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Metformin has been a frontline therapy for type 2 diabetes (T2D) for many years. Its effectiveness in T2D treatment is mostly attributed to its suppression of hepatic gluconeogenesis; however, the mechanistic aspects of metformin action remain elusive. In addition to its glucose-lowering effect, metformin possesses other pleiotropic health-promoting effects that include reduced cancer risk and tumorigenesis. Metformin inhibits the electron transport chain (ETC) and ATP synthesis; however, recent data reveal that metformin regulates AMP-activated protein kinase (AMPK) and the mechanistic target of rapamycin complex 1 (mTORC1) by multiple, mutually nonexclusive mechanisms that do not necessarily depend on the inhibition of ETC and the cellular ATP level. In this review, we discuss recent advances in elucidating the molecular mechanisms that are relevant for metformin use in cancer treatment., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Triple negative breast cancer (TNBC) cells express increased levels of the pro-inflammatory and pro-angiogenic chemokine interleukin-8 (IL-8, CXCL8), which promotes their proliferation and migration. Because TNBC patients are unresponsive to current targeted therapies, new therapeutic strategies are urgently needed. While proteasome inhibition by bortezomib (BZ) or carfilzomib (CZ) has been effective in treating hematological malignancies, it has been less effective in solid tumors, including TNBC, but the mechanisms are incompletely understood. Here we report that proteasome inhibition significantly increases expression of IL-8, and its receptors CXCR1 and CXCR2, in TNBC cells. Suppression or neutralization of the BZ-induced IL-8 potentiates the BZ cytotoxic and anti-proliferative effect in TNBC cells. The IL-8 expression induced by proteasome inhibition in TNBC cells is mediated by IκB kinase (IKK), increased nuclear accumulation of p65 NFκB, and by IKK-dependent p65 recruitment to IL-8 promoter. Importantly, inhibition of IKK activity significantly decreases proliferation, migration, and invasion of BZ-treated TNBC cells. These data provide the first evidence demonstrating that proteasome inhibition increases the IL-8 signaling in TNBC cells, and suggesting that IKK inhibitors may increase effectiveness of proteasome inhibitors in treating TNBC., Competing Interests: The authors have declared that no competing interests exist.

The rationale for developing histone deacetylase (HDAC) inhibitors (HDACi) as anticancer agents was based on their ability to induce apoptosis and cell cycle arrest in cancer cells. However, while HDACi have been remarkably effective in the treatment of hematological malignancies, clinical studies with HDACi as single agents in solid cancers have been disappointing. Recent studies have shown that, in addition to inducing apoptosis in cancer cells, class I HDACi induce IκB kinase (IKK)-dependent expression of proinflammatory chemokines, such as interleukin-8 (IL8; CXCL8), resulting in the increased proliferation of tumor cells, and limiting the effectiveness of HDACi in solid tumors. Here, we discuss the mechanisms responsible for HDACi-induced CXCL8 expression, and opportunities for combination therapies targeting HDACs and IKK in solid tumors., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Overexpression of the pro-angiogenic chemokine IL-8 (CXCL8) is associated with a poor prognosis in several solid tumors, including epithelial ovarian cancer (EOC). Even though histone deacetylase (HDAC) inhibition has shown remarkable antitumor activity in hematological malignancies, it has been less effective in solid tumors, including EOC. Here we report results that may explain the decreased efficiency of HDAC inhibition in EOC, based on our data demonstrating that HDAC inhibition specifically induces expression of IL-8/CXCL8 in SKOV3, CAOV3, and OVCAR3 cells. Suppression or neutralization of vorinostat-induced IL-8/CXCL8 potentiates the vorinostat inhibitory effect on cell viability and proliferation. The IL-8/CXCL8 expression induced by vorinostat in EOC cells is dependent on IκB kinase (IKK) activity and associated with a gene-specific recruitment of IKKβ and IKK-dependent recruitment of p65 NFκB to the IL-8/CXCL8 promoter. In addition, HDAC inhibition induces acetylation of p65 and histone H3 and their IL-8/CXCL8 promoter occupancy. In vivo results demonstrate that combining vorinostat and the IKK inhibitor Bay 117085 significantly reduces tumor growth in nude mice compared with control untreated mice or either drug alone. Mice in the combination group had the lowest IL-8/CXCL8 tumor levels and the lowest tumor expression of the murine neutrophil [7/4] antigen, indicating reduced neutrophil infiltration. Together, our results demonstrate that HDAC inhibition specifically induces IL-8/CXCL8 expression in EOC cells and that the mechanism involves IKK, suggesting that using IKK inhibitors may increase the effectiveness of HDAC inhibitors when treating ovarian cancer and other solid tumors characterized by increased IL-8/CXCL8 expression., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)

