Characterization of insulin-like-growth factor II (IGF II) mRNA positive hepatic altered foci and IGF II expression in hepatocellular carcinoma during diethylnitrosamine-induced hepatocarcinogenesis in rats

H-ras-targeted genetic therapy remarkably surpassed docetaxel treatment in inhibiting chemically induced hepatic tumors in rats

AIMS

Hepatocellular carcinoma (HCC) is still a leading cause of cancer-related death worldwide. But its chemotherapeutic options are far from expectation. We here compared H-ras targeted genetic therapy to a commercial docetaxel formulation (DXT) in inhibiting HCC in rats.

MAIN METHODS

After the physicochemical characterization of phosphorothioate-antisense oligomer (PS-ASO) against H-ras mutated gene, the PS-ASO-mediated in vitro hemolysis, in vivo hepatic uptake, its pharmacokinetic profile, tissue distribution in some highly perfused organs, its effect in normal rats, antineoplastic efficacy in carcinogen-induced HCC in rats were evaluated and compared against DXT treatment. Mutated H-ras expression by in situ hybridization, hep-par-I, CK-7, CD-15, p53 expression patterns by immunohistochemical methods, scanning electron microscopic evaluation of hepatic architecture, various hepatic marker enzyme levels and caspase-3/9 apoptotic enzyme activities were also carried out in the experimental rats.

KEY FINDINGS

PS-ASO showed low in vitro hemolysis (<3 %), and had a sustained PS-ASO blood residence time in vivo compared to DTX, with a time-dependent hepatic uptake. It showed no toxic manifestations in normal rats. PS-ASO distribution was although initially less in the lung than liver and kidney, but at 8 h it accumulated more in lung than kidney. Antineoplastic potential of PS-ASO (treated for 6 weeks) excelled in inhibiting chemically induced tumorigenesis compared to DTX in rats, by inhibiting H-ras gene expression, some immonohistochemical modulations, and inducing caspase-3/9-mediated apoptosis. It prevented HCC-mediated lung metastatic tumor in the experimental rats.

SIGNIFICANCE

PS-ASO genetic therapy showed potential to inhibit HCC far more effectively than DXT in rats.

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.

Recurrent Non-islet Cell Tumor Hypoglycemia Secondary to Hepatocellular Carcinoma: Case Report and Literature Review

RATIONALE

Non-islet cell tumor hypoglycemia (NICTH) is a paraneoplastic syndrome caused by tumors other than insulinoma that is primarily due to excessive production of insulin-like growth factor-II (IGF-II). The prevalence of NICTH is likely underestimated because of a lack of clinical recognition.

PATIENT CONCERNS

A 41-year-old male with massive malignant liver tumors presented with recurrent severe hypoglycemia, weight loss, and liver cirrhosis.

DIAGNOSIS

NICTH related to IGF-II produced by hepatocellular carcinoma was diagnosed based on clinical symptoms, biochemical tests, and elevated IGF-II/IGF-I ratio.

INTERVENTION

Initial treatment with intravenous glucose and parenteral nutrition showed limited efficacy. Glucocorticoids and recombinant human growth hormone led to progressive improvement in blood glucose levels.

OUTCOME

Due to extensive tumor burden and liver failure, surgical resection was not feasible, and the patient ultimately succumbed to refractory hypoglycemia and passed away in two weeks.

LESSONS

Early recognition and diagnosis of NICTH are crucial in patients with recurrent hypoglycemia and large tumors. Surgical resection is the preferred treatment option, but supportive care and pharmacological interventions, such as glucocorticoids and growth hormone, can help manage refractory hypoglycemia. Further research is needed to explore novel treatment options, including anti-IGF-I and -IGF-II neutralizing antibodies.

