Tumor Immunotherapy in Melanoma

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.     

Mcl-1 antisense therapy chemosensitizes human melanoma in a SCID mouse xenotransplantation model

It is well established that high expression of the antiapoptotic Bcl-2 family proteins Bcl-2 and Bcl-xL can significantly contribute to chemoresistance in a number of human malignancies. Much less is known about the role the more recently described Bcl-2 family member Mcl-1 might play in tumor biology and resistance to chemotherapy. Using an antisense strategy, we here address this issue in melanoma, a paradigm of a treatment-resistant malignancy. After in vitro proof of principle supporting an antisense mechanism of action with specific reduction of Mcl-1 protein as a consequence of nuclear uptake of the Mcl-1 antisense oligonucleotides employed, antisense and universal control oligonucleotides were administered systemically in combination with dacarbazine in a human melanoma SCID mouse xenotransplantation model. Dacarbazine, available now for more than three decades, still remains the most active single agent for treatment of advanced melanoma. Mcl-1 antisense oligonucleotides specifically reduced target protein expression as well as the apoptotic threshold of melanoma xenotransplants. Combined Mcl-1 antisense oligonucleotide plus dacarbazine treatment resulted in enhanced tumor cell apoptosis and led to a significantly reduced mean tumor weight (mean 0.16 g, 95% confidence interval 0.08-0.26) compared to the tumor weight in universal control oligonucleotide plus dacarbazine treated animals (mean 0.35 g, 95% confidence interval 0.2-0.44) or saline plus dacarbazine treated animals (mean 0.39 g, 95% confidence interval 0.25-0.53). We thus show that Mcl-1 is an important factor contributing to the chemoresistance of human melanoma in vivo. Antisense therapy against the Mcl-1 gene product, possibly in combination with antisense strategies targeting other antiapoptotic Bcl-2 family members, appears to be a rational and promising approach to help overcome treatment resistance of malignant melanoma.     

Comparison of a treatment strategy combining CCI-779 plus DTIC versus DTIC monotreatment in human melanoma in SCID mice

This study compares the antineoplastic potential of a novel treatment strategy combining cell cycle inhibitor-779 (CCI-779) plus dacarbazine (DTIC) versus DTIC monotreatment, the current chemotherapeutic mainstay in combating metastatic melanoma. A controlled four-group parallel study design comprising 24-40 mice per tumor cell line was used in a severe combined immunodeficiency (SCID)-mouse xenotransplantation model. SCID mice were injected with 518A2, Mel-JUSO, or 607B human melanoma cells. After they developed tumors, mice received daily CCI-779 or solvent over 14 days. From treatment day 4-8 mice were additionally injected with DTIC or saline. Treatment with CCI-779 plus DTIC was superior to single agent DTIC in two out of three cell lines (P<0.05). The tumor weight reduction was 44+/-17 and 61+/-6% compared with DTIC monotreatment in Mel-JUSO and 607B melanomas, respectively (P<0.05). In contrast, in 518A2 xenotransplants, CCI-779 plus DTIC treatment was as effective as DTIC monotreatment. CCI-779 monotherapy exerted no statistically significant antitumor effect. Collectively, these data indicate that CCI-779 has the potential to increase the chemotherapeutic efficacy, as the combination of CCI-779 plus DTIC proved to be more efficacious compared to DTIC monotherapy in two out of three melanoma cell lines in vivo.     

荷载白介素24的溶瘤腺病毒联合达卡巴嗪对裸鼠黑素瘤的抑制作用

目的 研究荷载白介素24（IL-24）的溶瘤腺病毒ZD55-IL-24联合达卡巴嗪抑制裸鼠黑素瘤的作用。方法 建立裸鼠恶性黑素瘤A375细胞移植瘤模型后,分别给予ZD55-IL-24联合达卡巴嗪、ZD55-IL-24、达卡巴嗪、磷酸盐缓冲液（PBS）干预。Western印迹法检测A375细胞移植瘤组织IL-24、E1A蛋白表达。测量裸鼠肿瘤生长体积。结果 Western印迹结果表明,ZD55-IL-24联合达卡巴嗪作用的裸鼠黑素瘤高效表达IL-24、E1A蛋白。接种30 d后,ZD55-IL-24联合达卡巴嗪组肿瘤平均体积为（2346.5 ± 576.0） mm3,ZD55-IL-24组为（4141.6 ± 1348.2） mm3,达卡巴嗪组为（5230.1 ± 922.8） mm3,PBS组为（7135.1 ± 1002.3）mm3,ZD55-IL-24联合达卡巴嗪组与各组之间差异均有统计学意义（P ＜ 0.05）。结论 荷载IL-24基因的溶瘤腺病毒ZD55-IL-24联合达卡巴嗪有抑制黑素瘤增殖的作用。     

