Phosphorylation of FOXP3 by LCK Downregulates MMP9 Expression and Represses Cell Invasion

Abstract

Forkhead Box P3 (FOXP3) is a member of the forkhead/winged helix family of the transcription factors and plays an important role not only as a master gene in T-regulatory cells, but also as a tumor suppressor. In this study, we identified lymphocyte-specific protein tyrosine kinase (LCK), which correlates with cancer malignancy, as a binding partner of FOXP3. FOXP3 downregulated LCK-induced MMP9, SKP2, and VEGF-A expression. We observed that LCK phosphorylated Tyr-342 of FOXP3 by immunoprecipitation and in vitro kinase assay, and the replacement of Tyr-342 with phenylalanine (Y342F) abolished the ability to suppress MMP9 expression. Although FOXP3 decreased the invasive ability induced by LCK in MCF-7 cells, Y342F mutation in FOXP3 diminished this suppressive effect. Thus we demonstrate for the first time that LCK upregulates FOXP3 by tyrosine phosphorylation, resulting in decreased MMP9, SKP2, and VEGF-A expression, and suppressed cellular invasion. We consider that further clarification of transcriptional mechanism of FOXP3 may facilitate the development of novel therapeutic approaches to suppress cancer malignancy.

Calycosin Inhibits the Migration and Invasion of Human Breast Cancer Cells by Down-Regulation of Foxp3 Expression

“…Previous studies have linked Foxp3 expression to the VEGF and MMP-9 signaling molecules that play important role in invasion and metastasis of malignant tumors [18]. We here found that the mRNA and protein levels of VEGF and MMP-9 were also dose-dependently reduced by calycosin in breast cancer cells MCF-7 and T47D, consistent with the decreased Foxp3 expression pattern ( p < 0.05 or p < 0.01, Fig.…”

“…It has been shown that Foxp3 is highly expressed in ER-positive breast cancer cells, and the high expression levels in breast cancer tissues are positively associated with histological grades and metastasis [16, 17]. Meanwhile, Foxp3 is proved to regulate vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) expression in MCF-7 cells [18]. In particularly, down-regulation of Foxp3 was reported to inhibit invasion of cholangiocarcinoma cell lines by reducing the levels of MMP-9 and MMP-2 [19].…”

FOXP3 Controls an miR-146/NF-κB Negative Feedback Loop That Inhibits Apoptosis in Breast Cancer Cells

“…Interestingly, when compared with the expression levels of miR-146a/b in MCF10A normal breast epithelial cells, the expression levels are low in less invasive breast cancer cell lines such as MCF7 and T47D and high in more invasive breast cancer cell lines such as MDA-MB-231 (4, 5, 31), suggesting miR-146a/b functions may be lost in tumor development but not in tumor metastasis. In contrast, the expression levels of CXCR4 and MMP9 , which promote tumor metastasis, were dramatically reduced by FOXP3 in MCF7 cells (40, 41). CXCR4 has been reported as a potential target of miR-146a (11), but miR-146a did not contribute to the FOXP3-induced regulation of CXCR4 in MCF7 cells.…”

Pim-2 Kinase Influences Regulatory T Cell Function and Stability by Mediating Foxp3 Protein N-terminal Phosphorylation

“…Protein phosphorylation is a common posttranslational modification to regulate signal transduction pathways and cellular processes. It has been reported that Foxp3 could be phosphorylated by cyclin-dependent kinase 2 (CDK2) and lymphocyte-specific protein tyrosine kinase (Lck) (18,34). Additionally, PIM1 kinase negatively regulates human FOXP3 activity through phosphorylating its C-terminal serine 422 residue (25).…”