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Background <p>Cisplatin-based chemotherapy is first-line for muscle-invasive bladder cancer (BLCA), but chemoresistance remains the primary barrier to clinical efficacy. RNA-binding proteins (RBPs) orchestrate post-transcriptional gene regulation and are increasingly implicated in cancer chemoresistance; however, the role and regulatory mechanism of the splicing factor RBP SLU7 in BLCA cisplatin resistance remain completely unknown.</p> Methods <p>We analyzed SLU7 expression and clinical prognosis in two independent cisplatin-treated BLCA cohorts (GSE87304, GSE169455). Cisplatin-resistant BLCA cell lines (T24-CIS, UMUC3-CIS) were established for functional assays (CCK-8, qRT-PCR, western blotting). Molecular interactions were validated by RIP-qPCR, immunofluorescence(IF), RNA-FISH, nucleocytoplasmic fractionation, co-immunoprecipitation (co-IP), and mass spectrometry (MS). In vivo therapeutic efficacy was assessed in BLCA xenograft models.</p> Results <p>SLU7 was significantly upregulated in cisplatin-resistant BLCA cells, and high SLU7 expression independently predicted poor cancer-specific survival (CSS) and recurrence-free survival (RFS) in cisplatin-treated patients. SLU7 knockdown suppressed MAP3K3 expression, inhibited p38 MAPK pathway, and restored cisplatin sensitivity. Mechanistically, SLU7 directly bound MAP3K3 mRNA and promoted its nuclear export—a non-canonical function independent of its canonical splicing activity. MS and Co-IP identified NAA50 as the upstream regulator that catalyzes N-terminal acetylation of SLU7 to prevent its ubiquitin-proteasomal degradation, thereby sustaining SLU7 stability. Pharmacological inhibition of NAA50 with Naa50-IN-1 destabilized SLU7, blocked the MAP3K3-p38 axis, and reversed cisplatin resistance in vitro and in vivo.</p> Conclusions <p>We uncover a novel NAA50–SLU7–MAP3K3-p38 MAPK regulatory axis that drives cisplatin resistance in BLCA. NAA50-mediated N-terminal acetylation stabilizes SLU7, which in turn facilitates MAP3K3 mRNA nuclear export to activate p38 MAPK signaling. Targeting NAA50 represents a promising therapeutic strategy to overcome cisplatin resistance in BLCA, and SLU7 serves as a predictive biomarker for cisplatin response.</p>

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NAA50-mediated SLU7 stabilization promotes cisplatin resistance in bladder cancer via regulating MAP3K3 mRNA nuclear export and p38 MAPK activation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月18日

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  • Benlin Wang,
  • Xianchong Zheng,
  • Qingsheng Hua,
  • Feng Zou,
  • Tao Huang,
  • Jiawei Chen

摘要

Background

Cisplatin-based chemotherapy is first-line for muscle-invasive bladder cancer (BLCA), but chemoresistance remains the primary barrier to clinical efficacy. RNA-binding proteins (RBPs) orchestrate post-transcriptional gene regulation and are increasingly implicated in cancer chemoresistance; however, the role and regulatory mechanism of the splicing factor RBP SLU7 in BLCA cisplatin resistance remain completely unknown.

Methods

We analyzed SLU7 expression and clinical prognosis in two independent cisplatin-treated BLCA cohorts (GSE87304, GSE169455). Cisplatin-resistant BLCA cell lines (T24-CIS, UMUC3-CIS) were established for functional assays (CCK-8, qRT-PCR, western blotting). Molecular interactions were validated by RIP-qPCR, immunofluorescence(IF), RNA-FISH, nucleocytoplasmic fractionation, co-immunoprecipitation (co-IP), and mass spectrometry (MS). In vivo therapeutic efficacy was assessed in BLCA xenograft models.

Results

SLU7 was significantly upregulated in cisplatin-resistant BLCA cells, and high SLU7 expression independently predicted poor cancer-specific survival (CSS) and recurrence-free survival (RFS) in cisplatin-treated patients. SLU7 knockdown suppressed MAP3K3 expression, inhibited p38 MAPK pathway, and restored cisplatin sensitivity. Mechanistically, SLU7 directly bound MAP3K3 mRNA and promoted its nuclear export—a non-canonical function independent of its canonical splicing activity. MS and Co-IP identified NAA50 as the upstream regulator that catalyzes N-terminal acetylation of SLU7 to prevent its ubiquitin-proteasomal degradation, thereby sustaining SLU7 stability. Pharmacological inhibition of NAA50 with Naa50-IN-1 destabilized SLU7, blocked the MAP3K3-p38 axis, and reversed cisplatin resistance in vitro and in vivo.

Conclusions

We uncover a novel NAA50–SLU7–MAP3K3-p38 MAPK regulatory axis that drives cisplatin resistance in BLCA. NAA50-mediated N-terminal acetylation stabilizes SLU7, which in turn facilitates MAP3K3 mRNA nuclear export to activate p38 MAPK signaling. Targeting NAA50 represents a promising therapeutic strategy to overcome cisplatin resistance in BLCA, and SLU7 serves as a predictive biomarker for cisplatin response.