Ross G. Cameron

The sequential analysis of cancer development.

Publisher Summary This chapter reviews the sequence of cellular and other changes during cancer development in selected sites in experimental animals and in humans. It highlights the similarities and differences among the carcinogenic processes and discusses the evident generalities and working hypotheses derived from the analyses. It also discusses some perspective concerning the possible relationship of carcinogenesis to other types of chronic pathological processes such as some forms of adaptation and evolution. Major emphasis is given to three sites—namely, skin, liver, and breast. Several other sites or types of neoplasms are also discussed in the chapter, including urinary bladder, brain, kidney, uterine cervix, and foreign-body sarcoma. It focuses on the development of cancer with chemicals in experimental animals and in humans. To date, the major evidence for a beneficial role for new cell populations occurring during the preneoplastic phase of carcinogenesis concerns the liver. However, it seems appropriate to explore other systems from this point of view. In other organs or tissues, appropriate physiological or environmental factors should be sought as possible influences on early carcinogen-induced new cell populations. These influences might well constitute naturally occurring “promoting” environments in at least some carcinogenic process.

Iron-chelation therapy with oral deferiprone in patients with thalassemia major

BACKGROUND To determine whether the orally active iron chelator deferiprone (1,2-dimethyl-3-hydroxy-pyridin-4-one) is efficacious in the treatment of iron overload in patients with thalassemia major, we conducted a prospective trial of deferiprone in 21 patients unable or unwilling to use standard chelation therapy with parenteral deferoxamine. METHODS Hepatic iron stores were determined yearly by chemical analysis of liver-biopsy specimens or magnetic-susceptibility measurements. Detailed clinical and laboratory studies were used to monitor safety and compliance. RESULTS The patients received deferiprone therapy for a mean (+/-SE) of 3.1 +/- 0.3 years. Ten patients in whom previous chelation therapy with deferoxamine had been ineffective had initial hepatic iron concentrations of at least 80 mumol per gram of liver, wet weight -- values associated with complications of iron overload. Hepatic iron concentrations decreased in all 10 patients, from 125.3 +/- 11.5 to 60.3 +/- 9.6 mumol per gram (P < 0.005), with values that were less than 80 mumol per gram in 8 of the 10 patients (P < 0.005). In all 11 patients in whom deferoxamine therapy had previously been effective, deferiprone maintained hepatic iron concentrations below 80 mumol of iron per gram. CONCLUSIONS Oral deferiprone induces sustained decreases in body iron to concentrations compatible with the avoidance of complications from iron overload. The risk of agranulocytosis associated with deferiprone may restrict its administration to patients who are unable or unwilling to use deferoxamine.

Syncytial giant-cell hepatitis. Sporadic hepatitis with distinctive pathological features, a severe clinical course, and paramyxoviral features

BACKGROUND AND METHODS We describe a new form of hepatitis, occurring in 10 patients over a period of six years, characterized clinically by manifestations of severe hepatitis, histologically by large syncytial giant hepatocytes, and ultrastructurally by intracytoplasmic structures consistent with paramyxoviral nucleocapsids. RESULTS The patients ranged in age from 5 months to 41 years. The tentative clinical diagnosis before biopsy was non-A, non-B hepatitis in five patients and autoimmune chronic active hepatitis in the others. Five patients underwent liver transplantation; the others died. The diagnosis of syncytial giant-cell hepatitis was established pathologically. The liver cords were replaced in all 10 patients by syncytial giant cells with up to 30 nuclei. In 8 of the 10 the cytoplasm contained pleomorphic particles of 150 to 250 microns, filamentous strands, and particles of 14 to 17 nm with peripherally disposed spikes resembling paramyxoviral nucleocapsids. Structures resembling degenerated forms were found in the other two patients. One of two chimpanzees injected with a liver homogenate from the index patient had an increase in the titer of paramyxoviral antibodies, probably an anamnestic reaction to previous paramyxoviral infection, suggesting that a paramyxoviral antigen but not viable virus was present in the liver homogenate. CONCLUSIONS Although further virologic studies will be required for precise classification, we believe that paramyxoviruses should be considered in patients with severe sporadic hepatitis.

Biochemical and clinical response of fulminant viral hepatitis to administration of prostaglandin E. A preliminary report.

