由基因组畸变导致上皮细胞不死化的研究由于缺乏同基因模型而在技术上充满挑战。为了解决这个问题，我们使用不同遗传来源的健康原代乳腺腺上皮细胞及其hTERT不死化后代，以确定与不死化相关的转录组变化。升高的TONSL(Tonsoku-like, DNA repair protein)表达是不死化期间的最早事件之一。TONSL位于8q24.3染色体上，约20%的乳腺癌中发现其扩增。TONSL单独使原代乳腺上皮细胞不死化并增加端粒酶活性，但过量表达不足以引起新生化形态转化。然而，在TONSL不死化的原代细胞上过表达已定义的癌基因，在小鼠中生成雌激素受体阳性的腺癌。对约600个肿瘤的乳腺肿瘤芯片分析显示TONSL过度表达的患者总体和无进展生存率较差。TONSL增加了促癌基因转录因子（包括NF-κB）对染色质的可及性，而限制了肿瘤抑制因子p53的访问。TONSL过度表达导致与DNA修复枢纽相关的基因表达显著改变，包括同源重组（HR）和Fanconi贫血通路中的多个基因上调。与这些结果一致，TONSL过度表达的原代细胞通过HR展现出上调的DNA修复。此外，TONSL对TONSL扩增的乳腺癌细胞系的生长至关重要，并且这些细胞对TONSL-FACT复合物抑制剂CBL0137敏感。总之，这些发现将TONSL确定为上皮细胞不死化的调节因子，以促进癌症引发并作为乳腺癌治疗的靶点。chr.8q24.3扩增的TONSL基因是肿瘤形成的初步步骤中上调的，通过增加DNA修复来支持新生化形态的转化，代表了治疗乳腺癌的潜在治疗靶点。 ©2023美国癌症研究协会。

Study of genomic aberrations leading to immortalization of epithelial cells has been technically challenging due to the lack of isogenic models. To address this, we used healthy primary breast luminal epithelial cells of different genetic ancestry and their hTERT-immortalized counterparts to identify transcriptomic changes associated with immortalization. Elevated expression of TONSL (Tonsoku-like, DNA repair protein) was identified as one of the earliest events during immortalization. TONSL, which is located on chromosome 8q24.3, was found to be amplified in approximately 20% of breast cancers. TONSL alone immortalized primary breast epithelial cells and increased telomerase activity, but overexpression was insufficient for neoplastic transformation. However, TONSL-immortalized primary cells overexpressing defined oncogenes generated estrogen receptor-positive adenocarcinomas in mice. Analysis of a breast tumor microarray with approximately 600 tumors revealed poor overall and progression-free survival of patients with TONSL-overexpressing tumors. TONSL increased chromatin accessibility to pro-oncogenic transcription factors, including NF-κB and limited access to the tumor-suppressor p53. TONSL overexpression resulted in significant changes in the expression of genes associated with DNA repair hubs, including upregulation of several genes in the homologous recombination (HR) and Fanconi anemia pathways. Consistent with these results, TONSL-overexpressing primary cells exhibited upregulated DNA repair via HR. Moreover, TONSL was essential for growth of TONSL-amplified breast cancer cell lines in vivo, and these cells were sensitive to TONSL-FACT complex inhibitor CBL0137. Together, these findings identify TONSL as a regulator of epithelial cell immortalization to facilitate cancer initiation and as a target for breast cancer therapy.The chr.8q24.3 amplicon-resident gene TONSL is upregulated during the initial steps of tumorigenesis to support neoplastic transformation by increasing DNA repair and represents a potential therapeutic target for treating breast cancer.©2023 American Association for Cancer Research.