Cytokeratin 7/19 expression in N-diethylnitrosamine-induced mouse hepatocellular lesions: implications for histogenesis

CYP2E1 in 1,4-dioxane metabolism and liver toxicity: insights from CYP2E1 knockout mice study

1,4-Dioxane (DX), an emerging water contaminant, is classified as a Group 2B liver carcinogen based on animal studies. Understanding of the mechanisms of action of DX liver carcinogenicity is important for the risk assessment and control of this environmental pollution. Previous studies demonstrate that high-dose DX exposure in mice through drinking water for up to 3 months caused liver mild cytotoxicity and oxidative DNA damage, a process correlating with hepatic CYP2E1 induction and elevated oxidative stress. To access the role of CYP2E1 in DX metabolism and liver toxicity, in the current study, male and female Cyp2e1-null mice were exposed to DX in drinking water (5000 ppm) for 1 week or 3 months. DX metabolism, redox and molecular investigations were subsequently performed on male Cyp2e1-null mice for cross-study comparisons to similarly treated male wildtype (WT) and glutathione (GSH)-deficient Gclm-null mice. Our results show that Cyp2e1-null mice of both genders were resistant to DX-induced hepatocellular cytotoxicity. In male Cyp2e1-null mice exposed to DX for 3 months, firstly, DX metabolism to β-hydroxyethoxyacetic acid was reduced to ~ 36% of WT levels; secondly, DX-induced hepatic redox dysregulation (lipid peroxidation, GSH oxidation, and activation of NRF2 antioxidant response) was substantially attenuated; thirdly, liver oxidative DNA damage was at a comparable level to DX-exposed WT mice, accompanied by suppression of DNA damage repair response; lastly, no aberrant proliferative or preneoplastic lesions were noted in DX-exposed livers. Overall, this study reveals, for the first time, that CYP2E1 is the main enzyme for DX metabolism at high dose and a primary contributor to DX-induced liver oxidative stress and associated cytotoxicity. High dose DX-induced genotoxicity may occur via CYP2E1-independent pathway(s), potentially involving impaired DNA damage repair.

Diethylnitrosamine Induction of Hepatocarcinogenesis in Mice

Diethylnitrosamine (DEN) is a chemical hepatocarcinogenic agent that triggers a large array of oncogenic mutations after a single injection. Initiated hepatocytes subsequently undergo clonal expansion within a proliferative environment, rendering the DEN model a comprehensive carcinogen. In rodent studies, DEN finds extensive utility in experimental liver cancer research, mimicking several aspects of human hepatocellular carcinoma (HCC), including angiogenesis, metabolic reprogramming, immune exhaustion, and the ability to metastasize. Beyond the wealth of scientific insights gleaned from this model, the objective of this chapter is to review morphological, genomic, and immunological characteristics associated to DEN-induced HCC. Furthermore, this chapter provides a detailed procedural guide to effectively induce hepatocarcinogenesis in mice through a single intraperitoneal injection of DEN.

Cathepsin-facilitated invasion of BMI1-high hepatocellular carcinoma cells drives bile duct tumor thrombi formation

Bile duct tumor thrombosis (BDTT) is a complication mostly observed in patients with advanced hepatocellular carcinoma (HCC), causing jaundice and associated with poor clinical outcome. However, its underlying molecular mechanism is unclear. Here, we develop spontaneous preclinical HCC animal models with BDTT to identify the role of BMI1 expressing tumor initiating cells (BMI1high TICs) in inducing BDTT. BMI1 overexpression transforms liver progenitor cells into BMI1high TICs, which possess strong tumorigenicity and increased trans-intrahepatic biliary epithelial migration ability by secreting lysosomal cathepsin B (CTSB). Orthotopic liver implantation of BMI1high TICs into mice generates tumors and triggers CTSB mediated bile duct invasion to form tumor thrombus, while CTSB inhibitor treatment prohibits BDTT and extends mouse survival. Clinically, the elevated serum CTSB level determines BDTT incidence in HCC patients. Mechanistically, BMI1 epigenetically up-regulates CTSB secretion in TICs by repressing miR-218-1-3p expression. These findings identify a potential diagnostic and therapeutic target for HCC patients with BDTT.

Early warning and diagnosis of liver cancer based on dynamic network biomarker and deep learning

Background

Early detection of complex diseases like hepatocellular carcinoma remains challenging due to their network-driven pathology. Dynamic network biomarkers (DNB) based on monitoring changes in molecular correlations may enable earlier predictions. However, DNB analysis often overlooks disease heterogeneity.

