Molecular features unique to glioblastoma radiation resistant residual cells may affect patient outcome - a short report
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Previously we have shown, using a primary glioblastoma (GBM) cell model, that a subpopulation of innately radiation resistant (RR) GBM cells survive radiotherapy and form multinucleated and giant cells (MNGCs) by homotypic fusions. We also showed that MNGCs may cause relapse. Here, we set out to explore whether molecular characteristics of RR cells captured from patient-derived primary GBM cultures bear clinical relevance.
Primary cultures were derived from 19 naive GBM tumor samples. RR cells generated from these cultures were characterized using various cell biological assays. We also collected clinicopathological data of the 19 patients and assessed associations with RR variables using Spearman’s correlation test and with patient survival using Kaplan-Meier analysis. Significance was determined using a log-rank test.
We found that SF2 (surviving fraction 2) values (p = 0.029), days of RR cell formation (p = 0.019) and percentage of giant cells (p = 0.034) in the RR population independently correlated with a poor patient survival. We also found that low ATM (Ataxia-telangiectasia mutated) expression levels in RR cells showed a significant (p = 0.002) negative correlation with SF2 values. A low ATM expression level in RR cells along with a high tumor volume was also found to negatively correlate with patient survival (p = 0.011). Finally, we found that the ATM expression levels in RR cells independently correlated with a poor patient survival (p = 0.014).
Our data indicate that molecular features of innately radiation resistant GBM cells independently correlate with clinical outcome. Our study also highlights the relevance of using patient-derived primary GBM cultures for the characterization of RR cells that are otherwise inaccessible for analysis.
KeywordsGlioblastoma Radiation resistant cells Patient-derived primary cultures MNGCs ATM DNA repair
We are grateful to Dr. Sadhana Kannan for help with statistical analysis and to Prof. B. J. Rao, TIFR, for providing the anti-ATM antibody. AG acknowledges DST-SERB, India for providing a National Post-Doctoral Fellowship (PDF/2016/00158), and SS acknowledges CSIR for providing a fellowship.
This study is supported by a Department of Biotechnology grant (BT/PR4020/MED/30/792/2012) to SD.
Compliance with ethical standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the Tata Memorial Centre institutional ethics committee (TMC-IEC III: - ECR/149/Inst/MH/2013) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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