Revi e w HPV and carcinogenesis .HP// and carcinogenesis M. A. Gonzalez Intxaurraga, R. Stankovic, R. Sorli and G. Trevisan. SUMMARY The HPV's mechanism of carcinogenesis is not completely understood. The possibility of evolving into direction of malignancy depends on the type of virus, the synergic action with different physical, chemi- cal and biological agents, the genetic constitution of the host and the immune defense mechanism of the host, all of which are able to modify the course of HPV infection. Introduction The human papillomaviruses (HPV) are small viruses with double stranded DNA that have a particular tro- pism for the epithelium inducing its proliferation. It is believed that the HPV enters the body after slight trauma to the epithelium and needs terminally differentiated epithelial cells for replication (1). Up to now 100 (2) different genotypes have been recognized, ofwhich one small group has been identi- fied as a causing agent for certain types of tumors in severa! epithelia. It is the number one cause of cervical carcinoma (3). The DNA of the HPV can persist in the infected cell in episomic or extrachromosomic form or can be in- corporated into chromosomes of the host cell . Conse- quently, the derived cells will also carry within their genetic material the genetic material of the virus, re- sponsible for the cellular transformation. The HPV genome contains a double-stranded cir- cular DNA of about 7900 base pairs that can be func- tionally divided into two regions: l. LCR (Long Control Region) - necessary for the regu- lation of the genic expression and far the DNA replica- tion. 2. ORF (Open Reading Frames) - that can be divided into the Early Region, necessary for the replication, cel- lular transformation and far the control of vira! tran- scription and the Late Region that codes for the capsid proteins that comprises the miter protein coat of the virus (1). Within the Early Regions (E), it is possible to distin- guish different genes with specific functions : - El and E2 have an important role in viral DNA replica- tion. The E2 participates in the regulation of LCR tran- scriptions, and decreases the expression ofE6 and E7. Acta Dermatoven APA Vol 11, 2002, No 3 - ---------- ----- -95 HPV and carcinogenesis - E3, whose function is stil! not known - E4, which codes one family of small proteins involved in the transformation of tbe bost celi producing alter- ations of tbe mitotic signals and interacting witb tbe keratin wbich becomes destabilized. - E5 interacts witb tbe growth factor's receptors and stimulates tbe cellular proliferation. It also decreases intercellular communication witb tbe aim to isolate tbe transformed cells. It also stimulates the expression of E6 and E7. - E6 acts as an oncogene, stimulating tbe growtb ancl transformation of tbe bost cell by tbe inhibition of pro- tein p53's normal oncosuppressor function. - E7 acts as an oncogene, inducing cellular prolifera- tion by inbibition of the protein pRb, p107 and p130. - ES, wbose function is stil! not known. Within the Late Region (L), it is possible to distin- guish: Ll whicb codes for major capsid protein and can form vims-like particles. L2 whicb codes for minor capsid protein. The oncogenic mechanism Tbe HPV's mecbanism of carcinogenesis is not com- pletely understood. HPV can produce immortality in keratinocytes and acts alone even if different cofactors, still not completely located, are necessary for malignant conversion. Tbe possibility of evolving into direction of malig- nancy clepencl~ on tbe type ofvims, tbe synergic action witb different pbysical, cbemical ancl hiological agents, tbe genetic constitution of tbe bost ancl on tbe immune clefense mecbanisms of tbe host, all of wbicb are able to moclify the course of HPV infection. In the case of bigb risk HPV infection ancl uncler favorable conditions, tbe vira! genome is integrated into tbe bost genome which is tbe necessary event for the keratinocytes immortality ( 4). During tbis process of integration the circular form of vira! genome breaks at the leve! of tbe El and E2 regions, never at tbe leve! of tbe E6 or E7 region. Different stuclies have shown that the integratecl part of the genome corresponcls to El, E6 ancl E7 while the regions from E2 to E5 are !ost ancl are not transcribecl in tbe tumors. The loss ofE2 during tbis process of integration produces the loss of E6 ancl E7 control. Therefore, the sequences E6 and E7 are cli- rectly