A Comparative Investigation of the Ability of Various Aptamer-Functionalized Drug Nanocarriers to Induce Selective Apoptosis in Neoplastic Hepatocytes: In Vitro and In Vivo Outcome

Aptamers offer a significant promise to target various cancers including hepatocellular carcinoma (HCC), for their high affinity and ability to reach the target site(s), non-immunogenicity, and low cost. The targeting ability to neoplastic hepatocytes by the aptamer, TLS 9a with phosphorothioate backbone modification (designated as L5), has not been explored yet. Hence, we investigated the comparative potential of L5 with some other previously reported liver cancer cell-specific aptamers, conjugated on the surface of drug-nanocarriers. Various in vitro studies such as cytotoxicity, in vitro cellular uptake, cell cycle analysis, and investigations related to apoptosis were performed. In vivo studies carried out here include macroscopic and microscopic hepatic alterations in chemically induced hepatocarcinogenesis in rats, upon experimental treatments. The outcome of the investigations revealed that L5-functionalized drug-nanocarrier (PTX-NPL5) had the highest apoptotic potential compared with the other aptamer-conjugated experimental formulations. Further, its maximum internalization by neoplastic hepatocytes and minimum internalization by normal hepatocytes indicate that it had the potential to preferentially target the neoplastic hepatocytes. Data of in vivo studies revealed that PTX-NPL5 reduced tumor incidences and tumor progress. Superior potency of PTX-NPL5 may be due to the maximum affinity of L5 towards neoplastic hepatocytes resulting in maximum permeation of drug-nanocarrier in them. An effective site-specific targeting of neoplastic hepatocytes can be achieved by L5 for preferential delivery of therapeutics. Further, investigations are needed to identify the target protein(s) on neoplastic hepatocytes responsible for ligand-receptor interaction of L5.

Aptamer-Functionalized Drug Nanocarrier Improves Hepatocellular Carcinoma toward Normal by Targeting Neoplastic Hepatocytes

Site-specific delivery of chemotherapeutics specifically to neoplastic hepatocytes without affecting normal hepatocytes should be a focus for potential therapeutic management of hepatocellular carcinoma (HCC). The aptamer TLS 9a with phosphorothioate backbone modifications (L5) has not been explored so far for preferential delivery of therapeutics in neoplastic hepatocytes to induce apoptosis. Thus, the objective of the present investigation was to compare the therapeutic potential of L5-functionalized drug nanocarrier (PTX-NPL5) with those of the other experimental drug nanocarriers functionalized by previously reported HCC cell-targeting aptamers and non-aptamer ligands, such as galactosamine and apotransferrin. A myriad of well-defined investigations such as cell cycle analysis, TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling) assay, and studies related to apoptosis, histopathology, and immunoblotting substantiated that PTX-NPL5 had the highest potency among the different ligand-attached experimental formulations in inducing selective apoptosis in neoplastic hepatocytes via a mitochondrial-dependent apoptotic pathway. PTX-NPL5 did not produce any notable toxic effects in healthy hepatocytes, thus unveiling a new and a safer option in targeted therapy for HCC. Molecular modeling study identified two cell-surface biomarker proteins (tumor-associated glycoprotein 72 [TAG-72] and heat shock protein 70 [HSP70]) responsible for ligand-receptor interaction of L5 and preferential internalization of PTX-NPL5 via clathrin-mediated endocytosis in neoplastic hepatocytes. The potential of PTX-NPL5 has provided enough impetus for its rapid translation from the pre-clinical to clinical domain to establish itself as a targeted therapeutic to significantly prolong survival in HCC.

Splenic serum from portal hypertensive patients enhances liver stem cell proliferation and self-renewal via the IGF-II/ERK signaling pathway

BACKGROUND

Hypersplenism is a serious complication of portal hypertension (PH) and can affect the prognosis of liver disease. Liver stem cells (LSCs) are involved in liver regeneration and hepatocarcinogenesis after liver cirrhosis.

AIM

To explore the effects and mechanism of the spleen on the proliferation and differentiation of LSCs in PH due to liver cirrhosis.

METHODS

Fetal liver stem cells (FLSCs) were treated with splenic serum from liver cirrhosis patients with hypersplenism and control serum from healthy volunteers, and the proliferation, self-renewal, and IGF-II/ERK signaling pathway of FLSCs were then evaluated.

