Based on limited published evidence, TMSB15B (thymosin beta 15B) is an actin-binding protein involved in cell migration regulation. Database annotations indicate it functions in positive regulation of cell migration through actin monomer binding and protein sequestering activity [GO terms]. TMSB15B represents a distinct gene paralog of thymosin beta 15, with tissue-specific expression patterns differing from TMSB15A 1. It is predominantly expressed in colon tissue and certain cancer cell lines, and its knockdown suppresses prostate cancer cell migration, suggesting a functional role in tumor cell motility 1. Unlike TMSB15A, TMSB15B expression is not repressed by transforming growth factor beta 1 1.