PARP 抑制剂 (PARPi) 疗法改变了同源重组 DNA 修复 (HRR) 缺陷的卵巢癌患者的治疗结果，例如 BRCA1 或 BRCA2 基因缺陷患者。不幸的是，PARPi 耐药性很常见。多种耐药机制已被描述，包括恢复 HR 基因阅读框的二次突变。 BRCA1 剪接异构体 △11 和 △11q 可以通过剪接含有突变的外显子，产生截短的、部分功能的蛋白质，从而有助于 PARPi 耐药。然而，BRCA1 外显子跳跃的临床影响和潜在驱动因素尚未完全了解。我们分析了 9 个具有 BRCA1 外显子 11 移码突变的卵巢癌和乳腺癌患者来源的异种移植物 (PDX)，以了解外显子跳跃和治疗反应，包括来自化疗/PARPi 前后的患者。 BRCA1 外显子 11 跳跃在 PARPi 耐药的 PDX 肿瘤中升高。使用 qRT-PCR、RNA 测序、免疫印迹和小基因建模证实，两个独立的 PDX 模型获得了驱动外显子跳跃的二次 BRCA1 剪接位点突变 (SSM)。 CRISPR/Cas9 介导的剪接功能破坏验证了外显子跳跃是 PARPi 抗性的机制。 ARIEL2 和 ARIEL4 临床试验的 PARPi 后卵巢癌患者队列中的 SSM 也有所丰富。在临床环境中很少有 PARPi 耐药机制得到证实。虽然二次/回复突变通常会恢复基因的阅读框，但我们已经在患者群体中发现了二次突变，这些突变劫持剪接位点以增强包含突变的外显子跳跃，导致 BRCA1 亚型的过度表达，进而促进 PARPi 耐药。因此，BRCA1 SSM 可以而且应该与框架恢复二次突变一起进行临床监测。© 2024。作者。

PARP inhibitor (PARPi) therapy has transformed outcomes for patients with homologous recombination DNA repair (HRR) deficient ovarian cancers, for example those with BRCA1 or BRCA2 gene defects. Unfortunately, PARPi resistance is common. Multiple resistance mechanisms have been described, including secondary mutations that restore the HR gene reading frame. BRCA1 splice isoforms △11 and △11q can contribute to PARPi resistance by splicing out the mutation-containing exon, producing truncated, partially functional proteins. However, the clinical impacts and underlying drivers of BRCA1 exon skipping are not fully understood.We analyzed nine ovarian and breast cancer patient derived xenografts (PDX) with BRCA1 exon 11 frameshift mutations for exon skipping and therapy response, including a matched PDX pair derived from a patient pre- and post-chemotherapy/PARPi. BRCA1 exon 11 skipping was elevated in PARPi resistant PDX tumors. Two independent PDX models acquired secondary BRCA1 splice site mutations (SSMs) that drive exon skipping, confirmed using qRT-PCR, RNA sequencing, immunoblotting and minigene modelling. CRISPR/Cas9-mediated disruption of splicing functionally validated exon skipping as a mechanism of PARPi resistance. SSMs were also enriched in post-PARPi ovarian cancer patient cohorts from the ARIEL2 and ARIEL4 clinical trials.Few PARPi resistance mechanisms have been confirmed in the clinical setting. While secondary/reversion mutations typically restore a gene's reading frame, we have identified secondary mutations in patient cohorts that hijack splice sites to enhance mutation-containing exon skipping, resulting in the overexpression of BRCA1 hypomorphs, which in turn promote PARPi resistance. Thus, BRCA1 SSMs can and should be clinically monitored, along with frame-restoring secondary mutations.© 2024. The Author(s).