using RNeasy Fibrous Tissue Mini Kit according to the manufacturer’s instruction. Expression levels of IGF-1 mRNA isoforms (IGF-1A, IGF-1B, IGF-1C, P1, and P2) and IGF-1R mRNA were determined through normalization of copy numbers in samples as related to reference genes: glyceraldehyde-3-phosphate dehydrogenase and hydroxymethylbilane synthase. Results on liver expression of the IGF-1 mRNA isoforms and IGF-1R transcript were compared to histological alterations in liver biopsies and with selected clinical data in the patients. Statistical analysis was performed using Statistica PL v. 9 software.

RESULTS: The study showed differences in quantitative expression of IGF-1 mRNA variants in HCV-infected livers, as compared to the control. Higher relative expression of total IGF-1 mRNA and of IGF-1 mRNAs isoforms (P1, A, and C) in HCV-infected livers as compared to the control were detected. Within both groups, expression of the IGF-1A mRNA isoform significantly prevailed over expressions of B and C isoforms. Expression of P1 mRNA was higher than that of P2 only in CH-C. Very high positive correlations were detected between reciprocal expressions of IGF-1 mRNA isoforms P1 and P2 (r = 0.876). Expression of P1 and P2 mRNA correlated with IGF-1A mRNA (r = 0.891; r = 0.821, respectively), with IGF-1B mRNA (r = 0.854; r = 0.813, respectively), and with IGF-1C mRNA (r = 0.839; r = 0.741, respectively). Expression of IGF-1A mRNA significantly correlated with isoform B and C mRNA (r = 0.956; r = 0.869, respectively), and B with C isoforms (r = 0.868) (P < 0.05 in all cases). Lower expression of IGF-1A and B transcripts was noted in the more advanced liver grading (G2) as compared to G1. Multiple negative correlations were detected between expression of various IGF-1 transcripts and clinical data (e.g., alpha fetoprotein, HCV RNA, steatosis, grading, and staging). Expression of IGF-1R mRNA manifested positive correlation with grading and HCV-RNA.

CONCLUSION: Differences in quantitative expression of IGF-1 mRNA isoforms in HCV-infected livers, as compared to the control, suggest that HCV may induce alteration of IGF-1 splicing profile.

Targeting the insulin-like growth factor pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. Only 30%-40% of the patients with HCC are eligible for curative treatments, which include surgical resection as the first option, liver transplantation and percutaneous ablation. Unfortunately, there is a high frequency of tumor recurrence after surgical resection and most HCC seem resistant to conventional chemotherapy and radiotherapy. Sorafenib, a multi-tyrosine kinase inhibitor, is the only chemotherapeutic option for patients with advanced hepatocellular carcinoma. Patients treated with Sorafenib have a significant increase in overall survival of about three months. Therefore, there is an urgent need to develop alternative treatments. Due to its role in cell growth and development, the insulin-like growth factor system is commonly deregulated in many cancers. Indeed, the insulin-like growth factor (IGF) axis has recently emerged as a potential target for hepatocellular carcinoma treatment. To this aim, several inhibitors of the pathway have been developed such as monoclonal antibodies, small molecules, antisense oligonucleotides or small interfering RNAs. However recent studies suggest that, unlike most tumors, HCC development requires increased signaling through insulin growth factor II rather than insulin growth factor I. This may have great implications in the future treatment of HCC. This review summarizes the role of the IGF axis in liver carcinogenesis and the current status of the strategies designed to target the IGF-I signaling pathway for hepatocellular carcinoma treatment.

