Blimp-1 Upregulation by Multiple Ligands via EGFR Transactivation Inhibits Cell Migration in Keratinocytes and Squamous Cell Carcinoma.

Hyemin Lee,Wan-Wan Lin,Duen-Yi Huang,Wan-Yu Ren,Hua-Ching Chang,Chia-Yee Lin,Yang-Shia Dai

doi:10.3389/fphar.2022.763678

Abstract

B lymphocyte-induced maturation protein-1 (Blimp-1) is a transcriptional repressor and plays a crucial role in the regulation of development and functions of various immune cells. Currently, there is limited understanding about the regulation of Blimp-1 expression and cellular functions in keratinocytes and cancer cells. Previously we demonstrated that EGF can upregulate Blimp-1 gene expression in keratinocytes, playing a negative role in regulation of cell migration and inflammation. Because it remains unclear if Blimp-1 can be regulated by other stimuli beyond EGF, here we further investigated multiple stimuli for their regulation of Blimp-1 expression in keratinocytes and squamous cell carcinoma (SCC). We found that PMA, TNF-α, LPS, polyIC, H2O2 and UVB can upregulate the protein and/or mRNA levels of Blimp-1 in HaCaT and SCC cells. Concomitant EGFR activation was observed by these stimuli, and EGFR inhibitor gefitinib and Syk inhibitor can block Blimp-1 gene expression caused by PMA. Reporter assay of Blimp-1 promoter activity further indicated the involvement of AP-1 in PMA-, TNF-α-, LPS- and EGF-elicited Blimp-1 mRNA expression. Confocal microscopic data indicated the nuclear loclization of Blimp-1, and such localization was not changed by stimuli. Moreover, Blimp-1 silencing enhanced SCC cell migration. Taken together, Blimp-1 can be transcriptionally upregulated by several stimuli in keratinocytes and SCC via EGFR transactivation and AP-1 pathway. These include growth factor PMA, cytokine TNF-α, TLR ligands (LPS and polyIC), and ROS insults (H2O2 and UVB). The function of Blimp-1 as a negative regulator of cell migration in SCC can provide a new therapeutic target in SCC.

Highlights

B lymphocyte-induced maturation protein-1 (Blimp-1) encoded by the PRDM1 gene is a member of PRDM family
We found that LPS (1 μg/ml) (Figure 1A), phorbol 12-myristate 13-acetate (PMA) (30 nM), tumor necrotic factor-α (TNF-α) (10 ng/ml) and H2O2 (200 μM) (Figure 1B) can increase Blimp-1 protein expression
After stimulation cell lysates were collected to determine Blimp-1 and β-actin expression by immunoblotting. (D) HaCaT cells were stimulated with PMA (30 nM), TNF-α (10 ng/ml), LPS (1 μg/ml), or UVB at 50 mJ/cm2 for indicated time periods and quantitative polymerase chain reaction (Q-PCR) was performed to evaluate the mRNA level of Blimp-1. *p < 0.05 as compared to control group

Summary

Introduction

B lymphocyte-induced maturation protein-1 (Blimp-1) encoded by the PRDM1 gene is a member of PRDM family. Blimp-1 is a transcriptional repressor that can regulate cell growth and differentiation. Several studies have demonstrated the pathways to regulate Blimp-1 expression, in particular in lymphocytes. In this context, IL-21 and IL-23 which are crucial for lymphocytes differentiation and functions have been demonstrated to induce Blimp-1 expression (Ozaki et al, 2004; Jain et al, 2016). Blimp-1 can undergo lysosomal degradation in keratinocytes (Chang et al, 2018)

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Conclusion