A tumor-suppressing role of TSPYL2 in thyroid cancer: Through interacting with SIRT1 and repressing SIRT1/AKT pathway.

Thyroid cancer is one of the most common endocrine cancers. Testis-specific protein, Y-encoded-like 2 (TSPYL2) belongs to the TSPY family. Studies show that TSPYL2 plays as a cancer suppressor in several cancers. However, the role of TSPYL2 in thyroid cancer remains elusive. In the present study, the expression of TSPYL2 in human central papillary thyroid cancer (PTC) tissues and corresponding para-cancer tissues was detected by qPCR and Western blot. The gain- and loss-of-function studies for TSPYL2 were performed in TPC-1 cells and IHH-4 cells. The results showed that TSPYL2 expression was decreased in PTC tissues, and the low TSPYL2 expression was associated with more lymph node metastasis. Moreover, the results showed that knockdown of TSPYL2 promoted proliferation and enhanced the ability of migration and invasion of TPC-1 cells and IHH-4 cells, while TSPYL2 overexpression reversed it. TSPYL2 overexpression arrested cell cycle. We found that TSPYL2 silencing suppressed cell apoptosis, while overexpression of TSPYL2 reversed it. Co-IP results illustrated that TSPYL2 interacted with SIRT1. Knockdown of TSPYL2 increased the association between SIRT1 and AKT. Moreover, TSPYL2 expression inhibited AKT activation by upregulating the AKT acetylation level. In vivo, tumor xenograft experiments indicated that TSPYL2 suppressed the tumorigenic ability of thyroid cancer cells. Western blot results suggested that knockdown of TSPYL2 enhanced the phosphorylation level of AKT, while TSPYL2 overexpression reversed it. Taken together, our study suggested TSPYL2 could be a tumor suppressor in thyroid cancer by regulating SIRT1/AKT pathway.