Promotes Melanoma Cell Invasion Research Articles

Abstract 3602: The metastasis-suppressive function of intracellular galectin-3 in melanoma

Abstract Melanoma is a relatively rare skin cancer. However, it accounts for most of all skin cancer-related deaths worldwide. Once melanoma spreads to distant sites, it confers a poor prognosis characterized by resistance to therapy and high mortality rate. Hence, a favorable clinical outcome is strongly correlated with early diagnosis. Despite the ongoing research to identify novel diagnostic, prognostic, and therapeutic targets for metastatic melanoma (MM), a reliable serum marker to predict whether melanoma is vulnerable to metastasize or has already metastasized is still lacking. Galectin-3 (Gal-3), a ß-galactoside-binding protein, is widely expressed by many human epithelial and immune cells. High extracellular Gal-3 expression levels have been reported to be positively correlated with late-stage disease in melanoma patients, where it is theorized to bind surface glycosylated proteins to promote melanoma cell invasion and metastasis. Gal-3 is also expressed intracellularly where it participates in the regulation of many biological processes. However, intrinsic Gal-3 levels within the melanoma cell and its relationship to melanoma progression is still poorly understood. Using The Cancer Genome Atlas (TCGA) database, we analyzed the Gal-3 expression profiles of 471 tumor samples obtained from melanoma patients. To our surprise, TCGA data analysis has shown significantly higher expression of Gal-3 in primary melanoma samples compared to metastatic melanoma. We hypothesize that intracellular Gal-3 potentially negatively regulates primary melanoma progression to metastatic disease. Using several human melanoma cell lines silenced for Gal-3 expression, we investigated the corresponding malignancy-associated activities of these cells. Our results revealed that Gal-3 silencing in melanoma cells potentiated melanoma migration, invasion, and colony formation, compared with mock controls, suggesting that intracellular Gal-3 could interfere with melanoma metastatic activity. Moreover, loss of Gal-3 boosted the activation of the PI3K/AKT and MAPK signaling pathways and upregulated nuclear factor of activated T cells (NFAT1) expression and its pro-metastatic downstream target genes. Importantly, this study illuminates the apparent opposing roles of Gal-3 in melanoma progression, with intracellular Gal-3 potentially serving as a metastasis-suppressive molecule. Moreover, these studies reveal the potential of analyzing melanoma cell-intrinsic levels of Gal-3 to better predict metastatic potential and clinical outcome in melanoma patients. Citation Format: Norhan B. B. Mohammed, Charles J. Dimitroff. The metastasis-suppressive function of intracellular galectin-3 in melanoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3602.

FZD6 Promotes Melanoma Cell Invasion but Not Proliferation by Regulating Canonical Wnt Signaling and Epithelial‒Mesenchymal Transition

FZD6 is a key gene that controls tissue polarity during development. Increasing evidence suggests that it also plays active roles in various cancers. In this study, we show that FZD6 is overexpressed in multiple melanoma cell lines and human samples. Knockdown or knockout of FZD6 does not affect cell proliferation but significantly reduces the invasive ability of melanoma cells. In addition, we have found that knockout of Fzd6 dramatically reduces lung metastasis in the Pten/BRaf mouse model of melanoma. Mechanistic studies invitro and invivo reveal a surprising involvement of canonical Wnt signaling and epithelial‒mesenchymal pathway in the FZD6-mediated invasive phenotype. Together, our study supports a promoter role of FZD6 in melanoma progression.

LncRNA LNCOC1 is Upregulated in Melanoma and Serves as a Potential Regulatory Target of miR-124 to Suppress Cancer Cell Invasion and Migration

