https://www.selleckchem.com/Proteasome.html Quercetin is a natural product that has been shown to induce tumor apoptosis and necrosis through multiple mechanisms. Tumor-induced myeloid-derived suppressor cell (MDSC) expansion negatively regulates the immune response by inhibiting T cell function through signal transducer and activator of transcription 3 (STAT3) activation, thereby facilitating tumor escape from host immune surveillance. Thus MDSC is an attractive target for cancer immunotherapy to enhance cytotoxic T cell responses. However, the effects of quercetin on MDSC are poorly understood. Here, we demonstrate that quercetin treatment enhanced mouse- and human- derived granulocytic-myeloid-derived suppressor cells (G-MDSC) survival and promoted the secretion of T cell-suppressive factors in vitro. Bioinformatics analysis further showed that quercetin was highly correlated with the estrogen receptor signaling pathway, which was confirmed by quantitative reverse transcription-polymerase chain reaction and flow cytometric analysis. These findings highlight the potential advantages and feasibility of quercetin in reinforcing the suppressive property of G-MDSC. Thus impact of G-MDSC should be taken into consideration when quercetin is applied to tumor therapy. Cisplatin (DDP) is the first-line drug for the treatment of gastric cancer (GC). However, DDP resistance is common. Autophagy, which is closely related to chemoresistance, is a process of resolving and recycling proteins and damaged cellular organs. Additionally, O-6-methylguanine-DNA methyltransferase (MGMT) is responsible for alkylating drug resistance. However, the relationship between autophagy and MGMT in response to DDP in GC is still unknown. In the present study, we determined that autophagy induced by DDP decreases chemosensitivity in GC cell lines. DDP may have induced autophagy in GC by inhibiting MGMT to increase autophagy-related gene (ATG) 4B. Inhibition of MGMT-mediated ATG4B suppression resul