nitrophenols and Melanoma

Cisplatin has been extensively used in therapeutics for its broad-spectrum anticancer activity and frequently used for the treatment of solid tumors. However, it presents several side-effects and several cancers develop resistance. Combination therapy of cisplatin with poly (ADP-ribose) polymerase 1 (PARP1) inhibitors has been effective in increasing its efficacy at lower doses.. In this work, we have shown that the nitro-flavone derivative, 2-(4-Nitrophenyl)-4H-chromen-4-one (4NCO), can improve the sensitivity of cancer cells to cisplatin through inhibition of PARP1. The effect of 4NCO on cisplatin toxicity was studied through combination therapy in both exponential and density inhibited A375 melanoma cells. Combination index (CI) was determined from isobologram analysis. The mechanism of cell killing was assessed by lactate dehydrogenase (LDH) assay. Temporal nicotinamide adenine dinucleotide (NAD. The synthetic nitro-flavone derivative 4NCO effectively inhibited the important nuclear DNA repair enzyme PARP1 and therefore, could complement the DNA-damaging anticancer drug cisplatin in A375 cells and thus, could act as a potential adjuvant to cisplatin in melanoma therapy.

Topics: Antineoplastic Agents; Apoptosis; Cell Line; Cisplatin; Coumarins; DNA Repair; Flavones; Humans; Melanoma; Nitrophenols; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases

Topics: Animals; Biphenyl Compounds; Cell Line, Tumor; Cell Survival; Down-Regulation; Drug Resistance, Neoplasm; Drug Synergism; Enzyme Inhibitors; Female; Humans; Lysophospholipids; Melanoma; Mice; Nitrophenols; Phosphotransferases (Alcohol Group Acceptor); Piperazines; Proto-Oncogene Proteins B-raf; Receptors, Lysosphingolipid; Sphingolipids; Sphingosine; Sphingosine-1-Phosphate Receptors; Sulfonamides; Vemurafenib; Xenograft Model Antitumor Assays

Malignant melanoma is an important type of cancer worldwide due to its aggressiveness and poor survival rate. Significant efforts to understand the biology of melanoma and approaches to treat the advanced disease are focused on targeted gene inhibitors. Frequently mutated genes, such as NRAS, B-RAF and TP53, significantly exceed the frequency of mutations of other genes, emphasizing their importance for future targeted therapies. Considering the antitumor activity of benzothiazolic derivatives, this study aimed to demonstrate the action of benzothiazolic (E)-2-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)-4-nitrophenol (AFN01) against three established human melanoma cell lines that recapitulate the molecular landscape of the disease in terms of its genetic alterations and mutations, such as the TP53, NRAS and B-RAF genes. The results presented here indicate that AFN01, as a significant cytostatic and cytotoxic drug due to its induction of DNA fragmentation, causes single and double DNA strand breaks, consequently inhibiting cell proliferation, migration and invasion by promoting apoptosis. Our data suggest that AFN01 might be considered as a future therapeutic option for managing melanoma.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cell Movement; Cell Survival; DNA Fragmentation; GTP Phosphohydrolases; Humans; Hydrazones; Melanoma; Membrane Proteins; Nitrophenols; Proto-Oncogene Proteins B-raf; Thiazoles; Tumor Suppressor Protein p53; Wound Healing

MCL-1 (BCL-2 family anti-apoptotic protein) is responsible for melanoma's resistance to therapy. Cancer initiating cells also contribute to resistance and relapse from treatments. Here we examined the effects of the MCL-1 inhibitor SC-2001 in killing non melanoma-initiating-cells (bulk of melanoma), and melanoma-initiating-cells (MICs). By itself, SC-2001 significantly kills melanoma cells under monolayer conditions in vitro and in a conventional mouse xenograft model. However, even at high doses (10μM), SC-2001 does not effectively eliminate MICs. In contrast, the combination of SC-2001 with ABT-737 (a BCL-2/BCL-XL/BCL-W inhibitor) significantly decreases ALDH+ cells, disrupts primary spheres, and inhibits the self-renewability of MICs. These results were observed in multiple melanomas, including short term cultures of relapsed tumors from current treatments, independent of the mutation status of BRAF or NRAS. Using a low-cell-number mouse xenograft model, we examined the effects of these treatments on the tumor initiating ability of MIC-enriched cultures. The combination therapy reduces tumor formation significantly compared to either drug alone. Mechanistic studies using shRNA and the CRISPR-Cas9 technology demonstrated that the upregulation of pro-apoptotic proteins NOXA and BIM contribute to the combination-induced cell death. These results indicate that the MCL-1 inhibitor SC-2001 combined with ABT-737 is a promising treatment strategy for targeting melanoma.

