bms345541 and Melanoma

Monoclonal antibodies against immune checkpoint blockade have proven to be a major success in the treatment of melanoma. The programmed death receptor-1 ligand-1 (PD-L1) expression on melanoma cells is believed to have an inhibitory effect on T cell responses and to be an important escape mechanism from immune attack. Previous studies have shown that PD-L1 can be expressed constitutively or can be induced by IFN-γ secreted by infiltrating lymphocytes. In the present study we have investigated the mechanism underlying these two modes of PD-L1 expression in melanoma cells including cells that had acquired resistance to the BRAF inhibitor vemurafenib. PD-L1 expression was examined by flow cytometry and immunoblotting. Specific inhibitors and siRNA knockdown approaches were used to examine the roles of the RAF/ MEK, PI3K, NF-κB, STAT3 and AP1/ c-Jun pathways. IFN-γ inducible expression of PD-L1 was dependent on NF-κB as shown by inhibition with BMS-345541, an inhibitor of IκB and the BET protein inhibitor I-BET151, as well as by siRNA knockdown of NF-κB subunits. We were unable to implicate the BRAF/MEK pathway as major regulators in PD-L1 expression on vemurafenib resistant cells. Similarly the PI3K/AKT pathway and the transcription factors STAT3 and c-Jun had only minor roles in IFN-γ induced expression of PD-L1. The mechanism underlying constitutive expression remains unresolved. We suggest these results have significance in selection of treatments that can be used in combination with monoclonal antibodies against PD1, to enhance their effectiveness and to reduce inhibitory effects melanoma cells have against cytotoxic T cell activity.

Topics: B7-H1 Antigen; Cell Line, Tumor; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Humans; Imidazoles; Indoles; Interferon-gamma; Melanoma; NF-kappa B; Quinoxalines; Sulfonamides; Time Factors; Vemurafenib

Resistance to TRAIL (TNF-related apoptosis-inducing ligand)- induced apoptosis limits its therapeutic use. Different strategies of TRAIL sensitization and a dependency on Bax have been reported, but common principles of TRAIL resistance and the way of Bax activation remained poorly understood. Applying a melanoma model of TRAIL-sensitive and -resistant cell lines, efficient sensitization for TRAIL-induced apoptosis is demonstrated by the kinase inhibitor BMS-345541 (N-(1,8-dimethylimidazo(1,2-a)quinoxalin-4-yl)-1,2-ethanediamine hydrochloride), which targets IκB (inhibitor of κB proteins) kinase β (IKKβ). This effect was completely abrogated by Bax knockout as well as by Bcl-2 overexpression, in accordance with a Bax dependency. Early loss of the mitochondrial membrane potential, release of cytochrome c and Smac (second mitochondria-derived activator of caspases) clearly indicated the activation of mitochondrial apoptosis pathways. Of note, BMS-345541 alone resulted in an early Bax activation, seen by conformational changes and by Bax translocation. The synergistic effects can be explained by Bid activation through TRAIL, which inhibits Bcl-2, and the activation of Bax through BMS-345541. The critical roles of XIAP (X-chromosome-linked inhibitor of apoptosis protein), Smac and Bid were clearly proven by overexpression and siRNA knockdown, respectively. The way of Bax activation by BMS-345541 was unraveled by establishing new assays for Bax activation. These showed reduction of the inactivating Bax phosphorylation at serine-184, while the activating Bax phosphorylation at threonine-167 was enhanced. Thus, modulation of Bax phosphorylation appeared as tightly related to TRAIL sensitivity/resistance in melanoma cells, and therapeutic strategies may be considered.

