Classical chemotherapy for metastatic melanoma

Repurposing melanoma chemotherapy to activate inflammasomes in treatment of BRAF/MAPK inhibitor resistant melanoma

The development of resistance to treatments of melanoma is commonly associated with upregulation of the MAPK pathway and development of an undifferentiated state. Prior studies have suggested that melanoma with these resistance characteristics may be susceptible to innate death mechanisms such as pyroptosis triggered by activation of inflammasomes. In the present studies we have taken cell lines from patients before and after development of resistance to BRAF V600 inhibitors and exposed the resistant melanoma to temozolomide (a commonly used chemotherapy) with and without chloroquine to inhibit autophagy. It was found that melanoma with an inflammatory undifferentiated state appeared susceptible to this combination when tested in vitro and in vivo against xenografts in NSG mice. Translation of the latter results into patients would promise durable responses in patients treated by the combination. The inflammasome and death mechanism involved appeared to vary between melanoma and involved either AIM2 or NLRP3 inflammasomes and gasdermin D or E. These preliminary studies have raised questions as to the selectivity for different inflammasomes in different melanoma and their selective targeting by chemotherapy. They also question whether the inflammatory state of melanoma may be used as biomarkers to select patients for inflammasome targeted therapy.

Assessment of the Chemosensitivity of Uveal Melanoma Cells Ex Vivo

The study was designed to create a primary cell culture of uveal melanoma and to evaluate its resistance to chemotherapy. Of the obtained 20 samples of uveal melanoma, the primary cultures with proliferation sufficient for MTT test were derived in only 7 cases. However, even these cultures were unable to survive more than 4 passages; the cells accumulated melanin and underwent apoptosis. Retinol palmitate and nepafenac produced no cytotoxic effect on uveal melanoma cells. Of 5 cultures treated with sodium valproate (Convulex), no pronounced cytotoxic effect was observed in one culture (UM4); in 2 cultures, 50% cells died in the presence of the lowest drug concentration of 1.88 mg/ml; and in 2 cultures, the same effect was achieved at drug concentrations 7-10 mg/ml. The cytotoxic effect of treosulfan was evaluated in only 4 cultures of uveal melanoma: the drug exhibited pronounced antitumor activity on all cultures, in 2 cases, it was effective at a concentration of 0.16 mg/ml. Gemcitabine in a concentration of 2.5 mg/ml produced a pronounced cytotoxic effect in 4 out of 7 cultures (death of 70-80% cells) and induced death of ~45% cells in the remaining 3 cultures. Mitoxantrone had ambiguous effect: in 2 of 5 cultures, the drug in high concentrations stimulated the growth of tumor cells, but in 3 cultures, the drug even in minimum concentrations induced death of 70-80% cells.

Dinitrophenyl hapten with laser immunotherapy for advanced malignant melanoma: A clinical study

The present study aimed to evaluate the efficacy and safety of in situ immunotherapy with dinitrophenyl (DNP) hapten in combination with laser therapy for patients with malignant melanoma (MM). Between February 2008 and March 2012, 72 patients with stage III or IV MM were enrolled. Patients received in situ DNP alone (n=32) or in combination with laser therapy (n=32), and each group received dacarbazine chemotherapy. The levels of peripheral cluster of differentiation (CD)4⁺CD25⁺ regulatory T cells (Tregs), interleukin (IL)-10 and tumor growth factor (TGF)-β were detected by ELISA. The association between delayed-type hypersensitivity (DTH) and survival time was evaluated. Although peripheral Treg levels significantly decreased over time in the two groups (P<0.001), there was no significant difference between the treatment groups (P=0.098). Patients receiving the combination treatment exhibited significantly higher interferon-γ production by CD8⁺ and CD4⁺ T cells (both P<0.001), as well as significantly reduced levels of IL-10, TGF-β1 and TGF-β2. In addition, patients in the combination treatment group experienced significantly longer overall survival (OS; P=0.024) and disease-free survival (DFS; P=0.007) times; a DTH response of ≥15 mm was also associated with increased OS time and DFS time (P≤0.001). Finally, no severe adverse events were observed in either treatment group. Overall, in situ immunization with DNP in combination with laser immunotherapy may activate focal T cells, producing a regional antitumor immune response that increases cell-mediated immunity and improves survival in MM patients. Thus, this may represent a novel therapeutic strategy for patients with unresectable, advanced MM.

Skewed Differentiation of Circulating Vγ9Vδ2 T Lymphocytes in Melanoma and Impact on Clinical Outcome

Objective

The aim of this study was to evaluate over time circulating γδ T lymphocytes in melanoma patients in terms of frequency, effector functions, and relationship with clinical stage and evolution, by comparing preoperative values to those obtained at a mean follow-up of 36 months or in the event of recurrence or disease progression, and to those of healthy controls. Also, we correlated the presence of tumor-infiltrating γδ T lymphocytes with clinical evolution of melanoma.

Results

Mean frequencies of circulating γδ T cells before and after melanoma removal were very similar and comparable to healthy subjects, but patients who progressed to stage III or IV showed a significantly decreased frequency of circulating Vγ9Vδ2 T cells. The distribution of Vγ9Vδ2 memory and effector subsets was similar in healthy subjects and melanoma patients at diagnosis, but circulating γδ T cells of patients after melanoma removal had a skewed terminally-differentiated effector memory phenotype. Highly suggestive of progressive differentiation toward a cytotoxic phenotype, Vγ9Vδ2T cells from patients at follow up had increased cytotoxic potential and limited cytokine production capability, while the opposite pattern was detected in Vγ9Vδ2T cells from patients before melanoma removal.

