MFN1 and osteosarcoma: Mitofusin 1 (Mfn1) when phosphorylated by ERK1/2 inhibits mitochondrial fusion [73] while mitofusin 2 (Mfn2) when phosphorylated by JNK becomes a substrate for the proteasome and promotes the fragmentation of mitochondria in human osteosarcoma cells [74].