Modulation of metastatic potential of B16F10 melanoma cells by acivicin: synergistic action of glutaminase and potentiation of cisplatin cytotoxicity.

Treatment for metastatic melanoma has mostly been unsatisfactory despite advances in ongoing medical research. Here we investigated the role of acivicin, a glutamine analogue, singly and in combination with either E. coli glutaminase or cisplatin, on the growth, angiogenic activity and invasiveness of B16F10 cells in vitro and after allografting in C57BL/6 mice. B16F10 melanoma colonization in the lungs of mice was measured by monitoring colony counts. Host toxicity was assessed with reference to tumor bearing host's weight and survivability. Acivicin promoted melanoma dormancy and reduced melanoma associated angiogenic factors like VEGF level and vessel diameter. Acivicin in combination with glutaminase significantly suppressed tumor growth by 66.7% and increased life-span by 43.5% without host toxicity. Tumor VEGF content was significantly lowered by combination therapy as assessed by ELISA. Accelerated cytotoxicity, reduced invasion and enhanced apoptosis of melanoma cells were exhibited in vitro by combined than by single agent treatment. Moreover, invasion of melanoma cells through matrigel chambers was reduced in presence of acivicin and glutaminase combination. These findings support future studies of acivicin in combination with other anticancer agents for prevention of melanoma metastasis.     

Barbigerone Inhibits Tumor Angiogenesis,Growth and Metastasis in Melanoma

Tumor angiogenesis, growth and metastasis are three closely related processes. We therefore investigated theeffects of barbigerone on all three in the B16F10 tumor model established in both zebrafish and mouse models,and explored underlying molecular mechanisms. In vitro, barbigerone inhibited B16F10 cell proliferation,survival, migration and invasion and suppressed human umbilical vascular endothelial cell migration, invasionand tube formation in concentration-dependent manners. In the transgenic zebrafish model, treatment with10μM barbigerone remarkably inhibited angiogenesis and tumor-associated angiogenesis by reducing blood vesseldevelopment more than 90%. In vivo, barbigerone significantly suppressed angiogenesis as measured by H andE staining of matrigel plugs and CD31 staining of B16F10 melanoma tumors in C57BL/6 mice. Furthermore,it exhibited highly potent activity at inhibiting tumor growth and metastasis to the lung of B16F10 melanomacells injected into C57BL/6 mice. Western blotting revealed that barbigerone inhibited phosphorylation of AKT,FAK and MAPK family members, including ERK, JNK, and p38 MAPKs, in B16F10 cells mainly through theMEK3/6/p38 MAPK signaling pathway. These findings suggested for the first time that barbigerone could inhibittumor-angiogenesis, tumor growth and lung metastasis via downregulation of the MEK3/6/p38 MAPK signalingpathway. The findings support further investigation of barbigerone as a potential anti-cancer drug.     

Combining suramin and a chimeric toxin directed to basic fibroblast growth factor receptors increases therapeutic efficacy against human melanoma in an animal model.

BACKGROUND: Suramin, which binds to and blocks autocrine and paracrine growth factors required for the proliferation of neoplastic cells, is a clinically effective antitumor agent against some human tumors; however, efficacy often is limited by toxicity. In this study, suramin treatment was combined with a fibroblast growth factor (FGF) receptor-directed toxin chimera, basic FGF-saporin (bFGF-SAP), based on the authors' previous observations that autocrine-mediated resistance to bFGF-SAP in melanoma in vitro is abrogated by suramin treatment. METHODS: Severe-combined immunodeficient-Beige mice bearing SK-Mel-5 human melanoma xenografts received weekly treatments of suramin (200 or 75 mg/kg intraperitoneally) beginning on Day 5 after tumor implantation followed 18 hours later by a treatment with bFGF-SAP (0.5-5 microg/kg intravenously) for 4 weeks. The optimal interlude between the administration of suramin and bFGF-SAP was determined by tumor excision assays. The efficacy of combination therapy as a function of alternative dosing regimens was determined by tumor growth inhibition (TGI) studies. RESULTS: Fifty days after implantation, a 79-82% TGI was observed in animals receiving the suramin (200 mg/kg) plus bFGF-SAP combination regimens compared with median tumor volumes from vehicle-treated controls (3070+/-440 mm(3)). TGI observed for combination therapies varied significantly (P<0.05-0.001) from TGI observed in treatment groups receiving suramin alone (57%) or bFGF-SAP alone (34-38%). Combining bFGF-SAP (5 microg/kg) with a low, therapeutically ineffective dose of suramin (75 mg/kg) produced a 68% rate of TGI compared with controls, thus lowering the therapeutic effective dose of suramin and eliminating the suramin-related lethal toxicity (12% mortality rate) observed in animals treated with high dose suramin. CONCLUSIONS: The results of the current study suggest that combining suramin with receptor-directed therapies offers a more effective regimen for the treatment of malignant melanoma.     

