Toma stem (brain-tumor-initiating) cells [12] and human glioblastoma cell lines [58]. Notably, in
Toma stem (brain-tumor-initiating) cells [12] and human glioblastoma cell lines [58]. Notably, in the latter study, only 1 (U138MG) and in tendency also a second (T98G) out of 5 glioblastoma lines have been radiosensitized by disulfiram (7500 nM) when grown in Cu2+ -containing serum-supplemented medium and when utilizing clonogenic survival as the endpoint [58]. Clonogenic survival determines the probability of a treated tumor to relapse, and is therefore believed to be the gold typical for the interpretation of drug effects on radiosensitivity in radiation biology [59]. Within the glioblastoma stem-cell spheroid cultures, 5 Gy irradiation in combination with disulfiram (one hundred nM) and Cu2+ (200 nM) further decreased viability (as defined by metabolic activity and compared to the disulfiram/Cu2+ /0 Gy arm) of only one particular out of two tested spheroid cultures [12]. Additionally, within the same study, disulfiram/Cu2+ delayed repair of DNA double-strand breaks (DSBs) of 2 Gy-irradiated cells PDE3 Modulator Species without the need of rising the number of residual (24 h-value) DSBs, as analyzed by the counting of nuclear H2AX (phosphorylated histone H2AX) foci [12]. Considering that only restricted conclusions on clonogenic survival may be drawn in the decay of radiation-induced H2AX foci [60] also as metabolically defined “viability” of irradiated cancer cells, the reported proof for a radiosensitizing function of disulfiram in glioblastoma stem cells is limited. Combined with the notion that disulfiram radiosensitized only a minor fraction of the tested panel of glioblastoma cell lines [58], and on top of that contemplating the results of our present study, it may be concluded that disulfiram could radiosensitize glioblastoma (stem) cells, but this appears to become rather an exception than a common phenomenon. The predicament is different in irradiated AT/RT (atypical teratoid/rhabdoid) brain tumor lines and primary cultures, exactly where disulfiram (in Cu(II)-containing serum-supplemented medium) regularly decreases survival fractions in colony μ Opioid Receptor/MOR Inhibitor Formulation formation assays of all tested cell models with an EC50 of 20 nM [61]. four.3. Cu2+ -Mediated Oxidative Strain The radiosensitizing action of disulfiram almost certainly is dependent upon the Cu2+ ion-overloading function in the drug. Ionizing radiation induces beyond instant radical formation (e.g., formation of OHby ionization of H2 O) delayed long-lasting mitochondrial-generated superoxide anion (O2 – formation which contributes to radiation-mediated genotoxic harm [62]. It is tempting to speculate that disulfiram-mediated Cu2+ overload and subsequent OHformation (see introduction) collaborates with radiation-triggered mitochondrial oxidative strain (and also with temozolomide) in introducing DNA DSBs. If that’s the case, the radiosensitizing (and also temozolomide-sensitizing) effect of disulfiram needs to be, on the one particular hand, a direct function of the interstitial Cu2+ concentration, and around the other, a function from the intracellular Cu2+ -reducing, Cu+ -chaperoning, -sequestrating, and -extruding capability at the same time as the oxidative defense of a tumor cell [63,64]. The Cu2+ -Biomolecules 2021, 11,17 ofdetoxifying capability most most likely differs in between cell kinds, and could explain the distinction in reported radiosensitizing activity of disulfiram among AT/RT [61] as well as the glioblastoma (stem) cells ([12,59] and present study). In specific, tumor stem cells happen to be demonstrated to exhibit upregulated drug-efflux pumps, DNA repair, and oxidative defense [65]. 4.4. Does Disulfiram Specificall.
