Regulation of gene expression in melanoma: New approaches for treatment

Novel MED15::ATF1 fusion in a pediatric melanoma with spitzoid features and aggressive presentation

Childhood melanoma is a rare and biologically heterogeneous pediatric malignancy. The differential diagnosis of pediatric melanoma is usually broad, including a wide variety of spindle cell or epithelioid neoplasms. Different molecular alterations affecting the MAPK and PI3K/AKT/mTOR pathways, tumor suppressor genes, and telomerase reactivation have been implicated in melanoma tumorigenesis and progression. Here, we report a novel MED15::ATF1 fusion in a pediatric melanoma with spitzoid features and an aggressive clinical course.

Measuring Melanoma Nanomechanical Properties in Relation to Metastatic Ability and Anti-Cancer Drug Treatment Using Scanning Ion Conductance Microscopy

A cell's mechanical properties have been linked to cancer development, motility and metastasis and are therefore an attractive target as a universal, reliable cancer marker. For example, it has been widely published that cancer cells show a lower Young's modulus than their non-cancerous counterparts. Furthermore, the effect of anti-cancer drugs on cellular mechanics may offer a new insight into secondary mechanisms of action and drug efficiency. Scanning ion conductance microscopy (SICM) offers a nanoscale resolution, non-contact method of nanomechanical data acquisition. In this study, we used SICM to measure the nanomechanical properties of melanoma cell lines from different stages with increasing metastatic ability. Young's modulus changes following treatment with the anti-cancer drugs paclitaxel, cisplatin and dacarbazine were also measured, offering a novel perspective through the use of continuous scan mode SICM. We found that Young's modulus was inversely correlated to metastatic ability in melanoma cell lines from radial growth, vertical growth and metastatic phases. However, Young's modulus was found to be highly variable between cells and cell lines. For example, the highly metastatic cell line A375M was found to have a significantly higher Young's modulus, and this was attributed to a higher level of F-actin. Furthermore, our data following nanomechanical changes after 24 hour anti-cancer drug treatment showed that paclitaxel and cisplatin treatment significantly increased Young's modulus, attributed to an increase in microtubules. Treatment with dacarbazine saw a decrease in Young's modulus with a significantly lower F-actin corrected total cell fluorescence. Our data offer a new perspective on nanomechanical changes following drug treatment, which may be an overlooked effect. This work also highlights variations in cell nanomechanical properties between previous studies, cancer cell lines and cancer types and questions the usefulness of using nanomechanics as a diagnostic or prognostic tool.

The pleiotropic role of galectin-3 in melanoma progression: Unraveling the enigma

Melanoma is a highly aggressive skin cancer with poor outcomes associated with distant metastasis. Intrinsic properties of melanoma cells alongside the crosstalk between melanoma cells and surrounding microenvironment determine the tumor behavior. Galectin-3 (Gal-3), a ß-galactoside-binding lectin, has emerged as a major effector in cancer progression, including melanoma behavior. Data from melanoma models and patient studies reveal that Gal-3 expression is dysregulated, both intracellularly and extracellularly, throughout the stages of melanoma progression. This review summarizes the most recent data and hypotheses on Gal-3 and its tumor-modulating functions, highlighting its role in driving melanoma growth, invasion, and metastatic colonization. It also provides insight into potential Gal-3-targeted strategies for melanoma diagnosis and treatment.

Establishment of a Zebrafish Xenograft Model for in Vivo Investigation of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a unique malignant tumor of the head and neck. Despite higher survival rates by the combination of radiotherapy and chemotherapy, the recurrence or metastasis of NPC still occurs at about 10%. Therefore, there is urgent demand to develop more effective in vivo models for preclinical trials to investigate the mechanisms of NPC development and progression and to explore better treatment approaches. In this study, we transplanted human NPC CNE1 cells into zebrafish embryos to establish a xenograft model of NPC, where the proliferation and invasion behaviors of NPC cells were investigated in vivo. Combining in vitro and in vivo analyses, we found that activating transcription factor 7 (ATF7) was involved in the occurrence and development of NPC regulated by peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1). The zebrafish NPC xenograft model established here thereby provides an in vivo tool for exploring the occurrence and development of NPC, which may help to identify new tumor markers and develop new therapeutic strategies for the treatment of NPC.

C-KIT Expression in Orbital Cavernous Venous Hemangiomas

Orbital (slow flow) cavernous venous hemangiomas (OCVH) are the most common benign orbital tumors in adults. The c-KIT is a tyrosine kinase receptor, which is expressed on several types of cells, is thought to play a key role in tumor pathogenesis. The purpose of this study was to evaluate the presence of the receptor c-KIT in OCVH. Our retrospective study examined 16 orbital cavernous venous hemangiomas from 16 cases operated on between 2006–2016 at Emek Medical Center. The mean tumor size was 18.4 mm. Symptoms appeared between 6 months and 22 years before operation. All specimens were analyzed for the c-KIT receptor through immunohistochemistry. The c-KIT was expressed by the endothelium in all 16 preparates. Staining was strong in two cases, moderate in six, and weak in eight cases, with no statistically significant correlation between staining and tumor size (p = 0.69) or the symptom duration (p = 0.15). We conclude that c-KIT may play an important role in the pathogenesis of OCVH. This pilot study is significant in that tumor-targeted therapy such as Imatinib Mesylate and Sunitinib may have a role in treating surgically complicated cases located in the orbital apex. A large multicenter collaborative study is necessary to examine the role of c-KIT in OCVH.

Genome-Wide Tiling Array Analysis of HPV-Induced Warts Reveals Aberrant Methylation of Protein-Coding and Non-Coding Regions

The human papillomaviruses (HPV) are a group of double-stranded DNA viruses that exhibit an exclusive tropism for squamous epithelia. HPV can either be low- or high-risk depending on its ability to cause benign lesions or cancer, respectively. Unsurprisingly, the majority of epigenetic research has focused on the high-risk HPV types, neglecting the low-risk types in the process. Therefore, the main objective of this study is to better understand the epigenetics of wart formation by investigating the differences in methylation between HPV-induced cutaneous warts and normal skin. A number of clear and very significant differences in methylation patterns were found between cutaneous warts and normal skin. Around 55% of the top-ranking 100 differentially methylated genes in warts were protein coding, including the EXOC4, KCNU, RTN1, LGI1, IRF2, and NRG1 genes. Additionally, non-coding RNA genes, such as the AZIN1-AS1, LINC02008, and MGC27382 genes, constituted 11% of the top-ranking 100 differentially methylated genes. Warts exhibited a unique pattern of methylation that is a possible explanation for their transient nature. Since the genetics of cutaneous wart formation are not completely known, the findings of the present study could contribute to a better understanding of how HPV infection modulates host methylation to give rise to warts in the skin.

Positive selection in Europeans and East-Asians at the ABCA12 gene

Natural selection acts on genetic variants by increasing the frequency of alleles responsible for a cellular function that is favorable in a certain environment. In a previous genome-wide scan for positive selection in contemporary humans, we identified a signal of positive selection in European and Asians at the genetic variant rs10180970. The variant is located in the second intron of the ABCA12 gene, which is implicated in the lipid barrier formation and down-regulated by UVB radiation. We studied the signal of selection in the genomic region surrounding rs10180970 in a larger dataset that includes DNA sequences from ancient samples. We also investigated the functional consequences of gene expression of the alleles of rs10180970 and another genetic variant in its proximity in healthy volunteers exposed to similar UV radiation. We confirmed the selection signal and refine its location that extends over 35 kb and includes the first intron, the first two exons and the transcription starting site of ABCA12. We found no obvious effect of rs10180970 alleles on ABCA12 gene expression. We reconstructed the trajectory of the T allele over the last 80,000 years to discover that it was specific to H. sapiens and present in non-Africans 45,000 years ago.

