Phytochemcials in Cancer Prevention - PowerPoint Presentation

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Phytochemcials in Cancer Prevention

Michael J. Wargovich, Ph.D.

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What Is Chemoprevention?

The science of trying to apply natural and synthetic compounds to interfere with the earliest stages of carcinogenesis, before invasive cancer appears

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The Ideal Chemopreventive Agent

Is effectiveEasily administeredPreferably once/twice dayLittle or ideally no toxicityAffordable

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Mechanisms of Chemoprevention

Antioxidants: defense against radicalsPhase 1 enzyme inducersPhase 2

enzyme inducers

Anti-proliferative

agents

Anti-hormonal compoundsDisruption

of mutational gain or loss of functionEpigenetic effects

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AntioxidantsOxygen is actually a very toxic substance

Antioxidants are the first line defense mechanism against oxidative damage in plantsFruits and vegetables are loaded with antioxidant chemicals

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Total Daily Intake of Antioxidants

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OH

OH

Anthocyanidin

e.g.

cyanidin

major constituents of dark

red fruit berries e.g. raspberries

+

OH

HO

OH

HO

OH

OH

O

OH

O

OH

OH

O

OH

O

HO

OH

Flavonol

e.g

.

quercetin

onion, cranberry, red apple

many fruit and vegetables

OH

OH

Hydroxycinnamate

e.g.

caffeic

acid

most fruit especially tomato, apple

some vegetables e.g. egg plant

grains

COOH

OH

OH

OH

HO

OH

O

Flavanol

e.g

.

epicatechin

red wine, green tea,

as

procyanidins

in apple, chocolate

Flavanone

e.g.

hesperetin

Citrus fruit, orange

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Green TeaEpidemiologic studies support a protective effect for

green tea but not black tea in prevention of certain cancersAnimal studies are highly supportive of a preventive effect of green tea, GTP

, and purified polyphenols, especially

EGCG

against certain cancers

Camellia sinensis

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9

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Evidence for Tea Drinking and Prevention of Human Cancer

Ecological Studies

Cohort Studies

Case-Control Studies

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BioflavonoidsNaturally occurring chemicals present in many fruits and vegetables

Major flavonoids in onion are quercetin and its glycoside, rutinCan reach appreciable levels in onions but tea also is a major source

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Bioflavonoids and Reduced Risk for Heart Disease

Quercetin inhibits oxidation of LDL cholesterolInhibits development of fatty streaks in animals

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Agents That Influence Drug Metabolism

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Surh et al Nat Reviews 3:2003

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Garlic

Consumption in China and Italy linked to lower gastric cancer risk Sulfur compounds inhibit cancers of colon, breast, esophagus, lung, skin

Primarily acts through modulation of Phase 1 ( activation) and Phase 2 (detoxification) enzymes

Allium sativum

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Organosulfur Compounds in GarlicMember of the plant genus

AlliumOver 20 different compounds in garlic are being tested for cancer inhibition.Diallyl sulfide was the first organosulfur compound known to inhibit experimentally-induced cancer.Proposed mechanisms of chemoprotection lie in modification of carcinogen metabolism and/or detoxification.

Alliin

Lipophilic compounds

diallyl sulfide

diallyl disulfide

methyl propyl sulfide

dipropyl disulfide

dimethyl trisulfide

methyl propyl trisulfide

methyl propyl thiosulfinate

Water soluble compounds

L-cysteine

S-allyl-l-cysteine

S-methyl-l-cysteine

L-methionine

Allicin

Allinase

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CYP2E1 and Colon Cancer

Dimethylhydrazine (DMH) Model

CH

3

-NH-NH-CH

3

1,2-Dimethylhydrazine

CH

3

-N=N-CH

3

azomethane

CH

3

-N=N-CH

3

azoxymethane

CH

3

-N=N-CH

2

OH

methylazoxymethanol

O

CH

3

-N N

methyldiazonium

LIVER

H

3

C

+

N

2

COLON

Spontaneous

breakdown

CYP2E1

CYP2E1

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Cyp2e1One subset of many cytochromes P450

Main task is to activate compounds; eliminate them from the bodyThis enzymes metabolizes many small molecular weight compoundsEthanol, nitrosamines, hydrazines

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Typical Chemoprevention Assays in Rodents

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Chemopreventive activity of oil-

soluble OSCs in ACF assay

(

M. Wargovich, 1997

)

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Antiproliferative or Growth Suppressing Agents:Modulation of Cell Signaling

