miR-4487 Enhances Gefitinib-Mediated Ubiquitination and Autophagic Degradation of EGFR in Non-Small Cell Lung Cancer Cells by Targeting USP37 / Journal of the Korean Cancer Association, 대한암학회지

Purpose@#With the identification of epidermal growth factor receptor (EGFR) mutations in non–small cell lung cancer (NSCLC) cells, EGFR–tyrosine kinase inhibitors (TKIs) are being used widely as the first-line of treatment in NSCLC. These inhibitors block auto-phosphorylation of activated EGFR by competing with ATP binding and mediate EGFR degradation independent of exogenous epidermal growth factor, which is associated with the mutation variants of EGFR. However, the precise mechanisms underlying the TKI-mediated EGFR degradation are still unclear. @*Materials and Methods@#To examine the physiological roles of miR-4487 and ubiquitin-specific peptidase 37 (USP37) in gefitinib-mediated EGFR degradation in NSCLC cells, multiple NSCLC cell lines were applied. The level of EGFR expression, apoptosis marker and autophagic flux were determined by western blot. Expression level of miR-4487 and cell cycle arrest was analyzed by TaqMan assay and flow cytometry respectively. @*Results@#We found that gefitinib mediates EGFR degradation under normal culture conditions, and is dependent on autophagic flux and the mutation variants of EGFR. Gefitinib reduced expression levels of USP37, which mediated EGFR degradation similar to gefitinib. Our results also showed a gefitinib-mediated increase in endogenous miR-4487 level and presented evidence for the direct targeting of USP37 by miR-4487, resulting in the sequential enhancement of ubiquitination, autophagy, and EGFR degradation. Thus, the depletion of USP37 and overexpression of miR-4487 led to an increase in gefitinib-mediated apoptotic cell death. @*Conclusion@#These data suggest that miR-4487 is a potential target for treating NSCLC, and miR-4487/USP37-regulated EGFR degradation is a determinant for developing gefitinib resistance.

Short-chain fatty acids, including acetate, propionate, and butyrate, elicit differential regulation of intracellular Ca2+ mobilization, expression of IL-6 and IL-8, and cell viability in gingival fibroblast cells

Short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate are secondary metabolites produced by anaerobic fermentation of dietary fibers in the intestine. Intestinal SCFAs exert various beneficial effects on intestinal homeostasis, including energy metabolism, autophagy, cell proliferation, immune reaction, and inflammation, whereas contradictory roles of SCFAs in the oral cavity have been reported. Herein, we found that low and high concentrations of SCFAs induce differential regulation of intracellular Ca2+ mobilization and expression of pro-inflammatory cytokines, such as interleukin (IL)-6 and IL-8, respectively, in gingival fibroblast cells. Additionally, cell viability was found to be differentially regulated in response to low and high concentrations of SCFAs. These findings demonstrate that the physiological functions of SCFAs in various cellular responses are more likely dependent on their local concentration.