The in vivo apoptotic effect of interferon alfa-2b on rat preneoplastic liver involves Bax protein

Type I interferon and cancer

Type I interferon (IFN) is a class of proinflammatory cytokines with a dual role on malignant transformation, tumor progression, and response to therapy. On the one hand, robust, acute, and resolving type I IFN responses have been shown to mediate prominent anticancer effects, reflecting not only their direct cytostatic/cytotoxic activity on (at least some) malignant cells, but also their pronounced immunostimulatory functions. In line with this notion, type I IFN signaling has been implicated in the antineoplastic effects of various immunogenic therapeutics, including (but not limited to) immunogenic cell death (ICD)-inducing agents and immune checkpoint inhibitors (ICIs). On the other hand, weak, indolent, and non-resolving type I IFN responses have been demonstrated to support tumor progression and resistance to therapy, reflecting the ability of suboptimal type I IFN signaling to mediate cytoprotective activity, promote stemness, favor tolerance to chromosomal instability, and facilitate the establishment of an immunologically exhausted tumor microenvironment. Here, we review fundamental aspects of type I IFN signaling and their context-dependent impact on malignant transformation, tumor progression, and response to therapy.

The anticarcinogenic effect of eugenol on lung cancer induced by diethylnitrosamine/2-acetylaminofluorene in Wistar rats: insight on the mechanisms of action

This study was designed to assess the ameliorative effects of eugenol and to propose the possible mechanisms of action of eugenol in diethylnitrosamine (DENA)/acetylaminofluorene (AAF)-caused lung cancer in Wistar rats. To induce lung cancer, DENA at a dose of 150 mg/kg body weight (b.wt) for 2 weeks were intraperitoneally injected once each week and AAF was administered orally at a dose of 20 mg/kg b.wt. four times each week for the next 3 weeks. DENA/AAF-administered rats were orally supplemented with eugenol at a dose of 20 mg/kg b.wt administered once a day until 17 weeks starting from the 1st week of DENA administration. Lung histological lesions, including sheets of tumor cells, micropapillary adenocarcinoma, and apoptotic cells, resulting from the DENA/AAF dosage, were ameliorated by eugenol treatment. However, a significant drop in the levels of LPO in the lungs and a remarkable rise in GSH content and GPx and SOD activities were observed in DENA/AAF-administered rats treated with eugenol compared with those in DENA/AAF-administered controls. Moreover, in DENA/AAF-administered rats, eugenol supplementation significantly reduced TNF-α and IL-1β levels and mRNA expression levels of NF-κB, NF-κB p65, and MCP-1 but significantly elevated the level of Nrf2. Furthermore, the DENA/AAF-administered rats treated with eugenol exhibited a significant downregulation of Bcl-2 expression levels in addition to a significant upregulation in P53 and Bax expression levels. Otherwise, the administration of DENA/AAF elevated the protein expression level of Ki-67, and this elevation was reversed by eugenol treatment. In conclusion, eugenol has effective antioxidant, anti-inflammatory, proapoptotic, and antiproliferative properties against lung cancer.

Direct and indirect effects of IFN-α2b in malignancy treatment: not only an archer but also an arrow

Interferon-α2b (IFN-α2b) is a highly active cytokine that belongs to the interferon-α (IFN-α) family. IFN-α2b has beneficial antiviral, antitumour, antiparasitic and immunomodulatory activities. Direct and indirect antiproliferative effects of IFN-α2b have been found to occur via multiple pathways, mainly the JAK-STAT pathway, in certain cancers. This article reviews mechanistic studies and clinical trials on IFN-α2b. Potential regulators of the function of IFN-α2b were also reviewed, which could be utilized to relieve the poor response to IFN-α2b. IFN-α2b can function not only by enhancing the systematic immune response but also by directly killing tumour cells. Different parts of JAK-STAT pathway activated by IFN-α2b, such as interferon alpha and beta receptors (IFNARs), Janus kinases (JAKs) and IFN‐stimulated gene factor 3 (ISGF3), might serve as potential target for enhancing the pharmacological action of IFN-α2b. Despite some issues that remain to be solved, based on current evidence, IFN-α2b can inhibit disease progression and improve the survival of patients with certain types of malignant tumours. More efforts should be made to address potential adverse effects and complications.

Protective effects of Persea americana fruit and seed extracts against chemically induced liver cancer in rats by enhancing their antioxidant, anti-inflammatory, and apoptotic activities

This study aims to explore the chemopreventive mechanisms of hydroethanolic extracts from avocado (Persea Americana) in diethylnitrosamine (DEN)/2-acetylaminofluorene (2AAF)-induced hepatocarcinogenesis. Chemical induction of hepatocarcinogenesis was induced by intraperitoneal injection of DEN at 150 mg/kg body weight (b.w.) twice a week for a fortnight, followed by oral administration of 2AAF at 20 mg/kg b.w. four times a week for 3 weeks. Rats administered DEN/2AAF were orally treated with hydroethanolic extracts of avocado fruits and seeds at a dose of 50 mg/kg b.w. every other day for 20 weeks. Moreover, rats administered DEN/2AAF and treated with avocado extracts revealed a marked decrease in liver enzyme activities, total bilirubin levels, and elevated liver tumor markers, but revealed an increase in total protein and albumin levels. The hepatocytes with hyperchromatic and bile duct cystadenoma observed in the liver of rats administered DEN/2AAF were reduced due to treatment with avocado extracts. Furthermore, the treatments prevented the elevation of lipid peroxidation levels and ameliorated the lowered glutathione peroxidase, glutathione-S-transferase, superoxide dismutase activities, and glutathione content in the liver tissues. Also, antigen Ki-67, cyclooxygenase-2, and nuclear factor kappa-B expression levels were decreased, but of the suppressor proteins p53 and BAX levels were increased in the liver of rats administered DEN/2AAF and treated with avocado extracts. In conclusion, the current results demonstrated that avocado extracts could abate hepatocarcinogenesis in rats administered DEN/2AAF through activation of antioxidant, anti-inflammatory, and apoptotic properties.

