Risk Of Developing Liver Cancer Research Articles

Modeling the Risk of Liver Cancer in Adults: A Machine Learning Investigation into the Role of Obesity and Overweight

Background: Liver cancer is a global health concern, with overweight and obese individuals exhibiting an increased risk of its development. Understanding the interplay between obesity-related factors and liver cancer incidence is crucial for early prediction and intervention. Aim: The aim of this investigation was to construct and validate an extreme gradient boosting (XGBoost) based machine learning model for the purpose of establishing a one-year liver cancer risk prediction system specifically tailored to overweight and obese patients. In addition, this study sought to compare the predictive performance of the XGBoost model with those of a random forest model and a logistic regression model, while also identifying the most influential predictive features for liver cancer incidence. Methods: A comprehensive retrospective analysis was conducted on MIMIC III data comprising 2,354 patients. To predict the risk of liver cancer development, three machine learning models were developed: XGBoost, random forest, and logistic regression. Feature selection was executed using a stepwise regression procedure encompassing both forward selection and backward elimination. Results: The stepwise regression technique unveiled 14 predictive factors for liver cancer incidence. Among the patient cohort, 132 individuals developed liver cancer within a year of follow-up, while 2,222 did not. Notably, most liver cancer cases occurred in male patients (60%). Statistically significant differences were observed between patients with liver cancer and those without, in terms of age, gender, total bilirubin, platelet, albumin, chloride, potassium, sodium, prothrombin time (PT) and alanine aminotransferase (ALT). The XGBoost model exhibited an impressive area under the receiver operating characteristic curve (AUROC) of 99%, Random Forest (RF) of 99%, and Logistic Regression (LR) of 90%. In a multivariate analysis, total bilirubin, creatinine levels, age, gender, ALT, alkaline phosphate (ALP), PT, calcium, and chloride emerged as independent predictors for liver cancer incidence. Conclusion: The XGBoost model demonstrated superior predictive performance when compared to the RF and LR models. If corroborated through prospective studies, the XGBoost model may prove to be a valuable tool for the early prediction of liver cancer risk in overweight or obese individuals. Such predictive capabilities could, in turn, facilitate the implementation of timely preventive interventions against liver cancer.

Western diet unmasks transient low-level vinyl chloride-induced tumorigenesis; potential role of the (epi-)transcriptome

Background & aimsVinyl chloride (VC) monomer is a volatile organic compound commonly used in industry. At high exposure levels, VC causes liver cancer and toxicant-associated steatohepatitis. However, lower exposure levels (i.e., sub-regulatory exposure limits) that do not directly damage the liver, enhance injury caused by Western diet (WD). It is still unknown if the long-term impact of transient low-concentration VC enhances the risk of liver cancer development. This is especially a concern given that fatty liver disease is in and of itself a risk factor for the development of liver cancer. MethodsC57Bl/6 J mice were fed WD or control diet (CD) for 1 year. During the first 12 weeks of feeding only, mice were also exposed to VC via inhalation at sub-regulatory limit concentrations (<1 ppm) or air for 6 h/day, 5 days/week. ResultsFeeding WD for 1 year caused significant hepatic injury, which was exacerbated by VC. Additionally, VC increased the number of tumors which ranged from moderately to poorly differentiated hepatocellular carcinoma (HCC). Transcriptomic analysis demonstrated VC-induced changes in metabolic but also ribosomal processes. Epitranscriptomic analysis showed a VC-induced shift of the modification pattern that has been associated with metabolic disease, mitochondrial dysfunction, and cancer. ConclusionsThese data indicate that VC sensitizes the liver to other stressors (e.g., WD), resulting in enhanced tumorigenesis. These data raise concerns about potential interactions between VC exposure and WD. It also emphasizes that current safety restrictions may be insufficient to account for other factors that can influence hepatotoxicity.

