Expression In Melanoma Cells Research Articles

Abstract 1146: Enhancer of zeste homolog 2 (EZH2) inhibition in metastatic melanoma promotes tumor regression in vivo

Abstract Melanoma is a deadly variety of skin cancer, which is responsible for three-fourths of skin cancer-related deaths, but constitutes less than 5% of all skin cancer cases. It has been estimated that in 2015, about 73,870 new cases of melanoma will be diagnosed in United States alone, of which 9,940 are expected to die. According to the ACS, melanoma is also the fastest growing cancer, which makes it essential to investigate the pathogenesis involved in the advanced stage of melanoma, and design effective therapeutics for its treatment. Drugs targeting epigenetic modifiers like EZH2 are becoming increasingly popular because of the fact that most epigenetic modifications and their effects can be reversed using these drugs. There has been no study till date investigating the role of EZH2 in melanoma. Our laboratory is investigating the role of EZH2 in the pathogenesis involved in the advanced stage of melanoma, to enable the design of effective therapeutic strategies for the treatment of melanoma. Here we investigate the relationship between EZH2 and tumor suppressors E-cadherin and RUNX3 in melanoma using matched melanoma cell lines (WM115 and WM266-4), formalin-fixed-paraffin-embedded (FFPE) patient tissue samples and in vivo xenograft model. The studies performed in cell lines and FFPE tissue samples suggested EZH2-mediated silencing of E-cadherin and RUNX3 by promoting H3K27-trimethylation of the E-CADHERIN and RUNX3 promoters in WM266-4 cells (metastatic; high EZH2; low E-cadherin) relative to WM115 cells (primary; low EZH2; high E-cadherin). Furthermore, we observed that EZH2 inhibition restores E-cadherin and RUNX3 expression in metastatic melanoma cells by reducing EZH2 and H3K27me3 occupancy at E-CADHERIN and RUNX3 promoters respectively. In addition, we found that inhibition of EZH2 besides inducing apoptosis and inhibiting cellular proliferation, also adversely affected invasion of metastatic melanoma. E-cadherin depletion had an opposite effect, suggesting that EZH2 mediated E-cadherin silencing promotes invasion in metastatic melanoma. In vivo, treatment of WM266-4 xenografts with EZH2 inhibitor resulted in significant reduction of tumor growth. In combination with Dabrafenib, this effect was highly synergistic. Analysis of harvested tumors indicated increased E-cadherin and RUNX3 levels in EZH2 inhibited group compared to vehicle, due to reduced H3K27me3 enrichment by EZH2 at E-cadherin and RUNX3 promoters, validating our in vitro finding. Tumor regression by combination therapy was also accompanied by significant increased pro-apoptotic proteins like Bak, Bax and decreased anti-apoptotic proteins Bcl-xL and Bcl-2. Hence, our findings suggest strong potential of EZH2 inhibitors as promising melanoma drugs either by itself (monotherapy), or in conjunction with other chemotherapeutics (combination therapy). Citation Format: Deepanwita Sengupta, Nathan Avaritt, Sara C. Shalin, Alan J. Tackett. Enhancer of zeste homolog 2 (EZH2) inhibition in metastatic melanoma promotes tumor regression in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1146.

Abstract 2351: Development of a B16F10 cell line expressing mNectin1 to study the activity of OncoVEXmGM-CSF in murine syngeneic melanoma models