Synergistic effects of hyperthermia and peplomycin against human malignant melanoma xenografts

Two types of human malignant melanoma were treated either with peplomycin alone, hyperthermia alone, or a combination of peplomycin and hyperthermia. The antitumor effect of combination therapy was evaluated by tumor growth curves, maximal suppression rate, and histopathology. A marked antitumor effect of combination therapy with peplomycin (5 mg/kg) and hyperthermia (43°C, 30 min) was obtained for both types of melanoma. Histopathologic findings revealed advanced central necrosis and pyknotic nuclei in the tumor cells. Although peplomycin alone (20 mg/kg, 6 times) had no antitumor effect on C24 melanoma, the peplomycin (5 mg/kg, 6 times) + heat group showed complete inhibition of the tumor growth. These results suggest that hyperthermia enhances the antitumor effect of peplomycin even against peplomycin-resistant tumor cells.     

Fibroblast growth factor receptors as therapeutic targets in human melanoma: synergism with BRAF inhibition

Cutaneous melanoma is a tumor with rising incidence and a very poor prognosis at the disseminated stage. Melanomas are characterized by frequent mutations in BRAF and also by overexpression of fibroblast growth factor 2 (FGF2), offering opportunities for therapeutic intervention. We investigated inhibition of FGF signaling and its combination with dacarbazine or BRAF inhibitors as an antitumor strategy in melanoma. The majority of melanoma cell lines displayed overexpression of FGF2 but also FGF5 and FGF18 together with different isoforms of FGF receptors (FGFRs) 1-4. Blockade of FGF signals with dominant-negative receptor constructs (dnFGFR1, 3, or 4) or small-molecule inhibitors (SU5402 and PD166866) reduced melanoma cell proliferation, colony formation, as well as anchorage-independent growth, and increased apoptosis. DnFGFR constructs also significantly inhibited tumor growth in vivo. Combination of FGF inhibitors with dacarbazine showed additive or antagonistic effects, whereas synergistic drug interaction was observed when combining FGFR inhibition with the multikinase/BRAF inhibitor sorafenib or the V600E mutant-specific BRAF inhibitor RG7204. In conclusion, FGFR inhibition has antitumor effects against melanoma cells in vitro and in vivo. Combination with BRAF inhibition offers a potential for synergistic antimelanoma effects and represents a promising therapeutic strategy against advanced melanoma.     

Release of vascular endothelial growth factor from a human melanoma cell line, WM35, is induced by hypoxia but not ultraviolet radiation and is potentiated by activated Ras mutation

Angiogenesis, the formation of blood vessels, is a major factor influencing tumor growth and metastatic capacity, and VEGF is the prototype angiogenic factor. VEGF expression is also found in the dermis and tumor stroma during the course of melanoma progression. Various oncogenes such as c-Src, v-Raf, and Ras, and multiple environmental stimuli, including hypoxia and ultraviolet radiation (UVR), can regulate VEGF expression under certain conditions. We have constructed several cell lines from a radial growth phase, primary human melanoma cell line, WM35. We have stably transfected WM35 cells with mutant activated H-ras, N-ras, dominant negative p53, or empty vector. In this report, we determined how VEGF expression and release from these melanoma cell lines were affected by the following important factors associated with melanoma initiation and progression: hypoxia, UVR, activated Ras, dominant negative p53, and culture conditions mimicking radial growth phase melanoma (monolayer culture) and vertical growth phase melanoma (spheroid culture). We found that hypoxia, but not UVR, up-regulates VEGF mRNA expression and protein release in these melanoma cells. In addition, activated Ras and dominant negative p53 enhances the hypoxia-induced VEGF protein release. We propose that hypoxia-induced VEGF release promotes tumor progression, especially in melanomas with Ras or p53 mutations.     