Topics: Animals; Antineoplastic Agents; Bcl-2-Like Protein 11; Biphenyl Compounds; Cell Line, Tumor; Cell Self Renewal; Cell Survival; Disease Models, Animal; Drug Synergism; Female; Gene Knockout Techniques; Humans; Melanocytes; Melanoma; Mice; Mutation; Myeloid Cell Leukemia Sequence 1 Protein; Neoplastic Stem Cells; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Sulfonamides; Xenograft Model Antitumor Assays

Major limitations of current melanoma treatments are for instances of relapse and the lack of therapeutic options for BRAF wild-type patients who do not respond to immunotherapy. Many studies therefore focus on killing resistant subpopulations, such as Melanoma Initiating Cells (MICs) to prevent relapse. Here we examined whether combining a GSI (γ-Secretase Inhibitor) with ABT-737 (a small molecule BCL-2/BCL-XL/BCL-W inhibitor) can kill both the non-MICs (bulk of melanoma) and MICs. To address the limitations of melanoma therapies, we included multiple tumor samples of patients relapsed from current treatments, with a diverse genetic background (with or without the common BRAF, NRAS or NF1 mutations) in these studies. Excitingly, the combination treatment reduced cell viability and induced apoptosis of the non-MICs; disrupted primary spheres, decreased the ALDH+ cells, and inhibited the self-renewability of the MICs in multiple melanoma cell lines and relapsed patient samples. Using a low-cell-number mouse xenograft model, we demonstrated that the combination significantly reduced the tumor initiating ability of MIC-enriched cultures from relapsed patient samples. Mechanistic studies also indicate that cell death is NOXA-dependent. In summary, this combination may be a promising strategy to address treatment relapse and for triple wild-type patients who do not respond to immunotherapy.

Topics: Amyloid Precursor Protein Secretases; Animals; Apoptosis; Biphenyl Compounds; Cell Line, Tumor; Cell Self Renewal; Drug Resistance, Neoplasm; Drug Synergism; Drug Therapy, Combination; Female; GTP Phosphohydrolases; Humans; Melanoma; Membrane Proteins; Mice; Mice, Nude; Mutation; Neoplasm Recurrence, Local; Neoplastic Stem Cells; Neurofibromin 1; Nitrophenols; Oligopeptides; Piperazines; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-bcl-2; Sulfonamides; Xenograft Model Antitumor Assays

In theory, pharmacological inhibition of oncogenic signaling is an effective strategy to halt cellular proliferation, induce apoptosis and eliminate cancer cells. In practice, drugs (for example, PLX-4032) that inhibit oncogenes like B-RAFV600E provide relatively short-term success in patients, owing to a combination of incomplete cellular responses and the development of resistance. To define the relationship between PLX-4032-induced responses and resistance, we interrogated the contributions of anti-apoptotic BCL-2 proteins in determining the fate of B-RAFV600E-inhibited melanoma cells. Although PLX-4032 eliminated B-RAFV600E signaling leading to marked cell cycle arrest, only a fraction of cells eventually underwent apoptosis. These data proposed two hypotheses regarding B-RAFV600E inhibition: (1) only a few cells generate a pro-apoptotic signal, or (2) all the cells generate a pro-apoptotic signal but the majority silences this pathway to ensure survival. Indeed, the latter hypothesis is supported by our observations as the addition of ABT-737, an inhibitor to anti-apoptotic BCL-2 proteins, revealed massive apoptosis following PLX-4032 exposure. B-RAFV600E inhibition alone sensitized cells to the mitochondrial pathway of apoptosis characterized by the rapid accumulation of BIM on the outer mitochondrial membrane, which could be functionally revealed by ABT-737 to promote apoptosis and loss of clonogenic survival. Furthermore, PLX-4032-resistant cells demonstrated collateral resistance to conventional chemotherapy, yet could be re-sensitized to PLX-4032 by BCL-2 family inhibition in vivo and conventional chemotherapies in vitro. Our data suggest that inhibiting anti-apoptotic BCL-2 proteins will enhance primary responses to PLX-4032, along with reducing the development of resistance to both targeted and conventional therapies.

Topics: Amino Acid Substitution; Apoptosis; Biphenyl Compounds; Cell Line, Tumor; Drug Resistance, Neoplasm; Humans; Indoles; Melanoma; Mutation, Missense; Nitrophenols; Piperazines; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-bcl-2; Sulfonamides; Vemurafenib

Investigations from multiple laboratories support the existence of melanoma initiating cells (MICs) that potentially contribute to melanoma's drug resistance. ABT-737, a small molecule BCL-2/BCL-XL/BCL-W inhibitor, is promising in cancer treatments, but not very effective against melanoma, with the antiapoptotic protein MCL-1 as the main contributor to resistance. The synthetic retinoid fenretinide N-(4-hydroxyphenyl)retinamide (4-HPR) has shown promise for treating breast cancers. Here, we tested whether the combination of ABT-737 with 4-HPR is effective in killing both the bulk of melanoma cells and MICs. The combination synergistically decreased cell viability and caused cell death in multiple melanoma cells lines (carrying either BRAF or NRAS mutations) but not in normal melanocytes. The combination increased the NOXA expression and caspase-dependent MCL-1 degradation. Knocking down NOXA protected cells from combination-induced apoptosis, implicating the role of NOXA in the drug synergy. The combination treatment also disrupted primary spheres (a functional assay for MICs) and decreased the percentage of aldehyde dehydrogenase (high) cells (a marker of MICs) in melanoma cell lines. Moreover, the combination inhibited the self-renewal capacity of MICs, measured by secondary sphere-forming assays. In vivo, the combination inhibited tumor growth. Thus, this combination is a promising treatment strategy for melanoma, regardless of mutation status of BRAF or NRAS.