Abstract Background: Talimogene laherparepvec is an oncolytic immunotherapy based on a modified herpes simplex virus type 1 (HSV-1), designed to kill neoplastic cells through two mechanisms: a) direct lysis and b) stimulation of a tumor antigen-specific adaptive immune response by way of GM-CSF expression. In order to support mechanism of action studies in a mouse melanoma model relevant to talimogene laherparepvec's approved U.S. indication, we expressed the HSV-1 entry receptor Nectin1 on B16F10 melanoma cells. B16F10 cells have previously been shown to be resistant to HSV-1 due to lack of entry receptor expression (Miller et al., Mol Ther, 2001). The goal of our work was to determine if mNectin1 expression in B16F10 melanoma cells renders them sensitive to talimogene laherparepvec treatment. For preclinical studies we used OncoVEXmGM-CSF, an HSV-1 modified similarly to talimogene laherparepvec except that murine GM-CSF is expressed instead of human GM-CSF. Herein we describe studies to assess the efficacy of OncoVEXmGM-CSF in a novel B16F10-mNectin1 syngeneic melanoma model. Methods: Parental B16F10 cells were transduced with lentivirus expressing either mNectin1, or eGFP as a control. In vitro sensitivity was determined by plating both cell types in 96-well plates, infecting with serially diluted OncoVEXmGM-CSF and then measuring ATP 72 hours later. For efficacy studies, B16F10 or B16F10-mNectin1 cells were injected subcutaneously on the right flank of female C57BL/6 mice. On day 10, mice were randomized into treatment groups based on tumor volume (n = 10/group). Talimogene laherparepvec was delivered intratumorally (5×106 PFU/dose,) every 3 days during the first week. Tumor growth and body weight were measured twice per week throughout the experiment. Survival analysis was performed using a Kaplan-Meier estimator. Results: B16F10 cells were insensitive to OncoVEXmGM-CSF up to 100 MOI (multiplicity of infection). In contrast, two other syngeneic cell lines, A20 and CT-26, showed MOI IC50 of 1 and 20. B16F10 cells expressing mNectin1 showed high sensitivity to OncoVEXmGM-CSF with an MOI IC50 of 0.01. In contrast, B16F10 cells expressing eGFP were insensitive up to an MOI of 100. In vivo, B16F10 mNectin1 cells showed a similar growth pattern as the parental B16F10 when injected subcutaneously. However, OncoVEXmGM-CSF treatment of B16F10-mNectin1 tumors caused a highly significant (p<0.0001) inhibition of tumor growth and increase in median overall survival compared to the control group. B16F10 mNectin1 tumors that grew during or following OncoVEXmGM-CSF treatment were shown to maintain mNectin1 expression suggesting other mechanisms of OncoVEXmGM-CSF resistance were involved. Conclusion: Expression of mNectin 1 in the B16F10 melanoma cell line confers sensitivity to OncoVEXmGM-CSF in vitro and extends median overall survival of mice bearing B16F10-muNectin1 tumors. Citation Format: Keegan Cooke, Juan Estrada, Jinghui Zhan, Petia Mitchell, Yannick Bulliard, Pedro J. Beltran. Development of a B16F10 cell line expressing mNectin1 to study the activity of OncoVEXmGM-CSF in murine syngeneic melanoma models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2351.

Abstract 765: The manipulation of FAP expression and its role in SDF-1 and IL-6 secretion by fibroblasts and melanoma cells

Abstract The cancer microenvironment surrounds tumors and primarily consists of fibroblasts and immune cells that cancer cells utiliaze to support their growth and invasion. Cancer-associated fibroblasts (CAFs) are the most prominent cell type in the microenvironment. They are attracted to tumors and activated by signals from cancer cells, including transforming growth factor-â (TGF-â). Following activation, CAFs display FAP on their surface, which breaks bonds in the extracellular matrix (ECM), creating space for cancer cells to migrate. CAFs also secrete cytokines, including stromal cell-derived factor-1 (SDF-1) and interleukin-6 (IL-6), to initiate this migration. This study seeks to determine if there is a link between the expression of fibroblast activation protein (FAP) and the specific production of SDF-1 and IL-6. Flow cytometry was used to verify the expression of FAP by the Malme-3 fibroblast cell line at an average rate of 50.6% and in the Malme-3M melanoma cell line at 4.8%. TGF-â treatment increased FAP expression in Malme-3M melanoma cells (50% increase), indicating a prominent role in cell transformation. siRNA transfection was also used to reduce FAP expression in both the fibroblasts (48.4% decrease) and the melanoma cells after initial TGF-â activation (11.6% decrease). Preliminary data from intracellular staining and ELISA analysis suggest that SDF-1 and IL-6 production both increased in melanoma cells in direct correlation to FAP expression in, but may be inversely related in fibroblasts. Future studies will further analyze the FAP expression levels and cytokine secretion of both cell types in different microenvironments to elucidate the relationship between FAP expression in cancer and the secretion of SDF-1 and IL-6. Citation Format: Zachary B. Fisher, Yuko J. Miyamoto. The manipulation of FAP expression and its role in SDF-1 and IL-6 secretion by fibroblasts and melanoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 765.

CD147 and matrix-metalloproteinase-2 expression in metastatic and non-metastatic uveal melanomas.

