Melanoma Angiogenesis Research Articles

Neoangiogenesis in Melanoma: An Issue in Biology and Systemic Treatment.

Neoangiogenesis is a recognized hallmark of cancer, granting tumor cells to dispose of metabolic substrates through a newly created vascular supply. Neoangiogenesis was also confirmed in melanoma, where vascular proliferation is associated with increased aggressiveness and poorer prognosis. Furthermore, melanoma cells show the so-called vascular mimicry, consisting in the assumption of endothelial-like features inducing the expression of pro-angiogenic receptors and ligands, which take part in the interplay with extracellular matrix (ECM) components and are potentiated by the ECM remodeling and the barrier molecule junction alterations that characterize the metastatic phase. Although neoangiogenesis was biologically proven and clinically associated with worse outcomes in melanoma patients, in the past anti-angiogenic therapies were employed with poor improvement of the already unsatisfactory results associated with chemotherapic agents. Among the novel therapies of melanoma, immunotherapy has led to previously unexpected outcomes of treatment, yet there is a still strong need for potentiating the results, possibly by new regimens of combination therapies. Molecular models in many cancer types showed mutual influences between immune responses and vascular normalization. Recently, clinical trials are investigating the efficacy of the association between anti-angiogenetic agents and immune-checkpoint inhibitors to treat advanced stage melanoma. This paper reviews the biological bases of angiogenesis in melanoma and summarizes the currently available clinical data on the use of anti-angiogenetic compounds in melanoma.

SFRP2 Supersedes VEGF as an Age-related Driver of Angiogenesis in Melanoma, Affecting Response to Anti-VEGF Therapy in Older Patients.

Angiogenesis is thought to be critical for tumor metastasis. However, inhibiting angiogenesis using antibodies such as bevacizumab (Avastin), has had little impact on melanoma patient survival. We have demonstrated that both angiogenesis and metastasis are increased in older individuals, and therefore sought to investigate whether there was an age-related difference in response to bevacizumab, and if so, what the underlying mechanism could be. We analyzed data from the AVAST-M trial of 1,343 patients with melanoma treated with bevacizumab to determine whether there is an age-dependent response to bevacizumab. We also examined the age-dependent expression of VEGF and its cognate receptors in patients with melanoma, while using syngeneic melanoma animal models to target VEGF in young versus old mice. We also examined the age-related proangiogenic factor secreted frizzled-related protein 2 (sFRP2) and whether it could modulate response to anti-VEGF therapy. We show that older patients respond poorly to bevacizumab, whereas younger patients show improvement in both disease-free survival and overall survival. We find that targeting VEGF does not ablate angiogenesis in an aged mouse model, while sFRP2 promotes angiogenesis in vitro and in young mice. Targeting sFRP2 in aged mice successfully ablates angiogenesis, while the effects of targeting VEGF in young mice can be overcome by increasing sFRP2. VEGF is decreased during aging, thereby reducing response to bevacizumab. Despite the decrease in VEGF, angiogenesis is increased because of an increase in sFRP2 in the aged tumor microenvironment. These results stress the importance of considering age as a factor for designing targeted therapies.

MicroRNA-145 suppresses uveal melanoma angiogenesis and growth by targeting neuroblastoma RAS viral oncogene homolog and vascular endothelial growth factor.