Conclusions

Follow-up data also showed that tumor infiltrating γδ T cells were significantly associated with lower mortality and relapse rates, suggesting that they may serve as a prognostic biomarker, for human melanoma.

2D-DIGE analysis of phospho-enriched fractions from dasatinib-treated melanoma cell lines

Current therapeutic regimes for metastatic melanoma have failed to provide robust clinical responses. Dasatinib has shown anti-proliferative and anti-invasive effects in vitro; however, not all melanoma cells tested were sensitive to dasatinib. We used 2D-DIGE analysis of phospho-enriched fractions to identify phosphoproteins involved in regulating response to dasatinib in an isogenic pair of melanoma cell lines, one sensitive to dasatinib (WM-115) and the other resistant (WM-266-4). In WM-115 cells treated with dasatinib, 18 unique protein species with altered phosphorylation levels were detected. Dasatinib treatment of WM-266-4 cells resulted in phosphoprotein alterations to four unique protein species. Four phosphorylated forms of Annexin-A2 (ANXA2) were increased in WM-115 cells treated with dasatinib, whilst dasatinib treatment did not alter ANXA2 phosphoprotein levels in WM-266-4 cells. Immunoblotting confirmed that phosphorylation of ANXA2, on tyrosine residues, was increased in WM-115 cells treated with dasatinib. Subsequent knockdown of ANXA2 by siRNA significantly inhibited proliferation of WM-115 cells but did not significantly reduce proliferation of WM-266-4 cells. Therefore, ANXA2 plays a role in regulating proliferation in dasatinib-sensitive WM-115 cells and could potentially play a role in sensitivity to dasatinib in melanoma cells.

Targeting CXCR1/CXCR2 receptor antagonism in malignant melanoma

IMPORTANCE OF THE FIELD

The incidence of malignant melanoma is increasing throughout the world and is currently rising faster than any other cancer in men and second only to lung cancer in women. Current strategies focused on systemic therapy for treatment of melanoma have shown no effect on survival. Therefore there is a pressing need for developing novel targeted therapeutics.

AREAS COVERED IN THIS REVIEW

Our goal is to provide an overview regarding targeting CXCR1/2 in malignant melanoma, the rationale behind these approaches and the future perspective.

WHAT THE READER WILL GAIN

This review illustrates our current understanding of CXCR1/2 receptor in melanoma progression and metastasis. We describe approaches that are being developed to block CXCR1/2 activation, including low-molecular-weight antagonists, modified chemokines and antibodies directed against ligands and receptors.

TAKE HOME MESSAGE

The chemokine receptors CXCR1 and CXCR2 and their ligands play an important role in the pathogenesis of malignant melanoma. Recent reports demonstrated that CXCR1 is constitutively expressed in all melanoma cases irrespective of stage and grade, however, CXCR2 expression was restricted to aggressive melanoma tumors,. Furthermore, modulation of CXCR1/2 expression and/or activity has been shown to regulate malignant melanoma growth, angiogenesis and metastasis, suggesting CXCR1/2 targeting as a novel therapeutic approach for malignant melanoma.

A(2B) and A(3) adenosine receptors modulate vascular endothelial growth factor and interleukin-8 expression in human melanoma cells treated with etoposide and doxorubicin

Cancer patients undergoing treatment with systemic cancer chemotherapy drugs often have abnormal growth factor and cytokine profiles. Thus, serum levels of interleukin-8 (IL-8) are elevated in patients with malignant melanoma. In addition to IL-8, aggressive melanoma cells secrete, through its transcriptional regulator hypoxia-inducible factor 1 (HIF-1), vascular endothelial growth factor (VEGF), which promotes angiogenesis and metastasis of human cancerous cells. Whether these responses are related to adenosine, a ubiquitous mediator expressed at high concentrations in cancer and implicated in numerous inflammatory processes, is not known and is the focus of this study. We have examined whether the DNA-damaging agents etoposide (VP-16) and doxorubicin can affect IL-8, VEGF, and HIF-1 expressions in human melanoma cancer cells. In particular, we have investigated whether these responses are related to the modulation of the adenosine receptor subtypes, namely, A(1), A(2A), A(2B), and A(3). We have demonstrated that A(2B) receptor blockade can impair IL-8 production, whereas blocking A(3) receptors, it is possible to further decrease VEGF secretion in melanoma cells treated with VP-16 and doxorubicin. This understanding may present the possibility of using adenosine antagonists to reduce chemotherapy-induced inflammatory cytokine production and to improve the ability of chemotherapeutic drugs to block angiogenesis. Consequently, we conclude that adenosine receptor modulation may be useful for refining the use of chemotherapeutic drugs to treat human cancer more effectively.