Topics: Aldehyde Dehydrogenase; Antineoplastic Agents; Apoptosis; Biomarkers, Tumor; Biphenyl Compounds; Cell Line, Tumor; Cell Survival; Drug Synergism; Drug Therapy, Combination; Fenretinide; Humans; Melanoma; Neoplastic Stem Cells; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Retinoids; Skin Neoplasms; Sulfonamides

Malignant melanoma is refractory to various chemotherapeutics including antitubulin agents such as paclitaxel. Previous studies have suggested a link between βIII-tubulin overexpression and paclitaxel resistance through alterations in the properties of the mitotic spindle. We found that paclitaxel treatment induced temporary mitotic arrest in 7 melanoma cell lines irrespective of the βIII-tubulin level, suggesting that βIII-tubulin had no significant influence on spindle properties. On the other hand, the amount of BCL2, an anti-apoptotic protein, was well correlated with paclitaxel resistance. Treatment of the paclitaxel-resistant cell lines with ABT-737, an inhibitor of BCL2 and BCLxL, or simultaneous knock-down of BCL2 and BCLxL dramatically increased the cells' sensitivity, while knock-down of MCL1, another member of the BCL2 family, had only a minimal effect. Our results suggest that the paclitaxel sensitivity of melanoma cells is attributable to apoptosis susceptibility rather than a change in spindle properties and that BCL2 and BCLxL play a pivotal role in the former.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; bcl-X Protein; Biphenyl Compounds; Caspase 9; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Flow Cytometry; Humans; Melanoma; Nitrophenols; Paclitaxel; Piperazines; Poly(ADP-ribose) Polymerases; Proto-Oncogene Proteins c-bcl-2; RNA, Small Interfering; Spindle Apparatus; Sulfonamides; Tubulin

Anti-apoptotic Bcl-2 family proteins, in particular, Mcl-1, are known to play a critical role in resistance of human melanoma cells to induction of apoptosis by endoplasmic reticulum stress and other agents. The present study examined whether the BH3 mimetics, Obatoclax and ABT-737, which inhibit multiple anti-apoptotic Bcl-2 family proteins, would overcome resistance to apoptosis. We report that both agents induced a strong unfolded protein response (UPR) and that RNAi knockdown of UPR signalling proteins ATF6, IRE1α and XBP-1 inhibited Mcl-1 upregulation and increased sensitivity to the agents. These results demonstrate that inhibition of anti-apoptotic Bcl-2 proteins by Obatoclax and ABT-737 appears to elicit a protective feedback response in melanoma cells, by upregulation of Mcl-1 via induction of the UPR. We also report that Obatoclax, but not ABT-737, strongly induces autophagy, which appears to play a role in determining melanoma sensitivity to the agents.

Topics: Antineoplastic Agents; Apoptosis; Autophagy; Biphenyl Compounds; Calcium; Cell Line, Tumor; Cytosol; Drug Resistance, Neoplasm; Endoplasmic Reticulum Stress; Humans; Indoles; Melanoma; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Sulfonamides; Unfolded Protein Response; Up-Regulation

Although the introduction of selective v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) inhibitors has been a major advance in treatment of metastatic melanoma, approximately 50% of patients have limited responses including stabilization of disease or no response at all. This study aims to identify a novel means of overcoming resistance of melanoma to killing by BRAF inhibitors. We examined the influence of the BH3-mimetic ABT-737 on induction of apoptosis by the selective BRAF inhibitor PLX4720 in melanoma cells with or without BRAF V600E mutation. Included were cell lines established from four patients before and during treatment with selective BRAF inhibitors and 3D spheroids derived from these cell lines. Cell lines with no or low sensitivity to PLX4720 underwent synergistic increases and increased rates of apoptosis when combined with ABT-737. This degree of synergism was not seen in cell lines without BRAF V600E mutations. Apoptosis was mediated through the mitochondrial pathway and was due in part to upregulation of Bim as shown by inhibition of apoptosis following small interfering RNA knockdown of Bim. Similar effects were seen in cell lines established from patients prior to treatment but not in lines from patients clinically resistant to the selective BRAF inhibitors and in 3D spheroids derived from these cell lines. These results suggest that combination of selective BRAF inhibitors with ABT-737 or the related orally available compound ABT-263 may increase the degree and rate of responses in previously untreated patients with V600E melanoma but not in those with acquired resistance to these agents.

Topics: Apoptosis; Biphenyl Compounds; Blotting, Western; Cell Proliferation; Clinical Trials, Phase II as Topic; Drug Resistance, Neoplasm; Drug Synergism; Humans; Immunoprecipitation; Indoles; Melanoma; Membrane Potential, Mitochondrial; Mutation; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Piperazines; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-bcl-2; RNA, Small Interfering; Sulfonamides; Tumor Cells, Cultured

Drug resistance in melanoma is commonly attributed to ineffective apoptotic pathways. Inhibiting antiapoptotic BCL-2 and its relatives is an attractive strategy for sensitizing lymphoid malignancies to drugs but it has been largely unsuccessful for melanoma and other solid tumors. ABT-737, a small-molecule BH3-mimetic, selectively inhibits BCL-2, BCL-XL, and BCL-w and shows promise for treating leukemia, lymphoma, and small-cell lung cancer. Melanoma cells are insensitive to ABT-737, but MCL-1 inhibition reportedly increases the sensitivity of other tumors to the compound.. The efficacy of MCL-1 and BFL-1 inhibition for sensitizing melanoma cells to ABT-737 was investigated by short hairpin RNA-mediated knockdown or overexpression of their antagonist NOXA in two-dimensional cell culture, a three-dimensional organotypic spheroid model, and an in vivo model.. MCL-1 downregulation or NOXA overexpression strongly sensitized melanoma cells to ABT-737 in vitro. NOXA-inducing cytotoxic drugs also strongly sensitized melanomas to ABT-737 but, surprisingly, not vice versa. The drugs most suitable are not necessarily those normally used to treat melanoma. Resistance to ABT-737 occurred quickly in three-dimensional melanoma spheroids through reduced NOXA expression, although experiments with both xenografts and three-dimensional spheroids suggest that penetration of ABT-737 into tumor masses may be the principal limitation, which may be obviated through use of more diffusible BH3-mimetics.. Sensitization of tumors to BH3-mimetics by cytotoxic drugs that induce NOXA is a therapeutic strategy worth exploring for the treatment of melanoma and other solid cancers.