BackgroundUveal melanoma (UM) is the most common primary intraocular malignancy in adults. It has been demonstrated that microRNA-145 (miR-145) is correlated with the progression of various cancers by regulating the expression of multiple target genes, especially a number of genes that regulate angiogenesis and proliferation. However, the underlying mechanisms of miR-145 in tumor angiogenesis of UM are still not well illustrated. Thus, we aimed to explore the potential target genes or pathways regulated by miR-145 in UM and the effect of miR-145 on invasion and angiogenesis.MethodsTotally, 24 choroid samples were collected in our study, including 12 UM samples and 12 normal uveal tissues. The expression of neuroblastoma RAS viral oncogene homolog (N-RAS), phosphorylated protein kinase B (p-AKT), and vascular endothelial growth factor (VEGF) in UM tissues and normal uveal tissues was analyzed using Western blotting analysis. Lentivirus expression system was used to construct MUM-2B and OCM-1 cell lines with stable overexpression of miR-145. Transwell and endothelial cell tube formation assay were used to measure the effects of miR-145 on the invasion and angiogenesis of UM in vitro. The downstream target genes of miR-145 were predicted by bioinformatics and confirmed using a luciferase assay. BALB/c nude mice models were established to investigate the mechanisms of miR-145 on tumor growth and angiogenesis in vivo. Group data comparisons were performed using analysis of Student's t test. A two-tailed P < 0.05 was considered as statistically significant.ResultsThe results of Western blotting analysis indicated that the expressions of N-RAS (1.10 ± 0.35 vs. 0.41 ± 0.36, t = 3.997, P = 0.012), p-AKT (1.16 ± 0.22 vs. 0.57 ± 0.03, t = 7.05, P = 0.001), and VEGF (0.97 ± 0.32 vs. 0.45 ± 0.21, t = 3.314, P = 0.008) in UM tumor tissues were significantly higher than those in normal uveal tissue. Luciferase assay demonstrated N-RAS and VEGF as downstream targets of miR-145. Moreover, tube formation assay revealed that miR-145-transfected human microvascular endothelial cell line formed shorter tube length (36.10 ± 1.51 mm vs. 42.91 ± 0.94 mm, t = 6.603, P = 0.003) and less branch points (350.00 ± 19.97 vs. 406.67 ± 17.62, t = 3.685, P = 0.021) as compared with controls. In addition, the numbers of invaded MUM-2B and OCM-1 cells with miR-145 overexpression were significantly lower than the controls (35.7 ± 3.3 vs. 279.1 ± 4.9, t = 273.75, P < 0.001 and 69.5 ± 4.4 vs. 95.6 ± 4.7, t = 21.27, P < 0.001, respectively). In vivo, xenografts expressing miR-145 had smaller sizes (miR-145 vs. miR-scr, 717.41 ± 502.62 mm3vs. 1694.80 ± 904.33 mm3, t = 2.314, P = 0.045) and lower weights (miR-145 vs. miR-scr, 0.74 ± 0.46 g vs. 1.65 ± 0.85 g, t = 2.295, P = 0.045).ConclusionOur results indicated that miR-145 is an important tumor suppressor and the inhibitory strategies against N-RAS/VEGF signaling pathway might be potential therapeutic applications for UM in the future.

Circ-GLI1 promotes metastasis in melanoma through interacting with p70S6K2 to activate Hedgehog/GLI1 and Wnt/\u03b2-catenin pathways and upregulate Cyr61

Circular RNAs (circRNAs) are emerging regulators in the development of human cancers. However, the role of circRNAs in melanoma is poorly understood. Microarray analysis and qRT-PCR was applied to screen out circRNAs that were differentially expressed in melanoma cells compared to normal cells. Currently, we first proved that inhibition of CYR61, an angiogenesis factor with controversial functions in melanoma, restrained cell migration, invasion and angiogenesis in melanoma. Thereafter, a novel circRNA hsa_circ_0027247 derived from GLI1 (circ-GLI1) was identified to positively modulate CYR61 expression in melanoma cell lines. Besides, silencing circ-GLI1 hindered melanoma cell metastasis as well. Interestingly, we unveiled that circ-GLI1 enhanced CYR61 transcription by an indirect manner. Meanwhile, circ-GLI1 activated Hedgehog/GLI1 and Wnt/β-catenin pathways by affecting the degradation of GLI1 and β-catenin. Moreover, we found that circ-GLI1 interacted with p70S6K2 to induce GSK3β phosphorylation at Ser9, and therefore blocked the binding of GSK3β with GLI1 and β-catenin so as to elevate their protein expression. Of note, CYR61 was transcriptionally activated by MYC, a well-recognized downstream target of both GLI1 and β-catenin. In conclusion, circ-GLI1 exacerbates the metastasis and angiogenesis of melanoma by upregulating Cyr61 via p70S6K2-dependent activation of Hedgehog/GLI1 and Wnt/β-catenin pathways.

Association of pathogenic germline variant KDR Q472H with angiogenesis and resistance to treatment in melanoma.

