One of our goals is radiation-induced DNA damage and repair of DNA double-strand breaks (DSBs) in tumor cells of different entities. Induction of DNA DSBs by ionizing radiation leads to formation of micrometer sized DNA-repair foci of the histone γH2AX, a marker of DSBs (Fig. 1a, b), whose organization on the nanometer-scale remains unknown because of the diffraction limit (∼200 nm) of conventional microscopy (Fig. 1b). Therefore we applied the diffraction-unlimited, direct stochastic optical reconstruction microscopy (dSTORM) with a lateral resolution of ∼20 nm to gain an insight into the nanostructure of DNA repair foci (Fig. 1c). We found (Sisario et al., 2018) that a single γH2AX focus consists of distinct circular subunits (“nanofoci”) with a diameter of ∼45 nm (Fig. 1d). In addition to the experiments on DNA damage, within the scope of a grant from the Deutsche Krebshilfe we currently studied the migration of different glioblastoma multiforme cell lines. 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). Thus, we found that PI-103 inhibited migration of DK-MG (p53 wt, PTEN wt) but not of SNB19 (p53 mut, PTEN mut) cells probably due to an aberrant reactivation of the PI3K pathway in SNB19 cells treated with PI-103. 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.
Memmel S, Sisario D, Zöller C, Fiedler V, Katzer A, Heiden R, Becker N, Eing L, Ferreira FLR, Zimmermann H, Sauer M, Flentje M, Sukhorukov VL, Djuzenova CS. Migration pattern, actin cytoskeleton organization and response to PI3K-, mTOR-, and Hsp90-inhibition of glioblastoma cells with different invasive capacities. Oncotarget. 2017;8:45298-45310. doi: 10.18632/oncotarget.16847.
Djuzenova CS, Zimmermann M, Katzer A, Fiedler V, Distel LV, Gasser M, Waaga-Gasser AM, Flentje M, Polat B. A prospective study on histone γ-H2AX and 53BP1 foci expression in rectal carcinoma patients: correlation with radiation therapy-induced outcome. BMC Cancer. 2015;15:856. doi: 10.1186/s12885-015-1890-9.
Djuzenova CS, Fiedler V, Memmel S, Katzer A, Hartmann S, Krohne G, Zimmermann H, Scholz CJ, Polat B, Flentje M, Sukhorukov VL. Actin cytoskeleton organization, cell surface modification and invasion rate of 5 glioblastoma cell lines differing in PTEN and p53 status. Exp Cell Res. 2015;330:346-57. doi: 10.1016/j.yexcr.2014.08.013.