Monoclonal antibody 4C5 immunostains human melanomas and inhibits melanoma cell invasion and metastasis.

PURPOSE: Tumor cell metastasis constitutes a major problem in the treatment of cancer. Because the cure rate of metastatic tumors is very low, new therapeutic approaches are needed. Heat shock protein 90 (HSP90) is a molecular chaperone that is recognized as a new target for the treatment of cancer. Here, we examine the value of a monoclonal antibody (mAb) against HSP90, mAb 4C5, as a potential marker in malignant melanomas. Moreover, we investigate the possibility to use mAb 4C5 as an inhibitor of melanoma cell invasion and metastasis. EXPERIMENTAL DESIGN: Paraffin blocks of formalin-fixed human melanoma tumor tissues were used to prepare tissue microarrays. The B16 F10 melanoma cell line was used in all the in vitro experiments. To assess melanoma cell invasion, the wound-healing assay and the Matrigel invasion assay were applied. To evaluate the effect of mAb 4C5 on tumor metastasis, we used an experimental model of metastatic melanoma. RESULTS: Immunohistochemical studies done on a panel of malignant melanomas showed positive immunostaining with mAb 4C5 in all cases. mAb 4C5 inhibits B16 F10 cell invasion by binding to surface HSP90 because it is not internalized. mAb 4C5 significantly inhibits melanoma metastasis in C57BL/6 mice inoculated with B16 F10 cells. CONCLUSIONS: mAb 4C5 could be potentially used as a novel specific marker for malignant melanomas. mAb 4C5 inhibits melanoma cell invasion in vitro by binding to cell surface HSP90 expressed on B16 F10 melanoma cells. Finally, this antibody significantly inhibits melanoma metastasis, thus rendering it a potential therapeutic agent for the treatment of cancer metastasis.     

Bromelain proteases suppress growth, invasion and lung metastasis of B16F10 mouse melanoma cells

The thiolprotease bromelain, isolated from pine apple stem, was suggested for use in adjuvant tumor therapy. This study examined the in vitro effects of crude bromelain, bromelain F9 and papain on B16F10 mouse melanoma cell lung colonization, in vitro cell proliferation, invasion through matrigel and CD44 expression. In vitro treatment of the melanoma cells with bromelain F9 and papain before i.v. injection into mice prevented lung colonization. The lung weight at day 20 was significantly reduced from 5.1% (untreated cells) to 1.6% (bromelain F9 treated cells). Papain was as effective as bromelain F9. However, there was no difference in the lung weight between bromelain F9 treated and the untreated group at day 27. Protease removal and further incubation of the B16F10 cells retained their capacity to induce lung tumor metastases. The proteases inhibited growth of the melanoma cells in a dose dependent manner. Crude bromelain was most active with a half maximal value of 7.5 mu g/ml. However, the antiproliferative effects did not correlate with the proteolytic activity. In a matrigel invasion assay, the proteases reduced the invasive capacity of the melanoma cells maximally by about 30%. Using flow cytometry, the proteases were found to reduce the CD44 density, present on the melanoma cells, to a different degree: crude bromelain was more active than bromelain F9 and papain, which had higher proteolytic activity. Crude bromelain was most active in abolishing the CD44 re-expression after protease treatment.     

