The class I homeobox (HOX) family of homeodomain-containing transcription factors has 39 members in mammals. These genes are distributed throughout the genome in four clusters: HOXA (7p15), HOXB (17q21), HOXC (12q13), and HOXD (2q31). HOX genes are known to act as transcription factors, playing an essential regulatory role in the temporal and spatial development of the embryo. HOXC family members are not expressed in normal prostate tissue but increased expression of HOXC genes is commonly detected in prostate cancers. HOXC4 is expressed in GC B cells and HoxC4 expression is specifically up-regulated by the same stimuli that induce AID expression (LPS, CD154 and IL-4). The calculated molecular weight of HOXC4 is 30 kDa. Sometimes higher molecular weight around 39 kDa can also be observed, which may be a modified variant of HOXC4 (PMID: 23178148, 32012197, 35400027).