Mutations in Coagulation Factor VIII Are Associated with More Favorable Outcome in Patients with Cutaneous Melanoma

Coagulation factor VIII (FVIII), von Willebrand factor (VWF), and ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats 13) play an important role in the regulation of normal hemostasis. However, little is known about their roles in patients with malignancy, particularly with cutaneous melanoma. Whole genome sequencing data are available for 25,719 cases in 126 cancer genomic studies for analysis. All sequencing data and corresponding pathology findings were obtained from The Cancer Genome Atlas. The cBioPortal bioinformatics tools were used for the data analysis. Our results demonstrated that mutations in genes encoding FVIII , VWF , and ADAMTS13 were reported in 92 of 126 cancer genomic studies, and high mutation rates in these three genes were observed in patients with cutaneous melanoma from three independent studies. Moreover, high mutation rates in FVIII , VWF , and ADAMTS13 were also found in patients with diffuse large B cell lymphoma (22.9%), lung small cell carcinoma (20.7%), and colon adenocarcinoma (19.4%). Among 366 melanoma cases from TCGA provisional, the somatic mutation rates of FVIII , VWF , and ADAMTS13 in tumor cells were 15, 14, and 5%, respectively. There was a strong tendency for coexisting mutations of FVIII , VWF , and ADAMTS13 . Kaplan–Meier survival analysis demonstrated that melanoma patients with FVIII mutations had a more favorable overall survival rate than those without FVIII mutations ( p  = 0.02). These findings suggest, for the first time, that the FVIII mutation burden may have a prognostic value for patients with cutaneous melanoma. Further studies are warranted to delineate the molecular mechanisms underlying the favorable prognosis associated with FVIII mutations.

SOX5 is involved in balanced MITF regulation in human melanoma cells

Background

Melanoma is a cancer with rising incidence and new therapeutics are needed. For this, it is necessary to understand the molecular mechanisms of melanoma development and progression. Melanoma differs from other cancers by its ability to produce the pigment melanin via melanogenesis; this biosynthesis is essentially regulated by microphthalmia-associated transcription factor (MITF). MITF regulates various processes such as cell cycling and differentiation. MITF shows an ambivalent role, since high levels inhibit cell proliferation and low levels promote invasion. Hence, well-balanced MITF homeostasis is important for the progression and spread of melanoma. Therefore, it is difficult to use MITF itself for targeted therapy, but elucidating its complex regulation may lead to a promising melanoma-cell specific therapy.

Method

We systematically analyzed the regulation of MITF with a novel established transcription factor based gene regulatory network model. Starting from comparative transcriptomics analysis using data from cells originating from nine different tumors and a melanoma cell dataset, we predicted the transcriptional regulators of MITF employing ChIP binding information from a comprehensive set of databases. The most striking regulators were experimentally validated by functional assays and an MITF-promoter reporter assay. Finally, we analyzed the impact of the expression of the identified regulators on clinically relevant parameters of melanoma, i.e. the thickness of primary tumors and patient overall survival.

Results

Our model predictions identified SOX10 and SOX5 as regulators of MITF. We experimentally confirmed the role of the already well-known regulator SOX10. Additionally, we found that SOX5 knockdown led to MITF up-regulation in melanoma cells, while double knockdown with SOX10 showed a rescue effect; both effects were validated by reporter assays. Regarding clinical samples, SOX5 expression was distinctively up-regulated in metastatic compared to primary melanoma. In contrast, survival analysis of melanoma patients with predominantly metastatic disease revealed that low SOX5 levels were associated with a poor prognosis.

Conclusion

MITF regulation by SOX5 has been shown only in murine cells, but not yet in human melanoma cells. SOX5 has a strong inhibitory effect on MITF expression and seems to have a decisive clinical impact on melanoma during tumor progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-016-0170-0) contains supplementary material, which is available to authorized users.

Inhibition of NADPH oxidase 1 activity and blocking the binding of cytosolic and membrane-bound proteins by honokiol inhibit migratory potential of melanoma cells

Overexpression of NADPH oxidase 1 (Nox1) in melanoma cells is often associated with increased migration/metastasis rate. To develop effective treatment options, we have examined the effect of honokiol, a phytochemical from Magnolia plant, on the migratory potential of human melanoma cell lines (A375, Hs294t, SK-Mel119 and SK-Mel28) and assessed whether Nox1 is the target. Using an in vitro cell migration assay, we observed that treatment of different melanoma cell lines with honokiol for 24 h resulted in a dose-dependent inhibition of cell migration that was associated with reduction in Nox1 expression and reduced levels of oxidative stress. Treatment of cells with N-acetyl-L-cysteine, an anti-oxidant, also inhibited the migration of melanoma cells. Treatment of cells with diphenyleneiodonium chloride, an inhibitor of Nox1, significantly decreased the migration ability of Hs294t and SK-Mel28 cells. Further, we examined the effect of honokiol on the levels of core proteins (p22(phox) and p47(phox)) of the NADPH oxidase complex. Treatment of Hs294t and SK-Mel28 cells with honokiol resulted in accumulation of the cytosolic p47(phox) protein and decreased levels of the membrane-bound p22(phox) protein, thus blocking their interaction and inhibiting Nox1 activation. Our in vivo bioluminescence imaging data indicate that oral administration of honokiol inhibited the migration/extravasation and growth of intravenously injected melanoma cells in internal body organs, such as liver, lung and kidney in nude mice, and that this was associated with an inhibitory effect on Nox1 activity in these internal organs/tissues.

CXCR3 signaling in BRAFWT melanoma increases IL-8 expression and tumorigenicity

Patients with early stage, radial growth phase (RGP) melanoma have a 97% survival rate; however, when the melanoma progresses to the invasive vertical growth phase (VGP), survival rates decrease to 15%. The targets of many clinical trials are the known genetic and molecular mechanisms involved in melanoma progression, with the most common oncogenic mutation being the BRAF^V600E. However, less than half of melanomas harbor this mutation, and consequently, do not respond to the current BRAF targeted treatments. It is therefore critical to elucidate alternative mechanisms regulating melanoma progression. Increased expression of the chemokine receptor, CXCR3, on melanoma cells is correlated with increased metastasis and poor patient outcomes, suggesting a role for CXCR3 in the RGP to VGP transition. We found that endogenous CXCR3 can be induced in two RGP cell lines, BOWES (BRAF^WT) and WM35 (BRAF^V600E), with in vitro environmental stress and nutrient deprivation. Signaling via induced endogenous CXCR3 is linked with IL-8 expression in BOWES cells. Ectopic overexpression of CXCR3 in BOWES cells leads to increased ligand-mediated phERK, cellular migration, and IL-8 expression in vitro, and to increased tumorigenesis and lymph node metastasis in vivo. Our results demonstrate that, in BRAF^WT melanomas, CXCR3 signaling mediates significant increases in IL-8 expression, suggesting that CXCR3 expression and signaling may represent a transformative event that drives the progression of BRAF^WT melanomas. Implications: Expression of CXCR3 on BRAF^WT melanoma cells may be a mediator of melanoma progression.