Methods

We integrated DNB analysis with graph convolutional neural networks (GCN) to identify critical transitions during hepatocellular carcinoma development in a mouse model. A DNB-GCN model was constructed using transcriptomic data and gene expression levels as node features.

Results

DNB analysis identified a critical transition point at 7 weeks of age despite histological examinations being unable to detect cancerous changes at that time point. The DNB-GCN model achieved 100% accuracy in classifying healthy and cancerous mice, and was able to accurately predict the health status of newly introduced mice.

Conclusion

The integration of DNB analysis and GCN demonstrates potential for the early detection of complex diseases by capturing network structures and molecular features that conventional biomarker discovery methods overlook. The approach warrants further development and validation.

Babao Dan decreases hepatocarcinogenesis by inhibiting hepatic progenitor cells malignant transformation via down-regulating toll-like receptor 4

Background

Babao Dan (BBD) is a traditional Chinese medicine that has been widely used as a complementary and alternative medicine to treat chronic liver diseases. In this study, we aimed to observe the effect of BBD on the incidence of diethylnitrosamine (DEN)-initiated hepatocellular carcinoma formation in rats and explored its possible mechanism.

Methods

To verify this hypothesis, BBD was administrated to rats at a dose of 0.5g/kg body weight per two days from the 9th to 12th week in HCC-induced by DEN. Liver injury biomarkers and hepatic inflammatory parameters were evaluated by histopathology as well as serum and hepatic content analysis. We applied immunohistochemical analysis to investigate the expression of CK-19 and SOX-9 in liver tissues. The expression of TLR4 was determined by immunohistochemical, RT-PCR, and western blot analysis. Furthermore, we also detected the efficacy of BBD against primary HPCs neoplastic transformation induced by LPS.

Results

We observed that DEN could induce hepatocarcinogenesis, and BBD could obviously decrease the incidence. The biochemical and histopathological examination results confirmed that BBD could protect against liver injury and decrease inflammatory infiltration. Immunohistochemistry staining results showed that BBD could effectively inhibit the ductal reaction and the expression of TLR4. The results showed that BBD-serumcould obviously inhibit primary HPCs neoplastic transformation induced by regulating the TLR4/Ras/ERK signaling pathway.

Conclusion

In summary, our results indicate that BBD has potential applications in the prevention and treatment of HCC, which may be related to its effect on hepatic progenitor cells malignant transformation via inhibiting the TLR4/Ras/ERK signaling pathway.

Aberrant cytokeratin 7 expression by hepatocytes can predict the ductopenia grade in primary biliary cholangitis

Background

Aberrant cytokeratin 7 expression by hepatocytes (CK7⁺Hs) is the hallmark characteristic of cholestasis diseases, especially in ductopenia diseases such as primary biliary cholangitis (PBC). This study attempted to evaluate the differences and relationships between the clinical and histological features of aberrant cytokeratin 7 (CK7) expression by hepatocytes in PBC patients.

Methods

The clinicopathological data of patients diagnosed with PBC at the Second Hospital of Nanjing between January 2016 and September 2018 were analysed with SPSS 20.0.

Results

Eighty-nine PBC patients who underwent liver biopsy were enrolled in this study, and 15, 29 and 45 patients had aberrant CK7 expression by hepatocytes (CK7⁺Hs (2 +), CK7⁺Hs (1 +), and CK7⁻Hs, respectively). There were significant differences in TB, DB, ALP, TA, IgM, interface activity, and ductopenia grade between patients with CK7⁻Hs and CK7⁺Hs (2 +) (P < 0.05). The ductopenia grade was also significantly different between patients with CK7⁺Hs (2 +) and CK7⁺Hs (1 +) according to sex (P < 0.05). Upon merging the data of CK7⁺Hs (2 +) and CK7⁺Hs (1 +) into CK7⁺Hs, we found significant differences in AMA, AMA-M2, anti-gp210, TB, DB, ALP, TA, IgM, fibrosis, and ductopenia grade between CK7⁺Hs and CK7⁻Hs (P < 0.05). The odds ratios (ORs) (and 95% confidence intervals (CIs)) of CK7⁺Hs according to anti-gp210, ductopenia grade, and interface activity were 6.413 (95% CI 1.363–30.162), 4.145 (95% CI 1.898–9.052) and 3.247 (95% CI 1.556–6.775), respectively (P < 0.05). Spearman's rank correlation according to interface activity and ductopenia grade in patients with CK7⁺Hs (2 + , 1 + , 0) was r = 0.359 (P = 0.001) and r = 0.396 (P < 0.001), respectively.

