Strategies for Prevention of HCC

Transcription

1 Strategies for Prevention of HCC

2 Molecular Epidemiology Identify risk factors and outcome Biomarkers Carcinogen-macromolecular adducts Normal DNA sequence variants Mutations in target genes Measure in urine, serum or tissue Immunoassays GC/MS, LC/MS Florescence spectometry May 2nd, 2005 Megan McBee-BE.450 2

3 HCC Epidemiology Annual new cases ~600,000 ~600,000 annual deaths 80% burden in Asia and subsaharan Africa 300,000+ cases in People s Republic of China High risk areas early age of onset 20 s Low risk areas early age of onset 50 s May 2nd, 2005 Megan McBee-BE.450 3

4 HCC Epidemiology Main causes in high risk areas HBV infection Aflatoxins in diet Synergism leading to increased risk Impact on HCC incidence HBV vaccination aflatoxin exposure May 2nd, 2005 Megan McBee-BE.450 4

5 HCC Epidemiology: Aflatoxin Studies Taiwan 1 : BsAg+ males with HCC compared to control subjects R = 2.8 detectable vs. nondetectable aflatoxin metabolites R = 5.5 high vs. low urinary metabolite levels Shanghai 2 : relative risk for HCC with presence aflatoxin metabolites = Wang LY et al. Int J Cancer Sep 4;67(5): Ross RK et al. Lancet Apr 18;339(8799): May 2nd, 2005 Megan McBee-BE.450 5

6 Aflatoxins H Produced by fungi 1960 outbreak of Turkey X disease in UK Aspergillus flavus Common in corn, peanuts, fermented soy products H Cytochrome P450 Aflatoxin B 1 CH 3 H H CH 3 Figure by MIT CW. Active DNA-modifying agent May 2nd, 2005 Megan McBee-BE.450 6

7 HCC Prevention/Intervention Primary Vaccination Reduced contamination Secondary Pharmaceuticals Natural products May 2nd, 2005 Megan McBee-BE.450 7

8 HCC Prevention/Intervention Hepatitis B Virus Aflatoxin B 1 HBsAg (serum) vaccination chlorophyllin Insertional Mutagenesis Reactive Intermediates oltipraz, ITCs Aflatoxin-Mercapturic Acid (urine) 1762 T /1764 A Double Mutation (serum) X-Gene Mutations antioxidants Promutagenic DNA Lesions Aflatoxin-N 7 -guanine (urine) antiviral drugs Chronic Inflammation green tea polyphenols, CX-2 inhibitors, ITCs, vitamin K analogs, retinoids p53 Gene Mutations (G:T-T:A transversions) Selective Clonal Expansion and p53 Allelic Deletion 249 ser Mutations (serum) Cell Proliferation green tea polyphenols, CX-2 inhibitors, ITCs, vitamin K analogs, retinoids Chronic Hepatitis and/or Cirrhosis oltipraz Hepatocellular Carcinoma Figure by MIT CW. May 2nd, 2005 Megan McBee-BE.450 8

9 Primary Interventions HBV vaccination Taiwan HCC cases in 6-14 year olds Born = 0.70 Born = 0.57 Born = 0.36 Reduction of aflatoxins in food Chang MH et al. N Engl J Med Jun 26;336(26): May 2nd, 2005 Megan McBee-BE.450 9

10 ltipraz Secondary Intervention Chlorophyllin H 3 C C 2 H 5 H 3 C C 2 H 5 N N S S H 2 C=HC H 3 C N N Cu N N CH 3 H 2 C=HC C - Na + H 3 C N N Cu N N CH 3 H 3 C S CH 2 C - Na + H 3 C CH 2 CH 2 C - Na + CH 2 C - Na + H 3 C CH 2 CH 2 C - Na + Trisodium Copper Chlorin e 6 Disodium Copper Chlorin e 4 Isothiocyanates Polyphenols R H R R + R N C S H A C H B + H R R + H H H H R H H R + H + R + H H H May 2nd, 2005 Megan McBee-BE.450 Figures by MIT CW. 10

11 Secondary Intervention: ltipraz ltipraz Induces phase 2 enzymes Inhibits phase 1 enzymes Higher doses (500mg+) not more effective at induction or inhibition than lower doses (125mg and 250mg) May 2nd, 2005 Megan McBee-BE

12 Mechanism of ltipraz Source: Kensler,T. W. Chemoprevention by inducers of carcinogen detoxication enzymes. Environmental Health Perspective 105, Supplement 4 (1997): Reproduced with permission from Environmental Health Perspectives. May 2nd, 2005 Megan McBee-BE

13 Secondary Intervention: ltipraz Phase IIa intervention trial Feasibility of biomarker measurements Dose response Tolerance/effectiveness longer term exposure Chronic toxicity Source: Kensler, T. W., et al. "Chemoprevention of hepatocellular carcinoma in aflatoxin endemic areas." Gastroenterology 127, no. 5, Supplement 1 (2004): S May 2nd, 2005 Megan McBee-BE

