Triple negative breast cancers (TNBC) are among the most aggressive and therapy-resistant breast tumors and currently possess almost no molecular targets for therapeutic options in this horizon. raises the possibility for the use of nifetepimine as a potent anti-cancer agent with strong immune-restoring properties for therapeutic intervention for this group of cancer bearers. elevated expression of GRP78 has been reported in several cancers, such as breast cancer and prostate cancer) (12,C15). Moreover, GRP78 expression has been shown in some cases to be associated with tumor development and growth and correlated with resistance to certain forms of chemotherapy. It seems that some cancer cells may have adapted to ER stress by activation of the UPR without resulting in apoptosis (13, 14, 16). As a master regulator of the UPR, GRP78 is believed to play an essential role in counteracting the apoptosis inducing potential of ER stress by multiple mechanisms such as binding Oxybenzone to the unfolded proteins to alleviate ER stress conditions, and binding to calcium to prevent its release from the ER (12). Reports suggest that human caspase-4 plays an important role in ER stress-induced apoptosis of human neuroblastoma and HeLa cells (17). Caspase-4 have been reported to be physically associated with GRP78 and down-regulation of GRP78 plays a role in facilitating the activation of caspase-4 and apoptosis (18). The GRP promoters contain multiple copies of ER stress response elements. It has been previously observed that a protein complex exhibits enhanced binding to the ER stress response element of the GRP78 promoter on thapsigargin-induced stress (19, 20). Later this protein binding within the ER stress response element SPP1 has been identified as the multitranscription factor TFII-I (21). TFII-I plays a significant role in signal transduction. TFII-I is phosphorylated at serine/threonine and tyrosine residues, and its activity is regulated by phosphorylation (22). It has also been acknowledged that ERK phosphorylates TFII-I at serines 627 and 633 and thereby regulates its promoter binding activity (23). Hence it can be suggested that the ERK pathway may participate in regulation of GRP78 transcription. Activation of the MEK/ERK pathway is a common cause for resistance of cells to apoptosis mediated by the death receptor and mitochondrial apoptotic pathways (24, 25). In this regard, we examined the potential interaction between the UPR and MEK/ERK pathway in regulation of sensitivity of breast carcinoma cells to ER stress-induced apoptosis. Thus regulation of the MEK/ERK pathway by any therapeutic agent may effectively interfere with GRP78 gene transcription, which might be effective in inducing apoptosis in breast cancer cells. On the basis of the above discussion, which highlights the importance of the cross-talk between ER stress and the MEK/ERK pathway in induction of cancer cell apoptosis, our present Oxybenzone work was focused on exploring the possibility of inducing apoptosis in TNBC cells by targeting ER stress and MEK/ERK pathways with a synthetic dihydropyrimidone, nifetepimine. Our laboratory has previously identified nifetepimine as a potential immune-restoring agent in tumor bearers (26). Here we have explored the role of nifetepimine in inducing apoptosis in TNBC cells in both and models. Underlying molecular mechanisms revealed that nifetepimine regulates GRP78 gene transcription by down-regulating phospho-ERK expression in TNBC cells and thereby induces significant apoptosis in breast cancer cells mice models. Our study thus reports for the first time an intricate mechanism of nifetepimine-mediated cancer regression in triple negative breast cancer cells and also suggests the role of nifetepimine as a possible therapeutic agent with a strong immunmodulatory and anti-carcinogenic effect, which can be used to treat patients with cancer. EXPERIMENTAL PROCEDURES Cell Lines and Mice The human mammary epithelial carcinoma cells (MDAMB-231 and MDAMB-468; maintained in complete DMEM) were obtained from NCCS, India. Male Swiss albino mice were obtained from Chittaranjan National Cancer Research Institute, Kolkata, India. The SCID mice experiments were performed in NCCS, Pune. All ethical guidelines of the animal ethics committee of the Institute for handling and performing of the experiments were followed. Oxybenzone Synthesis and Usage of Nifetepimine Nifetepimine has been synthesized using 3-nitrobenzaldehyde, ethyl acetoacetate, and urea as described (26). For studies, 50 m nifetepimine was used and for studies, 10 mg/kg body.