Over 200 HPV types have been identified to date, and among these, approximately 60 infect the human genital tract and can be classified according their oncogenic potential as low- or high-risk HPV types. Low-risk types are more frequently associated with genital warts and low-grade squamous intraepithelial lesions (LSIL), whereas high-risk types are more frequently associated with high-grade squamous intraepithelial lesions (HSIL) and cervical cancer (^{Muñoz et al. 2003}, ^{Bernard et al. 2010}). HPV6 and 11 are the most prevalent low-risk types in genital warts, and HPV16 and 18 are the most frequent high-risk types found in malignant lesions and are associated with 70% of all cervical cancer cases worldwide. Nonetheless, HPV types 31, 33, 35, 45, 52, and 58 are the six most common types in the world after HPV16 and 18, and are responsible for 30% of cervical cancer cases (^{de Sanjosé et al. 2010}).

The APOBEC3 (A3) proteins are cytidine deaminases that exhibit the ability to insert mutations in DNA and/or RNA sequences. APOBEC3B (A3B) has been evidenced as a DNA mutagen with consistent high expression in several cancer types. Data concerning the A3B influence on HPV infection and cervical cancer are limited and controversial. We investigated the role of A3B expression levels in cervical cancer in affected women positive for infection by different HPV types. Tumor biopsies from cancerous uterine cervix were collected from 216 women registered at Hospital do Câncer II of Instituto Nacional de Câncer, and infecting HPV was typed. A3B expression levels were quantified from RNA samples extracted from cervical biopsies using real-time quantitative PCR. Median A3B expression levels were higher among HPV18⁺ samples when compared to HPV16⁺ counterparts and were also increased compared to samples positive for other HPV types. In squamous cell carcinoma, HPV18⁺ samples also showed increased median A3B expression when compared to HPV Alpha-9 species or only to HPV16⁺ samples. Our findings suggest that A3B expression is differentially upregulated in cervical cancer samples infected with HPV18. A3B could be potentially used as a biomarker for HPV infection and as a prognostic tool for clinical outcomes in the context of cervical cancer.