10060 Background: Preclinical data suggest that melanoma angiogenesis promotes resistance to MAPK-pathway (MAPKi) and immune checkpoint inhibitors (ICIs). However, phase II clinical trials of anti-angiogenic therapy in melanoma were disappointing. We previously identified a pathogenic germline variant Q472H in the kinase insert domain receptor [KDR Q472H; vascular endothelial growth factor receptor-2 (VEGFR-2)] in 35% of primary melanoma patients. We hypothesize that KDR Q472H promotes resistance to MAPKi or ICIs, and that combined MAPKi or ICI and VEGF pathway inhibition may improve outcomes in patients harboring the variant. Methods: Metastatic melanoma (MM) patient clinical data and biospecimens enrolled in the NYU Langone Medical Center Melanoma program were studied. KDR status was determined by TaqMan assays. Tumor microvessel density (MVD) was assessed by CD34 immunohistochemistry. The impact of KDR Q472H on the tumor microenvironment was determined by RNA-seq and Nanostring. Synergy between BRAF (dabrafenib) and VEGFR-2 (lenvatinib) inhibitors in KDR-genotyped MM cell lines was assessed using cell proliferation assays and the Chou-Talalay method. Synergy between ICIs and anti-VEGFR-2 was evaluated in vivo using a B16 melanoma model. Results: We studied 221 MM patients (38% KDR Q472H variants). KDR Q472H variant was significantly associated with higher tumor MVD (P = 0.002). Among the MAPKi-treated patients, KDR Q472H homozygotes had shorter median progression-free survival (PFS, 3.3 vs 9.7 months, P = 0.009) than KDR wild type (WT). In patients treated with anti-PD-1-based therapies, response rates were lower in KDR Q472H variant patients compared to WT (P = 0.012), with shorter median PFS (8.4 months vs not reached, P = 0.0443). Transcriptomic analyses identified an immunosuppressive phenotype in KDR Q472H tumors, with reduced expression of genes associated with chemotaxis, inflammation, T cell activity, and antigen presentation. Consistent with this finding, VEGFR-2 blockade in a KDR Q472H B16 mouse melanoma model augmented the anti-melanoma immune response. KDR Q472H cell lines displayed synergistic cytotoxicity with dabrafenib and lenvatinib, compared to KDR WT cells. Conclusions: Our data demonstrate that melanoma patients with pathogenic germline variant KDR Q472H may be more resistant to both ICIs and MAPKi. Anti-angiogenic therapy should be reconsidered within this specific subset of patients in prospective clinical trials.

Elevated VEGF-A &amp; PLGF concentration in aqueous humor of patients with uveal melanoma following Iodine-125 plaque radiotherapy

To measure the concentration of vascular endothelial growth factor-A (VEGF-A), and placental growth factor (PLGF) in aqueous humor of uveal melanoma patients before and after Iodine-125 plaque therapy (IPT), determine the postoperative fluctuation and evaluate associated factors in vivo. Participants were 18 Chinese patients with uveal melanoma who were elected to IPT. Undiluted aqueous humor samples were collected at Iodine plaque implant and removal time, then stored immediately at -80°C until assayed. The concentration of VEGF-A, PLGF and other 7 cytokines comprising interleukin-2 (IL-2), IL-8, IL-10, interferon (IFN)-γ, programmed death (PD)-1, transforming growth factor (TGF)-β1 and insulin-like growth factor (IGF)-1 in aqueous humor was measured using Raybiotech immunoassay kit, a high throughput strategy. The VEGF-A and PLGF levels were compared across preoperation and postoperation subgroups, as well as those of other 7 interleukins. Correlation and grouped analyses were conducted to determine the independent effects of clinical parameters and other cytokines on VEGF-A and PLGF concentration or fluctuation. This study set a self-control design. VEGF-A (P=0.038) and PLGF (P=0.026) were the only two increased cytokines after IPT. Preoperative and postoperative level of VEGF-A and PLGF (r=0.575, P=0.013; r=0.987, P<0.001) correlated with each other significantly. Level of VEGF-A (r=0.626, P=0.005; r=0.588, P=0.01) and PLGF (r=0.616, P=0.007; r=0.588, P=0.01) had positive correlation with tumor thickness consistently. Elevated VEGF-A or PLGF level were strong predictive factors of each other (P=0.007, OR=60.0). The elevated VEGF-A group showed a higher postoperative level of IFN-γ (P=0.005), IL-2 (P<0.001) and IL-10 (P=0.004) in aqueous humor. When the elevated PLGF group got similar results that a higher postoperative level of IFN-γ (P=0.007), IL-2 (P<0.001) and IL-10 (P=0.013) in aqueous humor. This study reveals that VEGF-A and PLGF in aqueous humor significantly increased with tumor thickness and radiation process in uveal melanoma patients. VEGF-A and PLGF may be crucial in uveal melanoma genesis and radiotherapy reactions. Immune mediators comprised IFN-γ, IL-2 and IL-10 could play roles in the link between inflammation and angiogenesis in uveal melanoma when exposed to radiotherapy.