BackgroundExtracellular matrix remodelling regulated by matrix-metalloproteinase (MMP) inducer (CD147) is a crucial process during tumor cell invasion and regulation of blood supply. In this study, we evaluated the correlation of CD147 and MMP-2 expression with major prognostic factors for uveal melanoma and the development of metastasis.MethodsThe expression of CD147 and MMP-2 was analyzed in 49 samples of uveal melanomas. Triple immunofluorescence stainings using markers against glial cells (GFAP), endothelial cells (CD34) and macrophages (CD68) were performed to further analyse the exact localisation of CD147 and MMP-2 positivity. In 28 cases clinical metastatic disease were found. The remaining 21 cases showed no signs of metastatic disease for an average follow-up of 10 years. Correlation analysis (Pearson correlation) was performed to analyse the association of CD147 and MMP-2 expression with known prognostic factors, vasculogenic mimicry (VM), the mature vasculature (von Willebrand Factor) and tumor induced angiogenesis (by means of Endoglin expression).ResultsCD147 and MMP-2 were expressed in 47 (96.0 %) of the uveal melanomas. CD147 up-regulation was significantly correlated with a higher MMP-2 expression. The overall expression analysis revealed no significant difference in the metastatic (p = 0.777) and non-metastatic subgroup (p = 0.585). No correlation of CD147 expression and any system of blood supply was evident. In the non-metastatic sub-group a significant correlation of clustered CD147 positive cells with largest basal diameter (p = 0.039), height (p = 0.047) and TNM-stage (p = 0.013) was evident.ConclusionsThese data may indicate that CD147 regulates MMP-2 expression in uveal melanoma cells.

Endothelin-1 in the tumor microenvironment correlates with melanoma invasion.

Endothelin-1 (ET-1) is a vasoactive peptide that also plays a role in the tanning response of the skin. Animal and cell culture studies have also implicated ET-1 in melanoma progression, but no association studies have been performed to link ET-1 expression and melanoma in humans. Here, we present the first in-vivo study of ET-1 expression in pigmented lesions in humans: an ET-1 immunohistochemical screen of melanocytic nevi, melanoma in situ lesions, invasive melanomas, metastatic melanomas, and blue nevi was performed. Twenty-six percent of melanocytic nevi and 44% of melanoma in situ lesions demonstrate ET-1 expression in the perilesional microenvironment, whereas expression in nevus or melanoma cells was rare to absent. In striking contrast, 100% of moderately to highly pigmented invasive melanomas contained numerous ET-1-positive cells in the tumor microenvironment, with 79% containing ET-1-positive melanoma cells, confirmed by co-staining with melanoma tumor marker HMB45. Hypopigmented invasive melanomas had reduced ET-1 expression, suggesting a correlation between ET-1 expression and pigmented melanomas. ET-1-positive perilesional cells were CD68-positive, indicating macrophage origin. Sixty-two percent of highly pigmented metastatic melanomas demonstrated ET-1 expression in melanoma cells, in contrast to 28.2% of hypopigmented specimens. Eighty-nine percent of benign nevi, known as blue nevi, which have a dermal localization, were associated with numerous ET-1-positive macrophages in the perilesional microenvironment, but no ET-1 expression was detected in the melanocytes. We conclude that ET-1 expression in the microenvironment increases with advancing stages of melanocyte transformation, implicating a critical role for ET-1 in melanoma progression, and the importance of the tumor microenvironment in the melanoma phenotype.

Construction of a eukaryotic expression plasmid carrying the PKCI-1/HINT1 gene and its effects on apoptosis and autophagy of A375 melanoma cells

