Cirak Y.Varol U.Atmaca H.Kisim A.Sezgin C.Karabulut B.Uzunoglu S.Uslu R.Karaca B.2024-07-222024-07-2220121464410Xhttp://akademikarsiv.cbu.edu.tr:4000/handle/123456789/17535OBJECTIVES • To investigate if the cytotoxic and apoptotic effect of zoledronic acid (ZA) can be enhanced by the addition of the serine/threonine protein phosphatase inhibitors calyculin A (CA) and okadaic acid (OA) in hormone and drug refractory prostate cancer cells, PC-3 and DU-145. • To discover the effect of these combination treatments on phosphatase 1 (PP1) and PP2A protein expression levels in prostate cancer cells. MATERIALS AND METHODS • An XTT cell viability assay was used to determine cytotoxicity. • Apoptosis was evaluated by enzymelinked immunosorbent assay (ELISA) using a Cell Death Detection ELISA Plus Kit and verifi ed by measuring caspase 3/7 enzyme activity. • The PP1 and PP2A enzyme activities were evaluated by serine/threonine phosphatase ELISA and expression levels of PP1 and PP2A proteins were then re-assessed by Western blot RESULTS • Combination of ZA with either CA or OA showed synergistic cytotoxicity and apoptosis compared with any agent alone in both PC-3 and DU-145 prostate cancer cells. • The combination of ZA with phosphatase inhibitors resulted in enhanced suppression of both PP1 and PP2A enzyme activity andprotein levels, which was more overt with the ZA/CA combination. CONCLUSION • Results from our study increase the translational potential of our in vitro fi ndings and offer the basic rationale for the design of new combinatory strategies with ZA and phosphatase inhibitors for the treatment of prostate cancer, which may become resistant to conventional therapy. © 2012 B J U I N T E R N A T I O N A L.EnglishApoptosisBlotting, WesternBone Density Conservation AgentsCell Line, TumorCell ProliferationDiphosphonatesEnzyme-Linked Immunosorbent AssayHumansImidazolesMalePhosphoprotein PhosphatasesProstatic NeoplasmsProtein Phosphatase 1Protein Phosphatase 2calyculin Acaspase 3caspase 7okadaic acidphosphoprotein phosphatase 1phosphoprotein phosphatase 2Azoledronic acidbisphosphonic acid derivativebone density conservation agentimidazole derivativephosphoprotein phosphatasephosphoprotein phosphatase 1phosphoprotein phosphatase 2zoledronic acidMLCSMLOWNantineoplastic activityapoptosisarticlecancer cell culturecancer combination chemotherapycell viabilityconcentration responsecontrolled studydrug cytotoxicitydrug potentiationenzyme activityenzyme inhibitionenzyme linked immunosorbent assayhumanhuman cellIC 50in vitro studymalemonotherapypriority journalprotein expressionWestern blottingapoptosisbiosynthesiscell proliferationcomparative studydrug antagonismdrug effectmetabolismpathologyprostate tumortumor cell lineArticle10.1111/j.1464-410X.2012.11392.x