BackgroundA cascade of genes and pathways have been reported in the precise regulation of malignant melanoma (MM). Previous study has demonstrated that lncRNA LNCOC1 is an oncogenic factor in the pathogenesis and development of various cancers. The present study explored the functionalities of LNCOC1 and its interactions with miR-124 in MM.MethodsA total of 65 melanoma patients were enrolled in this study. The expression of LNCOC1 and miR-124 after cell transfection were detected by RT-qPCR. The migration rates of SK-MEL-3 and A375 cells after transient transfection with LNCOC1 expression vector and miR-124 mimic was detected by trans-well assay.ResultsLNCOC1 was accumulated to high levels in melanoma, and it was significantly correlated with the low survival rate of melanoma patients. Our bioinformatics data showed that miR-124 could target LNCOC1. Overexpression of miR-124 could downregulate LNCOC1. However, up-regulated the expression of LNCOC1 did not affect the expression of miR-124. Our correlation analysis also revealed that the expression of LNCOC1 and miR-124 were inversely correlated in both melanoma tissues and non-tumor tissues. The trans-well invasion and migration assays indicated that overexpression of miR-124 inhibited the melanoma cell invasion and migration. However, overexpression of LNCOC1 promoted melanoma cell invasion and migration.ConclusionLNCOC1 is upregulated in melanoma, which can be considered as a potential target of miR-124 in modulating melanoma cell invasion and migration. LNCOC1 may also be an interfering target of MM therapy.

Amelanotic B16-F10 Melanoma Compatible with Advanced Three-Dimensional Imaging Modalities

Amelanotic B16-F10 Melanoma Compatible with Advanced Three-Dimensional Imaging Modalities

Noncanonical EphA2 Signaling Is a Driver of Tumor-Endothelial Cell Interactions and Metastatic Dissemination in BRAF Inhibitor‒Resistant Melanoma

Acquired BRAF/MAPK/extracellular signal‒regulated kinase inhibitor resistance in melanoma results in a new transcriptional state associated with an increased risk of metastasis. In this study, we identified noncanonical ephrin receptor (Eph) EphA2 signaling as a driver of the resistance-associated metastatic state. We used mass spectrometry‒based proteomic and phenotypic assays to demonstrate that the expression of active noncanonical EphA2-S897E in melanoma cells led to a mesenchymal-to-amoeboid transition driven by Cdc42 activation. The induction of mesenchymal-to-amoeboid transition promoted melanoma cell invasion, survival under shear stress, adhesion to endothelial cells under continuous-flow conditions, increased permeability of endothelial cell monolayers, and stimulated melanoma transendothelial cell migration. Invivo, melanoma cells expressing EphA2-S897E or active Cdc42 showed superior lung retention after tail-vain injection. Analysis of BRAF inhibitor‒sensitive and ‒resistant melanoma cells demonstrated resistance to be associated with a mesenchymal-to-amoeboid transition switch, upregulation of Cdc42 activity, increased invasion, and transendothelial migration. The drug-resistant metastatic state was dependent on histone deacetylase 8 activity. Silencing of histone deacetylase 8 led to the inhibition of EphA2 and protein kinase B phosphorylation, reduced invasion, and impaired melanoma cell-endothelial cell interactions. In summary, we have demonstrated that the metastatic state associated with acquired BRAF inhibitor resistance is dependent on noncanonical EphA2 signaling, leading to increased melanoma-endothelial cell interactions and enhanced tumor dissemination.

RAB27A promotes melanoma cell invasion and metastasis via regulation of pro-invasive exosomes.

Despite recent advances in targeted and immune-based therapies, advanced stage melanoma remains a clinical challenge with a poor prognosis. Understanding the genes and cellular processes that drive progression and metastasis is critical for identifying new therapeutic strategies. Here, we found that the GTPase RAB27A was overexpressed in a subset of melanomas, which correlated with poor patient survival. Loss of RAB27A expression in melanoma cell lines inhibited 3D spheroid invasion and cell motility in vitro, and spontaneous metastasis in vivo. The reduced invasion phenotype was rescued by RAB27A-replete exosomes, but not RAB27A-knockdown exosomes, indicating that RAB27A is responsible for the generation of pro-invasive exosomes. Furthermore, while RAB27A loss did not alter the number of exosomes secreted, it did change exosome size and altered the composition and abundance of exosomal proteins, some of which are known to regulate cancer cell movement. Our data suggest that RAB27A promotes the biogenesis of a distinct pro-invasive exosome population. These findings support RAB27A as a key cancer regulator, as well as a potential prognostic marker and therapeutic target in melanoma.