Objective To construct a eukaryotic expression plasmid carrying the PKCI-1/HINT1 gene, to investigate its expression in A375 melanoma cells after transfection, and to evaluate its effects on apoptosis and autophagy of A375 cells. Methods The PKCI-1/HINT1 gene sequence was amplified by reverse transcription PCR (RT-PCR)with total RNA extracted from A375 cells as the template, then inserted into the eukaryotic expression plasmid PCDNA3.1(+)to construct a recombinant plasmid, PCDNA3.1(+)-PKCI-1/HINT1. Some A375 cells were classified into two groups to be transiently transfected with the recombinant plasmid (PCDNA3.1 (+)-PKCI-1/HINT1 group)or the empty plasmid PCDNA3.1(+)(control group). After additional 48-hour culture, RT-PCR and Western blot analysis were performed to quantify the mRNA and protein expressions of PKCI-1/HINT1 respectively, Hoechst 33342 staining was conducted to detect apoptosis of A375 cells, Western blot analysis to detect the expressions of intracellular caspase-3 and autophagyassociated protein beclin1, and cell autophagy was observed by using the green fluorescent protein (GFP)microtubule-associated protein 1 light chain 3 (LC3)labelling method combined with confocal laser scanning microscopy. Methyl thiazolyl tetrazolium (MTT)assay was performed to evaluate the proliferative activity of A375 cells at 24, 48, 72 and 96 hours after transfection. Results Enzyme digestion and sequencing analysis confirmed that the eukaryotic expression plasmid PCDNA3.1(+)-PKCI-1/HINT1 was successfully constructed and effectively expressed in the transfected A375 cells. MTT assay showed that PKCI-1/HINT1 could obviously inhibit the proliferation of A375 cells, and the number of live cells was decreased by 17.0%, 25.6% and 29.4% in the PCDNA3.1(+)-PKCI-1/HINT1 group at 48, 72 and 96 hours, respectively, compared with the control group (all P < 0.05). Hoechest 33258 staining revealed that PKCI-1/HINT1 could promote the formation of apoptotic bodies in A375 cells. Confocal laser scanning microscopy demonstrated that the overexpression of PKCI-1/HINT1 increased GFP-LC3 puncta formation in A375 cells. In addition, Western blot analysis indicated that PKCI-1/HINT1 upregulated the protein expressions of caspase-3 and beclin1 in A375 cells. Conclusions The eukaryotic expression plasmid PCDNA3.1 (+ )-PKCI-1/HINT1 was successfully constructed, and PKCI-1/HINT1 could be effectively expressed in A375 cells. High-level expression of PKCI-1/HINT1 could suppress cellular proliferation, promote apoptosis, and induce autophagy, of A375 cells. Key words: Melanoma; Cell line, tumor; Apoptosis; Autophagy; PKCI-1/HINT1

Construction of Ang2-siRNA chitosan magnetic nanoparticles and the effect on Ang2 gene expression in human malignant melanoma cells.

The aim of the present study was to construct angiopoietin-2 (Ang2)-small interfering (si)RNA chitosan magnetic nanoparticles and to observe the interference effects of the nanoparticles on the expression of the Ang2 gene in human malignant melanoma cells. Ang2-siRNA chitosan magnetic nanoparticles were constructed and transfected into human malignant melanoma cells in vitro. Red fluorescent protein expression was observed, and the transfection efficiency was analyzed. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to assess the inhibition efficiency of Ang2 gene expression. Ang2-siRNA chitosan magnetic nanoparticles were successfully constructed, and at a mass ratio of plasmid to magnetic chitosan nanoparticles of 1:100, the transfection efficiency into human malignant melanoma cells was the highest of the ratios assessed, reaching 61.17%. RT-qPCR analysis showed that the magnetic chitosan nanoparticles effectively inhibited Ang2 gene expression in cells, and the inhibition efficiency reached 59.56% (P<0.05). Ang2-siRNA chitosan magnetic nanoparticles were successfully constructed. The in vitro studies showed that the nanoparticles inhibited Ang2 gene expression in human malignant melanoma tumor cells, which laid the foundation and provided experimental evidence for additional future in vivo studies of intervention targeting malignant melanoma tumor growth in nude mice.

Protein Tyrosine Phosphatase 4A3 (PTP4A3) Promotes Human Uveal Melanoma Aggressiveness Through Membrane Accumulation of Matrix Metalloproteinase 14 (MMP14).

To study PTP4A3 phosphatase and MMP14 metalloprotease synergy in uveal melanoma aggressiveness. Cell membrane localization of matrix metalloprotease 14 (MMP14) in uveal melanoma cells expressing protein tyrosine phosphatase A3 (PTP4A3) was assessed by flow cytometry or immunohistochemistry. The vesicular trafficking of MMP14 in the presence of PTP4A3 was evaluated in OCM-1 cells expressing either the wild-type or mutated phosphatase. Finally, MMP14 localization at the cell membrane of OCM-1 cells was impaired using RNA interference, and the PTP4A3-related migration in vitro and invasiveness in vivo of the treated cells were evaluated. We found that the membrane-anchored MMP14 is enriched at the cell surface of OCM-1 cells, patient-derived xenograft cells, and human primary uveal melanoma tumors expressing PTP4A3. Moreover, we show that PTP4A3 and MMP14 colocalize and that the vesicular trafficking of MMP14 is faster in the presence of active PTP4A3. Finally, we demonstrate that inhibition of MMP14 expression in uveal melanoma cells expressing PTP4A3 impairs their migration in vitro and invasiveness in vivo. Our observations indicate that PTP4A3 increases cell membrane accumulation of MMP14 as a result of increased cellular trafficking of the metalloprotease. We also show that downregulation of MMP14 expression reduced PTP4A3-induced cell migration and invasiveness. Taken together, our findings suggest that PTP4A3-related subcellular localization of MMP14 is an important event in metastasis induction.

