Loss of maspin expression contributes to a more invasive potential in malignant melanoma

SERPINB5 promotes colorectal cancer invasion and migration by promoting EMT and angiogenesis via the TNF-α/NF-κB pathway

This study aimed to investigate the role of SERPINB5 in colorectal cancer (CRC). We established knockdown and overexpression models of SERPINB5 in CRC cells and conducted bioinformatics analysis to assess the clinicopathological significance of SERPINB5 expression in CRC patients. Human CRC cells were transfected with LV-SERPINB5 and sh-SERPINB5 lentivirus for subsequent functional and mechanistic studies. Results showed that high SERPINB5 expression correlated positively with CEA levels, N stage and lymphatic infiltration, while displaying a negative correlation with progression-free survival. Overexpression of SERPINB5 in CRC cells upregulated the expression of TNF-α, p-NF-κB/p65, N-cadherin, MMP2 and MMP9, accompanied by decreased E-cadherin expression. In addition, SERPINB5 overexpression enhanced the migration, invasion, and proliferation of CRC cells. Furthermore, overexpression of SERPINB5 in CRC cells increased VEGFA expression, and the conditioned medium from SERPINB5-overexpressing CRC cells promoted tube formation of HUVECs. Conversely, overexpression of SERPINB5 in HUVECs decreased VEGFA expression and inhibited tube formation. Notably, these changes in CRC cells were reversed by QNZ, a specific inhibitor of the TNF-α/NF-κB pathway. In summary, our findings revealed that high SERPINB5 expression correlated with poor progression-free survival in CRC patients. Moreover, SERPINB5 could induce EMT and angiogenesis by activating the TNF-α/NF-κB pathway, thereby promoting the invasion and migration of CRC cells.

Methylation Markers in Cutaneous Melanoma: Unravelling the Potential Utility of Their Tracking by Liquid Biopsy

Malignant melanoma is the most serious, life-threatening form of all dermatologic diseases, with a poor prognosis in the presence of metastases and advanced disease. Despite recent advances in targeted therapy and immunotherapy, there is still a critical need for a better understanding of the fundamental mechanisms behind melanoma progression and resistance onset. Recent advances in genome-wide methylation methods have revealed that aberrant changes in the pattern of DNA methylation play an important role in many aspects of cancer progression, including cell proliferation and migration, evasion of cell death, invasion, and metastasization. The purpose of the current review was to gather evidence regarding the usefulness of DNA methylation tracking in liquid biopsy as a potential biomarker in melanoma. We investigated the key genes and signal transduction pathways that have been found to be altered epigenetically in melanoma. We then highlighted the circulating tumor components present in blood, including circulating melanoma cells (CMC), circulating tumor DNA (ctDNA), and tumor-derived extracellular vesicles (EVs), as a valuable source for identifying relevant aberrations in DNA methylation. Finally, we focused on DNA methylation signatures as a marker for tracking response to therapy and resistance, thus facilitating personalized medicine and decision-making in the treatment of melanoma patients.

Bona Fide Tumor Suppressor Genes Hypermethylated in Melanoma: A Narrative Review

Loss-of-function events in tumor suppressor genes (TSGs) contribute to the development and progression of cutaneous malignant melanoma (CMM). Epigenetic alterations are the major mechanisms of TSG inactivation, in particular, silencing by promoter CpG-island hypermethylation. TSGs are valuable tools in diagnosis and prognosis and, possibly, in future targeted therapy. The aim of this narrative review is to outline bona fide TSGs affected by promoter CpG-island hypermethylation and their functional role in the progression of CMM. We conducted a systematic literature review to identify studies providing evidence of bona fide TSGs by cell line or animal experiments. We performed a broad first search and a gene-specific second search, supplemented by reference checking. We included studies describing bona fide TSGs in CMM with promoter CpG-island hypermethylation in which inactivating mechanisms were reported. We extracted data about protein role, pathway, experiments conducted to meet the bona fide criteria and hallmarks of cancer acquired by TSG inactivation. A total of 24 studies were included, describing 24 bona fide TSGs silenced by promoter CpG-island hypermethylation in CMM. Their effect on cell proliferation, apoptosis, growth, senescence, angiogenesis, migration, invasion or metastasis is also described. These data give further insight into the role of TSGs in the progression of CMM.