Improving chemotherapeutic drug penetration in melanoma by imatinib mesylate

BACKGROUND: Imatinib mesylate has specific activity in inhibiting select tyrosine kinase receptors, including platelet-derived growth factor receptors (PDGFRs) and c-kit. In general, melanomas widely express PDGFR and c-kit, and their in vivo resistance to chemotherapy is attributable to high tumor interstitial fluid pressure (IFP). Recent studies have suggested that PDGFR-beta inhibition reduces tumor IFP, and thus increases the uptake of concomitantly administered drugs. OBJECTIVE: The present study was designed to investigate the potential of imatinib mesylate as a therapy for melanoma or as an adjuvant to chemotherapeutics. METHODS: Using in vivo mouse models, the effect of imatinib mesylate on the growth of melanoma with or without dacarbazine was studied. RESULTS: Imatinib mesylate enhanced the antitumor effect of dacarbazine on in vivo growth and lung metastases of melanoma cells, although treatment with only imatinib mesylate had no effect. We could detect perivascular expression of PDGF beta-receptor in melanoma tumors. Interestingly, dacarbazine uptake in melanoma was more than three-times increased by treatment with imatinib mesylate, while its uptake in serum or bone marrow was not affected by imatinib mesylate. CONCLUSIONS: These data suggest interference with PDGF receptors, or their ligands, as a novel strategy to increase drug uptake and therapeutic effectiveness of chemotherapy for melanoma.     

A model of human melanoma in cyclosporine-immunosuppressed rats

A human malignant melanoma maintained in athymic nude mice has been successfully implanted and grown in cyclosporine (Cys)-immunosuppressed Lewis rats. Suspended melanoma cells (10(6)) or solid tumor sections measuring 2-4 mm in diameter were implanted s.c. in rats receiving parenteral Cys doses of 15-50 mg/kg each day for 1 week, and 3 times per week thereafter. Eighty-five percent of solid tumor sections implanted in animals receiving 25 mg/kg resulted in tumor growth, whereas no tumors grew from cell suspension injection sites. The average maximum tumor growth rate was 2 cm3/day, with a doubling time of 8 days. Tumors retained pretransplant gross and microscopic morphology, karyotype, and labeling index. Possible advantages of this model over the athymic nude mouse include greater longevity, larger animal and tumor size, and less stringent aseptic environmental requirements. This model may prove useful for further study of the pathophysiology of melanoma and for testing of new antimelanoma therapies.     

Thalidomide enhances the anti-tumor activity of standard chemotherapy in a human melanoma xenotransplatation model

It has been demonstrated that thalidomide's anti-angiogenic properties result in clear anti-tumor activity in a number of human malignancies. We studied thalidomide in a human melanoma severe combined immunodeficiency mouse xenotransplantation model. Thalidomide as a single agent showed a significant tumor reduction of 46% compared with the control group. Thalidomide combined with dacarbazine treatment markedly enhanced the anti-tumor effect of chemotherapy and showed a significant tumor reduction relative to the dacarbazine-only group (61%) and even more tumor reduction (74%) compared with the control group. We also measured clearly reduced levels of tumor necrosis factor-alpha in the thalidomide-treated group. A significantly lower microvessel density was encountered in the thalidomide treatment groups (thalidomide alone or combined with DTIC), underscoring the anti-angiogenic effect of thalidomide as a single agent as well as in combination with chemotherapy in this model. In line with these results, we observed a nearly 3-fold increase of apoptosis for the combination of thalidomide and DTIC compared with the rate of apoptotic cells in DTIC-only-treated melanoma xenotransplants. These data underline the rationale for combining dacarbazine--a cytotoxic agent--and thalidomide--an anti-angiogenic cytostatic agent--as a promising strategy for the treatment of melanoma.     

Effects of betulinic acid alone and in combination with irradiation in human melanoma cells

