American Association for Cancer Research
15357163mct170792-sup-188055_3_supp_4626249_p6f8m2.pdf (144.05 kB)

Figure S2 from Induced Telomere Damage to Treat Telomerase Expressing Therapy-Resistant Pediatric Brain Tumors

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journal contribution
posted on 2023-04-03, 15:06 authored by Satarupa Sengupta, Matthew Sobo, Kyungwoo Lee, Shiva Senthil Kumar, Angela R. White, Ilgen Mender, Christine Fuller, Lionel M.L. Chow, Maryam Fouladi, Jerry W. Shay, Rachid Drissi

A, Telomerase activity in HFF+hTERT cells treated with DMSO, 6-thio-dG (3 µM for 3 days), and imetelstat (IMT; 2 µM). For combination treatment, cells were pre-treated with IMT for 3 days and then with 6-thio-dG for another 3 days. (-) C, (+) C, and IC indicate negative control, positive control, and internal control respectively. Telomerase products are indicated. B-C, effect of telomerase inhibition on cell growth of HFF (B) and HFF+hTERT (C) cells treated with imetelstat (IMT; 2 µM) only, 6-thio-dG (3 µM) only, or 6-thio-dG in combination with imetelstat as described in A. Error bars represent the standard deviation generated from triplicates. P-value, **, P<0.01. D, quantification showing percent cells with TIFs in HFF+hTERT cells treated with imetelstat (IMT; 2 µM) only, 6-thio-dG (3 µM for 3 days), or in combination with imetelstat as described in A. Cells counted for each treatment (n= ~50 cells). Bottom panels show representative images showing TRF2 (green), γH2AX (red), and TIFs (yellow) indicated by white arrows. DAPI (blue) indicates nucleus staining.


CancerFree KIDS Pediatric Cancer Research Alliance

Cincinnati Children's Hospital Medical Center



Brain tumors remain the leading cause of cancer-related deaths in children and often are associated with long-term sequelae among survivors of current therapies. Hence, there is an urgent need to identify actionable targets and to develop more effective therapies. Telomerase and telomeres play important roles in cancer, representing attractive therapeutic targets to treat children with poor-prognosis brain tumors such as diffuse intrinsic pontine glioma (DIPG), high-grade glioma (HGG), and high-risk medulloblastoma. We have previously shown that DIPG, HGG, and medulloblastoma frequently express telomerase activity. Here, we show that the telomerase-dependent incorporation of 6-thio-2′deoxyguanosine (6-thio-dG), a telomerase substrate precursor analogue, into telomeres leads to telomere dysfunction–induced foci (TIF) along with extensive genomic DNA damage, cell growth inhibition, and cell death of primary stem-like cells derived from patients with DIPG, HGG, and medulloblastoma. Importantly, the effect of 6-thio-dG is persistent even after drug withdrawal. Treatment with 6-thio-dG elicits a sequential activation of ATR and ATM pathways and induces G2–M arrest. In vivo treatment of mice bearing medulloblastoma xenografts with 6-thio-dG delays tumor growth and increases in-tumor TIFs and apoptosis. Furthermore, 6-thio-dG crosses the blood–brain barrier and specifically targets tumor cells in an orthotopic mouse model of DIPG. Together, our findings suggest that 6-thio-dG is a promising novel approach to treat therapy-resistant telomerase-positive pediatric brain tumors. Mol Cancer Ther; 17(7); 1504–14. ©2018 AACR.