A comparative study of hollow copper sulfide nanoparticles and hollow gold nanospheres on degradability and toxicity.

Gold and copper nanoparticles have been widely investigated for photothermal therapy of cancer. However, degradability and toxicity of these nanoparticles remain concerns. Here, we compare hollow CuS nanoparticles (HCuSNPs) with hollow gold nanospheres (HAuNS) in similar particle sizes and morphology following intravenous administration to mice. The injected pegylated HCuSNPs (PEG-HCuSNPs) are eliminated through both hepatobiliary (67 percentage of injected dose, %ID) and renal (23 %ID) excretion within one month postinjection. By contrast, 3.98 %ID of Au is excreted from liver and kidney within one month after iv injection of pegylated HAuNS (PEG-HAuNS). Comparatively, PEG-HAuNS are almost nonmetabolizable, while PEG-HCuSNPs are considered biodegradable nanoparticles. PEG-HCuSNPs do not show significant toxicity by histological or blood chemistry analysis. Principal component analysis and 2-D peak distribution plots of data from matrix-assisted laser desorption ionization-time-of-flight imaging mass spectrometry (MALDI-TOF IMS) of liver tissues demonstrated a reversible change in the proteomic profile in mice receiving PEG-HCuSNPs. This is attributed to slow dissociation of Cu ion from CuS nanoparticles along with effective Cu elimination for maintaining homeostasis. Nonetheless, an irreversible change in the proteomic profile is observed in the liver from mice receiving PEG-HAuNS by analysis of MALDI-TOF IMS data, probably due to the nonmetabolizability of Au. This finding correlates with the elevated serum lactate dehydrogenase at 3 months after PEG-HAuNS injection, indicating potential long-term toxicity. The comparative results between the two types of nanoparticles will advance the development of HCuSNPs as a new class of biodegradable inorganic nanomaterials for photothermal therapy.

Paclitaxel disrupts polarized entry of membrane-permeable C6 ceramide into ovarian cancer cells resulting in synchronous induction of cell death.

Exogenous cell-permeable C6 ceramide has been demonstrated to act synergistically with chemotherapeutic drugs, including paclitaxel, cisplatin, doxorubicin and the histone deacetylase inhibitor, trichostatin A, to induce cell death in a variety of cancer cells. We previously demonstrated that C6 ceramide and paclitaxel function synergistically to induce ovarian cancer cell death via modulation of the PI3/AKT cell survival pathway. In the present study, the entry pattern of C6 ceramide into ovarian cancer cells was investigated using fluorescent short chain C6-NBD sphingomyelin (C6-NBD). Confocal microscopy revealed that C6-NBD enters the cells in a polarized pattern, characterized by marked signals at one cellular end, representing a likely mitosis initiation site. Pretreatment of the cells with filipin, an inhibitor of the lipid raft/caveolae endocytosis pathway, decreases C6-NBD entry into the cells. A pretreatment with the water channel inhibitor, CuSO4, was also found to reduce the entry of C6-NBD. Notably, the pretreatment with paclitaxel was shown to disrupt the polarized entry of C6-NBD into the cells, resulting in an even distribution of C6-NBD in the cytoplasm. In addition, the pretreatment of the cells with paclitaxel destabilized the cytoskeletal proteins, releasing an increased number of short tubulin fragments. The results of the present study indicate that C6 ceramide preferentially enters the cells via a predetermined initiation site of mitosis. In addition to diffusion, short chain C6 ceramide may also enter cells via water channels and caveolae-mediated endocytosis. Paclitaxel disrupts the cell cytoskeleton and induces an even distribution of C6 ceramide in the cytoplasm resulting in synergistic ovarian cancer cell death.

N-acetylcysteine potentiates doxorubicin-induced ATM and p53 activation in ovarian cancer cells.

Doxorubicin has been used clinically to treat various types of cancer, and yet the molecular mode of actions of doxorubicin remains to be fully unraveled. In this study, we investigated the effect of doxorubicin on cultured ovarian cancer cells (CaOV3). MTT assay data showed that doxorubicin inhibits cell proliferation in a time- and dose-dependent manner. Phagokinetic cell motility assay data indicated that doxorubicin inhibits both basal level and EGF-induced cell migration in CaOV3 cells. Confocal microscopic data revealed that doxorubicin induces reorganization of cytoskeletal proteins including actin, tubulin and vimentin. Doxorubicin induces phosphorylation of p53 at Ser15 and 20, acetylation of p53 and ATM activation. Doxorubicin also induces phosphorylation of histone H2AX at Ser139. Interestingly, doxorubicin also inhibits mTOR activity, measured by phosphorylation of S6 ribosomal protein. Pretreatment of CaOV3 cells with antioxidant N-acetylcysteine (NAC), but not pyrrolidine dithiocarbamate (PDTC) potentiates doxorubicin-induced phosphorylation of p53 and ATM. Collectively, we conclude that doxorubicin induces ATM/p53 activation leading to reorganization of cytoskeletal networks, inhibition of mTOR activity, and inhibition of cell proliferation and migration. Our data also suggest that removal of oxidants by antioxidants such as NAC may enhance the efficacy of doxorubicin in vivo.