Induction of DNA double-strand breaks (DSBs) by ionizing radiation leads to formation of micrometer sized DNA-repair foci of the histone γH2AX or 53BP1 protein, the markers of DSBs (Fig. 1A). Using the diffraction-unlimited, direct stochastic optical reconstruction microscopy (dSTORM) with a lateral resolution of ∼20 nm we found (Sisario et al., 2018) that a single γH2AX focus consists of distinct circular subunits (“nanofoci”) with a diameter of ∼45 nm. Besides this, we developed an automated method to count the number of foci (Memmel et al., 2020) and applied it to analyze DNA damage in repair-proficient and repair-deficient glioblastoma multiforme (GBM) cell lines (Djuzenova et al., 2021). In addition to the experiments on DNA damage, within the scope of a grant from the Deutsche Krebshilfe e.V. we studied the migration of different GBM cell lines (Fig. 1B). We found striking differences not only in the migration pattern among the cell lines studied but also in their migratory response to the dual PI3K and mTOR inhibitor PI-103 (Memmel et al., 2017) or Akt-inhibitor MK-2206 (Djuzenova et al., 2019). The experiments are intended to test the concept of molecular targeting of migration and invasion of tumor cells as a strategy for improving radiotherapy outcome.
Sisario D, Memmel S, Doose S, Neubauer J3, Zimmermann H, Flentje M, Djuzenova CS, Sauer M, Sukhorukov VL. Nanostructure of DNA repair foci revealed by superresolution microscopy. FASEB J. 2018:fj201701435. doi: 10.1096/fj.201701435.
Grabenbauer F, Katzer A, Sisario D, Memmel S, Flentje M, Sukhorukov VL, Djuzenova CS. MEK-inhibitor PD184352 enhances the radiosensitizing effect of the Hsp90 inhibitor NVP-AUY922: the role of cell type and drug-irradiation schedule. Oncotarget. 2018;9:37379-37392. doi: 10.18632/oncotarget.26436.
Djuzenova CS, Fiedler V, Memmel S, Katzer A, Sisario D, Brosch PK, Göhrung A, Frister S, Zimmermann H, Flentje M, Sukhorukov VL. Differential effects of the Akt inhibitor MK-2206 on migration and radiation sensitivity of glioblastoma cells. BMC Cancer. 2019;19:299. doi: 10.1186/s12885-019-5517-4.
Memmel S, Sisario D, Zimmermann H, Sauer M, Sukhorukov VL, Djuzenova CS, Flentje M. FocAn: automated 3D analysis of DNA repair foci in image stacks acquired by confocal fluorescence microscopy. BMC Bioinformatics. 2020;21:27. doi: 10.1186/s12859-020-3370-8.
Djuzenova CS, Fischer T, Katzer A, Sisario D, Korsa T, Steussloff G, Sukhorukov VL, Flentje M. Opposite effects of the triple target (DNA-PK/PI3K/mTOR) inhibitor PI-103 on the radiation sensitivity of glioblastoma cell lines proficient and deficient in DNA-PKcs. BMC Cancer. 2021;21:1201. doi: 10.1186/s12885-021-08930-1.