10 24 2006 Oncology Hpv And Cancer

HPV and cervical cancer 林雅雯 分機 18910 Department of Microbiology and Immunology National Defense Medical Center

Tumor Viruses • • • • •

Retrovirus Herpesvirus Hepatitis virus Human papillomavirus ……….

Tumor viruses-retrovirus • Retrovirus – ssRNA – 1911 Chicken sarcoma – 1970 Reverse transcriptase – 1976 Proto-oncogens > 60 – 1980s HTLV-1: T cell lymphoma/leukemia

Virion Structure Lipid Envelope

Nucleic Acid

Protein Capsid Virion Associated Polymerase

Spike Projections

Virion Components • Protein – – – –

Structural proteins Membrane proteins Receptor recognition Enzymes

• Genomic nucleic Acid – DNA – RNA

• Lipid envelope – Plasma membrane – Paramyxoviruses – Nuclear membrane – Herpes viruses – Golgi membrane - Bunyaviruses

Virus replication Maturation

Virion attachment to cellular receptors Uncoating

Release Budding Insertion of virus proteins into membrane Genomic nucleic acid synthesis

Virion Assembly

Newly synthesised virus proteins

Replication of Genomic nucleic acid

Protein Synthesis mRNA synthesis

Baltimore Classification of Viruses Grou p

Gen om e

1

dsDNA

2

ssDNA

3

dsRNA

4

+ve ssRNA

dsRNA

5

-ve ssRNA

dsRNA

6

ssRNA

7

Repl ic atio n dsDNA

Ex am ple mRNA

ssDNA

dsDNA dsRNA

Herpes simplex virus

mRNA mRNA

Parvovirus Reovirus

+ve ssRNA [Acts as mRNA] Enterovirus -ve ssRNA

mRNA

Influenza A virus

dsDNA

mRNA

Retrovirus (e.g. HIV)

intact dsDNA

mRNA

Hepatitis B virus

ssRNA

Nicked dsDNA nicked dsDNA RNA

Tumor Viruses For most viruses: Replication

Lysis virions

Progeny

Lytic Life Cycle Genome

all viral proteins

Tumor Viruses Virus

Latent Life Cycle

Cell

Integration (usually)

Transformation

Some virus-specific proteins expressed - No mature virus Viral structural proteins are not expressed Sometimes latency may terminate – cell must be infected by complete virus Changes in the properties of host cell - TRANSFORMATION

Tumor Viruses Transformation: • Loss of growth control

• Reduced adhesion • Motility • Invasion • Ability to form tumors - viral genes interfere with control of cell replication • Transformed cells frequently exhibit chromosomal aberrations

TRANSFORMATION Both DNA and RNA tumor viruses can transform cells Integration occurs (usually) Similar mechanisms

VIRAL TRANSFORMATION The changes in the biological functions of a cell that result from REGULATION of the cell’s metabolism by viral genes and that confer on the infected cell certain properties characteristic of NEOPLASIA These changes often result from the integration of the viral genome into the host cell DNA

Two Major Classes of Tumor Viruses DNA Tumor Viruses DNA viral genome DNA-dependent DNA polymerase (Host or viral)

Host RNA polymerase

Viral mRNA

Viral protein

RNA Tumor Viruses Viral RNA genome Reverse transcriptase (Virus-encoded)

Viral DNA genome (integrated) IMPORTANT

DNA-dependent RNA polymerase (Host RNA pol II)

Viral genomic RNA Splicing (Host splicing enzymes)

messenger RNA

viral protein

Virus

Important: Use HOST RNA polymerase to make its genome An enzyme that normally makes mRNA

DNA Tumor Viruses DNA genome

mRNA

Host RNA polymerase II

Host enzymes

protein

virus OR TRANSFORMATION In transformation usually only EARLY functions are expressed

DNA Tumor Viruses In Human Cancer Papilloma Viruses • cause natural cancers in animals • cause benign warts • ubiquitous • epitheliotropic - most human tumors are malignancies of epithelial cells

