ECT2 (epithelial cell transforming 2) is a guanine nucleotide exchange factor (GEF) that activates Rho family GTPases including RHOA, RAC1, and CDC42 1. During normal cell division, ECT2 functions in cytokinesis as part of the centralspindlin complex, regulating myosin contractile ring formation 2. However, ECT2 exhibits oncogenic properties when overexpressed or mislocalized in cancer cells. In colorectal cancer, elevated ECT2 expression occurs early in adenomas and correlates with poor patient survival, particularly when nuclear localization is increased 3. ECT2 promotes cancer cell invasion and anchorage-independent growth independent of its cytokinesis function 3. In non-small cell lung cancer, ECT2 regulates ribosomal RNA synthesis and ribosome biogenesis, supporting transformed growth 4. ECT2 also mediates mesenchymal-amoeboid transition in astrocytoma cells through RAC1 and CDC42 activation 1. Additionally, cytoplasmic ECT2 promotes confined cell migration and invasion by recruiting to the plasma membrane and activating RhoA/myosin II signaling in response to mechanical confinement 5. ECT2 represents both a normal cytokinesis regulator and an important oncogenic driver across multiple cancer types.