CBFβ-SMMHC is a fusion protein resulting from the fusion of the Core Binding Factor β subunit (CBFβ) and the Smooth Muscle Myosin Heavy Chain (SMMHC) genes, commonly found in patients with Acute Myeloid Leukemia (AML). This fusion protein is located in the cell nucleus and disrupts the normal differentiation process of blood cells by inhibiting the normal function of CBF. The primary biological reaction involving CBFβ-SMMHC is the proliferation of leukemia cells, caused by inhibiting the signaling pathways for blood cell differentiation. Gene-specific expression and related mutations are often associated with certain types of AML, playing a significant role in the diagnosis and treatment of leukemia.