Abstract 5167: Rab27a promotes melanoma cell invasion and metastasis via the regulation of exosome secretion

Abstract Introduction: The Rab GTPase family has been increasingly related to carcinogenesis and cancer biology during the past decade. In melanoma, Rab27a has been identified as a tumor dependency gene. Rab27a is thought to regulate exosome secretion in several cell types, however the exact role of Rab27a in melanoma biology and the underlying mechanisms are not well investigated. Experimental Procedures: To investigate the influence of Rab27a on melanoma biology and exosome secretion, Rab27a shRNA knockdown (KD) or CRISPR knockout (KO) was performed in human and murine melanoma cell lines. The effect of Rab27a loss on melanoma cell invasion and motility was analyzed by in vitro 3D spheroid invasion and live cell imaging. Rab27a function on melanoma metastasis was investigated using a mouse melanoma spontaneous metastasis model. Exosomes secreted by melanoma cell lines with/without Rab27a KD/KO were purified and characterized by electron microscopy, NanoSight analysis, BCA assay, western blotting and mass spectrometry. Results: Our results indicate that Rab27a loss in Rab27a high metastatic melanoma cell lines reduced 3D spheroid invasion and cell motility and Rab27a loss also reduced spontaneous melanoma metastasis in vivo. Rab27a KD invasion phenotype can be partially rescued by addition of exosomes from Rab27a replete cell conditioned media, but not exosomes derived from Rab27a KD cells. Loss of Rab27a does not alter the number of exosomes secreted from melanoma cells, but does alter exosome protein composition and morphology. Mass spectrometry analysis has shown that Rab27a replete cell secreted exosomes are more involved in regulating cell invasion and motility than the exosomes from Rab27a KD cells. Conclusion: In summary, Rab27a promotes the invasion and metastasis of a subset of melanoma cells via the regulation of pro-invasive exosomes, which indicates Rab27a as a potential therapeutic target for preventing melanoma progression. Citation Format: DAJIANG GUO, Goldie Y. Lui, Danae M. Sharp, Siew Li Lai, Shweta Tikoo, Rain Kwan, Michelle van Geldermalsen, Jeff Holst, Nikolas K. Haass, Wolfgang Weninger, Kimberley A. Beaumont. Rab27a promotes melanoma cell invasion and metastasis via the regulation of exosome secretion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5167.

1243 High Rab27a expression is associated with poor melanoma prognosis and promotes melanoma cell invasion and metastasis via regulation of pro-invasive exosomes

Despite recent advances in targeted and immune-based therapies, metastatic melanoma remains a clinical challenge with a poor prognosis. Understanding the genes and cellular processes that drive progression and metastasis are critical to identify new therapeutic strategies and improve treatment strategies and patient outcomes. Here, using clinical samples, we identified that Rab27a was overexpressed in a subset of melanomas, which correlated with poor survival. To further dissect the function of Rab27a in melanoma, we performed CRISPR-knockout and shRNA-knockdown of this gene in melanoma cell lines. We demonstrated that Rab27a loss inhibited proliferation, colony formation, 3D spheroid invasion and motility in vitro, as well as spontaneous metastasis in vivo. The reduced invasion phenotype observed with Rab27a knockdown was rescued by Rab27a-replete exosomes, indicating that exosomes drive Rab27a-mediated invasion. Further studies revealed that while Rab27a loss did not alter the number of exosomes secreted, there were changes in exosome morphology and the abundance of exosomal proteins associated with cancer cell migration and metastasis. These findings expand on a growing body of literature indicating important roles for Rab27a in regulating cancer cell biology, and further highlights its potential to be utilized as a clinical prognostic marker or therapeutic target in melanoma.