Isatin Counteracts Diethylnitrosamine/2-Acetylaminofluorene-Induced Hepatocarcinogenesis in Male Wistar Rats by Upregulating Anti-Inflammatory, Antioxidant, and Detoxification Pathways

Hepatocellular carcinoma (HCC) represents around 85% of all known types of liver cancers and is estimated to be the fifth most common cause of cancer-related death worldwide. The current study assessed the preventive efficacy of isatin on diethylnitrosamine (DENA)/2-acetylaminofluorene (2-AAF)-induced hepatocarcinogenesis in male Wistar rats and investigated the underlying cellular and molecular mechanisms. HCC was initiated by intraperitoneal injection of DENA (150 mg/kg/week) for two weeks, followed by oral 2-AAF (20 mg/kg) every other day for three successive weeks. Oral isatin or vehicle (control) was administered at 25 mg/kg for 20 weeks during and following HCC induction. Isatin ameliorated the deleterious effects of DENA/2-AAF on liver function as evidenced by reduced serum levels of AST, ALT, total bilirubin, albumin, and liver tumor biomarkers (CA19.9 and AFP) compared to control DENA/2-AAF-treated rats. Histopathological evaluations demonstrated that isatin-mediated protection against hepatocarcinogenesis was accompanied by a decline in hepatic lipid peroxidation, a marker of oxidative stress, and enhanced antioxidant capacity, as evidenced by increased glutathione and superoxide dismutase expression. Isatin treatment also upregulated expression of the major stress-response transcription factor Nrf2 and the detoxifying enzymes NAD(P)H quinine oxidoreductase and glutathione-S-transferase alpha 2 and downregulated expression of the proliferation marker Ki67. Moreover, isatin significantly reduced the DENA/2-AAF-induced decrease in hepatic expression of anti-apoptotic Bcl2 and the DENA/2-AAF-induced increases in pro-inflammatory and pro-apoptotic factors (TNF-α, NF-κB p50, NF-κB p65, p53, and caspase 3). Thus, it can be concluded that isatin may protect against chemically induced hepatocarcinogenesis by enhancing cellular antioxidant, anti-inflammatory, and detoxification mechanisms, in part through upregulation of the Nrf2 signaling pathway.

Delta-tocotrienol enhances the antitumor effects of interferon alpha through ROS and Erk/MAPK signaling pathways in hepatocellular carcinoma cells

The complexity of hepatocellular carcinoma (HCC) signaling and the failure of pharmacological therapeutics reveal the significance of establishing new anti-cancer strategies. Interferon alpha (IFN α) has been used as adjuvant therapy for reducing HCC recurrence and improving survival. Delta-tocotrienol (δ-tocotrienol), a natural unsaturated isoform of vitamin E, is a promising candidate for cancer treatment. In this study, we evaluated whether the combination of δ-tocotrienol with IFN α displays significant advantages in the treatment of HCC cells. Results showed that the combination significantly decreased cell viability, migration and invasion of HCC cells compared to single therapies. Combining δ-tocotrienol and IFN α enhanced the decrease in proliferating cell nuclear antigen (PCNA) and matrix metalloproteinases MMP-7 and MMP-9. The combination also produced an enhancement of apoptosis together with increased Bax/Bcl-xL ratio and ROS generation. δ-tocotrienol induced Notch1 activation and changes in Erk and p38 MAPK signaling status. Blocking experiments confirmed that ROS and Erk are involved, at least in part, in the anticancer effects of the combined treatment. In conclusion, the combination of δ-tocotrienol with IFN α therapy showed promising results for HCC cells treatment, which makes the combination of cytokine-based immunotherapy with natural products a potential strategy against liver cancer.

The chemoprotective effects of IFN-α-2b on rat hepatocarcinogenesis are blocked by vitamin E supplementation

Many cancer patients receive their classical therapies together with vitamin supplements. However, the effectiveness of these strategies is on debate. Here we aimed to evaluate how vitamin E supplementation affects the anticancer effects of interferon (IFN-α) using an early-model of liver cancer development (initiation-promotion, IP). Male Wistar rats subjected to this model were divided as follows: untreated (IP), IP treated with recombinant IFN-α-2b (6.5  ×  105 U/kg), IP treated with vitamin E (50 mg/kg), and IP treated with combination of vitamin E and IFN-α-2b. After treatments rats were fasted and euthanized and plasma and livers were collected. Combined administration of vitamin E and IFN-α-2b induced body weight drop, increased liver apoptosis, and low levels of hepatic lipids. Interestingly, vitamin E and IFN-α-2b combination also induced an increase in altered hepatic foci number, but not in size. It seems that vitamin E acts on its antioxidant capability in order to block the oxidative stress induced by IFN-α-2b, blocking in turn its beneficial effects on preneoplastic livers, leading to harmful final effects. In conclusion, this study shows that vitamin E supplementation in IFN-α-2b-treated rats exerts unwanted effects; and highlights that in spite of being natural, nutritional supplements may not always exert beneficial outcomes when used as complementary therapy for the treatment of cancer.

Prophylactic effects of Cynara scolymus L. leaf and flower hydroethanolic extracts against diethylnitrosamine/acetylaminoflourene-induced lung cancer in Wistar rats

The study examines the prophylactic action of artichoke leaf hydroethanolic extract (ALE) and artichoke flower head hydroethanolic extract (AFE) against diethylnitrosamine (DEN)/acetylaminofluorene (AAF)-induced lung cancer in Wistar rats. To chemically induce lung cancer, DEN was injected intraperitoneally twice a week for a fortnight at a dose of 150 mg/kg body weight (b.w.), followed by oral supplementation of AAF four times a week for 3 weeks at a dose of 20 mg/kg b.w. The DEN/AAF-administered rats were orally supplemented with ALE or AFE at a dose of 100 mg/kg b.w. for 17 weeks starting from the 1st week of DEN injection to the 17th week of the experiment. The lung cancerous injuries resulting from DEN/AAF-administration were significantly improved by the treatment with ALE and AFE as observed in histological examination. In addition, there was a significant reduction in lung lipid peroxidation, with resultant elevation in antioxidant enzymatic activity of glutathione-S-transferase, glutathione peroxidase, glutathione reductase, and superoxide dismutase as well as glutathione content in DEN/AAF-supplemented rats treated with ALE and AFE as compared to DEN/AAF-administered control. The lung tumor suppressor protein (p53) and B-cell lymphoma-2 (Bcl-2) mRNA expression significantly increased in the rats treated with ALE and AFE. In conclusion, the finding showed that ALE and AFE produced anti-cancer prophylactic effects against DEN/AAF-induced lung cancer in rats via suppression of oxidative stress and improved apoptotic signal induction.