核蛋白14对黑素瘤新生血管形成的影响及机制研究

Objective To evaluate the effect of nucleolar protein 14 (NOP14) on angiogenesis in melanoma. Methods Melanoma tissues were collected from 40 patients with pathologically diagnosed melanoma in Guangzhou First People′s Hospital from January 2016 to December 2018, and immunohistochemical study was conducted to determine the expression of NOP14 and CD31 (expressed as microvessel density [MVD]) . Melanoma cell lines A375 and SK-MEL-1 were both divided into 4 groups: empty vector group transfected with the empty vector, NOP14 group transfected with a NOP14-overexpressing vector, siNOP14 group transfected with the siRNA targeting NOP14, and siNC group transfected with a negative control siRNA. Fluorescence-based quantitative PCR and Western blot analysis were performed to determine the mRNA and protein expression of NOP14 respectively, and Western blot analysis and enzyme-linked immunosorbent assay (ELISA) to measure the expression of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) in cells and their culture media. Co-culture models of human umbilical vein endothelial cells (HUVECs) and A375/SK-MEL-1 cells in the above groups were established in Transwell chambers, and cell counting kit-8 (CCK8) assay, Transwell migration and invasion assays and Matrigel-based vasculogenic mimicry assay were performed to evaluate the cellular proliferative, migratory, invasive activity and tube formation capacity respectively. A linear regression model was used to analyze the relationship between NOP14 expression and MVD in melanoma tissues, multi-way analysis of variance to analyze the difference in cellular proliferative activity, and independent-sample t test to compare other experimental indices between 2 groups. Results The expression of CD31 (MVD) was 44 ± 13 in the group with high NOP14 expression (n = 20) , 58 ± 16 in that with moderate NOP14 expression (n = 17) , and 62 ± 11 in that with low NOP14 expression (n = 3) . The NOP14 expression was negatively correlated with MVD (r = - 0.525, P = 0.017) . Compared with the empty vector group, the expression of VEGF and VEGFR in A375 and SK-MEL-1 cells and their culture media significantly decreased in the NOP14 group (all P < 0.05) . Compared with the siNC group, the expression of VEGF and VEGFR in the A375 and SK-MEL-1 cells and their culture media significantly increased in the siNOP14 group (all P < 0.05) . In the co-culture models of A375 cells and HUVECs, the NOP14 group showed significantly decreased proliferative activity of HUVECs (F = 131.85, P < 0.05) , and numbers of migratory cells (22 ± 5 vs. 63 ± 8, t = 7.07, P = 0.002) , invasive cells (14 ± 5 vs. 45 ± 10, t = 4.94, P = 0.008) and branch points (8 ± 2 vs. 14 ± 3, t = 5.06, P < 0.001) compared with the empty vector group; compared with the siNC group, the siNOP14 group showed significantly increased proliferative activity of HUVECs (F = 79.92, P < 0.01) , and numbers of migratory cells (152 ± 30 vs. 59 ± 4, t = 5.36, P = 0.006) , invasive cells (134 ± 21 vs. 50 ± 8, t = 6.40, P < 0.001) and branch points (27 ± 3 vs. 15 ± 4, t = 6.10, P < 0.001) . In the co-culture models of SK-MEL-1 cells and HUVECs, the 4 groups showed the same trend of changes in the cellular proliferative, migratory, invasive activity and tube formation capacity of HUVECs as the above groups in the co-culture models of A375 cells and HUVECs. Conclusion The NOP14 expression is negatively correlated with MVD in melanoma tissues, and NOP14 can inhibit angiogenesis in melanoma. Key words: Nevi and melanomas; Melanoma, experimental; Nuclear proteins; Angiogenesis inhibitors; Cell proliferation; Cell movement; Nucleolar protein 14

Naringenin exerts anticancer effects by inducing tumor cell death and inhibiting angiogenesis in malignant melanoma.

