The extracellular domain (AA 127–524) of CKAP4 is required for antiproliferative factor (APF) binding, which suggests that targeting this special region of CKAP4 to inhibit APF binding may be an effective strategy for the treatment of interstitial cystitis related to bladder pathology (Chavda et al., 2017). This evidence concerns the gene CKAP4 and interstitial cystitis.