IFN-α-2b induces apoptosis by decreasing cellular cholesterol levels in rat preneoplastic hepatocytes

IFN-α administration to patients has been long discouraged and pushed back by new and apparently better drugs; however the adverse secondary effect, the high costs and the lack of specific action, make these new drugs hard to be used and put IFN-α again in the eye of the researchers. IFN-α-2b was demonstrated to induce apoptosis and modulation of lipid metabolism and the mechanisms are still unknown. Here, we sought to find the link between these features using a model of early stage cancer development. Using in vitro and in vivo approaches, we evaluated apoptosis and lipid metabolism. IFN-α-2b induced changes in hepatic cholesterol mass due to decreased synthesis and increased secretion. Interestingly, the drop in cellular cholesterol levels was necessary for IFN-α-2b to induce apoptosis. Results presented in this paper show the complexity of the action of IFN-α-2b on the early stages of liver cancer development. We show for the first time an interrelationship between cholesterol, apoptosis and IFN-α-2b. This makes clear the need for a reevaluation of IFN-α-2b action in order to develop softer, safer and more bearable derivatives. In this regard, knowing the molecular mechanisms by which IFN-α exerts its cellular actions is of crucial importance, and it is the main condition for therapy success for classical and new malignancies.

Molecular basis of mood and cognitive adverse events elucidated via a combination of pharmacovigilance data mining and functional enrichment analysis

Drug-induced Mood- and Cognition-related adverse events (MCAEs) are often only detected during the clinical trial phases of drug development, or even after marketing, thus posing a major safety concern and a challenge for both pharmaceutical companies and clinicians. To fill some gaps in the understanding and elucidate potential biological mechanisms of action frequently associated with MCAEs, we present a unique workflow linking observational population data with the available knowledge at molecular, cellular, and psychopharmacology levels. It is based on statistical analysis of pharmacovigilance reports and subsequent signaling pathway analyses, followed by evidence-based expert manual curation of the outcomes. Our analysis: (a) ranked pharmaceuticals with high occurrence of such adverse events (AEs), based on disproportionality analysis of the FDA Adverse Event Reporting System (FAERS) database, and (b) identified 120 associated genes and common pathway nodes possibly underlying MCAEs. Nearly two-thirds of the identified genes were related to immune modulation, which supports the critical involvement of immune cells and their responses in the regulation of the central nervous system function. This finding also means that pharmaceuticals with a negligible central nervous system exposure may induce MCAEs through dysregulation of the peripheral immune system. Knowledge gained through this workflow unravels putative hallmark biological targets and mediators of drug-induced mood and cognitive disorders that need to be further assessed and validated in experimental models. Thereafter, they can be used to substantially improve in silico/in vitro/in vivo tools for predicting these adversities at a preclinical stage.

Participation of 5-lipoxygenase and LTB4 in liver regeneration after partial hepatectomy

Regeneration is the unmatched liver ability for recovering its functional mass after tissue lost. Leukotrienes (LT) are a family of eicosanoids with the capacity of signaling to promote proliferation. We analyzed the impact of blocking LT synthesis during liver regeneration after partial hepatectomy (PH). Male Wistar rats were subjected to two-third PH and treated with zileuton, a specific inhibitor of 5-lipoxygenase (5-LOX). Our first find was a significant increment of intrahepatic LTB4 during the first hour after PH together with an increase in 5-LOX expression. Zileuton reduced hepatic LTB4 levels at the moment of hepatectomy and also inhibited the increase in hepatic LTB4. This inhibition produced a delay in liver proliferation as seen by decreased PCNA and cyclin D1 nuclear expression 24 h post-PH. Results also showed that hepatic LTB4 diminution by zileuton was associated with a decrease in NF-ĸB activity. Additionally, decreased hepatic LTB4 levels by zileuton affected the recruitment of neutrophils and macrophages. Non-parenchymal cells (NPCs) from zileuton-treated PH-rats displayed higher apoptosis than NPCs from PH control rats. In conclusion, the present work provides evidences that 5-LOX activation and its product LTB4 are involved in the initial signaling events for liver regeneration after PH and the pharmacological inhibition of this enzyme can delay the initial time course of the phenomenon.

Quercetin and naringenin abate diethylnitrosamine/acetylaminofluorene-induced hepatocarcinogenesis in Wistar rats: the roles of oxidative stress, inflammation and cell apoptosis

This study was designed to assess the preventive effects and to suggest the probable mechanisms of action of quercetin and naringein in diethylnitrosamine (DEN)/2-acetylaminofluorene (2AAF)-induced hepatocarcinogenesis in Wistar male rats. The chemical-induction of hepatocarcinogenesis was performed by injection of DEN intraperitoneally at 150 mg/kg body weight (b.w.) twice/week for two weeks, followed by oral administration of 2AAF at 20 mg/kg body weight (b.w.) 4 times/week for 3 weeks. The DEN/2AAF-administered rats were co-treated with quercetin and naringenin at dose level of 10 mg/kg b. w. by oral gavage for 20 weeks. The treatment of DEN/2AAF-administered rats with quercetin and naringenin significantly prevented the elevations in serum levels of liver function indicators (ALT, AST, ALP, γ-GT, total bilirubin and albumin) and liver tumor biomarkers including AFP, CEA and CA19.9. The cancerous histological lesions and inflammatory cells infiltration in liver of DEN/2AAF-administered rats were remarkably suppressed by treatments with quercetin and naringenin. The hepatic oxidative stress markers including NO level and lipid peroxidation significantly decreased while the SOD, GPx and CAT activities and GSH content significantly increased in DEN/2AAF-administered rats treated with quercetin and naringenin when compared to DEN/2AFF-administered control rats. Furthermore, the lowered mRNA expression of liver IL-4, P53 and Bcl-2 in of DEN/2AAF-administered rats were significantly counteracted by treatment with quercetin and naringenin. Taken together, our results demonstrate that quercetin and naringenin may abate hepatocarcinogenesis via enhancement of anti-inflammatory, anti-oxidant and apoptotic actions.

First approaches for the transplantation of hepatocytes from Wistar rat preneoplastic livers into healthy recipients

BACKGROUND

the shortage of donors of hepatocyte transplantation therapy led to the use of so-called marginal donors. Some donors may have a hepatic illnesses that is associated with hepatic preneoplasia with foci of altered hepatocytes (FAH).