Hypoxia-dependent drivers of melanoma progression

Hypoxia, a condition of low oxygen availability, is a hallmark of tumour microenvironment and promotes cancer progression and resistance to therapy. Many studies reported the essential role of hypoxia in regulating invasiveness, angiogenesis, vasculogenic mimicry and response to therapy in melanoma. Melanoma is an aggressive cancer originating from melanocytes located in the skin (cutaneous melanoma), in the uveal tract of the eye (uveal melanoma) or in mucosal membranes (mucosal melanoma). These three subtypes of melanoma represent distinct neoplasms in terms of biology, epidemiology, aetiology, molecular profile and clinical features.In this review, the latest progress in hypoxia-regulated pathways involved in the development and progression of all melanoma subtypes were discussed. We also summarized current knowledge on preclinical studies with drugs targeting Hypoxia-Inducible Factor-1, angiogenesis or vasculogenic mimicry. Finally, we described available evidence on clinical studies investigating the use of Hypoxia-Inducible Factor-1 inhibitors or antiangiogenic drugs, alone or in combination with other strategies, in metastatic and adjuvant settings of cutaneous, uveal and mucosal melanoma.Hypoxia-Inducible Factor-independent pathways have been also reported to regulate melanoma progression, but this issue is beyond the scope of this review.As evident from the numerous studies discussed in this review, the increasing knowledge of hypoxia-regulated pathways in melanoma progression and the promising results obtained from novel antiangiogenic therapies, could offer new perspectives in clinical practice in order to improve survival outcomes of melanoma patients.

Role of class I histone deacetylases in the regulation of maspin expression in prostate cancer

Maspin repression is frequently observed in prostate cancer; however, the molecular mechanism(s) causing the loss is not completely understood. Here, we demonstrate that inhibition of class I histone deacetylases (HDACs) mediates re-expression of maspin which plays an essential role in suppressing proliferation and migration capability in prostate cancer cells. Human prostate cancer LNCaP and DU145 cells treated with HDAC inhibitors, sodium butyrate, and trichostatin A, resulted in maspin re-expression. Interestingly, an exploration into the molecular mechanisms demonstrates that maspin repression in prostate tumor and human prostate cancer cell lines occurs via epigenetic silencing through an increase in HDAC activity/expression, independent of promoter DNA hypermethylation. Furthermore, transcriptional activation of maspin was accompanied with the suppression of HDAC1 and HDAC8 with significant p53 enrichment at the maspin promoter associated with an increase in histone H3/H4 acetylation. Our results provide evidence of maspin induction as a critical epigenetic event altered by class I HDACs in the restoration of balance to delay proliferation and migration ability of prostate cancer cells.

Protease-activated receptors (PARs)--biology and role in cancer invasion and metastasis

Although many studies have demonstrated that components of the hemostatic system may be involved in signaling leading to cancer progression, the potential mechanisms by which they contribute to cancer dissemination are not yet precisely understood. Among known coagulant factors, tissue factor (TF) and thrombin play a pivotal role in cancer invasion. They may be generated in the tumor microenvironment independently of blood coagulation and can induce cell signaling through activation of protease-activated receptors (PARs). PARs are transmembrane G-protein-coupled receptors (GPCRs) that are activated by a unique proteolytic mechanism. They play important roles in vascular physiology, neural tube closure, hemostasis, and inflammation. All of these agents (TF, thrombin, PARs—mainly PAR-1 and PAR-2) are thought to promote cancer invasion and metastasis at least in part by facilitating tumor cell migration, angiogenesis, and interactions with host vascular cells, including platelets, fibroblasts, and endothelial cells lining blood vessels. Here, we discuss the role of PARs and their activators in cancer progression, focusing on TF- and thrombin-mediated actions. Therapeutic options tailored specifically to inhibit PAR-induced signaling in cancer patients are presented as well.

Different maspin functions in the lung adenocarcinoma A549 and SPC-A1 cell lines

Mammary serine protease inhibitor (maspin) is a tumor suppressor gene that is silenced in the majority of cancer cells during metastatic progression by transcriptional and epigenetic mechanisms. The function of maspin in non‑small cell lung cancer cells (NSCLC) has not been clearly defined. In the present study, the expression of maspin in NSCLC cell lines, in particular, the adenocarcinoma cell lines, was heterogeneous. While the expression levels of maspin in PC‑9 and H460 cell lines were intact, the expression of maspin in the A549 and SPC‑A1 cells was hardly detected. Ectopic expression of maspin in A549 cells carrying the K‑ras gene point mutation significantly inhibited cell migration and invasion abilities, which was associated with downregulated expression of matrix metalloproteinase‑2 and integrin β1. Ectopic expression of maspin in SPC‑A1 cells harboring the wild‑type K‑ras gene predominantly affected cell growth via targeting the AKT signaling molecules. Maspin functions differently in lung adenocarcinoma cells, possibly due to the varied molecular characteristics.

Internalization by multiple endocytic pathways and lysosomal processing impact maspin-based therapeutics

Patients with metastatic disease face high rates of mortality with a paucity of therapeutic options. Protein-based therapeutics provide advantages over traditional chemotherapy through increased specificity, decreased immune impairment, and more direct means of delivery. However, development is often hindered because of insufficient knowledge about protein processing by cells when exogenously applied. This study focuses on recombinant Maspin (rMaspin), a serine protease inhibitor (SERPINB5), which alters invasive properties when directly applied to cancer cells. Previous evidence suggests differences in the effects of rMaspin treatment when compared with endogenous reexpression, with little explanation for these discrepancies. A leading hypothesis is that exogenously applied rMaspin is subject to different regulatory and/or processing mechanisms in cancer cells when compared with endogenous expression. Therefore, a more detailed understanding of the mechanisms of internalization and subcellular trafficking of rMaspin is needed to guide future translational development. We describe the molecular trafficking of rMaspin in cytoplasmic vesicles of the endosomal/lysosomal pathway and characterize its uptake by multiple endocytic mechanisms. Time-lapse laser scanning confocal microscopy shows the uptake, in real time, of dye-labeled rMaspin in cancer cells. This study indicates that cellular processing of rMaspin plays a key role by affecting its biologic activity and highlights the need for new approaches aimed at increasing the availability of rMaspin when used to treat cancer.