Systemic NK4 gene therapy inhibits tumor growth and metastasis of melanoma and lung carcinoma in syngeneic mouse tumor models

Hepatocyte growth factor (HGF) promotes malignant development of cancer cells by enhancing invasion and metastasis. NK4, a competitive antagonist for HGF, is a bifunctional molecule that acts as a HGF antagonist and angiogenesis inhibitor. Although successful tumor inhibition by NK4 gene expression in tumor models has been demonstrated, the effects of systemic NK4 gene introduction are yet to be addressed. Here we show that systemic administration of a replication-defective adenovirus expressing NK4 (Ad.NK4) inhibits tumor growth and lung metastasis of B16F10 melanoma and Lewis lung carcinoma in syngeneic mice. Single tail-vein injection of Ad.NK4 achieved therapeutic levels of NK4 in the circulation and in multiple organs. Despite NK4 expression that was highest in the liver, toxicity in the liver was minimal. Ad.NK4-mediated growth inhibition was associated with decreased blood vessel density and increased apoptosis in tumor tissues, which suggests that NK4 suppressed tumor growth as an angiogenesis inhibitor. Metastasis of B16F10 melanoma and Lewis lung carcinoma cells to the lung was potently inhibited by systemic Ad.NK4-administration. Our results demonstrated that the adenovirus-mediated induction of high levels of circulating NK4 significantly inhibited in vivo tumor growth and distant metastasis without obvious side effects. NK4 gene therapy is thus a safe and promising strategy for the treatment of cancer patients, and further validation in clinical trials is needed. ( Cancer Sci 2009; 100: 1351–1358)     

苦参碱衍生物M19对于肿瘤细胞转移的抑制作用

目的:探讨苦参碱衍生物M19对于肝细胞癌和黑色素瘤细胞转移的抑制作用。方法:肝癌细胞Hep3B、MHCC-LM3和黑色素瘤细胞B16F10经M19处理后,检测肿瘤细胞体外迁移能力。建立C57BL/6小鼠黑色素瘤B16F10和裸鼠肝细胞癌MHCC-LM3转移模型,经M19体内给药后,观察肿瘤细胞肝、肺转移情况。结果:M19能浓度依赖性地抑制肝癌细胞和黑色素瘤细胞迁移。M19体内给药使B16F10细胞在小鼠肺的转移减少,且还能抑制MHCC-LM3细胞在裸鼠肺和肝的转移。结论:M19能在体内外抑制肝细胞癌和黑色素瘤细胞的转移。     

Potentiated antitumor effects of butyrate and actinomycin D in melanoma model in mice.

Butyrate and butyric acid derivatives are well known to induce differentiation and apoptosis of tumor cells and have also recently gained acceptance as potential anticancer agents. In this study we observed an increased expression of mTNFalpha in tumor tissues in mice treated with butyrate prodrug tributyrin. Since in in vitro experiments we observed a potentiating effects of TNFalpha and actinomycin D on B16F10 cells and also a synergistic interaction was previously claimed between those agents, we investigated the anti-tumor activity of the combination therapy with butyrate and actinomycin D in the B16F10 melanoma model in mice. The combination of the drugs resulted in a strongly potentiated tumor growth retardation in melanoma bearing mice. However the B16F10 cells in vitro did not produce any detectable amounts of TNFalpha. The presented data strongly suggest that one of the mechanism of this successful drug combination could depend on the interaction of the actinomycin D with butyrate-induced TNFalpha produced by stromal or tumor infiltrating immune cells. The results illustrate also the possible application of this combination in cancer therapy.     

Suramin inhibits the growth of malignant mesothelioma in vitro, and in vivo, in murine flank and intraperitoneal models

Surgical debulking of malignant mesothelioma (MM) ultimately fails due to local recurrence. Suramin, an inhibitor of extracellular growth factors (ECGFs), has demonstrated efficacy in the treatment of malignant mesothelioma in a small case series. Our goal was to study survival benefits and disease progression in several MM animal models treated with suramin as a potential agent for adjuvant therapy. In vitro growth of human (REN, I-45), rat (II-45) and murine (AB12) mesothelioma cell lines were measured with or without suramin exposure. Human and murine MM tumors were implanted subcutaneously into murine flanks or injected intraperitoneally (i.p.) into murine abdominal cavities. Dose and treatment schedules were optimized to reduce the rate of tumor progression and to improve survival curves. Suramin inhibited the in vitro growth of all cell lines, reaching statistical significance (P<0.01) three doubling cycles after suramin administration, with a maximum inhibition of 10-25% of control growth. A significant time- and dose-dependent effect was observed. In vivo, suramin inhibited the growth of MM in the xenogeneic model (55% of control growth, P<0.01), and in the syngeneic model at both the low and high loading doses (46 and 36% of control growth, respectively, P<0.01). Suramin treatment inhibited in vivo growth in the REN intraperitoneal model shown grossly by necropsy of same day deaths comparing treatment and control animals. Tumor inhibition with the higher dose was also reflected by the lower mean tumor burden scores (control: 4.0 and high dose: 3.4). Suramin inhibits the growth of human, murine, and rat MM in vitro, in a time- and dose-dependent manner. Suramin also inhibits the growth of human MM flank and intraperitoneal xenografts in vivo in an immunodeficient host, as well as the growth of syngeneic murine flank tumors in an immunocompetent host. These studies demonstrate that suramin may have the potential to provide effective therapy for MM, and that further studies are necessary to elucidate the survival advantage of suramin mediated MM growth inhibition.     

