Kranjec Christian, Holleywood Christina, Libert Diane, Griffin Heather, Mahmood Radma, Isaacson Erin, Doorbar John
Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, UK.
The Francis Crick Institute Mill Hill Laboratory, The Ridgeway, Mill Hill, London, UK.
J Pathol. 2017 Aug;242(4):448-462. doi: 10.1002/path.4917.
In stratified epithelia such as the epidermis, homeostasis is maintained by the proliferation of cells in the lower epithelial layers and the concomitant loss of differentiated cells from the epithelial surface. These differentiating keratinocytes progressively stratify and form a self-regenerating multi-layered barrier that protects the underlying dermis. In such tissue, the continual loss and replacement of differentiated cells also limits the accumulation of oncogenic mutations within the tissue. Inactivating mutations in key driver genes, such as TP53 and NOTCH1, reduce the proportion of differentiating cells allowing for the long-term persistence of expanding mutant clones in the tissue. Here we show that through the expression of E6, HPV-16 prevents the early fate commitment of human keratinocytes towards differentiation and confers a strong growth advantage to human keratinocytes. When E6 is expressed either alone or with E7, it promotes keratinocyte proliferation at high cell densities, through the combined inactivation of p53 and Notch1. In organotypic raft culture, the activity of E6 is restricted to the basal layer of the epithelium and is enhanced during the progression from productive to abortive or transforming HPV-16 infection. Consistent with this, the expression of p53 and cleaved Notch1 becomes progressively more disrupted, and is associated with increased basal cell density and reduced commitment to differentiation. The expression of cleaved Notch1 is similarly disrupted also in HPV-16-positive cervical lesions, depending on neoplastic grade. When taken together, these data depict an important role of high-risk E6 in promoting the persistence of infected keratinocytes in the basal and parabasal layers through the inactivation of gene products that are commonly mutated in non-HPV-associated neoplastic squamous epithelia. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
在复层上皮组织如表皮中，内环境稳态通过上皮下层细胞的增殖以及上皮表面分化细胞的同步丢失来维持。这些分化的角质形成细胞逐渐分层，形成一个自我更新的多层屏障，保护下方的真皮。在这样的组织中，分化细胞的持续丢失和替换也限制了致癌突变在组织内的积累。关键驱动基因如TP53和NOTCH1的失活突变会减少分化细胞的比例，从而使扩展的突变克隆能够在组织中长期持续存在。在这里，我们表明，通过E6的表达，人乳头瘤病毒16型（HPV - 16）可阻止人类角质形成细胞早期向分化方向的命运决定，并赋予人类角质形成细胞强大的生长优势。当E6单独或与E7一起表达时，它通过使p53和Notch1共同失活，在高细胞密度下促进角质形成细胞增殖。在器官型筏培养中，E6的活性局限于上皮的基底层，并且在从生产性HPV - 16感染进展为流产性或转化性感染的过程中增强。与此一致的是，p53和切割的Notch1的表达逐渐受到更严重的破坏，并且与基底细胞密度增加和分化倾向降低相关。根据肿瘤分级，切割的Notch1的表达在HPV - 16阳性宫颈病变中也同样受到破坏。综上所述，这些数据表明高危型E6通过使在非HPV相关的肿瘤性鳞状上皮中常见突变的基因产物失活，在促进感染的角质形成细胞在基底层和副基底层持续存在方面发挥重要作用。© 2017作者。《病理学杂志》由约翰·威利父子有限公司代表大不列颠及爱尔兰病理学会出版。