IMPLICATIONS

Novel characterization of internalization and subcellular trafficking of rMaspin provides new insights for future therapeutic development.

Maspin expression and melanoma progression: a matter of sub-cellular localization

Maspin, a member of the serpin family of protease inhibitors, is involved in key processes of cancer progression. Its biological activity seems to be cancer and compartment specific, with the protein acting either as a suppressor or as a tumor promoter in different cancer types. Characterization of maspin expression and its sub-cellular localization in melanoma is missing, hence, we aim to investigate its possible association with melanoma prognostic factors and disease progression. Nuclear and cytoplasmic maspin expression were evaluated on 60 nevi, 152 primary lesions, and 106 melanoma metastases using tissue microarrays and immunohistochemistry. The association between maspin immunoreactivity and patient's clinic-pathological features was evaluated. Multivariate logistic models and survival analyses were performed for maspin expression in primary melanomas. Nuclear maspin was detected in 8% nevi, 49% primary melanomas, and 28% metastases, whereas cytoplasmic maspin in 12% nevi, 18% primary lesions, and 9% metastases. In univariate analysis, nuclear maspin expression in primary melanomas was significantly associated with melanoma prognostic factors (nodular histotype, tumor thickness, mitotic rate, and ulceration) and disease stage, whereas cytoplasmic maspin was observed at higher frequency in thin superficial spreading melanomas, without mitosis. In multivariate analysis, nuclear maspin remained significantly associated with risk of developing a tumor prone to disease progression and, accordingly, with significantly shorter disease-free and overall survival. In this study, maspin was expressed at highest frequency in primary lesions and when expressed in the nuclei, was significantly associated with poor prognostic markers, melanoma recurrence, and worse survival. The present study suggests a tumor-suppressive effect of cytoplasmic maspin and a tumor-promoting effect of nuclear maspin, which open the discussion on its potential use in cancer therapy.

Maspin expression in the invasive margin of primary melanomas may reflect an aggressive tumor phenotype

BACKGROUND

The role of maspin has been discussed controversially in different tumors. In the majority of malignant tumors, maspin seems to act as a tumor suppressor. However, data about maspin expression as well as its function in melanoma are very inconsistent.

OBJECTIVE

To investigate the expression of maspin in melanomas and to correlate the intensity of maspin staining with prognostic parameters of the tumor and with progression-free and overall survival.

PATIENTS AND METHODS

Primary melanomas from 47 patients were investigated for maspin expression using immunohistochemistry.

RESULTS

Maspin was heterogeneously expressed predominantly in the cytoplasm of melanoma cells. Maspin staining intensity in the invasive part of the tumor correlated with parameters of prognosis such as Clark level (p  =  0.05), tumor thickness (p  =  0.002) and stage of disease (p  =  0.023). Maspin staining intensity in the invasive front of the tumor significantly correlated with death from disease (p  =  0.007) and shortened overall survival (p  =  0.007).

CONCLUSIONS

In accordance with data concerning maspin expression in colorectal cancers, the expression of this protein in the invasive front of primary melanomas seems to correlate with local infiltration and tumor aggressiveness. Strong maspin expression in the invasive margin of primary melanomas therefore might reflect an aggressive tumor phenotype.

Genome-wide promoter methylation analysis identifies epigenetic silencing of MAPK13 in primary cutaneous melanoma

The involvement of epigenetic alterations in the pathogenesis of melanoma is increasingly recognized. Here, we performed genome-wide DNA methylation analysis of primary cutaneous melanoma and benign melanocytic nevus interrogating 14 495 genes using BeadChip technology. This genome-wide view of promoter methylation in primary cutaneous melanoma revealed an array of recurrent DNA methylation alterations with potential diagnostic applications. Among 106 frequently hypermethylated genes, there were many novel methylation targets and tumor suppressor genes. Highly recurrent methylation of the HOXA9, MAPK13, CDH11, PLEKHG6, PPP1R3C, and CLDN11 genes was established. Promoter methylation of MAPK13, encoding p38δ, was present in 67% of primary and 85% of metastatic melanomas. Restoration of MAPK13 expression in melanoma cells exhibiting epigenetic silencing of this gene reduced proliferation, indicative of tumor suppressive functions. This study demonstrates that DNA methylation alterations are widespread in melanoma and suggests that epigenetic silencing of MAPK13 contributes to melanoma progression.