JWA regulates melanoma metastasis by integrin alphaVbeta3 signaling

JWA, a newly identified novel microtubule-associated protein (MAP), was recently demonstrated to be indispensable for the rearrangement of actin cytoskeleton and activation of MAPK cascades induced by arsenic trioxide (As(2)O(3)) and phorbol ester (PMA). JWA depletion blocked the inhibitory effect of As(2)O(3) on HeLa cell migration, but enhanced cell migration after PMA treatment. As cancer cell migration is a hallmark of tumor metastasis and the functional role of JWA in cancer metastasis is not understood, here we show that JWA has an important role in melanoma metastasis. Our data demonstrated that JWA knockdown increased the adhesion and invasion abilities of melanoma cells. Furthermore, JWA knockdown in B16-F10 and A375 melanoma cells significantly promoted the formation and growth of metastatic colonies in vivo. Moreover, in the tumor biopsies from human melanoma patients, JWA expression was significantly decreased in malignant melanoma compared with normal nevi. In addition, we found that JWA knockdown could intensify tumor integrin alpha(V)beta(3) signaling by regulating nuclear factor Sp1. These findings suggest that JWA suppresses melanoma metastasis and may serve a potential therapeutic target for human melanoma.

Non-toxic melanoma therapy by a novel tubulin-binding agent

(S)-3-((R)-9-bromo-4-methoxy-6-methyl-5,6,7,8-tetrahydro-[1,3]dioxolo[4,5-g]isoquino-lin-5-yl)-6,7-dimethoxyisobenzofuran-1(3H)-one (EM011) is a tubulin-binding agent with significant anticancer activity. Here we show that EM011 modulates microtubule dynamics at concentrations that do not alter the total polymer mass of tubulin. In particular, EM011 decreases the transition frequencies between growth and shortening phases and increases the duration microtubules spend in an idle 'pause' state. Using B16LS9 murine melanoma cells, we show that EM011 briefly arrests cell-cycle progression at the G2/M phase by formation of multiple aster spindles. An aberrant mitotic exit without cytokinesis then occurs, leading to the accumulation of abnormal multinucleated cells prior to apoptosis. Our pharmacokinetic studies conformed to a linear dose-response relationship upto 150 mg/kg. However, non-linearity was observed at 300 mg/kg. In a syngeneic murine model of subcutaneous melanoma, better antitumor responses were seen at 150 mg/kg compared to 300 mg/kg of EM011. Unlike currently available chemotherapeutics, EM011 is non-toxic to normal tissues and most importantly, does not cause any immunosuppression and neurotoxicity. Our data thus warrant a clinical evaluation of EM011 for melanoma therapy.

Tumor immunotherapy in melanoma: strategies for overcoming mechanisms of resistance and escape

The incidence of melanoma has been steadily increasing over the last 3 decades. Currently, there are several approved treatments for metastatic melanoma, including chemotherapy and biologic therapy as both single treatments and in combination, but none is associated with a significant increase in survival. The chemotherapeutic agent dacarbazine is the standard treatment for metastatic melanoma, with a response rate of 15-20%, although most responses are not sustained. One of the main problems with melanoma treatment is chemotherapeutic resistance. The mechanisms of resistance of melanoma cells to chemotherapy have yet to be elucidated. Following treatment with dacarbazine, melanoma cells activate the extracellular signal-regulated kinase pathway, which results in over-expression and secretion of interleukin (IL)-8 and vascular endothelial growth factor. Melanoma cells utilize this mechanism to escape from the cytotoxic effect of the drug. We have previously reported on the development of fully human neutralizing antibodies against IL-8 (anti-IL-8-monoclonal-antibody [ABX-IL8]). In preclinical studies, ABX-IL8 inhibited tumor growth, angiogenesis, and metastasis of human melanoma in vivo. We propose that combination treatment with dacarbazine and IL-8 will potentiate the cytotoxic effect of the drug. Furthermore, formation of metastasis is a multistep process that includes melanoma cell adhesion to endothelial cells. Melanoma cell adhesion molecule (MUC18) mediates these processes in melanoma and is therefore a good target for eliminating metastasis. We have developed a fully human antibody against MUC18 that has shown promising results in preclinical studies. Since resistance is one of the major obstacles in the treatment of melanoma, we propose that utilization of antibodies against IL-8 or MUC18 alone, or as part of a 'cocktail' in combination with dacarbazine, may be a new treatment modality for metastatic melanoma that overcomes resistance of the disease to chemotherapy and significantly improves survival of patients.

New approaches in metastatic melanoma: biological and molecular targeted therapies

Classical metastatic melanoma therapy is disappointing but important progress has been made in the understanding of melanoma biology. Genetic lesions and several intracellular signaling pathways that could serve as targets for novel therapy have been identified and a number of new agents are under evaluation. Promising tumor cell targets were identified in the cell membrane, cytoplasm and nucleus. New therapeutic approaches, besides monoclonal antibodies and vaccination, include an increasing number of small molecules that have been shown to interfere restrictively with intracellular signaling pathways in melanoma and decrease proliferation, survival, migration or invasion. Other agents can interfere with stromal components of melanoma, such as angiogenesis and components of the immune system.

Chemoimmunotherapy for cutaneous melanoma with dacarbazine and epifocal contact sensitizers: results of a nationwide survey of the German Dermatologic Co-operative Oncology Group

PURPOSE

To scrutinize published data from small mono-centric studies and case reports which implicated high response rates and promising survival times for a combination therapy consisting of epifocal dinitrochlorobenzene (DNCB) and dacarbazine (DTIC) for metastasized melanoma. This therapy merges the effects of an allergic contact dermatitis elicited at the site of a cutaneous metastasis, and systemic chemotherapy.

METHODS

We performed a retrospective survey with nine German centers and evaluated 72 patients treated from 1993 to 2005.