Topics: Animals; Antineoplastic Agents; Biphenyl Compounds; Cell Line, Tumor; Gene Knockdown Techniques; Humans; Immunoblotting; Male; Melanoma; Mice; Mice, Inbred NOD; Mice, SCID; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; RNA, Small Interfering; Sulfonamides; Transduction, Genetic; Xenograft Model Antitumor Assays

The small molecule inhibitor, ABT-737, inhibits Bcl-2 that is overexpressed in many tumor cell lines and, in combination with an anticancer drug, can strongly enhance proapoptotic activity. In the present study, we evaluated the inhibitory activity of ABT-737 on the survival of a canine melanoma cell line (MCM-N1). MCM-N1 cell viability was decreased following 24- and 48-hr culture with ABT-737, depending on ABT-737 concentration, while cell viability was unchanged in controls. ABT-737 synergized with carboplatin to promote cell death. Notably, approximately 50% of MCM-N1 cells survived following culture with 2-4 µg/ml of carboplatin; whereas, less than 20% of MCM-N1 cells survived following culture with ABT-737 (1 mM) plus carboplatin (2-10 µg/ml).

Topics: Animals; Biphenyl Compounds; Carboplatin; Cell Line, Tumor; Cell Survival; Dog Diseases; Dogs; Dose-Response Relationship, Drug; Melanoma; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Catechol-O-methyltransferase (COMT) is a ubiquitous enzyme inactivating catecholic compounds. COMT is expressed also in human skin samples, and in melanoma cells it may be cytoprotective. A role of COMT in keratinocytes (HaCat) is unknown.. The objective of this study is: to investigate whether ultraviolet-B (UVB) radiation modifies COMT activity in melanocytes and HaCat and whether COMT inhibition plays a role in UVB-induced cell death.. Human cell lines of melanotic melanoma (SK-mel-1) and HaCat were used. COMT activity was evaluated under basal conditions and after UVB irradiation (311 nm) at a low (8 mJ/cm(2)) and a high dose (60 mJ/cm(2)). Tolcapone 1 μM was used to inhibit COMT.. Both SK-mel-1 and Ha-Cat cells express COMT activity. In SK-mel-1, COMT activity is reduced nearly 50% both 24 h and 48 h after a high dose UVB. In Ha-Cat cells, COMT activity increased 24 h after a high dose UVB but decreased at 48 h. Tolcapone increases significantly the cytotoxic effect of high dose UVB irradiation only in HaCat. High concentrations of tolcapone reduced melanin levels in melanoma cells parallel to reduced cell numbers.. Ultraviolet radiation differentially modifies COMT activity in melanoma cells and HaCat. Furthermore, tolcapone increased death of HaCat after irradiation but did not affect melanoma cells.

Topics: Benzophenones; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Cell Death; Cell Line, Tumor; Enzyme Inhibitors; Humans; Keratinocytes; Melanoma; Neoplasm Proteins; Nitrophenols; Tolcapone; Ultraviolet Rays

Metastatic malignant melanoma is highly resistant to chemotherapy, and the average survival rate is under 1 year. The only FDA-approved conventional chemotherapy (i.e., dacarbazine) targets melanoma tumor cells by inducing a form of cell death referred to as apoptosis. However, dacarbazine exhibits a response rate of ~5%, and combination chemotherapies consisting of cisplatin, vinblastine, and dacarbazine often offer little clinical advantage over dacarbazine alone. Apoptosis is governed by the BCL-2 family of proteins, which is comprised of anti-apoptotic and pro-apoptotic members. To determine if the anti-apoptotic BCL-2 repertoire established the cell death threshold and chemoresistance in melanoma, a novel treatment strategy was designed to inhibit the anti-apoptotic BCL-2 members with ABT-737. Using various melanoma model systems, we determined the affects of ABT-737 on sensitivity to dacarbazine-based regimens. Strikingly, ABT-737 re-sensitized melanoma cell lines to common chemotherapeutics leading to marked BIM-mediated apoptosis. Cellular features of the ABT-737 combination treatments were loss of proliferation, mitochondrial fragmentation, nuclear condensation, phosphatidylserine exposure, and decreased clonogenic survival. We also observed significant anti-tumor activity in an in vivo melanoma model system. Our data indicate that ABT-737 may be a beneficial adjuvant therapy to improve melanoma response rates when conventional chemotherapy is the only option.