基因枪介导的neu基因DNA疫苗抗肿瘤作用的实验研究

目的 探讨DNA疫苗pWRG-neu的皮内免疫,对高表达neu基因的小鼠移植瘤生长和转移的抑制作用。方法 向小鼠黑色素瘤B16F10细胞系转染pcDNA-neu,用有限稀释法筛选一株高表达neu基因的细胞株B16F10-neu。在基因枪介导下,向C57BL／6小鼠导入DNA疫苗pWRG-neu,通过观察免疫动物的生存期,评价DNA疫苗的抗肿瘤作用。分离免疫动物脾细胞,经自体淋巴细胞混合培养实验,分析DNA疫苗体内免疫后机体的CTL应答。结果 筛选到一株高表达neu基因的B16F10-neu细胞株,转基因过程和外源基因的表达没有改变细胞系的增殖特性。用基因枪轰击,进行DNA疫苗pWRG-neu皮内免疫,对小鼠黑色素瘤B16F10-neu进行预防、治疗和抗转移的实验研究,结果表明,DNA疫苗的免疫能够明显推迟移植瘤的生长,延长小鼠生存期,获得明显的抗肿瘤效果。DNA疫苗免疫后可诱导小鼠脾淋巴细胞CTL活性。结论 基因枪介导的DNA疫苗pWRG-neu经皮内免疫,能够有效的诱导机体的细胞免疫应答,预防和治疗小鼠移植瘤的发生,并有一定的预防肿瘤肺转移的作用。     

Antimetastatic Effect by Anti-adhesion Therapy with Cell-adhesive Peptide of Fibronectin in Combination with Anticancer Drugs

We have investigated the therapeutic effect of CH-271 fusion polypeptide containing both cell-binding domain (C-274) and heparin-binding domain (H-271) of fibronectin in combination with anticancer drugs such as doxorubicin (DOX) or mitomycin C (MMC) on tumor metastasis of different types of tumors. CH-271 fusion polypeptide alone significantly inhibited both liver and lung metastasis when it was co-injected with L5178Y-ML25 T-lymphoma, RAW117-H10 B-lymphoma or B16-BL6 melanoma cells, and spontaneous lung metastasis of B16-BL6 melanoma cells when administered i.v. seven times before or after surgical excision of the primary tumors. Combined treatments with CH-271 and either DOX or MMC significantly inhibited liver and lung metastasis of lymphoma or melanoma cells respectively, as compared with either treatment alone or the untreated control. Administrations of CH-271 and DOX in combination substantially prolonged the survival time of mice injected i.v. with L5178Y-ML25 cells. CH-271 or DOX was effective for inhibiting the invasion of LS178Y-ML25 cells into Matrigel in a concentration-dependent manner. Our previous study has shown that CH-271-mediated inhibition of tumor invasion may be due in part to the anti-cell adhesive property without affecting the cell growth, whereas the anti-invasive effect of DOX was established to have resulted from the growth inhibition of tumor cells. Moreover, the combination of CH-271 with DOX provided a more effective inhibition of tumor invasion into Matrigel than did either alone. Thus, we have demonstrated that the combination of anti-cell adhesive CH-271 and anticancer drugs such as DOX or MMC, i.e. anti-adhesion therapy and chemotherapy, is a new approach that offers enhanced (additive) inhibitory effects on tumor metastasis and invasion.     

