The γH2AX Foci Assay – Improvements for a possible clinical Application


The γH2AX Foci Assay – Improvements for a possible clinical Application

von Neubeck, C.; Rassamegevanon, T.; Richter, D.; Meneceur, S.; Löck, S.; Range, U.; Hiemann, R.; Krause, M.; Baumann, M.

Abstract

Introduction:

The phosphorylation of histone H2AX (γH2AX) is one of the early events in the DNA repair pathways for DNA double strand break repair following radiation exposure. In xenografted human head and neck squamous cell carcinomas (hHNSCC), we found a significant correlation of initial and residual γH2AX foci after in vivo irradiation with local tumor control (Menegakis et al. 2011, Koch et al. 2013). Based on tumor biopsies, the γH2AX foci assay was translated to a clinically relevant ex vivo irradiation setting. We could show that the slopes of the dose response curves of ex vivo irradiated patient-derived and xenograft-derived tumor biopsies allow for discrimination of radio-resistant and radio-sensitive tumor types (Menegakis et al. 2015).

Methods & Results:

Ongoing work is focused on in vivo irradiated hHNSCC xenograft tumors as well as ex vivo irradiated HNSCC patient-derived and xenograft-derived biopsies. Studies with experimental tumors are dedicated to technical developments and biological characteristics of γH2AX foci. Here, a comparison of manually counted and automatically evaluated γH2AX foci from in vivo and ex vivo irradiated xenograft samples will be presented. A particular focus in manually evaluated samples was set to the exclusion criteria for pan-nuclear stained cells and the corresponding interpretation bias for tumor radio-sensitivity missing apoptotic, necrotic, mitotic and S-phase cells. In clinical routine, very little biological material is available for experimental diagnostic purposes. Therefore, the inter- and intra-tumoral heterogeneities of experimental hHNSCC tumors were evaluated and statistically modeled to allow a logical transfer to the clinical situation.

Conclusion:

Overall, our findings support the clinical relevance of γH2AX foci as potential biomarkers for individual radio-sensitivity and therewith, for personalized cancer treatment. Nonetheless, additional strategies are needed to improve the robustness and process time of the assay.

Acknowledgement:

This work was supported by a grant of the Federal Ministry of Education and Research (BMBF 02NUK035C).

References:

Menegakis et al., Radiother. Oncol. 100:137–44 (2011)
Koch et al., Radiother. Oncol. 108:434–39 (2013)
Menegakis et al., Radiother. Oncol. 116:473–79 (2015)

  • Lecture (Conference)
    Gesellschaft für biologische Strahlenforschung GBS annuel meeting, 26.-28.09.2016, Erlangen, Deutschland

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