LncRNA-CYTOR/SRSF4/7 RNA-protein Complex Promotes Crpc Progression Through Regulating Alternative Splicing Of AR-V7

Objective: The androgen receptor(AR)is a key therapeutic target in advanced prostate cancer(PCa).Castration-resistant prostate cancers(CRPC)frequently express the androgen receptor splice variant-7(AR-V7),a constitutively active AR associated with resistance to AR-targeting therapies.In spite of its clinical importance,the molecular process leading to alternative splicing of AR-V7 m RNA remains poorly understood.In present study,we aim to investigate the molecular mechanism of the alternative splicing of AR-V7.Methods: We developed an androgen-independent LNCa P cell line(LNCa P-AI)with detectable AR-V7 expression to investigate factors involved in AR-V7 m RNA splicing.First,we used RNA-array results to find putative trans-acting splicing factors required for AR-V7 m RNA splicing.We next focused on long non-coding RNAs(lnc RNAs)that may interact with splicing factors to mediate sequence-specific regulation of AR-V7 splicing.Through bioinformatic,biochemical,and expression analysis in human CRPC samples,we need to confirm the expression and functional role of lnc RNA.Importantly,in our developed cell lines and xenografts model,we validated the effect of targeting AR-V7 splicing process with antisense oligonucleotides(ASOs)or si RNA/sh RNA.Results: First,we identified SRSF4 and SRSF7 as putative trans-acting splicing factors required for AR-V7 m RNA splicing.We next focused on lnc RNAs that may interact with SRSF4/7 to mediate sequence-specific regulation of AR-V7 splicing.Through bioinformatic,biochemical,and expression analysis in human CRPC samples,cytoskeleton regulator RNA(CYTOR)was determined to be key lnc RNA that regulate AR-V7 m RNA splicing.CYTOR interacts with SRSF4/7,leading to AR cryptic exon 3(CE3)inclusion and AR-V7 generation.Targeting CYTOR/AR-V7 axis with ASOs or si RNA/sh RNA leads to reducing PCa resistance to androgen deprivation therapy (ADT)with enzalutamide.These findings support a regulated process that mediate CRPC-specific AR-V7 splicing,and a critical role for targeting CYTOR in altering PCa androgen-deprivation therapy resistance.Conclusion: In summary,these results suggest that complex of CYTOR/SRSF4/7 could regulate the alternative splicing of AR-V7 in CRPC.The metastatic CRPC specific CYTOR is an excellent diagnostic marker for treatment selection of CRPC patients and a target to receive re-sensitivity of enzalutamide resistant patients.