Gelatin nanoparticles loaded with 3-alkylpyridinium salt APS7, an analog of marine toxin, are a promising support in human lung cancer therapy.

This study demonstrates the potential of gelatin nanoparticles as a nanodelivery system for antagonists of nicotinic acetylcholine receptors (nAChRs) to improve chemotherapy efficacy and reduce off-target effects. Too often, chemotherapy for lung cancer does not lead to satisfactory results. Therefore, new approaches directed at multiple pharmacological targets in cancer therapy are being developed. Following the activation of nAChRs (e.g. by nicotine), cancer cells begin to proliferate and become more resistant to chemotherapy-induced apoptosis. This work shows that the 3-alkylpyridinium salt, APS7, a synthetic analog of a toxin from the marine sponge Haliclona (Rhizoneira) sarai, acts as an nAChR antagonist that inhibits the pro-proliferative and anti-apoptotic effects of nicotine on A549 human lung adenocarcinoma cells. In this study, gelatin-based nanoparticles filled with APS7 (APS7-GNPs) were prepared and their effects on A549 cells were compared with that of free APS7. Both APS7 and APS7-GNPs inhibited Ca2+ influx and increased the efficacy of cisplatin chemotherapy in nicotine-stimulated A549 cells. However, significant benefits from APS7-GNPs were observed - a stronger reduction in the proliferation of A549 lung cancer cells and a much higher selectivity in cytotoxicity towards cancer cells compared with non-tumorigenic lung epithelial BEAS-2B cells.

Attenuation of Nicotine Effects on A549 Lung Cancer Cells by Synthetic α7 nAChR Antagonists APS7-2 and APS8-2.

Nicotine binds to nicotinic acetylcholine receptors (nAChRs) that are overexpressed in different cancer cells, promoting tumor growth and resistance to chemotherapy. In this study, we aimed to investigate the potential of APS7-2 and APS8-2, synthetic analogs of a marine sponge toxin, to inhibit nicotine-mediated effects on A549 human lung cancer cells. Our electrophysiological measurements confirmed that APS7-2 and APS8-2 act as α7 nAChR antagonists. APS8-2 showed no cytotoxicity in A549 cells, while APS7-2 showed concentration-dependent cytotoxicity in A549 cells. The different cytotoxic responses of APS7-2 and APS8-2 emphasize the importance of the chemical structure in determining their cytotoxicity on cancer cells. Nicotine-mediated effects include increased cell viability and proliferation, elevated intracellular calcium levels, and reduced cisplatin-induced cytotoxicity and reactive oxygen species production (ROS) in A549 cells. These effects of nicotine were effectively attenuated by APS8-2, whereas APS7-2 was less effective. Our results suggest that APS8-2 is a promising new therapeutic agent in the chemotherapy of lung cancer.

Suppressed translation as a mechanism of initiation of CASP8 (caspase 8)-dependent apoptosis in autophagy-deficient NSCLC cells under nutrient limitation.

Macroautophagy/autophagy inhibition under stress conditions is often associated with increased cell death. We found that under nutrient limitation, activation of CASP8/caspase-8 was significantly increased in autophagy-deficient lung cancer cells, which precedes mitochondria outer membrane permeabilization (MOMP), CYCS/cytochrome c release, and activation of CASP9/caspase-9, indicating that under such conditions the activation of CASP8 is a primary event in the initiation of apoptosis as well as essential to reduce clonogenic survival of autophagy-deficient cells. Starvation leads to suppression of CFLAR proteosynthesis and accumulation of CASP8 in SQSTM1 puncta. Overexpression of CFLARs reduces CASP8 activation and apoptosis during starvation, while its silencing promotes efficient activation of CASP8 and apoptosis in autophagy-deficient U1810 lung cancer cells even under nutrient-rich conditions. Similar to starvation, inhibition of protein translation leads to efficient activation of CASP8 and cell death in autophagy-deficient lung cancer cells. Thus, here for the first time we report that suppressed translation leads to activation of CASP8-dependent apoptosis in autophagy-deficient NSCLC cells under conditions of nutrient limitation. Our data suggest that targeting translational machinery can be beneficial for elimination of autophagy-deficient cells via the CASP8-dependent apoptotic pathway.