CD99 and osteosarcoma: In addition, the forced expression of CD99wt in osteosarcoma cells induced the downregulation of genes involved in actin cytoskeleton remodeling and cell invasion, such as actin-related protein 2 homologue (yeast) (ACTR2) and actin-related protein 2/3 complex, subunit 1A (ARPC1A) [55]; furthermore CD99 forced expression increased MAPK/ERK signaling, favoring the recruitment of activated ERK to the cell membrane/cytoplasm.