These findings are supported by studies in other malignancy cell lines. and functionally active in all three cell lines. Adenosine showed moderate cytotoxicity (MTT-IC50 values were between 700 and 900?M) and induced apoptosis in a concentration-dependent manner by increasing levels of sub-G1 and cleaved PARP. Apoptosis was Angelicin diminished by QVD-OPh, confirming caspase-dependent induction of apoptosis. Forty-eight hours pre-incubation of adenosine prior to cisplatin significantly enhanced cisplatin-induced cytotoxicity in a synergistic manner and increased apoptosis. SLV320 or PSB603, selective A1 and A2B antagonists, was not able to inhibit adenosine-induced increase Angelicin in cisplatin cytotoxicity or apoptosis whereas dipyridamole, a nucleoside transporter inhibitor, completely abrogated both effects. Mechanistically, adenosine increased pAMPK and reduced pS6K which was prevented by dipyridamole. In conclusion, application of adenosine prior to cisplatin could be a new therapeutic option to increase the potency of cisplatin in a synergistic manner and thus overcome platinum resistance in ovarian malignancy. Electronic supplementary material The online version of this article (10.1007/s11302-018-9622-7) contains supplementary material, which is available to authorized users. mutations and previously receiving three or more chemotherapy regimens [8, 9]. However, PARP inhibitors are limited to Triton X-100) for 10 to 20?min at 4 to 8?C. Luminescence was measured after addition of luciferase assay reagent (30?mM Tricine, 10?mM MgSO4, 0.5?mM EDTA, 10?mM DTT, 0.5?mM ATP, 0.5?mM coenzyme A, and 0.05?mM D-luciferin) by a LUMIstar Galaxy microplate reader (BMG Labtech, Germany). Measurement of apoptotic cells The cells were seeded at a density of 5??104 cells per well in 24-well Angelicin plates (Sarstedt, Germany). They were treated with numerous concentrations of adenosine alone or in combination with cisplatin for indicated time points. The supernatant was removed after centrifugation step, and the cells were lysed in 500?l of hypotonic PI-staining buffer (0.1% sodium citrate, 0.1% Triton X-100, and 100?g/ml propidium iodide solution in filtered distilled water) at 4 to 8?C in the dark for at least 6?h. The percentage of apoptotic nuclei with DNA content in sub-G1 was analyzed by circulation cytometry (CyFlow, Partec, Germany) or by fluorescence imaging (Thermo Fisher Array Scan XTI, Schwerte, Germany). Immunoblotting The cells were treated with numerous concentrations of adenosine alone or in combination with cisplatin for indicated time points. Protein samples were prepared from cell lysate in a reducing condition using lysis buffer 6 (Bio-Tech, Germany) or RIPA lysis buffer (50?mM Tris HCl, 2?mM EDTA, 150?mM NaCl, 0.1% SDS, 1% Triton X-100, and 0.5% sodium deoxycholate) plus protease/phosphatase inhibitor. Equivalent amounts of total protein (25 to 35?g) were resolved by SDS-PAGE and transferred to polyvinylidene fluoride (PVDF) membranes. Blots were incubated with main Rabbit Polyclonal to COX41 antibodies against -actin, PARP, pAMPK, and pS6K. After washing, the blots were incubated with HRP-coupled secondary antibodies. Angelicin After additional washing, the proteins were visualized by luminol reagent under Intas imager (Intas, Germany). Densitometric analysis was performed on scanned images using ImageJ software (National Institutes of Health) [28]. Statistical analysis EC50 and IC50 values were estimated after fitted the pooled data from at least three impartial experiments to the four-parameter logistic equation using GraphPad Prism version 4.00 for Windows (GraphPad, USA). Data were offered as mean??standard error of the mean (mean??SEM). Statistical comparison was analyzed using Students test. (*), (**), and (***) indicate value?