RESULTS

We found that splenic serum from PH patients promoted FLSC proliferation, colony formation, and Ki-67 expression in vitro. Splenic serum from PH also enhanced FLSC spheroid formation in vitro. Mechanistically, we determined that insulin-like growth factor (IGF)-II concentration was elevated in splenic serum from PH patients and could promote FLSC proliferation and self-renewal. Furthermore, both IGF-II and splenic serum from PH patients enhanced ERK signaling activation through IGF-I receptor (IGF-I R) in FLSCs. Consistently, blocking IGF-I R or ERK signaling could attenuate the effects of splenic serum from PH patients on FLSCs.

CONCLUSIONS

The spleen in PH patients promotes FLSC proliferation and self-renewal through the IGF-II/ERK signaling pathway.

Alteration of oncogenic IGF-II gene methylation status associates with hepatocyte malignant transformation

BACKGROUND

Oncogenic insulin-like growth factor-II (IGF-II) is overexpressed in hepatocellular carcinoma (HCC). The present study aimed to analyze the dynamic alteration of IGF-II CpG site methylation status and its molecular mechanism in HCC progression.

METHODS

IGF-II alterations were observed in rat hepatocarcinogenesis models induced by 2-acetylaminofluorene. Liver IGF-II expression was compared by immunohistochemistry or tissue IGF-II specific concentration (nmol/mg protein). Status of human IGF-II promoter 3 (P3) or rat IGF-II P2 CpG site methylation was amplified by methylation-specific polymerase chain reaction (MSP). Serum IGF-II levels were quantitatively detected by an enzyme-linked immunosorbent assay.

RESULTS

The levels of hepatic IGF-II expression were significantly elevated in the HCC group (P < 0.001). The unmethylation rate of IGF-II P3 CpG sites was 100% in the HCC-, 52.5% in the paracancerous-, and none (0%) in the distal noncancerous-tissues. Abnormal IGF-II expression was related to differentiation degree, tumor invasion, and positive HBV-DNA (all P < 0.001), with a negative correlation between P3 methylation degree and IGF-II expression. There was a positive correlation between liver IGF-II specific concentration and circulating IGF-II level (r = 0.97, P < 0.001). Significantly negative correlation was found between IGF-II P2 CpG site methylation and circulating IGF-II (r_s = -0.89, P < 0.001) or liver IGF-II level (r_s = -0.84, P < 0.001).

CONCLUSIONS

The increase of serum IGF-II and the alteration of oncogenic gene IGF-II methylation may be biomarkers for HCC diagnosis and DNA methylation may be the therapeutic target of HCC.

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.

Clear cell hepatocellular carcinoma: origin, metabolic traits and fate of glycogenotic clear and ground glass cells

Clear cell hepatocellular carcinoma (CCHCC) has hitherto been considered an uncommon, highly differentiated variant of hepatocellular carcinoma (HCC) with a relatively favorable prognosis. CCHCC is composed of mixtures of clear and/or acidophilic ground glass hepatocytes with excessive glycogen and/or fat and shares histology, clinical features and etiology with common HCCs. Studies in animal models of chemical, hormonal and viral hepatocarcinogenesis and observations in patients with chronic liver diseases prone to develop HCC have shown that the majority of HCCs are preceded by, or associated with, focal or diffuse excessive storage of glycogen (glycogenosis) which later may be replaced by fat (lipidosis/steatosis). In ground glass cells, the glycogenosis is accompanied by proliferation of the smooth endoplasmic reticulum, which is closely related to glycogen particles and frequently harbors the hepatitis B surface antigen (HBsAg). From the findings in animal models a sequence of changes has been established, commencing with preneoplastic glycogenotic liver lesions, often containing ground glass cells, and progressing to glycogen-poor neoplasms via various intermediate stages, including glycogenotic/lipidotic clear cell foci, clear cell hepatocellular adenomas (CCHCA) rich in glycogen and/or fat, and CCHCC. A similar process seems to take place in humans, with clear cells frequently persisting in CCHCC and steatohepatitic HCC, which presumably represent intermediate stages in the development rather than particular variants of HCC. During the progression of the preneoplastic lesions, the clear and ground glass cells transform into cells characteristic of common HCC. The sequential cellular changes are associated with metabolic aberrations, which start with an activation of the insulin signaling cascade resulting in pre-neoplastic hepatic glycogenosis. The molecular and metabolic changes underlying the glycogenosis/lipidosis are apparently responsible for the dramatic metabolic shift from gluconeogenesis to the pentose phosphate pathway and Warburg-type glycolysis, which provide precursors and energy for an ever increasing cell proliferation during progression.