AIMS

to determine whether recipients developed FAH upon transplantation with hepatocytes from a preneoplastic liver and whether FAH progresses to a preneoplastic hepatocyte-derived tumor (PHDT), up to 60 days after transplantation.

MATERIAL AND METHODS

male Wistar adult rats were used as donors and recipients. Donors underwent a 2-phase model of liver preneoplasia for hepatocyte isolation. Recipients underwent a partial two thirds hepatectomy and received 150,000 hepatocytes. Recipients were euthanized seven and 60 days after transplantation. The number of FAH per liver area, percentage of liver occupied by FAH, the hepatic enzymatic profile, the percentage of prothrombin time (PT), the proliferative index (PI) and liver morphology were analyzed.

RESULTS

recipients developed few and very isolated FAH. No statistical differences were found between hepatic enzyme activities and PT. There were no differences between the groups with regard to the number of FAH per liver area and percentage of liver occupied by FAH after 60 days. The PI decreased on day 60 compared to day seven. No morphological alterations were found.

CONCLUSIONS

recipients developed few FAH that did not increase in number or size, nor did they progress to PHDT and had normal plasma biochemical features and liver morphology up to 60 days post-transplant. Additional studies are needed to determine whether FAH development constitutes a risk for recipients while waiting for whole organ transplant.

Troxerutin subdues hepatic tumorigenesis via disrupting the MDM2-p53 interaction

Hepatocellular carcinoma (HCC) is the leading cause of cancer death worldwide that lacks proper medical prognosis and treatment. In the present study, the anti-tumoral potential of troxerutin (TX), an ethnomedicine, was examined in relation to its effects on the promoter 2-acetylaminofluorene (2-AAF) in N-nitrosodiethylamine (NDEA) initiated HCC, as compared to its effects on HCC induced by NDEA alone. Liver samples from each experimental group were collected and evaluated for histological, biochemical and cellular characterization. The protein expressions of apoptotic and cell proliferation markers were determined via immunohistochemistry and western blotting. Molecular docking was also performed to delineate the inhibitory mechanism of TX on HCC. The results show that only higher doses of TX showed a significant reduction in the incidence of hepatic nodule formation, and they also counteracted NDEA plus 2-AAF induced alterations in the enzymic status. The frequencies of glutathione-S-transferase and proliferating cell nuclear antigen, markers of S phase progression, were markedly reduced during TX treatment. TX also modulated the imbalance in the MDM2-p53 interaction. The molecular docking results confirmed the interaction of TX with the upstream kinases that regulate apoptosis. This study provides evidence that a copious dose of TX is required to counteract the differential mitoinhibitory effect of 2-AAF in NDEA initiated hepatomas, and TX exhibits an anti-tumoral effect via suppressing oxidative stress, regulating liver function enzymes, inhibiting inflammatory responses and modulating MDM2-p53 interactions, thus inducing apoptosis, and thereby suggesting that TX may provide promising therapeutic effects for the chemoprevention of HCC.

Diethylnitrosamine Increases Proliferation in Early Stages of Hepatic Carcinogenesis in Insulin-Treated Type 1 Diabetic Mice

Diethylnitrosamine (DEN) induces hepatocarcinogenesis, increasing mitotic hepatocytes and leading to chronic inflammation. In addition, type 1 diabetes mellitus (T1DM) is also characterized by a proinflammatory state and by requiring insulin exogenous treatment. Given the association of diabetes, insulin treatment, and cell proliferation, our specific goal was to determine whether the liver in the diabetic state presents a greater response to DEN-induced cell cycle alteration, which is essential for the malignant transformation. Male C57BL/6 mice (four-week-old) were divided into 4 groups: C, C + DEN, T1DM, and T1DM + DEN. Mice were euthanized ten weeks after DEN injection. DEN per se produced an increase in liver lipid peroxidation levels. Besides, in T1DM + DEN, we found a greater increase in the proliferation index, in comparison with C + DEN. These results are in agreement with the increased expression observed in cell cycle progression markers: cyclin D1 and E1. In addition, a proapoptotic factor, such as activated caspase-3, evidenced a decrease in T1DM + DEN, while the Vascular Endothelial Growth Factor (VEGF) and the protooncogene p53 showed a higher increase with respect to C + DEN. Overall, the results allow us to highlight a major DEN response in T1DM, which may explain in part the greater predisposition to the development of hepatocarcinoma (HCC) during the diabetic state.

Hepatic preneoplasia induction in male Wistar rats: histological studies up to five months post treatment

BACKGROUND

Liver preneoplasia development in rats can be mimicked by an initiation-promotion model that induces the appearance of altered hepatocyte foc (FAH).

AIMS

We compare two initiation-promotion models to evaluate the presence of FAH or additional hepatic pathologies in which other organs were affected up to five month post treatment.

MATERIAL AND METHODS

FAH were induced in male adult Wistar rats with two doses of dietylnitrosamine (DEN, 150 mg/kg bw) followed by 4 doses per week (3 weeks) of 2-acetylaminofluorene (2-AAF, 20 mg/kg bw) or with one dose of DEN (200 mg/kg bw) followed by 2 doses per week (3 weeks) of 2-AAF. DEN 150, DEN 200 and control mice (received the vehicle of the drugs) groups were compared. Rats were euthanized immediately after the last dose of 2-AAF, at 3, 4 and 5 months (n = 3 euthanasia times per group). Samples of livers, lungs, kidneys, pancreatic tissue and small bowel were processed for histological and immunohistochemical analysis.

RESULTS

FAH persisted for 5 months in all livers of the DEN groups. Three months after withdrawal of 2-AAF, one rat from the DEN 150 group developed fibrosis and 5 months after 2-AAF removal another rat from the same group presented a microscopic hyperplastic nodule. Only the lungs had damage compatible with lesions induced by gavage-related reflux in DEN groups.

CONCLUSION

We concluded that up to five month post treatments, FAH persisted in all the livers from the DEN groups; livers from the DEN 200 group showed no other hepatic lesions besides FAH, and only the lungs suffered pathological alterations in both treated groups.

Attenuation of liver cancer development by oral glycerol supplementation in the rat

PURPOSE

Glycerol usage is increasing in food industry for human and animal nutrition. This study analyzed the impact of glycerol metabolism when orally supplemented during the early stage of rat liver carcinogenesis.

METHODS

Wistar rats were subjected to a 2-phase model of hepatocarcinogenesis (initiated-promoted, IP group). IP animals also received glycerol by gavage (200 mg/kg body weight, IPGly group).