Dendritic cell c-kit signaling and adaptive immunity: implications for the upper airways

PURPOSE OF REVIEW

Binding of the receptor tyrosine kinase, c-kit, to its ligand, stem cell factor (SCF), mediates numerous biological functions. Important roles for c-kit in hematopoiesis, melanogenesis, erythropoiesis, spermatogenesis, and carcinogenesis are well documented. Similarly, activation of mast cells and eosinophils by c-kit ligation has long been known to result in degranulation with concomitant release of pro-inflammatory mediators including cytokines. This review will highlight a recently discovered function of c-kit in regulating the adaptive immune responses with relevance to allergic diseases.

RECENT FINDINGS

Recent studies in a number of laboratories including our own highlight the previously unappreciated functions for c-kit in immunological processes. Increased expression of c-kit and its ligand, SCF, on dendritic cells by Th2/Th17-inducing stimuli leads to c-kit activation and immune skewing toward these subsets and away from Th1 responses. Treatment of dendritic cells with inhibitors of c-kit activation such as imatinib mesylate (Gleevec) induces breach of T-cell tolerance, skewing of responses toward Th1, and activation of natural killer cells.

SUMMARY

Taken together, these observations suggest that the c-kit/SCF axis may be a useful target for redirecting deleterious immune responses in various disease settings, including allergic diseases that are often associated with Th2 and Th17 responses.

Features of matrix metalloproteinase-2 expression in the nuclei of tumor cells of a skin melanoma

Goal of the study. To compare expression of matrix metalloproteinase-2 (MMP-2) in the nuclei and cytoplasm of tumor cells and assess the mutual relation between the localization of MMP-2 expression and different clinical and morphologic criteria in patients with a skin melanoma. Materials and methods. Tumor samples obtained from paraffin blocks taken from patients suffering from a skin melanoma and treated at the Krasnoyarsk Territorial Oncologic Dispensary served as the object of the study. Skin tissue samples taken from patients suffering from a skin melanoma (n = 44) were obtained from the Krasnoyarsk Territorial Pathological Anatomy Bureau. Immunohistochemistry was performed based on a standard technique using primary anti-matrix metalloproteinase-2 antibodies. Results. MMP-2 expression was revealed in the nuclei of tumor cells of a skin melanoma in 43.1% of cases and in the cytoplasm in 56.9% of cases. No significant differences in MMP-2 expression in the nuclei and cytoplasm were revealed (p = 0.33). Patients with nuclear expression in tumor cells are characterized by a more favorable prognosis than patients with cytoplasmic enzyme expression in tumor complexes. No dependence of the intracellular localization of MMP-2 expression on the patient sex or age, tumor localization, Clark level of invasion, Breslow’s thickness, particular features of tumor lymphocyte infiltration, tumor growth phase, histological subtype, pigmentation, tumor ulceration and tumor stage according to AJCC (American Joint Committee on Cancer) was revealed. Conclusion. MMP-2 located in the nuclei can be related to hypoxia in the tumor tissue as well as increased peroxynitrite level, which, in its turn, can have an effect on the function and regulation of matrix metalloproteinases. Moreover, MMP-2 with an atypical localization can be related to tumor cells with different biological characteristics within the same tumor, which characterize the intratumoral heterogeneity of neoplasms. The biological and clinical role of changes in the intracellular localization of the enzyme needs further explanation.

EGF-induced expression of Fused Toes Homolog (FTS) facilitates epithelial-mesenchymal transition and promotes cell migration in ME180 cervical cancer cells

The role of Fused Toes Homolog (FTS) in epidermal growth factor (EGF) induced epithelial-mesenchymal transition (EMT) in cervical cancer cells was studied. EGF treatment induced the change of EMT markers and increased cell migration. EGF treatment also increased phosphorylated EGFR and ERK and nuclear level of ATF-2. The binding of ATF-2 to the promoter region of FTS was evidenced after EGF treatment. Pretreatment with PD98059 and gefitinib prevented EGF-induced FTS expression. FTS silencing reduced EMT and cell migration by EGF treatment. These results demonstrate a novel function for FTS in EGF-mediated EMT process.

Gene therapy for advanced melanoma: selective targeting and therapeutic nucleic acids

Despite recent advances, the treatment of malignant melanoma still results in the relapse of the disease, and second line treatment mostly fails due to the occurrence of resistance. A wide range of mutations are known to prevent effective treatment with chemotherapeutic drugs. Hence, approaches with biopharmaceuticals including proteins, like antibodies or cytokines, are applied. As an alternative, regimens with therapeutically active nucleic acids offer the possibility for highly selective cancer treatment whilst avoiding unwanted and toxic side effects. This paper gives a brief introduction into the mechanism of this devastating disease, discusses the shortcoming of current therapy approaches, and pinpoints anchor points which could be harnessed for therapeutic intervention with nucleic acids. We bring the delivery of nucleic acid nanopharmaceutics into perspective as a novel antimelanoma therapeutic approach and discuss the possibilities for melanoma specific targeting. The latest reports on preclinical and already clinical application of nucleic acids in melanoma are discussed.

Hepatitis B virus regulation of Raf1 promoter activity through activation of transcription factor AP-2α

The X protein of hepatitis B virus (HBx) is one of the important factors in the development of hepatocellular carcinoma. Raf1 kinase is a central component of many signaling pathways that are involved in normal cell growth and oncogenic transformation. We previously demonstrated that hepatitis B virus regulates Raf1 expression in HepG2.2.15 cells by enhancing its promoter activity and that HBx and HBs might play an important role in this process. However, the underlying molecular mechanisms remain unclear. In this study, we show that nucleotides -209 to -133 of the Raf1 promoter sequence constitute the core region where hepatitis B virus is regulated. This regulation was found to require the involvement of cis-regulatory element AP-2α. We further demonstrated that AP-2α expression was higher in HepG2.2.15 cells (HBV-expressing cells) than in HepG2 cells in vitro. Silencing AP-2α expression by siRNA significantly inhibited the Raf1 promoter activity in HepG2.2.15 cells. These findings indicated that HBV regulates Raf1 promoter activity, possibly through AP-2α.

Network motifs in the transcriptional regulation network of cervical carcinoma cells respond to EGF

PURPOSE

Cervical carcinoma is the second most prevalent and the fifth most deadly malignancy seen in women worldwide. Dysregulated activation of EGF ErbB system has been implicated in diverse types of human cancer; however, it is elusive how it is regulated in human cervical cancer cells. We herein aimed to explore the mechanisms of cervical carcinoma response to epidermal growth factor (EGF), with a view of the pathways activated by EGF.

METHODS

Using the GSE6783 affymetrix microarray data accessible from gene expression omnibus database, we first identified the differentially expressed genes between EGF-stimulated and -unstimulated samples. Then we constructed a regulation network and identified the network motifs. We also performed biological process and pathway enrichment analyses to functionally classify the genes in the regulation network.

RESULTS

A total of 11 network motifs were identified in the regulation network. EGF treatment could increase the risk of cancer via dysregulation of cancer-related pathways and immune response pathways.

CONCLUSIONS

Network motif analysis is useful in mining the useful information underlying the network. We hope our work could serve as a basis for further experimentation.

