Abstract
Background/Aims: Alterations of cytosolic Ca2+-activity ([Ca2+](i)) are decisive in the regulation of tumor cell proliferation, migration and survival. Transport processes participating in the regulation of [Ca2+] i include Ca2+ extrusion through K+-independent (NCX) and/or K+-dependent (NCKX) Na+/Ca2+-exchangers. The present study thus explored whether medulloblastoma cellsexpress Na+/Ca2+-exchangers, whether expression differs between therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells, and whether Na+/Ca2+-exchangersparticipate in the regulation of cell survival. Methods: In therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells transcript levels were estimated by RT-PCR, protein abundance by Western blotting, cytosolic Ca2+-activity ([Ca2+] i) from Fura-2-fluorescence, Na+/Ca2+-exchanger activity from the increase of [Ca2+] i (.[Ca2+] i) and from whole cell current (I-ca) following abrupt replacement of Na+ containing (130 mM) and Ca2+ free by Na+ free and Ca2+ containing (2 mM) extracellular perfusate as well as cell death from PI -staining and annexin-V binding in flow cytometry. Results: The transcript levels of NCX3, NCKX2, and NCKX5, protein abundance of NCX3, slope and peak of.[Ca2+] i as well as Ica were significantly lower in therapy sensitive D283 than in therapy resistant UW228-3 medulloblastoma cells. The Na+/Ca2+-exchanger inhibitor KB-R7943 (10 mu M) significantly blunted.[Ca2+](i), and augmented the ionizing radiation-induced apoptosis but did not significantly modify clonogenicityof medulloblastoma cells. Apoptosis was further enhanced by NCX3 silencing. Conclusions: Na+/Ca2+-exchanger activity significantly counteracts apoptosis but does not significantly affect clonogenicity after radiation of medulloblastoma cells. (C) 2017 The Author(s) Published by S. Karger AG, Basel