An elevated FIB-4 score is associated with an increased incidence of liver cancer: A longitudinal analysis among 248,224 outpatients in Germany

BackgroundNon-invasive tests such as the FIB-4 index (calculated on the basis of patients’ age, AST/ALT levels and platelet count) have been recommended by different guidelines to rule out advanced fibrosis and stratify the risk of liver-related outcomes in patients with chronic liver diseases. An elevated FIB-4 index ≥1.3 is an independent predictor for liver cancer development among patients with NAFLD. However, the predictive value of an elevated FIB-4 index regarding (liver) cancer development among the general population is unknown. MethodsUsing the Disease Analyzer database (IQVIA) which compiles diagnoses, laboratory values, and basic medical and demographic data for over 7.5 million patients followed in general practices in Germany, we identified 248,224 patients with available lab values for FIB-4 index calculation between 2005 and 2019. Patients with an average FIB-4 index of <1.3 were matched 1:1 to patients with a FIB-4 index of ≥1.3 by age and sex. ResultsWithin 10 years of the index date, the cumulative incidence of liver cancer was significantly higher in patients with a FIB-4 index ≥1.3 (0.25% versus 0.04%, p < 0.001). In a multivariate Cox-regression analysis, this association was found to be higher in patients with pre-existing liver disease (hazard ratio, HR: 10.54 versus 3.79). The risk of liver cancer development was most pronounced among men (HR: 9.40, p < 0.001) and patients ≤50 years of age (HR: 16.36, p < 0.001). A persistently high or increasing FIB-4 index over time was a strong predictor for liver cancer. Notably, the cumulative incidence of cancer in general was comparable among patients with a low/high FIB-4 index (15.7% versus 16.6%; p = 0.060). ConclusionOur data support the use of the FIB-4 index to estimate the risk of liver cancer development even in unselected patients without pre-existing liver disease. By contrast, the index does not appear to have any predictive value for other tumour sites.

Risk of hepatocellular carcinoma after HCV eradication: Determining the role of portal hypertension by measuring spleen stiffness

Background & AimsHepatitis C virus (HCV) eradication with direct-acting antivirals (DAAs) reduces but does not eliminate the risk for hepatocellular carcinoma (HCC). The development of surveillance strategies for HCC after the sustained virologic response (SVR) is therefore warranted. We aimed to evaluate the role of spleen stiffness measurement (SSM) in the prediction of HCC risk in a cohort of patients with advanced chronic liver disease (ACLD) treated with DAAs.MethodsThis is a retrospective cohort study of 140 patients with HCV-related ACLD successfully treated with DAAs in our centre between 2015 and 2017. Patients with available liver stiffness (LSM) and SSM before treatment and 6 months after (SVR24) were included. A Cox regression model investigated the association between SSM and HCC development.ResultsDuring a median follow-up of 41.5 (IQR 32–49) months, 20 patients presented with HCC. SSM at SVR24 predicted HCC development in univariate and adjusted multivariate analysis (hazard ratio: 1.025; 95% CI: 1.001–1.050); the best cut-off was 42 kPa. Patients with LSM-SVR24 ≤10 kPa were at the lowest risk of HCC. In patients with LSM-SVR24 >10 kPa, HCC incidence was not further influenced by LSM values (10–20 kPa vs. >20 kPa), but only by SSM-SVR24 values (≤42 vs. >42 kPa).ConclusionsPortal hypertension, as evaluated by SSM, plays a significant role in liver carcinogenesis after DAA treatment. We proposed a new algorithm based on post-treatment values of LSM and SSM for the stratification of HCC risk after SVR achievement.Lay summarySpleen stiffness predicts the development of hepatocellular carcinoma after viral eradication, especially in patients with post-treatment liver stiffness values >10 kPa. An algorithm based on liver and spleen stiffness can stratify for the risk of liver cancer development and guide the surveillance strategies after treatment with direct-acting antivirals.

Hypoxia-inducible factor-1α mediates and regulates angiogenesis-related factors expression in hepatocellular carcinoma