Conclusion

CK7⁺Hs serves as a cholestasis index of PBC and are associated with the ductopenia grade and interface activity. Aberrant cytokeratin 7 expression by hepatocytes can predict the ductopenia grade in primary biliary cholangitis.

Oxidative stress and genotoxicity in 1,4-dioxane liver toxicity as evidenced in a mouse model of glutathione deficiency

1,4-Dioxane (DX) is a synthetic chemical used as a stabilizer for industrial solvents. Recent occurrence data show widespread and significant contamination of drinking water with DX in the US. DX is classified by the International Agency for Research on Cancer as a group 2B carcinogen with the primary target organ being the liver in animal studies. Despite the exposure and cancer risk, US EPA has not established a drinking water Maximum Contaminant Level (MCL) for DX and a wide range of drinking water targets have been established across the US and by Health Canada. The DX carcinogenic mechanism remains unknown; this information gap contributes to the varied approaches to its regulation. Our recent mice study indicated alterations in oxidative stress response accompanying DNA damage as an early change by high dose DX (5000 ppm) in drinking water. Herein, we report a follow-up study, in which we used glutathione (GSH)-deficient glutamate-cysteine ligase modifier subunit (Gclm)-null mice to investigate the role of redox homeostasis in DX-induced liver cytotoxicity and genotoxicity. Gclm-null and wild-type mice were exposed to DX for one week (1000 mg/kg/day by oral gavage) or three months (5000 ppm in drinking water). Subchronic exposure of high dose DX caused mild liver cytotoxicity. DX induced assorted molecular changes in the liver including: (i) a compensatory nuclear factor erythroid 2-related factor 2 (NRF2) anti-oxidative response at the early stage (one week), (ii) progressive CYP2E1 induction, (iii) development of oxidative stress, as evidenced by persistent NRF2 induction, oxidation of GSH pool, and accumulation of the lipid peroxidation by-product 4-hydroxynonenal, and (iv) elevations in oxidative DNA damage and DNA repair response. These DX-elicited changes were exaggerated in GSH-deficient mice. Collectively, the current study provides additional evidence linking redox dysregulation to DX liver genotoxicity, implying oxidative stress as a candidate mechanism of DX liver carcinogenicity.

Radiomics Analysis of Susceptibility Weighted Imaging for Hepatocellular Carcinoma: Exploring the Correlation between Histopathology and Radiomics Features

Purpose:

No previous researches have extracted radiomics features from susceptibility weighted imaging (SWI) for biomedical applications. This research aimed to explore the correlation between histopathology of hepatocellular carcinoma (HCC) and radiomics features extracted from SWI.

Methods:

A total of 53 patients were ultimately enrolled into this retrospective study with MR examinations undertaken at a 3T scanner. About 107 radiomics features were extracted from SWI images of each patient. Then, the Spearman correlation test was performed to evaluate the correlation between the SWI-derived radiomics features and histopathologic indexes including histopathologic grade, microvascular invasion (MVI) as well as the expression status of cytokeratin 7 (CK-7), cytokeratin 19 (CK-19) and Glypican-3 (GPC-3). With SWI-derived radiomics features utilized as independent variables, four logistic regression-based diagnostic models were established for diagnosing patients with positive CK-7, CK-19, GPC-3 and high histopathologic grade, respectively. Then, receiver operating characteristic analysis was performed to evaluate the diagnostic performance.

Results:

A total of 11, 32, 18 and one SWI-derived radiomics features were significantly correlated with histopathologic grade, the expression of CK-7, the expression of CK-19 and the expression of GPC-3 (P < 0.05), respectively. None of the SWI-derived radiomics features was correlated with MVI status. The areas under the curve were 0.905, 0.837, 0.800 and 0.760 for diagnosing patients with positive CK-19, positive CK-7, high histopathologic grade and positive GPC-3.

Conclusion:

Extracting the radiomics features from SWI images was feasible to evaluate multiple histopathologic indexes of HCC.

Heterogeneity of Epigenetic and Epithelial Mesenchymal Transition Marks in Hepatocellular Carcinoma with Keratin 19 Proficiency

OBJECTIVE

Keratin 19 (K19) expression is a potential predictor of poor prognosis in patients with hepatocellular carcinoma (HCC). To clarify the feature of K19-proficient HCC, we traced epigenetic footprints in cultured cells and clinical materials.