RESULTS

The objective response rate in stage III melanoma (n = 39) was 62%. In contrast, only 9% objective responses were observed in 33 stage IV patients. Interestingly, more than half of patients with objective remissions remained progression-free for more than 1 year irrespective of the stage of disease.

CONCLUSIONS

Epifocal DNCB combined with DTIC is effective in patients with regionally metastasized melanoma not amenable to surgery or isolated limb perfusion, whereas in stage IV disease in spite of few durable remissions the addition of DNCB does not improve the therapeutic efficacy of DTIC.

Antisense-mediated melanoma inhibitor of apoptosis protein downregulation sensitizes G361 melanoma cells to cisplatin

Malignant melanoma is an aggressive form of skin cancer that is highly resistant to conventional therapies. The melanoma inhibitor of apoptosis protein is a potent inhibitor of apoptosis and is overexpressed in melanoma cells, but undetectable in most normal tissues including melanocytes. We designed 20-mer phosphorothioate antisense oligonucleotides complementary to five putatively single-stranded sites on the melanoma inhibitor of apoptosis protein mRNA and investigated their ability to sensitize G361 melanoma cells to cisplatin. Inhibition of melanoma inhibitor of apoptosis protein mRNA and protein expression were measured by real-time polymerase chain reaction and immunoblotting. Cell viability and apoptosis were quantitated by colorimetric viability assays and by annexin V staining, respectively. Oligonucleotide M706 was identified as the most efficient antisense sequence which downregulated melanoma inhibitor of apoptosis protein mRNA and protein levels in G361 cells by 68 and 78%, respectively. The specificity of target downregulation was confirmed using scrambled sequence control oligonucleotides that only marginally decreased melanoma inhibitor of apoptosis protein expression. Whereas downregulation of melanoma inhibitor of apoptosis protein moderately inhibited cell growth by 26%, in combination with cisplatin, this resulted in a supra-additive effect with almost 57% reduction in G361 cell viability compared with cisplatin alone (17%) (P<0.05). Cell death was mainly due to apoptosis as demonstrated by a 3- to 4-fold increase in annexin V-positive cells and typical morphological changes compared with controls. In summary, we describe a new antisense oligonucleotide that efficiently downregulates melanoma inhibitor of apoptosis protein expression and sensitizes melanoma cells to cisplatin.

The small-molecule immune response modifier imiquimod – its mode of action and clinical use in the treatment of skin cancer

Due to its good clinical efficacy against malignant skin tumours, the topical immune response modifier, imiquimod, has attracted much interest among researchers and clinicians alike. Imiquimod exerts its antitumoural effect, at least in part, through agonistic stimulation of TLR-7 and TLR-8 on dendritic cells, followed by NF-kappaB-dependent secretion of a multitude of pro-inflammatory cytokines. The net result of this pro-inflammatory activity is a profound tumour-directed cellular immune response. Recent research has revealed an additional mode of action inasmuch as imiquimod interferes with adenosine receptor signalling, even in TLR-7- and TLR-8-negative cells, thereby presumably augmenting inflammatory signalling cascades. Moreover, at higher concentrations imiquimod also exerts direct proapoptotic activity against tumour cells. This mode of action appears to be independent of membrane-bound death receptors but is mediated, at least in part, through Bcl-2-dependent release of mitochondrial cytochrome c and subsequent caspase activation. Overall, a combination of several complementary antitumoural modes of action appears to underlie the great utility of imiquimod for treating cutaneous tumours.

Human Malignant Melanomas Express Receptors for Luteinizing Hormone Releasing Hormone Allowing Targeted Therapy with Cytotoxic Luteinizing Hormone Releasing Hormone Analogue

Cytotoxic analogue of luteinizing hormone releasing hormone (LHRH), AN-207, binds with high affinity to LHRH receptors and can be targeted to tumors expressing these receptors. We investigated the expression of LHRH receptors in surgical specimens of human malignant melanoma and evaluated the effects of AN-207 in models of human melanoma. Human melanoma specimens derived from primary tumors or metastases were examined for LHRH receptor expression by immunohistochemistry. Binding assays, Western immunoblotting, and reverse transcription-PCR analyses were used to investigate LHRH receptors in MRI-H255 and MRI-H187 transplantable human melanoma tumor lines. Antitumor effects of AN-207 and its components were evaluated in vivo in nude mice bearing xenografts of either melanoma tumor line. All 19 human melanoma specimens examined showed positive staining for LHRH receptors. The mRNA for LHRH receptors, receptor protein and binding sites for LHRH were detected in both transplantable melanoma tumor lines. AN-207 significantly inhibited the growth of MRI-H255 and MRI-H187 xenografts in vivo, reducing tumor volume by 59.9% to 79.2% and tumor weight by 61.0% to 76.9% (all P < 0.05). The components of AN-207 (LH-RH analogue carrier and cytotoxic radical AN-201 as single drugs or as an unconjugated mixture) had no significant effects. Blockade of LHRH receptors by an excess of LHRH agonist Decapeptyl suppressed the effects of AN-207. LHRH receptors are expressed in a very high percentage of human malignant melanoma specimens and can be used for targeted chemotherapy with cytotoxic LHRH analogue AN-207.

