Given that the N-terminal region of PTEN is essential for controlling the cytoplasmic localization and activity of PTEN 15, 16 and that PTEN and FGD1 were mutually exclusively in sarcoma patient samples (Figure S5A), we wondered whether FGD1 inhibits the function of PTEN in osteosarcoma cells. The gene discussed is PTEN; the disease is sarcoma.