RESULTS

Glycerol treatment reduced the volume of preneoplastic lesions by decreasing the proliferative status of liver foci, increasing the expression of p53 and p21 proteins and reducing the expression of cyclin D1 and cyclin-dependent kinase 1. Besides, apoptosis was enhanced in IPGly animals, given by an increment of Bax/Bcl-2 ratio, Bad and PUMA mitochondrial expression, a concomitant increase in cytochrome c release and caspase-3 activation. Furthermore, hepatic levels of glycerol phosphate and markers of oxidative stress were increased in IPGly rats. Oxidative stress intermediates act as intracellular messengers, inducing p53 activation and changes in JNK and Erk signaling pathways, with JNK activation and Erk inhibition.

CONCLUSION

The present work provides novel data concerning the preventive actions of glycerol during the development of liver cancer and represents an economically feasible intervention to treat high-risk individuals.

Cell death mechanisms in human chronic liver diseases: a far cry from clinical applicability

The liver is constantly exposed to a host of injurious stimuli. This results in hepatocellular death mainly by apoptosis and necrosis, but also due to autophagy, necroptosis, pyroptosis and in some cases by an intricately balanced combination thereof. Overwhelming and continuous cell death in the liver leads to inflammation, fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Although data from various disease models may suggest a specific (predominant) cell death mode for different aetiologies, the clinical reality is not as clear cut. Reliable and non-invasive cell death markers are not available in general practice and assessment of cell death mode to absolute certainty from liver biopsies does not seem feasible, yet. Various aetiologies probably induce different predominant cell death modes within the liver, although the death modes involved may change during disease progression. Moreover, current methods applicable in patients are limited to surrogate markers for apoptosis (M30), and possibly for pyroptosis (IL-1 family) and necro(pto)sis (HMGB1). Although markers for some death modes are not available at all (autophagy), others may not be specific for a cell death mode or might not always definitely indicate dying cells. Physicians need to take care in asserting the presence of cell death. Still the serum-derived markers are valuable tools to assess severity of chronic liver diseases. This review gives a short overview of known hepatocellular cell death modes in various aetiologies of chronic liver disease. Also the limitations of current knowledge in human settings and utilization of surrogate markers for disease assessment are summarized.

Hepatic carboxylesterase 3 (Ces3/Tgh) is downregulated in the early stages of liver cancer development in the rat

It is accepted that cancer development is associated with metabolic changes. Previously, we established a model of hepatic preneoplasia in which adult rats were subjected to a 2-phase model of hepatocarcinogenesis (initiated-promoted, IP) for 6weeks until they develop altered hepatic foci (AHF). Here, we found that a whole metabolic shift occurs in order to favor cancer development. IP animals presented with increased plasma lipids due to increased VLDL secretion as well as increased liver lipid accretion due to stimulated transacetylase activity rather than lipogenesis, compared to control rats. We found that carboxylesterase 3/triacylglycerol hydrolase (Ces3/Tgh) presented with a perilobular distribution surrounding lipid droplets in normal livers. However, it is downregulated both at the protein and mRNA level in liver homogenates and is almost undetectable inside the AHF with no changes in the surrounding tissue. Ces3/Tgh expression is regulated by ω-3 fatty acids, thus, supplementation of diet with fish oil, allowed the restoration of Ces3/Tgh expression inside the foci and, more interestingly, led to the decrease in number and volume of the AHF. These studies show a preventive role of Ces3/Tgh in liver cancer development.

FoxO3a modulation and promotion of apoptosis by interferon-α2b in rat preneoplastic liver

BACKGROUND

FoxO3a, a member of the FOXO family of transcription factors, is expressed in adult liver and modulates the expression of genes involved in apoptosis. FoxO3a is post-translationally regulated, negatively by PI3K/Akt and MAPK/Erk and positively by oxidative stress/JNK pathways. In previous works, we have demonstrated that interferon-α2b (IFN-α2b) induces apoptosis of hepatic preneoplastic foci through the production of reactive oxygen species (ROS).

AIMS

To investigate the post-translational signal events triggered by the oxidative stress induced by IFN-α2b and the modulation of FoxO3a transcriptional activity during these events in rat preneoplastic liver.

METHODS

Adult male Wistar rats were subjected to a two-phase model of hepatocarcinogenesis. A group of animals received IFN-α2b and another group received IFN-α2b and ascorbic acid (ASC), by intraperitoneal injection. Lipid peroxidation, immunohistochemistry, immunoblotting, co-immunoprecipitation and sqRT-PCR assays were performed to explore the role of ROS, JNK, Akt, Erk, FoxO3a, β-catenin and PUMA in the IFN-α2b-mediated apoptotic mechanism.

RESULTS

In vivo IFN-α2b treatment induced endogenous production of ROS which activated JNK. IFN-α2b blocked the activation of Akt and Erk, avoiding FoxO3a activity repression. Activated JNK was responsible for the nuclear translocation and transcriptional activity of FoxO3a which positively modulated the expression of PUMA, a proapoptotic player. In addition, nuclear FoxO3a competed for the nuclear β-catenin associated to TCF, inhibiting the canonical Wnt signalling pathway.

CONCLUSIONS

The data presented here propose a model in which in vivo IFN-α2b treatment induces nuclear translocation and transcriptional activity of FoxO3a, triggering the mitochondrial apoptotic pathway in hepatic preneoplastic foci.

Quercetin prevents liver carcinogenesis by inducing cell cycle arrest, decreasing cell proliferation and enhancing apoptosis

SCOPE

Quercetin is the most abundant flavonoid in human diet. It has special interest as it holds anticancerous properties. This study aims to clarify the mechanisms involved in quercetin effects during the occurrence of preneoplastic lesions in rat liver.

METHODS AND RESULTS

Adult male Wistar rats were subjected to a two-phase model of hepatocarcinogenesis (initiated-promoted group). Initiated-promoted animals also received quercetin 10 and 20 mg/kg body weight (IPQ10 and IPQ20 groups, respectively). Antioxidant defenses were modified by quercetin administration at both doses. However, only IPQ20 group showed a reduction in number and volume of preneoplastic lesions. This group showed increased apoptosis and a reduction in the proliferative index. In addition, IPQ20 group displayed a reduction of cell percentages in G₁ and S phases, accumulation in G₂, and decrease in M phase, with reduced expression of cyclin D1, cyclin A, cyclin B, and cyclin-dependent kinase 1. Interestingly, peroxisome proliferator activated receptor-α levels were reduced in IPQ20 group.