Recently, betulinic acid was identified as a highly selective inhibitor of human melanoma growth and was reported to induce apoptosis in these cells. We have investigated the growth-inhibitory properties of this compound alone and in combination with ionizing radiation in a panel of established human melanoma cell lines as well as in normal human melanocytes. Betulinic acid strongly and consistently suppressed the growth and colony-forming ability of all human melanoma cell lines investigated. In combination with ionizing radiation the effect of betulinic acid on growth inhibition was additive in colony-forming assays. Betulinic acid also induced apoptosis in human melanoma cells as demonstrated by Annexin V binding and by the emergence of cells with apoptotic morphology. The growth-inhibitory action of betulinic acid was more pronounced in human melanoma cell lines than in normal human melanocytes. Notably, despite the induction of apoptosis, analysis of the expression of Bcl-2 family members in betulinic-acid-treated cells revealed that expression of the anti-apoptotic protein Mcl-1 was induced. Furthermore, the antiproliferative action of betulinic acid seemed to be independent of the p53 status. The properties of betulinic acid make it an interesting candidate, not only as a single agent but also in combination with radiotherapy. We conclude that the strictly additive mode of growth inhibition in combination with irradiation suggests that the two treatment modalities may function by inducing different cell death pathways or by affecting different target cell populations.     

Therapie des malignen Melanoms im Stadium der Fernmetastasierung

Treatment of melanoma in the stage of distant metastasis aims on palliation and achievement of durable tumor remission with prolongation of survival. As long as metastasis is confined to one organ system and is removable, surgery remains the treatment of first choice. In limited metastasis radiotherapy may likewise be indicated, particularly in bone and brain metastasis. More extensive metastasis should be treated by chemotherapy or chemoimmunotherapy. Monochemotherapy with dacarbazine, temozolomide, fotemustine and vindesine or its combinations with interferon-alpha are currently preferred. Polychemotherapy or its combinations with interferon-alpha and interleukin-2 are suitable to produce higher response rates but failed to prolong survival. As these treatments are associated with substantially higher toxicity they have been widely abandoned. Combined treatment with dacarbazine and interferon-alpha obtain tumor responses or stable disease in 40-50% and objective tumor remissions in 15-20% of patients. Effective cancer vaccination strategies and blockade of melanoma specific target molecules are currently developed as new treatment options.     

Ambulatory treatment of metastatic melanoma associating subcutaneous dacarbazine, interferon α and interleukin-2

Background Recent studies have shown that interleukin–2 (IL2) is less toxic when administered subcutaneously than intravenously. Moreover interferon α and Dacarbazine could increase the efficiency of IL2. Patients and methods Nineteen ambulatory patients with metastatic melanoma (1 stage 111 and 18 stage IV) were treated with an association of dacarbazine 400 mg/m², interferon α_2a (Roferon) 9 × l0⁶ IU 3 times per week administered subcutaneously and recombinant interleukin-2 (IL–2) (Eurocetus) 3 × 10⁶ IU five days per week for two weeks per month subcutaneously. The treatment consisted of 2 induction cures separated by a one-month interval followed by evaluation studies. Results At the end of the induction phase. 2 complete and 3 partial responses (response rate 26.2%) were observed. These responses were obtained in patients with sinus (1 case), skin (3 cases), lymph node (2 cases), bone (1 case) and liver (I case) targets. The mean response period was 10 months for the 2 complete responses. No patients had grade 4 toxicity, and treatment was stopped for only one patient. Painful subcutaneous nodules frequently (23%) formed at the injection site. Conclusion The association of subcutaneously administered dacarbazine, interferon α and IL2 would thus seem of interest for the treatment of metastatic melanoma. Moreover, toxicity is tolerable and compatible with ambulatory treatment ensuring the patient a decent quality of life.     

Expression of activated N-ras in a primary melanoma cell line counteracts growth inhibition by transforming growth factor-beta

One critical factor in melanoma progression is the change from radial growth phase to vertical growth phase. We previously showed a high incidence of ras mutations in progressing but not early human melanomas. We also found that stable expression of activated Ras in a primary human melanoma cell line (WM35) led to enhanced proliferation, anchorage-independent survival, migration and invasion in vitro and enhanced subcutaneous tumor formation in vivo, transforming the melanoma phenotype from the radial growth phase to the vertical growth phase. Inhibitory cytokines, especially transforming growth factor-beta, are important in homeostasis of normal human melanocytes. Proliferation of early melanoma cells can be inhibited by transforming growth factor-beta, whereas more aggressive stages lose this response. Using a transforming growth factor-beta activated luciferase reporter transiently transfected into WM35, WM35N-ras, and WM35H-ras (WM35 transfected with mutant N-ras or H-ras genes), we demonstrated significant decreases (p < 0. 04) in transforming growth factor-beta induced reporter expression in both ras transfected cell lines. Transforming growth factor-beta also induced significant decreases (p < 0.002) in the proportion of WM35 cells in S-phase of the cell cycle; this effect was not observed in WM35N-ras cells. Furthermore, we demonstrated that an important controlling factor in transforming growth factor-beta inhibition of cell cycle progression, the phosphorylation of the Rb protein, was altered in WM35N-ras; transforming growth factor-beta caused a marked relative increase in hypophosphorylated pRb in WM35 cells, but not in WM35N-ras. These data suggest that activated Ras plays an important part in melanoma progression from the radial growth phase to the vertical growth phase by counteracting inhibition by cytokines such as transforming growth factor-beta, thus providing a growth advantage.     

