我们的研究采用汇集 CRISPR 筛选，整合 2D 和 3D 培养模型，来识别在乳腺癌 (BC) 肿瘤球形成中至关重要的 miRNA。这些筛选与 RNA-seq 实验相结合，可以识别肿瘤球生长所必需的 miRNA 特征和靶标。 miR-4787-3p 在 BC 中表现出显着上调，特别是在基底样 BC 中，表明其与侵袭性疾病相关。令人惊讶的是，尽管它位于蛋白质编码基因的 5'UTR 内，该基因定义了 DROSHA 独立转录起始位点 (TSS)-miRNA，但我们发现它的成熟依赖于 DROSHA 和 DICER1。抑制 miR-4787-3p 会阻碍肿瘤球形成，凸显其作为 BC 治疗靶点的潜力。我们的研究提出 miR-4787-3p 表达升高作为 BC 不良结果的潜在预后生物标志物。我们发现在 CRISPR 筛选中积极选择的蛋白质编码基因富含 miR-4787-3p 靶标。在这些靶标中，我们选择 ARHGAP17、FOXO3A 和 PDCD4 作为已知的癌症肿瘤抑制因子，并通过实验验证 miR-4787-3p 与其 3'UTR 的相互作用。我们的工作阐明了 miR-4787-3p 在 BC 中致癌作用的分子机制。这些发现提倡针对 miR-4787-3p 进行临床研究，并强调其预后意义，为 BC 的定制治疗干预和预后评估提供有希望的途径。© 2024。Crown。

Our study employs pooled CRISPR screens, integrating 2D and 3D culture models, to identify miRNAs critical in Breast Cancer (BC) tumoursphere formation. These screens combine with RNA-seq experiments allowing identification of miRNA signatures and targets essential for tumoursphere growth. miR-4787-3p exhibits significant up-regulation in BC, particularly in basal-like BCs, suggesting its association with aggressive disease. Surprisingly, despite its location within the 5'UTR of a protein coding gene, which defines DROSHA-independent transcription start site (TSS)-miRNAs, we find it dependant on both DROSHA and DICER1 for maturation. Inhibition of miR-4787-3p hinders tumoursphere formation, highlighting its potential as a therapeutic target in BC. Our study proposes elevated miR-4787-3p expression as a potential prognostic biomarker for adverse outcomes in BC. We find that protein-coding genes positively selected in the CRISPR screens are enriched of miR-4787-3p targets. Of these targets, we select ARHGAP17, FOXO3A, and PDCD4 as known tumour suppressors in cancer and experimentally validate the interaction of miR-4787-3p with their 3'UTRs. Our work illuminates the molecular mechanisms underpinning miR-4787-3p's oncogenic role in BC. These findings advocate for clinical investigations targeting miR-4787-3p and underscore its prognostic significance, offering promising avenues for tailored therapeutic interventions and prognostic assessments in BC.© 2024. Crown.