CONCLUSION

The outcomes of this study represent a significant contribution to the current understanding on the preventive mechanisms of quercetin during the early stages of liver cancer development, demonstrating that in addition to its known proapoptotic characteristics, the flavonoid modulates the expression of critical cell cycle regulators and peroxisome proliferator activated receptor-α activity.

Effects of pegylated interferon α2b on metastasis of hepatocellular carcinoma

OBJECTIVE

Interferon (IFN) has an anti-tumor activity in hepatocellular carcinoma (HCC) via anti-angiogenesis and induction of apoptosis. We have previously reported anti-metastatic effects of IFN combined chemotherapy on the outcome of HCC patients. The aim of this study was to investigate anti-metastatic effects of IFN.

METHODS

In vitro, pegylated interferon α2b (PEG-IFN-α2b) was administered to mouse MH134 cells (mouse HCC cell line, MH134), and anti-implantation effects were examined by evaluating the inhibition of cell invasion and cell proliferation. Expressions of vascular endothelial growth factor (VEGF) mRNA were also measured. In vivo, PEG-IFN-α2b was subcutaneously administered into MH134 cells and tumor growth was evaluated. In distant metastasis models, PEG-IFN-α2b was subcutaneously administered and MH134 cells were injected into the spleen. The number of liver metastases and microvessel densities (MVD) were counted.

RESULTS

In vitro, the proliferation of MH134 cells was significantly suppressed by PEG-IFN-α2b dose-dependently. MH134 cells added with PEG-IFN-α2b exhibited significantly lower levels of invasion potential. In vivo, tumor size in mice treated with PEG-IFN-α2b significantly suppressed compared with control mice (mean 0.5 versus 5.0 cm, in diameter, P < 0.05) and also decreased number of liver metastases (19.3 versus 6.0, P < 0.05). Moreover, PEG-IFN-α2b significantly suppressed angiogenesis compared with the control.

CONCLUSION

PEG-IFN-α2b in itself had remarkable anti-metastatic effects via inhibition of angiogenesis and cell adhesions.

Attenuation of the Wnt/beta-catenin/TCF pathway by in vivo interferon-alpha2b (IFN-alpha2b) treatment in preneoplastic rat livers

Wnt/beta-catenin/T cell factor (TCF) pathway is activated in several types of human cancers, promoting cell growth and proliferation. Forkhead box containing protein class O (FOXO) transcription factors compete with TCF for beta-catenin binding, particularly under cellular oxidative stress conditions. Contrary to beta-catenin/TCF, beta-catenin/FOXO promotes the transcription of genes involved in cell cycle arrest and apoptosis. We have previously demonstrated that in vivo interferon-alpha2b (IFN-alpha2b) administration induces apoptosis in preneoplastic livers, a mechanism mediated by reactive oxygen species (ROS) and transforming growth factor-beta(1) (TGF-beta(1)). This study was aimed to assess the status of the Wnt/beta-catenin/TCF pathway in a very early stage of rat hepatocarcinogenesis and to further evaluate the effects of in vivo IFN-alpha2b treatment on it. We demonstrated that the Wnt/beta-catenin/TCF pathway is activated in preneoplastic rat livers. More important, in vivo IFN-alpha2b treatment inhibits Wnt/beta-catenin/TCF pathway and promotes programed cell death possibly providing a link with FOXO pathway.

Interferon-alpha2b (IFN-alpha2b)-induced apoptosis is mediated by p38 MAPK in hepatocytes from rat preneoplastic liver via activation of NADPH oxidase

It is still unclear how Interferon-alfa (IFN-alpha) acts on preventing the appearance of hepatocarcinogenesis. We have demonstrated that IFN-alpha2b induces hepatocytic transforming growth factor-beta1 (TGF-beta(1)) production and secretion by inducing reactive oxygen species (ROS) formation through the activation of NADPH oxidase. This TGF-beta(1), alters antioxidant defences and induces programmed cell death. Since it was demonstrated that IFN-alpha induces apoptosis through the activation of p38 mitogen-activated protein kinase (p38 MAPK), this study was aimed to assess the role of this kinase in the IFN-alpha2b-induced apoptosis in rat liver preneoplasia; and to further evaluate the participation of NADPH oxidase. p38 MAPK pathway was activated during the IFN-alpha2b-induced apoptosis in rat liver preneoplasia. This activation was accompanied with phosphorylation of different transcription factors, depending on the time of IFN-alpha2b stimulus. Our data suggest that NADPH oxidase is activated by IFN-alpha2b through p38 MAPK. p38 MAPK-induced activation of NADPH oxidase is accomplished by a two-step pathway: first, ROS-independent and second ROS- and TGF-beta(1)-dependent.

Cross-talk between IFN-alpha and TGF-beta1 signaling pathways in preneoplastic rat liver

Interferon-gamma/transforming growth factor-beta (IFN-gamma/TGF-beta) pathways have opposite effects on diverse cellular functions. However, little is known about interactions between IFN-alpha/TGF-beta. In previous studies, we showed that IFN-alpha2b increases TGF-beta(1) production and secretion in hepatocytes from preneoplastic rat livers. Here, the interaction between IFN-alpha/TGF-beta(1) pathways was explored. We observed a positive cross-talk between IFN-alpha and TGF-beta(1) signaling, with activation of both pathways. p300 protein levels in hepatocytes from preneoplastic livers were enough to interact with both activated Stat1 and Smad2/3. Besides, Smad7 was not directly related with TGF-beta(1) and IFN-alpha signals. Interestingly, we reported the novel finding that the autocrine TGF-beta(1) up-regulates TGF-betaRII at protein and mRNA levels. In conclusion, the intracellular signals triggered by IFN-alpha2b and by autocrine TGF-beta(1) are integrated at the nuclear level, where activated Stat1 and Smad2/3 are capable of interact with p300, present in no restrictive cellular amounts.

