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DOI: 10.1055/s-0041-1727981
Patient derived e x vivo slice cultures demonstrate a profound DNA double-strand break repair defect in HPV-positive OPSCC
Introduction HPV-induced oropharyngeal cancer (OPSCC) are more sensitive towards radiation than HPV-negative. Underlying mechanism are discussed controversial. Theories are enhanced cellular radiosensitivity based on a defect in DNA double-strand break (DSB) repair or stronger immunogenicity. Limitation for the first theory is the experimental restriction to a low number of HPV positive and negative HNSCC cell lines.
Methods We assessed DSB repair of HPV-positive and HPV-negative HNSCC using 400µm thick, patient derived tumor slice cultures, which were irradiated and fixed after 2 and 24h, partially after inhibiting the central DNA damage response kinase ATM. Residual DSBs were analyzed by quantification of 53BP1 repair foci in enlarged p63-positive nuclei indicative of tumor cell origin.
Results Analyzed nuclei of HPV+ OPSCC cultures (n=6) displayed on average an almost 5 times higher residual foci number than HPV-OPSCC (n=8) (3 Gy: 6,3 vs. 1,4 Foci/ normalized cell nucleus p = 0,019). Inhibition of the central DNA damage response kinase ATM resulted in a profound (3-5 fold) increase in residual foci numbers in HPV-negative samples (n=3). Amongst the HPV-positive samples only the tumor showing the most effective DSB-repair demonstrated an enhancement in foci numbers.
Conclusions Our ex-vivo data, to the best of our knowledge, represent the first experimental evidence for the DSB repair defect of HPV+ OPSCC outside of established cell lines. Our experiments indicate a defect in the ATM-mediated DNA damage response as a contributing factor. Clinically, the functional ex vivo assay may be a powerful tool to predict patient-individual radiosensitivity and to identify cases of HPV positive tumors with a functional DSB repair to be excluded from de-intensification trials.
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Conflict of interest
Der Erstautor gibt keinen Interessenskonflikt an.
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Publication History
Article published online:
13 May 2021
© 2021. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).
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