A 28-year-old woman from Delhi presents with a 6-month history of abnormal vaginal bleeding and postcoital spotting. On speculum examination, a friable, cauliflower-like lesion is noted on the cervix. Pap smear shows atypical squamous cells of undetermined significance (ASCUS). HPV testing is positive for high-risk types (HPV-16 and HPV-18). Colposcopy with biopsy confirms cervical intraepithelial neoplasia grade 2 (CIN 2). Which viral protein is primarily responsible for the malignant transformation observed in this patient?

Explanation

## Viral Oncogenesis in High-Risk HPV ### Mechanism of Malignant Transformation **Key Point:** High-risk HPV types (HPV-16, HPV-18, HPV-31, HPV-33) express E6 and E7 oncoproteins that drive malignant transformation through inactivation of critical tumor suppressors. ### E6 and E7 Oncoprotein Functions | Oncoprotein | Target | Mechanism | Consequence | |---|---|---|---| | **E6** | p53 (tumor suppressor) | Binds p53 → ubiquitin-mediated degradation | Loss of apoptosis, cell cycle arrest | | **E7** | Rb (retinoblastoma protein) | Binds Rb → E2F release | Uncontrolled G1/S transition | | **E7** | p21, p27 (CDK inhibitors) | Direct degradation | Loss of cell cycle checkpoints | **High-Yield:** The E6-p53 and E7-Rb axis is the cornerstone of HPV-driven cervical carcinogenesis. This is tested in nearly every NEET PG virology exam. ### Progression Model in This Patient 1. **Acute infection** → HPV-16/18 integration into host genome 2. **Early phase** → E6/E7 expression → p53 and Rb inactivation 3. **Intermediate phase** → Loss of growth control → CIN 1 (LSIL) 4. **Advanced phase** → Accumulation of secondary mutations → CIN 2/3 (HSIL) → Invasive cancer **Clinical Pearl:** The presence of HPV-16 and HPV-18 (highest oncogenic potential) with CIN 2 indicates this patient is at substantial risk for progression to invasive cervical cancer within 5 years if untreated. E6/E7 expression is the driving force. ### Why E6/E7 Are the Answer - **E1 and E2** are regulatory proteins involved in viral DNA replication, not transformation - **L1 and L2** are structural capsid proteins; they are not expressed in malignant cells and have no transforming capacity - **E4 and E5** have minor roles in viral replication and immune evasion but are not the primary oncogenic drivers **Mnemonic:** **"E6 Eats p53, E7 Evicts Rb"** — remember that the early proteins (E6, E7) are the oncogenic culprits. [cite:Robbins 10e Ch 7]