Objective: To investigate the expression of hypoxia-inducible factor (HIF)-1α, vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) during the progression of liver diseases and the molecular mechanism of HIF-1α in regulating the expression of angiogenic factors in hepatocellular carcinoma (HCC). Methods: Serum samples from hospitalized patients with liver cancer, liver cirrhosis, and chronic hepatitis were collected, and healthy people were used as controls. Mouse models of hepatocarcinogenesis were used to detect the dynamic expression of HIF-1α, VEGF and Ang-2. Enzyme-linked immunosorbent assay was used to quantitatively analyze the serum levels of HIF-1α, VEGF and Ang-2 in patients with liver disease and mice. HIF-1α-specific miRNA expression plasmids was constructed to transfect HepG2 human HCC cells. HIF-1α mRNA transcriptional interference effects were analyzed on biological behavior, VEGF and Ang-2 expression, and epithelial mesenchymal transformation (EMT) in human HCC cell line. The sample means of multiple groups were compared by analysis of variance and q test and the sample rate was compared by χ (2) test. Results: In patients with chronic liver disease, the serum expression of HIF-1α, VEGF and Ang-2 in the liver cancer group (145.6 ± 32.6) μg/L, (458.9 ± 125.3) μg/L and (42.9 ± 5.1) μg/L was significantly higher than the liver cirrhosis (P < 0.001) (79.5 ± 28.4) μg/L, (206.8 ± 56.8) μg/L and (26.2 ± 6.1) μg/L and chronic hepatitis group (60.1 ± 18.8) μg/L, (178.1 ± 85.4) μg/L and (21.8 ± 6.9) μg/L. In addition, HIF-1α was positively correlated with VEGF (r = 0.937, P < 0.001), HIF-1α and Ang-2 (r = 0.933, P < 0.001), and VEGF and Ang-2 (r = 0.910, P < 0.001). Mouse models of hepatocarcinogenesis confirmed that HIF-1α, VEGF and Ang-2 had progressively increased during the process of malignant transformation from normal hepatocytes, hepatocyte degeneration, and precancerous lesions to canceration. HIF-1α miRNA intervention plasmid had transformed HepG2 cells. Compared with the blank group, HIF-1α mRNA, HIF-1α, VEGF and Ang-2 were decreased by 88.1%, 59.8%, 54.0% and 36.0% at 72h, respectively. The expression level of EMT-related protein Snail (0.26 ± 0.02 and 0.67 ± 0.09, q = 6.75, P < 0.003), VIM (0.27±0.08 and 0.73±0.04, t = 10.35, P < 0.001) and Twist (0.24 ± 0.07 and 0.73 ± 0.02, q = 12.08, P < 0.001) was significantly reduced, but the expression level of E-cadherin (0.76 ± 0.08 and 0.27 ± 0.09, q = 7.05, P < 0.002) was significantly increased. Conclusion: HIF-1α mediates and regulates angiogenesis-related factors such as VEGF and Ang-2 expression in hepatocellular carcinoma. Furthermore, HIF-1α transcriptional interference can significantly affect the biological characteristics and EMT transformation of hepatocellular carcinoma cells.

Risk Assessment of Aflatoxins in Maize-Groundnuts Complemen-tary Foods Consumed by Ghanaian Infants

Background: Complementary foods are given to infants when breast milk alone becomes insufficient in meeting their nutritional needs. The major objective of this study was to assess the prevalence of Aflatoxins (AFs) in Weanimix complementary foods purchased from shops in Accra (Ghana), and to estimate risk of liver cancer development in infants. &#x0D; Methods: In total, 32 samples of Weanimix were purchased from shops in Accra, an urban centre and analyzed for AFs by Reverse-Phase High Performance Liquid Chromatography (RP-HPLC). Previously published data on levels of AFs in Weanimix prepared in rural households were also collected. The data was analyzed to estimate infants’ daily exposure to AFs as well as the risk of liver cancer development.&#x0D; Results: AFs levels of 18.8% of samples were above the maximum permitted limit of 10 µg/kg. The minimum and maximum levels of total AFs detected in all samples were 2.51 and 98.87 µg/kg, respectively with a mean value of 16.43 µg/kg. Exposure assessment showed that the minimum and maximum daily AFs exposures were 0.044 and 2.805 µg/kg bw/d, respectively for Weanimix from rural households; these rates for Weanimix purchased from urban shops were 0.014 and 0.55 µg/kg bw/d, respectively. The chances of liver cancer development would increase to 0.6 per year if infants were fed on Weanimix prepared in rural households with minimum AF level of 7.9 µg/kg.&#x0D; Conclusion: The infants fed on Weanimix prepared in rural households would be at a higher risk of AF exposure and liver cancer development than infants fed on Weanimix purchased from urban shops of Ghana.

ERADICATION OF HCV INFECTION IN PATIENTS WITH LIVER CIRRHOSIS: FACTOR OF CANCER PREVENTION OR CARCINOGENESIS?