Cooperative antiproliferative signaling by aspirin and indole-3-carbinol targets microphthalmia-associated transcription factor gene expression and promoter activity in human melanoma cells

Antiproliferative signaling of combinations of the nonsteroidal anti-inflammatory drug acetylsalicylic acid (aspirin) and indole-3-carbinol (I3C), a natural indolecarbinol compound derived from cruciferous vegetables, was investigated in human melanoma cells. Melanoma cell lines with distinct mutational profiles were sensitive to different extents to the antiproliferative response of aspirin, with oncogenic BRAF-expressing G361 cells and wild-type BRAF-expressing SK-MEL-30 cells being the most responsive. I3C triggered a strong proliferative arrest of G361 melanoma cells and caused only a modest decrease in the proliferation of SK-MEL-30 cells. In both cell lines, combinations of aspirin and I3C cooperatively arrested cell proliferation and induced a G1 cell cycle arrest, and nearly ablated protein and transcript levels of the melanocyte master regulator microphthalmia-associated transcription factor isoform M (MITF-M). In melanoma cells transfected with a -333/+120-bp MITF-M promoter-luciferase reporter plasmid, treatment with aspirin and I3C cooperatively disrupted MITF-M promoter activity, which accounted for the loss of MITF-M gene products. Mutational analysis revealed that the aspirin required the LEF1 binding site, whereas I3C required the BRN2 binding site to mediate their combined and individual effects on MITF-M promoter activity. Consistent with LEF1 being a downstream effector of Wnt signaling, aspirin, but not I3C, downregulated protein levels of the Wnt co-receptor LDL receptor-related protein-6 and β-catenin and upregulated the β-catenin destruction complex component Axin. Taken together, our results demonstrate that aspirin-regulated Wnt signaling and I3C-targeted signaling pathways converge at distinct DNA elements in the MITF-M promoter to cooperatively disrupt MITF-M expression and melanoma cell proliferation.

Melanocytes Affect Nodal Expression and Signaling in Melanoma Cells: A Lesson from Pediatric Large Congenital Melanocytic Nevi.

Expression of Nodal, a Transforming Growth Factor-beta (TGF-β) related growth factor, is associated with aggressive melanoma. Nodal expression in adult dysplastic nevi may predict the development of aggressive melanoma in some patients. A subset of pediatric patients diagnosed with giant or large congenital melanocytic nevi (LCMN) has shown increased risk for development of melanoma. Here, we investigate whether Nodal expression can help identify the rare cases of LCMN that develop melanoma and shed light on why the majority of these patients do not. Immunohistochemistry (IHC) staining results show varying degree of Nodal expression in pediatric dysplastic nevi and LCMN. Moreover, median scores from Nodal IHC expression analysis were not significantly different between these two groups. Additionally, none of the LCMN patients in this study developed melanoma, regardless of Nodal IHC levels. Co-culture experiments revealed reduced tumor growth and lower levels of Nodal and its signaling molecules P-SMAD2 and P-ERK1/2 when melanoma cells were grown in vivo or in vitro with normal melanocytes. The same was observed in melanoma cells cultured with melanocyte conditioned media containing pigmented melanocyte derived melanosomes (MDM). Since MDM contain molecules capable of inactivating radical oxygen species, to investigate potential anti-oxidant effect of MDM on Nodal expression and signaling in melanoma, melanoma cells were treated with either N-acetyl-l-cysteine (NAC), a component of the anti-oxidant glutathione or synthetic melanin, which in addition to providing pigmentation can also exert free radical scavenging activity. Melanoma cells treated with NAC or synthetic melanin showed reduced levels of Nodal, P-SMAD2 and P-ERK1/2 compared to untreated melanoma cells. Thus, the potential role for Nodal in melanoma development in LCMN is less evident than in adult dysplastic nevi possibly due to melanocyte cross-talk in LCMN capable of offsetting or delaying the pro-melanoma effects of Nodal via anti-oxidant effects of MDM.