Topics: Antineoplastic Agents; Apoptosis; Biphenyl Compounds; Cell Line, Tumor; Cell Survival; Cisplatin; Humans; Melanoma; Mitochondria; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Metastatic melanoma is characterized by extremely poor survival rates and hence novel therapies are urgently required. The ability of many anticancer drugs to activate autophagy, a lysosomal-mediated catabolic process which usually promotes cell survival, suggests targeting the autophagy pathway may be a novel means to augment therapy.. Autophagy and apoptosis were assessed in vitro in human melanoma cell lines in response to clinically achievable concentrations of the endoplasmic reticulum (ER) stress-inducing drugs fenretinide or bortezomib, and in vivo using a s.c. xenograft model.. Autophagy was activated in response to fenretinide or bortezomib in B-RAF wild-type cells, shown by increased conversion of LC3 to the autophagic vesicle-associated form (LC3-II) and redistribution to autophagosomes and autolysosomes, increased acidic vesicular organelle formation and autophagic vacuolization. In contrast, autophagy was significantly reduced in B-RAF-mutated melanoma cells, an effect attributed partly to oncogenic B-RAF. Rapamycin treatment was unable to stimulate LC3-II accumulation or redistribution in the presence of mutated B-RAF, indicative of de-regulated mTORC1-dependent autophagy. Knockdown of Beclin-1 or ATG7 sensitized B-RAF wild-type cells to fenretinide- or bortezomib-induced cell death, demonstrating a pro-survival function of autophagy. In addition, autophagy was partially reactivated in B-RAF-mutated cells treated with the BH3 mimetic ABT737 in combination with fenretinide or bortezomib, suggesting autophagy resistance is partly mediated by abrogated Beclin-1 function.. Our findings suggest inhibition of autophagy in combination with ER stress-inducing agents may represent a means by which to harness autophagy for the therapeutic benefit of B-RAF wild-type melanoma.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Autophagy; Biphenyl Compounds; Blotting, Western; Boronic Acids; Bortezomib; Cell Line, Tumor; Endoplasmic Reticulum; Female; Fenretinide; Humans; Luminescent Proteins; Melanoma; Mice; Microscopy, Fluorescence; Microtubule-Associated Proteins; Nitrophenols; Piperazines; Proto-Oncogene Proteins B-raf; Pyrazines; RNA Interference; Signal Transduction; Sulfonamides; Xenograft Model Antitumor Assays

MicroRNAs play important roles in gene regulation, and their expression is frequently dysregulated in cancer cells. In a previous study, we reported that miR-193b represses cell proliferation and regulates cyclin D1 in melanoma cells, suggesting that miR-193b could act as a tumor suppressor. Herein, we demonstrate that miR-193b also down-regulates myeloid cell leukemia sequence 1 (Mcl-1) in melanoma cells. MicroRNA microarray profiling revealed that miR-193b is expressed at a significantly lower level in malignant melanoma than in benign nevi. Consistent with this, Mcl-1 is detected at a higher level in malignant melanoma than in benign nevi. In a survey of melanoma samples, the level of Mcl-1 is inversely correlated with the level of miR-193b. Overexpression of miR-193b in melanoma cells represses Mcl-1 expression. Previous studies showed that Mcl-1 knockdown cells are hypersensitive to ABT-737, a small-molecule inhibitor of Bcl-2, Bcl-X(L), and Bcl-w. Similarly, overexpression of miR-193b restores ABT-737 sensitivity to ABT-737-resistant cells. Furthermore, the effect of miR-193b on the expression of Mcl-1 seems to be mediated by direct interaction between miR-193b and seed and seedless pairing sequences in the 3' untranslated region of Mcl-1 mRNA. Thus, this study provides evidence that miR-193b directly regulates Mcl-1 and that down-regulation of miR-193b in vivo could be an early event in melanoma progression.

Topics: Antimetabolites, Antineoplastic; Apoptosis; Binding Sites; Biphenyl Compounds; Cell Line, Tumor; Cyclin D1; Down-Regulation; Drug Resistance, Neoplasm; Growth Inhibitors; Humans; Melanoma; MicroRNAs; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Skin Neoplasms; Sulfonamides

Metastatic melanoma has poor prognosis and is refractory to most conventional chemotherapies. The alkylating agent temozolomide (TMZ) is commonly used in treating melanoma but has a disappointing response rate. Agents that can act cooperatively with TMZ and improve its efficacy are thus highly sought after. The BH3 mimetic ABT-737, which can induce apoptosis by targeting pro-survival Bcl-2 family members, has been found to enhance the efficacy of many conventional chemotherapeutic agents in multiple cancers. We found that combining TMZ and ABT-737 induced strong synergistic apoptosis in multiple human melanoma cell lines. When the drugs were used in combination in a mouse xenograft model, they drastically reduced tumor growth at concentrations where each individual drug had no significant effect. We found that TMZ treatment elevated p53 levels, and that the pro-apoptotic protein Noxa was elevated in TMZ/ABT-737 treated cells. Experiments with shRNA demonstrated that the synergistic effect of TMZ and ABT-737 was largely dependent on Noxa. Experiments with nutlin-3, a p53 inducer, demonstrated that p53 induction was sufficient for synergistic cell death with ABT-737 in a Noxa-dependent fashion. However, p53 was not necessary for TMZ/ABT-737 synergy as demonstrated by a p53-null line, indicating that TMZ and ABT-737 together induce Noxa in a p53-independent fashion. These results demonstrate that targeting anti-apoptotic Bcl-2 members is a promising method for treating metastatic melanoma, and that clinical trials with TMZ and Bcl-2 inhibitors are warranted.