[Malignant melanoma -- a medical students' viewpoint]

Malignant melanoma is a primarily cutaneous melanocytic tumour with increasing incidence responsible for 90 % of skin cancer mortality. Genetic predisposition has been identified as the most important risk factor, while UV is second in importance and can be avoided. New diagnostic methods include sentinel lymph node biopsy and the detection of tumour markers in blood. Furthermore, malignant melanoma shows an extraordinary resistance to therapy; at present the only cure lies in early excision of the primary tumour. Thus early recognition is of utmost importance. Experimental approaches, such as dendritic cell vaccination, have shown some effectiveness which must be confirmed in multicenter, randomised trials.

The role of biological response modifiers in malignant melanoma

This article reviews the existing data in an attempt to address the role of biological response modifiers (IFN-alpha and IL-2) in the management of melanoma. Eight prospective controlled Phase III trials evaluating IFN-alpha therapy are discussed. As the results from these trials have been heterogeneous and inconsistent, the role of IFN-alpha in the adjuvant treatment of stage II and III melanoma patients remains to be defined. IL-2 possesses modest antitumour activity in melanoma yielding objective response in approximately 15% of patients. Many toxic effects are induced by high-dose IL-2 therapy. Combinations of chemotherapy and biological response modifiers and their impact on tumour response and survival are discussed.

Death receptor-independent apoptosis in malignant melanoma induced by the small-molecule immune response modifier imiquimod

Bypassing molecular mechanisms of apoptosis deficiency may be of great utility for the successful treatment of malignant tumors. We have discovered that imiquimod, a small-molecule immunomodulator, exerts rather tumor-selective direct pro-apoptotic activity in vivo and in vitro towards cutaneous metastases of malignant melanoma, an aggressive skin tumor. This pro-apoptotic activity was not detectable with resiquimod, a closely related structural analogue whose pro-inflammatory activity is even greater than that of imiquimod. Unresponsiveness of some melanoma metastases to imiquimod in vivo corresponded to resistance towards imiquimod-induced apoptosis in vivo and in vitro. At the molecular level, the pro-apoptotic activity of imiquimod was independent of membrane-bound death receptors, but depended on Bcl-2 expression as demonstrated by overexpression of Bcl-2 in melanoma cells. Imiquimod is the first topical compound with the potential to bypass molecular mechanisms of apoptosis deficiency, a concept that may be relevant for other tumors as well.

Induction of apoptosis and/or necrosis following exposure to antitumour agents in a melanoma cell line, probably through modulation of Bcl-2 family proteins

Malignant melanoma cells have been reported to be highly resistant to chemotherapeutic agents. To gain insight into the molecular mechanisms underlying chemotherapeutic drug resistance, we examined the role of the Bcl-2 family members Bcl-2 and Bax in cell death in the melanoma cell line G361 following stimulation with cisplatin (CDDP) or dacarbazine (DTIC). Trypan blue dye exclusion showed that both CDDP and DTIC induced death of G361 cells. Apoptotic and necrotic cell death could be distinguished by flow cytometry using combined staining with annexin V and 7-amino-actinomycin D (7-AAD). CDDP-induced cell death at a low concentration (0.6 micro g/ml) was mainly due to apoptosis (annexin V+/7-AAD-), while a mixture of apoptosis and secondary necrosis (annexin V+/7-AAD+) was found at a high concentration (6 micro g/ml). DTIC at the concentrations used induced only apoptosis. CDDP-induced apoptosis and secondary necrosis were accompanied by activation of caspase-3 and modulation of Bcl-2 family members Bcl-2 and Bax. On Western blotting Bax was seen to be upregulated with concomitant downregulation of Bcl-2. Flow cytometry, which enables measurement of protein at the single-cell level, revealed that Bcl-2+/Bax- cells were decreased, with a slight concomitant rise in Bcl-2-/Bax+ cells on stimulation with CDDP. These findings suggest that the chemotherapeutic agents CDDP and DTIC induce apoptosis and/or secondary necrosis depending on dose, probably involving the modulation of Bcl-2 family proteins.

Exposure of melanoma cells to dacarbazine results in enhanced tumor growth and metastasis in vivo

PURPOSE

In recent years, the incidence of cutaneous melanoma has increased more than that of any other cancer. Dacarbazine is considered the gold standard for treatment, having a response rate of 15% to 20%, but most responses are not sustained. Previously, we have shown that short exposure of primary cutaneous melanoma cells to dacarbazine resulted in the upregulation of interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The purpose of the present study was to determine how long-term exposure of melanoma cells to dacarbazine would affect their tumorigenic and metastatic potential in vivo.

MATERIALS AND METHODS

The primary cutaneous melanoma cell lines SB2 and MeWo were repeatedly exposed in vitro to increasing concentrations of dacarbazine, and dacarbazine-resistant cell lines SB2-D and MeWo-D were selected and examined for their ability to grow and metastasize in nude mice.

RESULTS

The dacarbazine-resistant cell lines SB2-D and MeWo-D exhibited increased tumor growth and metastatic behavior in vivo. This increase could be explained by the activation of RAF, MEK, and ERK, which led to the upregulation of IL-8 and VEGF. More IL-8, VEGF, matrix metalloproteinase-2 (MMP-2), and microvessel density (CD-31) were found in tumors produced by SB2-D and MeWo-D in vivo than in those produced by their parental counterparts. No mutations were observed in BRAF.

CONCLUSION

Our results have significant clinical implications. Treatment of melanoma patients with dacarbazine could select for a more aggressive melanoma phenotype. We propose that combination treatment with anti-VEGF/IL-8 or MEK inhibitors may potentiate the therapeutic effects of dacarbazine.