苏拉明对肺腺癌小鼠移植瘤生长的影响及其机制

背景与目的:有研究表明,苏拉明对恶性肿瘤有明显抑制作用,但有关其对肺腺癌体内抗瘤作用的报道很少。本实验观察苏拉明对肺腺癌LA795细胞的T739小鼠移植瘤生长和转移的抑制作用,并探讨其作用机制。方法:将32只接种LA795肺腺癌细胞T739的小鼠随机分成4组:对照组、顺铂组、苏拉明组、联合组(苏拉明加顺铂组),每组8只。用药16d,观察肿瘤生长情况,于接种后24d处死各组小鼠,取出双肺并剥离皮下肿瘤,计算出肺转移发生率,计数各组小鼠肺表面转移结节数并算出肺表面结节转移抑制率;收集移植瘤标本,称重和测量体积,免疫组化和图像分析系统定量检测肿瘤组织中表皮生长因子受体(epidermal growth factor receptor,EGFR)、P-选择素和增殖细胞核抗原(proliferating cell nuclear antigen,PCNA)的表达。结果:顺铂组、苏拉明组、联合组肿瘤的生长明显受到抑制,瘤重明显低于对照组,其抑瘤率分别为34.9%、23.8%、57.3%;苏拉明组及联合组与对照组和顺铂组相比肺转移发生率、肺表面转移结节数明显下降(P<0.05),而顺铂组与对照组比较差异则无统计学意义。EGFR和P-选择素的表达对照组高于顺铂组、苏拉明组、联合组,对照组、顺铂组、苏拉明组、联合组EGFR表达的灰度值分别为157.7±6.1、130.7±5.9、110.3±5.8、89.2±5.4,P-选择素表达的灰度值分别为134.5±5.7、117.9±5.1、96.2±5.4、78.3±4.5,各用药组与对照组相比差异均有统计学意义(P<0.05或P<0.01);对照组、顺铂组、苏拉明组、联合组增殖指数(S phase fraction,SPF)分别为(89.7±3.8)%、(68.8±4.0)%、(65.2±4.2)%、(51.3±4.2)%,各用药组SPF都比对照组低,差异有统计学意义(P<0.01)。结论:苏拉明可明显抑制肺腺癌细胞在小鼠体内的生长和转移,其作用机制可能为通过调控肿瘤细胞中的EGFR和P-选择素表达,从而抑制肿瘤细胞增殖和减少肿瘤细胞的粘附而防止转移。     

Effect of thrombin treatment of tumor cells on adhesion of tumor cells to platelets in vitro and tumor metastasis in vivo.

Seven different tumor cell lines (human melanoma SK MEL 28; hamster melanoma HM29; murine melanomas B16F10 and amelanotic melanoma B16a; human colon carcinoma HCT8; murine colon carcinoma CT26; and murine Lewis lung carcinoma) were treated with thrombin at 0.5-1 unit/ml and examined for their ability to bind to adherent platelets; HM29 was studied for its ability to bind to fibronectin and von Willebrand factor; CT26, B16F1, B16F10, and B16a were studied for their ability to form pulmonary metastasis after i.v. injection of thrombin-treated tumor cells; CT26 was studied for its ability to grow s.c. Five of 7 thrombin-treated tumor cell lines increased their adhesion to adherent platelets 2-to 3-fold. HM29 increased its adherence to fibronectin and von Willebrand factor 2- to 3-fold. CT26, B16F1, B16F10, and B16a increased experimental pulmonary metastasis 10- to 156-fold. Thrombin-treated CT26 cells demonstrated 2-fold greater growth in vivo after s.c. injection. The mechanism of enhanced adhesion of thrombin-treated tumor cells to platelets required the platelet integrin GPIIb-GPIIIa since it could be inhibited by agents known to block adhesion of ligands to GPIIb-GPIIIa (monoclonal antibody 10E5, tetrapeptide RGDS, disintegrin Albolabrin); as well as a "GPIIb-GPIIIa-like" structure on tumor cells since it could be inhibited by treatment of thrombin-treated tumor cells with 10E5 and RGDS. The thrombin effect on tumor cells was optimum at 1 h of incubation with thrombin, did not require active thrombin on the tumor cell surface, and did not require protein synthesis (not inhibited by cycloheximide). Thus, thrombin-treated tumor cells markedly enhance pulmonary metastasis. It is suggested that this may be secondary to thrombin-induced enhanced adhesion as well as growth of tumor cells.     