Study of the effects of cyclooxygenase-2 inhibitor on the promotion of hepatic tumorigenesis in rats fed a high fat diet

BACKGROUND/OBJECTIVE

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. The highest prevalence of hepatitis is an important risk factor contributing to development of HCCs. However, an increasing number of cases are associated metabolic disease and steatohepatitis. Inflammation associated with many liver disease, seems to be a necessary pre-requisite for successful tumor initiation. Mechanisms that link high fat diet and inflammation initial stage of HCC are not completely understood. The present work was designed to investigate the effect of fat, through modulation of the insulin-like growth factors I and II (IGF-I and IGF-II), on the promotion of hepatocellular carcinoma, and the role of cyclooxygenase 2 (COX-2).

METHODS

two main groups of rats were used: control and HCC groups. The HCC group was further sub-divide in to two subgroups, HCC fed with standard diet and HCC fed with high fat diet. The effects of celecoxib were also investigated in HCC fed with high fat diet.

RESULTS

We found that high fat diet was associated with significant increases in COX2 and interleukin 6 (IL6) with significant promotion of HCC progression. The significant increase in IGF could contribute partially to the observed effects of high fat diet. In addition, celecoxib was found to significantly reduce HCC progression.

CONCLUSIONS

We conclude that COX2 could play central role in high prevalence of HCC observed with high fat diet. Several triggering factors such as IGF and IL6, together with the direct modulation of fat metabolism could open several novel preventive strategies of celecoxib treatment, and could be useful biomarkers for assessment of its pharmacological effects.

Antisense oligonucleotides directed against insulin-like growth factor-II messenger ribonucleic acids delay the progress of rat hepatocarcinogenesis

Background:

Hepatocellular carcinoma (HCC) is a multistep complex process, caused by many of genetic alteration. Insulin-like growth factors and their receptor have been widely implicated to HCC. Insulin-like growth factor-II (IGF-II) is a mitogenic polypeptide, found in various fetal and neonatal tissues of humans and rats and expresses in HCC. Here we investigated anticancer potential of phosphorothioate antisense oligonucleotides (ASOs) against three coding exons (exon-1/exon-2/exon-3) of IGF-II messenger ribonucleic acid in rat hepatocarcinogenesis model.

Materials and Methods:

During diethylnitrosamine and 2-acetylaminofluorene induced hepatocarcinogenesis, rats were treated with ASOs. Various biochemical and histological studies were conducted.

Results:

About 40% of carcinogen treated rats, which received two oligomers (against exon-1 or-3) did not show any hepatic lesion, hyperplastic nodule or tumor and remaining 60% of those rats showed lesion incidence and had about 59% and 55% reductions in the numbers of hepatic altered foci, respectively. Reductions in the total lesion-area when compared with carcinogen control rats were 64% and 53%, respectively for the animals treated with carcinogen and received the ASOs against exon-1/-3. Fluorescein isothiocyanate-labeled ASO reached in the hepatocytes in 2 h. No predominant IGF-II overexpression was observed in case of rats treated with the two ASOs. Treatment of the antisense IGF-II oligomers in carcinogen treated rats show better hepatocellular integrity along with several preneoplastic/neoplastic marker isoenzyme/enzyme modulations.

Conclusions:

Two of the three antisense oligomer-types effectively controlled IGF-II overexpression, causing the delay of the development and/or progress of hepatic cancer in rats.