Constitutive activation of the Ras-Raf signaling pathway in metastatic melanoma is associated with poor prognosis

Background

Genes of the Raf family encode kinases that are regulated by Ras and mediate cellular responses to growth signals. Recently, it was shown that activating mutations of BRaf are found with high frequency in human melanomas. The Ras family member most often mutated in melanoma is NRas.

Methods

The constitutive activation of the Ras/Raf signaling pathway suggests an impact on the clinical course of the tumor. To address this notion, we analyzed tumor DNA from 114 primary cutaneous melanomas and of 86 metastatic lesions obtained from 174 patients for mutations in BRaf (exons 15 and 11) and NRas (exons 1 and 2) by direct sequencing of PCR products and correlated these results with the clinical course.

Results

In 57.5% of the tumors either BRaf or NRas were mutated with a higher incidence in metastatic (66.3%) than in primary lesions (50.9%). Although the majority of BRaf mutations affected codon 599, almost 15% of mutations at this position were different from the well-described exchange from valine to glutamic acid. These mutations (V599R and V599K) also displayed increased kinase and transforming activity. Surprisingly, the additional BRaf variants D593V, G465R and G465E showed a complete loss of activity in the in vitro kinase assay; however, cells overexpressing these mutants displayed increased Erk phosphorylation. The correlation of mutational status and clinical course revealed that the presence of BRaf/NRas mutations in primary tumors did not negatively impact progression free or overall survival. In contrast, however, for metastatic lesions the presence of BRAF/NRAS mutations was associated with a significantly poorer prognosis, i.e. a shortened survival.

Conclusion

We demonstrate a high – albeit lower than initially anticipated – frequency of activating BRaf mutations in melanoma in the largest series of directly analyzed tumors reported to date. Notably, the clinical course of patients harboring activating BRaf mutations in metastatic melanoma was significantly affected by the presence of a constitutive BRaf activation in these.

Systemic chemotherapy in the treatment of malignant melanoma

Different postsurgical therapies are used for the treatment of metastatic melanoma. This article reviews the use of chemotherapeutic agents in the treatment of patients with metastatic malignant melanoma. A variety of single chemotherapy agents have been evaluated, although the most widely used chemotherapeutic in the treatment of metastatic melanoma is dacarbazine. In order to improve the rate and duration of responses, combination chemotherapy was developed. The most common combined chemotherapy regimens used as standard for the treatment of metastatic melanoma are Dartmouth regimen, CVD (cisplatin + vinblastine + dacarbazine) and BOLD (bleomycin + vincristine + lomustine + dacarbazine). However, Phase III trials have failed to demonstrate a significant benefit in survival in patients treated with polychemotherapy compared to those treated with dacarbazine alone. The use of classical systemic chemotherapy still has a role in the treatment of patients with metastatic melanoma. Immunotherapy and biochemotherapy have no additional advantage over chemotherapy.

The biology of gonadotropin hormone-releasing hormone: role in the control of tumor growth and progression in humans

It is now well known that different forms of GnRH coexist in the same vertebrate species. In humans, two forms of GnRH have been identified so far. The first form corresponds to the hypophysiotropic decapeptide, and is now called GnRH-I. The second form has been initially identified in the chicken brain, and it is referred to as GnRH-II. GnRH-I binds to and activates specific receptors, belonging to the 7 transmembrane (7TM) domain superfamily, present on pituitary gonadotropes. These receptors (type I GnRH receptors) are coupled to the Gq/11/PLC intracellular signalling pathway. A receptor specific for GnRH-II (type II GnRH receptor) has been identified in non-mammalian vertebrates as well as in primates, but not yet in humans. In the last 10-15 years experimental evidence has been accumulated indicating that GnRH-I is expressed, together with its receptors, in tumors of the reproductive tract (prostate, breast, ovary, and endometrium). In these hormone-related tumors, activation of type I GnRH receptors consistently decreases cell proliferation, mainly by interfering with the mitogenic activity of stimulatory growth factors (e.g., EGF, IGF). Recent data seem to suggest that GnRH-I might also reduce the migratory and invasive capacity of cancer cells, possibly by affecting the expression and/or activity of cell adhesion molecules and of enzymes involved in the remodelling of the extracellular matrix. These observations point to GnRH-I as an autocrine negative regulatory factor on tumor growth progression and metastatization. Extensive research has been performed to clarify the molecular mechanisms underlying the peculiar antitumor activity of GnRH-I. Type I GnRH receptors in hormone-related tumors correspond to those present at the pituitary level in terms of cDNA nucleotide sequence and protein molecular weight, but do not share the same pharmacological profile in terms of binding affinity for the different synthetic GnRH-I analogs. Moreover, the classical intracellular signalling pathway mediating the stimulatory activity of the decapeptide on gonadotropin synthesis and secretion is not involved in its inhibitory activity on hormone-related tumor growth. In these tumors, type I GnRH receptors are coupled to the Gi-cAMP, rather than the Gq/11-PLC, signal transduction pathway. Recently, we have reported that GnRH-I and type I GnRH receptors are expressed also in tumors not related to the reproductive system, such as melanoma. Also in melanoma cells, GnRH-I behaves as a negative regulator of tumor growth and progression. Interestingly, the biochemical and pharmacological profiles of type I GnRH receptors in melanoma seem to correspond to those of the receptors at pituitary level. The data so far reported on the expression and on the possible functions of GnRH-II in humans are still scanty. The decapeptide has been identified, together with a 'putative' type II GnRH receptor, both in the central nervous system and in peripheral structures, such as tissues of the reproductive tract (both normal and tumoral). The specific biological functions of GnRH-II in humans are presently under investigation.