The effect of PG on patients with fulminant and subfulminant viral hepatitis (FHF) was studied. 17 patients presented with FHF secondary to hepatitis A (n = 3), hepatitis B (n = 6), and non-A, non-B (NANB) hepatitis (n = 8). 14 of the 17 patients had stage III or IV hepatic encephalopathy (HE). At presentation the mean aspartate transaminase (AST) was 1,844 +/- 1,246 U/liter, bilirubin 232 +/- 135 mumol/liter, prothrombin time (PT) 34 +/- 18, partial thromboplastin time (PTT) 73 +/- 26 s, and coagulation Factors V and VII 8 +/- 4 and 9 +/- 5%, respectively. Intravenous PGE1 was initiated 24-48 h later after a rise in AST (2,195 +/- 1,810), bilirubin (341 +/- 148), PT (36 +/- 15), and PTT (75 +/- 18). 12 of 17 responded rapidly with a decrease in AST from 1,540 +/- 833 to 188 +/- 324 U/liter. Improvement in hepatic synthetic function was indicated by a decrease in PT from 27 +/- 7 to 12 +/- 1 s and PTT from 61 +/- 10 to 31 +/- 2 s, and an increase in Factor V from 9 +/- 4 to 69 +/- 18% and Factor VII from 11 +/- 5 to 71 +/- 20%. Five responders with NANB hepatitis relapsed upon discontinuation of therapy, with recurrence of HE and increases in AST and PT, and improvement was observed upon retreatment. After 4 wk of intravenous therapy oral PGE2 was substituted. Two patients with NANB hepatitis recovered completely and remained in remission 6 and 12 mo after cessation of therapy. Two additional patients continued in remission after 2 and 6 mo of PGE2. No relapses were seen in the patients with hepatitis A virus and hepatitis B virus infection. Liver biopsies in all 12 surviving patients returned to normal. In the five nonresponders an improvement in hepatic function was indicated by a fall in AST (3,767 +/- 2,611 to 2,142 +/- 2,040 U/liter), PT (52 +/- 25 to 33 +/- 18 s), and PTT (103 +/- 29 to 77 +/- 44 s), but all deteriorated and died of cerebral edema (n = 3) or underwent liver transplantation (n = 2). These results suggest efficacy of PGE for FHF, and further investigation is warranted.

Fulminant Hepatitis as a Consequence of Reactivation of Hepatitis B Virus Infection after Discontinuation of Low-Dose Methotrexate Therapy

Excerpt Development of liver disease in chronic hepatitis B virus carriers depends on the interplay between viral products and the host immune system. Although it is generally believed that the vir...

Inducers of cytochrome P450 2E1 enhance methotrexate-induced hepatocytotoxicity

OBJECTIVES To study the effect of cytochrome P450 2E1-inducers on methotrexate (MTX)-induced cytotoxicity in human hepatocytes, and investigate the role of silymarin in preventing this toxicity. DESIGN AND METHODS Cells were exposed to MTX in the presence of either ethanol (EtOH) or acetaminophen (APAP), or either combined with silymarin (S). Apoptosis and necrosis were measured by analyzing 6000 cells/sample using transmission electron microscopy, while cytokine release and apoptosis were quantitated by ELISA. Cytokine expression was measured by RT-PCR. Gluthatione (GSH) content was determined in cytosolic (c) and mitochondrial (m) fractions. RESULTS MTX+EtOH and MTX+APAP increased MTX cytotoxicity 2.9-fold and 1.9-fold, respectively. S abolished this toxicity. MTX + EtOH increased the release of IL 6, IL 8 and TNF alpha by 1.0, 1.2, and 1.1 times, respectively. Cytokine expression was upregulated versus control for IL 6 (22%), IL 8 (38%), and TNF alpha (29%). Addition of 0.5 mmol/L S downregulated TNF alpha expression and reduced cytokine release. TNF alpha increased cytotoxicity by 22%, while anti-TNFalpha antibody eradicated it. MTX+EtOH depleted 45% mGSH (0 < 0.001) while S replenished it to 87% (p < 0.001), when both were compared to control levels. CONCLUSIONS Cytochrome P450 2E1-inducers contribute to increase oxidative stress in MTX-exposed cells by increasing TNF alpha and depleting both cGSH and mGSH. This enhances MTX-cytotoxicity and promotes apoptosis.

A pilot study of ribavirin therapy for recurrent hepatitis C virus infection after liver transplantation.

Ribavirin is a guanosine analogue that normalizes serum liver enzymes in most nontransplant patients with chronic hepatitis C virus (HCV) infection. We conducted an uncontrolled pilot study of ribavirin in 9 liver transplantation recipients that had persistently elevated liver enzymes, active hepatitis by liver biopsy, and HCV RNA in serum by polymerase chain reaction. Ribavirin was given orally at dosages of 800-1200 mg per day for 3 mo. All 9 patients promptly responded to ribavirin: mean (+/- SD) ALT decreased from 392 +/- 377 IU/L immediately before treatment to 199 +/- 185 and 68 +/- 37 IU/L after 1 and 12 weeks of treatment, respectively, complete normalization of enzymes occurred in 4 patients. None of the patients cleared the virus from their serum during therapy, and biochemical relapse occurred in all patients 4 +/- 4.2 weeks after cessation of therapy. The hepatitis activity index of liver biopsy specimens obtained before and at the cessation of therapy was similar. Ribavirin treatment was resumed in 4 patients because of increasing fatigue (2 patients), rising bilirubin (3), or increasing necroinflammation on liver biopsy (2); the biochemical response to the second course of therapy was similar to the first course in all 4 patients. Ribavirin caused reversible hemolysis in all patients, including symptomatic anemia in 3 patients that resolved after reduction of drug dosage. These results suggest that ribavirin may be of benefit in the treatment of HCV infection after liver transplantation. Further studies are needed to determine the optimal dosage and duration of therapy.