Berberine-induced changes in protein expression and antioxidant enzymes in melanoma cells

Proteomic identification of differentially expressed proteins after treatment with berberine, a natural alkaloid, was investigated in this study. The 23 differentially expressed proteins, 3 of which were enhanced and 20 were reduced, were associated with diverse biological functions including cell death and molecular chaperone. The proteomic result was also validated by western blot analysis of ezrin, septin, UQCRC1 and elongation factor Tu. Moreover, changes in total activity and isozyme pattern of antioxidant enzymes were examined via activity assay and in-situ activity staining, respectively. Total activities of catalase and superoxide dismutase were enhanced, while those of glutathione peroxidase and glutathione reductase were unchanged by berberine. Taken together, the results showed that berberine elicited alteration of protein expression patterns and signaled the induction of isozyme of catalase and superoxide dismutase in melanoma cells.

Transketolase-like 1 ectopic expression is associated with DNA hypomethylation and induces the Warburg effect in melanoma cells.

BackgroundThe metabolism of cancer cells is often reprogrammed by dysregulation of metabolic enzymes. Transketolase-like 1 (TKTL1) is a homodimeric transketolase linking the pentose-phosphate pathway with the glycolytic pathway. It is generally silenced at a transcriptional level in somatic tissues. However, in human cancers its expression is associated with the acquisition of a glycolytic phenotype (the Warburg effect) by cancer cells that contributes to the progression of malignant tumors. In melanoma, defective promoter methylation results in the expression of genes and their products that can affect the tumor cell’s phenotype including the modification of immune and functional characteristics. The present study evaluates the role of TKTL1 as a mediator of disease progression in melanoma associated with a defective methylation phenotype.MethodsThe expression of TKTL1 in metastatic melanoma tumors and cell lines was analysed by qRT-PCR and immunohistochemistry. The promoter methylation status of TKTL1 in melanoma cells was evaluated by quantitative methylation specific PCR. Using qRT-PCR, the effect of a DNA demethylating agent 5-aza-2’-deoxycytidine (5aza) on the expression of TKTL1 was examined. Biochemical and molecular analyses such as glucose consumption, lactate production, invasion, proliferation and cell cycle progression together with ectopic expression and siRNA mediated knockdown were used to investigate the role of TKTL1 in melanoma cells.ResultsExpression of TKTL1 was highly restricted in normal adult tissues and was overexpressed in a subset of metastatic melanoma tumors and derived cell lines. The TKTL1 promoter was activated by hypomethylation and treatment with 5aza induced TKTL1 expression in melanoma cells. Augmented expression of TKTL1 in melanoma cells was associated with a glycolytic phenotype. Loss and gain of function studies revealed that TKTL1 contributed to enhanced invasion of melanoma cells.ConclusionsOur data provide evidence for an important role of TKTL1 in aerobic glycolysis and tumor promotion in melanoma that may result from defective promoter methylation. This epigenetic change may enable the natural selection of tumor cells with a metabolic phenotype and thereby provide a potential therapeutic target for a subset of melanoma tumors with elevated TKTL1 expression.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2185-5) contains supplementary material, which is available to authorized users.

What are the Therapeutic Implications of Increased Collagen Expression in Melanoma Cells Treated with Vemurafenib?

What are the Therapeutic Implications of Increased Collagen Expression in Melanoma Cells Treated with Vemurafenib?

Mismatch in epitope specificities between IFNγ inflamed and uninflamed conditions leads to escape from T lymphocyte killing in melanoma.

BackgroundA current focus in cancer treatment is to broaden responses to immunotherapy. One reason these therapies may prove inadequate is that T lymphocytes fail to recognize the tumor due to differences in immunogenic epitopes presented by the cancer cells under inflammatory or non-inflammatory conditions.The antigen processing machinery of the cell, the proteasome, cleaves proteins into peptide epitopes for presentation on MHC complexes. Immunoproteasomes in inflammatory melanomas, and in antigen presenting cells of the immune system, are enzymatically different to standard proteasomes expressed by tumors with no inflammation. This corresponds to alterations in protein cleavage between proteasome subtypes, and a disparate repertoire of MHC-presented epitopes.MethodsWe assessed steady state and IFNγ-induced immunoproteasome expression in melanoma cells. Using epitope specific T-lymphocyte clones, we studied processing and presentation of three NY-ESO-1 HLA-Cw3 restricted epitopes by melanoma cell lines. Our experimental model allowed comparison of the processing of three distinct epitopes from a single antigen presented on the same HLA complex. We further investigated processing of these epitopes by direct inhibition, or siRNA mediated knockdown, of the immunoproteasome catalytic subunit LMP7.ResultsOur data demonstrated a profound difference in the way in which immunogenic T-lymphocyte epitopes are presented by melanoma cells under IFNγ inflammatory versus non-inflammatory conditions. These alterations led to significant changes in the ability of T-lymphocytes to recognize and target melanoma cells.ConclusionsOur results illustrate a little-studied mechanism of immune escape by tumor cells which, with appropriate understanding and treatment, may be reversible. These data have implications for the design of cancer vaccines and adoptive T cell therapies.Electronic supplementary materialThe online version of this article (doi:10.1186/s40425-016-0111-7) contains supplementary material, which is available to authorized users.