Malignant melanoma is one of the most deadly skin cancer, due to its aggressive proliferation and metastasis. Naringenin, abundantly present in citrus fruits, has widely studied in cancer therapy. In this study, we investigated whether naringenin also has anticancer effects against B16F10 murine and SK-MEL-28 human melanoma cells. Moreover, we assessed the effects of naringenin treatment on angiogenesis of HUVECs and ex vivo sprouting of microvessels.Naringenin inhibited tumor cell proliferation and migration in a dose-dependent manner in B16F10 and SK-MEL-28 cells, which is supported by the results that phosphorylation of ERK1/2 and JNK MAPK decreased. Furthermore, naringenin induced cell apoptosis. Western blot analysisshowed naringenin treatment significantly upregulated the protein expression of activated cas3 and PARP in B16F10 and SK-MEL-28 cells. In addition, in vitro and ex vivo angiogenesis assays demonstrated that naringenin treatment potently suppressed EC migration, tube formation, and sprouting of microvessels. RT-PCR analysis showed that naringenin treatment significantly reduced the mRNA expression of Tie2, but did not inhibit the expression of Ang2. In conclusion, present study demonstrates the anticancer effects of naringenin by its induction of tumor cell death and inhibition of angiogenesis in malignant melanoma, suggesting that naringenin has potential as a safe and effective therapeutic agent to treat melanoma.

Preventing Calpain Externalization by Reducing ABCA1 Activity with Probenecid Limits Melanoma Angiogenesis and Development

Calpains, intracellular proteases specifically inhibited by calpastatin, play a major role in neoangiogenesis involved in tumor invasiveness and metastasis. They are partly exteriorized via the ATP-binding cassette transporter A1(ABCA1) transporter, but the importance of this process in tumor growth is still unknown. The aim of our study was to investigate the role of extracellular calpains in a model of melanoma by blocking their extracellular activity or exteriorization. In the first approach, a B16-F10 model of melanoma was developed in transgenic mice expressing high extracellular levels of calpastatin. In these mice, tumor growth was inhibited by ∼ 3-fold compared with wild-type animals. Invitro cytotoxicity assays and invivo tumor studies have demonstrated that this protection was associated with a defect in tumor neoangiogenesis. Similarly, in wild-type animals given probenecid to blunt ABCA1 activity, melanoma tumor growth was inhibited by ∼ 3-fold. Again, this response was associated with a defect in neoangiogenesis. Invitro studies confirmed that probenecid limited endothelial cell migration and capillary formation from vascular explants. The observed reduction in fibronectin cleavage under these conditions is potentially involved in the response. Collectively, these studies demonstrate that probenecid, by blunting ABCA1 activity and thereby calpain exteriorization, limits melanoma tumor neoangiogenesis and invasiveness.

Tumour Angiogenesis in Uveal Melanoma Is Related to Genetic Evolution.

Increased angiogenesis is associated with a higher metastasis- and mortality rate in uveal melanoma (UM). Recently, it was demonstrated that genetic events, such as 8q-gain and BAP1-loss, influence the level of immune infiltrate. We aimed to determine whether genetic events, and specific cytokines, relate to angiogenesis in UM. Data from UM patients who underwent enucleation between 1999 and 2008 were analysed. Microvascular density (MVD) and the presence of infiltrating immune cells were determined with immunohistochemistry (IHC) and immunofluorescence in 43 cases. Chromosome status, BAP1 IHC and mRNA expression of angiogenesis-related genes were known in 54 cases. Tumours with monosomy 3/BAP1-loss showed a higher MVD compared to tumours with disomy 3/normal BAP1 expression (p = 0.008 and p = 0.004, respectively). Within BAP1-positive lesions (n = 20), 8q-gain did not relate to MVD (p = 0.51). A high MVD was associated with an increased expression of angiopoietin 2 (ANGPT2) (p = 0.041), Von Willebrand Factor (VWF) (p = 0.010), a decreased expression of vascular endothelial growth factor B (VEGF-B) (p = 0.024), and increased numbers of tumour-infiltrating macrophages (CD68+, p = 0.017; CD68+CD163+, p = 0.031) and lymphocytes (CD4+, p = 0.027). Concluding, vascular density of UM relates to its genetic profile: Monosomy 3 and BAP1-loss are associated with an increased MVD, while an early event (gain of 8q) is not independently related to MVD, but may initiate a preparation phase towards development of vessels. Interestingly, VEGF-B expression is decreased in UM with a high MVD.

Hexokinase2 controls angiogenesis in melanoma by promoting aerobic glycolysis and activating the p38-MAPK signaling.