Maspin: molecular mechanisms and therapeutic implications

Maspin, a non-inhibitory member of the serine protease inhibitor superfamily, has been characterized as a tumor suppressor gene in multiple cancer types. Among the established anti-tumor effects of Maspin are the inhibition of cancer cell invasion, attachment to extracellular matrices, increased sensitivity to apoptosis, and inhibition of angiogenesis. However, while significant experimental data support the role of Maspin as a tumor suppressor, clinical data regarding the prognostic implications of Maspin expression have led to conflicting results. This highlights the need for a better understanding of the context dependencies of Maspin in normal biology and how these are perturbed in the context of cancer. In this review, we outline the regulation and roles of Maspin in normal and developmental biology while discussing novel evidence and emerging theories related to its functions in cancer. We provide insight into the immense therapeutic potential of Maspin and the challenges related to its successful clinical translation.

Elevated maspin expression is associated with better overall survival in esophageal squamous cell carcinoma (ESCC)

Tumor suppressor maspin is a differentially regulated gene in the progression of many types of cancer. While the biological function of maspin in blocking tumor invasion and metastasis is consistent with the loss of maspin expression at the late stage of tumor progression, the differential expression and the biological significance of maspin in early stage of tumor progression appear to be complex and remain to be elucidated. In the current study, we examined the expression of maspin in 84 esophageal squamous cell carcinoma (ESCC) cases (stages I–III) and 55 non-tumor adjacent esophageal tissue specimens by immunohistochemical (IHC) staining. The correlation of maspin with clinicopathological parameters was analyzed. Compared to normal esophageal squamous tissue where 80% (47/55) of the cases expressed maspin at a low to moderate level, all ESCC specimens (100% (84/84)) were positive for maspin expression at a moderate to high level. ESCC with low or moderate maspin expression had significantly shorter postoperative survival rates compared to those that had high maspin expression (p<0.001). Since the correlation of maspin with ESCC histology and the correlation of maspin with ESCC prognosis seem to be at odds, we further investigated the biological function of maspin in ESCC using the established ESCC cell lines. The expression of maspin in five human esophageal squamous cancer cell lines (T12, E450, KYSE150, EC109, and KYSE510) was examined by the Western blot. ESCC cell line KYSE510 that did not express maspin and was stably transfected by maspin cDNA or an empty vector. The resulting transfected cells were characterized in vitro. Maspin expression significantly inhibited cell proliferation, motility and matrigel invasion. Taken together, our data suggest that the transient up-regulation of maspin in the early development of ESCC may be a defense mechanism against further transition towards more malignant phenotypes, ultimately slowing down ESCC tumor progression.

Role of maspin in cancer

Maspin (mammary serine protease inhibitor), is a member of the serine protease inhibitor/non-inhibitor superfamily. Its expression is down-regulated in breast, prostate, gastric and melanoma cancers but over-expressed in pancreatic, gallbladder, colorectal, and thyroid cancers suggesting that maspin may play different activities in different cell types. However, maspin expression seems to be correlated with better prognosis in prostate, bladder, lung, gastric, colorectal, head and neck, thyroid and melanoma cancer. In breast and ovarian cancer maspin significance is associated with its subcellular localization: nucleus maspin expression correlates with a good prognosis, whilst in pancreatic cancer it predicts a poor prognosis. Since tumor metastasis requires the detachment and invasion of tumor cells through the basement membrane and stroma, a selectively increased adhesion by the presence of maspin may contribute to the inhibition of tumor metastasis. Furthermore the different position of maspin inside the cell or its epigenetic modifications may explain the different behavior of the expression of maspin between tumors. The expression of maspin might be useful as a prognostic and possibly predictive factor for patients with particular types of cancer and data can guide physicians in selecting therapy. Its expression in circulating tumor cells especially in breast cancer, could be also useful in clinical practice along with other factors, such as age, comorbidities, blood examinations in order to select the best therapy to be carried out. Focusing on the malignancies in which maspin showed a positive prognostic value, therapeutic approaches studied so far aimed to re-activate a dormant tumor suppressor gene by designed transcription factors, to hit the system that inhibits the expression of maspin, to identify natural substances that can determine the activation and the expression of maspin or possible “molecules binds” to introduce maspin in cancer cell and gene therapy capable of up-regulating the maspin in an attempt to reduce primarily the risk of metastasis.

Further studies in these directions are necessary to better define the therapeutic implication of maspin.