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COX Inhibitors Reduce Colorectal Carcinogenesis – Observational Data

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How Do NSAIDs Work?Aspirin transfers acetyl group to serine on the cyclooxygenase enzyme, blocking its affinity for arachidonic acid

All other NSAIDs are competitive inhibitors of the COX enzymes

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BIOLOGICAL ROLE OF PROSTANOIDS

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Inflammation and Cancer

Chronic, clinically invisible, unresolved inflammation may create a very high risk for common cancersTumors corrupt the inflammatory pathway to survive

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A model of chronic inflammationsetting a threshold for cancer

Chronic

Inflammation

Esophagitis

Gastritis

Colitis

Pancreatitis

Hepatitis

Replacement

hyperproliferation

Mutation

Tumor

ROS/RNS

ROS/RNS

Cell damage

Promotion

Initiation



apoptosis



angiogenesis

Growth

advantage

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Multistage Colon Carcinogenesis

APC

mutation

COX-2

Overexpression

K-ras

mutation

p53

mutation

Loss of 18q

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NSAIDs Inhibit ACFs in the Colon

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NSAIDS, COX Specificity and Chemoprevention

COX 1

COX 2

100% Indomethacin 0%

Sulindac

Piroxicam

Diclofenac

Naproxen Meclofenamate Etodolac

Nimsulide Celecoxib 0% 100%

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Toxicity of NSAIDsIbuprofen

DiclofenacNaproxenKetoprofenIndomethacinPiroxicam

- +

+/- +

+/- +

+ +++++ ++++++ +++

Compound Toxicity* Inhibit ACF?

* Clinical manifestations: Colitis, perforation, fistulae, GI bleeding

Peptic and small bowel ulcers, strictures

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* P < 0.05; n=12/group

Vehicle

150

500

1500

50

0

5

10

15

20

25

30

35

Late treatment

(days 55-80)

Celecoxib

Piroxicam

*

(mg/kg diet)

*

Celecoxib Inhibits Tumor Multiplicity in

the MIN Mouse Model

Multiplicity (tumors/animal)

10

15

20

25

30

35

Vehicle

500

1500

50

0

5

Early treatment

(days 30-80)

Celecoxib

Piroxicam

(mg/kg diet)

*

*

Jacoby et al: Cancer Res 60:5040-4, 2000

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Effect of COX-2 Selective Inhibition on Colorectal Adenomas in Patients with FAP

Steinbach et al, NEJM, 2000

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Plant-based NSAIDS...

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Herbal NSAIDSOveruse could potentially result in bleeding, prolonged platelet aggregation, and ulceration

Combined use might reduce the need for high strength NSAIDsCould help in long term chemoprevention trials for colon and breast cancer

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Are there plant-based NSAIDS?

If so, the source should:Have anti-inflammatory effectsBe available for oral useBe safe

Efficacious

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Resveratrol (Red Grapes)

A phytoalexin in red grapesInhibits cell transformation in cultured tumor cells

Inhibits cell proliferation in cells in culture and in tumors grown in mice

Inhibits mammary cancer in rats

Induces apoptosis

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Epidemiological Studies of

Tea and Cancer

Ecologic, case-control and cohort studies have been performed.

Studies are difficult to compare. No standard method of tea intake

Several cancer sites investigated:

Stomach, colon, esophagus, prostate, lung

Duration of tea consumption is important

Earlier in life, stronger the effect

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Results of Animal Studies With Tea

 

 

 

Organ Site

Protective

Not Protective

Skin

13

5

Oral

2

0

Esophagus

3

1

(Fore)stomach

5

0

Intestine/Colon

10

3

Liver

7

0

Bladder

1

0

Prostate

1

0

Breast

6

3

Lung

10

1

Yang CS. Personal Communication

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How Do Tea

Polyhenols Prevent Colon Cancer?

By inhibiting cell proliferation and inducing apoptosis?

Yes.

By influence on cell signaling pathways?

Yes.

By influence on nuclear transcription factors?

Yes.By inhibition of prostanoid biosynthesis? Yes.