The convergent roles of CD271/p75 in neural crest-derived melanoma plasticity

The embryonic microenvironment is an important source of signals that promote multipotent cells to adopt a specific fate and direct cells along distinct migratory pathways. Yet, the ability of the embryonic microenvironment to retain multipotent progenitors or reprogram de-differentiated cells is less clear. Mistakes in cell differentiation or migration often result in developmental defects and tumorigenesis, including aggressive cancers that share many characteristics with embryonic progenitor cells. This is a striking feature of the vertebrate neural crest, a multipotent and highly migratory cell population first identified by His (1868) with the potential to metamorphose into aggressive melanoma cancer. In this perspective, we address the roles of CD271/p75 in tumor initiation, phenotype switching and reprogramming of metastatic melanoma and discuss the convergence of these roles in melanoma plasticity.

LKB1 loss cooperating with BRAF V600E promotes melanoma cell invasion and migration by up-regulation MMP-2 via PI3K/Akt/mTOR pathway.

The serine/threonine kinase LKB1, act as a tumor suppressor, has been reported in several sporadic cancers. However, how the loss of LKB1 promotes melanoma invasion and metastasis remains incompletely understood. In this study, we inactivated LKB1expression by RNA interference in BRAF mutation and wild type melanoma cells respectively. We found LKB1 inactivation cooperate with BRAF V600E lead to melanoma cells more aggressive by a series of experiments including wound scratch test, Transwell assay. While single alteration, either LKB1 loss or BRAF V600E, fails to enhance melanoma cells invasion ability. Mechanistically, LKB1 loss synergism with BRAF V600E resulted in the activation of the PI3K/Akt/mTOR signaling pathway and significant up-regulation expression of MMP-2. In addition, LKB1 expression in human melanoma tissues was negatively associated with MMP-2 expression in the presence of BRAF V600E. Thus, our findings indicate a probable explanation on LKB1 function as a tumor suppressor in melanoma and a new therapeutic strategy for melanoma by targeting on BRAF and LKB1 together.

The thiirane-based selective MT1-MMP/MMP2 inhibitor ND-322 reduces melanoma tumor growth and delays metastatic dissemination

MT1-MMP and MMP2 have been implicated as pro-tumorigenic and pro-metastatic factors in a wide variety of cancers including melanoma. We have previously demonstrated that MT1-MMP is highly expressed in melanoma where it promotes melanoma cell invasion and metastasis in part through the activation of its target MMP2. Given the accessibility of MMPs, as they are either secreted (e.g. MMP2) or membrane-tethered (e.g. MT1-MMP), they represent ideal targets for specific inhibition via small molecules. Here we show that the novel small-molecule inhibitor ND-322 with high selectivity for MT1-MMP and MMP2, effectively inhibits MT1-MMP and MMP2 activity resulting in reduced in vitro melanoma cell growth, migration and invasion. Importantly, these inhibitory effects lead to significant reduction of melanoma tumor growth and metastasis. We further show that while cell migration and invasion could be similarly hampered by specific inhibition of either MT1-MMP or MMP2 via shRNAs, the growth inhibitory activity of ND-322 could only be mirrored by specific inhibition of MT1-MMP. These data support ND-322 as a novel effective inhibitor capable of counteracting both MT1-MMP and MMP2, two key proteases involved in melanoma growth and metastasis. ND-322 may therefore represent a new inhibitor in the repertoire of treatments against melanoma.