IGF axis and other factors in HPV-related and HPV-unrelated carcinogenesis (review)

The insulin-like growth factor (IGF) axis promotes the growth of cells, tissues and organs. IGF-1 is mainly produced in the liver but is also secreted from local tissues. In the circulation, IGF-1 is bound to insulin-like binding proteins (IGFBPs), and when released it activates the insulin-like growth factor receptor (IGF-1R). The signal is further transmitted by intracellular signaling pathways leading to gene expression that regulates, among others, cell proliferation and survival. This review presents the IGF axis in the context of cell transformation and cancer development. Aspects involving IGF-1 deficiency and protection from cancer are also briefly described. Furthermore, human papillomaviruses (HPVs) interplaying with IGF axis components in cervical cancer development are described. These small dsDNA viruses are divided into low-risk and high-risk HPVs with regard to the potency of their oncogenic actions; they mainly infect epithelial or mucosal cells. Special attention is drawn to expression of two major HPV oncogenes (E6 and E7) initiating and maintaining cervical carcinogenesis, which is a multistep and multifactorial process; therefore, involvement of additional factors such as mitochondrial DNA changes, sex hormones, retinoic and folic acids are also discussed. Finally, IGF axis components and HPV oncogenes as targets in anticancer treatment are presented which include IGF-1R downregulation, RNA interference and anti-HPV therapeutic vaccines. The review concludes that despite an enormous advancement in research on IGF and HPV-related cancers, more molecular studies and clinical trials are needed before commercialized therapies are widely available for oncology patients.

Insulin-like growth factor-1 prevents miR-122 production in neighbouring cells to curtail its intercellular transfer to ensure proliferation of human hepatoma cells

miRNAs are 20-22 nt long post-transcriptional regulators in metazoan cells that repress protein expression from their target mRNAs. These tiny regulatory RNAs follow tissue and cell-type specific expression pattern, aberrations of which are associated with various diseases. miR-122 is a liver-specific anti-proliferative miRNA that, we found, can be transferred via exosomes between human hepatoma cells, Huh7 and HepG2, grown in co-culture. Exosomal miR-122, expressed and released by Huh7 cells and taken by miR-122 deficient HepG2 cells, was found to be effective in repression of target mRNAs and to reduce growth and proliferation of recipient HepG2 cells. Interestingly, in a reciprocal process, HepG2 secretes Insulin-like Growth Factor 1 (IGF1) that decreases miR-122 expression in Huh7 cells. Our observations suggest existence of a reciprocal interaction between two different hepatic cells with distinct miR-122 expression profiles. This interaction is mediated via intercellular exosome-mediated miR-122 transfer and countered by a reciprocal IGF1-dependent anti-miR-122 signal. According to our data, human hepatoma cells use IGF1 to prevent intercellular exosomal transfer of miR-122 to ensure its own proliferation by preventing expression of growth retarding miR-122 in neighbouring cells.

Emerging role of insulin-like growth factor-binding protein 7 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a vicious and highly vascular cancer with a dismal prognosis. It is a life-threatening illness worldwide that ranks fifth in terms of cancer prevalence and third in cancer deaths. Most patients are diagnosed at an advanced stage by which time conventional therapies are no longer effective. Targeted molecular therapies, such as the multikinase inhibitor sorafenib, provide a modest increase in survival for advanced HCC patients and display significant toxicity. Thus, there is an immense need to identify novel regulators of HCC that might be targeted effectively. The insulin-like growth factor (IGF) axis is commonly abnormal in HCC. Upon activation, the IGF axis controls metabolism, tissue homeostasis, and survival. Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted protein of a family of low-affinity IGF-binding proteins termed “IGFBP-related proteins” that have been identified as a potential tumor suppressor in HCC. IGFBP7 has been implicated in regulating cellular proliferation, senescence, and angiogenesis. In this review, we provide a comprehensive discussion of the role of IGFBP7 in HCC and the potential use of IGFBP7 as a novel biomarker for drug resistance and as an effective therapeutic strategy.

Non-B, non-C hepatocellular carcinoma (Review)

Although most hepatocellular carcinoma (HCC) is related to viral infection, there is a substantial population of HCC patients (5-20%) who are negative for both markers of hepatitis B virus and hepatitis C virus infection [non-B, non-C (NBNC) hepatitis] in Japan and the incidence of NBNC-HCC has recently tended to increase. The most common cause of liver disease in developed countries is non‑alcoholic fatty liver disease (NAFLD), which includes non‑alcoholic steatohepatitis (NASH) and its related complications. Increased body mass index and diabetes mellitus are associated with developing NAFLD and NASH, which is a severe form of NAFLD. Furthermore, increasing clinical evidence supports the fact that NAFLD and NASH can progress to liver cirrhosis and even HCC. A detailed understanding of the epidemiology, etiology, molecular mechanism, clinical features and prognosis of NBNC-HCC could improve our screening and therapy of this disease. In this review, we primarily focus on clinical aspects of NBNC-HCC and refer to our current knowledge of this cancer.

