Cundong Fan

Positive Surface Charge Enhances Selective Cellular Uptake and Anticancer Efficacy of Selenium Nanoparticles

Surface charge plays a key role in cellular uptake and biological actions of nanomaterials. Selenium nanoparticles (SeNPs) are novel Se species with potent anticancer activity and low toxicity. This study constructed positively charged SeNPs by chitosan surface decoration to achieve selective cellular uptake and enhanced anticancer efficacy. The results of structure characterization revealed that hydroxyl groups in chitosan reacted with SeO(3)(2-) ion to form special chain-shaped intermediates, which could be decomposed to form crystals upon reduction by ascorbic acid. The initial colloids nucleated and then assembled into spherical SeNPs. The positive charge of the NH(3)(+) group on the outer surface of the nanoparticles contributed to the high stability in aqueous solutions. Moreover, a panel of four human cancer cell lines were found to be susceptible to SeNPs, with IC(50) values ranging from 22.7 to 49.3 μM. Chitosan surface decoration of SeNPs significantly enhanced the selective uptake by endocytosis in cancer cells and thus amplified the anticancer efficacy. Treatment of the A375 melanoma cells with chitosan-SeNPs led to dose-dependent apoptosis, as evidenced by DNA fragmentation and phosphatidylserine translocation. Our results suggest that the use of positively charged chitosan as a surface decorator could be a simple and attractive approach to achieve selective uptake and anticancer action of nanomaterials in cancer cells.

Enhancement of cell permeabilization apoptosis-inducing activity of selenium nanoparticles by ATP surface decoration

UNLABELLED A simple method for preparation of adenosine triphosphate (ATP) surface-functionalized selenium nanoparticles (SeNPs@ATP) with enhanced cell permeabilization and anticancer activity has been demonstrated in the study reported in this article. Spherical SeNPs were decorated with ATP by strong adsorption through an Se-N bond, leading to the highly stable structure of the conjugates. ATP surface decoration significantly enhanced the cellular uptake and anticancer activity of SeNPs. Induction of apoptosis in HepG2 human hepatocellular carcinoma cells by SeNPs@ATP was evidenced by accumulation of the sub-G1 cell population, phosphatidylserine exposure, DNA fragmentation, PARP cleavage and caspase activation. Further studies found that SeNPs@ATP treatment triggered the depletion of mitochondrial membrane potential and reactive oxygen species (ROS) overproduction. Our results demonstrate that the use of ATP as a surface decorator of SeNPs is a novel strategy to achieve anticancer synergy. SeNPs@ATP may be a candidate for further evaluation as a chemotherapeutic agent for human cancers. FROM THE CLINICAL EDITOR In this paper, adenosine triphosphate (ATP) surface-functionalized selenium nanoparticles are discussed as cell-penetrating anticancer agents. Conjugates are stable and ATP functionalization greatly enhances the apoptosis induction properties of the selenium nanoparticles in HepG2 human hepatocellular carcinoma cells.

Selenocystine potentiates cancer cell apoptosis induced by 5-fluorouracil by triggering reactive oxygen species-mediated DNA damage and inactivation of the ERK pathway.

5-Fluorouracil (5-FU)-based chemotherapy as a first-line treatment is quite limited, because of its inefficiency and clinical resistance to it. The search for chemosensitizers that could augment its efficiency and overcome the drug resistance to 5-FU has kindled great interest among scientists. Selenocystine (SeC), a naturally occurring selenoamino acid, displayed broad-spectrum anticancer activity in our previous studies. This study demonstrates that SeC acts as an effective enhancer of 5-FU-induced apoptosis in A375 human melanoma cells through induction of mitochondria-mediated apoptosis with the involvement of DNA damage-mediated p53 phosphorylation and ERK inactivation. Pretreatment of the cells with SeC significantly enhanced 5-FU-induced loss of mitochondrial membrane potential (∆ψm) by regulating the expression levels of Bcl-2 family proteins. SeC and 5-FU in combination also triggered cell oxidative stress through regulation of the intracellular redox system and led to DNA damage and inactivation of ERK and AKT. Moreover, inhibitors of ERK and AKT effectively enhanced the apoptotic cell death induced by the combined treatment. However, pretreatment of the cells with glutathione reversed the apoptosis induced by SeC and 5-FU and recovered the expression of ERK and AKT inactivation, which revealed the important role of reactive oxygen species in cell apoptosis and regulation of ERK and AKT pathways. Taken together, our results suggest that a strategy of using SeC and 5-FU in combination could be a highly efficient way to achieve anticancer synergism.