Fragments of SLIT3 inhibit cellular migration

The repellent factor family of Slit molecules has been described as having a repulsive function in the developing nervous system on growing axons expressing the Roundabout (Robo) receptors. Recent studies determined the effects of Slit molecules on the migratory and invasive potential of several types of tumor cells but also on synovial fibroblasts (SFs) derived from rheumatoid arthritis (RA) patients. To optimize a potential therapeutic application we aimed at generatingfragments of Slit3 showing the same functional ability as the full-length molecule but having the advantage of a smaller size. Recombinant Slit3 proteins were expressed and analyzed by western blotting. Their activity was defined by functional assays such as migration assays with RASF and melanoma cells. Recombinant Slit3 containing only leucine rich repeat domain 2 (D2), the domain important for Robo binding and the minimal functional unit D2 dNC were both able to inhibit migration of RASFs as effectively as Slit3 with all 4 repeats. Collectively, our data showed that the ability of Slit3 to reduce the migratory activity of synovial cells from patients with RA and melanoma cells can be mimicked by small protein fragments derived from Slit3. Slit3 fragments may be helpful in therapeutic attempts; however, further studies are necessary in order to elucidate their activity in vivo.

Immunohistochemical features of 3,3',4,4'-tetrachloroazobenzene-induced rat gingival lesions

Gingival lesions of squamous hyperplasia, cystic keratinizing hyperplasia (CKH), and squamous cell carcinoma (SCC) can be induced in rats treated by chronic gavage with 10-100 mg/kg 3,3',4,4'-tetrachloroazobenzene. We evaluated gingival squamous hyperplasia (GSH), CKH, and SCC for the immunohistochemical pattern of expression of carcinogenesis-associated markers. The 3 types of lesions and controls were stained with proliferation markers (proliferating cell nuclear antigen [PCNA] and cyclin-D1), tumor-suppressor markers (β-catenin and mammary serine protease inhibitor [maspin]) and stroma-related markers (α-smooth muscle actin [SMA] and osteonectin/SPARC). The lesions had common immunohistochemical characteristics that differed in their expression patterns among the various diagnoses. PCNA and cyclin-D1 expression was higher in GSH, CKH, and SCC than in controls. The normal membranous expression of β-catenin was lower in GSH, and almost absent in CKH and SCC. Maspin expression was similar in GSH and controls, whereas both CKH and SCC showed decreased expression. SMA and/or osteonectin/SPARC were seen in stromal cells in CKH and SCC. Collectively, there appears to be a progression from hyperplastic and cystic lesions toward malignancy based on the morphological changes, supported by the expression of carcinogenesis-associated proteins. The exact sequence of events leading to SCC remains to be defined in a time-dependent manner.

The emerging role of the thrombin receptor (PAR-1) in melanoma metastasis--a possible therapeutic target

Melanoma remains as the deadliest form of skin cancer with limited and inefficient treatment options available for patients with metastatic disease. Within the last decade, the thrombin receptor, Protease Activated Receptor-1, has been described as an essential gene involved in the progression of human melanoma. PAR-1 is known to activate adhesive, invasive and angiogenic factors to promote melanoma metastasis. It is overexpressed not only in metastatic melanoma cell lines but is also highly expressed in metastatic lesions as compared to primary nevi and normal skin. Recently, PAR-1 has been described to regulate the gap junction protein Connexin 43 and the tumor suppressor gene Maspin to promote the metastatic melanoma phenotype. Herein, we review the role of PAR-1 in the progression of melanoma as well as utilizing PAR-1-regulated genes as potential therapeutic targets for melanoma treatment.

Protease activated receptor-1 inhibits the Maspin tumor-suppressor gene to determine the melanoma metastatic phenotype

The thrombin receptor protease activated receptor-1 (PAR-1) is overexpressed in metastatic melanoma cell lines and tumor specimens. Previously, we demonstrated a significant reduction in tumor growth and experimental lung metastasis after PAR-1 silencing via systemic delivery of siRNA encapsulated into nanoliposomes. Gene expression profiling identified a 40-fold increase in expression of Maspin in PAR-1-silenced metastatic melanoma cell lines. Maspin promoter activity was significantly increased after PAR-1 silencing, suggesting that PAR1 negatively regulates Maspin at the transcriptional level. ChIP analyses revealed that PAR-1 decreases binding of Ets-1 and c-Jun transcription factors to the Maspin promoter, both known to activate Maspin transcription. PAR-1 silencing did not affect Ets-1 or c-Jun expression; rather it resulted in increased expression of the chromatin remodeling complex CBP/p300, as well as decreased activity of the CBP/p300 inhibitor p38, resulting in increased binding of Ets-1 and c-Jun to the Maspin promoter and higher Maspin expression. Functionally, Maspin expression reduced the invasive capability of melanoma cells after PAR-1 silencing, which was abrogated after rescuing with PAR-1. Furthermore, tumor growth and experimental lung metastasis was significantly decreased after expressing Maspin in a metastatic melanoma cell line. Moreover, silencing Maspin in PAR-1-silenced cells reverted the inhibition of tumor growth and experimental lung metastasis. Herein, we demonstrate a mechanism by which PAR-1 negatively regulates the expression of the Maspin tumor-suppressor gene in the acquisition of the metastatic melanoma phenotype, thus attributing an alternative function to PAR-1 other than coagulation.

