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.

Abstract 5247: Human melanoma cells resist oxidative stress due to overactive MEK/ERK and AKT/mTOR pathways and overproduction of melanin

Melanoma is considered as one of the most aggressive and less treatable cancers. While various models of mechanisms have been proposed, the transformation from tranquil melanocytes to invasive melanoma cells remains an enigma. Alteration of cellular redox status has been suggested to be associated with cellular transformation. We compared primary human melanocytes and melanoma cells and their responses to oxidative stress. Both cells were treated with H2O2 at doses between 5 and 250μM. Microscopic data showed that melanoma cells are more resistant to H2O2 treatment. Western blot and confocal microscopic data showed that in melanoma cells, H2O2 does not induce CRT translocation which is considered as a mechanism through which melanocytes surrender to oxidative stress and induces immunogenic cell death. Furthermore, Western blot analysis showed that melanoma cells express EGFR, responsive to EGF treatment and have constitutive activation of AKT and mTOR, which are all related to better survival. In contrast, in the primary human melanocytes, EGFR expression is almost undetectable. And confocal microscopic data confirm this observation. Treatments of cells with MEK/ERK inhibitor U0126 and PI3K/AKT inhibitor LY294002 attenuates S6 phosphorylation. We also observed that in melanoma cells, but not in melanocytes, low dose (5 to 250μM) of H2O2 induces melanin production that is recognized to protect from further oxidative stress. Collectively, our data suggest that active MEK/ERK and AKT/mTOR pathways and up-regulation of melanin production contribute to the resistance of melanoma cells to oxidative stress and attribute to the aggressiveness of melanoma. Our data provides insights into the understanding of the molecular mechanisms of the transformation from melanocytes to melanoma and support the notion from the most recently published proteomic studies that EGFR remains one of the most important targets for better clinical management of melanoma.

Citation Format: David Calianese, Garrett Cammarata, Gabriella Brum, Kevin Szulak, Charles Best, Katelyn Higgins, Yinsheng Wan. Human melanoma cells resist oxidative stress due to overactive MEK/ERK and AKT/mTOR pathways and overproduction of melanin. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5247. doi:10.1158/1538-7445.AM2013-5247

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

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.

Abstract 3734: 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 is demonstrated to act synergistically with chemotherapeutic drugs: paclitaxel, cisplatin, doxorubicin and histone deacetylase inhibitor trichostatin A (TSA) to induce cell death in a variety of cancer cells. We previously showed that C6 ceramide and paclitaxel act synergistically to induce ovarian cancer cell death via modulation of PI3/AKT cell survival pathway. This current study is focused on the process of C6 ceramide into the cell and its behavior during apoptosis. We investigated the entry pattern of C6 ceramide into ovarian cancer cells using fluorescent short chain C6-NBD sphingomyelin (or C6-NBD). As imaged with confocal microscopy, we observed that C6-NBD enters cells in a polarized pattern, characterized by strong signals at one cellular end, a probable mitosis initiation site. Pretreatment of the cells with filipin, an inhibitor of the raft/caveolae endocytosis pathway, decreases C6-NBD entry into cells. Pretreatment of water channel inhibitor CuSO4 also reduces entry of C6-NBD. Interestingly, pretreatment of cells with paclitaxel disrupts the polarized entry of C6-NBD into the cells, resulting in even distribution of C6-NBD in the cytoplasm. Further studies show that pretreatment of the cells with paclitaxel destabilizes cytoskeletal proteins, releasing increased number of short fragments of tubulins. The data suggests that C6 ceramide enters the cells preferably through a predetermined initial site of mitosis. In addition to diffusion, short chain C6 ceramide enters cells also via water channels and caveolae-mediated endocytosis. Paclitaxel disrupts cytoskeletons and induces an even distribution of C6 ceramide in the cytoplasm resulting in synergistic ovarian cancer cell death.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3734. doi:1538-7445.AM2012-3734