Chemoprevention of skin cancer in xeroderma pigmentosum.

Xeroderma pigmentosum is a rare recessive disease with sun sensitivity, increased freckling and defective DNA repair. Xeroderma pigmentosum patients have more than a 1000-fold increased risk of developing skin cancer including basal cell carcinoma, squamous cell carcinoma and melanoma. We studied chemoprevention of new skin cancers with oral retinoids in xeroderma pigmentosum patients who had multiple skin cancers. Xeroderma pigmentosum patients were cleared of all pre-existing tumors surgically and then treated with high dose (2 mg/kg/day) oral isotretinoin (13-cis retinoic acid, Accutane) for two years and then for one year off treatment. Patients were examined at regular intervals for new tumor formation and for side effects. Five xeroderma pigmentosum patients had a total of 121 basal or squamous cell carcinomas in 2 years before treatment and only 25 tumors during 2 years of treatment. The tumor frequency increased 8.5-fold after the drug was discontinued (New Engl J Med 318: 1633-1637, 1988). Toxicity (cutaneous, triglyceride, liver-function or skeletal abnormalities) prompted subsequent use of a low dose protocol. Patients were treated initially with 0.5 mg/kg/day oral isotretinoin and the dose was increased sequentially to 1.0 or 1.5 mg/kg/day. We found that toxicity was less with the lower doses. The lowest effective, least toxic dose varied among the xeroderma pigmentosum patients.     

阿维A对鼠B16黑素瘤的增殖抑制及诱导分化作用

目的 探讨阿维A对鼠B16黑素瘤移植瘤的增殖抑制及诱导分化可能的作用机制。方法 小鼠黑素瘤B16细胞接种C57BL/6J小鼠,观察阿维A及其联合顺铂对移植瘤生长状态的影响。应用HE染色观察移植瘤形态学改变;免疫组化法检测肿瘤组织中生存素、促细胞凋亡蛋白Fas及血管内皮生长因子（VEGF）的表达。结果 阿维A能显著抑制鼠B16黑素瘤的生长,各治疗组瘤重及瘤体积均低于阴性对照组（P < 0.05）。HE染色观察瘤组织：对照组瘤组织边界不清,细胞密集排列,异形性明显,治疗组瘤组织中心及边缘可见不同程度的大片状或灶性坏死。免疫组化结果显示：生存素和VEGF蛋白的表达在阿维A高剂量组及联合用药组的免疫组化评分分别为3.600 ± 0.966,2.100 ± 0.568和4.600 ± 0.966,2.400 ± 0.516,均低于对照组5.900 ± 1.370,6.100 ± 1.197（P < 0.01,P < 0.01）,Fas蛋白的表达均高于对照组（P < 0.01）,且各治疗组生存素的表达与Fas的表达呈负相关（rs = -0.77,P < 0.01）,与VEGF的表达成正相关（rs = 0.72,P < 0.01）。结论 阿维A能抑制鼠B16黑素瘤增殖,诱导其分化,作用机制可能与下调抑凋亡基因生存素、上调促凋亡基因Fas的表达及抑制VEGF的表达有关。     

Dermatologic toxicity from novel therapy using antimicrobial peptide LL‐37 in melanoma: A detailed examination of the clinicopathologic features

