Upregulated SPAG6 correlates with increased STAT1 and is associated with reduced sensitivity of interferon‐α response in BCR::ABL1 negative myeloproliferative neoplasms

Sperm‐associated antigen 6 (SPAG6) has been identified as an oncogene or tumor suppressor in various types of human cancer. However, the role of SPAG6 in BCR::ABL1 negative myeloproliferative neoplasms (MPNs) remains unclear. Herein, we found that SPAG6 was upregulated at the mRNA level in primary MPN cells and MPN‐derived leukemia cell lines. The SPAG6 protein was primarily located in the cytoplasm around the nucleus and positively correlated with β‐tubulin expression. In vitro, forced expression of SPAG6 increased cell clone formation and promoted G(1) to S cell cycle progression. Downregulation of SPAG6 promoted apoptosis, reduced G(1) to S phase transition, and impaired cell proliferation and cytokine release accompanied by downregulated signal transducer and activator of transcription 1 (STAT1) expression. Furthermore, the inhibitory effect of interferon‐α (INF‐α) on the primary MPN cells with high SPAG6 expression was decreased. Downregulation of SPAG6 enhanced STAT1 induction, thus enhancing the proapoptotic and cell cycle arrest effects of INF‐α both in vitro and in vivo. Finally, a decrease in SPAG6 protein expression was noted when the STAT1 signaling was blocked. Chromatin immunoprecipitation assays indicated that STAT1 protein could bind to the SPAG6 promoter, while the dual‐luciferase reporter assay indicated that STAT1 could promote the expression of SPAG6. Our results substantiate the relationship between upregulated SPAG6, increased STAT1, and reduced sensitivity to INF‐α response in MPN.