MAP4 is a non-neuronal microtubule-associated protein that promotes microtubule assembly and stabilization 1. As a key regulator of microtubule dynamics, MAP4 functions in critical cellular processes including cell division, spindle organization, and establishment of spindle orientation 1. MAP4 exhibits microtubule-stabilizing activity and participates in microtubule cytoskeleton organization through its interaction with tubulin and microtubule polymers 1. The protein's activity is regulated through phosphorylation; ARID1A loss increases MAP4 phosphorylation via PI3K activation, which attenuates its microtubule-stabilizing capacity and creates cellular vulnerability to antimicrotubule chemotherapy drugs like estramustine phosphate 2. In disease contexts, MAP4 is significantly upregulated in lung adenocarcinoma compared to normal tissue, where high expression correlates with poor overall survival and promotes cancer cell migration and invasion through epithelial-mesenchymal transition (EMT) 3. MAP4 participates in radiation resistance in lung adenocarcinoma by regulating radiation-induced EMT processes, suggesting it serves as both a prognostic biomarker and therapeutic target 3. Unlike MAP7, which modulates tubulin posttranslational modifications in response to osmotic stress, MAP4 association remains relatively constant under varying cytoplasmic density conditions 4.