Question

briefly describe how papillomaviruses cause cancer?

Answer 1

When you're exposed to genital human papillomavirus (HPV), your immune system usually prevents the virus from doing serious harm. But sometimes, the virus survives for years. Eventually, the virus can lead to the conversion of normal cells on the surface of the cervix into cancerous cells. Due to this long life of the virus on the cervical cells surface it slowly develops into a precancerous stage known as cervical intraepithelial neoplasia, which usually goes away spontaneously but sometimes it generates into invasive cancer.

The molecular basis of the cancer cause is that the HPV infects squamous epithelial cells, which have the capacity to proliferate, and get access to basal cell during trauma or abrasion. In the basal cells, HPV infection induces the expression of viral genes that helps in the viral replication. The interaction of HPV with the host cells occurs via surface receptors such as heparin sulfate proteoglycans and alpha 6 integrins. The early proteins E1 and E2 are required for the initiation of replication. The protein E2, being the transcriptional repressor of E6 and E7, controls the expression of E6 and E7. The mode of replication is the rolling circle mechanism during which the virus gets integrated into the human genome. The integration disturbs the E2 gene thereby resulting in a higher expression of E6 and E7 oncoproteins and leading to cell transformation. Due to higher expression of these oncoproteins the cancer gradually develops withing humans.

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