HPV and cervical carcinogenesis
- Mechanism
Almost every cervical cancer starts with a persistent high-risk HPV infection whose two proteins switch off the cell's main brakes.
What it is
Nearly all cervical carcinomas are caused by persistent infection with high-risk human papillomavirus, mainly types 16 and 18. The virus infects the immature basal cells of the transformation zone; most infections clear within a couple of years, but in persistent ones the viral E6 and E7 proteins inactivate p53 and RB. Integration of the viral genome raises E6 and E7 production and, with added host mutations, leads from a high-grade lesion to invasive cancer over years. This long precursor phase is what makes screening and vaccination so effective.
Function
- Productive infection: the virus replicates as the epithelium matures and is shed from the surface; koilocytes are the visible mark.
- Transforming infection: the viral oncoproteins keep basal-type cells dividing and stop them maturing; atypical immature cells rise through the epithelium.
Step by step
- High-risk HPV reaches the basal and reserve cells of the transformation zone through small breaks in the epithelium.
- Most infections are productive and transient: the immune system clears them within about two years.
- In a minority the infection persists, and E6 and E7 inactivate p53 and RB.
- The viral genome integrates into host DNA, E2 is lost and E6 and E7 are made in excess; cells proliferate and accumulate DNA damage.
- The epithelium becomes a high-grade squamous intraepithelial lesion (CIN 2–3).
- Additional host mutations and immune escape, over years, allow invasion through the basement membrane.
Low-risk vs high-risk HPV
| Feature | Low-risk HPV (6, 11) | High-risk HPV (16, 18 and others) |
|---|---|---|
| Typical lesion | Condyloma, LSIL | HSIL and carcinoma (also many LSIL) |
| Viral DNA | Stays episomal | Often integrated into host DNA |
| E6 and E7 binding to p53 and RB | Weak | Strong |
| p16 staining | Patchy or negative | Strong and diffuse |
| Vaccine coverage | Quadrivalent and nonavalent vaccines | All vaccines cover 16 and 18; nonavalent covers five more |
Markers
- p16 (block-type)
- Ki-67 (proliferation high in the epithelium)
- HPV DNA or mRNA tests
Clinical notes
- The same mechanism causes HPV-associated cancers of the vulva, vagina, anus, penis and oropharynx.
- People with HIV clear HPV less often and develop high-grade lesions and cancer more frequently.
- In Latin America, HPV 16 and 18 account for most high-grade lesions and cancers, so the available vaccines cover the main types.
Test yourself
Think of the answer, then tap the question to see it.
Which HPV proteins inactivate p53 and RB?
E6 targets p53 for degradation; E7 binds RB and releases E2F, driving the cell cycle.
Why is p16 overexpressed in HPV-transformed cells?
E7 inactivates RB, and loss of RB function removes the negative feedback on p16, so p16 accumulates; diffuse staining marks transforming high-risk HPV.
What is the significance of viral integration?
Integration disrupts E2, which normally represses E6 and E7, so the oncoproteins are made in excess; it is typical of high-risk types and of progression.
Why does the transformation zone matter?
Its immature metaplastic and reserve cells are the main target of HPV, so precursor lesions and most carcinomas start there and screening samples it.
Elsewhere in DurgiPedia
- Cervix and vagina: the transformation zone
- Oncogenes and tumour suppressor genes
- Tumor immunology and checkpoint inhibitors
Connections
Microorganisms1
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Human Papillomavirus (StatPearls (NCBI Bookshelf), 2026); Cervical Cancer (StatPearls (NCBI Bookshelf), 2026); Distribution of human papillomavirus genotypes by severity of cervical lesions in HPV screened positive women from the ESTAMPA study in Latin America (PloS one, 2022).
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Representative model, for educational purposes only.