Abstract A04: Aging microenvironment modulates melanoma invasion and metastasis

Abstract The incidence of melanoma rises dramatically after the age of 55. Due to an increase in aging population, it is important to study the change in molecular mechanisms due to aging that would allow development of therapies that are tailored to the age of the patients. The role of the tumor microenvironment in modulating cancer characteristics is widely recognized and it also provides targets for therapeutic intervention. Due to this, we hypothesized that changes in tumor microenvironment due to aging could affect the progression of the melanoma. We obtained skin fibroblasts from healthy donors aged 25-35, as well as skin fibroblasts from healthy donors aged 55-65. We cultured these fibroblasts and used conditioned media from them to affect the invasion of melanoma cells in 3D spheroid invasion assays, where aged fibroblasts promoted invasion of melanoma cells into collagen. We also built artificial skin (reconstructs) using young and aged fibroblasts and demonstrated that skin built with aged fibroblasts promoted melanoma cell invasion. Finally using a transgenic mouse model of melanoma (Yumm1.7, BRAFV600E/PTEN-/-) we observed that the injection of melanoma cells into the tail vein of aged mice (52 weeks) formed metastastic colonies much more rapidly than those injected into the tail vein of young mice (8 weeks). To study the factors involved in the aging microenvironment, we performed a proteomics study of the secretome from young and aged fibroblasts. From this study, we observed that aged fibroblasts secreted inhibitors of canonical Wnt signaling, as well as increased deposition of extracellular matrix components in the aging microenvironment. Since inhibition of canonical Wnt signaling has been linked to decreased sensitivity towards BRAF inhibitors in melanoma, we injected Yumm 1.7 cells subcutaneously into aged and young mice. These mice were then treated with BRAF inhibitors. We observed an increased resistance in response to therapy in the aged mice. We also prepared skin reconstruct from fibroblasts with knockdown of the proteins that we identified from secretome and treated them with PLX4720. These results indicated the role of these extracellular matrix proteins in melanoma. We are exploring the mechanisms of how these extracellular matrix proteins affect the sensitivity towards chemotherapeutics. We concluded that aging could alter tumor microenvironment thus resulting in increased metastasis and therapy resistance. It is important that the studies in cancer therapies take into account the age of the patient to achieve better response in patients. Citation Format: Amanpreet Kaur, Katie Marchbank, Vanessa Dang, Michael O'Connell, Marie Webster, Jessica Appleton, Phil Cheng, Alexander Valiga, Rachel Morissette, Nazli McDonnell, Luigi Ferrucci, Andrew Kossenkov, Katrina Meeth, Marcus Bosenberg, Hsin-Yao Tang, Xiangfan Yin, William Wood, III, Elin Lehrmann, Kevin Becker, Keith Flaherty, Dennie Frederick, Jennifer Wargo, Katherine Aird, Rugang Zhang, Xiaowei Xu, Qin Liu, David Speicher, Ashani Weeraratna. Aging microenvironment modulates melanoma invasion and metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Melanoma: From Biology to Therapy; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(14 Suppl):Abstract nr A04.

EIF4E Is an Adverse Prognostic Marker of Melanoma Patient Survival by Increasing Melanoma Cell Invasion

Human cutaneous melanoma is a devastating skin cancer because of its invasive nature and high metastatic potential. We used tissue microarray to study the role of human eukaryotic translation initiation factor 4E (eIF4E) in melanoma progression in 448 melanocytic lesions and found that high eIF4E expression was significantly increased in primary melanomas compared with dysplastic nevi (P<0.001), and further increased in metastatic melanomas (P<0.001). High eIF4E expression was associated with melanoma thickness (P=0.046), and poor overall and disease-specific 5-year survival of all, and primary melanoma patients, especially those with tumors ≥1 mm thick. Multivariate Cox regression analysis revealed that eIF4E is an independent prognostic marker. eIF4E knockdown (KD) in melanoma cells resulted in a significant increase in apoptosis (sub-G1 populations) and decrease in cell proliferation, and also resulted in downregulation of mesenchymal markers and upregulation of E-cadherin. In addition, eIF4E KD led to a decrease in melanoma cell invasion, matrix metalloproteinase-2 expression and activity, c-myc and BCL2 expression, and an increase in cleaved PARP and cleaved caspase-3 expression and chemosensitivity. Taken together, our data suggest that the eIF4E may promote melanoma cell invasion and metastasis, and may also serve as a promising prognostic marker and a potential therapeutic target for melanoma.

Abstract 3145: eIF4E, an adverse prognostic marker of melanoma patient survival, increases melanoma cell invasion

