Caracterização da proteína rap1 como biomarcador da neoplasia intraepitelial cervical associada à infecção por papilomavírus humano (HPV)

Abstract

RAP1 (RAS proximate 1), a small GTP-binding protein of the RAS superfamily, is a putative oncogene that is highly expressed in several malignant cell lines and types of cancers, including some types of squamous cell carcinoma (SCC). However, the participation of RAP1 in cervical carcinogenesis initiated by Human papillomavirus (HPV) is unknown. We conducted a cross-sectional study of paraffin embedded cervical biopsies to determine the association of RAP1 with cervical intraepithelial neoplasia (CIN). HPV detection and genotyping were performed by nested polymerase chain reaction (PCR) and viral load by real-time PCR of E6 and E7 oncoproteins mRNAs. Standard and quantitative immunohistochemistry assessment of RAP1, RAP1 GAP, p16INK4A (p16) and Ki67 expressions in fixed tissue were performed on 319 paraffin-embedded cervical biopsies that were classified as normal or non-dysplastic mucosa (NDM) (n = 65); CIN grade 1 (n = 102), CIN grade 2/3 (n = 85), and SCC (n=67). RAP1A, RAP1B and p16 gene expression quantification was performed by real-time PCR. HPV DNA was detected in 56.73% of the samples in all groups, mainly CIN 2/3 (68.42%) and SCC (75.00%). A gradual increase in RAP1, RAP1 GAP, p16 and Ki67 expressions in NDM < CIN 1 < CIN 2/3 (p<0.001) specimens was observed. Specifically, a progressive increase in the RAP1 expression levels increased the risk of CIN 1 [odds ratio (OR) = 3.50; 95% confidence interval (CI) 1.30-10.64] 3.5 fold and the risk of CIN 2/3 (OR=19.86, 95% CI 6.40-70.79) nearly 20 fold when compared to NDM. In addition, stereotype ordinal logistic regression analysis showed that this progressive increase in RAP1 expression more strongly affected CIN 2/3 than CIN 1. Compared to CIN 1 and CIN 2/3 groups, it also observed lower relative gene expression RAP1A in the SCC group (p <0.05). We found no differences in the relative gene expression RAP1B and p16. Thus, our findings suggest that RAP1 may be a useful biomarker for the diagnosis of CIN.