Pericyte dysfunction due to Shb gene deficiency increases B16F10 melanoma lung metastasis

Intravasation, vascular dissemination and metastasis of malignant tumor cells require their passage through the vascular wall which is commonly composed of pericytes and endothelial cells. We currently decided to investigate the relative contribution of these cell types to B16F10 melanoma metastasis in mice using an experimental model of host Shb gene (Src homology 2 domain-containing protein B) inactivation. Conditional inactivation of Shb in endothelial cells using Cdh5-CreERt2 resulted in decreased tumor growth, reduced vascular leakage, increased hypoxia and no effect on pericyte coverage and lung metastasis. RNAseq of tumor endothelial cells from these mice revealed changes in cellular components such as adherens junctions and focal adhesions by gene ontology analysis that were in line with the observed effects on leakage and junction morphology. Conditional inactivation of Shb in pericytes using Pdgfrb-CreERt2 resulted in decreased pericyte coverage of small tumor vessels with lumen, increased leakage, aberrant platelet-derived growth factor receptor B (PDGFRB) signaling and a higher frequency of lung metastasis without concomitant effects on tumor growth or oxygenation. Flow cytometry failed to reveal immune cell alterations that could explain the metastatic phenotype in this genetic model of Shb deficiency. It is concluded that proper pericyte function plays a significant role in suppressing B16F10 lung metastasis.     

Pentoxifylline impedes migration in B16F10 melanoma by modulating Rho GTPase activity and actin organisation

Cancer cell migration is a hallmark of metastatic cascade and compounds that can intervene in this process are clinically important. Pentoxifylline (PTX), a methyl xanthine derivative, inhibits B16F10 melanoma lung homing by inhibiting F10 invasion, MMP secretion and adhesion to matrix components. However, its effect on B16F10 migration remained unexamined, which we investigated in the present study. PTX significantly inhibits F10 migration in scratch wound assay. Elevation in cAMP levels inhibits F10 migration and PTX mediated inhibition of the process was found to be, in part, due to an increase in cellular cAMP levels. PTX induces Protein Kinase A (PKA) activity and PKA inhibitor partly reversed its effects on F10 motility. RhoA and Rac1 GTPases induce B16F10 motility and PTX was found to inhibit migration by affecting these molecules. Stress fibres and lamellipodial protrusions reduced significantly. This was accompanied with inhibition in RhoA and Rac1 membrane localisation. A stark inhibition in RhoA-GTP bound form was also observed. Taken together, the results indicate that PTX, through its phosphodiesterase action, inhibits RhoGTPases and associated actin organisation in B16F10 melanoma, thereby inhibiting cell motility.     

Pectic polysaccharide isolated from Angelica gigas Nakai inhibits melanoma cell metastasis and growth by directly preventing cell adhesion and activating host immune functions

The pectic polysaccharide (angelan) of Angelica gigas Nakai is an immunostimulator that activates the immune functions of B cells and macrophages. Here we investigated the effect of angelan on tumor growth and metastasis. Angelan was found to significantly prolong the survival rate of B16F10-implanted mice and to reduce the frequency of pulmonary metastasis of B16F10 melanoma. Moreover, the combined treatment of angelan and doxorubicin (a cytotoxic anticancer agent) more effectively inhibited tumor growth and metastasis than either compound alone. In the present study, we found that angelan directly inhibited cancer cell adhesion and invasion through the extracellular matrix, in addition to activating the immune functions of B cells and macrophages. These results suggest that angelan can inhibit tumor growth and metastasis by stimulating host immunity and directly inhibiting cancer cell adhesion.     

Resveratrol modulates the malignant properties of cutaneous melanoma through changes in the activation and attenuation of the antiapoptotic protooncogenic protein Akt/PKB

Resveratrol, a nontoxic natural product, exhibits multifaceted biological effects including antimutagenic and anticancer properties. We examined the effect of resveratrol on the expression and activation of Akt/protein kinase B and its impact on melanoma cell migration and invasiveness. We also explored the use of resveratrol as an antimalignant treatment option against skin melanoma in mouse models of the disease. Akt expression and activity were determined by a combination of real-time PCR and western blot analysis. Cell lines stably expressing Akt or a dominant negative variant were used to further establish the role of Akt during the response to resveratrol. Wound healing and transwell assays were used as in-vitro correlates of melanoma cell migration and invasiveness. The efficacy of resveratrol in the treatment of melanoma was assessed in two syngeneic mouse models. Resveratrol downregulated and inactivated Akt in B16F10 and B16BL6 melanoma cells. Resveratrol also inhibited the migratory and invasive properties of these highly malignant cells. The reduction of cell migration and invasion, however, was reversed in cell lines overexpressing Akt or after cotreatment with pharmacological inhibitors that blocked Akt degradation. Dominant-negative Akt cells were more sensitive to resveratrol and had diminished migratory properties. Oral treatment with resveratrol reduced primary tumor volume, Akt expression, and the propensity for metastasis in syngeneic mouse models of melanoma. These results suggest that resveratrol can reduce the malignant properties of highly invasive melanoma cells by inactivating Akt. The nontoxic targeting of Akt by resveratrol makes it an attractive treatment option for melanoma.     

