HPV OncoTect

HPV OncoTect is a method for screening cervical carcinoma identifying the oncogenic activity of Human papillomavirus (HPV) in infected cervical cells. This method has been developed by Bruce K. Patterson, M.D in Stanford University School of Medicine (Department of Pathology) and is being used in U.S.A, Canada, South Africa and Spain.

HPV and cervical cancer

HPV is one of the most common sexually transmitted infections and a necessary cause of cervical cancer. [Walboomers, J.M., et al., Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. J Pathol, 1999. 189(1): p. 12-9.] HPV infection is highly transmissible, the majority of young men and women will acquire it at some time in their life. [Franceschi, S., et al., Variations in the age-specific curves of human papillomavirus prevalence in women worldwide. Int J Cancer, 2006. 119(11): p. 2677-84.]

More than 100 types of HPV have been identified which can be classified as high-risk or low-risk depending on their known oncogenic activity. Infections with HPV take place in cervical epithelium and are usually of transient nature. Fortunately about 90% of HPV infections clear within two years without treatment. Only in a small amount of the women infected with oncogenic types of HPV, the infection will progress to high-grade lesions or even cervical cancer in the absence of treatment. [zur Hausen, H., Papillomaviruses and cancer: from basic studies to clinical application. Nat Rev Cancer, 2002. 2(5): p. 342-50.] [ Cuschieri, K.S., M.J. Whitley, and H.A. Cubie, Human papillomavirus type specific DNA and RNA persistence--implications for cervical disease progression and monitoring. J Med Virol, 2004. 73(1): p. 65-70. ]

During persistent infections the viral genomes often integrate into the host chromosome, which results in an overexpression of the viral proteins E6 and E7. These oncoproteins induce immortalization and malignant transformation of cells conferring a certain growth advantage to the infected cells. [ Doorbar, J., The papillomavirus life cycle. J Clin Virol, 2005. 32 Suppl 1: p. S7-15.] [ Snijders, P.J., et al., HPV-mediated cervical carcinogenesis: concepts and clinical implications. J Pathol, 2006. 208(2): p. 152-64.] [ Munger, K. and P.M. Howley, Human papillomavirus immortalization and transformation functions. Virus Res, 2002. 89(2): p. 213-28. ]

Cervical cancer screening

Cervical cancer affects approximately 500,000 women worldwide. Cervical cancer screening programs have dramatically reduced the number of deaths and the prevalence of cervical cancer. Therefore screening programs are the main tool to prevent cervical cancer-associated mortality.

The Papanicoloau (Pap) smear has been the standard of care in the United States for over 40 years, resulting in a 74% decline in deaths due to cervical cancer. [Hakama, M., Screening for cervical cancer. Cancer Treat Res, 1996. 86: p. 41-9.] Despite this success, screening programs that rely on Pap-stained cytological samples have the limitations of relativity low sensitivity (30-87%) and a high false negative rate.Dubious|date=September 2008 [Nanda, K., et al., Accuracy of the Papanicolaou test in screening for and follow-up of cervical cytologic abnormalities: a systematic review. Ann Intern Med, 2000. 132(10): p. 810-9.] [Renshaw, A.A., Measuring sensitivity in gynecologic cytology: a review. Cancer, 2002. 96(4): p. 210-7.] In women 30 years and older, the current HPV DNA test can be used for adjunctive screening with Pap smear to detect oncogenic types of HPV in cervical cytology specimens. Most HPV DNA assays such as type-specific polymerase chain reaction (PCR) and Hybrid Capture II (Digene) detect the present of HPV infection despite the fact that only a small proportion of the women infected with a high-oncogenic-risk type will suffer disease that progresses to cancer. Although HPV assays have a high sensitivity, their specificity is low because they detect an infection that in the vast majority of women do not develop cancer and regress spontaneously. [Arbyn, M., et al., Clinical utility of HPV-DNA detection: triage of minor cervical lesions, follow-up of women treated for high-grade CIN: an update of pooled evidence. Gynecol Oncol, 2005. 99(3 Suppl 1): p. S7-11.]

