Which of the following statement about carcinogenesis is false
Correct Answer: Papilloma viruses produce tumors in animal but not in human
Description: Ref Harrison 17/e p487 HPV, the causative agent of cervical neoplasia, has a tropism for the immature squamous cells of the transformation zone. Most HPV infections are transient and are eliminated within months by an acute and chronic inflammatory response. A subset of infections persists, however, and some of these progress to cervical intraepithelial neoplasia (CIN), precursor lesion from which most invasive cervical carcino- mas develop. HPV is detectable by molecular methods in nearly all cases of CIN and cervical carcinoma. Impoant risk factors for the development of CIN and invasive carcinoma thus are directly related to HPV exposure and include * Early age at first intercourse * Multiple sexual paners * Male paner with multiple previous sexual paners * Persistent infection by high-risk strains of papillomavirus Although HPV infection occurs in the most immature squamous cells of the basal layer, replication of HPV DNA takes place in more differentiated overlying squamous cells. Squamous cells at this stage of maturation do not normally replicate DNA, but HPV-infected squamous cells do, as a consequence of expression of two potent oncoproteins encoded in the HPV genome called E6 and E7. The E6 and E7 proteins bind and inactivate two critical tumor suppressors, p53 and Rb, respectively (Chapter 5), and in doing so promote growth and increased susceptibility to additional mutations that may eventually lead to carcinogenesis
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