Abstract Human cutaneous melanoma is a life-threatening skin cancer due to its invasive nature and high metastatic potential, leading to poor prognosis for melanoma patients. However, the mechanisms for melanoma invasion and metastasis are poorly understood. Human eukaryotic translation initiation factor 4E (eIF4E) has been shown to be associated with tumor progression in multiple cancer types. However, the role of eIF4E in melanoma progression is not very well known. We examined eIF4E expression in 448 melanocytic lesions at different stages using tissue microarray and found that positive eIF4E staining was significantly increased in primary melanomas compared to dysplastic nevi (P&amp;lt;0.001), and further increased in metastatic melanomas compared to primary melanomas (P=0.008). EIF4E expression was correlated with melanoma thickness (P&amp;lt;0.001) and was inversely correlated with overall and disease-specific 5-year survival of all and primary melanoma patients especially those with tumor ≥4mm thick combined with metastatic melanoma patients. Furthermore, positive eIF4E expression was significantly higher in AJCC stage I-II melanomas compared to stage III-IV melanomas. Multivariate Cox regression analysis also revealed that eIF4E is an independent prognostic marker. FACS analysis and sulforhodamine B (SRB) cell proliferation assay showed that eIF4E knockdown in melanoma cells resulted in a significant increase and decrease in apoptosis and cell proliferation, respectively. EIF4E knockdown in melanoma cells also resulted in a down regulation of mesenchymal markers such as vimentin, N-cadherin, α-smooth muscle actin (α-SMA) and the EMT inducing transcription factor Twist. Additionally eIF4E knockdown in melanoma cells led to a decrease in the expression of c-Myc and Bcl2 and an increase in the expression of cleaved PARP and cleaved Caspase3. Moreover, down regulation of eIF4E resulted in a decrease in both melanoma cell invasion and MMP-2 activity. Taken together our data suggests the eIF4E may promote melanoma cell invasion and metastasis by inducing EMT and preventing apoptosis and also by increasing MMP-2 activity. EIF4E may also serve as a promising prognostic marker and a potential therapeutic target for melanoma. Citation Format: Shahram Khosravi, Gholamreza Safaee Ardekani, Magdalena Martinka, Christopher John Ong. eIF4E, an adverse prognostic marker of melanoma patient survival, increases melanoma cell invasion. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3145. doi:10.1158/1538-7445.AM2014-3145

SOX10 Promotes Melanoma Cell Invasion by Regulating Melanoma Inhibitory Activity

The transcription factor SOX10 (SRY (sex determining region Y)-box 10) has a key role in the embryonic development of melanocytes. Recently, it has been suggested that SOX10 is highly relevant for melanoma development and survival. However, the distinct functions and downstream targets of SOX10 in melanoma remain widely unknown. In this study, we inhibited SOX10 via RNA interference in different human melanoma cell lines and found a significantly reduced invasion capacity in vitro and in the chick embryo model. At later time points, SOX10 inhibition reduced proliferation and induced cell death. We identified melanoma inhibitory activity (MIA) as a direct target gene of SOX10, which is an essential protein for melanoma cell migration and invasion. Expression levels of SOX10 and MIA strictly correlated in melanoma cell lines, and SOX10 inhibition reduced MIA expression and promoter activity. Direct binding of SOX10 to the MIA promoter was demonstrated by electrophoretic mobility shift assay and chromatin immunoprecipitation. Ectopic expression of MIA in SOX10-inhibited melanoma cells restored the invasion capacity, supporting the hypothesis that MIA is responsible for SOX10-mediated melanoma cell invasion. Our data provide evidence for a critical role of SOX10 in melanoma cell invasion through the regulation of MIA and highlight its role as a therapeutic target in melanoma.

Angiopoietin-like 4 promotes melanoma cell invasion and survival through aldolase A.

In the present study, the association between angiopoietin-like 4 (ANGPTL4) and aldolase A (ALDOA) in human melanoma cell invasion and survival was investigated. Overexpression and knockdown of ANGPTL4 were respectively performed in WM-115 and WM-266-4 cells. ALDOA expression at both the mRNA and the protein levels as well as the ALDOA gene promoter activities were increased and decreased in parallel with overexpression and knockdown of ANGPTL4 in the melanoma cells, which was blocked by selective protein kinase C (PKC) inhibitor and restored by PKC agonist, respectively. ANGPTL4 overexpression significantly increased cell invasion and matrix metalloproteinase-2 (MMP-2) expression and decreased cell apoptosis against cisplatin in WM-115 cells, which was reversed by knocking down ALDOA. In WM-266-4 cells, knockdown of ANGPTL4 decreased cell invasion and MMP-2 expression and increased cell apoptosis against cisplatin, which was reversed by overexpression of ALDOA. In conclusion, this study demonstrates that ANGPTL4 upregulates ALDOA expression in human melanoma cells at the ALDOA gene promoter/transcriptional level through a PKC-dependent mechanism, and that ALDOA is a critical mediator of the promoting effect of ANGPTL4 on melanoma cell invasion, likely through upregulating the MMP-2 expression. Additionally, our results suggest that ALDOA plays an important role in ANGPTL4-enhanced melanoma cell survival against apoptotic stress, which implicates ANGPTL4 and ALDOA in the development of melanoma chemoresistance.