Topics: Alkylating Agents; Animals; Apoptosis; Biomimetic Materials; Biphenyl Compounds; Cell Line, Tumor; Dacarbazine; Drug Synergism; Female; Gene Expression Regulation, Neoplastic; Humans; Melanoma; Mice; Nitrophenols; Piperazines; Protein Structure, Tertiary; Proto-Oncogene Proteins c-bcl-2; Sulfonamides; Temozolomide; Time Factors; Tumor Suppressor Protein p53; Xenograft Model Antitumor Assays

In cancer, combinations of drugs targeting different cellular functions is well accepted to improve tumor control. We studied the effects of a Pseudomonas exotoxin A (PE)-based immunotoxin, the 9.2.27PE, and the BH-3 mimetic compound ABT-737 in a panel of melanoma cell lines. The drug combination resulted in synergistic cytotoxicity, and the cell death observed was associated with apoptosis, as activation of caspase-3, inactivation of Poly (ADP-ribose) polymerase (PARP) and increased DNA fragmentation could be prevented by pre-treatment with caspase and cathepsin inhibitors. We further show that ABT-737 caused endoplasmic reticulum (ER) stress with increased GRP78 and phosphorylated eIF2α protein levels. Moreover, treatment with ABT-737 increased the intracellular calcium levels, an effect which was enhanced by 9.2.27PE, which as a single entity drug had minimal effect on calcium release from the ER. In addition, silencing of Mcl-1 by short hairpin RNA (shRNA) enhanced the intracellular calcium levels and cytotoxicity caused by ABT-737. Notably, the combination of 9.2.27PE and ABT-737 caused growth delay in a human melanoma xenograft mice model, supporting further investigations of this particular drug combination.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Biphenyl Compounds; Blotting, Western; Calcium; Cell Line, Tumor; Cell Survival; DNA Fragmentation; Endoplasmic Reticulum Chaperone BiP; Female; Humans; Immunotoxins; Melanoma; Membrane Potential, Mitochondrial; Mice; Mice, Nude; Nitrophenols; Piperazines; Sulfonamides; Xenograft Model Antitumor Assays

The mitogen-activated protein kinase (MAPK) pathway is constitutively activated in the majority of melanomas, promoting cell survival, proliferation and migration. In addition, anti-apoptotic Bcl-2 family proteins Mcl-1, Bcl-xL and Bcl-2 are frequently overexpressed, contributing to melanoma's well-documented chemoresistance. Recently, it was reported that the combination of MAPK pathway inhibition by specific MEK inhibitors and Bcl-2 family inhibition by BH3-mimetic ABT-737 synergistically induces apoptotic cell death in melanoma cell lines. Here we provide the first evidence that inhibition of another key MAPK, p38, synergistically induces apoptosis in melanoma cells in combination with ABT-737. We also provide novel mechanistic data demonstrating that inhibition of p38 increases expression of pro-apoptotic Bcl-2 protein PUMA. Furthermore, we demonstrate that PUMA can be cleaved by a caspase-dependent mechanism during apoptosis and identify what appears to be the PUMA cleavage product. Thus, our findings suggest that the combination of ABT-737 and inhibition of p38 is a promising, new treatment strategy that acts through a novel PUMA-dependent mechanism.

Topics: Apoptosis Regulatory Proteins; Biphenyl Compounds; Caspases; Cell Death; Cell Line, Tumor; Cell Survival; Drug Synergism; Enzyme Activation; Gene Knockdown Techniques; Humans; Imidazoles; Melanoma; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; p38 Mitogen-Activated Protein Kinases; Piperazines; Protein Kinase Inhibitors; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Pyridines; Skin Neoplasms; Sulfonamides; Up-Regulation

Taspase1, the mixed lineage leukemia and TFIIAalpha-beta cleaving protease, enables cell proliferation and permits oncogenic initiation. Here, we show its critical role in cancer maintenance and thus offer a new anticancer target. Taspase1 is overexpressed in primary human cancers, and deficiency of Taspase1 in cancer cells not only disrupts proliferation but also enhances apoptosis. Mechanistically, loss of Taspase1 induces the levels of CDK inhibitors (CDKI: p16, p21, and p27) and reduces the level of antiapoptotic MCL-1. Therapeutically, deficiency of Taspase1 synergizes with chemotherapeutic agents and ABT-737, an inhibitor of BCL-2/BCL-X(L), to kill cancer cells. Taspase1 alone or in conjunction with MYC, RAS, or E1A fails to transform NIH/3T3 cells or primary mouse embryonic fibroblasts, respectively, but plays critical roles in cancer initiation and maintenance. Therefore, Taspase1 is better classified as a "non-oncogene addiction" protease, the inhibition of which may offer a novel anticancer therapeutic strategy. The reliance of oncogenes on subordinate non-oncogenes during tumorigenesis underscores the non-oncogene addiction hypothesis in which a large class of non-oncogenes functions to maintain cancer phenotypes and presents attractive anticancer therapeutic targets. The emergence of successful cancer therapeutics targeting non-oncogenes to which cancers are addicted supports the future development and potential application of small-molecule Taspase1 inhibitors for cancer therapy.

