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Published on: December 9, 2016
PTBP1-Mediated Alternative Splicing of DNAJB6 Promotes Everolimus Resistance in Clear Cell Renal Cell Carcinoma via
Xiu-Wu Pan1, Hong-Feng Zheng1, Mu-Chen Li1
1Department of Urology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
Background:
Everolimus (EVE) is a key treatment for advanced clear cell renal cell carcinoma (ccRCC), mainly targeting AKT/mTOR signaling. However, developed resistance remains a major challenge for EVE treatment. Aberrant alternative splicing, particularly regulated by PTBP1, may represent a critical mechanism enabling the activation of these resistance-associated pathways.
Methods:
Single-cell transcriptome sequencing is performed to reveal the association between PTBP1 expression, EVE resistance and AKT/mTOR pathway activity. Patient-derived specimens, animal models, and in vitro assays are used to evaluate the role of PTBP1 in EVE resistance. Full-length transcriptome sequencing and crosslinking immunoprecipitation (CLIP) sequencing are employed to identify PTBP1-regulated splicing targets. Co-immunoprecipitation, proteomic analyses, and molecular docking further elucidate the mechanism by which DNAJB6b re-activated AKT/mTOR signaling.
Results:
PTBP1 is upregulated in EVE-resistant tumors and its expression positively correlates with AKT/mTOR signaling activation. PTBP1 promotes the expression of the DNAJB6b isoform through alternative splicing. EIF4B is identified as a direct binding partner of DNAJB6b, forming a complex that enhances oncogenic translation and activates a PKIB-dependent AKT/mTOR signaling cascade.
Conclusion:
This study demonstrates that PTBP1 drives EVE resistance in ccRCC by upregulating DNAJB6b, which recruits EIF4B to initiate a PKIB/AKT/mTOR positive feedback loop, sustaining oncogenic translation and therapeutic evasion.
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