In this study, we used endostatin (ES)-induced apoptosis of endothelial cells to study the role of Hexokinase2 (HK2) in the control of angiogenesis in melanoma. Real-time polymerase chain reaction and Western blot analysis were performed to explore the effect of HK2, lactate, and ES on the levels of caspase-9/3, ATP, and p38/MAPK activation. ES increased the levels of caspase-9/3 while decreasing the level of ATP, whereas ES + HK2 and lactate both restored the normal levels of caspase-9/3 and ATP. In addition, cells transfected with HK2 short hairpin RNA1 (HK2shRNA1) and HK2shRNA2 showed an evident decrease in the levels of caspase-9/3 along with an obvious increase in the level of ATP. Knockdown of HK2 also increased O2 consumption while decreasing the extracellular level of lactate and the phosphorylation of p38-mitogen-activated protein kinase (MAPK). On the other hand, the lactate treatment elevated the phosphorylation of p38-MAPK under time- and concentration-dependent manner. In the study, we clarified the role of HK2 in the control of apoptosis of ECs, which plays an important role in the angiogenesis of melanoma by promoting aerobic glycolysis and activating the p38-MAPK signaling.

Role of angiogenesis in melanoma progression: Update on key angiogenic mechanisms and other associated components.

Angiogenesis, the formation of new blood vessels from existing blood vessels, is a complex and highly regulated process that plays a role in a wide variety of physiological and pathological processes. In malignancy, angiogenesis is essential for neoplastic cells to acquire the nutrients and oxygen critical for their continued proliferation. Angiogenesis requires a sequence of well-coordinated events mediated by a number of tightly regulated interactions between pro-angiogenic factors and their corresponding receptors expressed on various vascular components (e.g., endothelial cells and pericytes) and stromal components forming the extracellular matrix. In this review, we discuss the functional roles of key growth factors and cytokines known to promote angiogenesis in cutaneous melanoma and key factors implicated in the extracellular matrix remodeling that acts synergistically with angiogenesis to promote tumor progression in melanoma, incorporating some of the most up-to-date basic science knowledge from recently published in vivo and in vitro experimental studies.

Uveal Melanoma, Angiogenesis and Immunotherapy, Is There Any Hope?

Uveal melanoma is considered a rare disease but it is the most common intraocular malignancy in adults. Local treatments are effective, but the systemic recurrence rate is unacceptably high. Moreover, once metastasis have developed the prognosis is poor, with a 5-year survival rate of less than 5%, and systemic therapies, including immunotherapy, have rendered poor results. The tumour biology is complex, but angiogenesis is a highly important pathway in these tumours. Vasculogenic mimicry, the ability of melanomas to generate vascular channels independently of endothelial cells, could play an important role, but no effective therapy targeting this process has been developed so far. Angiogenesis modulates the tumour microenvironment of melanomas, and a close interplay is established between them. Therefore, combining immune strategies with drugs targeting angiogenesis offers a new therapeutic paradigm. In preclinical studies, these approaches effectively target these tumours, and a phase I clinical study has shown encouraging results in cutaneous melanomas. In this review, we will discuss the importance of angiogenesis in uveal melanoma, with a special focus on vasculogenic mimicry, and describe the interplay between angiogenesis and the tumour microenvironment. In addition, we will suggest future therapeutic approaches based on these observations and mention ways in which to potentially enhance current treatments.

Rapamycin suppresses angiogenesis and lymphangiogenesis in melanoma by downregulating VEGF-A/VEGFR-2 and VEGF-C/VEGFR-3 expression.

Background: Cutaneous melanoma is a highly malignant tumor which tends to metastasize in the early stage and leads to poor prognosis. Hematogenous and lymphatic metastasis are common in the dissemination of melanoma. Rapamycin, an mTOR inhibitor, was reported to have anti-angiogenic and anti-lymphangiogenic properties.Aim: The aim of this study was to investigate if rapamycin can inhibit the formation of blood vessels and lymphatic vessels in melanoma.Methods: A melanoma xenograft model was generated by subcutaneously transplanting A375 human melanoma cells into the back of immunodeficient mice. Two weeks after cell transplantation, rapamycin was injected intraperitoneally every other day seven times. Then, tumors were harvested. Hematoxylin-eosin (H-E) staining, immunohistochemical staining, Western blot, and quantitative PCR were performed to observe the pathological structure of the tumor, the distribution of blood vessels and lymphatic vessels, and the expression of mTOR signal pathway, VEGF-A/VEGFR-2, and VEGF-C/VEGFR-3.Results: The results showed that CD34(+) blood vessels and LYVE-1(+) lymphatic vessels decreased in the peritumor and intratumor region in rapamycin-treated tumors. Expression of p-4EBP1 and p-S6K1 proteins was downregulated. Expression of both proteins and mRNAs of VEGF-A/VEGFR-2 and VEGF-C/VEGFR-3 was downregulated.Conclusion: In conclusion, rapamycin suppresses angiogenesis and lymphangiogenesis in melanoma by blocking the mTOR signal pathway and subsequently downregulating the expression of VEGF-A/VEGFR-2 and VEGF-C/VEGFR-3. Therefore, targeted therapy via mTOR signal pathway may control the hematogenous and lymphatic metastasis of melanoma, and even prolong patients’ survival time.