involvecl in the cellular cycle by inhibiting the normal functions of p53 ancl pRb respectively (5). The protein p53 is known as tbe "genome's guarcl" ancl in the case of DNA damage, the p53 can provoke the ar- rest of cellular division ancl assure the tirne necessary for DNA repair (6). If clamage can not be repaired, p53 is able to incluce the programmed cellular cleatb and prevent the propagation of DNA damage in subsequent generations of cells. In the case of other types of tu- mors p53 is usually mutated and acts asa real oncogene. In tbe case ofHPV infection, E6 suppresses the proper- ties of p53 gene product achieving the functional equivalent of the two hits required to knock out both alleles of a tumor suppressor gene (7). The mutations of p53 are normally not found. The E7 protein interacts with retinoblastoma protein (pRb) , which is the crucial factor for the cellular cycle control. This interaction causes the rele ase of the transcription factor E2F, which is now free to act and can stimulate the cellular divi- sion. E7 is also able to bind and inactivate the proteinkinase inhibitors p21 and p27 and can interact with different proteins whose significance has stil! not been determined. E6 and E7 can cooperate with cellular oncoproteins like ras and myc which enables the virus to act at the leve! of growth factors and cellular and nuclear metabo- lism producing oncogenic cells. E6 and E7 can provoke directly DNA mutations of the bost celi, probably by causing alterations of DNA repah' mechanisms. This means tbat certain types of HPV are able to cause ma- lignant lesions even witbout tbe action of otber cofac- tors. Tbe exact role of tbe immune response against bigb risk HPVs is not completely clear. HPVs are obligatory intraepitbelial pathogens that replicate at tbe superfi- cial layers of the mucosa and epidermis where the cells are more differentiated. Both types ofimmune response (antibodies and celi mediated) have been demonstrated in bumans . Cell-mediated immunity plays a crucial role in controlling HPV infection. The antiboclies against HPV can be of the type IgA, IgM or IgG reaching maximum levels 6 to 12 montbs after the beginning ofthe infection. There is an increasecl prevalence of antibodies against proteins E7 and E4 in patients with cervical intraepithelial neoplasia and with cervical carcinoma. It is possible that in the future the measuring of the antibodies against E7 will become a marker to assess the response of a specific therapy. The presence of antibodies against E4 is associated with vi- ra! replication and is believed to coincicle with the first host's contact with HPV (8). The regression of HPV le- sions is associated witb a characteristic histologic re- sponse with participation of T lymphocytes and acti- vated macrophages (cellularly mecliated). In the case of immunosuppressed patients tbe possibility of high risk infections is increased because of the lack of im- mune response, tbe oncogenic effect of tbe drug ad- ministration, as well as chronic antigenic stimulation. HPV related neoplasias The iclea that cervical carcinoma can be related to sexual activity and to infective agents was postulated in 1842 (9). Subsequently, many sex:ually transmitted in- Review 96 ----- ------ - ----------------------- Acta Dermatoven APA Vol 11, 2002, No 3 R eview fective agents have been suspected as responsible far this type of neoplasia. In 1977, by means of cytologic, hystologic and colposcopic studies, the first evidences ofthe involvement ofHPV in cervical cancer (CC) were obtained. In 1983, Syrjanen identified HPV vira! anti- gens in 50 % of the cases of cervical displasia . In the following years, different types ofHPVs have been iden- tified in correlation with different neoplasias (10). Up to now high risk HPVs have been known to be involved in the following diseases: 1. Epidermodysplasia verruciformis (EV) This is a rare, lifelong, autosomal recessive heredi- tary disorder affecting the skin characterized by dys- function of cell-mediated immunity. The disease usu- ally begins in infancy or early childhood with develop- ment of various types of warts and plaques involving mostly sun-exposed areas of the skin. Different types of HPV have been identified in the lesions: HPV 3, 5, 8, 9, 10, 12, 14, 17, 20, 21, 23, 25, 28, 38, 47 and 49. The combination of different HPV types, such as 3, 5, 8, 14 and 17, immune deficiency and solar exposure result in high risk far multiple skin cancers (principally squamocellular type) in these patients (11,12). Cutane- ous carcinomas, developing in about half ofEV patients, typically appear during the fourth and fifth decades of life and are usually associated with the oncogenic HPV 5 (13) and HPV 8. Certain authors believe that EV is not a typical HPV provoked neoplasia because genetic dis- position is involved. 