PATIENTS AND METHODS

In vitro, KRT19 promoter methylation was analyzed and 5-aza-2'-deoxycytidine with trichostatin A (TSA) treatment was performed. Among 564 surgically resected HCCs, the clinicopathological relevance of K19-proficent HCCs was performed in comparison with hepatocytic (HepPar-1 and arginase-1), epithelial-mesenchymal transition (E-cadherin and vimentin), biliary differentiation-associated (K7 and NOTCH-1) markers, and epigenetic markers (KRT19 promoter/long interspersed nucleotide element-1 [LINE-1] methylation status).

RESULTS

KRT19 promoter methylation was clearly associated with K19 deficiency and 5-aza-2'-deoxycytidine with TSA treatment-stimulated K19 re-expression, implicating DNA methylation as a potential epigenetic process for K19 expression. After excluding HCCs with recurrence, TNM stage as IIIB or greater, preoperative therapy, transplantation, and combined hepatocellular cholangiocarcinoma, we assessed 125 of 564 HCC cases. In this cohort, K19 expression was found in 29 HCCs (23.2%) and corresponded with poor survival following surgery (p = 0.025) and extrahepatic recurrence-free survival (p = 0.017). Compared with K19-deficient HCCs, lower KRT19 promoter methylation level was observed in K19-proficient HCCs (p < 0.0001). Conversely, HCC with genome-wide LINE-1 hypermethylation was frequently observed in K19-proficient HCCs (p = 0.0079). Additionally, K19 proficiency was associated with K7 proficiency (p = 0.043), and reduced E-cadherin and HepPar-1 expression (p = 0.043 and p < 0.0001, respectively).

CONCLUSIONS

K19-proficient HCC exhibited poor prognosis owing to extrahepatic recurrence, with molecular signatures differing from those in conventional cancer stem cells, providing novel insights of the heterogeneity underlying tumor development.

AIM2 deficiency reduces the development of hepatocellular carcinoma in mice

Chronic liver inflammation is crucial in the pathogenesis of hepatocellular carcinoma (HCC). Activation of the inflammasome complex is a key inflammatory process that has been associated with different liver diseases, but its role in HCC development remains largely unexplored. Here we analyzed the impact of different inflammasome components, including absent in melanoma 2 (AIM2) and NOD-like receptor family pyrin domain containing 3 (NLRP3), in the development of diethylnitrosamine (DEN)-induced HCC in mice. Genetic inactivation of AIM2, but not NLRP3, reduces liver damage and HCC development in this model. AIM2 deficiency ameliorates inflammasome activation, liver inflammation and proliferative responses during HCC initiation. We also identified that AIM2 is highly expressed in Kupffer cells, and that AIM2-mediated production of IL-1β by these cells is enhanced after DEN-induced liver damage. Our data indicate that AIM2 promotes inflammation during carcinogenic liver injury and that it contributes to genotoxic HCC development in mice, thereby recognizing AIM2 as a potential therapeutic target in this disease.

Seeds in the liver

The liver is a crucial organ for homeostasis and has a tremendous self-renewal and regenerative capacity. It has long been believed that the self-renewal and repair of the liver within a given physiological condition or its repopulation in chronic liver diseases, when hepatocyte proliferation is impaired, will primarily be conducted by the proliferating duct cells, termed "oval cells" or hepatic progenitor cells (HPCs). In addition, numerous studies have revealed that HPCs are the initial tumor cells of liver cancer under certain micro-environments. However, benefit from the extensive application of lineage tracing strategies using the Cre/LoxP system, researchers have redefined the fate of these bipotential cells, raising obvious controversies regarding the capacity of liver cells to control their own biology and differentiation. Here, we review the relevant articles, focusing on cell-lineage tracing to better understanding seed cells and their distinct fate in the liver.

Animal models as a tool in hepatocellular carcinoma research: A Review

Cancer is the first cause of death in developed countries and the second in developing countries. Concerning the most frequent worldwide-diagnosed cancer, primary liver cancer represents approximately 4% of all new cancer cases diagnosed globally. However, among primary liver cancer, hepatocellular carcinoma is by far the most common histological subtype. Notwithstanding the health promotion and disease prevention campaigns, more than half a million new hepatocellular carcinoma cases are reported yearly, being estimated to growth continuously until 2020. Taking this scenario under consideration and the fact that some aspects concerning hepatocellular carcinoma evolution and metastasize process are still unknown, animal models assume a crucial role to understand this disease. The animal models have also provided the opportunity to screen new therapeutic strategies. The present review was supported on research and review papers aiming the complexity and often neglected chemically induced animal models in hepatocarcinogenesis research. Despite the ongoing debate, chemically induced animal models, namely, mice and rat, can provide unique valuable information on the biotransformation mechanisms against xenobiotics and apprehend the deleterious effects on DNA and cell proteins leading to carcinogenic development. In addition, taking under consideration that no model achieves all hepatocellular carcinoma research purposes, criteria to define the " ideal" animal model, depending on the researchers' approach, are also discussed in this review.