DNA Tumor Viruses In Human Cancer Papilloma Viruses • Epidermodysplasia verruciformis wart

malignant squamous cell carcinoma

DNA Tumor Viruses In Human Cancer ONCOGENE A gene that codes for a protein that potentially can transform a normal cell into a malignant cell An oncogene may be transmitted by a virus in which case it is known as a VIRAL ONCOGENE

v-onc

RNA Tumor Viruses RNA Genome - Retroviruses RNA-dependent DNA Polymerase encoded by virus REVERSE TRANSCRIPTASE RNA genome Reverse transcriptase

virus

DNA genome Integrase

virus

Integrates Host RNA polymerase II

RNA genome

host

RNA Tumor Viruses Viral Oncogene V-onc

Cellular Proto-oncogene C-onc

RNA Tumor Viruses Proto-oncogene A cellular (host) gene that is homologous with a similar gene that is found in a transforming virus A cellular oncogene can only induce transformation after • mutation • some other change in the cell’s genome

RNA Tumor Viruses The discovery of the acutely transforming retroviruses that contain v-oncs explains how cancers may arise as a result of infection

These viruses cause rapid cancer in animals in the laboratory

RNA Tumor Viruses In contrast: Chronically transforming retroviruses cause tumors inefficiently after prolonged period of time Avian Leukosis Virus (causes lymphomas)

R R

U5

GAG

POL

ENV

U3

No oncogene! – How does it cause a tumor?

RNA Tumor Viruses ALV can integrate into the host cell genome at MANY locations but in tumor it is always at the SAME site (or restricted number of sites) Suggests tumor arose from one cell • Something must be important about this site for transformation • Crucial event must be rare

RNA Tumor Viruses What is special about this site? Myelocytoma tumors from several birds all have the oncogene close to this site

It is close to C-myc! Oncogenesis by promotor insertion

RNA Tumor Viruses

Could C-oncs be involved in NON-VIRAL cancers?

RNA Tumor Viruses What do oncogenes encode? Proteins that are involved in growth control and differentiation

Growth factors Growth factor receptors Signal transduction proteins Transcription factors

DNA Tumor Viruses Herpes

myb

mos myc

Genes can be assigned to sites on specific chromosomes mos and myc : chromosome 8

fe s

fes: chromosome 15

Cancers often result from gene Burkitt’s translocations

Lymphoma

8:14 translocation Break in chromosome 14 at q32 myc

Acute myelocytic leukemia 7:15 9:18 11:15:17

Oncogenesis by rearrangement Tumor

c-onc

new promotor

Burkitt’s lymphoma

myc (8)

Ig heavy (8 to 14) Ig light (8 to 2)

B-cell chronic lymphocytic

bcl-1

Ig heavy (11 to 14)

leukemia

bcl-2

Ig heavy (18 to 14)

T cell chronic lymphocytic

tcl-1

leukemia T cell chronic lymphocytic leukemia

T cell receptor (14 inversion)

myc

T cell receptor (8 to 14)

Oncogenes Mutations in a proto-oncogene are dominant “gain of function” mutations

Anti-Oncogenes • Loss of function mutations • Retinoblastoma • p53

Proto-oncogenes Heterozygote

Dominant mutations Homozygote

Allele 1

Allele 2

Allele 1

Allele

Normal

Mutant

Mutant

Mutant

2

Binds under special circumstance s

Mutant always binds

Always binds

Function gained

Mutant always binds

Mutant always binds Always binds

Function gained

Anti-Oncogenes Recessive mutations Mutation Rb Gene

Mutant Rb

growth Mutant Rb

Mutant Rb

Rb Rb protein

Heterozygote

Rb Binds and controls cell cycle Turns off DNA replication

Homozygote Function lost No binding - Growth continues

Anti-Oncogenes Retinoblastoma gene has normal regulatory function in many cells

Involved in Retinoblastoma Lung carcinomas Breast carcinomas

Anti-Oncogenes P53 Inactivated by • deletion • point mutation In a series of colorectal cancers all showed: • Allele 1: partial or complete deletion • Allele 2: Point mutation

DNA Tumor Viruses Oncogenes • Adenovirus

E1A region 2

• SV 40

Large T

• Polyoma

Large T

• BK virus

Large T

• Lymphotropic virus

Large T

• Human papilloma Virus-16

E7

All have a sequence in common Mutations in this region abolish transformation capacity

