APC is a tumor suppressor protein that functions as a negative regulator of Wnt/β-catenin signaling by promoting rapid degradation of β-catenin (CTNNB1) 1. The protein operates as a core component of the β-catenin destruction complex, where AXIN1 polymerization and APC facilitate β-catenin capture, phosphorylation, and ubiquitylation for proteasomal degradation 1. APC also interacts directly with the SCFβ-TrCP E3 ligase complex to limit ubiquitylation processivity and regulate β-catenin flux through the destruction complex 1. Beyond Wnt signaling, APC binds microtubules and actin filaments, functions downstream of Rho GTPases to stabilize microtubules at the cell cortex, and mediates ERBB2-dependent microtubule stabilization [UniProt]. APC dysregulation occurs through multiple mechanisms: METTL3-mediated m6A modification recruits YTHDF for APC mRNA degradation, leading to β-catenin accumulation and enhanced cell proliferation in esophageal cancer 2. APC mutations, particularly within the mutation cluster region (codons 1200-1500), correlate with chr5 instability and aneuploidy in colorectal adenomas 3. Loss-of-function APC mutations cause familial adenomatous polyposis and supernumerary tooth formation through Wnt/β-catenin pathway hyperactivation 4. Oncogenic APC truncations retain partial function but are impaired in destruction complex efficiency 1. APC mutations appear in colorectal, gastric, and pancreatic carcinomas 5.