Proteases in cutaneous malignant melanoma: relevance as biomarker and therapeutic target

Cutaneous malignant melanoma is the most aggressive skin cancer. It is also the most rapidly spreading cancer in terms of worldwide incidence. Although it is detected by simple inspection and can be relatively easily removed or treated, differential diagnosis to other melanocytic lesions, lack of prognostic markers, and no efficient treatment of advanced melanoma pose problems. Detection and targeting of proteases may represent a useful tool since they play a role in tumor cell metabolism, invasion, angiogenesis and metastasis. This review gives an overview of the role of proteases in development and progression of cutaneous malignant melanoma. In addition, regulation, activation, and interaction of proteases and their inhibitors are explained for tumors in general. The potential use of proteases as differential markers for melanoma mimicking melanocytic lesions, as biomarkers in tissues, and as prognostic serum markers is discussed. Current and future possibilities to target tumor proteases in therapy are presented.

Aberrant DNA methylation in malignant melanoma

Malignant melanoma remains one of the most deadly human cancers with no effective cures for metastatic disease. The poor efficacy of current therapy in advanced melanoma highlights the need for better understanding of molecular mechanisms contributing to the disease. Recent work has shown that epigenetic changes, including aberrant DNA methylation, lead to alterations in gene expression and are as important in the development of malignant melanoma as the specific and well-characterized genetic events. Reversion of these methylation patterns could thus lead to a more targeted therapy and are currently under clinical investigation. The purpose of this review is to compile recent information on aberrant DNA methylation of melanoma, to highlight key genes and molecular pathways in melanoma development, which have been found to be epigenetically altered and to provide insight as to how DNA methylation might serve as targeted treatment option as well as a molecular and prognostic marker in malignant melanoma.

Epigenetics of human cutaneous melanoma: setting the stage for new therapeutic strategies

Cutaneous melanoma is a very aggressive neoplasia of melanocytic origin with constantly growing incidence and mortality rates world-wide. Epigenetic modifications (i.e., alterations of genomic DNA methylation patterns, of post-translational modifications of histones, and of microRNA profiles) have been recently identified as playing an important role in melanoma development and progression by affecting key cellular pathways such as cell cycle regulation, cell signalling, differentiation, DNA repair, apoptosis, invasion and immune recognition. In this scenario, pharmacologic inhibition of DNA methyltransferases and/or of histone deacetylases were demonstrated to efficiently restore the expression of aberrantly-silenced genes, thus re-establishing pathway functions. In light of the pleiotropic activities of epigenetic drugs, their use alone or in combination therapies is being strongly suggested, and a particular clinical benefit might be expected from their synergistic activities with chemo-, radio-, and immuno-therapeutic approaches in melanoma patients. On this path, an important improvement would possibly derive from the development of new generation epigenetic drugs characterized by much reduced systemic toxicities, higher bioavailability, and more specific epigenetic effects.

Slit3 inhibits Robo3-induced invasion of synovial fibroblasts in rheumatoid arthritis

Introduction

The repellent factor family of Slit molecules has been described to have repulsive function in the developing nervous system on growing axons expressing the Robo receptors. However, until today no data are available on whether these repellent factors are involved in the regulation of synovial fibroblast (SF) activity in rheumatoid arthritis (RA).

Methods

mRNA expression in primary synovial fibroblasts was quantified by quantitative reverse transcription PCR and protein expression was measured by fluorescence activated cell sorting (FACS) analysis. Different functional assays were performed with rheumatoid arthritis synovial fibroblasts (RASF): proliferation, migration and a novel in-vitro cartilage destruction assay.

Results

First, we found increased expression of Robo3 expression in RASF compared to normal SF. Interestingly, analysis of data from a recently published genome-wide association study suggests a contribution of ROBO3 gene polymorphisms to susceptibility of RA. Functional assays performed with RASF revealed induction of migration and cartilage destruction by Robo3 and increased matrix metalloproteinase (MMP)1 and MMP3 expression. Treatment of RASF in early passages with Slit3 led to inhibition of migration whereas RASF in later passages, having reduced Robo3 expression in cell culture, were not inhibited by Slit3 treatment. Here, reduction of Robo3 expression from passage 3 to 10 might reflect an important step in losing repulsive activity of Slit3.

Conclusions

Taken together, our data showed that deregulation of the Robo3 receptor in synovial fibroblasts in RA correlates with aggressiveness of the fibroblasts. Slit3 reduces the migratory activity of synovial cells from patients with RA, potentially by repulsion of the cells in analogy to the neuronal system. Further studies will be necessary to prove Slit activity in vivo.

Mammaglobin and maspin transcripts in blood may reflect disease progression and the effect of therapy in breast cancer

Detection of residual tumor cells in the circulation can provide prognostic as well as therapeutic information and help in identifying patients at high risk for developing metastases. Maspin and mammaglobin are two molecules that are specifically associated with breast cancer. We looked for mammaglobin and maspin transcripts in the peripheral blood of patients with breast cancer and evaluated their utility as a marker of the response to therapy. Maspin and mammaglobin transcripts were analyzed in 85 breast-cancer patients by nested RT-PCR, prior to and after treatment. Before therapy, 10 patients were found positive for mammaglobin and 20 patients were positive for maspin. In four patients, both transcripts were detected. Immediately following treatment, only one patient was still positive for mammaglobin while maspin transcripts persisted in three patients. Disease progression was observed mainly in patients in whom maspin transcripts were not detectable. Molecular detection of circulating tumor cells during therapy based on analysis for mammaglobin and maspin transcripts is an easy and practical method that can be applied to follow-up patients. We suggest that detection of mammaglobin mRNA is useful to determine the effect of therapy while maspin transcripts may indicate more aggressive disease.