By epigenetic mechanisms?Our current research

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Anti-proliferation effects of EGCG

48 hr

72 hr

EGCG µM

EGCG µM

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Jumping to Mouse Models:

Apc

Min

Mouse Is Not Perfect

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Apc

min/+ & AOM mouse model

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*

*

AOM Treatment Increases Colonic Tumors in the

Apc

Min

+/

Model and Continual Exposure to Oral Green Tea Suppresses Tumorigenesis

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*

Green tea

suppresses tumorigenesis

early

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Intestinal Medium RXR alpha negative Foci

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Intestinal Large

RXRa negative Foci

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Me

Me

Me

Me

Me

Me

not transcribed

X

gene transcribed

Me

Me

Me

HDAC

HDAC

HDAC

Gene

Silencing

methylation

histone deacetylation

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Retinoid Receptors and Cancer

Loss

associated with increased tumorigenesis in:

Head and neck

Breast

Oral

ColonRARβ often methylated

Control cell proliferation

Induce apoptosis

Induce differentiation

Uncontrolled cell proliferation

Block apoptosis

Inhibit differentiation

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RXR-Retinoid X receptors

Mediate activity of retinoids along with RARs

Dysregulated in breast, lung, prostate cancers

CpG islands in the RXR promoter

Hypermethylation

 RXR expression and heterodimer partners (RAR, VITD, PPAR, THR

Makes this an important nexus for tumors to knock out

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*

Number of RXR alpha negative foci decreases

in the presence of green tea

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S+W

AOM+W

AOM+GT

S+GT

RXR

α

Cyclin D1

S+W

AOM+W

AOM+GT

S+GT

Control

 actin

 actin

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RXR

Heterodimerizes

With Many Key Regulatory Transcription Factors

VDR

RAR

PXR

PPAR

THR

FXR

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Global Collaborations

Ethnobotanicals

Wargovich Laboratory

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Tropical Fruits from Colombia

Collaboration with Pontificia Universidad Javeriania (Bogota)

Examine extracts of native fruits for cancer prevention

Many related to pomegranates

Lulo, curuba, borojo, granadilla

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The flowers, leaves, and seeds of the Neem plant

From India:

Azadirachta

indica

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What Research Is Going On with Neem?

Natural products may make cancer therapy work better/more safelySupercritical extracts of the neem tree (Azadirachta

indica

) are being tested to alleviate a major side effect of cancer therapy: oral

mucositisStudies with the UTHSCSA Dental School to evaluate neem for prevention of oral cancer

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Radiation/ Chemotherapy

Healing

Ulceration/

Infection

Initiation

Inflammation



ROS

Activation of NF-B

 Proinflammatory cytokines

Apoptosis

Tissue injury

Infection

NEEM MOUTHWASH

Anti-oxidant

Anti-inflammatory

Anti-ulcer

Anti-microbial

Azadirachta

indica

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Fingerprinting profile of Neem from 3 runs

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Cyclin D1 is Down-regulated after 48 hrs Neem Treatment in HCT116 Cells

34-36 KDa

37

KDa

Cyclin

D1

GAPDHV NeemV 5FU

12.5+5FU18+5FU

5FU 505FU 100

12.5 µg/ml18µg/ml

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West African Traditional Medicinal Plants With Anti-inflammatory Activity

Common Name

Botanical Name

Medicinal Use

How Used?

Neem tree

Azadirachta indica

Reduce fever

Decoction of bark

Baobob tree

Adamsonia

digitata

GI pain; fever; rheumatic pain

Decoction of the leaves

African basil

Ocimum viridae

Common analgesic for fever

Syrup made of water extract of leaves

Senegal mahoghany

Khaya sengalensis

Joint pain and menstrual pain

Syrup made of conc. extract of stem & bark

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[M+H]

+

[2M+H]

+

MS spectrum of K-4

:

3,7 -dideaetylkhivorin

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Natural Product Development Pipeline

Sustainable

Reliable

Reproducible

MeOH

EtOH

H

2

0scC02

HPLCLC-MS

Cell lines

Growth

Apoptosis

Motility

Microarrays

Next Gen

Seq

Inflammasome

Epigenomics

1

 tumor

models

Xenografts

Phase 1

Biofractionization

driven analysis may miss the fact that

complex mixtures may act synergistically with better

efficacy than isolated compounds!!! Complex mixtures

are what we consume!

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Chemoprevention Continuum

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With Thanks to:

Wargovich Lab

Jay Morris, PhD

Dina Brown PhD

Becky Weber, MD, PhD

Keya Mukhopadhyay, PhDApril Cabang

Yuan FangRoxanne KhoogarByung Chang Kim, MD

NIH

R01 CA 96694R21 CA 158530Kronkosky Foundation

Lichtenstein FoundationKerr Foundation