MTSS1 and cancer: As β-TRCP is the first identified E3 ligase for MTSS1, to explore the biological significance for SCFβ-TRCP-mediated destruction of MTSS1, next we intended to examine how ectopic expression of a non-degradable mutant form of MTSS1 (S322A-MTSS1) or wild-type MTSS1 (as a control) in both PC3 and MDA-MB-231 cancer cells could affect cellular migration or proliferation (Supplementary Figure S4A-B).