Division of Monoclonal Antibodies, Center for Drug Evaluation and Research/Food and Drug Administration, Bethesda, Maryland, United States of America.
PLoS One. 2011;6(7):e21877. doi: 10.1371/journal.pone.0021877. Epub 2011 Jul 15.
p63 is critical for squamous epithelial development, and elevated levels of the ΔNp63α isoform are seen in squamous cell cancers of various organ sites. However, significant controversy exists regarding the role of p63 isoforms as oncoproteins or tumor suppressors. Here, lentiviruses were developed to drive long-term overexpression of ΔNp63α in primary keratinocytes. Elevated levels of ΔNp63α in vitro promote long-term survival and block both replicative and oncogene-induced senescence in primary keratinocytes, as evidenced by the expression of SA-β-gal and the presence of nuclear foci of heterochromatin protein 1γ. The contribution of ΔNp63α to cancer development was assessed using an in vivo grafting model of experimental skin tumorigenesis that allows distinction between benign and malignant tumors. Grafted lenti-ΔNp63α keratinocytes do not form tumors, whereas lenti-GFP/v-ras(Ha) keratinocytes develop well-differentiated papillomas. Lenti-ΔNp63α/v-ras(Ha) keratinocytes form undifferentiated carcinomas. The average volume of lenti-ΔNp63α/v-ras(Ha) tumors was significantly higher than those in the lenti-GFP/v-ras(Ha) group, consistent with increased BrdU incorporation detected by immunohistochemistry. The block in oncogene-induced senescence corresponds to sustained levels of E2F1 and phosphorylated AKT, and is associated with loss of induction of p16(ink4a)/p19(arf). The relevance of p16(ink4a)/p19(arf) loss was demonstrated in grafting studies of p19(arf)-null keratinocytes, which develop malignant carcinomas in the presence of v-ras(Ha) similar to those arising in wildtype keratinocytes that express lenti-ΔNp63α and v-ras(Ha). Our findings establish that ΔNp63α has oncogenic activity and its overexpression in human squamous cell carcinomas contributes to the malignant phenotype, and implicate its ability to regulate p16(ink4a)/p19(arf) in the process.
p63 对于鳞状上皮的发育至关重要，在各种器官部位的鳞状细胞癌中都可见到 ΔNp63α 同工型的水平升高。然而，p63 同工型作为癌蛋白或肿瘤抑制因子的作用仍存在很大争议。在这里，开发了慢病毒来驱动原代角质形成细胞中 ΔNp63α 的长期过表达。体外升高的 ΔNp63α 水平可促进原代角质形成细胞的长期存活，并阻断复制和致癌基因诱导的衰老，这表现在 SA-β-gal 的表达和异染色质蛋白 1γ 的核焦点的存在。通过实验性皮肤肿瘤发生的体内移植模型评估 ΔNp63α 对癌症发展的贡献，该模型允许区分良性和恶性肿瘤。移植 lenti-ΔNp63α 角质形成细胞不会形成肿瘤，而 lenti-GFP/v-ras(Ha) 角质形成细胞则形成分化良好的乳头瘤。Lenti-ΔNp63α/v-ras(Ha) 角质形成细胞形成未分化的癌。Lenti-ΔNp63α/v-ras(Ha) 肿瘤的平均体积明显高于 lenti-GFP/v-ras(Ha) 组，这与免疫组织化学检测到的 BrdU 掺入增加一致。致癌基因诱导的衰老受阻对应于 E2F1 和磷酸化 AKT 的持续水平，并与 p16(ink4a)/p19(arf) 的诱导缺失相关。p16(ink4a)/p19(arf) 缺失的相关性在 p19(arf)-null 角质形成细胞的移植研究中得到了证明，在 v-ras(Ha) 存在下，这些细胞类似于表达 lenti-ΔNp63α 和 v-ras(Ha) 的野生型角质形成细胞中出现的恶性癌，它们会发展为恶性癌。我们的研究结果表明，ΔNp63α 具有致癌活性，其在人类鳞状细胞癌中的过表达有助于恶性表型，并暗示其调节 p16(ink4a)/p19(arf) 的能力在该过程中。
