Acid calponin is an actin filament?associated regulatory protein expressed in smooth muscle and non?muscle cells. The roles of acid calponin in regulating dendritic spine remodeling, cytoskeletal rearrangement, smooth muscle contraction, skeletal muscle development, placentation processes, embryonic development, and signal transduction have been investigated extensively. These roles indicate that changes in acid calponin expression are related to the occurrence and development of drug?resistant epilepsy, colorectal cancer, mucosa?associated lymphoid tissue lymphoma, and ovarian cancer, which are significant for diagnosis and prognosis.