Hepatocellular carcinoma (HCC) is one of the most common causes of death from cancer and is the final stage of chronic liver disease, usually occurring in patients with cirrhosis (CP). Chronic infection with hepatitis C virus (HCV) leads to progressive liver inflammation and cirrhosis because this virus specifically affects liver tissue. Previously used interferon therapy had a relatively low efficiency and very high risks of side effects. During the period of administration of interferon (IFN) schemes it was proved that elimination of the virus significantly reduced risk of liver cancer development. Discovery of direct-acting antiviral (DAA ) drugs have revolutionized HCV therapy with virus elimination rate of more than 95 % and an excellent safety profile. However, the risk of transformation of liver cirrhosis into hepatocellular carcinoma is still high even after complete eradication of the virus. Numerous studies have shown conflicting results on the possible relationship between the use of new antiviral drugs and the increase in the frequency of newly diagnosed or recurrent hepatocellular carcinoma. Thus, the long-term prognosis in terms of risk for HCC development among patients with sustained virological response (SVR) remains unclear.The purpose of the studywas to analyze the literature on the effect of antiviral therapy of chronic hepatitis C with interferon-containing regimens and drugs of direct antiviral action on the risk of developing or recurring hepatocellular carcinoma.Material and Methods. We analyzed publications available from PubMed, S copus, E-library, Web of S cience using the key words “hepatocellular carcinoma”, “chronic hepatitis C”, “direct-acting antiviral drugs”, “liver cirrhosis”, “interferons”, and “sustained virological response”. Of the 99 studies found, 21 were used to write a systematic review.Results.Eradication of the virus reduces the risks of HCC. Despite reports on high risk of occurrence or recurrence of hepatocellular carcinoma in patients with cirrhosis after treatment with DAA s compared with interferon-containing regimens, there is not enough data confirming the direct link between the use of DAA s and the development of hepatocellular carcinoma. No statistically significant difference in the frequency of HCC between patients treated with interferon or DAA s was detected.Conclusion.Eradication of the virus is the most significant factor in the prevention of HCC; therefore, treatment of CHC should not be delayed due to the risk of HCC. Patients with liver cirrhosis require a long period of follow-up, even after successful treatment of chronic hepatitis C with DAA drugs. Stratification of HCC risk requires further research.

Liver Cancer in Tyrosinemia Type 1.

Hereditary Tyrosinemia type I (HT1) is clinically mainly characterised by severe liver disease. Most patients present in their first months of life with liver failure, but others can present later with issues of compensated cirrhosis, renal tubulopathy or acute intermittent porphyria. If patients survive the acute phase with liver failure or if they present later with compensated cirrhosis, they often develop hepatocellular carcinoma early but also later in life. The course of the disease changed after the introduction of 2-(2 nitro-4-3 trifluoro-methylbenzoyl)-1, 3-cyclohexanedione (NTBC), which blocks the tyrosine degradation pathway at an earlier step. Therefore, the toxic products did not accumulate anymore and all clinical problems resolved. However, the risk (although clearly decreased) for developing liver cancer remained, especially if NTBC treatment is initiated late, a slow decrease of the tumor marker α-fetoprotein is seen or if the α-fetoprotein concentrations remain just above the normal range. A rise of α-fetoprotein in these HT1 patients is more or less pathognomonic for liver cancer. Although hepatoblastoma development occurs in HT1 patients, most HT1 patients develop hepatocellular carcinoma (HCC) or a mixed type of carcinoma consisting of HCC and hepatoblastoma. Due to the small risk of liver cancer development, screening for liver cancer (especially HCC) is still recommended in HT1 patients using regular measures of α-fetoprotein and imaging. Ultrasound is mostly the modality of choice for surveillance, because it is widely available, it does not use radiation and is noninvasive. When a suspicious lesion is present, the higher sensitivity of MRI could be used for characterization and staging of lesions. At this moment, no HCC development in pre-symptomatically treated patients is reported. These different situations could possibly indicate that NTBC can prevent the start of the development of HCC when initiated early, but can't stop the development of HCC if it is prescribed at a later stage, stressing the importance of early diagnosis.