Ubiquitin ligase UBE3C promotes melanoma progression by increasing epithelial-mesenchymal transition in melanoma cells.

Melanoma is the most aggressive type of skin cancer, exhibiting extensive local invasion and early distant metastasis. Aberrant expression of ubiquitin-protein ligase E3C (UBE3C) plays a key role in tumor development and progression. In the present study, we analyzed UBE3C expression in samples of cancerous and normal skin tissue. Levels of UBE3C expression were much higher in primary and metastatic melanoma tissues than in normal skin, cutaneous squamous cell carcinoma or basal cell carcinoma. Melanoma cells overexpressing UBE3C frequently exhibited a mesenchymal phenotype, including reduced expression of the epithelial marker E-cadherin and expression of the mesenchymal marker vimentin. Knockdown of UBE3C expression in melanoma cells significantly suppressed melanoma growth and progression. Furthermore, silencing UBE3C led to increased E-cadherin expression and decreased vimentin and Snail1 expression. Thus UBE3C promotes melanoma progression, possibly by inducing epithelial-mesenchymal transition in melanoma cells. Inhibiting UBE3C activity may suppress melanoma invasion and metastasis and may represent a targeted therapeutic approach.

Inhibition of oncogenic BRAF activity by indole-3-carbinol disrupts microphthalmia-associated transcription factor expression and arrests melanoma cell proliferation.

Indole-3-carbinol (I3C), an anti-cancer phytochemical derived from cruciferous vegetables, strongly inhibited proliferation and down-regulated protein levels of the melanocyte master regulator micropthalmia-associated transcription factor (MITF-M) in oncogenic BRAF-V600E expressing melanoma cells in culture as well as in vivo in tumor xenografted athymic nude mice. In contrast, wild type BRAF-expressing melanoma cells remained relatively insensitive to I3C anti-proliferative signaling. In BRAF-V600E-expressing melanoma cells, I3C treatment inhibited phosphorylation of MEK and ERK/MAPK, the down stream effectors of BRAF. The I3C anti-proliferative arrest was concomitant with the down-regulation of MITF-M transcripts and promoter activity, loss of endogenous BRN-2 binding to the MITF-M promoter, and was strongly attenuated by expression of exogenous MITF-M. Importantly, in vitro kinase assays using immunoprecipitated BRAF-V600E and wild type BRAF demonstrated that I3C selectively inhibited the enzymatic activity of the oncogenic BRAF-V600E but not of the wild type protein. In silico modeling predicted an I3C interaction site in the BRAF-V600E protomer distinct from where the clinically used BRAF-V600E inhibitor Vemurafenib binds to BRAF-V600E. Consistent with this prediction, combinations of I3C and Vemurafenib more potently inhibited melanoma cell proliferation and reduced MITF-M levels in BRAF-V600E expressing melanoma cells compared to the effects of each compound alone. Thus, our results demonstrate that oncogenic BRAF-V600E is a new cellular target of I3C that implicate this indolecarbinol compound as a potential candidate for novel single or combination therapies for melanoma. © 2016 Wiley Periodicals, Inc.

SOX9 indirectly regulates CEACAM1 expression and immune resistance in melanoma cells.

As melanoma cells are immunogenic, they instigate an adaptive immune response and production of anti-tumor T-cells. A central factor in this interaction is CEACAM1 (carcinoembryonic antigen cell adhesion molecule 1), a transmembrane glycoprotein previously shown in our lab to protect melanoma cells from T cell-mediated killing. In this study, we examine the role of transcription factor SOX9 in the regulation of CEACAM1 expression and immune resistance in melanoma cells. Knockdown of endogenous SOX9 results in CEACAM1 up-regulation, while its overexpression leads to the opposite effect. We show that SOX9 controls CEACAM1 expression at a transcriptional level, but in an indirect manner, as regulation of the CEACAM1 promoter remains intact even when all eight potential SOX9-binding sites are abolished. A series of promoter truncations localizes the SOX9-controlled area to the proximal 200bp of the promoter. Point mutations in putative Sp1 and ETS1 binding sites identify these transcription factors as the primary SOX9-controlled mediators. Co-immunoprecipitation studies show that SOX9 and Sp1 physically interact in melanoma cells, while silencing of SOX9 down-regulates ETS1, but not Sp1, in the same cells. Finally, knockdown of SOX9 indeed renders melanoma cells resistant to T cell-mediated killing, in line with the increased CEACAM1 expression. In conclusion, we show that SOX9 regulates CEACAM1 expression in melanoma cells, and thereby their immune resistance. As CEACAM1 is a pivotal protein in melanoma biology and immune crosstalk, further understanding of its regulation can provide new insights and contribute to the development of novel approaches to therapy.

