The incidence of cutaneous malignant melanoma in the United States has increased more than any other cancer in recent years. Chemotherapy for metastatic melanoma is disappointing, there being anecdotal cases of complete remission. Dacarbazine (DTIC) is considered the gold standard for treatment, having a response rate of 15-20%, but most responses are not sustained. The mechanisms for the increased chemotherapeutic resistance of melanoma are unclear. The objective of this study was to determine the mechanisms by which melanoma cells escape the cytotoxic effect of DTIC. Here, we show that DTIC induced interleukin (IL)-8 and vascular endothelial growth factor (VEGF) protein overexpression and secretion via transcriptional up-regulation in the two melanoma cell lines SB-2 and MeWo. Luciferase activity driven by the IL-8 and VEGF promoters was up-regulated by 1.5-2- and 1.6-3.5-fold, respectively, in the SB2 and MeWo melanoma cell lines. The mitogen-activated protein kinase signal transduction pathway seemed to regulate at least partially the activation of IL-8, whereas it was not involved in VEGF promoter regulation. Electrophoretic mobility shift analysis analyses have revealed an increase in binding activity of activator protein 1 (c-Jun) and nuclear factor-kappaB after DTIC treatment for both melanoma cell lines. Metastatic melanoma cell lines secreting high levels of IL-8 and VEGF were more resistant to DTIC than early primary melanomas secreting low levels of the cytokines. In addition, transfection of the primary cutaneous melanoma SB-2 cells with the IL-8 gene rendered them resistant to the cytotoxic effect of the drug, whereas the addition of IL-8-neutralizing antibody to metastatic melanoma cells lowered their sensitivity to DTIC. Taken together, our data demonstrate that DTIC can cause melanoma cells to secrete IL-8 and VEGF, which might render them resistant to the cytotoxic effects of the drug. We propose that combination treatment with anti-VEGF/IL-8 agents may potentiate the therapeutic effects of DTIC.
"Through DNA alkylation assays and combinatorial treatments using DTIC and a MGMT inhibitor we provide clear evidence that light exposure does not transform DTIC into a DNA methylating agent, but rather an inhibitor of DNA synthesis. This finding is of major importance considering that light activation of DTIC has been extensively used to study the mechanisms underlying its cytotoxic effects as well as leading to acquired resistance in patients [28-31]. In this context it is important to mention that wild type BRAF melanoma cells that had been selected for resistance to light activated DTIC in vitro exhibited increased tumour growth in vivo, a phenotype that correlates well with enhanced DNA synthesis activity . "
[Show abstract][Hide abstract] ABSTRACT: Background
The importance of the genetic background of cancer cells for the individual susceptibility to cancer treatments is increasingly apparent. In melanoma, the existence of a BRAF mutation is a main predictor for successful BRAF-targeted therapy. However, despite initial successes with these therapies, patients relapse within a year and have to move on to other therapies. Moreover, patients harbouring a wild type BRAF gene (including 25% with NRAS mutations) still require alternative treatment such as chemotherapy. Multiple genetic parameters have been associated with response to chemotherapy, but despite their high frequency in melanoma nothing is known about the impact of BRAF or NRAS mutations on the response to chemotherapeutic agents.
Using cell proliferation and DNA methylation assays, FACS analysis and quantitative-RT-PCR we have characterised the response of a panel of NRAS and BRAF mutant melanoma cell lines to various chemotherapy drugs, amongst them dacarbazine (DTIC) and temozolomide (TMZ) and DNA synthesis inhibitors.
Although both, DTIC and TMZ act as alkylating agents through the same intermediate, NRAS and BRAF mutant cells responded differentially only to DTIC. Further analysis revealed that the growth-inhibitory effects mediated by DTIC were rather due to interference with nucleotide salvaging, and that NRAS mutant melanoma cells exhibit higher activity of the nucleotide synthesis enzymes IMPDH and TK1. Importantly, the enhanced ability of RAS mutant cells to use nucleotide salvaging resulted in resistance to DHFR inhibitors.
In summary, our data suggest that the genetic background in melanoma cells influences the response to inhibitors blocking de novo DNA synthesis, and that defining the RAS mutation status could be used to stratify patients for the use of antifolate drugs.
Molecular Cancer 06/2014; 13(1):154. DOI:10.1186/1476-4598-13-154 · 4.26 Impact Factor
"VEGF and fibroblast growth factor (FGF) are angiogenic factors that have been implicated in melanoma progression and growth. VEGF is also up-regulated in melanoma cells when exposed to chemotherapy. Bevacizumab, a monoclonal antibody that binds extracellular VEGF, has been evaluated in multiple studies for the treatment of metastatic melanoma. "
[Show abstract][Hide abstract] ABSTRACT: Until recently, options for therapy in metastatic melanoma were limited. The understanding of immune check-point blockade and the discovery of molecular pathways involving driver mutations like BRAF has transformed the therapeutic landscape in this disease. Ipilimumab was the first drug shown to improve survival while vemurafenib demonstrated rapid responses never seen before in melanoma. Drugs from these classes and others are now in advanced stages of development and primed to positively impact patient survival in an incremental fashion. In this review, we highlight some of the developments during this renaissance in melanoma therapy and discuss agents of promise. Clinical challenges we face include individualizing therapy for patients, overcoming resistance to molecularly targeted therapy and developing rationale combinations or sequences of drugs. A concerted bench and bedside effort in this direction will undoubtedly keep melanoma in the forefront in an era of personalized medicine.
Journal of Carcinogenesis 02/2014; 13(1):1. DOI:10.4103/1477-3163.126759
"Plitidepsin triggers apoptosis in vitro and blocks VEGF secretion in different tumour models. The finding that DTIC increases protein expression of VEGF and promotes tumour growth and metastasis in vivo in human melanoma cells (Lev et al, 2003, 2004) suggested that a combination of plitidepsin and DTIC might have synergistic antineoplastic effects in metastatic melanoma. Plitidepsin showed sustained clinical antitumour activity in a melanoma patient in a phase I study (Anthoney et al, 2000). "
[Show abstract][Hide abstract] ABSTRACT: Background:
This phase I–II trial compared plitidepsin 1-h infusion alone or combined with dacarbazine (DTIC) 1-h infusion as front-line therapy for advanced melanoma.
The recommended dose (RD) for plitidepsin/DTIC was defined in the first stage. In the second stage, patients were randomised to receive single-agent plitidepsin 3.2 mg m−2 (n=20) on days 1, 8 and 15 every 4 weeks (q4wk) or plitidepsin 2.4 mg m−2 on days 1, 8 and 15 q4wk combined with DTIC 800 mg m−2 q4wk (n=38).
The overall response rate with plitidepsin/DTIC was 21.4% all responders had normal serum lactate dehydrogenase (LDH) levels and performance status ⩽1 at baseline. Median progression-free survival (PFS) with plitidepsin/DTIC was 3.3 months in all patients, and 4.3 months in those with baseline normal LDH. No responses occurred with single-agent plitidepsin and median PFS was 1.5 months. Both regimens were well tolerated. Haematological abnormalities were more common and transaminase increases more severe with plitidepsin/DTIC. Treatment-related transaminase increases leading to infusion omission on day 8 were relatively common. No drug–drug pharmacokinetic interactions were found.
This plitidepsin/DTIC schedule has antitumour activity and manageable toxicity in advanced melanoma. Further evaluation of plitidepsin 2.4 mg m−2 fortnightly and DTIC 800 mg m−2 q4wk is recommended.
British Journal of Cancer 08/2013; 109(6). DOI:10.1038/bjc.2013.477 · 4.84 Impact Factor
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