PNPLA3 rs738409, hepatocellular carcinoma occurrence and risk model prediction in patients with cirrhosis

Several studies have reported an association between the genetic variant rs738409 (G) in the PNPLA3 gene and the risk of cirrhosis in various liver diseases. Our purpose was to assess the influence of this polymorphism on the risk of hepatocellular carcinoma (HCC) occurrence in two distinct longitudinal cohorts of patients with cirrhosis as well as its possible usefulness in HCC-risk model prediction. PNPLA3 rs738409 genotypes were assessed in 279 patients with alcoholic- and 253 patients with HCV-related cirrhosis. These patients were followed-up and screened for the risk of HCC, and the influence of rs738409 on the occurrence of liver cancer was assessed using the Kaplan-Meier method, then according to the multivariate Cox model. In patients with HCV-related cirrhosis, rs738409 genotypes did not influence the risk of HCC development (log-rank = 0.7) or death (log-rank = 0.2). Conversely, in patients with alcoholic cirrhosis, the rs738409 (GG) genotype was an independent risk factor for HCC occurrence (HR = 1.72 [1.21-2.45], log-rank = 0.002) as well as older age, male gender, and higher BMI. Combining these features enabled HCC-risk stratification of this population into three groups with the 6-year cumulative incidence ranging from 3.4% (low risk, n = 58), 12.2% (intermediate risk, n = 163), and 51.7% (high risk, n = 58), respectively (HR = 4.3 [2.7-6.4]; log-rank <0.0001). This study provides key data that affirm the influence of the rs738409 (GG) genotype on the occurrence of HCC in patients with alcoholic cirrhosis. Its combination with clinical features refines the selection of patients at higher risk of liver cancer development.

Serum Ferritin Level and Risk of Liver Cancer Development in Patients With Chronic Liver Diseases

Purpose: Radiofrequency ablation (RFA) is a safe and effective technique for hepatocellular carcinoma and it has minimal morbidity and mortality. One of the most important major complications of RFA is perforation of the gastrointestinal tract, which occurs when the tumor is adjacent to the digestive tract. In particular, the risk is much higher in patients with lesions located within 1 cm from the liver surface in proximity to the digestive tract. In such cases, an artificial ascites technique has been employed. However, the separation of adjacent digestive organ from the liver is insufficient in this method. Therefore, in this study, to overcome this problem, we devised a novel RFA technique using a double-balloon catheter. In the first step, an animal experiment was performed to evaluate the safety and feasibility of the balloon RFA method. In the second step, the human pilot trial was carried out to evaluate the safety, feasibility and effectiveness of this method. Materials and Methods: We produced an 8 Fr silicone catheter equipped with 2 balloons of 2.5 cm diameter. In experiments using pigs, we first inserted this balloon catheter percutaneously into the peritoneal space between the liver and gastrointestinal tracts, filled it with cooled water, and performed RFA for in normal liver 1 cm from the liver surface. Then, heat damage to the excised liver and gastrointestinal tract was evaluated macroscopically andmicroscopically. In a human pilot study, balloon catheter RFA was performed in 4 patients with HCC (1.5 ± 0.7 cm) abutting the gastrointestinal tract. Results: In pigs, we performed each 6 RFA sessions with or without balloon catheter. It was technically easy to place the balloon catheter between liver and gastrointestinal tracts to separate them. Heat damage reached the liver surface in all lesions. In the groupwith balloon catheter, no heat damage of the gastrointestinal tracts was observed (0%, 0/6). In contrast, in the group without balloon catheter, heat damage was observed in 5/6 (83.3%): stomach (2/6), small intestine (2/6), and omentum (1/6). The coolant temperature in the balloon was significantly increased after RFA, suggesting that the heat generated by RFA was absorbed by the coolant. In the human pilot study, balloon catheter RFA was easily performed in all patients without associated complications. CT confirmed complete ablation with an appreciable safety margin in all patients, without recurrence for 20.3 ± 4.5 months. Conclusions: RFA with our balloon catheter is safe and effective for the treatment of HCC abutting the gastrointestinal tract, suggesting an expanded indication of these lesions for RFA.