2. Cervical intraepithelial neoplasia (GIN) and invasive cervical carcinoma (!CC) In the case of cervical neoplasia of the uterus the presence of HPV is greater than or equal to 95 %. Dif- ferent types ofHPV have been identified: 16, 18, 31, 33, 35, 39, 42, 43, 44, 51, 55, 58, 72 ancl 73 . Types 16 and 18 are most clearly shown to be a human carcinogen. Among other anogenital HPV types 6, 11 , 26, 27, 30, 35, 39, 40, 45, 59, 61, 62, 64, the epidemiological evidence is strongestfor HPV 3 1 and 33 (14). In the majority of cases the presence of HPV alone is not sufficient far the development of neoplasia ancl different cofactors have been identified: - tobacco, probably by tar deposits that interfere with the cervical physical barrier ancl with local Langerhans cells; - other sexually transmitted diseases ( e.g., HIV, herpes virus, Chlamydia species); - conditions of tempora1y immunodeficiency, such as pregnancy, the use of contraceptive cl.rugs, steroid treat- ment; or permanent immunodeficiency, as in the case ofleukemias, lymphomas, AIDS, renal grafts, etc. In the cervical smear the presence of HPV is three times more frequent during the pregnancy than in non-pregnant women; HPV and carcinogenesis - alterations of hormona! status; - beta-carotene deficiency; - repeated local traumas and promiscuity, which in- crease the statistical probability; - some modalities of sexual behavior (10). 3. Vaginal intraepithelial neoplasia (VAJN) and vaginal carcinoma (VC) It is not frequent when compared with cervical neo- plasia and in many cases it represents the propagation of cervical neoplasia . In this type of neoplasia HPV is present in 50 % of cases and the types usually identified are 16, 18 and 31. However the routine diagnostic pro- cedures have n ot been directed to intraepithelial neoplasias other than CC. 4. Vulvar intraepithelial neoplasia (VINJ (Bowenoid papulosis, erythroplasia oj Queyrat and vulvar carcinoma) In these conditions HPV is present in more than 50 % of the cases, usually type 16. Patient history usually reveals the previous presence of condyloma (15). Re- cent studies suggest that in erythroplasia of Queyrat, in contrast to other genital neoplasias, a co infection with HPV type 8 and HPV type 16 occur. The presence or absence of HPV type 8 might help to distinguish be- tween erythroplasia of Queyrat and Bowen's disease. 5. Penile carcinoma (including Bowenoid papulosis) HPV can be identified in 50 % of cases and is strongly associated with type 16. Patient history is frequently positive far the presence of condylomas. Buschke- Lowenstein syndrome or giant condylomatosis is asso- ciated with types 6 and 11, which are considered as vims types with low risk. 6. Anal (AC) and perianal carcinoma (PC) HPV bas been found in more than 70 % of cases. The identified types ofHPV correspond to those found in the cervical neoplasia. AC and PC are mud1 more common in immunosuppressed patients like HIV-infected individuals. 7. Oropharyngeal carcinoma (EC) HPV DNA has been found in 20 % of tumors locali- zed at the tongue and tonsillas and corresponds to the types identified in the anogenital lesiohs. 8. Esophageal carcinoma (EC) Far this type of carcinoma the results are stili not clear. The role of infected agents, among them of HPV, Acta Dermatoven APA Vol 11, 2002, No 3 - ---------- - - - --- --- -- 97 HPV and carcinogenesis is already suspected and some authors have isolated HPV in 15 % - 30 % of the biopsy specimens. HPV 73 was identified in EC by some authors (16) . 