NADPH oxidase 1 overexpression enhances invasion via matrix metalloproteinase-2 and epithelial-mesenchymal transition in melanoma cells

NADPH oxidase 1 (Nox1) is a member of the NADPH oxidase family that has not been well characterized in the melanocytic cell lineage. Here we demonstrated that Nox1 and Nox4 were detected in melanocytic lineage, with only Nox1 detected in normal human melanocytes and Nox4 in a subset of metastatic melanoma cell lines. The protein level and enzymatic activity of Nox1 was elevated in all melanoma cells as compared with normal melanocytes. Overexpression of GFP-Nox1 protein in Wm3211 primary melanoma cells increased invasion rate by 4- to 6-fold as measured by Matrigel invasion assay, whereas knocking down or inhibiting Nox1 decreased invasion by approximately 40-60% in Wm3211 and SK-Mel-28 cells. Matrix metalloproteinase-2 (MMP-2) was increased by Nox1 overexpression at the mRNA, protein, and activity levels, and decreased by Nox1 knockdown. MMP-2 promoter activity was also regulated by Nox1 knockdown. In addition, stable clones overexpressing Nox1 exhibited an epithelial-mesenchymal transition (EMT) as examined by cell morphology and EMT markers; knockdown or inhibiting Nox1 led to a reversal of EMT. Supplementing MMP-2 to culture media did not induce EMT, suggesting that EMT induction by Nox1 was not through MMP-2 upregulation. In summary, Nox1 was overexpressed in all melanoma cell lines examined, and enhanced cell invasion by MMP-2 upregulation and EMT induction.

Aberrant expressions of AP-2α splice variants in pancreatic cancer

OBJECTIVES

The present study was conducted to evaluate the expression and function of AP-2α isoforms in pancreatic ductal adenocarcinoma.

METHODS

The expression of AP-2α was evaluated at the RNA level by reverse transcription-polymerase chain reaction and at the protein level by Western blotting and immunofluorescence. Its function as a transcription factor was evaluated in transient transfection experiments: DNA binding properties by electromobility shift assay and transactivation capabilities by luciferase assay.

RESULTS

Multiple alternative splicing events of AP-2α messenger occurred in all human pancreatic cancer cell lines, including a novel isoform, termed variant 6, which was not present in HeLa cells. At the protein level, except for 1 cell line, all pancreatic cancer cell lines expressed high nuclear levels of AP-2α. We also showed that AP-2α expressed by the pancreatic cancer cell lines could bind its cognate recognition site and activate transcription. However, variant 6, although not able to activate transcription, did not act in a dominant negative manner when cotransfected with the full-length protein.

CONCLUSIONS

Multiple isoforms of AP-2α are highly expressed in pancreatic cancer cell lines including a new isoform, AP-2α variant 6, which seems to be pancreatic cancer specific and is deprived of transcriptional activity.

Transcriptional control of melanoma metastasis: the importance of the tumor microenvironment

The molecular changes associated with the transition of melanoma cells from radial growth phase (RGP) to vertical growth phase (VGP) and the metastatic phenotype are not very well defined. However, some of the genes involved in this process and their transcriptional regulation are beginning to be elucidated. For example, the switch from RGP to VGP and the metastatic phenotype is associated with loss of the AP-2α transcription factor. AP-2α regulates the expression of c-KIT, MMP-2, VEGF, and the adhesion molecule MCAM/MUC18. Recently, we reported that AP-2α also regulates two G-protein coupled receptors (GPCRs) PAR-1 and PAFR. In turn, the thrombin receptor, PAR-1, regulates the expression of the gap junction protein Connexin-43 and the tumor suppressor gene Maspin. Activation of PAR-1 also leads to overexpression and secretion of proangiogenic factors such as IL-8, uPA, VEGF, PDGF, as well certain integrins. PAR-1 also cooperates with PAFR to regulate the expression of the MCAM/MUC18 via phosphorylation of CREB. The ligands for these GPCRs, thrombin and PAF, are secreted by stromal cells, emphasizing the importance of the tumor microenvironment in melanoma metastasis. The metastatic phenotype of melanoma is also associated with overexpression and function of CREB/ATF-1. Loss of AP-2α and overexpression of CREB/ATF-1 results in the overexpression of MCAM/MUC18 which by itself contributes to melanoma metastasis by regulating the inhibitor of DNA binding-1 (Id-1). CREB/ATF-1 also regulates the angiogenic factor CYR-61. Our recent data indicate that CREB/ATF-1 regulates the expression of AP-2α, thus, supporting the notion that CREB is an important "master switch" in melanoma progression.

CREB inhibits AP-2alpha expression to regulate the malignant phenotype of melanoma

BACKGROUND

The loss of AP-2alpha and increased activity of cAMP-responsive element binding (CREB) protein are two hallmarks of malignant progression of cutaneous melanoma. However, the molecular mechanism responsible for the loss of AP-2alpha during melanoma progression remains unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Herein, we demonstrate that both inhibition of PKA-dependent CREB phosphorylation, as well as silencing of CREB expression by shRNA, restored AP-2alpha protein expression in two metastatic melanoma cell lines. Moreover, rescue of CREB expression in CREB-silenced cell lines downregulates expression of AP-2alpha. Loss of AP-2alpha expression in metastatic melanoma occurs via a dual mechanism involving binding of CREB to the AP-2alpha promoter and CREB-induced overexpression of another oncogenic transcription factor, E2F-1. Upregulation of AP-2alpha expression following CREB silencing increases endogenous p21(Waf1) and decreases MCAM/MUC18, both known to be downstream target genes of AP-2alpha involved in melanoma progression.

CONCLUSIONS/SIGNIFICANCE

Since AP-2alpha regulates several genes associated with the metastatic potential of melanoma including c-KIT, VEGF, PAR-1, MCAM/MUC18, and p21(Waf1), our data identified CREB as a major regulator of the malignant melanoma phenotype.

Erythropoietin is involved in angiogenesis in human primary melanoma

In this study, the extent of angiogenesis, evaluated as microvascular volume density, immunoreactivity of tumour cells to erythropoietin (Epo) and of endothelial cells to Epo receptor (EpoR) have been correlated in human primary melanoma specimens. Results showed that Epo/EpoR expression correlate with angiogenesis and tumour thickness. These findings suggest that Epo is secreted by tumour cells and it affects vascular endothelial cells via its receptor and promotes angiogenesis in a paracrine manner, playing an important role in melanoma angiogenesis.

Signaling of c-kit in dendritic cells influences adaptive immunity

The binding of the receptor tyrosine kinase, c-kit, to its ligand, stem cell factor (SCF), mediates numerous biological functions. Important roles for c-kit in hematopoiesis, melanogenesis, erythropoiesis, spermatogenesis, and carcinogenesis are well documented. Similarly, activation of granulocytes, mast cells, and of eosinophils in particular, by c-kit ligation has long been known to result in degranulation with concomitant release of pro-inflammatory mediators, including cytokines. However, recent work from a number of laboratories, including our own, highlights previously unappreciated functions for c-kit in immunologic processes. These novel findings strongly suggest that signaling through the c-kit-SCF axis could have a significant impact on the pathogenesis of diseases associated with an immunologic component. In our own studies, c-kit upregulation on dendritic cells via T helper (Th)2- and Th17-inducing stimuli led to c-kit activation and immune skewing toward these T helper subsets and away from Th1 responses. Others have shown that dendritic cell treatment with inhibitors of c-kit activation, such as imatinib mesylate (Gleevec), favored breaking of T-cell tolerance, skewing of responses toward production of Th1 cytokines, and activation of natural killer cells. These data all indicate that deeper understanding of, and ability to control, the c-kit-SCF axis could lead to improved treatment modalities aimed at redirecting unwanted and/or deleterious immune responses in a wide variety of conditions.