Osteopontin Promotes the Invasive Growth of Melanoma Cells by Activating Integrin αvβ3 and Down-Regulating Tetraspanin CD9

Overexpression of osteopontin (OPN) is strongly associated with the invasiveness/metastasis of many cancers, including melanomas. However, the molecular mechanisms of OPN in these processes remain poorly understood. We found that forced expression of OPN in early vertical-growth-phase melanoma cells dramatically increased their migration/invasion and growth/survival in a three-dimensional collagen I gel. Neutralizing antibodies to OPN, integrin β1, and integrin αvβ3, but not to CD44, negated the effects of OPN. Conversely, knocking down OPN in metastatic melanoma cells abrogated the invasive growth. OPN overexpression activated and OPN knockdown inactivated αvβ3 and αvβ5 integrins, negligibly affecting their expression. We further found OPN expression to inversely correlate with tetraspanin CD9 expression. Early-stage melanoma cells displayed low OPN and high CD9 expression, and conversely, metastatic cells displayed high OPN and low CD9 expression. Overexpression of OPN in vertical-growth-phase melanoma cells induced down-regulation of CD9, and knockdown of OPN in metastatic melanoma cells up-regulated CD9. Reversion of these CD9 changes abolished the effects of OPN. Furthermore, knockdown of CD9 in early-stage melanoma cells stimulated their invasive capacity in three-dimensional collagen. Similarly, microarray analyses of benign nevi and primary melanomas from different stages revealed an inverse correlation between OPN and CD9. These data suggest that OPN promotes melanoma cell invasion by activating integrin αvβ3 and down-regulating CD9, a putative metastasis suppressor.

Role of EIF5A2, a downstream target of Akt, in promoting melanoma cell invasion

Background:Cutaneous melanoma is a life-threatening skin cancer because of its poorly understood invasive nature and high metastatic potential. This study examines the importance of eukaryotic translation initiation factor 5A2 (EIF5A2) in melanoma pathogenesis.Methods:We examined EIF5A2 expression in 459 melanocytic lesions using tissue microarray. In addition, melanoma cell lines were subjected to invasion and cell proliferation assays, zymography, FACS and real-time PCR to investigate the role of EIF5A2 in cancer progression.Results:Positive EIF5A2 staining increased from dysplastic naevi to primary melanomas (PMs; P=0.001), and further increased in metastatic melanomas (P=0.044). Eukaryotic translation initiation factor 5A2 expression was correlated with melanoma thickness (P<0.001) and was inversely correlated with the 5-year survival of PM patients especially those with tumour⩽2 mm thick. Strikingly, none of the latter died within 5 years in EIF5A2-negative staining group. Cox regression analysis revealed that EIF5A2 is an independent prognostic marker. Further, we found that EIF5A2 is a novel downstream target of phosphorylated Akt. Both melanoma cell invasion and MMP-2 activity increased and decreased with EIF5A2 overexpression and knockdown, respectively.Conclusion:We for the first time showed that EIF5A2, as a target of PI3K/Akt, promotes melanoma cell invasion and may serve as a promising prognostic marker and a potential therapeutic target for melanoma.

Abstract 4307: Paradoxical activation of the MEK/ERK pathway promotes melanoma invasion and metastasis.