As persistent infection is a decisive factor for the progressive course of the disease [Ho, G.Y., et al., Persistent genital human papillomavirus infection as a risk factor for persistent cervical dysplasia. J Natl Cancer Inst, 1995. 87(18): p. 1365-71. ] , it may be important to identify a long term persistent infection. For that reason in the last years new molecular markers have been developed and there are new tests that identify cells with malignant transformation. [von Knebel Doeberitz, M., New molecular tools for efficient screening of cervical cancer. Dis Markers, 2001. 17(3): p. 123-8. [12] .] One of these new tests is HPV OncoTect which used as an adjunct to the Pap test is a reliable screening technique to prevent cervical cancer.Fact|date=September 2008 This method is highly sensitive and specific, with a high positive predictive value for detecting the presence of lesions with high probability of progression.Narimatsu, R. and B.K. Patterson, High-throughput cervical cancer screening using intracellular human papillomavirus E6 and E7 mRNA quantification by flow cytometry. Am J Clin Pathol, 2005. 123(5): p. 716-23.]

Despite the fact that continued expression of the E6 and E7 genes of oncogenic HPVs is the molecular switch for the development of cervical cancer [American Cancer Society 2003] [Nakagawa, S., et al., Ubiquitous presence of E6 and E7 transcripts in human papillomavirus-positive cervical carcinomas regardless of its type. J Med Virol, 2000. 62(2): p. 251-8.] [zur Hausen, H., Papillomaviruses and cancer: from basic studies to clinical application. Nat Rev Cancer, 2002. 2(5): p. 342-50] Fact|date=September 2008, HPV OncoTect test quantify E6/E7 protein expression in cervical cells. The level of E6 and E7 gene expression is increased in high-grade lesions compared with low-grade lesions, making the level of E6 and E7 gene expression a functional discriminator between high-risk and low-risk infections. [Woodman, C.B., et al., Natural history of cervical human papillomavirus infection in young women: a longitudinal cohort study. Lancet, 2001. 357(9271): p. 1831-6. ]

How does HPV OncoTect work?

HPV OncoTect is a flow cytometry based in situ test for the detection of HPV E6 and E7 mRNA in intact ectocervical cells. HPV OncoTect takes advantage of the fact that oncogenic genotypes of HPV overexpress E6 and E7 mRNA following integration of HPV into genomic DNA. [Molden, T., et al., Comparison of human papillomavirus messenger RNA and DNA detection: a cross-sectional study of 4,136 women >30 years of age with a 2-year follow-up of high-grade squamous intraepithelial lesion. Cancer Epidemiol Biomarkers Prev, 2005. 14(2): p. 367-72. ] [Molden, T., et al., Predicting CIN2+ when detecting HPV mRNA and DNA by PreTect HPV-proofer and consensus PCR: A 2-year follow-up of women with ASCUS or LSIL Pap smear. Int J Cancer, 2005. 114(6): p. 973-6. ] Current investigations suggest that in situ detection of active viral mRNA precedes or coincides with morphologic changes in cervical cells signifying cervical cancer.

Results:The result is expressed on percentage of analyzed ectocervical cells that overexpress oncoproteins E6 and E7. If this percentage is over 2% the HPV OncoTect result is positive, if it is lower it is a negative result.

*A negative result means there is no overexpresion of high-risk HPV oncoproteins E6/E7. With a negative result the risk of have a cervical cancer in the future is almost null.

*A positive result means the viral DNA has been integrated into the cell genome which results in an overexpression of E6/E7 proteins. If the result of Pap smear is negative but HPV OncoTect result is positive the ginecologist should repeat both tests in 6-12 months. If both tests are positive it is needed a colposcopy or biopsy to confirm the diagnostic.

HPV OncoTect:

*Is a test that identifies persistent HPV infections that can progress to high-grade lesions.

*Is a test that detects the HPV oncogenic activity analyzing cervical cells that overexpress oncoproteins E6 and E7.

*Is a test that can be used at any time of woman life because there is no low age limit.

The sensitivity of HPV OncoTect is higher than a single Pap smearso this test in adjunct to the Pap smear would give a sensitivity of 100% as a primary screening tool.Fact|date=September 2008 The specificity and positive predictive value are also higher than other HPV detection techniques. This might be very useful in screening young women, a cohort in which the prevalence of HPV DNA positivity may be as high as 20%.Dubious|date=September 2008

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