Loss of neural crest-associated gene FOXD1 impairs melanoma invasion and migration via RAC1B downregulation

Recent studies suggest that malignant melanoma heterogeneity includes subpopulations of cells with features of multipotent neural crest (NC) cells. Zebrafish and mouse models have shown that reactivation of neural crest-specific pathways determines the invasiveness of melanoma cells. In this study, we show that the neural crest-associated transcription factor FOXD1 plays a key role in invasion and migration capacity of metastatic melanomas both in vivo and in vitro. Gene expression profiling analysis identified on one hand, an upregulation of FOXD1 in NC and melanoma cells, and on the other hand, a downregulation of several genes related to cell invasion in FOXD1 knockdown cells, including MMP9 and RAC1B. Furthermore, we demonstrate that knockdown of RAC1B a tumor-specific isoform of RAC1, significantly impaired cell migration and invasion in melanoma and could abrogate enhanced invasiveness induced by FOXD1 overexpression. We conclude that FOXD1 may influence invasion and migration via indirect regulation of MMP9 and RAC1B alternative splicing in melanoma cells. mRNA isolated from NHM, D1, D1NC, HT144, MZ7, A375, MeWo, SK-NL-SETDB1, SKmel103 [GSM3039499-GSM3039504] Matrix 1: gene expression comparison between neural crest and hiPSC (related to Figure 1D). [GSM3039505-GSM3039513] Matrix 2: gene expression comparison between melanoma lines and NHM (related to Figure 1D). [GSM3039514-GSM3039528] Matrix 3: gene expression comparison between FOXD1 silenced cell lines and Control cell lines (related to Figure S4).