Abstract Melanoma is the most deadly form of skin cancer. An important feature of melanoma is its ability to metastasize and this contributes to its poor prognosis. RAS is mutated in ∼20% of melanomas and its downstream kinase BRAF is mutated in a further 50% of cases, these oncogenes regulate proliferation and survival through the MEK-ERK cascade. Selective inhibitors of BRAF such as vemurafenib have a remarkable clinical activity in patients with BRAF mutant melanomas with response rates of approximately 60-80%. In cells expressing activating BRAF mutations, vemurafenib blocks activation of the MAPK pathway. However, in cells expressing wild type BRAF and constitutively active upstream components that activate the MAPK pathway, BRAF inhibitors drive the paradoxical activation of this pathway. Here we show that kinase-dead BRAF promotes melanoma cell invasion and metastasis in the presence of oncogenic RAS. Notably, drugs that target BRAF mimic these effects and also induce RAS mutant melanoma cell invasion. The underlying mechanism is driven by paradoxical activation of the MEK-ERK pathway, resulting in increased secretion of the chemokine IL8 and subsequent secretion of extracellular matrix proteases, which induce invasion. We also show that BRAF inhibitors promote melanoma metastasis in an allograft model and that BRAF inhibitors induce invasion of drug-resistant BRAF mutant melanoma cells. We conclude that paradoxical activation of the MAPK pathway by BRAF inhibitors can drive melanoma invasion and metastasis in RAS mutant melanoma and in drug-resistant BRAF mutant melanoma cells. Citation Format: Berta Sanchez-Laorden, Amaya Viros, Maria Romina Girotti, Matthew Martin, Malin Pedersen, Alfonso Zambon, Dan Niculescu-Duvaz, Caroline Springer, Richard Marais. Paradoxical activation of the MEK/ERK pathway promotes melanoma invasion and metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4307. doi:10.1158/1538-7445.AM2013-4307

Abstract C51: c-Abl and Arg are activated in human primary melanomas, promote melanoma cell invasion, proliferation, survival, and drive metastatic progression

Abstract Despite 40 years of clinical trials, there has been little improvement in one-year survival rates for patients with metastatic melanoma, and the disease is essentially untreatable if not cured surgically. The paucity of chemotherapeutic agents that are effective for treating metastatic melanoma indicates a dire need to develop new therapies. Here, we found a previously unrecognized role for Abl kinases in melanoma progression. We demonstrate that Abl kinases (c-Abl, Arg) are activated in human melanoma cell lines, in primary melanomas (60%), and in a subset of benign nevi (33%). Using siRNA and pharmacological approaches, we show that c-Abl/Arg activation is functionally relevant because it is required for melanoma cell proliferation, survival, matrigel-invasion and single-cell 3D invasion. Moreover, active c-Abl transcriptionally upregulates MMP-1, and using rescue approaches we show that c-Abl promotes invasion via a STAT3-MMP-1 pathway. Conversely, active Arg drives invasion in a STAT3-independent manner, and upregulates MMP-3 and MT1-MMP, in addition to MMP-1. Paradoxically, c-Abl and Arg also increase expression of TIMP-1, a negative regulator of MMPs, both at the transcript and protein level via a STAT3-dependent pathway. In addition to negatively regulating MMPs, TIMPs also have anti-apoptotic functions, and high TIMP-1 expression is correlated with decreased survival and a poor clinical outcome in breast and colon cancer patients. Currently, we are in the process of testing whether c-Abl and Arg promote survival via induction of TIMP-1. Most importantly, we found that Abl kinases not only promote in vitro processes important for melanoma progression, but also promote metastasis in vivo, as inhibition of c-Abl/Arg with nilotinib dramatically inhibits lung colonization/metastasis in a mouse model using two different melanoma cell lines. Taken together, these data identify Abl kinases as critical, novel, drug targets in metastatic melanoma, and indicate that nilotinib may useful in preventing metastasis in patients with melanomas harboring active Abl kinases. Citation Format: Sourik S. Ganguly, Leann S. Fiore, Jonathan T. Sims, J Woodrow Friend, DivyaMani Srinivasan, Matthew Thacker, Michael L. Cibull, Wang Chi, Rina Plattner. c-Abl and Arg are activated in human primary melanomas, promote melanoma cell invasion, proliferation, survival, and drive metastatic progression. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C51.