HPV and Cervical Cancer One of those deadliest but preventable diseases catch early and try to prevent HPV infection HPV is like the common cold everybody gets it HPV infection leads to integration of oncogenes into DNA of epithelial cells lining cervix and can cause cancer Sex plus differences in access to health care equates to lots of disparity in incident and death rates across the world and the US Vaccination of youth decreases incident rates Cervical cancer history Epidemiologists working in the early 20th century noted the following Cervical cancer was common in female sex workers Rare in nuns except for those who had been sexually active before entering the convent More common in the 2nd wives of men whose first wives had died from cervical cancer Infectious agent Cervical cancer was linked to HPV and now over 100 strains of HPV are known Common HPV Types 100 types of HPV 23 are present in the genital tract 12 main types associated with cancer and considered high risk 16 18 31 33 35 39 45 51 52 68 69 most women will clear an HPV infection within 9 15 months women with persistent high risk HPV infection are 300 times more likely to develop cervical cancer How does HPV cause cancer HPV gene expression timing Viruses express their genes in 2 phases early E and late L The HPV early genes E6 and E7 are associated with cancer viral oncogenes E6 protein causes p53 tumor suppressor degradation and promotes telomerase activity E7 protein causes Rb tumor suppressor degradation HPV hijacks epithelial cells Once integrated into host DNA then cancer is likely HPV hides from the immune system by inserting into host DNA persistent infection Not mutation causing cancer it makes the immune system think that it s healthy so that it won t attack them This leads to over expression of E6 and E7 and cancer Prevalence of HPV infection There are currently around 20 million people infected Each year more than 20 000 HPV associated cancers occur in women cervical most common About 12 000 HPV associated cancers occur each year in men oropharyngeal cancer most common Risk factors of cervical cancer Smoking Started having sex before age 18 HPV infection Multiple sex partners Other STIs Multiple pregnancies Oral contraceptives Diet Molecular genetic factors p53 Rb Family history Low socioeconomic status Pap test and cervical cancer Pap test developed in 1943 by George Papanicolaou As result cervical cancer dropped from the 2nd leading cause of cancer deaths among American women to the 13th in the US Most successful screening test Pap smear morphology Dysplasia a higher nuclear to cytoplasmic ratio means nucleus is larger than it should be for the size of the cell Mild dysplasia the nucleus is about 3 4 times larger than it should be Moderate dysplasia the nucleus is 5 6 times larger than it should be Severe dysplasia the nucleus is taking up most of the cell HPV DNA integration and PCR test for virus If you get a positive test without any other information creates fear because the infection might not be cancerous false positives Treating cervical cancer Traditional radiation and chemotherapy Loop electrosurgical excision procedure compressed nitrogen gas flows through a cryo probe making the metal cold enough to freeze and destroy the abnormal cervical tissue Advanced states hysterectomy removes the uterus and may also remove the cervix and the vagina Recurrent pelvic exteneration
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