Human papillomavirus (HPV)

associated skin diseases

Baki Akgül

Institute of VirologyUniversity of Cologne

Germany

Skin Tumour LaboratoryCancer Research UK,

London, UK

HPVs are small DNA tumour viruses.

HPVs can be subdevided in cutaneous and mucosal types based on their anatomical site of infection.

mucosal types (alpha types: HPV16, 18) are associated with cervical cancer

The association between HPV and skin cancer was first identified in patients with the rare disease Epidermodysplasia verruciformis (EV)

EV patients have a predisposition to infection with EV types or beta-HPV types) and develop non-melanoma skin cancer (NMSC), mainly SCCs, at sun-exposed body sites.

These skin cancers frequently harbour the oncogenic types HPV5 or HPV8.

HPV and skin cancer

De Villiers et al., Virology, 2004

Recent epidemiological studies have shown that HPVs are also found in SCCs

of the general population.

27-85% of SCC positive compared to normal skin where 15-35% of samples

were positive for HPV

Remarkable is the even higher prevalence of beta-HPV (85%) in premalignant

actinic keratoses (Pfister et al., 2003).

Beta-HPV prevalence in skin tumours

Akgül et al., J. Pathol., 2006

Beta-HPV loads in skin tumours

However, viral DNA load in skin tumours is low; a single HPV copy can be

detected in only 10 - 10000 dysplastic cells, confirmed by in situ hybridization

and quantitative PCR).

The HPV-DNA loads in actinic keratoses,however, exceeds those in NMSC, which suggests a particular involvement of HPV in the early stages of cutaneous oncogenesis.

SCC AK

1 HPV copy per >500 cells 23 32

1 HPV copy per 50-500 cells 8 8

1 HPV copy per 5-50 cells 15 28

1 HPV copy per <5 cells 0 12

SCC, HPV15 (Quant. PCR: 1 HPV copy per 708 cells)

In situ hybridization quantitative PCR

Weissenborn et al., JID, 2005

Biochemical studies

Since cell transforming activities of EV-HPV (beta-HPV) proteins differ from the

alpha-HPV types (HPV16):

The aim of our biochemical study was to analyze effects of the oncogenic HPV8

early genes E2, E6, E7 on human keratinocytes in organotypic skin cultures (raft-

cultures) because of the fact that the papillomavirus life cycle is linked to the

differentiation of the skin.

Akgül et al., J. Pathol, 2006

Use of collagen type 1 gels, repopulated with 3T3 mouse fibroblasts

Boxman et al., 2001

Organotypic skin cultures

primary dermal fibroblasts on reticular dermis

primary cutaneous keratinocytes (expressing HPV8 genes)

on papillary dermis

Akgül et al.

De-epidermised human dermis

HPV8-E7 causes invasion of keratinocytes into the dermis

control HPV8 E7 HPV8 E6/E7

HPV8 E7 HPV8 E7

Akgül et al., Cancer Res., 2005

Control

HPV8 E7

21 days

Basement membrane is disrupted in HPV8-E7 culturesLocalization of type VII collagen

also lack of:Collagen type IVLaminin V

Control

HPV8 E7

Akgül et al., Cancer Res., 2005

MMP-1 MMP-8 MT1-MMP

Control

HPV8 E7

Control

HPV8 E7

Control

HPV8 E7

MMP expression in HPV8-E7 cultures

Akgül et al., Cancer Res., 2005

Transgenic mice model

HPV8 trangenic mouse with benign skin tumour

transgene

Generation of a transgenic mouse with the complete early region of HPV8 under control of the keratin-14 promoter.

99,4% of HPV8-transgenic mice developed single or multifocal benign tumors, characterized by varying degrees of epidermal dysplasia

SCC developed in 6% of animals

Skin tumours developed without any further treatment with physical or chemical carcinogens.

Schaper et al., Cancer Res., 2005

Immunhistochemical detection of MMP in mouse SCC

negative control MT1-MMP staining

negative control MMP-13 staining

Akgül et al., Exp. Dermatol. 2005

Conclusions

In contrast to cervical cancer, the presence of HPV is probably not mandatory for maintenance of the malignant phenotype of skin cancer cells.

Low DNA loads, a small number of HPV-positive cells and higher loads in actinic keratoses are compatible with a role of cutaneous HPVs as a carcinogen in early phases of non-melanoma skin cancer development.

The induction of human keratinocyte invasion by HPV8-E7 and the spontaneous development of skin cancers in HPV8 transgenic mice provided the first experimental evidences for a role of HPV in NMSC development.

Acknowledgements

Skin Tumour Laboratory, Cancer Research UK

Alan StoreyHarshad Navsaria

Irene LeighCharlotte Proby

Catherine Harwood

Institute of Virology, University of Cologne

Herbert PfisterRegina Pfefferle

Sönke Weissenborn

Department of Dermatology, Cologne

Cornelia MauchThomas Krieg