背景:低危人乳头瘤病毒(HPV),如6型和11型,被认为是非致癌的,但是这些类型已经在口腔癌组织样本中检测到,提示它们可能参与口腔癌的发生。因为已知高风险HPV和EB病毒(EBV)的双重感染与口腔癌的发生有关,我们假设低危型HPV和EBV共感染可以转化口腔细胞.为了验证我们的假设,我们评估了同时表达低风险HPVE6/E7和EBVLMP-1的细胞系的转化活性。
方法:我们将HPV6、11和16E6/E7基因和EBVLMP-1基因转导到原代小鼠胚胎成纤维细胞中。检查细胞系的转化活性指标,如增殖,诱导DNA损伤,抗凋亡,锚定独立生长,和裸鼠中的肿瘤形成。为了评估转化中涉及的信号通路,分析NF-κB和p53活性。我们还评估了与锚定非依赖性生长相关的黏附信号分子,例如MMP-2,桩蛋白和Cat-1。
结果:低风险HPV6E6和EBVLMP-1的共表达显示细胞增殖增加,NF-κB活性升高和p53诱导减少。此外,共表达低风险HPV6E6和EBVLMP-1诱导DNA损伤,在基因毒性条件下逃避细胞凋亡和抑制DNA损伤反应(DDR)。低风险HPV11E6/E7和EBVLMP-1的共表达显示出相似的结果。然而,它没有导致恶性特征,如锚定非依赖性生长,裸鼠的侵袭力和肿瘤形成。与共表达高危HPV16E6和EBVLMP-1诱导转化的细胞相比,低危HPV6E6和EBVLMP-1的共表达与低MMP-2、桩蛋白和Cat-1表达相关。
结论:低危型HPVE6/E7和EBVLMP-1的共表达不诱导恶性转化,但它允许继发于DNA损伤增加和DDR抑制的体细胞突变的积累。因此,低危型HPV和EBV双重感染可导致癌前病变。
BACKGROUND: Low-risk human papillomavirus (HPV), such as types 6 and 11, is considered non-oncogenic, but these types have been detected in oral cancer tissue samples, suggesting their possible involvement in oral carcinogenesis. Because double infection of high-risk HPV and Epstein-Barr virus (EBV) is known to be involved in oral carcinogenesis, we hypothesized that low-risk HPV and EBV co-infection can transform the oral cells. To verify our hypothesis, we evaluated the transformation activity of cell lines expressing both low-risk HPV E6/E7 and EBV LMP-1.
METHODS: We transduced HPV6, 11 and 16 E6/E7 genes and EBV LMP-1 gene into primary mouse embryonic fibroblasts. The cell lines were examined for indices of transformation activity such as proliferation, induction of DNA damage, resistance to apoptosis, anchorage-independent growth, and tumor formation in nude mice. To evaluate the signaling pathways involved in transformation, NF-κB and p53 activities were analyzed. We also assessed adhesion signaling molecules associated with anchorage-independent growth such as MMP-2, paxillin and Cat-1.
RESULTS: Co-expression of low-risk HPV6 E6 and EBV LMP-1 showed increased cell proliferation, elevated NF-κB activity and reduced p53 induction. Moreover, co-expression of low-risk HPV6 E6 and EBV LMP-1 induced DNA damage, escaped from apoptosis under genotoxic condition and suppression of DNA damage response (DDR). Co-expression of low-risk HPV11 E6/E7 and EBV LMP-1 demonstrated similar results. However, it led to no malignant characteristics such as anchorage-independent growth, invasiveness and tumor formation in nude mice. Compared with the cells co-expressing high-risk HPV16 E6 and EBV LMP-1 that induce transformation, co-expression of low-risk HPV6 E6 and EBV LMP-1 was associated with low MMP-2, paxillin and Cat-1 expression.
CONCLUSIONS: The co-expression of low-risk HPV E6/E7 and EBV LMP-1 does not induce malignant transformation, but it allows accumulation of somatic mutations secondary to increased DNA damage and suppression of DDR. Thus, double infection of low-risk HPV and EBV could lead to precancerous lesions.