Functional activity of CXCL8 receptors, CXCR1 and CXCR2, on human malignant melanoma progression

We examined the autocrine/paracrine role of interleukin-8 (CXCL8) and the functional significance of CXCL8 receptors, CXCR1 and CXCR2, in human malignant melanoma proliferation, migration, invasion and angiogenesis. We found that a panel of seven cell lines, even though at different extent, secreted CXCL8 protein, and expressed CXCR1 and CXCR2 independently from the CXCL8 expression, but depending on the oxygen level. In fact, hypoxic exposure increases the expression of CXCR1 and CXCR2. The cell proliferation of both M20 and A375SM lines, expressing similar levels of both CXCR1 and CXCR2 but secreting low and high amounts of CXCL8, respectively, was significantly enhanced by CXCL8 exposure and reduced by CXCL8, CXCR1 and CXCR2 neutralising antibodies, indicating the autocrine/paracrine role of CXCL8 in melanoma cell proliferation. Moreover, an increased invasion and migration in response to CXCL8 was observed in several cell lines, and a further enhancement evidenced under hypoxic conditions. A CXCL8-dependent in vivo vessel formation, evaluated through a matrigel assay, was also demonstrated. Furthermore, when neutralising antibodies against CXCR1 or CXCR2 were used, only the involvement of CXCR2, but not CXCR1 was observed on cell migration and invasion, while both receptors played a role in angiogenesis. In summary, our data demonstrate that CXCL8 induces cell proliferation and angiogenesis through both receptors and that CXCR2 plays an important role in regulating the CXCL8-mediated invasive and migratory behaviour of human melanoma cells. Thus, blocking the CXCL8 signalling axis promises an improvement for the therapy of cancer and, in particular, of metastatic melanoma.

RIOK3 interacts with caspase-10 and negatively regulates the NF-kappaB signaling pathway

RIOK3 was initially characterized as a homolog of Aspergillus nidulans sudD and showed down-regulation at the invasive front of malignant melanomas, but the molecular mechanism remains elusive. Here, we report that overexpression of RIOK3 inhibits TNFalpha-induced NF-kappaB activation, but down-regulation of endogenous RIOK3 expression by siRNA potentiates it. A yeast two-hybrid experiment revealed that RIOK3 interacted with caspase-10, and further, a GST pull-down assay and endogenous coimmunoprecipitation validated the interaction. We subsequently showed that the interaction was mediated by the RIO domain of RIOK3 and each death effector domain of caspase-10. Interestingly, our data demonstrated that RIOK3 suppressed caspase-10-mediated NF-kappaB activation by competing RIP1 and NIK to bind to caspase-10. Importantly, the kinase activity of RIOK3 was confirmed to be relevant to NF-kappaB signaling. Taken together, our findings strongly suggest that RIOK3 negatively regulates NF-kappaB signaling pathway activated by TNFalpha dependent on its kinase activity and NF-kappaB signaling pathway activated by caspase-10 independent of its kinase activity.

Tumor immunotherapy in melanoma: strategies for overcoming mechanisms of resistance and escape

The incidence of melanoma has been steadily increasing over the last 3 decades. Currently, there are several approved treatments for metastatic melanoma, including chemotherapy and biologic therapy as both single treatments and in combination, but none is associated with a significant increase in survival. The chemotherapeutic agent dacarbazine is the standard treatment for metastatic melanoma, with a response rate of 15-20%, although most responses are not sustained. One of the main problems with melanoma treatment is chemotherapeutic resistance. The mechanisms of resistance of melanoma cells to chemotherapy have yet to be elucidated. Following treatment with dacarbazine, melanoma cells activate the extracellular signal-regulated kinase pathway, which results in over-expression and secretion of interleukin (IL)-8 and vascular endothelial growth factor. Melanoma cells utilize this mechanism to escape from the cytotoxic effect of the drug. We have previously reported on the development of fully human neutralizing antibodies against IL-8 (anti-IL-8-monoclonal-antibody [ABX-IL8]). In preclinical studies, ABX-IL8 inhibited tumor growth, angiogenesis, and metastasis of human melanoma in vivo. We propose that combination treatment with dacarbazine and IL-8 will potentiate the cytotoxic effect of the drug. Furthermore, formation of metastasis is a multistep process that includes melanoma cell adhesion to endothelial cells. Melanoma cell adhesion molecule (MUC18) mediates these processes in melanoma and is therefore a good target for eliminating metastasis. We have developed a fully human antibody against MUC18 that has shown promising results in preclinical studies. Since resistance is one of the major obstacles in the treatment of melanoma, we propose that utilization of antibodies against IL-8 or MUC18 alone, or as part of a 'cocktail' in combination with dacarbazine, may be a new treatment modality for metastatic melanoma that overcomes resistance of the disease to chemotherapy and significantly improves survival of patients.

The cinnamon-derived Michael acceptor cinnamic aldehyde impairs melanoma cell proliferation, invasiveness, and tumor growth

Redox dysregulation in cancer cells represents a chemical vulnerability that can be targeted by pro-oxidant redox intervention. Dietary constituents that contain an electrophilic Michael acceptor pharmacophore may therefore display promising chemopreventive and chemotherapeutic anti-cancer activity. Here, we demonstrate that the cinnamon-derived dietary Michael acceptor trans-cinnamic aldehyde (CA) impairs melanoma cell proliferation and tumor growth. Feasibility of therapeutic intervention using high doses of CA (120 mg/kg, po, daily, 10 days) was demonstrated in a human A375 melanoma SCID mouse xenograft model. Low-micromolar concentrations (IC(50)< 10 microM) of CA, but not closely related CA derivatives devoid of Michael acceptor activity, suppressed proliferation of human metastatic melanoma cell lines (A375, G361, LOX) with G1 cell-cycle arrest, elevated intracellular ROS, and impaired invasiveness. Expression array analysis revealed that CA induced an oxidative stress response in A375 cells, up-regulating heme oxygenase 1, sulfiredoxin 1 homolog, thioredoxin reductase 1, and other genes, including the cell-cycle regulator and stress-responsive tumor suppressor gene cyclin-dependent kinase inhibitor 1A, a key mediator of G1-phase arrest. CA, but not Michael-inactive derivatives, inhibited NF-kappaB transcriptional activity and TNFalpha-induced IL-8 production in A375 cells. These findings support a previously unrecognized role of CA as a dietary Michael acceptor with potential anti-cancer activity.

Emerging functions of c-kit and its ligand stem cell factor in dendritic cells: regulators of T cell differentiation

The receptor tyrosine kinase, c-kit, and its ligand, stem cell factor (SCF), function in a diverse range of biological functions. The role of c-kit in the maintenance and survival of hematopoietic stem cells and of mast cells is well recognized. c-kit also plays an important role in melanogenesis, erythropoiesis and spermatogenesis. Recent work from our laboratory highlights an important role of c-kit in the regulation of expression of two molecules in dendritic cells (DCs), interleukin-6 (IL-6) and Jagged-2 (a ligand of Notch), which are known to regulate T helper cell differentiation. Our study shows that induction of c-kit expression and its signaling in DCs promotes Th2 and Th17 responses but not Th1 response. c-kit inhibition by imatinib mesylate (Gleevec) in DCs was previously shown to promote natural killer cell activation which may be due to dampening of IL-6 production by the DCs. Since dysregulation of c-kit function has been associated with various disease states including cancer, in this perspective we have focused on known and novel functions of c-kit to include molecules such as IL-6 and Notch that were not previously recognized to be within the purview of c-kit biology. We have also reviewed the differential expression pattern of SCF and c-kit on various cell types and its variation during development or pathology. The recognition of previously unappreciated roles for c-kit will provide better insights into its function within and beyond the immune system and pave the way for developing better therapeutic strategies.