Interleukin-6 trans-signalling differentially regulates proliferation, migration, adhesion and maspin expression in human prostate cancer cells

Interleukin-6 (IL-6) is suggested to have a pathogenic role in the progression of prostate cancer (PC), therefore representing an attractive target for new therapies. However, due to the pleiotropy of this cytokine, targeting IL-6 results in different and unpredictable responses. In order to better understand the mechanisms underlying the different responses to the cytokine, we focused our attention on IL-6 receptors (IL-6Rs) that represent the first element in the cascade of cytokine-activated signalling pathways. IL-6 signal transduction may indeed occur through the membrane IL-6R (classical signalling) and/or through the less studied soluble IL-6R (sIL-6R; IL-6 trans-signalling (IL-6TS)). We provide the first evidence how responses to IL-6 may depend on the different content of IL-6Rs in PC. In particular, the studies of (3)H-thymidine incorporation and exploitation of different approaches (i.e. activation or inhibition of IL-6TS in sIL-6R-negative and -positive cell lines and transfection of IL-6R siRNA) allowed us to demonstrate that IL-6TS specifically accounts for an anti-proliferative effect of the cytokine in three PC cell lines that are known to respond differently to IL-6. Additionally, by applying migration-, scratch- and adhesion assays, we show that IL-6TS increases motility and migration and decreases adhesion of prostate cells facilitating thereby processes that determine metastasis initiation and spread. Finally, by western analyses, we uncovered an IL-6- and sIL-6R-dependent downregulation of the tumour suppressor maspin. Collectively, these data suggest that selective targeting of IL-6TS might allow to refine the currently available experimental anti-IL-6 therapies against PC.

Role of the Netrin System of Repellent Factors on Synovial Fibroblasts in Rheumatoid Arthritis and Osteoarthritis

Changes in the expression of repellent factors, i.e., Netrins and their receptors, may be responsible for the invasive behavior of the synovial tissue cells in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). This study was carried out to analyze the expression of Netrins and their receptors in synovial cells of patients with RA, OA, and control subjects without synovial inflammation. Quantitative RT-PCR was performed to measure the expression of Netrin-1, −3, −4, Neogenin, DCC, UNC5A-D. The influence of Netrin-1 on synovial fibroblasts (SF) was analyzed by determining proliferation, migration, and their ability to organize collagen. SF expressed all repellent factors of the Netrin family. When comparing SF of healthy donors to patients with RA and OA, a stronger expression of UNC5B (4 fold) and UNC5C (769 fold) in RA and OA was found, whereas expression of the other molecules revealed no significant differences. Treating the SF-cells with recombinant Netrin-1 resulted in inhibition of migration of RA- and OA-SFs whereas control cells were not affected. The stronger expression of UNC5B and UNC5C receptors might contribute to the disordered phenotype of RA- and OA-SFs. Addition of Netrin-1 reduces the migratory ability of SFs, potentially by repulsion, as seen in neuronal cells in embryonic development. Due to its function, Netrin-1 may constitute a novel target in the treatment of OA and RA.

Loss of full length CtBP1 expression enhances the invasive potential of human melanoma

BACKGROUND

The C-terminal binding protein 1 (CtBP1) is a known co-repressor of gene transcription. We recently revealed that CtBP1 expression is lost in melanoma cells and melanoma inhibitory activity (MIA) expression is subsequently increased. The present study was performed to evaluate a more general role of CtBP1 in human melanoma and identify further CtBP1-regulated target genes.

METHODS

Sequence analysis and expression profile of CtBP1 in melanoma cell lines were done by PCR. Boyden Chamber assays and co-immunoprecipitation were performed to investigate the functional role of CtBP1. Gene expression analysis and micro array data were used to define target genes.

RESULTS

Interestingly, we detected an alternative splice product of CtBP1 with unknown function whose expression is induced at reduction of full length CtBP1. Overexpression of full length CtBP1 in melanoma cells had no effect on cell proliferation but did influence cell migration and invasiveness. To understand the effect of CtBP1 we identified putative LEF/TCF target genes found to be strongly expressed in melanoma using DNA microarray analysis. We focused on fourteen genes not previously associated with melanoma. Detailed analysis revealed that most of these were known to be involved in tumor metastasis. Eleven genes had expression profiles associated with melanoma cell invasiveness.

CONCLUSION

In summary, this study revealed that reduction of CtBP1 expression is correlated with migratory, invasive potential of melanoma cells.

