American Association for Cancer Research
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Table S2 from TONSL Is an Immortalizing Oncogene and a Therapeutic Target in Breast Cancer

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posted on 2023-04-14, 08:41 authored by Aditi S. Khatpe, Rebecca Dirks, Poornima Bhat-Nakshatri, Henry Mang, Katie Batic, Sarah Swiezy, Jacob Olson, Xi Rao, Yue Wang, Hiromi Tanaka, Sheng Liu, Jun Wan, Duojiao Chen, Yunlong Liu, Fang Fang, Sandra Althouse, Emily Hulsey, Maggie M. Granatir, Rebekah Addison, Constance J. Temm, George Sandusky, Audrey Lee-Gosselin, Kenneth Nephew, Kathy D. Miller, Harikrishna Nakshatri

Table S2: Gene expression differences between mature luminal and luminal progenitor cells of the breast. Data are from 15 samples, five each from women of European, African and Latina ancestry.


Susan G. Komen (SGK)

Office of Extramural Research, National Institutes of Health (OER)

Breast Cancer Research Foundation (BCRF)



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.

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