Carestiato Fernanda Nahoum, Amaro-Filho Sergio Menezes, Moreira Miguel Angelo Martins, Cavalcanti Silvia Maria Baeta
Universidade Federal Fluminense, Departamento de Microbiologia e Parasitologia, Niterói, RJ, Brasil.
Instituto Nacional de Câncer, Programa de Genética, Rio de Janeiro, RJ, Brasil.
Mem Inst Oswaldo Cruz. 2018 Dec 17;114:e180456. doi: 10.1590/0074-02760180456.
BACKGROUND Epigenetic modifications in host cells, like p16 ink4a methylation, have been considered as putative complementary mechanisms for cancer development. Because only a small proportion of infected women develop cervical cancer, other factors might be involved in carcinogenesis, either independently or in association with high-risk human papillomavirus (HR-HPV) infections, including epigenetic factors. OBJECTIVES We hypothesised that p16 ink4a methylation might have a role in cancer development driven by HPV16, mainly in the presence of intact E1/E2 genes. Thus, our objectives were to assess the status of p16 ink4a methylation and the HPV16 E1/E2 integrity in samples in different stages of cervical diseases. METHODS Presence of HPV16 was determined by E6 type-specific polymerase chain reaction (PCR). Methylation status of the p16 ink4a promoter was assessed by methylation-specific PCR in 87 cervical specimens comprising 29 low-grade (LSIL), 41 high-grade (HSIL) lesions, and 17 cervical cancers (CC). Characterisation of E1 and E2 disruption (as an indirect indicator of the presence of episomal viral DNA) was performed by PCR amplifications. FINDINGS We observed a significantly increased trend (nptrend = 0.0320) in the proportion of methylated p16 ink4a in cervical samples during cancer development. Concomitant E1 and E2 disruptions were the most frequent pattern found in all groups: CC (76%), HSIL (54%), and LSIL (73%). No statistically significant differences between p16 ink4a methylation and E1/E2 integrity, in histological groups, was observed. MAIN CONCLUSIONS There was an increase in methylation of the p16 ink4a promoter from pre-neoplastic lesions to cancer. Additionally, a high frequency of E1/E2 disruptions in LSIL/HSIL suggested that viral DNA integration was an early event in cervical disease. Moreover, the methylation status was apparently independent of HPV16 integrity.
背景 宿主细胞中的表观遗传修饰，如p16 ink4a甲基化，已被视为癌症发展的潜在互补机制。由于只有一小部分受感染的女性会患上宫颈癌，其他因素可能独立或与高危型人乳头瘤病毒（HR-HPV）感染相关，参与致癌过程，包括表观遗传因素。目的 我们假设p16 ink4a甲基化可能在HPV16驱动的癌症发展中起作用，主要是在E1/E2基因完整的情况下。因此，我们的目的是评估不同宫颈疾病阶段样本中p16 ink4a甲基化状态和HPV16 E1/E2完整性。方法 通过E6型特异性聚合酶链反应（PCR）检测HPV16的存在。采用甲基化特异性PCR评估87例宫颈标本中p16 ink4a启动子的甲基化状态，其中包括29例低级别（LSIL）、41例高级别（HSIL）病变和17例宫颈癌（CC）。通过PCR扩增对E1和E2破坏（作为游离病毒DNA存在的间接指标）进行特征分析。结果 我们观察到在癌症发展过程中，宫颈样本中甲基化p16 ink4a的比例有显著增加趋势（nptrend = 0.0320）。E1和E2同时破坏是所有组中最常见的模式：CC组（76%）、HSIL组（54%）和LSIL组（73%）。在组织学组中，未观察到p16 ink4a甲基化与E1/E2完整性之间存在统计学显著差异。主要结论 从癌前病变到癌症，p16 ink4a启动子的甲基化增加。此外，LSIL/HSIL中E1/E2破坏的高频率表明病毒DNA整合是宫颈疾病的早期事件。而且，甲基化状态显然与HPV16完整性无关。