Inhibition of early preneoplastic events in the rat liver by the somatostatin analog lanreotide

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death, and its incidence is increasing worldwide. Due to the known risk factors (mainly hepatitis B and C viruses), we believe there is a rationale for a chemopreventive approach to treat HCC. Here, based on described in vitro data, we evaluated the preventive effects of lanreotide, a somatostatin analog, on the induction of early carcinogenic events. We monitored preneoplastic foci induced by a two-stage initiation/promotion model of hepatocarcinogenesis in male Wistar rats, using diethylnitrosamine and 2-acetylaminofluorene. Lanreotide was given starting the day after the first diethylnitrosamine injection. By quantitative morphometry, we showed that lanreotide significantly decreases the size of induced preneoplastic foci. Analysis of proliferation and apoptosis assessed by immunohistochemistry, showed decreased proliferation and increased cell death in rats treated with lanreotide. As these events were associated with a significant decreased expression of the cell cycle regulator cyclin D1 and an increased expression of the cyclin-dependent kinase inhibitor p27(kip1) compared to the non-treated group, it is tempting to speculate that these factors are involved in the favorable effect of lanreotide. In conclusion, lanreotide significantly decreases early carcinogenic transformation in a two-step rat model. As lanreotide has a low toxicity profile, we believe it would be interesting to evaluate its effect in chemoprevention of HCC.

The PPARgamma agonist pioglitazone inhibits early neoplastic occurrence in the rat liver

Hepatocellular carcinoma (HCC) is increasing worldwide and is the fifth main cause of cancer-related death. HCC develops on a preneoplastic organ, the cirrhotic liver. Therefore, chemoprevention could play a role in the therapy of HCC. We evaluated the preventive effects of pioglitazone, a peroxisome proliferator-activated receptor gamma agonist, on the induction of early carcinogenic events. We monitored pre-neoplastic foci induced by a two-stage initiation/promotion model of hepatocarcinogenesis in rats, using diethylnitrosamine and acetylaminofluorene. Pioglitazone treatment was initiated the day after the first diethylnitrosamine injection. By quantitative morphometry and Western blot, we showed that pioglitazone significantly decreases the size of pre-neoplastic foci. Analysis of proliferation and apoptosis, assessed by immunohistochemistry, demonstrated decreased proliferation but no effect on cell death in rats treated with pioglitazone. These events were associated with an increased expression of the cyclin-dependent kinase inhibitor p27(kip1), compared to the non treated group. In conclusion, pioglitazone inhibits early carcinogenic transformation in a two-step rat model. As pioglitazone has a low toxicity profile, we believe it would be interesting to evaluate its effect in chemoprevention of HCC in humans in a clinical setting.

Hepatocytes isolated from preneoplastic rat livers are resistant to ethacrynic acid cytotoxicity

Glutathione S-transferases (GSTs) are involved in the detoxification of xenobiotics, such as several cytostatic drugs, through conjugation with glutathione (GSH). Pi class GST (GST P) liver expression is associated with preneoplastic and neoplastic development and contributes with the drug-resistance phenotype. Ethacrynic acid (EA) is an inhibitor of rat and human GSTs. In addition, causes lipid peroxidation in isolated rat hepatocytes. Therefore, we decided to evaluate the role of the GST/GSH system in isolated hepatocytes from preneoplastic rat livers (IP) in the presence of EA and determine the cytotoxicity of the drug. Our results showed a resistance to the toxic effects of EA since viability and cellular integrity values were significantly higher than control. Initial levels of thiobarbituric acid reactive substances (TBARS) in IP hepatocytes were significantly higher than control and the presence of EA did not change TBARS levels. A diminution in intracellular total GSH was observed by treating with EA isolated hepatocytes from both groups. However, the initial total GSH levels were higher in IP hepatocytes than in control. Immunoblotting analysis showed the presence of GST P in IP animals only. Although alpha and mu class isoenzymes levels were decreased in IP hepatocytes, total GST activity was 1.5-fold higher than in control. In addition, multidrug-resistance protein 2 (Mrp2) showed fivefold decreased levels in IP hepatocytes. In conclusion, increased total GSH, decreased Mrp2 levels and the presence of GST P could be critical factors involved in the resistance of IP hepatocytes to the toxicity of EA.

Involvement of reactive oxygen species on the apoptotic mechanism induced by IFN-alpha2b in rat preneoplastic liver

Interferon-alpha2b (IFN-alpha2b) is an important component in the preventive treatment of patients who have severe hepatic illness such as hepatitis B or C and hepatocarcinomas. In a previous work, using a rat liver preneoplastic model, we have demonstrated that IFN-alpha2b reduces the number and volume of altered hepatic foci (AHF) inducing apoptosis through a mechanism mediated by TGF-beta(1). In this study, the implication of hepatocytes redox status of IFN-alpha2b-treated preneoplastic liver in the TGF-beta(1)-induced apoptotic death was analyzed. Results indicate that IFN-alpha2b induces hepatocytic TGF-beta(1) production and secretion by induction of reactive oxygen species (ROS) formation through the activation of a membrane bound NADPH oxidase complex. TGF-beta(1), in turn, reduces hepatocytes antioxidant defenses and induces programmed cell death. On the other hand, it was also demonstrated that treatment of rats with IFN-alpha2b plus a ROS scavenger such as ascorbic acid, abolishes the apoptotic effect of IFN-alpha2b in rat preneoplastic livers, leading to an increase of the foci volume. In conclusion, these findings strongly suggest that ROS have a fundamental role as signaling and/or regulator molecules in the IFN-alpha2b-induced apoptosis in hepatic preneoplastic cells.

Time-dependent onset of Interferon-α2b-induced apoptosis in isolated hepatocytes from preneoplastic rat livers

We have already demonstrated that interferon alfa-2b (IFN-alpha2b) induces apoptosis in isolated hepatocytes from preneoplastic rat livers via the secretion of transforming growth factor beta(1) (TGF-beta(1)), and this process is accompanied by caspase-3 activation. The aim of this study was to further investigate the mechanism of this activation. Isolated hepatocytes from preneoplastic livers induced DNA fragmentation in response to IFN-alpha2b, which was completely blocked when anti-TGF-beta(1) was added to the culture media. IFN-alpha2b mediated radical oxygen species (ROS) production that preceded the loss of mitochondrial transmembrane potential (DeltaPsi), release of cytochrome c, and activation of caspase-3. Bax levels increased in a time-dependent fashion, and Bcl-x(L) was down-regulated in the early hours of IFN-alpha2b treatment. The delayed translocation of Bid into the mitochondria was in concordance with late caspase-8 activation. In conclusion, endogenous TGF-beta(1) secreted under IFN-alpha2b stimulus seems to induce cytochrome c release through a mechanism related to Bcl-2 family members and loss of mitochondrial DeltaPsi. Bax protein could be responsible of the release of cytochrome c during the initial hours of IFN-alpha2b-induced apoptosis via TGF-beta(1). Activated Bid by caspases could amplificate the mitochondrial events, enhancing the release of cytochrome c.