Overexpression of cytochrome P-450 isoforms involved in aflatoxin B1 bioactivation in human liver with cirrhosis and hepatitis.

Studies were carried out to test the hypothesis that inflammatory liver disease increases the expression of specific cytochrome P-450 isoenzymes involved in aflatoxin B1 (AFB) activation. The immunohistochemical expression and localization of various human cytochrome P-450 isoforms, including CYP2A6, CYP1A2, CYP3A4, and CYP2B1, were examined in normal human liver and liver with hepatitis and cirrhosis. The constitutive expression of CYP3A4 in normal liver showed a characteristic pattern of distribution in centrilobular hepatocytes, whereas CYP1A2, CYP2A6, and CYP2B1 1 were expressed uniformly throughout the liver acinus. In sections of liver infected with hepatitis B virus (HBV) or hepatitis C virus (HCV), the expression of CYP2A6 was markedly increased in hepatocytes immediately adjacent to areas of fibrosis and inflammation. CYP3A4 and CYP2B 1 were induced to a lesser degree, and expression of CYP1A2 was unaffected. In HBV-infected liver, double immunostaining revealed that overexpression of CYP2A6 occurred in hepatocytes expressing the HBV core antigen. In HCV-infected liver, CYP2A6, CYP3A4, and CYP2B 1 were overexpressed in hepatocytes with hemosiderin pigmentation. These results suggest that alterations in phenotypic expression of specific P-450 isoenzymes in hepatocytes associated with hepatic inflammation and cirrhosis might increase susceptibility to AFB genotoxicity.

CYP2E1-mediated modulation of valproic acid-induced hepatocytotoxicity

OBJECTIVES To determine the cytotoxicity of valproic acid (VPA) and its metabolite, 4-ene-valproic acid (4-ene-VPA) in human hepatoblastoma cells (Hep G2), and to study the modulatory effect of cytochrome P450 2E1 induction in this model. METHODS Cells were exposed to VPA or 4-ene-VPA in the presence of either ethanol (EtOH), or EtOH combined with disulphiram (DS). Some cells were exposed to alpha-fluoro-VPA or to alpha-fluoro-4-ene-VPA in the absence of CYP2E1 inducers. Apoptosis and necrosis were measured by analyzing 6000 cells per sample using transmission electron microscopy, while cytokine release and apoptosis were quantitated by ELISA. RESULTS VPA + EtOH increased VPA cytotoxicity. 4-ene-VPA + EtOH significantly increased toxicity, while DS + EtOH significantly reduced this toxicity. Alpha-fluorinated analogues reduced cytotoxicity compared to the corresponding VPA compounds. Neither VPA nor alpha-fluorinated VPA increased the release of IL-6 or TNF-alpha in media. A significant increase in the release of TNF-alpha was observed in cells exposed to 4-ene-VPA that further increased with EtOH exposure. CONCLUSIONS Cells exposed to 4-ene-VPA experience greater cytotoxicity than those treated with VPA. Cytochrome P450 2E1 inducers enhance toxicity in VPA-exposed cells, while alpha-fluorination of VPA diminishes cytotoxicity by directly interfering with the beta-oxidation of the 4-ene-VPA metabolite.

Ethanol-induced apoptosis in vitro

Objectives: The aim is to study the apoptotic process in a human hepatocyte model for ethanol (EtOH)-induced apoptosis. Design and methods: Normal human primary hepatocytes (HPH) and Hep G2 cells were exposed to increasing EtOH. 6000 cells/sample were analyzed by transmission electron microscopy. Results: Apoptotic cells were observed (mmol/L EtOH): 40: 6 ± 0.5%, 60: 13 ± 2% (p < 0.05), 80: 26 ± 1% (p < 0.001) (vs. control). Two consecutive doses of 80 mmol/L for 24 h each additionally increased apoptosis 55 ± 3% (p < 0.0001 vs. control and p < 0.001 vs. single dose). In response to this exposure, there is a stronger apoptotic activity in HPH when compared to Hep G2 (p < 0.05). Conclusions: In vitro, EtOH-induced apoptosis is regulated by dose level and the frequency of exposure.