LL‐37 is a naturally occurring 37‐amino‐acid peptide that is part of the innate immune system in human skin. Preclinical studies have showed that intra‐tumoral injections of LL‐37 stimulate the innate immune system by activation of plasmacytoid dendritic cells, which mediate tumor destruction. LL‐37 intra‐tumoral injections have been utilized in a phase 1 clinical trial for melanoma patients with cutaneous metastases. We report dermatologic toxicity in a 63‐year‐old woman with stage IIIC melanoma of the right calf and inguinal lymph nodes. She was previously treated with nivolumab and combination chemotherapy (cisplatin, vinblastine and dacarbazine) and subsequently treated with LL‐37 injections upon progression of both prior regimens. She received a total of 8 weekly LL‐37 injections, with interval clinical shrinkage of injected lesions. However, approximately 45 days after initiation of this therapy, she presented with multiple verrucous papules and a vesiculo‐bullous lesion on the trunk and extremities. Clinically, most of these lesions were thought to be either squamous cell carcinoma or inflamed seborrheic keratosis. Histologically, 11 of the total 12 skin biopsies showed similar histopathologic features, with a prominent lichenoid inflammatory infiltrate admixed with eosinophils and an overlying atypical squamous epithelial proliferation with verrucous and keratoacanthoma‐like features and varying degrees of keratinocytic atypia. Interestingly, a majority of the lesions did not show spongiosis (11/12). All lesions resolved within 2 months of cessation of LL‐37 injection therapy. This case highlights adverse dermatological manifestations of LL‐37 therapy, similar to the consequences of other novel therapies.     

Upcoming strategies for the treatment of metastatic melanoma

Prognosis for advanced and metastatic melanoma is poor, with a 5-year survival of 78, 59 and 40% for patients with stage IIIA, IIIB and IIIC, respectively, and a 1-year survival of 62% for M1a, 53% for M1b and 33% for M1c. The unsatisfactory results of actual standard therapies for metastatic melanoma highlight the need for effective new therapeutic strategies. Several drugs, including BRAF, KIT and MEK inhibitors, are currently being evaluated after promising data from Phase I and Phase II studies; Vemurafenib, a BRAF-inhibitor agent, has been approved by the Food and Drug Administration (FDA) for the treatment of patients with unresectable or metastatic melanoma with the BRAF V600E mutation after a significant impact on both progression-free and overall survival was demonstrated compared with dacarbazine in a Phase III trial. Ipilimumab, an immunotherapeutic drug, has proven to be capable of inducing long-lasting responses and was approved for patients with advanced melanoma in first- and second-line treatment by the FDA and in second-line treatment by the European Medicines Agency. Furthermore, a significant survival benefit of the combination of ipilimumab with dacarbazine compared with dacarbazine alone for first-line treatment was reported. In the near future, patients with BRAF mutations could have the chance to benefit from treatment with BRAF inhibitors; patients harboring BRAF or NRAS mutations could be treated with MEK inhibitors; finally, the subgroup of patients with acral, mucosal or chronic sun-damaged melanoma harboring a KIT mutation could benefit from KIT inhibitors. Ipilimumab could become a standard treatment for metastatic melanoma, both as a single agent and in combination; its efficacy has been proven, and researchers should now address their efforts to understanding the predictive variables of response to treatment.     

Cytotoxic antimelanoma drugs suppress the activation of M2 macrophages

Together with regulatory T cells (Tregs), tumor‐associated macrophages (TAMs) play roles in maintaining the tumor microenvironment. Although cytotoxic antimelanoma drugs such as dacarbazine (DTIC), nimustine hydrochloride (ACNU) and vincristine (VCR) have been used for the treatment of malignant melanoma as adjuvant therapy in Japan, the detailed mechanisms of their immunomodulatory effects are not fully understood. As the majority of TAMs are alternatively activated M2 macrophages that favour tumor development, the aim of this study was to elucidate the immunomodulatory effects of these reagents on human monocyte‐derived M2 macrophages. First, mRNA expressions and protein production of immune checkpoint molecules, PD‐L1 and chemokines by CD163⁺ CD206⁺ M2 macrophages derived from peripheral blood mononuclear cells were investigated to determine the immunomodulatory effects of DTIC, ACNU, and VCR. DTIC and VCR significantly decreased PD‐L1 mRNA expression, which was confirmed by flow cytometry. Moreover, the mRNA expression and production of CCL22 were significantly decreased by DTIC, which suggested that DTIC might suppress the recruitment of Tregs in the tumor site. Furthermore, the decreased expression of PD‐L1 and production of CCL22 were validated in vivo, using the B16F10 mouse melanoma model, leading to abrogation of the suppressive function of T‐cell proliferation. The present report suggests one of the possible antimelanoma mechanisms of DAV combination chemotherapy for melanoma patients.