Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana.
Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana.
Cancer Res. 2023 Apr 14;83(8):1345-1360. doi: 10.1158/0008-5472.CAN-22-3667.
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.
由于缺乏同基因模型，研究导致上皮细胞永生化的基因组异常一直具有技术挑战性。为了解决这个问题，我们使用不同遗传背景的健康原发性乳腺腔上皮细胞及其 hTERT 永生化对应物来鉴定与永生化相关的转录组变化。TONSL（Tonsoku-like，DNA 修复蛋白）的高表达被鉴定为永生化过程中的最早事件之一。位于 8q24.3 染色体上的 TONSL 在大约 20%的乳腺癌中被发现扩增。TONSL 本身可以使原代乳腺上皮细胞永生化并增加端粒酶活性，但过表达不足以引起肿瘤转化。然而，TONSL 永生化的原代细胞过表达特定的癌基因，在小鼠中产生雌激素受体阳性腺癌。对包含约 600 个肿瘤的乳腺肿瘤微阵列进行分析显示，TONSL 过表达肿瘤患者的总体生存率和无进展生存率较差。TONSL 增加了致癌转录因子（包括 NF-κB）的染色质可及性，并限制了肿瘤抑制因子 p53 的可及性。TONSL 过表达导致与 DNA 修复枢纽相关的基因表达发生显著变化，包括同源重组（HR）和范可尼贫血途径中的几个基因上调。与这些结果一致，TONSL 过表达的原代细胞表现出通过 HR 上调的 DNA 修复。此外，TONSL 对于体内 TONSL 扩增的乳腺癌细胞系的生长是必需的，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 鉴定为促进癌症起始的上皮细胞永生化的调节剂，并将其鉴定为乳腺癌治疗的靶标。
chr.8q24.3 扩增子驻留基因 TONSL 在肿瘤发生的初始步骤中上调，通过增加 DNA 修复来支持肿瘤转化，代表了治疗乳腺癌的潜在治疗靶点。