14 Secondary Intervention: ltipraz Location: Dazin Township, Qidong, People s Republic of China Randomized, placebo-controlled, double blind 240 adults without history of chronic disease Detectable serum aflatoxin-albumin adducts 3 intervention groups 1) Placebo 2) 125mg once daily 3) 500mg once weekly Source: Kensler, T. W., et al. "Chemoprevention of hepatocellular carcinoma in aflatoxin endemic areas." Gastroenterology 127, no. 5, Supplement 1 (2004): S May 2nd, 2005 Megan McBee-BE

15 Secondary Intervention: ltipraz 500mg weekly after 1 month 51% decrease median levels aflatoxin M 1 excretion No effect on aflatoxin-mercapturic acid Inhibits activation 250mg daily after 1 month 2.6-fold increase in median levels of aflatoxinmercapturic acid Modest effect on aflatoxin M 1 levels Increase phase 2 conjugation Source: Kensler, T. W., et al. "Chemoprevention of hepatocellular carcinoma in aflatoxin endemic areas." Gastroenterology 127, no. 5, Supplement 1 (2004): S May 2nd, 2005 Megan McBee-BE

16 Secondary Intervention: ltipraz ngoing follow-up phase IIb trial Sustained expression enhancement of aflatoxin detoxification enzymes 250mg versus 500mg once weekly for 1 year Measuring multiple biomarkers for mechanisms of action May 2nd, 2005 Megan McBee-BE

17 Secondary Intervention: Chlorophyllin Mixture of sodium-copper salts of chlorophyll TC drug Wound healing accelerant Controls body, fecal and urinary odor In vitro and in vivo antimutagen in short-term genotoxicity assays May 2nd, 2005 Megan McBee-BE

18 Secondary Intervention: Chlorophyllin Complexes with aflatoxin B1 Reduction in bioavailability Needs molar excesses to carcinogen for efficacy In vitro inhibitor of cytochrome P450 enzymes Antioxidant-reduction in lipid peroxidation May 2nd, 2005 Megan McBee-BE

19 Secondary Intervention: Chlorophyllin Chemoprevention study in Qidong 180 healthy adults 100mg chlorophyllin or placebo 3-times daily for 4 months Endpoint of modulated aflatoxin-n7- guanine adducts in urine after 3 months Resulted in 55% decrease in median urinary adduct levels Source: Kensler, T. W., et al. "Chemoprevention of hepatocellular carcinoma in aflatoxin endemic areas." Gastroenterology 127, no. 5, Supplement 1 (2004): S May 2nd, 2005 Megan McBee-BE

20 Secondary Intervention: Isothiocynates Source: Family Cruciferae (mustards), Genus Brassica (cauliflower, Brussels sprouts, broccoli, cabbage) Lower cancer rates in individuals consuming high levels of yellow and green vegetables Isothiocyanates Particularly glucosinolate precursors Sulforaphane induces phase 2 enzymes in rats (glucoraphanin is precursor) May 2nd, 2005 Megan McBee-BE

21 Secondary Intervention: Source: Green tea Polyphenols Inverse association of consumption versus risk and development of cancer Green tea-derived polyphenols (ongoing study) Reduce aflatoxin M 2 excretion Increase aflatoxin-mercapturic acid excretion Reduced 8-oxo-deoxyguanosine May 2nd, 2005 Megan McBee-BE

22 utlook: Primary Interventions HBV vaccination nly benefits younger generations Vertical transmission not prevented Reduced food contamination Requires infrastructure for production, processing and distribution Monitoring mycotoxins $$ Not feasible in developing countries May 2nd, 2005 Megan McBee-BE

23 utlook: Pharmaceutical Chemoprevention Not practical for populations at highest risk SE Asia, China, Africa First-generation (oltipraz) expensive 2nd and 3rd generation dithiolethiones Cheaper 10-fold increase in potency over oltipraz ngoing safety evaluations Long-term costs potentially high, chronic treatment May 2nd, 2005 Megan McBee-BE

24 utlook: Natural Products Practical for populations at highest risk SE Asia, China, Africa Inexpensive, diet-based Long-term compliance better Immediate impact May 2nd, 2005 Megan McBee-BE

25 Potential Impact Reduction of aflatoxin-n7- guanine Reduced risk HCC in animals Increased latency period Decreased aflatoxin exposure in Bejing correlated with later onset of HCC Image removed due to copyright reasons. Source: Kensler, T.W., et al. Chemoprevention of hepatocellular carcinoma in aflatoxin endemic areas. Gastroenterology Review 127, no. 5, Supplement 1 (2004): S May 2nd, 2005 Megan McBee-BE

26 Questions? May 2nd, 2005 Megan McBee-BE