Herbacetin suppressed MMP9 mediated angiogenesis of malignant melanoma through blocking EGFR-ERK/AKT signaling pathway

Malignant melanoma remains a challenge for clinical practice and novel therapeutic strategies are urgently needed. Herbacetin, a natural flavonoid compound that has multiple pharmacological activities, exerts anticancer effects on several human tumors. In this study, the anti-angiogenesis effect of Herbacetin in human malignant melanoma was investigated. The results indicated that Herbacetin treatment significantly suppressed tumor growth and angiogenesis of malignant melanoma both in vitro and in vivo. In melanoma A375 and Hs294T cells, Herbacetin treatment suppressed both EGF-induced and constitutive phosphorylation of EGFR, accelerated the internalization and degradation of EGFR, and subsequently suppressed the activation of the downstream kinases (AKT and ERK). Moreover, MMP9 was determined as a key angiogenic factor in Herbacetin treated melanoma cells. Knockdown of MMP9 suppressed the in vitro angiogenesis while overexpression of MMP9 in Herbacetin treated melanoma cells restored the angiogenesis ability. We concluded that Herbacetin suppressed melanoma angiogenesis through blocking EGFR-ERK/AKT-MMP9 signaling pathway and Herbacetin may be developed as a potential drug for melanoma treatment.

The Inhibitory Effect of Propylene Glycol Alginate Sodium Sulfate on Fibroblast Growth Factor 2-Mediated Angiogenesis and Invasion in Murine Melanoma B16-F10 Cells In Vitro.

Melanoma is one of the most malignant and aggressive types of cancer worldwide. Fibroblast growth factor 2 (FGF2) is one of the critical regulators of melanoma angiogenesis and metastasis; thus, it might be an effective anti-cancer strategy to explore FGF2-targeting drug candidates from existing drugs. In this study, we evaluate the effect of the marine drug propylene glycol alginate sodium sulfate (PSS) on FGF2-mediated angiogenesis and invasion. The data shows that FGF2 selectively bound to PSS with high affinity. PSS inhibited FGF2-mediated angiogenesis in a rat aortic ring model and suppressed FGF2-mediated invasion, but not the migration of murine melanoma B16-F10 cells. The further mechanism study indicates that PSS decreased the expression of activated matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9), and also suppressed their activity. In addition, PSS was found to decrease the level of Vimentin in B16-F10 cells, which is known to participate in the epithelial–mesenchymal transition. Notably, PSS did not elicit any changes in cancer cell viability. Based on the results above, we conclude that PSS might be a potential drug to regulate the tumor microenvironment in order to facilitate the recovery of melanoma patients.

Knockdown of FBXO22 inhibits melanoma cell migration, invasion and angiogenesis via the HIF-1α/VEGF pathway.

F-box proteins, a type of substrate-recognition complexes consisting of SKP1-cullin 1-F-box protein (SCF) E3 ligase, can critically affect many cellular processes because of the ubiquitylation and subsequent degradation of target proteins. This study investigated the effect of FBXO22 on melanoma angiogenesis, migration, and invasion. Results showed that FBXO22 staining intensity was increased in malignant melanoma (MM) compared with that in skin tissue (P˂0.001). The percentage of high FBXO22 expression in MM (74.3%) was markedly higher than that in paracancerous and skin tissues (0%) (P˂0.001). FBXO22 was also overexpressed in MM tissues compared with that in normal skin tissues. FBXO22 knockdown in vitro inhibited MM cell migration, invasion, and angiogenesis (P < 0.001). In vivo studies confirmed that using nude mice with knocked down FBXO22 reduced the formation of blood vessels and decreased the positive rate of CD31 (P < 0.05). HIF-1α expression varied with FBXO22, indicating that FBXO22 regulated the expression of HIF-1α and VEGFA and that FBXO22 was a regulator of HIF-1α and VEGF for the control of tumor angiogenesis. In conclusion, FBXO22 promoted the migration and invasion of tumor cells and melanoma angiogenesis via HIF-1α upregulation. This study demonstrated that FBXO22 knockdown suppressed tumor progression and metastasis, suggesting that FBXO22 might be developed as a novel target for treating patients with MM.