Protein phosphatase 2A promotes hepatocellular carcinogenesis in the diethylnitrosamine mouse model through inhibition of p53

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Most HCCs develop in cirrhotic livers. Alcoholic liver disease, chronic hepatitis B and chronic hepatitis C are the most common underlying liver diseases. Hepatitis C virus (HCV)-specific mechanisms that contribute to HCC are presently unknown. Transgenic expression of HCV proteins in the mouse liver induces an overexpression of the protein phosphatase 2A catalytic subunit (PP2Ac). We have previously reported that HCV-induced PP2Ac overexpression modulates histone methylation and acetylation and inhibits DNA damage repair. In this study, we analyze tumor formation and gene expression using HCV transgenic mice that overexpress PP2Ac and liver tissues from patients with HCC. We demonstrate that PP2Ac overexpression interferes with p53-induced apoptosis. Injection of the carcinogen, diethylnitrosamine, induced significantly more and larger liver tumors in HCV transgenic mice that overexpress PP2Ac compared with control mice. In human liver biopsies from patients with HCC, PP2Ac expression was significantly higher in HCC tissue compared with non-tumorous liver tissue from the same patients. Our findings demonstrate an important role of PP2Ac overexpression in liver carcinogenesis and provide insights into the molecular pathogenesis of HCV-induced HCC.

Targeting insulin-like growth factor axis in hepatocellular carcinoma

The insulin-like growth factor (IGF) axis contains ligands, receptors, substrates, and ligand binding proteins. The essential role of IGF axis in hepatocellular carcinoma (HCC) has been illustrated in HCC cell lines and in animal xenograft models. Preclinical evidence provides ample indication that all four components of IGF axis are crucial in the carcinogenic and metastatic potential of HCC. Several strategies targeting this system including monoclonal antibodies against the IGF 1 receptor (IGF-1R) and small molecule inhibitors of the tyrosine kinase function of IGF-1R are under active investigation. This review describes the most up-to-date understanding of this complex axis in HCC, and provides relevant information on clinical trials targeting the IGF axis in HCC with a focus on anti-IGF-1R approach. IGF axis is increasingly recognized as one of the most relevant pathways in HCC and agents targeting this axis can potentially play an important role in the treatment of HCC.

Targeting insulin-like growth factor axis in hepatocellular carcinoma

The insulin-like growth factor (IGF) axis contains ligands, receptors, substrates, and ligand binding proteins. The essential role of IGF axis in hepatocellular carcinoma (HCC) has been illustrated in HCC cell lines and in animal xenograft models. Preclinical evidence provides ample indication that all four components of IGF axis are crucial in the carcinogenic and metastatic potential of HCC. Several strategies targeting this system including monoclonal antibodies against the IGF 1 receptor (IGF-1R) and small molecule inhibitors of the tyrosine kinase function of IGF-1R are under active investigation. This review describes the most up-to-date understanding of this complex axis in HCC, and provides relevant information on clinical trials targeting the IGF axis in HCC with a focus on anti-IGF-1R approach. IGF axis is increasingly recognized as one of the most relevant pathways in HCC and agents targeting this axis can potentially play an important role in the treatment of HCC.

Effect of antisense oligomer in controlling c-raf.1 overexpression during diethylnitrosamine-induced hepatocarcinogenesis in rat

PURPOSE

In ras-mediated signal transduction pathway, c-raf.1 is believed to have predominant oncogenic potential and has been found to be highly expressed in certain human and animal malignancies including hepatocellular carcinoma. In the present study, anticancer efficacy of antisense c-raf.1 oligomer on the inhibition of c-raf.1 mRNA overexpression during hepatocarcinogenesis was determined.

METHODS

Initially antiproliferating effect of the antisense oligomers was studied in vitro by measuring the rate of tritiated thymidine incorporation into DNA in rat hepatocellular carcinoma cells in culture medium. Based on the findings, the antisense treatment was carried out in rat hepatocarcinogenesis model-initiated with diethylnitrosamine and promoted using 2-acetylaminoflourene. Different drug-metabolizing enzymes, lipid peroxidation, liver morphology and histopathological studies along with c-raf.1 gene expression by in situ hybridization were performed.