Lentiviral-mediated overexpression of long non-coding RNA GAS5 reduces invasion by mediating MMP2 expression and activity in human melanoma cells.

The present study evaluated the effects of long non-coding RNA GAS5 on the migration and invasion of melanoma cells. Using the SK-Mel‑110 melanoma cell line, we stably expressed GAS5, visualized the distribution of GAS5 by RNA fluorescence in situ hybridization (FISH) and examined changes in cell migration and invasion with Transwell assays. In GAS5 overexpressed SK-Mel‑110 cells, migrated and invaded cells decreased by 65.3 and 55.6%, respectively. Moreover, the MMP2 protein level, and its activity was downregulated by 67.9 and 15.8%, respectively. Overexpressing lncRNA GAS5 inhibited the migration and invasion ability of melanoma SK-Mel‑110 cells, partially by decreasing the MMP2 expression and its activity. This study is the first to reveal a potential relationship between lncRNA GAS5 and the migration and invasion of melanoma.

RIG-I inhibits the MAPK-dependent proliferation of BRAF mutant melanoma cells via MKP-1

BackgroundBRAF-mutant melanoma is characterized by aggressive metastatic potential and therapeutic resistance. The innate immune receptor RIG-I has emerged as a potential target in melanoma therapies but the contributing pathways involved in anti-cancer activity are poorly characterized. MethodsBaseline and ATRA-induced expression of RIG-I in nine (3 wild type and 6 BRAF-mutant) melanoma cell lines was measured with Q-PCR and Western blot. Ligand-specific stimulation of RIG-I was detected by Q-PCR and ELISA. Activation of the RIG-I-coupled IRF3, NF-κB and MAPK pathways was tested with protein array and Western blot. Cell proliferation and apoptosis was monitored by flow cytometry and cell counting. Down modulation of MKP-1 expression in melanoma cells was performed by specific siRNA. ResultsShort-term ATRA pre-treatment increases the expression of RIG-I in BRAF-mutant melanoma cells. Specific activation of RIG-I by 5ʹppp-dsRNA leads to increased activity of the IRF3-IFNβ pathway but does not influence NF-κB signaling. RIG-I mediates the targeted dephosphorylation of several MAPKs (p38, RSK1, GSK-3α/β, HSP27) via the endogenous regulator MKP-1 resulting in decreased melanoma cell proliferation. ConclusionRIG-I has the potential to exert anticancer activity in BRAF-mutant melanoma via controlling IFNβ production and MAPK signaling. This is the first study showing that RIG-I activation results in MKP-1-mediated inhibition of cell proliferation via controlling the p38-HSP27, c-Jun and rpS6 pathways thus identifying RIG-I and MKP-1 as novel and promising therapeutical targets.

Epigallocatechin-3-O-gallate up-regulates microRNA-let-7b expression by activating 67-kDa laminin receptor signaling in melanoma cells.

MicroRNAs (miRNAs) are non-coding RNAs involved in various biological processes by regulating their target genes. Green tea polyphenol (−)-epigallocatechin-3-O-gallate (EGCG) inhibits melanoma tumor growth by activating 67-kDa laminin receptor (67LR) signaling. To examine the effect of EGCG on miRNA expression in melanoma cells, we performed miRNA microarray analysis. We showed that EGCG up-regulated miRNA-let-7b expression through 67LR in melanoma cells. The EGCG-induced up-regulation of let-7b led to down-regulation of high mobility group A2 (HMGA2), a target gene related to tumor progression. 67LR-dependent cAMP/protein kinase A (PKA)/protein phosphatase 2A (PP2A) signaling pathway activation was involved in the up-regulation of let-7b expression induced by EGCG. These findings provide a basis for understanding the mechanism of miRNA regulation by EGCG.