Dietary restriction protects against diethylnitrosamine-induced hepatocellular tumorigenesis by restoring the disturbed gene expression profile

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent malignancies, worse still, there are very limited therapeutic measures with poor clinical outcomes. Dietary restriction (DR) has been known to inhibit spontaneous and induced tumors in several species, but the mechanisms are little known. In the current study, by using a diethylnitrosamine (DEN)-induced HCC mice model, we found that DR significantly reduced the hepatic tumor number and size, delayed tumor development, suppressed proliferation and promoted apoptosis. Further transcriptome sequencing of liver tissues from the DEN and the DEN accompanied with DR (DEN+DR) mice showed that DEN induced profound changes in the gene expression profile, especially in cancer-related pathways while DR treatment reversed most of the disturbed gene expression induced by DEN. Finally, transcription factor enrichment analysis uncovered the transcription factor specificity protein 1 (SP1) probably functioned as the main regulator of gene changes, orchestrating the protective effects of DR on DEN induced HCC. Taken together, by the first comprehensive transcriptome analysis, we elucidate that DR protects aginst DEN-induced HCC by restoring the disturbed gene expression profile, which holds the promise to provide effective molecular targets for cancer therapies.

Ductular reaction, cytokeratin 7 positivity, and gamma-glutamyl transferase in multistage hepatocarcinogenesis in rats

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and is characterized by multistage formation. The presence of ductular reaction, cytokeratin 7 positivity (PCK7), and increased levels of gamma glutamyltransferase (γGT) has been observed during liver carcinogenesis and contribute to tumor progression. Our goal was to evaluate the ductular reaction in multistage carcinogenesis and to correlate PCK7 and γGT levels with tumor incidence, histological characteristics, liver DNA damage index, and the expression of oxidative stress proteins. HCC was induced in 24 male Wistar rats weighing 145-150 g by chronic and intermittent exposure to 50 or 100 mg/kg diethylnitrosamine (DEN). Six control animals received only vehicle. Blood was collected to determine hepatic enzyme levels. Animals were divided into three groups: control (CO), precancerous lesions (PL), and advanced HCC. Liver samples were obtained for immunohistochemical analyses and the measurement of protein expression. Statistical analyses included Tukey's test and Pearson's correlation analyses. We observed an extensive ductular reaction in advanced HCC and a strong correlation between PCK7 and levels of γGT and the poor prognosis and aggressiveness of HCC. The extent of PCK7 and high γGT levels were associated with overexpression of inducible nitric oxide synthase (iNOS) and heat shock factor protein 1 (HSF-1). However, PCK7 and γGT levels were negatively correlated with protein expression of nuclear factor erythroid 2-related factor 2 (NRF2) and inducible heat shock protein 70 (iHSP70). These findings suggest that ductular reaction is involved in the progression of multistage hepatocarcinogenesis.

Cytokeratin-19 positivity is acquired along cancer progression and does not predict cell origin in rat hepatocarcinogenesis

Although the expression of the stem/progenitor cell marker cytokeratin-19 (CK-19) has been associated with the worst clinical prognosis among all HCC subclasses, it is yet unknown whether its presence in HCC is the result of clonal expansion of hepatic progenitor cells (HPCs) or of de-differentiation of mature hepatocytes towards a progenitor-like cell phenotype. We addressed this question by using two rat models of hepatocarcinogenesis: the Resistant-Hepatocyte (R-H) and the Choline-methionine deficient (CMD) models. Our data indicate that the expression of CK-19 is not the result of a clonal expansion of HPCs (oval cells in rodents), but rather of a further step of preneoplastic hepatocytes towards a less differentiated phenotype and a more aggressive behavior. Indeed, although HCCs were positive for CK-19, very early preneoplastic foci (EPFs) were completely negative for this marker. While a few weeks later the vast majority of preneoplastic nodules remained CK-19 negative, a minority became positive, suggesting that CK-19 expression is the result of de-differentiation of a subset of EPFs, rather than a marker of stem/progenitor cells. Moreover, the gene expression profile of CK-19-negative EPFs clustered together with CK-19-positive nodules, but was clearly distinct from CK-19 negative nodules and oval cells.