RESULTS

c-raf.1 antisense oligomers exhibited an inhibitory effect (approximately 68%) on cancer cell proliferation in vitro. Gross and microscopic examination of liver showed fewer (29%) and smaller hyperplastic nodules and preneoplastic lesions (30%) in carcinogen and antisense oligomer-treated group as compared with carcinogen control group. Treatment of antisense c-raf.1 oligomers enhanced cytochrome P-450 content (81%) and reduced glutathione S-transferase activity (33%), UDP glucuronosyltransferase activity (74%) and MDA concentration (30%) in carcinogen and antisense oligomer-treated group as compared with carcinogen control animals. The oligomer treatment also resulted in less expression in terms of c-raf.1 expressed lesion count as compared to carcinogen control group.

CONCLUSION

The study demonstrates that the antisense oligomer targeted against c-raf.1 mRNA inhibits the overexpression of c-raf.1 gene during hepatocellular carcinoma in rats.

Hepatocellular Carcinoma: Tumorigenesis and Prediction Markers

Hepatocellular carcinoma (HCC) is one of the most common malignancies. Although many advances have been made in the clinical study of HCC, the prognosis remains poor. Despite the discoveries in cancer biology in respect with physiological and pathological factors in relation to prognosis, HCC remains still a fatal disease due to late diagnosis. For improving the outcomes of patients with HCC, it is important to identify the factors predisposing to patient death. In recent years, based on cellular and molecular biology techniques, many tumor markers related to invasion, metastasis, recurrence and survival have been explored. However, routine biomarkers for the prediction of HCC evolution and prognosis are available in small number and less specific. These reviews focus on the recent advances in HCC tumorigenesis, revealing those biomarkers with prognosis significance or can be used for early detection.

Changes in the antioxidant defense and hepatic drug metabolizing enzyme and isoenzyme levels, 8-hydroxydeoxyguanosine formation and expressions of c-raf.1 and insulin-like growth factor II genes during the stages of development of hepatocellular carcinoma in rats

This is an extensive study in a defined initiation-promotion hepatocellular carcinoma model of hepatocarcinogenesis (in rats) in which many important marker enzymes and isoenzymes and 8-hydroxydeoxyguanosine formation have been studied together with two very important cellular proliferating genes, insulin-like growth factor II and c-raf.1, known for their role in hepatocellular cancer development. Experiments were carried out on hepatic tissues of male Sprague-Dawley rats. Variations in different enzyme/isoenzyme activities/contents/expression pattern and 8-hydroxydeoxyguanosine-positive cells were studied. Insulin-like growth factor II and c-raf.1 gene expressions were monitored. A direct shift with increase in size and numbers of lesions was found to occur in different experimental groups. In this study, glutathione peroxidase (1.14 and 1.46-fold) and reduced triphosphopyridine nucleotide (TPNH)-cytochrome-c-reductase (1.94 and 2.94-fold) activities, cytochrome b5 (1.57 and 3.28-fold) and P-450 contents (1.45 and 1.22-fold), glutathione content (1.27 and 1.45-fold) and superoxide dismutase and catalase (1.16 and 1.39-fold) activities in group A animals were found to be lower than those in initiation and promotion studies, respectively. 8-Hydroxydeoxyguanosine-positive nuclei count showed that oxidative damage of nuclear DNA enhanced with the progress of the disease. The insulin-like growth factor II expression was found to be predominant in hepatocellular carcinoma and in early preneoplastic lesions. Unlike insulin-like growth factor II, c-raf.1 expression was located in the late basophilic lesions associated with hepatocellular carcinoma. During the various stages of the development of hepatocellular carcinoma, the enzymes played a significant role in metabolizing carcinogens and thereby scavenging various toxic metabolites or free radicals produced. A sequence of cellular changes starting from the appearance of glycogen storage foci to basophilic foci leading to hepatocellular carcinoma via mixed cell foci varied the activity/content or expression pattern of the enzymes and isoenzymes and in 8-hydroxydeoxyguanosine formation. It has been established that c-raf.1-induced signaling pathways activated by insulin-like growth factor II is implicated in the late stage of development of cancer.

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