Molecular Biology Program, Cardinal Bernardin Cancer Center, the Stritch School of Medicine, Department of Pathology, Room 304, Loyola University Medical Center, 2160 S First Avenue, Maywood, IL 60153, USA.
Am J Pathol. 2010 Mar;176(3):1091-6. doi: 10.2353/ajpath.2010.090816. Epub 2010 Jan 21.
Protein kinase C delta (PKC-delta) protein levels are frequently low in chemically and UV-induced mouse skin tumors as well as in human cutaneous squamous cell carcinomas (SCCs). Furthermore, overexpression of PKC-delta in human SCC lines and mouse epidermis is sufficient to induce apoptosis and suppress tumorigenicity, making PKC-delta a potential tumor suppressor gene for SCCs. Here we report that PKC-delta is lost in human SCCs at the transcriptional level. We used laser capture microdissection to isolate cells from three normal human epidermis and 14 human SCCs with low PKC-delta protein. Analysis by quantitative reverse transcription-PCR revealed that PKC-delta RNA was reduced an average of 90% in the SCCs tested, consistent with PKC-delta down-regulation at the protein level. Analysis of DNA from nine of the same tumors revealed that PKC-delta gene was deleted in only one tumor. In addition, Ras-transformed human keratinocytes, which have selective down-regulation of PKC-delta at both protein and mRNA levels, had significantly repressed human PKC-delta promoter activity. Together, these results indicate that PKC-delta gene expression is suppressed in human SCCs, probably via transcription repression. Our results have implications for the development of topical therapeutic strategies to trigger the re-expression of pro-apoptotic PKC-delta to induce apoptosis in SCCs.
蛋白激酶 C 三角洲（PKC-delta）蛋白水平在化学诱导和 UV 诱导的小鼠皮肤肿瘤以及人类皮肤鳞状细胞癌（SCC）中经常降低。此外，PKC-delta 在人类 SCC 系和小鼠表皮中的过表达足以诱导细胞凋亡并抑制肿瘤发生，这使得 PKC-delta 成为 SCC 的潜在肿瘤抑制基因。在这里，我们报告 PKC-delta 在人类 SCC 中在转录水平上丢失。我们使用激光捕获显微切割技术从三个正常人类表皮和 14 个 PKC-delta 蛋白水平低的人类 SCC 中分离细胞。通过定量逆转录-PCR 分析表明，在测试的 SCC 中 PKC-delta RNA 平均降低了 90%，与蛋白质水平的 PKC-delta 下调一致。对来自九个相同肿瘤的 DNA 的分析表明，PKC-delta 基因仅在一个肿瘤中缺失。此外，Ras 转化的人角质形成细胞在蛋白质和 mRNA 水平上选择性地下调 PKC-delta，其显著抑制了人 PKC-delta 启动子活性。这些结果表明，PKC-delta 基因表达在人类 SCC 中受到抑制，可能通过转录抑制。我们的研究结果为开发局部治疗策略以触发促凋亡 PKC-delta 的再表达以诱导 SCC 细胞凋亡提供了依据。