Ceramide inhibition of MMP-2 expression and human cancer bronchial cell invasiveness involve decreased histone acetylation

Ceramides have been proposed as potential therapeutic strategy with regard to their ability to induce cell death. We previously demonstrated that C2-ceramide generated apoptosis in bronchocarcinoma BZR cells. We here investigated whether ceramides also target other molecules involved in cell-cell or cell-matrix interactions during cancer progression. A SuperArray(R) analysis showed that ceramides modulate gene expression after 2 h. Among deregulated genes, we observed an inhibition of the transcript coding for the pro-metastatic enzyme MMP-2. The pharmacological inhibitor of caspases cascade, ZVAD-fmk, did not prevent C2-ceramide-induced down-regulation of MMP-2 ruling out apoptosis as a mediator of this event, whereas inhibition of oxidative stress using NAC confirmed a role for ROS. This effect of C2-ceramide was associated with changes in histone H3 acetylation. However, although histone deacetylase inhibitors are also currently under investigation for their anti-tumor activity, we demonstrated here that a combined treatment with trichostatin A abrogated both MMP-2 down-regulation and reduced invasive properties elicited by C2-ceramide alone. Hence, this study demonstrates that besides its apoptotic effect, C2-ceramide also exhibits anti-invasive properties, showing a dual beneficial effect against cancer progression, but casts some doubt on the use of HDAC inhibitors as combined treatment with drugs that trigger the ceramide pathway.

Inflammation and melanoma growth and metastasis: the role of platelet-activating factor (PAF) and its receptor

An inflammatory tumor microenvironment fosters tumor growth, angiogenesis and metastatic progression. Platelet-activating factor (PAF) is an inflammatory biolipid produced from membrane glycerophospholipids. Through the activity of its G-protein coupled receptor, PAF triggers a variety of pathological reactions including tumor neo-angiogenesis. Several groups have demonstrated that inhibiting PAF-PAF receptor pathway at the level of a ligand or receptor results in an effective inhibition of experimental tumor growth and metastasis. In particular, our group has recently demonstrated that PAF receptor antagonists can effectively inhibit the metastatic potential of human melanoma cells in nude mice. Furthermore, we showed that PAF stimulated the phosphorylation of CREB and ATF-1 in metastatic melanoma cells, which resulted in overexpression of MMP-2 and MT1-MMP. Our data indicate that PAF acts as a promoter of melanoma metastasis in vivo. Since only metastatic melanoma cells overexpress CREB/ATF-1, we propose that these cells are better equipped to respond to PAF within the tumor microenvironment when compared to their non-metastatic counterparts.

Expression and distribution of MUC18 in human uveal melanoma

The immunoglobulin superfamily protein MUC18 is involved in transendothelial migration and signal transduction, and is expressed in malignancies including cutaneous melanoma. Recent in vitro studies showed evidence of increased MUC18 protein in some uveal melanoma cell lines with an increased potential for invasion. We assessed seven uveal and three metastasis-derived melanoma cell lines for the expression of MUC18 mRNA and protein by RT-PCR, and immunoblotting and immunocytochemistry, respectively. We also examined the expression and distribution of MUC18 in paraffin sections of primary uveal melanomas (n = 23; 5/23 spindle; 18/23 mixed and epithelioid) and normal eyes (n = 3) using a polyclonal goat anti-human antibody to MUC18 visualized with peroxidase and Vector NovaRED. Distribution and intensity of immunostaining was graded semi-quantitatively (grade 0 to 3) by 2 independent observers. All cell lines expressed MUC18 mRNA and protein ( approximately 130 kDa), and showed punctate cell membrane MUC18 immunostaining. Primary melanomas displayed heterogeneous cell membrane and cytoplasmic MUC18, with moderate to strong immunolabelling (> or =grade 2) in approximately 70% of tumours. Vasculature in tumours and in retina and choroid of all melanoma-affected and normal eyes showed intense MUC18 immunostaining. These observations further suggest a role for MUC18 in uveal melanoma growth; moreover, interactions between MUC18-positive melanoma cells and vasculature may be important for the hematogenous spread of cells during metastases.

CCAAT displacement protein regulates nuclear factor-kappa beta-mediated chemokine transcription in melanoma cells

Members of the nuclear factor-kappa beta (NF-kappaB) family maintain cellular homeostasis by enhancing the transcription of genes involved in inflammation, immune response, cell proliferation, and apoptosis. Melanoma tumor cells often express inflammatory mediators through enhanced activation of NF-kappaB. The NF-kappaB activation appears to result from the enhancer formation including NF-kappaB and lysine acetyl transferases such as p300, CREB (cyclic AMP-responsive element binding protein)-binding protein (CBP), and/or p300/CBP associating factor (PCAF). We observed that proteins expressed by Hs294T metastatic melanoma cells are highly acetylated compared with normal melanocytes, and dominant-negative PCAF reduced the basal and tumor necrosis factor-alpha-stimulated transcriptional activity of NF-kappaB. The promoter activity of NF-kappaB-regulated chemokines was also reduced by the expression of dominant-negative PCAF. The promoters of these chemokines contain a CCAAT displacement protein (CDP)-binding site near the NF-kappaB element. compared with vector-transduced cells, in CDP-transduced Hs294T cells: (i) over-expressed CDP bound efficiently to PCAF, (ii) tumor necrosis factor-alpha-stimulated chemokine expression and NF-kappaB-mediated transcription were reduced, and (iii) the binding of CBP to Rel A was reduced. These data suggest that CDP inhibits cytokine-induced NF-kappaB-regulated chemokine transcription. This study contributes to our understanding of the role of CDP in an enhanceosome of NF-kappaB-mediated chemokine transcription in human melanoma cells.

Mcl-1, Bcl-XL and Stat3 expression are associated with progression of melanoma whereas Bcl-2, AP-2 and MITF levels decrease during progression of melanoma

Members of the Bcl-2 family of antiapoptotic proteins (Bcl-2, Bcl-XL and Mcl-1) are key regulators of apoptosis. The purpose of the present study was to examine and better define the role of Bcl-2, Bcl-XL and Mcl-1 in the progression of melanoma. Immunohistochemical staining for Bcl-2, Bcl-XL and Mcl-1 was performed on paraffin sections of 100 cases of benign nevi, primary melanoma and metastatic melanoma. Expression was correlated with histopathologic features, clinical progress and expression of transcription factors (AP-2, MITF and p-Stat3). Bcl-2 was expressed in 100% of benign nevi and thin melanoma (<or=1.0 mm) but was less in thick melanoma (>1.0 mm) (88%), subcutaneous (62%) and lymph node metastases (35%). In contrast, Bcl-XL and Mcl-1 were expressed at lower levels in nevi and thin melanoma compared to Bcl-2 but their expression was much higher in thick melanoma and in subcutaneous and lymph node metastases (P<0.0001). Bcl-2 expression was negatively associated with tumor thickness (P<0.05) but Bcl-XL expression increased with increasing tumor thickness (P<0.05) and dermal tumor mitotic rate (P<0.05). Similarly Mcl-1 expression increased with increasing tumor thickness (P<0.09) and dermal tumor mitotic rate (P<0.17). Bcl-2 expression was positively correlated with expression of the transcription factors microphthalmia transcription factor (MITF) and nuclear AP-2 whereas Bcl-XL (and Mcl-1) expression were positively correlated with p-Stat3. This study is the first to show a clear dissociation between changes in Bcl-2 expression (downregulation) and Bcl-XL, Mcl-1 expression (upregulation) during progression of melanoma. The results were also consistent with a role for AP-2 and MITF in regulation of Bcl-2 and pStat3 in regulation of Bcl-XL. These findings have important implications for the development of treatments targeting antiapoptotic proteins in patients with melanoma.