CXCR7 promotes melanoma tumorigenesis via Src kinase signaling

Chemokine receptors have been documented to exert critical functions in melanoma progression. However, current drugs targeting these receptors have limited efficacy in clinical applications, suggesting the urgency to further explore the roles of chemokine receptors in melanoma. Here we found that C–X–C chemokine receptor 7 (CXCR7) was the most highly expressed chemokine receptor in murine melanoma cell lines. In addition, the expression level of CXCR7 was positively correlated with melanoma progression in the clinical samples. High CXCR7 expression was associated with shorter overall survival in melanoma patients. Increased expression of CXCR7 augmented melanoma proliferation in vitro and tumor growth in vivo, whereas knockout of CXCR7 exhibited significant inhibitory effects. Moreover, our data elucidated that CXCR7 activated Src kinase phosphorylation in a β-arrestin2-dependent manner. The administration of the Src kinase inhibitor PP1 or siRNA specific for β-arrestin2 abolished CXCR7-promoted cell proliferation. Importantly, CXCR7 also regulated melanoma angiogenesis and the secretion of vascular endothelial growth factor (VEGF). Subsequent investigations revealed a novel event that the activation of the CXCR7-Src axis stimulated the phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) to accelerate the translation of hypoxia-inducible factor 1α (HIF-1α), which enhanced the secretion of VEGF from melanoma cells. Collectively, our results illuminate the crucial roles of CXCR7 in melanoma tumorigenesis, and indicate the potential of targeting CXCR7 as new therapeutic strategies for melanoma treatment.

The interplay of CDK4 and CDK6 in melanoma.

The cyclin-dependent kinases CDK4 and CDK6 promote progression through the cell cycle, where their functions are considered to be redundant. Recent studies have identified an additional role for CDK6 in the transcriptional regulation of cancer-relevant genes such as VEGF-A and EGR1 in hematopoietic malignancies. We show that the CDK4/6 inhibitor PD0332991 causes a significant decrease in tumor growth in a xenotransplantation mouse model of human melanoma. shRNA knockdown of either CDK4 or CDK6 significantly reduces cell proliferation and impedes their migratory capacity in vitro, which translates into a strong inhibition of tumor growth in xenotransplantation experiments. CDK4/6 inhibition results not only in the pronounced reduction of cell proliferation but also in an impaired tumor angiogenesis. CDK6 knockdown in melanoma cell lines impairs VEGF-A expression and reduces the potential stimulation of endothelial cell growth. The knockdown of CDK4 ends in similar results. The effect is caused by changes of CDK6 localization, less CDK6 is detected on the VEGF-A promoter. Bioinformatic analysis of human melanoma patient data verifies the key role of CDK6 in tumor angiogenesis in melanoma. The results highlight the importance of the delicate balance between CDK4 and CDK6 in regulating the cell cycle and transcription.

Interleukin-13 receptor \u03b12 is a novel marker and potential therapeutic target for human melanoma

Malignant melanoma is one of the untreatable cancers in which conventional therapeutic strategies, including chemotherapy, are hardly effective. Therefore, identification of novel therapeutic targets involved in melanoma progression is urgently needed for developing effective therapeutic methods. Overexpression of interleukin-13 receptor α2 (IL13Rα2) is observed in several cancer types including glioma and pancreatic cancer. Although IL13Rα2 is implicated in the progression of various types of cancer, its expression and roles in the malignant melanoma have not yet been elucidated. In the present study, we showed that IL13Rα2 was expressed in approximately 7.5% melanoma patients. While IL13Rα2 expression in human melanoma cells decreased their proliferation in vitro, it promoted in vivo tumour growth and angiogenesis in melanoma xenograft mouse model. We also found that the expression of amphiregulin, a member of the epidermal growth factor (EGF) family, was correlated with IL13Rα2 expression in cultured melanoma cells, xenograft tumour tissues and melanoma clinical samples. Furthermore, expression of amphiregulin promoted tumour growth, implicating causal relationship between the expression of IL13Rα2 and amphiregulin. These results suggest that IL13Rα2 enhances tumorigenicity by inducing angiogenesis in malignant melanoma, and serves as a potential therapeutic target of malignant melanoma.