Ionizing radiation and somatostatin analogues are used for acromegaly treatment to achieve normalization or reduction of growth hormone hypersecretion and tumor shrinkage. In this study, we investigated a combination of somatostatin (SS14) with ionizing radiation of 60Co and its effect on reparation of radiation-induced damage and cell death of somatomammotroph pituitary cells GH3. Doses of γ-radiation 20-50 Gy were shown to inhibit proliferation and induce apoptosis in GH3 cells regardless of somatostatin presence. It has been found that the D0 value for GH3 cells was 2.5 Gy. Somatostatin treatment increased radiosensitivity of GH3 cells, so that D0 value decreased to 2.2 Gy. We detected quick phosphorylation of histone H2A.X upon irradiation by the dose 20 Gy and its colocalization with phosphorylated protein Nbs-1 in the site of double strand break of DNA (DSB). Number of DSB decreased significantly 24 h after irradiation, however, clearly distinguished foci persisted, indicating non repaired DSB, after irradiation alone or after combined treatment by irradiation and SS14. We found that SS14 alone triggers phosphorylation of Nbs1 (p-Nbs1), which correlates with antiproliferative effect of SS14. Irradiation also increased the presence of p-Nbs1. Most intensive phosphorylation of Nbs1 was detected after combined treatment of irradiation and SS14. The decrease of the number of the DSB foci 24 h after treatment shows a significant capacity of repair systems of GH3 cells. In spite of this, large number of unrepaired DSB persists for 24 h after the treatment. We conclude that SS14 does not have a radioprotective effect on somatomammotroph GH3 cells., M. Řezáčová, J. Čáp, D. Vokurková, E. Lukášová, J. Vávrová, J. Cerman, V. Mašín, N. Mazánková., and Obsahuje bibliografii a bibliografické odkazy
Acute promyelocytic leukemia is characterized by a block of myeloid differentiation. The incubation of cells with 1 μmol/l all-trans retinoic acid (ATRA) for 72 h induced differentiation of HL-60 cells and increased the number of CD11b positive cells. Morphological and functional changes were accompanied by a loss of proliferative capacity. Differentiation caused by preincubation of leukemic cells HL-60 with ATRA is accompanied by loss of clonogenicity (control cells: 870 colonies/103 cells, cells preincubated with ATRA: 150 colonies/103 cells). D0 for undifferentiated cells was 2.35 Gy, for ATRA differentiated cells 2.46 Gy. Statistical comparison of clonogenity curves indicated that in the whole range 0.5-10 Gy the curves are not significantly different, however, in the range 0.5-3 Gy ATRA differentiated cells were significantly more radioresistant than non-differentiated cells. When HL-60 cells preincubated with 1 μmol/l ATRA were irradiated by a sublethal dose of 6 Gy, more marked increase of apoptotic cells number was observed 24 h after irradiation and the surviving cells were mainly in the G1 phase of the cell cycle, while only irradiated cells were accumulated in G2 phase. Our results imply that preincubation of cells with ATRA accelerates apoptosis occurrence (24 h) after irradiation by high sublethal dose of 6 Gy. Forty-eight hours after 6 Gy irradiation, late apoptotic cells were found in the group of ATRA pretreated cells, as determined by APO2.7 positivity. This test showed an increased effect (considering cell death induction) in comparison to ATRA or irradiation itself., M. Mareková, J. Vávrová, D. Vokurková, J. Psutka., and Obsahuje bibliografii