TEKT5 (tektin 5) is a sperm-specific microtubule inner protein (MIP) that forms part of the dynein-decorated doublet microtubules in the flagellar axoneme 1. It interacts extensively with other tektin proteins to anchor the tektin bundle onto the A-tubule of the sperm flagellum, reinforcing the helical microtubule structure essential for flagellar function [UniProt annotation supported by 29]. Beyond its canonical role in spermiogenesis, TEKT5 functions as a cancer/testis antigen with expression restricted to testis in normal tissues but aberrantly expressed in multiple malignancies including colon, ovarian, and lung cancers 3. In cancer cells, TEKT5 regulates cell cycle progression by negatively regulating HDAC6 expression, thereby maintaining acetylated α-tubulin levels and preventing SMAD3-mediated p27kip1 upregulation and G1 arrest 1. TEKT5 knockdown in ovarian cancer cells triggers apoptosis and decreased acetylated α-tubulin with subsequent tubulin fragmentation 1. In testicular tissue, TEKT5 maintains spermatid numbers and acetylated α-tubulin levels necessary for proper sperm morphogenesis 1. Clinically, TEKT5 demonstrates immunogenicity with detectable antibodies in cancer patients 3 and has been identified as a candidate biomarker for male infertility assessment 4. GWAS studies suggest potential sex-dimorphic effects on coronary artery disease mortality outcomes 5. These findings support TEKT5's potential as both a diagnostic and immunotherapeutic target in cancer.