The role of insulin-like growth factor 1 and its receptor in the formation and development of colorectal carcinoma

OBJECTIVE

To investigate the role of insulin-like growth factor (IGF)-1 and its receptor (IGF1R) in the formation and development of colorectal carcinoma.

METHODS

Colorectal tissue and matching serum samples were collected from patients with adenomatous polyps or carcinoma and healthy control subjects. IGF1R mRNA levels were determined via quantitative real-time reverse transcription-polymerase chain reaction. Serum IGF1 was quantified using enzyme-linked immunosorbent assay.

RESULTS

Serum IGF1 concentrations and mucosal IGF1R mRNA levels were significantly higher in patients with adenomatous polyps (n = 24) or carcinoma (n = 13) compared with healthy control subjects (n = 13). There was a significant positive correlation between serum IGF1 and mucosal IGF1R mRNA in patients with adenomatous polyps.

CONCLUSIONS

High circulating IGF1 concentrations and mucosal IGF1R expression may play important roles in both the formation and development of colorectal carcinoma. IGF1 and its receptor may be activated before carcinogenesis, and may promote the growth and malignant transformation of adenomatous polyps. IGF1 and IGF1R may be useful biomarkers for evaluating the stage and risk of carcinogenesis.

The insulin-like growth factor-1 and expression of its binding protein‑3 in chronic hepatitis C and hepatocellular carcinoma

The role of growth factors produced by the liver, including insulin-like growth factor-1 (IGF-1) and its main binding protein, IGF binding protein-3 (IGFBP-3), in hepatitis C virus (HCV)-associated carcinogenesis has only partially been recognized and there is not much data available on the local expression of IGF-1 and IGFBP-3 in chronic hepatitis C (CH‑C). Therefore, the aim of the present study was to evaluate the IGF‑1 and IGFBP‑3 serum levels and tissue expression in liver biopsies of CH‑C patients (n=37) and hepatocellular carcinoma (HCC) samples (n=61) as related to age- and gender-matched control serum samples (n=15) and healthy liver samples (n=10). Serum concentrations of IGF-1 (S-IGF-1) and IGFBP‑3 (S-IGFBP‑3) were measured by the ELISA method. Tissue expression of proteins was detected using ABC immunocytochemistry and evaluated applying a spatial visualization technique. Concentrations of S-IGF-1 and hepatic expression of IGF-1 (H-IGF-1) proved to be lower in CH-C compared to the controls. No significant differences were detected in the concentration of S-IGFBP-3 between the studied groups but the S-IGF-1/IGFBP-3 ratio in the CH-C group was significantly lower compared to the control. H-IGFBP-3 was higher in CH-C compared to those in the control and HCC. In HCC, lower expression of H-IGF-1 was detected compared to the control and a higher H-IGF-1/IGFBP-3 ratio compared to CH-C. A negative correlation was detected between S-IGF-1 and S-IGF-1/IGFBP-3 ratio, on the one hand, and age, grading and concentration of α-fetoprotein (AFP) on the other, while H-IGFBP-3 was negatively correlated with BMI in the CH‑C group. In patients with CH‑C, the H‑IGF‑1/IGFBP‑3 ratio was higher compared to that of the S‑IGF‑1/IGFBP‑3 ratio. The studies documented a disturbed H‑IGF‑1 and H‑IGFBP‑3 in CH‑C, which may be of significance in carcinogenesis. Examination of serum concentration and tissue expression of the two proteins and, first of all, estimation of the IGF‑1/IGFBP‑3 ratio may provide additional (to the estimation of IGF‑1 and AFP) non-invasive markers in HCV‑related liver injury.