Anti-Oncogenes Retinoblastoma Rb Gene

Rb protein

Rb

Adenovirus E1A

105kD Rb

Rb Stops replication

Cell cycle continues

Anti-Oncogenes p53 P53 gene

P53 gene Hepatitis C

P53

P53

P53

Papilloma P53

Papilloma proteolysis

DNA

Stops replication

P53 gene

replication

replication

Tumor virus-Human papillomaviruses Circular dsDNA ~8k bp ~100 types 8 genes

High risk HPV 31

HPV and Cervical cancer • 1974~1976 – postulating the role of HPV in cervical cancer

• 1976 – The role of HPV in Pap smear and mild dysplasia

• 1983 – The first HPV isolated from cervical cancer biopsy (HPV 16)

• 1984 – Isolation of HPV 18 from cervical cancer biopsy

• 1985 – Active E6/E7 in cervical cancer

• 1989 – The transforming properties of E6 and E7

HPV and Cervical cancer • 1987 – First epidemiologic study – High rate of infection in young women

• 1992 – A large-scale epidemiological study in Columbia and Spain that provides convincing evidence that high risk HPVs are the main risk factor for CC.

• 1995 – Prevalence of HPV in cervical cancer: a worldwide perspective

• 1995 – HPV 16 and 18 were defined as causative agents for cervical cancer by IARC

HPV and Cervical cancer • 1998 – The natural history of HPV infection – 14% per year, 44% in 3 years – Average clearance time 8 months

• 1999~2001 – Type-specific persistent infection is the major risk factor for cervical cancer

• 2000 – Viral load as a risk factor

• 2002 – The causal role of HPV in cervical cancer is beyond reasonable questioning

HPV pathogenesis

Oncogene (2003) 22, 5201–5207

The spectrum of cervical neoplasia

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Normal

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LSIL

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HSIL

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SCC

HPV pathogenesis- viral oncoproteins • E6-P53 • E7-Rb • E5-transmembrane proteins • E4 (?) • E2-+/- regulation of URR • L1 and L2

Cell cycle and P53/Rb

High-risk HPV E6 promotes p53 degradation via the ubiquitin pathway

Model for the concerted action of the HPV oncoproteins in virus-induced cellular transformation

E6/E7 binding proteins

E6/E7 functions

Functions of the E6 and E7 oncoproteins, and their interaction with each other in steps that lead to cell immortalization Nat Rev Cancer. 2002 May;2(5):342-50. Review.

Systemic and host-cell controls that interfere with HPV-induced progression towards malignant proliferation

HPV pathogenesis-Immune evasion

The biology of HPV infection

How the adaptive immune system ‘sees’ and responds to tumour (or other foreign) antigens inside cells

Immune Evasion Mecahnisms • Subversiion of IFN responses – E7 blocks IFN-alpha inducible genes – E7 inhibits IFN-beta promoter

• Oncoprotein escape • E7 is tolerogenic • Others – – – – –

E7: similar to some human proteins E6/E7 reduce IFN-alpha production in NK cell E6 can down regulate IL-18 E5 affect Ag processing and presentation in APCs ………….

Protective specific immunity to E7 epithelial tumour antigen by administration of an inflammatory stimulus

E7 in peripheral epithelium tolerizes the CTL response.

Natural history of HPV infection 30% 3yr

HPV 14% annually

Normal

60% 3 yr

70% 1st yr

30% 1st yr

91% 2nd yr

9% 2nd yr

8 mo

HPV (-)

LSIL ~10% 2 yr

HPV (+)

5-10% 3yr

<5% 2 yr

HSIL

HPV and non-HPV factors that contribute to HPV-induced malignant progression

HPV is necessary , but not sufficient

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Co-Factors: Environmental? Genetic?

Normal

LSIL

HSIL

SCC

HPV-16 類病毒顆粒疫苗 • 以基因工程技術於酵母菌體內大量合成 HPV 病毒 L1 鞘膜蛋白，經活體結合為類病毒顆粒 (virus like particle, VLP) 後純化為疫苗。 • 可充分激發人體免疫系統，產生高效價之抗病 毒抗體。 • 不帶任何病毒基因，無致病危險性。

人類乳突病毒顆粒

類病毒顆粒

Perspectives • Mechanism exploration • Clinical applications – Diagnosis – Treatment – Vaccine

N Engl J Med 2003;349:2042-54.

NATURE REVIEW/CANCER VOLUME4, DECEMBER 2004

Interaction between DNA Methylation and Histone Methylation

Signaling Networks in Cancer

Hanahan and Weinberg, 2000 Cell 100:57

The End

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