PTEN and cancer: Most importantly, our group have found SUMOylation has been linked to cancer initiation and development, for examples, SUMOylation of tumor suppressors PTEN [12], Egr1 [13] and oncogenic protein Grb2 [14] regulate tumorigenesis; SUMOylation of RhoGDI (Rho GDP-dissociation inhibitor) enhances cancer cell motility [15].