When nitric oxide (NO) donor drugs combine with doxorubicin they potentiate doxorubicin, anticancer effects. However, limited NO payloads, too rapid NO release, and the lack of organ or tissue specificity have limited the clinical utility of currently available NO donors. Hence, there is a great need to design tuneable NO donors which can enhance the efficacy of currently available chemotherapeutic drugs such as doxorubicin.
A highly stable NO-releasing compound was synthesized by nitrosation of hydrophobic and sterically hindered thiol to form tert-dodecane S-nitrosothiol (tDodSNO). It was then encapsulated in a polymer (SMA) to make stable and hydrophilic NO-releasing NPs (SMA-tDodSNO). The dose (1-100 μM) dependent cytotoxicity of SMA-tDodSNO alone or combined with doxorubicin on 4T1 (mouse breast cancer) cells were assessed by MTT and cell cycle analysis. In addition, the effect of SMA-tDodSNO and Dox were evaluated on mitochondrial oxidative stress, mitochondrial membrane potential, intracellular calcium level, and ERK1/2 activity.
Incubation of 4T1 cells with SMA-tDodSNO at μM concentrations showed a concentration-dependent decrease in cell survival. When the NPs were combined with doxorubicin they significantly (p<0.001) increased the doxorubicin cytotoxicity. In addition, the combination significantly enhanced mitochondrial oxidative stress and mitochondrial membrane permeabilization when compared to only doxorubicin-treated cells. Evaluation of intracellular calcium level via calcium sensitive fluorophore (Indo-1) demonstrated that the SMA-tDodSNO caused a boost in the cytosolic calcium level and over-activation of ERK1/2 pathway and apoptosis.
We designed a novel NO-releasing nanoparticle, SMA-tDodSNO, which showed controlled NO release and significant cytotoxicity in 4T1 cells. When combined with doxorubicin it increased the anticancer potency of doxorubicin via enhanced mitochondrial oxidative stress and elevation of cytosolic calcium level.
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University of Otago.
University of Otago.
All authors have declared no conflicts of interest.