Topics: Animals; Antineoplastic Agents; Apoptosis; Biphenyl Compounds; Cell Growth Processes; Cell Line, Transformed; Cell Line, Tumor; Endopeptidases; Genes, myc; Genes, ras; Glioblastoma; Humans; Male; Melanoma; Mice; Mice, Inbred NOD; Mice, SCID; Myeloid Cell Leukemia Sequence 1 Protein; NIH 3T3 Cells; Nitrophenols; Piperazines; Proto-Oncogene Proteins c-bcl-2; Sulfonamides; Transduction, Genetic; Transfection

The Bcl-2 family is important in modulating sensitivity to anticancer drugs in many cancers, including melanomas. The BH3 mimetic ABT-737 is a potent small molecule inhibitor of the anti-apoptotic proteins Bcl-2/Bcl-X(L)/Bcl-w. In this report, we examined whether ABT-737 is effective in killing melanoma cells in combination with the proteasome inhibitor MG-132, and further evaluated the mechanisms of action. Viability, morphological, and Annexin V apoptosis assays showed that ABT-737 alone exhibited little cytotoxicity, yet it displayed strong synergistic lethality when combined with MG-132. In addition, the detection of Bax/Bak activation indicated that the combination treatment synergistically induced mitochondria-mediated apoptosis. Furthermore, mechanistic analysis revealed that this combination treatment induced expression of the pro-apoptotic protein Noxa- and caspase-dependent degradation of the anti-apoptotic protein, Mcl-1. Finally, siRNA-mediated inhibition of Mcl-1 expression significantly increased sensitivity to ABT-737 in these cells, and knocking down Noxa expression protected the cells from cytotoxicity induced by the combination treatment. These findings demonstrate that ABT-737 combined with MG-132 synergistically induced Noxa-dependent mitochondrial-mediated apoptosis. In summary, this study indicates promising therapeutic potential of targeting anti-apoptotic Bcl-2 family members in treating melanoma, and it validates rational molecular approaches that target anti-apoptotic defenses when developing cancer treatments.

Topics: Antineoplastic Agents; Apoptosis; Biphenyl Compounds; Caspases; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Drug Synergism; Humans; Leupeptins; Melanoma; Mitochondria; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Piperazines; Proteasome Inhibitors; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Constitutive activation of the mitogen-activated protein kinase (MAPK) pathway is implicated in the development and progression of many human cancers, including melanoma. Mutually exclusive activating mutations in NRAS or BRAF have been identified in approximately 85% of melanomas, and components of this pathway have been developed as molecular targets for therapeutic intervention. We and others have shown that inhibition of this pathway with specific small molecule MAPK/extracellular signal-regulated kinase kinase (MEK) inhibitors induces a wide range of apoptotic responsiveness in human melanoma cells both in vitro and in vivo. To define the molecular mechanism underlying variable apoptotic sensitivity of melanoma cells to MEK inhibition, we examined the expression and subcellular localization of Bcl-2 family members in a comprehensive set of human melanoma cell lines. Whereas the proapoptotic protein Bim was activated and localized to the mitochondrial membrane in all cell lines regardless of apoptotic sensitivity, Bmf activation and cytosolic translocation was exclusive to sensitive cells. In resistant cells, Bmf remained sequestered to the cytoskeleton through dynein light chain 2 (DLC2) binding. Overexpression of Bmf in resistant cells did not enhance apoptosis, whereas expression of mutant BmfA69P, which has decreased binding to DLC2, promoted cell death. Expression of BmfA69P mutants possessing the Bcl-2 homology 3 (BH3) domain mutation L138A, which impairs BH3 interactions, did not enhance apoptosis in resistant cells. RNA interference targeting Bim and Bmf provided protection from apoptosis induced by MEK inhibition. These results show a novel role for Bmf in promoting apoptosis and provide insight into the mechanism of apoptotic resistance to MEK inhibition in melanoma.

Topics: Adaptor Proteins, Signal Transducing; Apoptosis; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Benzamides; Biphenyl Compounds; Caspases; Cell Line, Tumor; Drug Resistance, Neoplasm; Extracellular Signal-Regulated MAP Kinases; Humans; Melanoma; Membrane Proteins; Mitogen-Activated Protein Kinase Kinases; Nitrophenols; Piperazines; Protein Kinase Inhibitors; Protein Transport; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

Malignant melanoma is resistant to almost all conventional forms of chemotherapy. Recent evidence suggests that anti-apoptotic proteins of the Bcl-2 family are overexpressed in melanoma and may contribute to melanoma's striking resistance to apoptosis. ABT-737, a small-molecule inhibitor of Bcl-2, Bcl-xl and Bcl-w, has demonstrated efficacy in several forms of leukemia, lymphoma as well as solid tumors. However, overexpression of Mcl-1, a frequent observance in melanoma, is known to confer ABT-737 resistance.. Here we report that knockdown of Mcl-1 greatly reduces cell viability in combination with ABT-737 in six different melanoma cell lines. We demonstrate that the cytotoxic effect of this combination treatment is due to apoptotic cell death involving not only caspase-9 activation but also activation of caspase-8, caspase-10 and Bid, which are normally associated with the extrinsic pathway of apoptosis. Caspase-8 (and caspase-10) activation is abrogated by inhibition of caspase-9 but not by inhibitors of the death receptor pathways. Furthermore, while caspase-8/-10 activity is required for the full induction of cell death with treatment, the death receptor pathways are not. Finally, we demonstrate that basal levels of caspase-8 and Bid correlate with treatment sensitivity.. Our findings suggest that the combination of ABT-737 and Mcl-1 knockdown represents a promising, new treatment strategy for malignant melanoma. We also report a death receptor-independent role for extrinsic pathway proteins in treatment response and suggest that caspase-8 and Bid may represent potential markers of treatment sensitivity.

