ver-155008 and Inflammation

TNFα is a pleiotropic cytokine which fuels tumor cell growth, invasion, and metastasis in some malignancies, while in others it induces cytotoxic cell death. However, the molecular mechanism by which TNFα exerts its diverse effects on breast cancer subtypes remains elusive. Using in vitro assays and mouse xenografts, we show here that TNFα contributes to the aggressive properties of triple negative breast cancer (TNBC) cell lines via upregulation of TNFAIP3(A20). In a striking contrast, TNFα induces a potent cytotoxic cell death in luminal (ER+) breast cancer cell lines which fail to upregulate A20 expression. Overexpression of A20 not only protects luminal breast cancer cell lines from TNFα-induced cell death via inducing HSP70-mediated anti-apoptotic pathway but also promotes a robust EMT/CSC phenotype by activating the pStat3-mediated inflammatory signaling. Furthermore, A20 overexpression in luminal breast cancer cells induces aggressive metastatic properties in mouse xenografts via generating a permissive inflammatory microenvironment constituted by granulocytic-MDSCs. Collectively, our results reveal a mechanism by which A20 mediates pleiotropic effects of TNFα playing role in aggressive behaviors of TNBC subtype while its deficiency results in TNFα-induced apoptotic cell death in luminal breast cancer subtype.

Topics: Animals; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Epithelial-Mesenchymal Transition; Female; Gene Expression Regulation, Neoplastic; Genetic Pleiotropy; Heterografts; HSP72 Heat-Shock Proteins; Humans; Inflammation; Lung Neoplasms; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Invasiveness; Neoplasm Proteins; Neoplastic Stem Cells; Purine Nucleosides; Recombinant Fusion Proteins; RNA, Neoplasm; Signal Transduction; STAT3 Transcription Factor; Triple Negative Breast Neoplasms; Tumor Necrosis Factor alpha-Induced Protein 3; Tumor Necrosis Factor-alpha

The unfolded protein response (UPR) is a cascade of events that helps restoring cellular homeostasis under stressful conditions. It is activated when there is an imbalance in the protein load and protein folding capacity of the endoplasmic reticulum (ER) as a result of an increase in the naïve, unfolded, or misfolded protein content of the cell. Dengue virus (DENV) utilizes the host machinery to synthesize viral proteins and replicates in the cell. During DENV infection, up-regulation of viral proteins increases the protein pool of the cell, resulting in the induction of UPR pathway. In this study, we have tried to understand the consequence of UPR induction during DENV infection in human monocytic cells. To fulfill this objective, we have used VER-155008 (VER), a known inhibitor of the 78 kDa glucose-regulated protein (GRP78), which is the master regulator of the UPR pathway. After VER treatment, cells were infected with DENV, and the induction of the UPR elements and their downstream activation was studied by western blotting and RT-PCR analysis. Interestingly, inhibition of GRP78 via VER treatment led to the decreased expression of DENV envelope protein through the activation of the UPR elements, protein kinase-like ER resident kinase, activating transcription factor 6, and inositol-requiring enzyme 1 (IRE1), and then led to the activation of innate immune factors such as double-stranded RNA-activated protein kinase (PKR), interferon regulated factor 3 (IRF3), nuclear factor-κB (NF-κB) and interleukin 1β (IL-1β). This strategy may be used to decrease viral infection transiently. Thus UPR elements could be important therapeutic targets for decreasing DENV multiplication.

Topics: Activating Transcription Factor 6; Animals; Cell Line; Cytokines; Dengue; Dengue Virus; Dose-Response Relationship, Drug; Endoplasmic Reticulum; Endoplasmic Reticulum Chaperone BiP; Endoribonucleases; Enzyme-Linked Immunosorbent Assay; Heat-Shock Proteins; Humans; Immunity, Innate; Inflammation; Insecta; Monocytes; NF-kappa B; Protein Denaturation; Protein Serine-Threonine Kinases; Purine Nucleosides; Unfolded Protein Response