Topics: Apoptosis; bcl-2-Associated X Protein; BH3 Interacting Domain Death Agonist Protein; Caspases; Cell Line, Tumor; Humans; I-kappa B Kinase; Imidazoles; Melanoma; Mitochondria; NF-kappa B; Oligopeptides; Phosphorylation; Proto-Oncogene Proteins c-bcl-2; Quinoxalines; Recombinant Proteins; RNA Interference; RNA, Small Interfering; TNF-Related Apoptosis-Inducing Ligand; X-Linked Inhibitor of Apoptosis Protein

The transcription factor NF-κB promotes survival of cancer cells exposed to doxorubicin and other chemotherapeutic agents. IκB kinase is essential for chemotherapy-induced NF-κB activation and considered a prime target for anticancer treatment. An IκB kinase inhibitor sensitized human melanoma xenografts in mice to killing by doxorubicin, yet also exacerbated treatment toxicity in the host animals. Using mouse models that simulate cell-selective targeting, we found that impaired NF-κB activation in melanoma and host myeloid cells accounts for the therapeutic and the adverse effects, respectively. Ablation of tumor-intrinsic NF-κB activity resulted in apoptosis-driven tumor regression following doxorubicin treatment. By contrast, chemotherapy in mice with myeloid-specific loss of NF-κB activation led to a massive intratumoral recruitment of interleukin-1β-producing neutrophils and necrotic tumor lesions, a condition associated with increased host mortality but not accompanied by tumor regression. Therefore, a molecular target-based therapy may be steered toward different clinical outcomes depending on the drug's cell-specific effects.. Our findings show that the IκB kinase–NF-κB signaling pathway is important for both promoting treatment resistance and preventing host toxicity in cancer chemotherapy; however, the two functions are exerted by distinct cell type–specific mechanisms and can therefore be selectively targeted to achieve an improved therapeutic outcome.

Topics: Animals; Apoptosis; Cell Line, Tumor; Doxorubicin; Drug Resistance, Neoplasm; Humans; I-kappa B Kinase; Imidazoles; Interleukin-1beta; Melanoma; Mice; Mice, Inbred C57BL; Myeloid Cells; Neutrophils; NF-kappa B; Protein Kinase Inhibitors; Quinoxalines; Signal Transduction; Xenograft Model Antitumor Assays

Purpose. To examine the involvement of nuclear factor-kappa B (NFkappaB) pathways in uveal melanoma (UM) and to assess their potential as a therapeutic target for metastatic UM. Methods. Samples from primary (n = 7) and metastatic (n = 7) UM were evaluated for NFkappaB transcription factor family expression by quantitative PCR (QPCR), immunofluorescent staining, and Western blot analysis. The effect of two NFkappaB inhibitors, DHMEQ and BMS-345541, on two cell lines derived from UM liver metastases was assessed. Cell proliferation was examined by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, methylene blue assay, and immunostaining for Ki-67. Apoptosis was assessed by immunostaining for activated caspase 3. Results. NFkappaB1, NFkappaB2, RelA, RelB, and NIK were expressed in primary UM and in its liver metastases. NFkappaB2, RelB, and NIK showed significantly higher mRNA levels in metastases from UM compared with primary tumors (3.4-fold, P = 0.03; 3.6-fold, P = 0.05; 3.5-fold, P = 0.03; respectively). NFkappaB2 protein activation was 3.9-fold higher in metastases (P = 0.03). NFkappaB inhibition reduced metastatic cell proliferation by 9.2-fold and 1.9-fold according to Ki67 staining (P = 0.04) and methylene blue assay (P = 6 x 10(-7)), respectively. Both NFkappaB inhibitors achieved dose-dependent reductions of UM cell proliferation in both cell lines (P < 0.001). NFkappaB inhibition resulted in a 6.3-fold increase of apoptosis (P = 7 x 10(-7)). Conclusions. These data indicate that the NFkappaB1 and NFkappaB2 pathways are active in both primary and metastatic UM and that these pathways regulate metastatic cell proliferation and apoptosis. The role of NFkappaB as a therapeutic target for UM should be further evaluated.