Serum level of adiponectin and the risk of liver cancer development in chronic hepatitis C patients

Obesity and metabolic syndrome are recognized risk factors for development of hepatocellular carcinoma (HCC) in patients with chronic hepatitis C (CHC). Dysregulation of adipokines, particularly the decreased secretion of adiponectin, appears to play a key role. To investigate the association between adiponectin and hepatocarcinogenesis, we conducted a large-scale retrospective cohort study. We enrolled 325 patients with CHC (146 men, 179 women; mean age 58.0 ± 10.3 years) whose serum samples were collected between January 1994 and December 2002. Subjects were divided into two groups according to their serum adiponectin levels. We evaluated the association between adiponectin level and the risk of subsequent HCC development using univariate and multivariate Cox proportional hazard regression. Because average serum adiponectin level was higher in females than males, each gender was analyzed separately. Patients with CHC had significantly higher adiponectin levels than healthy controls. During the follow-up period (mean: 9.0 years), HCC developed in 122 subjects. Unexpectedly, subjects with higher serum adiponectin levels had a higher incidence of HCC (males: p = 0.032; females: p = 0.01; log-rank test). Multivariate analysis revealed that a high serum adiponectin level was independently associated with HCC development (hazard ratio [HR] = 2.07; p = 0.031 in females and HR = 1.82; p = 0.05 in males). Isoform analysis revealed that middle- and low-molecular-weight isoforms contributed to the risk of HCC. In conclusion, Patients who had CHC with high serum adiponectin levels had a higher risk of liver cancer development. Adiponectin may thus be tumorigenic or indicate a liver disease state independently of other clinical parameters.

The Pro variant of the p53 codon 72 polymorphism is associated with hepatocellular carcinoma in Moroccan population

Codon 72 polymorphism of the p53 gene has been implicated in cancer risk, and it has been suggested that it may have an impact on the clinical outcome of the disease. Our objective was to evaluate the association between p53 polymorphism at codon 72 and hepatocellular carcinoma (HCC) in the Moroccan population. Genomic DNA was extracted from peripheral blood cells of 96 patients with HCC and 222 controls without HCC matched for age, gender and ethnicity. Codon 72 polymorphism of p53 was identified by PCR-restriction fragment length polymorphism, confirmed by sequencing. Patients with HCC had higher frequencies of Pro/Pro (13.5% vs. 6.3%, P < 0.02) than controls and consequently a 2.3-fold increased risk of liver cancer development (odds ratio [OR], 2.304; 95% confidence interval [CI], 1.014-5.234). In addition, we found a significant association between the p53Arg72Pro polymorphism and the female gender in HCC. Men with Pro/Pro genotype had a 1.57-fold increased risk for HCC, whereas the corresponding genotype in women had a 4.4-fold increased risk of HCC (OR, 4.4; 95% CI, 1.18-16.42). No correlation between the polymorphism and HCC risk was found when comparing the hepatitis C virus (HCV)-positive cases to HCV-positive controls. However, HCV-negative subjects and Pro/Pro genotype had a 3.31-fold increased risk for HCC. These results provide evidence that p53 polymorphism at codon 72 is a modifier of hepatocarcinogenesis, especially in women and HCV-negative subjects.

Tyrosinemia type I treated by NTBC: How does AFP predict liver cancer?

Background Tyrosinemia type I is associated with an increased risk of liver cancer development. The formation of the pathogenic fumarylacetoacetate is prevented by 2-(2-nitro-4-3 trifluoro-methylbenzoyl)-1,3-cyclohexanedione (NTBC). Still, some patients with NTBC treatment develop liver cancer. A rise of α-fetoprotein (AFP) is an indicator of liver cancer. Aim To study the predictive value of AFP in tyrosinemia type I patients for the discrimination between patients at high and low risk of liver cancer development. Methods We examined the course of AFP values of 11 Dutch patients with tyrosinemia type I treated by NTBC, of whom four were diagnosed with liver cancer. Results The four patients with liver cancer had a course of AFP different from the other patients in either velocity of the decrease of AFP, achieving normal AFP and/or having a rise of AFP concentrations. Conclusion Apart from a rise of AFP, a slow AFP decrease, and never normalizing levels of AFP are important predictors of liver cancer development in further life.

Perturbations of endogenous levels of orotic acid and carcinogenesis: effect of an arginine-deficient diet and carbamyl aspartate on hepatocarcinogenesis in the rat and the mouse.