Pharmacogenetic candidate genes for melanoma

The incidence of melanoma is rising at an alarming rate and has become an important public health concern. If detected early, melanoma carries an excellent prognosis after appropriate surgical resection. Unfortunately, advanced melanoma has a poor prognosis and is notoriously resistant to radiation and chemotherapy. The relative resistance of melanoma to a wide-range of chemotherapeutic agents and high toxicity of current therapies has prompted a search for effective alternative treatments that would improve prognosis and limit side effects. Advances in molecular genetics are revealing in increasing detail the mechanisms responsible for the development of melanoma. Hopefully, elucidation of these pathways will provide a means of screening high-risk individuals and allow new drug development for prevention and treatment by identification of specific pharmacological targets. This review will summarize the genetics of melanoma with the goal of providing insights into potential pharmacogenetic candidate genes.

Treosulfan and gemcitabine in metastatic uveal melanoma patients: results of a multicenter feasibility study

No effective treatment currently exists for metastatic uveal melanoma. However, recent results obtained by an ATP-based tumor chemosensitivity assay have shown consistent activity of treosulfan+gemcitabine in up to 80% of tumor specimens tested. In this study we describe the first clinical results observed with this drug combination at different European centers in patients with metastatic uveal melanoma. Clinical case series of patients with metastatic uveal melanoma were treated with treosulfan+gemcitabine at seven different centers. Fourteen patients, 13 previously untreated and one pretreated with chemoimmunotherapy, were included in the study. Patients received treosulfan+gemcitabine in four different dose regimens. The response rates, progression-free and overall survival, and toxicity were evaluated. The analysis of 14 patients revealed one complete response, three partial responses and a stable disease in eight cases. The objective response rate was 28.6%, the median overall survival was 61 weeks [95% confidence interval (CI) 54-133 weeks], the progression-free survival was 28.5 weeks (95% CI 13-62 weeks) and the 1-year survival rate was 80%. The drugs were well tolerated. The most common side-effects were leuko- and thrombocytopenia. These preliminary results suggest potential therapeutic benefit of treosulfan+gemcitabine treatment in metastatic uveal melanoma and warrant further controlled studies.

Bleomycin, vincristine, lomustine and dacarbazine (BOLD) in combination with recombinant interferon alpha-2b for metastatic uveal melanoma

This EORTC multicentre study analysed the efficacy and tolerability in patients with metastatic uveal melanoma of BOLD chemotherapy in combination with recombinant interferon alpha-2b. The dose of bleomycin was 15 mg on days 2 and 5, of vincristine 1 mg/m(2) on days 1 and 4, of lomustine 80 mg on day 1, and of dacarbazine (DTIC) 200 mg/m(2) on days 1-5, given every 4 weeks for a minimum of two cycles. Subcutaneous (s.c.) interferon alpha-2b at a dose of 3 x 10(6) IU was initiated on day 8 of the first cycle, and continued at a dose of 6 x 10(6) IU three times per week after 6 weeks. A median of two cycles were administered to 24 patients (median age 60.5 years). None achieved an objective response (0%; 95% Confidence Interval (CI): 0-14), 2 (8.3%) remained stable, 20 showed progression, and 2 (8.3%) were invaluable. The median progression-free survival was 1.9 months (95% CI: 1.8-3.4) and overall survival 10.6 months (95% CI: 6.9-16.4). Overall survival improved with increasingly favourable pretreatment characteristics (median, 14.7 versus 6.9 versus 6.0 months for Helsinki University Central Hospital (HUCH) Working Formulation stages IVBa, IVBb and IVBc, respectively; P=0.018). Grade 3 alopecia and neurotoxicity occurred in 13% of the patients. This multicentre study did not confirm earlier reports that BOLD with human leucocyte or recombinant interferon would induce at least 15% objective responses in metastatic uveal melanoma.

Cyclooxygenase-2 inhibition improves macrophage function in melanoma and increases the antineoplastic activity of interferon gamma

BACKGROUND

Melanoma inhibits macrophage tumoricidal activity and increases the expression of cyclooxygenase-2 (COX-2). In this study, we sought to determine whether inhibition of COX-2 could restore macrophage function and hence maximize the antitumor activity of the immune stimulant interferon gamma (IFN gamma).

METHODS

Peritoneal macrophages were exposed to B16 melanoma-conditioned medium for 24 hours with or without the COX-2 inhibitor NS-398 and then were stimulated with lipopolysaccharide and IFN gamma. Cytotoxic activity, nitrite production, and cytokine production by the stimulated macrophages were measured. In addition, B16 melanoma cells were implanted intradermally into mice treated with IFN gamma (14,000 U on alternate days) alone or with a combination of IFN gamma and a COX-2 inhibitor (NS-398 or nimesulide). Mice were assessed for tumor growth and survival.

RESULTS

Macrophage cytotoxicity and nitrite production were significantly suppressed by melanoma-conditioned medium (P <.01). This was prevented by 200 micro M of NS-398 (P <.05). In vivo, combined treatment with IFN gamma and a COX-2 inhibitor caused a significant inhibition of tumor growth (P <.01) and improved survival (P =.02) compared with controls.