10. Melanoma The HPV could be detected in melanoma biopsy specimens, but it has not a role in inducing the devel- opment of this tumor. HPV may be correlated with rapid melanoma progression because may act as a cofactor 9. Non-melanoma skin cancers (basal cell carcinoma-BCC and squamous cell carcinoma-SCC) (19). The presence of HPV-DNA is demonstrated in 90% of cutaneous SCC from renal allograft recipients. These HPV types (20, 23 and 38) are ali related to the epidermodysplasia verruciformis group. The relation between infection with certain types of HPV and the development of non-melanoma skin cancers in immu- nocompetent patients has stil! not been explained and may be just casual or the virns can be a real etiologic agent. One recent study with 61 immunocompetent patients suggests that the occurrence of HPV-DNA in BCC does not reflect a major etiologic role of HPV in this cancer (17). Conclusion The evidence of association between certain tumors and HPV infection today is indisputable. In the case of anogenital tumors different types of HPVs have been identified. Of ali the sexually transmitted diseases, condylomas have the highest frequency in the devel- oped world. Different studies are t1ying to determine the cancer risk after HPV infection, with the results vary- ing from 6 % to 33 % and a tirne interval from 1.7 to 2.7 years for intraepithelial neoplasias and 6 years for inva- sive tumors. The role of HPV in non-melanoma skin cancer car- cinogenesis remains speculative (18). lY F.0' .,._., 1·., v 'l.'' ;~ r ('' p Q .H. t .. J..!;· .1.1 . :!i .il š.1-.e .1 V _j 1_!; ;._·:, l. Olmos L. Condilomas Acuminados (Verrugas genitales) I. Enf Trans Sex 1990; 4: 73-81. 2. Tyring SK. Human papillomavirus infections: Epidemiology, pathogenesis, and host immune response. J Am Acad Dermatol 2000; 43: S18-26. 3. Bosch FX, Manos MM, Muiioz N, et al. Prevalence of Human papillomavirus in Cervical Cancer: A Worldwide Perspective. J Natl Cancer Inst 1995;87:796-802. 4. McGlennen RC. Human papillomavirus oncogenesis. Ciin Lab Med 2000; 20(2): 383-406. 5. Swan DC, Vernon SD, Icenogle JP: Cellular proteins involved in papillomavirus-induced transforma- tion. Arch Virol 1994; 138(1-2):105-15. 6. Sanchez Y, Elledge SJ. Stopped for repairs. Bioessays 1995;17(6): 545-8. 7. Scheffner M, Werness BA, Huibregtse JM, et al. The E6 oncoprotein encoded by human papillomavirus types 16 and 18 promoted the degradation of p53. Cell 1990; 63: 1129-36. 8. Dillner J. The serological response to papillomaviruses. Semin Cancer Biol 1999:9(6):423-30. 9. Rigoni-Stern. Fatti statistici relativi alle malattie cancerose. Gior Servire Progr Path Terap 1842; 2: 507. 10. Olmos L. Condilomas Acuminados (Verrugas genitales) II. EnfTrans Sex 1990; 4: 131-42. 11. Jackson S, Storey A. E6 proteins from diverse cutaneous HPV types inhibit apoptosis in response to UV damage. Oncogene 2000;27; 19(4): 592-8. 12. Payne D, Chan TS, Wagner R, et al. Cloning of mucosal and cutaneous HPV sequences in a metastatic squamous cell carcinoma from an epidermodysplasia verruciformis patient. Anticancer Res 1996;16(3A): 1165-6, 13. Ramos N, Rueda LA, Bouadjar B, et al. A susceptibility locus for Epidermodysplasia Verruciformis, an abnormal predisposition to infection with the oncogenic human papillomavirus type 5, maps to cluo- mosome 17qter in a region containing a psoriasis locus. J Invest Dermatol 1999; 112: 259-63. 14. Katase K, Teshima H, Hirai Y, et al. Natura! history of cervical human papillomavirus lesions. Intervirology 1995; 38(3-4): 192-4. Review 98 - - ---------- - - ----------------- ---Acta Dermatoven APA Vol 11, 2002, No 3 Review AUTHORS' ADDRESSES HPV and carcinogenesis 15. Joste NE, Rushing L, Granados R, et al. Bethesda classification of cervicovaginal smears: reproduc- ibility and vira! correlates. Hum Pathol 1996; 27(6): 581-5. 16. \Vest AB. Soloway GN, Lizarraga G, et al. Type 73 human papillomavirus in esophageal squamous celi carcinoma: a novel association. Cancer 1996; 77(12): 2440-4. 17. Harwood CA, Surentheran T, McGregor )M, et al. Human papillomavirus infection and non-mela- noma skin cancer in immunosuppressed and immunocompetent individuals. J Med Virol 2000; 61(3): 289-97. 18. Kiviat NB. papillomaviruses in non-melanoma skin cancer: epidemiological aspects. Semin Cancer Biol 1999; 9(6): 397-403. 19. Dreau D, Culberson C, Wyatt S, et al. Human papillomavirus in melanoma biopsy specimens and its relation to melanoma progression. Ann Surg 2000; 231 (5): 664-71. Maria Angeles Gonzalez Intxaurraga, MD, Institute oj Dermatology, University ojTrieste, Ospedale di Cattinara, Strada per Fiume 34149, Trieste, Italy. Reija Stanlwvic, MD, dermatologist, same address Rodolfo Sorli, MD dermatologist, same address Giusto Trevisan, MD, projessor and chairman, same address Correspondence: Dr. MA. Gonzalez Intxaurraga, Institute oj Dermatology, University ojTrieste, Ospedale di Cattinara, Strada per Fiume 34149, Trieste, Italy. Acta Dermatoven APA Vol 11, 2002, No 3 - - -------- - ------- 99