The use of the dietary polyphenols as chemosensitizing agents to enhance the efficacy of conventional cytostatic drugs has recently gained the attention of scientists and clinicians as a plausible approach for overcoming the limitations of chemotherapy (e.g. drug resistance and cytotoxicity). The aim of this study was to investigate whether a naturally occurring diet-based flavonoid, fisetin, at physiologically attainable concentrations, could act synergistically with clinically achievable doses of paclitaxel to produce growth inhibitory and/or pro-death effects on A549 non-small cell lung cancer cells, and if it does, what mechanisms might be involved. The drug–drug interactions were analyzed based on the combination index method of Chou and Talalay and the data from MTT assays. To provide some insights into the mechanism underlying the synergistic action of fisetin and paclitaxel, selected morphological, biochemical and molecular parameters were examined, including the morphology of cell nuclei and mitotic spindles, the pattern of LC3-II immunostaining, the formation of autophagic vacuoles at the electron and fluorescence microscopic level, the disruption of cell membrane asymmetry/integrity, cell cycle progression and the expression level of LC3-II, Bax, Bcl-2 and caspase-3 mRNA. Here, we reported the first experimental evidence for the existence of synergism between fisetin and paclitaxel in the in vitro model of non-small cell lung cancer. This synergism was, at least partially, ascribed to the induction of mitotic catastrophe. The switch from the cytoprotective autophagy to the autophagic cell death was also implicated in the mechanism of the synergistic action of fisetin and paclitaxel in the A549 cells. In addition, we revealed that the synergism between fisetin and paclitaxel was cell line-specific as well as that fisetin synergizes with arsenic trioxide, but not with mitoxantrone and methotrexate in the A549 cells. Our results provide rationale for further testing of fisetin in the combination with paclitaxel or arsenic trioxide to obtain detailed insights into the mechanism of their synergistic action as well as to evaluate their toxicity towards normal cells in an animal model in vivo. We conclude that this study is potentially interesting for the development of novel chemotherapeutic approach to non-small cell lung cancer.

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The identification and development of new agents with a therapeutic potential as well as novel drug combinations are gaining the attention of scientists and clinicians as a plausible approach to improve therapeutic regimens for chemoresistant tumors. We have recently reported that the flavonoid fisetin (FIS), at physiologically attainable concentrations, acts synergistically with clinically achievable doses of paclitaxel (PTX) to produce growth inhibitory and pro-death effects on A549 human non-small cell lung cancer (NSCLC) cells. To further investigate a potential therapeutic efficacy of the combination of fisetin with paclitaxel, we decided to assess its impact on metastatic capability of A549 cells as well as its toxicity toward normal human lung fibroblast. Cell viability, cell migration, and invasion were measured by thiazolyl blue tetrazolium bromide (MTT) assay, wound healing assay, and Transwell chamber assay, respectively. The expression of metastasis-related genes was assessed with quantitative reverse transcriptase real-time polymerase chain reaction (qRT-PCR). Actin and vimentin filaments were examined under the fluorescence microscope. The combination of FIS and PTX significantly reduced cancer cell migration and invasion, at least partially, through a marked rearrangement of actin and vimentin cytoskeleton and the modulation of metastasis-related genes. Most of these effects of the combination treatment were significantly greater than those of individual agents. Paclitaxel alone was even more toxic to normal cells than the combination of this drug with the flavonoid, suggesting that FIS may provide some protection against PTX-mediated cytotoxicity. The combination of FIS and PTX is expected to have a synergistic anticancer efficacy and a significant potential for the treatment of NSCLC, however, further in vitro and in vivo studies are required to confirm this preliminary evidence.

The existence, the functional role and clinical relevance of GDF15 and its signaling through a GFRAL/RET-dependent complex in gastric cancer (GC) and other human tumors remain to be elucidated, despite the widespread recognition of obesity as an important cancer-predisposing factor. Therefore, we aimed to analyze the expression levels of GDF15, GFRAL and RET in GC tissues in relation to each other and clinicopathological features, including patient survival, in order to establish a potential implication of the body-weight signaling pathway in the pathology and clinical outcome of GC. Protein expression was examined by immunohistochemistry on tissue microarrays containing 104 and 30 consecutive GC and normal gastric mucosa samples, whereas gene expression data for The Cancer Genome Atlas cohort of 413 GC patients were obtained from public sources. We found that the protein expression of GDF15, GFRAL and RET was significantly elevated and positively correlated in our set of GC tissues, which was reflected in their tendency to be overexpressed in low-grade and intermediate-grade tumors rather than high-grade ones. No other relationships between the expression status of the examined proteins and clinicopathological characteristics of GC patients were found. Through in silico data analysis, we showed that high GDF15 expression was associated with better overall survival (OS) of GC patients, whereas the opposite was true for high levels of GFRAL or RET. Specifically, GFRAL and RET emerged as independent prognostic factors associated with poor OS. Furthermore, high combined expression of the three markers: GDF15+GFRAL+RET was significantly associated with reduced OS, and it was an independent prognostic factor of borderline significance in terms of OS, when adjusted for covariates. If validated in large-scale studies, the individual and combined expression of GDF15, GFRAL and RET may provide significant clinical implications for the prognosis prediction of GC patients.