Krüppel-like factor 4 (KLF4) is a C2H2 zinc-finger transcription factor known to regulate multiple cellular processes including cell proliferation, differentiation and stemness. Cell scattering is characterized by disruption of E-cadherin-mediated intercellular adhesion and acquisition of fibroblast-like morphology with increased motility and invasiveness, a cellular process reminiscent of epithelial-to-mesenchymal transition (EMT). We have previously demonstrated the involvement of KLF4 in hepatocyte growth factor (HGF)-induced cell scattering (Lai et al., J. Cell Sci., in press). Still, the question as to whether KLF4 is generally involved in cell-scattered response induced by other stimuli such as 12-O-Tetradecanoylphorbol-13-Acetate (TPA) has never been formerly addressed and thus the main focus of this study. Using human hepatocellular carcinoma cell line HepG2 as the cellular model, we herein presented evidence that KLF4 was clearly up-regulated following TPA stimulation. RT-PCR analysis and luciferase reporter assay revealed that both the mRNA and promoter activity of KLF4 was markedly increased by TPA, indicating that TPA up-regulated KLF4 at the level of transcription. Of note, knockdown of KLF4 severely impaired the level of TPA-induced HepG2 cell scattering, highlighting the requirement of KLF4 in TPA-induced scattered response. Additionally, we found that the promoting effect of TPA on KLF4 expression was clearly blocked when cells were pre-treated with the pan-PKC inhibitor Gö6983 as well as the PKCα-specific inhibitor Gö6976. Likewise, TPA-induced cell scattering and KLF4 up-regulation were ablated when ERK activity was inhibited by U0126. Taken together, our results defined the involvement of KLF4 in TPA-induced cell scattered response. Particularly, TPA engages the PKCα-ERK signaling axis to induce transcriptional up-regulation of KLF4, leading to the initiation of cell scattering. Our findings further implicate the possible involvement of KLF4 in other TPA-induced cellular responses such as cell migration and invasion.
Citation Format: Jun-Kai Lai, Han-Chung Wu, Chia-Che Chang. 12-O-tetradecanoylphorbol-13-acetate (TPA) induces cell scattering by upregulating krüppel-like factor 4 (KLF4) through the PKCα-ERK signaling axis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 296. doi:10.1158/1538-7445.AM2013-296