Comprehensive Analysis of Mouse Cancer/Testis Antigen Functions in Cancer Cells and Roles of TEKT5 in Cancer Cells and Testicular Germ Cells.

The cancer/testis antigen (CTA) genes were identified as human genes preferentially expressed in cancer cells and testis, but the contribution of CTAs to cancer and male germ cell development is unclear. In this study, we comprehensively examined mouse CTA functions and found that the majority of CTAs are involved in growth and/or survival of cancer cells. We focused on one mouse CTA gene, , for its detailed functional analysis. knockdown (KD) in ovarian cancer cells caused G arrest and apoptosis, and p27 was concomitantly upregulated. KD also resulted in decreased levels of acetylated α-tubulin and subsequent fragmentation of β-III-tubulin, upregulation of HDAC6 that deacetylates α-tubulin, and nuclear accumulation of SMAD3 that induces p27 expression. Because depolymerization of tubulin is known to cause translocation of SMAD3 to the nucleus, these results together suggested that TEKT5 negatively regulates expression and consequently maintains cell cycle via stabilization of tubulin. We also found that the number of spermatids was significantly decreased and acetylated α-tubulin levels were decreased by KD of in testis. Because acetylated α-tubulin is required for sperm morphogenesis, these results suggest that TEKT5 is necessary for spermiogenesis via maintenance of acetylated α-tubulin levels.