<p>AT101-Loaded Cubosomes as an Alternative for Improved Glioblastoma Therapy</p>

Abstract

Introduction: AT101, the R-(-)-enantiomer of the cottonseed-derived polyphenol gossypol, is a promising drug in glioblastoma multiforme (GBM) therapy due to its ability to trigger autophagic cell death but also to facilitate apoptosis in tumor cells. It does have some limitations such as poor solubility in water-based media and consequent low bioavailability, which affect its response rate during treatment. To overcome this drawback and to improve the anti-cancer potential of AT101, the use of cubosome-based formulation for AT101 drug delivery has been proposed. This is the first report on the use of cubosomes as AT101 drug carriers in GBM cells. Materials and Methods: Cubosomes loaded with AT101 were prepared from glyceryl monooleate (GMO) and the surfactant Pluronic F-127 using the top-down approach. The drug was introduced into the lipid prior to dispersion. Prepared formulations were then subjected to complex physicochemical and biological characterization. Results: Formulations of AT101-loaded cubosomes were highly stable colloids with a high drug entrapment efficiency (97.7%) and a continuous, sustained drug release approaching 35% over 72 h. Using selective and sensitive NMR diffusometry, the drug was shown to be efficiently bound to the lipid-based cubosomes. In vitro imaging studies showed the high efficiency of cubosomal nanoparticles uptake into GBM cells, as well as their marked ability to penetrate into tumor spheroids. Treatment of GBM cells with the AT101-loaded cubosomes, but not with the free drug, induced cytoskeletal rearrangement and shortening of actin fibers. The prepared nanoparticles revealed stronger in vitro cytotoxic effects against GBM cells (A172 and LN229 cell lines), than against normal brain cells (SVGA and HMC3 cell lines). Conclusion: The results indicate that GMO-AT101 cubosome formulations are a promising basic tool for alternative approaches to GBM treatment.

Effects of the Anti-Tumorigenic Agent AT101 on Human Glioblastoma Cells in the Microenvironmental Glioma Stem Cell Niche

“…Thus, an urgent need exists to develop alternative, more effective treatment strategies. In addition to the preferred chemotherapeutic drug TMZ, a promising candidate for the treatment of GBMs is AT101 [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. AT101 is able to trigger autophagic, mitophagic, or apoptotic cell death by versatile mechanisms of action as the inhibition of Bcl-2 proteins, the induction of mitochondrial dysfunction, or by modulating serval signaling pathways in a specific manner [ 22 , 23 , 24 , 25 , 26 , 41 ].…”

“…Here, in our opinion, a local application of AT101 directly in the tumor resection cavity (e.g., by nanoparticles or (biodegradable) drug carrier devices) together with systemic treatment with TMZ will be the most promising approach. Using this local treatment strategy of AT101, it is possible to overcome the known relatively low bioavailability of AT101 after systemic treatment [ 20 ], and to analyze the potential of AT101 to eradicate TMZ-resistant glioblastoma cells, which in most cases are characterized by pronounced stem-like cell characteristics [ 17 ]. Further, since it was shown that AT101 was a competent enhancer of radiation-induced apoptosis in head and neck squamous cell carcinoma in vitro [ 56 ], a combination of AT101 and radiation might also be feasible to treat glioblastomas more efficiently.…”

“…RNA of cells was isolated with the TRIzol ® Reagent (Thermo Fisher Scientific) or with the ARCTURUS ® PicoPure ® RNA Isolation Kit (Applied Biosystems, Waltham, MA, USA) according to the manufacturer’s instructions. DNase digestion, cDNA synthesis, and qRT-PCR were performed as described before [ 17 , 18 , 19 , 20 ] using TaqMan primer probes (Applied Biosystems): CXCL11 (Hs00171138_m1), CXCL12 (Hs00171022_m1), CXCL16 (Hs00222859_m1), CX3CL1 (Hs00171086_m1), CXCR4 (Hs00237052_m1), CXCR6 (Hs00174843_m1), CXCR7 (Hs00664172_s1), CX3CR1 (Hs00365842_m1), GAPDH (Hs99999905_m1), interleukin-6 (IL-6) (Hs00985639_m1), interleukin-6 receptor (IL-6R) (Hs01075664_m1), krüppel-like factor 4 (KLF4) (Hs00358836_m1), Nestin (Hs00707120_s1), octamer binding transcription factor (OCT4) (Hs00999632_g1), transforming growth factor-β (TGF-β) (Hs00171257_m1), and TGF-β receptor 1 (TGF-βR1). Cycles of threshold (C T ) were determined, and ΔC T values of each sample were calculated as C T gene of interest − C T GAPDH .…”

“…Thus, there is an urgent need to develop alternative treatment strategies in order to overcome the heterogeneity-based chemoresistance of GBMs. Besides the preferred chemotherapeutic drug temozolomide (TMZ), a promising candidate for the treatment of GBMs is AT101, the R(-) enantiomer of the naturally occurring cottonseed-derived polyphenol gossypol [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ].…”

“…AT101 is characterized by versatile modes of action resulting in, e.g., anti-inflammatory, anti-oxidative, or especially anti-tumorigenic effects (alone or in combination with other drugs) on several tumor entities, including GBMs [ 16 , 17 , 18 , 19 , 20 , 21 ]. AT101 was able to trigger autophagic, mitophagic, or apoptotic cell death by competitive inhibition of Bcl-2 proteins [ 22 , 23 , 24 , 25 ].…”