Department of Clinical and Molecular Medicine, Sapienza University of Rome, Laboratory Affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Viale Regina Elena 324, 00161, Rome, Italy.
S. Andrea University Hospital, Rome, Italy.
Cell Commun Signal. 2020 May 19;18(1):76. doi: 10.1186/s12964-020-00582-1.
The epithelial isoform of the fibroblast growth factor receptor 2 (FGFR2b) controls the entire program of keratinocyte differentiation via the sequential involvement of protein kinase C (PKC) δ and PKCα. In contrast, the FGFR2 isoform switch and the aberrant expression of the mesenchymal FGFR2c isoform leads to impairment of differentiation, epithelial-mesenchymal transition (EMT) and tumorigenic features. Aim of our present study was to contribute in clarifying the complex network of signaling pathways involved in the FGFR2c-mediated oncogenic outcomes focusing on PKCε, which appears to be involved in the induction of EMT and tumorigenesis in several epithelial contexts.
Biochemical and molecular analysis, as well as in vitro invasion assays, combined with the use of specific small interfering RNA (siRNA), were performed in human keratinocytes stably expressing FGFR2c or FGFR2b isoforms.
Our results showed that aberrant expression and signaling of FGFR2c, but not those of FGFR2b, in human keratinocytes induced a strong phosphorylation/activation of PKCε. The use of siRNA approach showed that PKCε is the hub signaling downstream FGFR2c responsible for the modulation of EMT markers and for the induction of the EMT-related transcription factors STAT3, Snail1 and FRA1, as well as for the acquisition of the invasive behavior. Moreover, experiments of depletion of ESRP1, responsible for FGFR2 splicing in epithelial cells, indicated that the activation of PKCε is the key molecular event triggered by FGFR2 isoform switch and underlying EMT induction.
Overall, our results point to the identification of the downstream PKC isoform responsible for the FGFR signaling deregulation occurring in epithelial tissues from the physiological oncosoppressive to the pathological oncogenic profile. Video Abstract.
成纤维细胞生长因子受体 2（FGFR2）的上皮同工型通过蛋白激酶 C（PKC）δ和 PKCα的顺序参与控制角质形成细胞分化的整个程序。相比之下，FGFR2 同工型转换和间质 FGFR2c 同工型的异常表达导致分化受损、上皮-间质转化（EMT）和致瘤特征。我们目前研究的目的是阐明参与 FGFR2c 介导的致癌结果的信号通路的复杂网络，重点关注 PKCε，PKCε 似乎参与了几种上皮背景下 EMT 和肿瘤发生的诱导。
在稳定表达 FGFR2c 或 FGFR2b 同工型的人角质形成细胞中进行生化和分子分析以及体外侵袭测定，并结合使用特异性小干扰 RNA（siRNA）。
我们的结果表明，人角质形成细胞中 FGFR2c 的异常表达和信号转导而非 FGFR2b 的异常表达诱导了 PKCε 的强烈磷酸化/激活。使用 siRNA 方法表明，PKCε 是负责 EMT 标志物调节和 EMT 相关转录因子 STAT3、Snail1 和 FRA1 诱导以及侵袭行为获得的 FGFR2c 下游信号枢纽。此外，ESRP1 耗竭实验表明，FGFR2 剪接在上皮细胞中负责 ESRP1，该实验表明 PKCε 的激活是 FGFR 同工型转换触发的关键分子事件，也是 EMT 诱导的基础。
总体而言，我们的结果表明，已经确定了负责发生在生理抗肿瘤到病理致癌谱的上皮组织中 FGFR 信号失调的下游 PKC 同工型。视频摘要。