Bortezomib (BZ) is the first clinically approved proteasome inhibitor that has shown remarkable anticancer activity in patients with hematological malignancies. However, many patients relapse and develop resistance; yet, the molecular mechanisms of BZ resistance are not fully understood. We have recently shown that in solid tumors, BZ unexpectedly increases expression of the pro-inflammatory and pro-angiogenic chemokine interleukin-8 (IL-8), while it inhibits expression of other NFκB-regulated genes. Since monocytes and macrophages are major producers of IL-8, the goal of this study was to test the hypothesis that BZ increases the IL-8 expression in human monocytes and macrophages. Here, we show that BZ dramatically increases the IL-8 expression in lipopolysaccharide (LPS)-stimulated U937 macrophages as well as in unstimulated U937 monocytes and peripheral blood mononuclear cells, while it inhibits expression of IL-6, IL-1 and tumor necrosis factor-α. In addition, our results show that the underlying mechanisms involve p38 mitogen-activated protein kinase, which is required for the BZ-induced IL-8 expression. Together, these data suggest that the BZ-increased IL-8 expression in monocytes and macrophages may represent one of the mechanisms responsible for the BZ resistance and indicate that targeting the p38-mediated IL-8 expression could enhance the BZ effectiveness in cancer treatment., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Interleukin-8 (IL-8), originally discovered as the neutrophil chemoattractant and inducer of leukocyte-mediated inflammation, contributes to cancer progression through its induction of tumor cell proliferation, survival, and migration. IL-8 expression is increased in many types of advanced cancers, including ovarian cancer, and correlates with poor prognosis. Bortezomib (BZ) is the first FDA-approved proteasome inhibitor that has shown remarkable antitumor activity in multiple myeloma and other hematological malignancies. In solid tumors, including ovarian carcinoma, BZ has been less effective as a single agent; however, the mechanisms remain unknown. We have recently shown that in ovarian cancer cells, BZ greatly increases IL-8 expression, while expression of other NFκB-regulated cytokines, IL-6 and TNF, is unchanged. In this chapter, we describe a protocol that uses real-time qRT-PCR to quantitatively analyze mRNA levels of IL-8 and IL-6 in BZ-treated ovarian cancer cells. The protocol can be easily modified and used for analysis of other cytokines in different cell types.

Interleukin-1β (IL-1) and tumor necrosis factor-α (TNF) are important pro-inflammatory cytokines involved in the mediation of the immune response, inflammation, tissue repair, and tumor progression. Regulation of IL-1 and TNF expression is mediated at the level of transcription by the transcription factor NFκB. Inhibition of NFκB activity by the proteasome inhibitor bortezomib (BZ) has been used as a frontline therapy in multiple myeloma and other hematological malignancies. In this chapter, we describe a protocol that uses chromatin immunoprecipitation (ChIP) to analyze the NFκB recruitment to endogenous IL-1 and TNF promoters in BZ-treated human macrophages. Corresponding to the BZ-suppressed mRNA levels of IL-1 and TNF, we show that BZ inhibits p65 NFκB recruitment to IL-1 and TNF promoters. This study specifically uses U937 macrophages, but the protocol could be easily modified to analyze the regulation of NFκB recruitment in other cell types.

Expression of the proinflammatory and proangiogenic chemokine IL-8, which is regulated at the transcriptional level by NF-κB, is constitutively increased in androgen-independent metastatic prostate cancer and correlates with poor prognosis. Inhibition of NF-κB-dependent transcription was used as an anticancer strategy for the development of the first clinically approved 26S proteasome inhibitor, bortezomib (BZ). Even though BZ has shown remarkable antitumor activity in hematological malignancies, it has been less effective in prostate cancer and other solid tumors; however, the mechanisms have not been fully understood. In this article, we report that proteasome inhibition by BZ unexpectedly increases IL-8 expression in androgen-independent prostate cancer PC3 and DU145 cells, whereas expression of other NF-κB-regulated genes is inhibited or unchanged. The BZ-increased IL-8 expression is associated with increased in vitro p65 NF-κB DNA binding activity and p65 recruitment to the endogenous IL-8 promoter. In addition, proteasome inhibition induces a nuclear accumulation of IκB kinase (IKK)α, and inhibition of IKKα enzymatic activity significantly attenuates the BZ-induced p65 recruitment to IL-8 promoter and IL-8 expression, demonstrating that the induced IL-8 expression is mediated, at least partly, by IKKα. Together, these data provide the first evidence, to our knowledge, for the gene-specific increase of IL-8 expression by proteasome inhibition in prostate cancer cells and suggest that targeting both IKKα and the proteasome may increase BZ effectiveness in treatment of androgen-independent prostate cancer.

Objective: Despite advances in the management of sepsis and acute respiratory distress syndrome, the mortality rate remains high. Delayed apoptosis of neutrophils is associated with multiple organ failure under those conditions. Thus, development of nontoxic neutrophil apoptosis regulating molecules may provide a novel therapeutic strategy. Curcumin is a promising dietary supplement for cancer prevention. However, the effect of curcumin on human neutrophil apoptosis remains unknown. We therefore hypothesized that curcumin would produce a proapoptotic effect on neutrophils., Design: Prospective, controlled, and randomized in vitro study., Setting: Research institute laboratory., Subjects: Human peripheral neutrophils obtained from normal subjects., Interventions: None., Measurements and Main Results: In the presence or absence of curcumin, both spontaneous neutrophil apoptosis and apoptosis of neutrophils following transmigration across a human lung endothelium-epithelium bilayer were studied by morphology and terminal dUTP nucleotide end labeling analyses, respectively. Myeloperoxidase activity and migration assays were performed to determine the impact of curcumin on neutrophil function. To elucidate the potential mechanism, the p38 mitogen-activated protein kinase pathway and caspase-3 activity were examined by Western blotting and enzymatic analyses. The data demonstrate that curcumin increased constitutive neutrophil apoptosis and abrogated the transbilayer migration-induced delay in neutrophil apoptosis. Neutrophil activation was reduced by curcumin treatment as evidenced by a decrease in migration and myeloperoxidase release. A marked increase in p38 phosphorylation and caspase-3 activity was observed following curcumin exposure. In addition, inhibition of p38 mitogen-activated protein kinase with SB203580 suppressed apoptosis and caspase-3 activation induced by curcumin. Thus, activation of p38 mitogen-activated protein kinase or an increase in caspase-3 activity appears to contribute to the proapoptotic effect of human neutrophil apoptosis by curcumin., Conclusion: The characteristics of curcumin, including its proapoptotic effect and antidegranulation effect, make it a potential candidate for the therapy of neutrophil-induced lung injury and sepsis.