[Sinonasal mucosal malignant melanoma]

INTRODUCTION

Mucosal melanomas are rare tumors, and primary sinonasal malignant melanomas uncommon tumors that are frequently misclassified. Differential diagnosis should rule out other sinonasal malignancies, including carcinoma, lymphoma, sarcoma, and olfactory neuroblastoma.

CASE

We report two new cases of sinonasal melanoma. One involved a 68-year-old man being followed for chronic sinusitis, despite antibiotics; he presented a tumor of the right nasal cavity. The second case was that of a 77-year-old woman, referred for painful gingival swelling shown to involve osteolytic growth in the left maxillary sinus. In both cases, pathologic examination of the biopsy samples concluded that these were sinonasal malignant melanomas.

DISCUSSION

Histologically, the diagnosis is very difficult because of the polymorphic features of this tumor, and immunohistochemical studies are very important. The relative inaccessibility of the mucosa to self-examination often delays diagnosis and leads to late detection and poor prognosis.

New technologies used in the study of human melanoma

The amount of information on tumor biology has expanded enormously, essentially due to the completion of the human genome sequencing and to the application of new technologies that represent an exciting breakthrough in molecular analysis. Often these data spring from experimental procedures, such as a serial analysis of gene expression (SAGE) and DNA microarrays, which cannot be defined as hypothesis-driven: it may appear to be a "brute force" approach through which no information can be directly generated concerning the specific functions of selected genes in a definite context. However, interesting results are fruitfully generated, and thus it is important to consider the enormous potential these new technologies possess and to learn how to apply this novel form of knowledge in the emerging field of molecular medicine. This review, after a limited outline regarding several classic aspects of human cutaneous melanoma biology, genetics, and clinical approaches, will focus on the proficient use of up-to-date technologies in the study of the neoplastic disease and on their capability to provide effective support to conventional approaches in melanoma diagnosis, prognosis, and treatment.

Markers and tissue resources for melanoma: meeting report

The Markers and Tissue Resources for Melanoma meeting convened by the Cancer Diagnosis Program, Division of Cancer Treatment and Diagnosis, Specialized Programs of Research Excellence at the Organ Systems Branch of the National Cancer Institute (NCI), and the Melanoma Research Foundation was held in Gaithersburg, MD on October 2005. The meeting reviewed the current status of biomarkers for early- and advanced-stage melanoma and addressed some of the challenges scientists and clinicians face as they unravel the biology of melanoma and try to apply these findings to patient care. Specifically, the participants focused on molecular changes associated with melanoma progression, potential diagnostic and prognostic markers emerging from molecular profiling studies, and new treatment targets for current and future clinical trials. They also highlighted the ongoing challenges about translational research in melanoma, including availability of tissue resources, and summarized the status of nevus and melanoma tissue microarrays, recently developed as a collaborative project between the melanoma research community and the NCI. The meeting report is intended to provide a perspective on emerging scientific approaches in translational research that can enhance the progress in discovery and validation of markers for melanoma. (Cancer Res 2006; 66(22): 10652-7).

Bioimmunotherapy for melanoma using fully human antibodies targeting MCAM/MUC18 and IL-8

Metastatic melanoma is associated with high rate of patients' mortality and represents a great challenge for cancer therapies because of its notorious resistance to chemotherapeutic drugs. Considerable efforts have been made over the last 2 decades in pursuit of new treatment modalities and identification of molecular events associated with melanoma progression and development of metastases. The acquisition of the metastatic phenotype is associated with overexpression of the adhesion molecule MCAM/MUC18 and the angiogenic factor IL-8. In this review, we summarize our current knowledge on MCAM/MUC18 and IL-8, their transcriptional regulation, and their role in melanoma growth, angiogenesis and metastasis. Further, we report on the development of new fully human antibodies, anti-MCAM/MUC18 (ABX-MA1) and anti-IL-8 (ABX-IL8), and their effects on tumor growth and metastasis in animal models. Collectively, our studies suggest that ABX-MA1 and ABX-IL8 could serve as new modalities for the treatment of melanoma either alone, or in combination with conventional chemotherapy or other antitumor agents.

NF-kappaB activation in melanoma

Metastatic melanoma is an aggressive skin cancer that is notoriously resistant to current cancer therapies. In human melanoma, nuclear factor-kappa B (NF-kappaB) is upregulated, leading to the deregulation of gene transcription. In this review, we discuss (i) the relationship between gene alteration in melanoma and upregulation of NF-kappaB, (ii) mechanisms by which activated NF-kappaB switch from pro-apoptotic to anti-apoptotic functions in melanoma and (iii) autocrine mechanisms that promote constitutive activation of NF-kappaB in metastatic melanoma.

mda-9/Syntenin: a positive regulator of melanoma metastasis

Metastasis is a significant event in cancer progression and continues to pose the greatest challenge for a cancer cure. Defining genes that control metastasis in vivo may provide new targets for intervening in this process with profound therapeutic implications. Melanoma differentiation associated gene-9 (mda-9) was initially identified by subtraction hybridization as a novel gene displaying biphasic expression during terminal differentiation in human melanoma cells. Mda-9, also known as syntenin, is a PDZ-domain protein overexpressed in many types of human cancers, where it is believed to function in tumor progression. However, a functional role of mda-9/syntenin in tumor growth and metastasis and the signaling pathways involved in mediating these biological activities remain to be defined. Evidence is now provided, using weakly and highly metastatic isogenic melanoma variants, that mda-9/syntenin regulates metastasis. Expression of mda-9/syntenin correlates with advanced stages of melanoma progression. Regulating mda-9/syntenin expression using a replication-incompetent adenovirus expressing either sense or antisense mda-9/syntenin modifies the transformed phenotype and alters metastatic ability in immortal human melanocytes and metastatic melanoma cells in vitro and in vivo in newborn rats. A direct relationship is observed between mda-9/syntenin expression and increased phosphorylation of focal adhesion kinase, c-Jun-NH2-kinase, and p38. This study provides the first direct link between mda-9/syntenin expression and tumor cell dissemination in vivo and indicates that mda-9/syntenin expression activates specific signal transduction pathways, which may regulate melanoma tumor progression. Based on its ability to directly alter metastasis, mda-9/syntenin provides a promising new focus for melanoma cancer research with potential therapeutic applications for metastatic diseases.

