SREBF1-mediated SND1 transcriptional activation promotes prostate cancer progression via MTDH interaction through the SESN2/AMPK/mTOR axis.

[BACKGROUND] Prostate cancer (PCa) is a prevalent cancer and a major cause of cancer-related deaths in men worldwide. Growing evidence indicates that Staphylococcal nuclease and Tudor domain containing 1 (SND1) is a multifunctional protein extensively involved in transcriptional regulation, RNA maturation, post-transcriptional modifications, and other processes. However, previous studies have rarely investigated the function of SND1 as an RNA-binding protein in PCa tumorigenesis.

[METHODS] The Cancer Genome Atlas and NCBI Gene Expression Omnibus (GEO) databases were used to evaluate SND1 expression levels in PCa. We conducted a series of in vitro and in vivo functional experiments to assess the biological functions of SND1, including cell counting kit-8, colony formation, Transwell and wound-healing assays, and animal experiments in nude mice. Chromatin immunoprecipitation, dual-luciferase reporter assay, and DNA pull-down assay were performed to validate the association between the upstream transcription factor and SND1. Based on mass spectrometry, RNA-seq, and RNA immunoprecipitation (RIP)-seq, we identified the downstream targets of SND1- Sestrin 2 (SESN2), which were validated through qRT-PCR, Western blotting, RIP-qPCR, dual-luciferase reporter assay, and RNA pull-down assay. Finally, a series of functional assays and Western blotting analyses confirmed SESN2 as a downstream target of SND1.

[RESULTS] Our research identified that SND1 was significantly elevated in PCa, and knocking down SND1 repressed PCa multiplication and migration. Mechanistically, sterol regulatory element binding transcription factor 1 (SREBF1) bound to the promoter of the SND1 gene and activated its transcription, which subsequently formed a complex with metadherin (MTDH). This complex is directly bound to and degraded SESN2 mRNA, and disruption of this interaction with C26-A6 inhibited MTDH-SND1-mediated SESN2 degradation. Notably, SESN2 expression was inhibited in PCa and may exert tumor-suppressive effects by affecting the AMPK/mTOR signaling pathway. Rescue experiments indicated that knocking down SND1 or MTDH significantly inhibited PCa proliferation and migration, and knocking down SESN2 partially reversed this effect.

[CONCLUSIONS] Our study reveals SND1 overexpression in PCa, which is transcriptionally activated by SREBF1. Mechanistically, SND1 interacts with MTDH and promotes SESN2 mRNA degradation, modulating PCa progression through the AMPK/mTOR pathway.