Shock wave-induced ATP release from osteosarcoma U2OS cells promotes cellular uptake and cytotoxicity of methotrexate

Abstract

BackgroundOsteosarcoma is the most prevalent primary malignant bone tumor, but treatment is difficult and prognosis remains poor. Recently, large-dose chemotherapy has been shown to improve outcome but this approach can cause many side effects. Minimizing the dose of chemotherapeutic drugs and optimizing their curative effects is a current goal in the management of osteosarcoma patients.MethodsIn our study, trypan blue dye exclusion assay was performed to investigate the optimal conditions for the sensitization of osteosarcoma U2OS cells. Cellular uptake of the fluorophores Lucifer Yellow CH dilithium salt and Calcein was measured by qualitative and quantitative methods. Human MTX ELISA Kit and MTT assay were used to assess the outcome for osteosarcoma U2OS cells in the present of shock wave and methotrexate. To explore the mechanism, P2X7 receptor in U2OS cells was detected by immunofluorescence and the extracellular ATP levels was detected by ATP assay kit. All data were analyzed using SPSS17.0 statistical software. Comparisons were made with t test between two groups.ResultsTreatment of human osteosarcoma U2OS cells with up to 450 shock wave pulses at 7 kV or up to 200 shock wave pulses at 14 kV had little effect on cell viability. However, this shock wave treatment significantly promoted the uptake of Calcein and Lucifer Yellow CH by osteosarcoma U2OS cells. Importantly, shock wave treatment also significantly enhanced the uptake of the chemotherapy drug methotrexate and increased the rate of methotrexate-induced apoptosis. We found that shock wave treatment increased the extracellular concentration of ATP and that KN62, an inhibitor of P2X7 receptor reduced the capacity methotrexate-induced apoptosis.ConclusionsOur results suggest that shock wave treatment promotes methotrexate-induced apoptosis by altering cell membrane permeability in a P2X7 receptor-dependent manner. Shock wave treatment may thus represent a possible adjuvant therapy for osteosarcoma.

Extracellular ATP: A Feasible Target for Cancer Therapy

“…An interesting extension of P2X7R-targeting in cancer therapy comes from the finding that eATP increases plasma membrane permeability for cytotoxic molecules (e.g., doxorubicin, ethidium bromide, thiocyanate) via P2X7R pore opening [ 159 , 160 ]. More recently, a mechanism has been proposed by which shock wave treatment of human osteosarcoma U2OS cells induces the efflux of intracellular ATP, which promotes the intake of methotrexate (MTX) by altering plasma membrane permeability via P2X7R activation, thus leading to MTX-induced apoptosis [ 161 ].…”

The P2X7 Receptor in Inflammatory Diseases: Angel or Demon?

“…Moreover, when combined with cisplatin or mitomycin C, hyperthermia, and eATP potentiate chemotherapy cytotoxicity, enhancing the therapeutic efficacy of conventional cancer treatments. Likewise hyperthermia, shock wave and photodynamic therapy alter cells membrane permeability via ATP-P2X7 signaling, boosting hydrophilic drugs intake, and cell death induction (Pacheco et al, 2016 ; Qi et al, 2016 ). P2X7 receptor activation also modulates radiotherapy-killing activity (Gehring et al, 2012 , 2015 ).…”

Cellular signaling pathways modulated by low-intensity extracorporeal shock wave therapy

“…In this study shockwave treatment did not significantly inhibit cell survival (viability > 95%) if the dose was restricted to 200 or fewer pulses. Cell survival declines in a dose dependent fashion as the number of shocks exceeds 200 51 .…”