Topics: Apoptosis; Benzamides; Blotting, Western; Caspase 3; Cell Proliferation; Cyclohexanones; Fluorescent Antibody Technique, Indirect; Humans; Imidazoles; Ki-67 Antigen; Liver Neoplasms; Melanoma; NF-kappa B; Quinoxalines; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured; Uveal Neoplasms

The BRAFV600E mutation is common in human melanoma. This mutation enhances IkappaB kinase (IKK)/nuclear factor-kappaB (NF-kappaB) and extracellular signal-regulated kinase/activator protein signaling cascades. In this study, we evaluated the efficacy of targeting either B-Raf or IKKbeta in combination with the DNA alkylating agent temozolomide for treatment of advanced metastatic melanoma. Xenografts of Hs294T human metastatic melanoma cells exhibiting the BRAFV600E mutation were treated with inhibitors of IKKbeta (BMS-345541), B-Raf (BAY 54-9085), and/or temozolomide. Drug response was mechanistically analyzed in vitro and in vivo. In this study, we determined that the antitumor activity of all three drugs depends on inhibition of NF-kappaB. BMS-345541 inhibits IKKbeta-mediated phosphorylation of IkappaBalpha and thus blocks the nuclear localization of NF-kappaB, whereas BAY 54-9085 inhibits activation of NF-kappaB through a mechanism that does not involve stabilization of IkappaBalpha. Moreover, BMS-345541, but not BAY 54-9085, activates the death pathways of p53 and c-Jun-NH2-kinase, contributing to the killing of melanoma cells. Temozolomide inhibits both NF-kappaB and extracellular signal-regulated kinase activity, conferring effective in vivo antitumor activity. Thus, temozolomide, but not BAY 54-9085, has a synergistic in vivo antitumor effect with BMS-345541. We conclude that the efficacy of antimelanoma therapy depends on inhibition of expression of antiapoptotic genes transcriptionally regulated by NF-kappaB. In contrast, drug targeting of the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway alone in melanoma cells is ineffective for melanoma therapy in cases where NF-kappaB is not also targeted.

Topics: Animals; Antineoplastic Agents; Benzenesulfonates; Biomarkers, Tumor; Dacarbazine; Drug Delivery Systems; Drug Synergism; Female; Gene Expression Regulation, Neoplastic; Humans; Imidazoles; Melanoma; Mice; Mice, Inbred BALB C; Mice, Nude; Models, Biological; Niacinamide; Phenylurea Compounds; Pyridines; Quinoxalines; Skin Neoplasms; Sorafenib; Substrate Specificity; Temozolomide; Treatment Outcome; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Constitutive activation of inhibitor of kappaB kinase (IKK) confers melanoma resistance to apoptosis and chemotherapy. Whether IKK is able to serve as a therapeutic target in melanoma is unknown. We explored the possibility of exploiting IKK as a therapeutic target in melanoma by using BMS-345541, a novel compound with a highly selective IKKbeta inhibitory activity, to trigger melanoma cell apoptosis.. Three human melanoma cell lines (SK-MEL-5, Hs 294T, and A375), all of which have high constitutive IKK activities, served as in vitro and in vivo melanoma models for treatment with BMS-345541. Two known antitumor drugs (temozolomide and bortezomib) were used as parallel controls for evaluation of the therapeutic efficiency and toxicity of BMS-345541. The effects of BMS-345541 on nuclear factor kappaB (NF-kappaB) signaling and on the apoptosis machinery were investigated.. Inhibition of constitutive IKK activity by BMS-345541 resulted in the reduction of NF-kappaB activity, CXCL1 chemokine secretion by cultured melanoma cells and melanoma cell survival in vitro and in vivo. The effect of BMS-345541 on tumor cell growth was through mitochondria-mediated apoptosis, based on the release of apoptosis-inducing factor, dissipation of mitochondrial membrane potential, and reduced ratio of B cell lymphoma gene-2 (Bcl-2)/Bcl-associated X protein (Bax) in mitochondria. The BMS-345541 execution of apoptosis was apoptosis-inducing factor-dependent, but largely caspase-independent.. BMS-345541 down-regulation of IKK activity results in mitochondria-mediated apoptosis of tumor cells because the programmed cell death machinery in melanoma cells is highly regulated by NF-kappaB signaling. Therefore, IKK may serve as a potential target for melanoma therapy.

Topics: Animals; Apoptosis; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Humans; I-kappa B Kinase; Imidazoles; In Vitro Techniques; Melanoma; Mice; Mitochondria; NF-kappa B; Quinoxalines; Signal Transduction; Structure-Activity Relationship; Time Factors; Tumor Cells, Cultured