Feeding excess orotic acid (OA) in the diet promotes the carcinogenic process in different organs including the liver. A number of metabolic and genetic disorders are associated with increased synthesis of endogenous OA and some of these disorders appear to pose an increased risk of liver cancer development. This study therefore examines whether excess OA of endogenous origin also exerts a promoting effect on hepatocarcinogenesis in the mouse and the rat. Increased endogenous synthesis of OA was achieved by (i) feeding a diet deficient in arginine (AD) and (ii) feeding excess dietary carbamylaspartate (CA), a precursor for the synthesis of OA. A single dose of diethylnitrosamine (DENA) was given i.p. to male Fischer 344 rats (200 mg/kg) or to male DBA/2 mice (90 mg/kg). One week later they were placed on either AD diet or the same diet supplemented with 1.35% arginine (AS) for a total of 4 weeks. Two-thirds partial hepatectomy (PH) was performed at the end of the second week. All animals were then transferred to a control semisynthetic basal diet for a total of 20 weeks before they were killed. The results indicated that AD diet increased the incidence of hepatic nodules in both rats (percentage area occupied by nodules was 4.7 +/- 0.4 in the AD group compared to a control value of 0.7 +/- 0.5) and mice (4/10 mice had nodules > 5 mm diameter in the AD group while none in the AS group had such large nodules). In another experiment male Fischer 344 rats similarly initiated with DENA were exposed to either basal diet or basal diet containing 2% CA for 4 weeks coupled with PH performed at the end of the second week. This regimen was followed by 20 weeks of feeding basal diet to both groups. Rats given CA developed larger hepatic foci and nodules (0.84 +/- 0.56 mm3) compared to the control group, which was fed basal diet throughout the experiment (0.07 +/- 0.03 mm3). Further, both AD diet and dietary CA, like dietary OA, induced an increase in hepatic uridine nucleotides. Taken together, these results suggest that increased levels of endogenously synthesized OA, like exogenously supplied excess OA, can induce an imbalance in hepatic nucleotide pools and can exert a promoting effect on hepatocarcinogenesis.

In vitro metabolism of aflatoxin B1 by normal and tumorous liver tissue from Thailand.

Liver tissues were obtained from 20 liver cancer patients from Thailand, an area where the incidence of this tumour is high and where exposure to aflatoxin occurs. The expression of hepatic cytochrome P450s (P450) and glutathione S-transferase (GST) was examined and this expression was compared to the in vitro metabolism of aflatoxin B1 (AFB1). There was a > 10-fold inter-individual variation in expression of the various P450s including CYP3A4 (57-fold), CYP2B6 (56-fold) and CYP2A6 (120-fold). Microsomal metabolism of AFB1 to AFB1 8,9-epoxide (as measured by AFB1 tris-diol formation) and aflatoxin Q1 (AFQ1), the major metabolite produced, was significantly correlated with CYP3A3/4 expression (P < 0.001) and, to a lesser extent, with CYP2B6 expression (P < 0.01). There was a significantly reduced expression of major P450 proteins in microsomes from liver tumours compared to microsomes from the paired normal liver when analysed by Western immunoblot analysis. The production of AFQ1 and AFB1 tris-diol was almost uniformly reduced in tumours, but interestingly, the production of AFP1 was significantly increased. The immunoreactive expression of the major human classes of cytosolic GSTs (alpha, mu and pi) was also analyzed in normal and tumorous liver tissue. The expression of GSTA (alpha) and GSTM (mu) class proteins was markedly decreased and GSTP (pi) increased in the majority of tumour cytosols compared to normal liver. The cytosolic GST activity (1-chloro-2,4-dinitrobenzene conjugation) was significantly lower in liver tumours compared to normal liver (193 +/- 149 versus 875 +/- 299 nmol/min/mg, P < 0.0001), as was glutathione peroxidase (GPx) activity (cumene hydroperoxide) (26 +/- 23 versus 70 +/- 26 nmol/min/mg respectively, P < 0.005). Ten out of 14 individuals (71%) were homozygous null when genotyped for GSTM1. There was no detectable conjugation of AFB1 8,9-epoxide to glutathione by cytosol either from tumorous or normal liver. Thus, capacity of human cytosols to conjugate reactive AFB1 metabolites to GSH resembled AFB1-sensitive species such as rat, trout and duck rather than resistant species such as mouse and hamster. These data indicate a strong capacity of multiple forms of human hepatic P450s to metabolize AFB1 to both the reactive intermediate AFB1 8,9-epoxide and the detoxification product AFQ1. These results suggest that in view of the lack of significant GST-mediated protection against AFB1 in human liver, variations in expression of hepatic P450, due either to genetic polymorphisms or to modulation by environmental factors, may be important determinants in the risk of liver cancer development in AFB1-exposed populations.