Overexpression of Merlin in B16F10 mouse melanoma cells reduces their metastatic activity: role of the cell surface heparan sulfate glycosaminoglycans

Merlin, the protein product of the neurofibromatosis type 2 gene (NF2) acts as a tumor suppressor in mice and humans. In this study, melanoma B16F10 cells were engineered to overexpress the NF2 gene by establishing stable transductants. A cell line overexpressing Merlin (B16F10-M) was generated. When compared to the parental cells, the B16F10-M cells demonstrated differences in their cell surface organization. The overexpressing strain changed its ability to grow in soft agar as well as its cell motility properties. B16F10-M cells were then examined in the in vivo mouse melanoma tumor growth and tumor metastasis models. While tumor growth was marginally affected, the presence of increased Merlin severely reduced the metastastatic ability of the cells. When isolated using specific enzymes with distinct substrate specificity, the cell surface heparan sulfate glycosaminoglycans (HSGAGs) from the overexpressing B16F10-M cells, inhibited the metastatic properties of the parental B16F10 cells. The results obtained provide a causal link between the reorganization/changes to the cell surface HSGAGs by the overexpression of Merlin and the inhibition of the metastatic activity of the mouse melanoma B16F10 cells in vivo.     

Demethylating agent 5-aza-2'-deoxycytidine enhances expression of TNFRI and promotes TNF-mediated apoptosis in vitro and in vivo

Promoter hypermethylation within CpG islands plays an important role in the silencing of numerous genes involved in tumor growth including tumor suppressor genes and genes encoding proteins involved in the execution of apoptosis. Here we show that CpG islands are also found within the promoter regions of both human and mouse TNFR1 (TNFRSF1) genes. Selective inhibition of methyltransferases with 5-aza-2'-deoxycytidine increases the expression of TNFR1 in human (WM35) and murine (B16F10) melanoma cells and sensitizes them to TNF-induced apoptosis both in vitro and in vivo. Treatment of mice with the combination of 5-aza-2'-deoxycytidine and recombinant TNF leads to potentiated antitumor effects. Importantly the antitumor efficacy of the combination treatment is shown when both drugs are used in doses that do not exert any antitumor effects when used alone. Altogether our studies show that the combination treatment with 5-aza-2'-deoxycytidine and TNF might be effective in the treatment of melanoma.     

Sterically stabilized etoposide liposomes: evaluation of antimetastatic activity and its potentiation by combination with sterically stabilized pentoxifylline liposomes in mice

Cytotoxic activity of chemotherapeutic agents can be enhanced by site-specific delivery or by combination with other less toxic agents. In the present study, enhancement in the antimetastatic activity of etoposide (ETP) by encapsulation in sterically stabilized liposomes was evaluated in the murine experimental B16F10 melanoma model. Further, potentiation of its antimetastatic activity by combination with pentoxifylline (PTX) solution or sterically stabilized PTX liposomes was evaluated in the same animal model. Upon intravenous administration, ETP solution and ETP liposomes inhibited pulmonary tumor nodule formation in a dose-dependent manner. Encapsulation of ETP in liposomes resulted in significant enhancement in its antimetastatic activity at doses of 0.5 mg/kg and 0.75 mg/kg as compared to ETP solution at similar doses. In combination therapy, the effect of sequence of administration of the drugs, ETP and PTX, was evaluated. Enhancement of antimetastatic activity of ETP solution when used in combination with PTX solution was effected by the sequence in which the solutions were administered. However, a combination of ETP liposomes and PTX liposomes led to potentiation of antimetastatic activity in a sequence-independent manner. The results indicate that antimetastatic activity of ETP is significantly enhanced by encapsulation in liposomes. Administration of ETP liposomes with PTX liposomes further potentiated the activity, suggesting the usefulness of this combination in clinical practice for reducing the dose-limiting toxic effects of ETP.