Methotrexate (MTX), an analog of folic acid (FA), is a drug widely used in cancer treatment. To prevent its potential toxicity and enhance therapeutic efficacy, targeted drug delivery systems, especially nanotechnology–folate platforms, are a central strategy. Gold nanoparticles (AuNPs) are promising candidates to be used as drug delivery systems because of their small particle sizes and their inertness for the body. In this study, glutathione (GSH)-coated FA-modified spherical AuNPs (5.6 nm) were successfully synthesized, and the anticancer activity of novel MTX-loaded (MTX/Au-GSH-FA) NPs (11 nm) was examined. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) results showed that MTX/AuNPs possess spherical morphology, nanoscaled particle size, narrow size distribution, and good stability. In vitro studies showed that cytotoxicity of MTX/Au-GSH-FA to folate receptor-positive (FR+) human brain (U-87 MG) and cervical (HeLa) cancer cells enhanced significantly (∼3 and ∼10 fold, respectively) compared to free MTX while there was no significant effect in FR−negative human cell lines A549 (lung carcinoma), PC3 (prostate carcinoma), HEK-293 (healthy embryonic kidney). Moreover, the receptor specificity of the conjugate was shown by fluorescent microscopic imaging. In conclusion, these results indicate that the synthesized novel MTX/Au-GSH-FA NP complex seems to be a good candidate for effective and targeted delivery in FR+ cancer therapy.

GBM cells can easily gain resistance to conventional therapy, and therefore treatment of glioblastoma multiforme (GBM) is difficult. One of the hallmark proteins known to be responsible for this resistance is heat shock protein 27 (Hsp27) which has a key role in the cell survival. Resveratrol, a natural compound, exhibits antitumor effects against GBM, but there are no reports regarding its effect on Hsp27 expression in gliomas. The aim of the present study was to asses the effect of resveratrol on Hsp27 expression and apoptosis in non-transfected and transfected U-87 MG human glioblastoma cells. In order to block the Hsp27 expression, siRNA transfection was performed. Non-transfected and transfected cells were treated with either 10 or 15 μM resveratrol. The effects of resveratrol were compared with quercetin, a well-known Hsp27 inhibitor. Resveratrol was found to induce apoptosis more effectively than quercetin. Our data showed that resveratrol induces dose- and time-dependent cell death. We also determined that silencing of Hsp27 with siRNA makes the cells more vulnerable to apoptosis upon resveratrol treatment. The highest effect was observed in the 15 μM resveratrol and 25 nM siRNA combination group (suppressed Hsp27 expression by 93.4% and induced apoptosis by 101.2%). This study is the first report showing that resveratrol reduces Hsp27 levels, and siRNA-mediated Hsp27 silencing enhances the therapeutic effects of resveratrol in glioma cells. Our results suggest that resveratrol administration in combination with Hsp27 silencing has a potential to be used as a candidate for GBM treatment.

Extracts of mistletoe (Viscum album) are intensively used in complementary medicine, but their mechanisms are not fully understood in most cases, and the effects on metabolism have not been investigated in detail. However, some biologically active natural products are well known to provoke unexpected cellular responses. They reduce overexpression of heat shock proteins (Hsps) in cancer cells. The aim of the current study was to determine whether methanolic extract of V. album, which possesses antioxidant activity, has an effect on expression levels of Hsp27 and 14-3-3 proteins in a C6 glioma cell line. For the first time, the apoptosis-inducing effect of this extract was also determined via caspase-3 activation in the cells. Overexpression of Hsps was induced by heat shock at 42°C for 1 h. Expression levels of Hsp27 and 14-3-3 proteins were determined using Western blot analysis. The apoptosis-inducing effect was also evaluated via caspase-3 activation in C6 glioma cells. Pretreatment of the cells with a nontoxic dose (100 μg/mL) of V. album extract before heat shock significantly reduced expression levels of Hsp27 (73%) and 14-3-3β (124%), 14-3-3γ (23%), and 14-3-3ζ (84%) proteins. Pretreatment with the extract before heat shock increased apoptosis via caspase-3 activation (60%) in C6 glioma cells. This result suggested that the methanolic extract of V. album downregulates expression of Hsp27 and 14-3-3 chaperone proteins and induces apoptosis, which warrants further exploration as a potential bioactive compound for cancer therapy.