Pathogenesis and prognosis of hepatocellular carcinoma at the cellular and molecular levels

Different approaches predict the outcome for patients with hepatocellular carcinoma (HCC). The expression of biliary-hepatic progenitor cell markers generally correlates with poor prognosis. This article focuses on the pathogenesis of HCC, how differentiation or dedifferentiation leads to a phenotype switch, and heterogeneity in the same tumor. A tumor cell decides its fate based on a complex interplay of signaling pathways. Interaction with the microenvironment decides whether it will invade, proliferate, or enter survival mode. Several signaling pathways contribute to stemness features, reflecting a small chemoresistant subpopulation of the tumor that expresses biliary-hepatic progenitor cell markers.

Diethylnitrosamine (DEN)-induced carcinogenic liver injury in mice

The toxic properties of various nitrosamines in animals and humans are well established. The parenteral or oral administration of the smallest quantities of diethylnitrosamine (DEN) or dimethylnitrosamine (DMN) results in severe liver damage. Most prominent are intense neutrophilic infiltration, extensive centrilobular haemorrhagic necrosis, bile duct proliferation, fibrosis, and bridging necrosis that ends in hepatocarcinogenesis. Due to the robustness of the induced hepatic alterations, the application of DEN in rodents has become an attractive experimental model for studies aimed at understanding the pathogenetic alterations underlying the formation of liver cancer, which represents one of the most common malignancies in humans worldwide. However, several studies have shown that the hepatocarcinogenic effects of nitrosamines might vary with the genetic background of the animals, their sex, their age, and other factors that might impact the outcome of experimentation. We present general guidelines for working with DEN, and a detailed protocol that allows the establishment of highly reproducible liver cancer in mice. The outcome of liver injury after the application of DEN in mice, as estimated by the formation of cirrhosis and cancer, appears to be a suitable animal model for the analysis of some aspects and processes that promote the pathogenesis of hepatocellular carcinoma in humans.

Prognostic significance and anti-proliferation effect of microRNA-365 in hepatocellular carcinoma

MircroRNA functions as tumor suppressor or promoter in hepatocellular carcinoma (HCC). Researchers have found that miR-365 expression was lower in HCC tissues compared with that in adjacent normal tissues. However, its prognostic significance and anti-proliferation effect in HCC remain to be clarified. In this study, we firstly found that miR-365 expression was lower in HCC tissues compared with that in adjacent normal tissues. Then, we analyzed miR-365 expression level and its clinicopathological and prognostic significance. Finally, overexpression of miR-365 inhibits HCC cell proliferation and migration in vitro. Our findings suggest that miR-365 expression was an independent poor prognostic factor for HCC patient overall survival and suppressed tumor cell growth. Therefore, miR-365 may serve as a valuable prognostic marker and promising target for HCC.

N-diethylnitrosamine mouse hepatotoxicity: time-related effects on histology and oxidative stress

Animal models, namely mice, have been used to study chemically induced carcinogenesis due to their similarity to the histological and genetic features of human patients. Hepatocellular carcinoma (HCC) is a common malignancy with poor clinical outcome. The high incidence of HCC might be related to exposure to known risk factors, including carcinogenic compounds, such as N-nitrosamines, which cause DNA damage. N-nitrosamines affect cell mitochondrial metabolism, disturbing the balance between reactive oxygen species (ROS) and antioxidants, causing oxidative stress and DNA damage, potentially leading to carcinogenesis. This work addresses the progressive histological changes in the liver of N-diethylnitrosamine (DEN)-exposed mice and its correlation with oxidative stress. Male ICR mice were randomly divided into five DEN-exposed and five matched control groups. DEN was IP administered, once a week, for eight consecutive weeks. Samples were taken 18 h after the last DEN injection (8 weeks post-exposure). The following sampling occurred at weeks 15th, 22nd, 29th and 36th after the first DEN injection. DEN resulted in early toxic lesions and, from week 29 onwards, in progressive proliferative lesions. Between 15 and 29 weeks, DEN-exposed animals showed significant changes in hepatic antioxidant (glutathione, glutathione reductase, and catalase) status (p<0.05) compared with controls. These results point to an association between increased DEN-induced oxidative stress and the early histopathological alterations, suggesting that DEN disrupted the antioxidant defense mechanism, thereby triggering liver carcinogenesis.