Amongst all types of cancers, breast cancer is recognized as the most common cancer and a principal cause of morbidity and mortality in women. Endoplasmic reticulum (ER) stress pathways are primarily activated in cancer cells and activate a signaling network called the unfolded protein response (UPR). Many tumors, by activating the UPR pathway, allow to adapt and grow under stressful conditions. UPR is usually inactive in non-tumor cells, while it is active in tumor cells, so it is appropriate to develop new breast cancer therapies. A protein that regulates UPR is 78 KDa Glucose-Regulated Protein (GRP78). Usually, the GRP78 level in the cell is relatively low but increases significantly under stresses that affect the ER and calcium homeostasis, and increases resistance to chemotherapy. GRP78 drug suppressors could provide promising anticancer therapeutics. Therefore, understanding the molecular mechanism of GRP78 in cancer and identifying drugs that target GRP78 is essential for the treatment of breast cancer. In this review, we investigate the role of GRP78 in the pathogenesis of breast cancer.

Background and objectives: Quercetin is a naturally occurring phenolic compound abundantly present in plants as a secondary metabolite. The purpose of this study was to investigate the effect of quercetin on improving RINm5F β-insulinemia cell viability, glucose-stimulated insulin secretion (GSIS), and cell insulin content in the presence or absence of streptozotocin (STZ). Methods: This experimental study was conducted on RINm5F β-insulinemia cell line. The cell viability was evaluated by MTT assay. The necrosis was confirmed by flowcytometry and insulin ELISA kit was used to measure the GSIS level and cell insulin content. It should be noted that for testing of cells by 50μM of quercetin, simultaneous treatment and pre-treatment of quercetin were performed in the presence of STZ (20mM). Results: The quercetin was able to improve the viability of RINm5F cells in the presence of STZ and to increase the GSIS level and cell insulin content under STZ and glucotoxic conditions Conclusion: The quercetin seems to have beneficial effects on β-cells, especially the synthesis and secretion of insulin. In addition to the therapeutic effect, given the low toxicity of this flavonoid and the results of this study, the quercetin as a preventive agent may play an important role in maintaining the health of β-cells in people at risk of diabetes.