Opportunities to Improve the Prevention and Treatment of Cervical Cancer

Abstract

Human papillomavirus (HPV) is a causal agent for approximately 5.3% of cancers worldwide, including cervical cancer, and subsets of genital and head and neck cancer. Persistent HPV infection is a necessary, but not sufficient, cause of cervical cancer. Of the >100 HPV genotypes, only about a dozen, termed "high-risk", are associated with cancer. HPV-16 is present in approximately 50% of all cervical cancers and HPV-16, HPV-18, HPV-31 and HPV-45 together account for approximately 80%. Most high-risk HPV infections are subclinical, and are cleared by the host's immune system. The remainder produces low or high-grade squamous intraepithelial lesions (SILs), also called cervical intraepithelial neoplasia (CIN), which also may regress spontaneously. However persistent high grade SIL represents the precursor lesion of cervical cancer and carcinogenic progression is associated with integration of the viral DNA, loss of E2 and upregulation of viral oncogene expression, and chromosomal rearrangements like 3q gain. Cytologic screening of the cervix for SIL and intervention has reduced the incidence of cervical cancer in the US by an estimated 80% and HPV viral DNA and other molecular tests may improve screening further. The licensure of a preventive HPV vaccine ushers in a new era, but issues remain, including: protection restricted to a few oncogenic HPV types, access in low resource settings and impact on current cytologic screening protocols. Importantly, preventive HPV vaccination does not help with current HPV infection or disease. Here we examine the potential of second-generation preventive HPV vaccines and therapeutic HPV vaccination to address these outstanding issues.