CONCLUSIONS

COX-2 inhibition reversed melanoma-induced suppression of macrophage function, and combined treatment of IFN gamma plus a COX-2 inhibitor was maximally effective in reducing tumor growth and improving survival.

Involvement of tumor cell integrin alpha v beta 3 in hematogenous metastasis of human melanoma cells

Early metastasis is the primary cause of death in melanoma patients. The adhesion receptor integrin alpha v beta 3 contributes to tumor cell functions that are potentially involved in melanoma growth and metastasis. We tested whether integrin alpha v beta 3 supports metastasis of human melanoma cells when injected into the bloodstream of immune deficient mice. Comparing variants of the same melanoma cell type that expressed either alpha v beta 3, alpha IIb beta 3 or no beta 3 integrin, we found that only alpha v beta 3 strongly supported metastasis. Inhibition of tumor cell alpha v beta 3 function reduced melanoma metastasis significantly and prolonged animal survival. To understand mechanisms that allow alpha v beta 3, but not alpha IIb beta 3 to support melanoma metastasis, we analyzed proteolytic and migratory activities of the melanoma cell variants. Melanoma cells expressing alpha v beta 3, but not those expressing alpha IIb beta 3 or no beta 3 integrin, produced the active form of metalloproteinase MMP-2 and expressed elevated mRNA levels of MT1-MMP and TIMP-2. This indicates an association between alpha v beta 3 expression and protease processing. Furthermore, alpha v beta 3 expression was required for efficient melanoma cell migration toward the matrix proteins fibronectin and vitronectin. The results suggest that expression of integrin alpha v beta 3 promotes the metastatic phenotype in human melanoma by supporting specific adhesive, invasive and migratory properties of the tumor cells and that the related integrin alpha IIb beta 3 cannot substitute for alpha v beta 3 in this respect.

Locally expressed LHRH receptors mediate the oncostatic and antimetastatic activity of LHRH agonists on melanoma cells

Malignant melanoma is a tumor known for its uncontrollable growth and aggressive metastatic behavior. The mean survival time for patients with a metastatic melanoma is estimated to be less than 6 months, tumor cells being refractory to the conventional chemotherapy. A better understanding of the mechanisms regulating melanoma growth and progression might help increase the number of therapeutic options for this pathology. In this paper, we have shown that LHRH receptors are present in the BLM melanoma cell line, both at mRNA and at protein level; a potent LHRH agonist (LHRH-A; Zoladex) binds to these receptors with high affinity. BLM cells also express the mRNA for LHRH, indicating the presence of an autocrine LHRH-based system in melanoma cells. The treatment of BLM cells with LHRH-A dose-dependently inhibited cell proliferation; this effect was found to be specific because it was completely abrogated by the simultaneous treatment of the cells with a LHRH antagonist. Similar observations could be obtained in another melanoma cell line (Me15392). The activation of LHRH receptors, by means of LHRH-A, also reduced the ability of melanoma cells to invade a reconstituted basement membrane (Matrigel) and to migrate through a Boyden's chamber in response to a chemotactic stimulus. These data represent the first report that 1) LHRH and LHRH receptors are expressed in melanoma tumor cells; and 2) the activation of tumor LHRH receptors reduces both the proliferation and the metastatic potential of melanoma cells. It is suggested that the expression of LHRH receptors might represent a new diagnostic marker for the detection and progression of melanoma. These receptors might also be considered as a possible molecular target for a hormone-based therapeutic approach to this tumor.

Comparison of the ex vivo chemosensitivity of uveal and cutaneous melanoma

Cutaneous and uveal melanoma both have a poor prognosis and chemotherapy is usually unsuccessful. We have previously reported the activity of a number of cytotoxic agents against metastatic cutaneous and primary choroidal uveal melanoma using an ex vivo adenosine triphosphate (ATP)-based chemosensitivity assay (ATP-TCA). In this study we compare the results obtained with the two types of melanoma. Cutaneous melanoma deposits in skin and lymph nodes (n = 58) and choroidal melanomas (n = 77) were tested using the ATP-TCA. Analysis of the data based on an arbitrary threshold for sensitivity shows that both types of melanoma exhibit heterogeneity of sensitivity to all the agents and combinations tested. With all the single agents except gemcitabine, cutaneous melanomas showed greater sensitivity in the assay, though this did not achieve statistical significance. This was also true with the drug combinations, with the exception of treosulfan + gemcitabine, which had similar activity in each type of melanoma. Of all the single agents tested, doxorubicin (47% of specimens classed as sensitive), vinorelbine (43%), treosulfan (41%) and paclitaxel (33%) showed the greatest activity with cutaneous melanoma. In the uveal melanoma samples, mitoxantrone (33%), gemcitabine (22%) and treosulfan (21%) showed the greatest activity. In contrast to the cutaneous melanomas, 13% of the uveal melanomas were sensitive to paclitaxel, 4% were sensitive to doxorubicin and 11% were found to be sensitive to vinorelbine. Both tumour types showed greater sensitivity to combinations of cytotoxic agents. The combination of treosulfan + gemcitabine was universally effective, with 72% of cutaneous melanomas and 80% of uveal melanomas exhibiting activity at the level selected to indicate sensitivity in the assay, though this will not necessarily indicate a similar level of clinical sensitivity.