Abstract
The transcription factor FOXO3 is associated with poor outcome in high-stage neuroblastoma (NB), as it facilitates chemoprotection and tumor angiogenesis. In other tumor entities, FOXO3 stimulates metastasis formation, one of the biggest challenges in the treatment of aggressive NB. However, the impact of FOXO3 on the metastatic potential of neuronal tumor cells remains largely unknown. In the present study, we uncover the small leucine-rich proteoglycan family member lumican (LUM) as a FOXO3-regulated gene that stimulates cellular migration in NB. By a drug-library screen we identified the small molecular weight compound repaglinide (RPG) as a putative FOXO3 inhibitor. Here, we verify that RPG binds to the FOXO3-DNA-binding-domain (DBD) and thereby silences the transcriptional activity of FOXO3. Consistent with the concept that the FOXO3/LUM axis enhances the migratory capacity of aggressive NB cells, we demonstrate that stable knockdown of LUM abrogates the FOXO3-mediated increase in cellular migration. Importantly, FOXO3 inhibition by RPG represses the binding of FOXO3 to the LUM promoter, inhibits FOXO3-mediated LUM RNA and protein expression, and efficiently abrogates FOXO3-triggered cellular “wound healing” as well as spheroid-based 3D-migration. Thus, silencing the FOXO3/LUM axis by the FDA-approved compound RPG represents a promising strategy for novel therapeutic interventions in NB and other FOXO3-dependent tumors.
Highlights
Neuroblastoma (NB) is a pediatric tumor of the sympathetic nervous system that covers a broad spectrum of clinical outcomes
RPG dose-dependently interacted with the recombinant FOXO3-DBD protein, as determined by an Fluorescence polarization assay (FPA) experiment using the fluorophore-labeled oligonucleotide containing the insulin response element (IRE)
MMP-13 in breast cancer cells activity and elevated we investigated the impact of FOXO3 on MMP-9 and MMP-13 promoter activity in the aggressive invasion/migration capacity has been reported in glioma [15], in gastric cancer [16], and in colorectal cancer [3]
Summary
Neuroblastoma (NB) is a pediatric tumor of the sympathetic nervous system that covers a broad spectrum of clinical outcomes. Cells 2020, 9, 1 studies indicate that active FOXO3 promotes tumor angiogenesis in vivo [11] and chemoprotection in vitro [12] in high-stage NB. Rehman et al demonstrated that FOXO3 promotes tumor cell migration and may serve as a prognostic biomarker and a potential therapeutic target for breast cancer [14]. Storz et al found that FOXO3 promotes breast cancer cell invasion through the induction of matrix metalloproteinases 9 and 13 (MMP-9 and MMP-13) [4]. FOXO3 has further been associated with MMP-9 activity and elevated invasion capacity in glioma [15], with increased cell migration and invasion in gastric [16] and colorectal cancers [3]. FOXO3-knockdown attenuates tumor growth and metastasis formation in pancreatic ductal carcinoma and in glioblastoma xenografts [8,9]
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