Early cancers of the skin: clinical, histopathological, and molecular characteristics

Because skin lesions are visible and easily accessible, skin cancers provide us with an excellent in vivo model to study the development of cancers. Cutaneous malignant melanoma and squamous cell carcinoma (SCC) both arise from the epidermis and have an initial progression stage in which proliferation of the neoplastic cells is confined to the epidermis. This stage is called melanoma in situ or SCC in situ. Molecular analyses of melanoma in situ and of solar keratosis, a prototype of early SCC in situ, show that loss of p16(INK4a)/p14(ARF) and dysfunction of p53 play a critical role, respectively. Furthermore, there seems to be potential precursor cells to these in situ lesions, which are not discernible with conventional hematoxylin and eosin-stained sections. The precursor cells have minimal but critical genetic alterations, such as cyclin D1 amplification and p53 mutation, and can be identified using fluorescent in situ hybridization and immunostaining with p53 antibodies, respectively. These precursor cells may be defective in repair response to DNA damage, and would have proliferative or survival advantages over their normal neighboring counterparts in the presence of growth factor stimulation or genotoxic events, such as ultraviolet irradiation. Such precursor clones may be induced at a rather young age, and their number and size increase with accumulating carcinogenic stimuli. If these lesions acquire additional mutations, they could progress to clinically visible lesions of in situ carcinoma. Precise molecular analyses of early stages of skin cancers may have a strong impact on our understanding of in vivo development of cancers in other human organs.

Platelet-activating factor mediates MMP-2 expression and activation via phosphorylation of cAMP-response element-binding protein and contributes to melanoma metastasis

Overexpression of cAMP-response element (CRE)-binding protein (CREB) and activating transcription factor (ATF) 1 contributes to melanoma progression and metastasis at least in part by promoting tumor cell survival and stimulating matrix metalloproteinase (MMP) 2 expression. However, little is known about the regulation of CREB and ATF-1 activities and their phosphorylation within the tumor microenvironment. We analyzed the effect of platelet-activating factor (PAF), a potent phospholipid mediator of inflammation, for its ability to activate CREB and ATF-1 in eight cultured human melanoma cell lines, and we found that PAF receptor (PAFR) was expressed in all eight lines. In metastatic melanoma cell lines, PAF induced CREB and ATF-1 phosphorylation via a PAFR-mediated signal transduction mechanism that required pertussis toxin-insensitive Galphaq protein and adenylate cyclase activity and was antagonized by a cAMP-dependent protein kinase A and p38 MAPK inhibitors. Addition of PAF to metastatic A375SM cells stimulated CRE-dependent transcription, as observed in a luciferase reporter assay, without increasing the CRE DNA binding capacity of CREB. Furthermore, PAF stimulated the gelatinase activity of MMP-2 by activating transcription and MMP-2 expression. MMP-2 activation correlated with the PAF-induced increase in the expression of an MMP-2 activator, membrane type 1 MMP. PAF-induced expression of pro-MMP-2 was causally related to PAF-induced CREB and ATF-1 phosphorylation; it was prevented by PAFR antagonist and inhibitors of p38 MAPK and protein kinase A and was abrogated upon quenching of CREB and ATF-1 activities by forced overexpression of a dominant-negative form of CREB. PAF-induced MMP-2 activation was also down-regulated by p38 MAPK and protein kinase A inhibitors. Finally, PAFR antagonist PCA4248 inhibited the development of A375SM lung metastasis in nude mice. This result indicated that PAF acts as a promoter of melanoma metastasis in vivo. We proposed that metastatic melanoma cells overexpressing CREB/ATF-1 are better equipped than nonmetastatic cells to respond to PAF within the tumor microenvironment.

The AP-2gamma transcription factor is upregulated in advanced-stage ovarian carcinoma

OBJECTIVE

To analyze the expression of the AP-2gamma transcription factor in ovarian borderline tumors, early-stage ovarian carcinoma and advanced-stage ovarian carcinoma, and to evaluate its prognostic role in advanced-stage tumors.

METHODS

Sections from 14 normal ovaries, 75 borderline tumors, 22 FIGO stage I invasive ovarian carcinomas, and 306 advanced-stage (FIGO stages II-IV) ovarian carcinomas (42 primary tumors, 62 solid metastases, 202 effusions) were evaluated for expression of the transcription factor AP-2gamma using immunohistochemistry. Sixty-three effusions and two cell lines (SKOV-3 and OVCAR-3) were additionally studied using immunoblotting. The prognostic role of AP-2gamma in advanced-stage carcinomas was analyzed.

RESULTS

AP-2gamma was detected in the nucleus of tumor cells in 28/75 (37%) borderline tumors, 13/22 (59%) FIGO stage I carcinomas, and 255/306 (83%) advanced-stage carcinomas (P < 0.001, Chi-square test). Benign ovaries were uniformly negative. Expression was largely limited to carcinoma cells in effusions. Solid lesions and effusions from advanced-stage carcinomas showed comparable expression. Immunoblotting showed AP-2gamma expression in 59/61 effusions and both cell lines. AP-2gamma expression did not correlate with survival.

CONCLUSIONS

AP-2gamma expression is upregulated in advanced-stage ovarian carcinoma compared to early-stage carcinomas, borderline tumors, and the ovarian surface epithelium, and AP-2gamma is specifically localized to cancer cells in effusions, suggesting a role in tumor progression. The lack of predictive value for this transcription factor in advanced-stage disease may be related to its frequent expression.

Human malignant melanoma: detection of BRAF- and c-kit-activating mutations by high-resolution amplicon melting analysis

Activating mutations in the BRAF kinase have been reported in a large number of cases of malignant melanoma. This suggests that therapy with specific RAF kinase inhibitors may find use in treating this disease. If the response to RAF kinase inhibition is dependent on the presence of an activated BRAF protein, it will be necessary to evaluate cases of malignant melanoma for the presence or absence of BRAF mutations. High-resolution amplicon melting analysis is able to detect single base-pair changes in DNA isolated from paraffin-embedded tissue sections and obviates the need for direct DNA sequencing. Results can be available within 48 hours. In this report, we used high-resolution amplicon melting analysis to evaluate 90 cases of malignant melanoma for BRAF mutations. Of these 90 cases, 74 were metastatic melanomas, 12 were primary cutaneous melanomas, and 4 were in situ melanomas. BRAF activation mutations were found in 43 cases (48%). Forty-one of these mutations were in exon 15. The mutations in exon 15 included V600E (34 cases), V600K (6 cases), and V600R (1 case). Two activating mutations were found in exon 11, G469V and G469R. The presence or absence of a BRAF mutation in the junctional component of an invasive melanoma was maintained in the invasive component. We also evaluated these 90 cases, as well as an additional 10 cases (total of 100) for the expression of c-kit. The majority of invasive and metastatic malignant melanomas did not express c-kit, although all in situ lesions and the junctional components of invasive lesions were strongly c-kit positive. Surprisingly, 2 cases of metastatic malignant melanoma (2%) showed strong and diffuse c-kit expression and contained a c-kit-activating mutation, L576P, as detected by high-resolution amplicon melting analysis and confirmed by direct DNA sequencing. These 2 c-kit mutation-positive cases did not contain BRAF mutations. The presence of a c-kit-activating mutation in metastatic malignant melanoma suggests that a small number of melanomas may progress by a somatic mutation of the c-kit gene. The presence of BRAF- and c-kit-activating mutations in malignant melanoma suggests new approaches to treating this disease involving specific tyrosine kinase inhibitors may prove worthwhile and that mutation analysis by high-resolution melting analysis might help guide therapy.