Maspin modulates prostate cancer cell apoptotic and angiogenic response to hypoxia via targeting AKT

Hypoxia has been previously linked to the development of both benign prostatic hyperplasia and prostate cancer. This study investigated the effect of maspin, an extracellular matrix (ECM) tumor suppressor, on the apoptotic response of prostate cancer cells to hypoxia. Gene expression profiling of human benign and malignant prostate epithelial cells after exposure to hypoxia or normoxia revealed dramatic changes in ECM regulators. Maspin was found to be overexpressed in response to hypoxia in prostate cancer cells, but not in benign prostate cells. To dissect the contribution of maspin to tumor cell responses within a hypoxic microenvironment, we used maspin-overexpressing DU-145 human prostate cancer cells. Exposure to hypoxic conditions (1% O(2)) led to a significant increase in apoptosis in the DU-145 maspin cells, compared to DU-145 neo-transfectants without a significant effect on cell migration. This enhanced sensitivity to hypoxia-induced apoptosis leads to a significant suppression of tumor growth and tumor vascularity in vivo by targeting Akt and focal adhesion kinase activation. Our findings implicate maspin in prostate cancer cell response to hypoxia via recruitment of intracellular signaling partners. This study may have significance in the identification of maspin-driven therapeutic targeting in advanced metastatic prostate cancer.

Loss of nephronectin promotes tumor progression in malignant melanoma

Nephronectin (POEM) was originally identified as a factor involved in tissue morphogenesis. POEM has several characteristics of a matrix protein including an arg-gly-asp binding domain site that is recognized by integrins. Recently, deregulation of POEM was found in breast cancer. We therefore speculate that deregulation of POEM expression plays a role in the development or progression of malignant melanoma. Thus, we evaluated melanoma cell lines and tissue samples of malignant melanoma for POEM transcription. We found that POEM expression was reduced or lost in most cell lines and in all tumor samples analyzed. Reduced POEM expression occurred as early as in primary tumors detected by both immunohistochemical and reverse transcription-polymerase chain reaction analyses. Functional assays with stable POEM transfected cell lines revealed that POEM expression increased cell adhesion and decreased cell migration and invasion supporting a role of POEM in tumor progression. Interestingly, integrin alpha-8 expression, which was described as a receptor for POEM, is enhanced in malignant melanoma. Our studies thus indicate that loss of POEM expression may contribute to melanoma progression.

MASPIN subcellular localization and expression in oral cavity squamous cell carcinoma

MASPIN, a member of serpin superfamily, has multifaceted biological functions and an unique tumour suppressing activity. Experimental evidences showed that MASPIN suppresses tumour growth, angiogenesis, invasion and metastasis. Only a very limited number of studies considered MASPIN expression in the upper aero-digestive tract carcinomas. It was recently found that nuclear localization of MASPIN was significantly associated with lower recurrence rate and longer disease-free interval in laryngeal carcinoma. The present study investigated the biological and prognostic role of MASPIN in relation to its subcellular localization in oral carcinoma. Sub-cellular pattern of distribution of MASPIN, nuclear and cytoplasmic MASPIN expressions were immunohistochemically determined in 56 consecutive cases of oral carcinoma. Statistical analysis found a significant association between pN-stage and recurrence of disease (P=0.032) and a significantly longer disease-free interval in pN0 patients than in pN+ ones (P=0.038). None of the subcellular expressions of MASPIN was significantly correlated with recurrence of disease and disease-free interval in our series of oral carcinomas. Sixty-one percent of pN0 cases was strongly MASPIN-positive in the cytoplasm of primary carcinoma cells, 33% of the pN+ cases was MASPIN-positive in the cytoplasm. Statistical analysis found a significant association between MASPIN cytoplasmic expression and pN-stage (P=0.032). Negative MASPIN immunoreactivity in carcinoma cells cytoplasm may be useful to identify patients at risk of disease disseminating to neck lymph nodes. Further investigations are necessary to understand the biological role of cytoplasmic MASPIN localization in oral carcinoma.

Epigenetic events in malignant melanoma

Irreversible changes in the DNA sequence, including chromosomal deletions or amplification, activating or inactivating mutations in genes, have been implicated in the development and progression of melanoma. However, increasing attention is being turned towards the participation of 'epigenetic' events in melanoma progression that do not affect DNA sequence, but which nevertheless may lead to stable inherited changes in gene expression. Epigenetic events including histone modifications and DNA methylation play a key role in normal development and are crucial to establishing the correct program of gene expression. In contrast, mistargeting of such epigenetic modifications can lead to aberrant patterns of gene expression and loss of anti-cancer checkpoints. Thus, to date at least 50 genes have been reported to be dysregulated in melanoma by aberrant DNA methylation and accumulating evidence also suggests that mistargetting of histone modifications and altered chromatin remodeling activities will play a key role in melanoma. This review gives an overview of the many different types of epigenetic modifications and their involvement in cancer and especially in melanoma development and progression.