Topics: Apoptosis; Biphenyl Compounds; Caspase 8; Cell Line, Tumor; Gene Knockdown Techniques; Humans; Melanoma; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Piperazines; Polymorphism, Genetic; Proto-Oncogene Proteins c-bcl-2; RNA Interference; Sulfonamides

Even though activating mutations of B-Raf, a kinase atop the MAPK signaling cascade, reportedly sensitize tumor cells to MEK inhibitors, Raf and MEK inhibitors have exhibited limited clinical activity. In this issue of the JCI, Cragg et al. report that MEK inhibition upregulates the proapoptotic Bcl-2 family member Bim but induces little regression of human melanoma xenografts in mice unless the Bcl-2 antagonist ABT-737 is added (see the related article beginning on page 3651). These findings illustrate the potential benefit of simultaneously inhibiting oncogenic kinases and inhibiting Bcl-2 action in solid tumors.

Topics: Animals; Apoptosis Regulatory Proteins; bcl-2 Homologous Antagonist-Killer Protein; Bcl-2-Like Protein 11; Biphenyl Compounds; Humans; Melanoma; Membrane Proteins; Mice; Mitogen-Activated Protein Kinase Kinases; Models, Biological; Nitrophenols; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins B-raf; Skin Neoplasms; Sulfonamides; Xenograft Model Antitumor Assays

The cytotoxic effects of anticancer immune cells are mediated by perforin/granzyme-B, Fas ligand and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), and therefore depend on intact apoptotic responses in target tumour cells. As killing by all three of these mechanisms is blocked by the frequently overexpressed antiapoptotic oncoprotein Bcl-2, we hypothesised that coexposure to a Bcl-2 inhibitor might enhance anticancer immune responses. We evaluated this in U937 lymphoma cells, and A02 melanoma cells, which both show strong Bcl-2 expression. Valpha24(+) Vbeta11(+) natural killer T (NKT) cells expanded from peripheral blood of normal donors (n=3) were coincubated with PKH26-labelled U937 cells, and cytotoxicity was determined by flow cytometry after annexin-V-FITC and 7-AAD staining. In all cases, addition of the HA14-1 small-molecule Bcl-2 inhibitor to the cocultures significantly increased apoptosis in the target U937 cells. Using a similar assay, killing of A02 cells by the cytotoxic T-lymphocyte clone 1H3 was shown to be amplified by coexposure to the potent small-molecule Bcl-2 inhibitor ABT-737. Experiments with immune effectors preincubated with concanamycin-A suggested that sensitisation to perforin/granzyme-B may underlie enhanced target-cell killing observed in the presence of Bcl-2 inhibitors. We conclude that immune destruction of malignant cells can be amplified by molecular interventions that overcome Bcl-2-mediated resistance to apoptosis.

Topics: Adult; Antineoplastic Agents; Benzopyrans; Biphenyl Compounds; Cell Line, Tumor; Cell Proliferation; Enzyme Inhibitors; Granzymes; Humans; Lymphoma; Melanoma; Membrane Glycoproteins; Nitriles; Nitrophenols; Perforin; Piperazines; Pore Forming Cytotoxic Proteins; Proto-Oncogene Proteins c-bcl-2; Sensitivity and Specificity; Structure-Activity Relationship; Sulfonamides

One hundred eighty-three patients with advanced solid neoplasms were tested for their ability to react to four common skin test antigens (tuberculin PPD, streptokinase-streptodornase, mumps, and Monilia) and their ability to develop delayed cutaneous hypersensitivity (DCH) to 2, 4 dinitrochlorobenzene (DNCB). All patients were followed for at least 6 months or until death. Histologic tumor types studied were: melanoma (65), sarcoma (28), squamous cell carcinoma (23), and adenocarcinoma (67). The rate of progression of disease within 6 months of testing was lower in patients who had a positive response to a challenging dose of 50 mug of DNCB. Reactivity to recall antigens had no prognostic value except in patients with adenocarcinomas. Among patients with adenocarcinoma, those who reacted strongly to DNCB and one or more skin test antigens had the best prognosis, while those who were nonreactive to all had the worst prognosis (progression rate: 18% vs. 78%). Peripheral lymphocyte counts were related to the results of DCH to DNCB and skin tests. The preseence or absence of lymphocytopenia (count less than 1000/mm3) had prognostic value in patients who had positive skin test(s). In such patients, the disease progression rate was much higher in patients who were anergic to DNCB and who were lymphocytopenic (90% vs. 40%). These data suggest that DCH to DNCB, recall antigens, and peripheral lymphocyte counts are useful immunologic measurements in patients with advanced cancer. Although the prognostic value of each individual test is relatively limited, the predictive worth can be increased when multiple tests are employed. Pertinent findings reported in the literature are reviewed.

Topics: Adenocarcinoma; Candida; Carcinoma, Squamous Cell; Humans; Hypersensitivity, Delayed; Immunity, Cellular; Leukocyte Count; Lymphocytes; Melanoma; Mumps virus; Neoplasms; Nitrophenols; Prognosis; Sarcoma; Skin Tests; Streptodornase and Streptokinase; Time Factors; Tuberculin Test