Functionalized selenium nanoparticles with nephroprotective activity, the important roles of ROS-mediated signaling pathways

The most frequent adverse effect of cisplatin-based chemotherapy is nephrotoxicity. Oxidative stress has been implicated as an important mechanism in the pathogenesis of cisplatin-induced nephrotoxicity. In the present study, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) surface-functionalized selenium nanoparticles (Se@Trolox) with enhanced antioxidant activity have been prepared by self-assembly of trolox on the surface of the nanoparticles, and their nephroprotective effects have been investigated. Functionalization by trolox significantly enhanced cell uptake and in vitro antioxidant activities of the nanoparticles. In addition, pretreatment with Se@Trolox dose-dependently blocked cisplatin-induced cell growth inhibition against HK-2 cells. Mechanistic investigation suggested that Se@Trolox markedly prevented cisplatin-induced apoptosis in HK-2 cells, as evidenced by inhibition of chromatin condensation, DNA fragmentation, PARP cleavage and activation of caspase-3. Furthermore, Se@Trolox effectively blocked the cisplatin-induced reactive oxygen species (ROS) accumulation, activation of AKT and MAPK signaling and DNA damage-mediated p53 phosphorylation in HK-2 cells. Taken together, our findings suggest that Se@Trolox is a promising Se species with potential application in prevention of cisplatin-induced renal injury.

Strategy to enhance the anticancer efficacy of X-ray radiotherapy in melanoma cells by platinum complexes, the role of ROS-mediated signaling pathways

Radiotherapy plays an important role in treatment of cancers with low toxicity to the surrounding normal tissues. However, it still fails to eradicate hypoxic tumors due to the occurrence of radioresistance. Therefore, the search for new radiation sensitizers is of great significance. Platinum (Pt) complexes have been identified as potential radiation sensitizers to increase the sensitivity of cancer cells to radiotherapy. In the present study, we have synthesized four Pt complexes containing (2 - benzimidazole [4, 5-f] - [1, 10] phenanthroline) ligand and found that they could effectively enhance the X-ray-induced growth inhibition against A375 human melanoma cells through induction of G2/M cell cycle arrest. In contrast, they showed much lower cytotoxicity toward human normal cells. The complexes also dramatically inhibited the TrxR activity and caused intracellular ROS overproduction, due to the Auger electron effect of heavy metal element under X-ray radiation. Excessive ROS triggered DNA damage and activated downstream signaling pathways, including the phosphorylation of p53 and p38MAPK, and down-regulation of phosphorylated AKT and ERK, finally resulted in increase of radiosensitivity and inhibition of tumor reproduction. Taken together, our results suggest that the synthetic Pt complexes could be further developed as sensitizers of X-ray radiotherapy.

Arene ruthenium(II) complexes induce S-phase arrest in MG-63 cells through stabilization of c-Myc G-quadruplex DNA

A series of arene ruthenium(II) complexes coordinated by phenanthroimidazole derivatives have been synthesized and evaluated for their in vitro anticancer activities. It has been found that these types of arene Ru(II) complexes, especially [(C6H6)Ru(o-ClPIP)Cl]Cl·2H2O (2a), exhibited acceptable antiproliferative activity against several human cancer cell lines but with low toxicity towards normal HK-2 human cells. Mechanistic studies revealed that 2a-induced growth inhibition against osteosarcoma MG-63 cells was mainly caused by S-phase cell cycle arrest, which was confirmed by the down-regulation of cyclin A and CDK2 using western blot analysis of protein levels. Furthermore, studies using comet assay at single cell level indicated that 2a triggered DNA damage in MG-63 cells, and subsequently initiated S-phase arrest, as shown by the up-regulation of phosphorylated p53 and histone. Moreover, exposure of MG-63 cells to 2a resulted in the down-regulation of c-Myc protein expression. The in vitro DNA-binding behaviors also indicated that 2a could stabilize c-Myc G-quadruplex DNA (G4-DNA) by affecting its conformation. In conclusion, these results suggest that arene Ru(II) complexes coordinated by phenanthroimidazole derivatives serve as c-Myc G4-DNA stabilizers that could induce S-phase arrest in cancer cells by triggering DNA damage, which suggest that these complexes may act as potential candidates for the treatment of human malignant osteosarcoma.