Alternative signaling pathways regulating type I interferon-induced apoptosis

Type I interferons (IFNs) are pleiotropic cytokines that exert multiple effects on normal and tumor cells. These effects are supposedly mediated through the stimulation of several signal transduction pathways by type I IFNs. These include the well-studied canonical Jak-Stat pathway, largely responsible for the antiviral and growth-inhibitory activities of IFNs, as well as the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways, whose importance in IFN-induced biologic outcomes has not been precisely established. One of the effects of type I IFNs on tumor cells is the induction of programmed cell death, apoptosis, which has been studied extensively over the last decade and has been suggested to be an important effector mechanism for IFN's antitumor effects in the treatment of cancer. The aim of this review is to summarize and discuss the recent data in the field of type I IFN-induced apoptosis, with special emphasis on the molecular mechanisms of apoptosis and on the role of alternative noncanonical signaling pathways stimulated by type I IFNs in this process.

Differential effects of interferon alpha-2b and beta on the signaling pathways in human liver cancer cells

BACKGROUND

Interferon (IFN) has been reported to reduce the incidence of hepatocellular carcinoma (HCC) in patients with chronic hepatitis C and the recurrence of HCC after effective treatment. We examined the effect of IFNs on the proliferation and the signaling pathways of human HCC cells.

METHODS

Cellular proliferation was examined by a modified 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay. Activities of signaling molecules were evaluated by Western blot analysis.

RESULTS

Cellular growth was not significantly modulated by IFNalpha-2b or by IFN-beta, even though the HCC cells expressed the IFN receptors. However, extracellular signal-regulated kinase (ERK)1/2 was activated by treatment with IFNalpha-2b, and both ERK1/2 and AKT were activated by treatment with IFN-beta, implying a possible role in resistance to IFNs. Contrary to our expectations, inhibition of mitogen-activated ERK-regulating kinase (MEK) or phosphatidylinositol-3-OH kinase (PI3K) did not modulate the proliferation of HCC cells. Also, abrogation of the ERK1/2 and AKT signaling pathways did not affect cell-cycle arrest at the G1/S phase caused by IFNalpha-2b.

CONCLUSIONS

IFNalpha-2b and IFN-beta activated ERK1/2 and/or AKT independently of modulating the proliferation of HCC cells and the cell-cycle machinery. A signal transduction-based approach for HCC treatment needs to focus on other possible signaling molecules besides ERK1/2 and AKT when challenged with IFNs.

Interferon-alphaCon1 suppresses proliferation of liver cancer cell lines in vitro and in vivo

BACKGROUND/AIMS

We investigated the effects of consensus interferon (IFN-alphaCon1), a nonnaturally occurring type I interferon with higher specific activity than other type I IFNs, on the growth of human liver cancer cells.

METHODS

The effect of IFN-alphaCon1 on the proliferation of 13 liver cancer cell lines was investigated in vitro. Hepatocellular carcinoma (HCC) cells (KIM-1 and HAK-1B) were transplanted subcutaneously into the back of nude mice, then IFN-alphaCon1 was subcutaneously administered to the mice once a day for 2 weeks, and tumor volume and histology were examined.

RESULTS

IFN-alphaCon1 expressed a dose-dependent growth inhibitory effect in all cell lines in vitro. KIM-1 tumor volume in mice that received 0.01 microg (10(4)IU)/mouse/day of IFN-alphaCon1 (similar to the clinical dose for chronic hepatitis C) was 62% of the control, 0.1microg/mouse/day resulted in 26%, and 1 microg/mouse/day resulted in 10%. HAK-1B tumor volume under the same treatment was 61, 24 and 0% of the control, respectively. The number of apoptotic cells significantly increased and the number of blood vessels significantly decreased with the increase in IFN-alphaCon1 dose.

CONCLUSIONS

IFN-alphaCon1 suppressed HCC growth in nude mice. These data indicate the potential clinical application of IFN-alphaCon1 in the prevention and treatment of HCC.

Interferon alpha-induced apoptosis on rat preneoplastic liver is mediated by hepatocytic transforming growth factor beta(1)

In previous work we showed that interferon alfa-2b (IFN-alpha2b) increases apoptosis on rat hepatic preneoplastic foci. The aim of this study was to determine if transforming growth factor beta1 (TGF-beta1) was involved in the programmed cell death on the foci. Animals were divided into 6 groups: subjected to a 2-phase model (diethylnitrosamine plus 2-acetylaminofluorene) of preneoplasia development (group 1); treated with IFN-alpha2b during the 2 phases (group 2); treated with IFN-alpha2b during initiation with diethylnitrosamine (group 3); treated with IFN-alpha2b during 2-acetylaminofluorene administration (group 4); subjected only to an initiation stage (group 5); and treated with IFN-alpha2b during the initiation period (group 6). Serum TGF-beta1 levels were increased in IFN-alpha2b-treated rats. Immunohistochemical studies showed that IFN-alpha2b significantly increased the quantity of TGF-beta1-positive hepatocytes in groups 2 to 4. Phosphorylated-Smads-2/3 (p-Smads-2/3) proteins in liver nuclear extracts were significantly elevated. To determine the source of TGF-beta1, isolated hepatocytes, Kupffer cells, and peritoneal macrophages from animals in groups 1 and 5 were cultured with or without IFN-alpha2b. IFN-alpha2b stimulus induced several-fold increases of TGF-beta1 secretion from hepatocytes. Neither Kupffer cells nor peritoneal macrophages secreted detectable TGF-beta1 levels when they were treated with IFN-alpha2b. IFN-alpha2b-stimulated cultured hepatocytes from preneoplastic livers showed enhanced apoptosis, measured by fluorescence microscopy and caspase-3 activity. They presented higher nuclear accumulation of p-Smads-2/3, indicating increased TGF-beta1 signaling. When anti-TGF-beta1 was added to the culture media, TGF-beta1 activation and apoptosis induced by IFN-alpha2b were blocked. In conclusion, IFN-alpha2b-induced production of TGF-beta1 by hepatocytes from preneoplastic liver is involved in the apoptotic elimination of altered hepatic foci.