TRAIL (TNF-related apoptosis-inducing ligand) and its derivatives are potentials for anticancer therapy due to the selective induction of apoptosis in tumor cells upon binding to death receptors DR4 or DR5. Previously, we generated a DR5-selective TRAIL mutant variant DR5-B overcoming receptor-dependent resistance of tumor cells to TRAIL. In the current study, we improved the antitumor activity of DR5-B by fusion with a tumor-homing iRGD peptide, which is known to enhance the drug penetration into tumor tissues. The obtained bispecific fusion protein DR5-B-iRGD exhibited dual affinity for DR5 and integrin αvβ3 receptors. DR5-B-iRGD penetrated into U-87 tumor spheroids faster than DR5-B and demonstrated an enhanced antitumor effect in human glioblastoma cell lines T98G and U-87, as well as in primary patient-derived glioblastoma neurospheres in vitro. Additionally, DR5-B-iRGD was highly effective in a xenograft mouse model of the U-87 human glioblastoma cell line in vivo. We suggest that DR5-B-iRGD may become a promising candidate for targeted therapy for glioblastoma.

Glioblastoma multiforme (GBM) is the most aggressive type of brain cancer with a poor prognosis. GBM cells, developing in the environment of neural tissue, often exploit neurotransmitters and their receptors to promote their growth and invasion. Nicotinic acetylcholine receptors (nAChRs) play a crucial role in the central nervous system signal transmission, are widely represented in the brain, the GBM cells expressing several subtypes of nAChRs which are suggested to transmit signals from neurons, thus promoting tumor invasion and growth. Functional alpha1*, alpha7 and alpha9 nAChRs are demonstrated on several patient-derived GBM neurosphere cultures and U87MG cell line using neurotoxins and fluorescent calcium assay. Selective alpha1*, alpha7 and alpha9 nAChR antagonists stimulated cell growth in presence of nicotinic agonists. Choline, normally present in blood, is capable of activating alpha1*, alpha7 and alpha9 nAChR subtypes, mediates the antagonist's influence on cell proliferation. Several cultivating conditions have been shown to directly change sensitivity of primary GBM lines to nAChR ligands. Thus, results of in vitro testing of nAChR ligands on GBM lines should be interpreted and reviewed in cell culture conditions-aware manner.

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor. One of the reasons for the resistance of GBM to treatment is the extreme heterogeneity of the tumor and, in particular, the presence of cancer stem cells (CSCs) in the population of glioblastoma cells. In this work, we investigated the effect of conditions that reduce the proportion of CSCs in the GBM cell population on the levels of long noncoding RNAs (lincROR and MALAT1) involved in the formation of the phenotype of glioblastoma cancer stem cells. We have shown that culturing under conditions that cause a decrease in cell stemness (when fetal bovine serum is added to the culture medium) affected the content of these transcripts: in the cells of most of the analyzed lines, a decrease in the level of the positive stemness regulator lincROR and an increase in the content of MALAT1 were noted.