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

Tissue factor pathway inhibitor-2 inhibits integrin β1 activation and focal adhesion formation and suppresses peritoneal ovarian cancer dissemination in mice

Tissue factor pathway inhibitor-2 (TFPI2) is a Kunitz-type serine protease inhibitor and an ovarian clear cell carcinoma (CCC) biomarker. TFPI2 is expressed in several cancers and exerts tumor-suppressive effects; however, the role of TFPI2 in the CCC cell phenotype remains unclear. Therefore, in this study, we investigated the function of TFPI2 by establishing a gene knockout (KO) in ES-2 CCC cells and observed the change in phenotypes in vitro and in vivo. TFPI2 KO inhibited ES-2 cell proliferation, increased extracellular matrix protein adhesion, enhanced focal adhesion formation and activated integrin β1 cell surface clustering in vitro, and markedly increased ES-2 tumor growth and dissemination in the peritoneal cavity of a mouse xenograft model. These findings suggest a novel function of TFPI2 expression in suppressing the formation of focal adhesions in CCC cells, potentially by activating integrin β1. This function plays a role in the peritoneal growth characteristics of CCC cells.

STC1 competitively binding βPIX enhances melanoma progression via YAP nuclear translocation and M2 macrophage recruitment through the YAP/CCL2/VEGFA/AKT feedback loop

This study investigates the role of Stanniocalcin-1 (STC1) in melanoma progression, with a focus on its impact on metastasis, angiogenesis, and immune evasion. Systematic bioinformatics analysis revealed the potential influence of STC1 dysregulation on prognosis, immune cell infiltration, response to immune therapy, and cellular functions. In vitro assays were conducted to assess the proliferation, invasion, migration, and angiogenesis capabilities of A375 cells. In vivo experiments utilizing C57BL/6 J mice established a lung metastasis model using B16-F10 cells to evaluate macrophage infiltration and M2 polarization. A Transwell co-culture system was employed to explore the crosstalk between melanoma and macrophages. Molecular interactions among STC1, YAP, βPIX, and CCL2 are investigated using mass spectrometry, Co-Immunoprecipitation, Dual-Luciferase Reporter Assay, and Chromatin Immunoprecipitation experiments. STC1 was found to enhance lung metastasis by promoting the recruitment and polarization of M2 macrophages, thereby fostering an immunosuppressive microenvironment. Mechanistically, STC1 competes with YAP for binding to βPIX within the KER domain in melanoma cells, leading to YAP activation and subsequent CCL2 upregulation. CCL2-induced M2 macrophages secrete VEGFA, which enhances tumor vascularization and increases STC1 expression via the AKT signaling pathway in melanoma cells, establishing a pro-metastatic feedback loop. Notably, STC1-induced YAP activation increases PD-L1 expression, promoting immune evasion. Silencing STC1 enhances the efficacy of PD-1 immune checkpoint therapy in mice. This research elucidates STC1's role in melanoma metastasis and its complex interactions with tumor-associated macrophages, proposing STC1 as a potential therapeutic target for countering melanoma metastasis and augmenting the efficacy of PD-1 immunotherapy.

Organoids and metastatic orthotopic mouse model for mismatch repair-deficient colorectal cancer

Background

Genome integrity is essential for the survival of an organism. DNA mismatch repair (MMR) genes (e.g., MLH1, MSH2, MSH6, and PMS2) play a critical role in the DNA damage response pathway for genome integrity maintenance. Germline mutations of MMR genes can lead to Lynch syndrome or constitutional mismatch repair deficiency syndrome, resulting in an increased lifetime risk of developing cancer characterized by high microsatellite instability (MSI-H) and high mutation burden. Although immunotherapy has been approved for MMR-deficient (MMRd) cancer patients, the overall response rate needs to be improved and other management options are needed.

Methods

To better understand the biology of MMRd cancers, elucidate the resistance mechanisms to immune modulation, and develop vaccines and therapeutic testing platforms for this high-risk population, we generated organoids and an orthotopic mouse model from intestine tumors developed in a Msh2-deficient mouse model, and followed with a detailed characterization.

Results

The organoids were shown to be of epithelial origin with stem cell features, to have a high frameshift mutation frequency with MSI-H and chromosome instability, and intra- and inter-tumor heterogeneity. An orthotopic model using intra-cecal implantation of tumor fragments derived from organoids showed progressive tumor growth, resulting in the development of adenocarcinomas mixed with mucinous features and distant metastasis in liver and lymph node.

Conclusions

The established organoids with characteristics of MSI-H cancers can be used to study MMRd cancer biology. The orthotopic model, with its distant metastasis and expressing frameshift peptides, is suitable for evaluating the efficacy of neoantigen-based vaccines or anticancer drugs in combination with other therapies.

A Reconstructed Human Melanoma-in-Skin Model to Study Immune Modulatory and Angiogenic Mechanisms Facilitating Initial Melanoma Growth and Invasion

Invasion, immune modulation, and angiogenesis are crucial in melanoma progression. Studies based on animals or two-dimensional cultures poorly recapitulate the tumor-microenvironmental cross-talk found in humans. This highlights a need for more physiological human models to better study melanoma features. Here, six melanoma cell lines (A375, COLO829, G361, MeWo, RPMI-7951, and SK-MEL-28) were used to generate an in vitro three-dimensional human melanoma-in-skin (Mel-RhS) model and were compared in terms of dermal invasion and immune modulatory and pro-angiogenic capabilities. A375 displayed the most invasive phenotype by clearly expanding into the dermal compartment, whereas COLO829, G361, MeWo, and SK-MEL-28 recapitulated to different extent the initial stages of melanoma invasion. No nest formation was observed for RPMI-7951. Notably, the integration of A375 and SK-MEL-28 cells into the model resulted in an increased secretion of immune modulatory factors (e.g., M-CSF, IL-10, and TGFβ) and pro-angiogenic factors (e.g., Flt-1 and VEGF). Mel-RhS-derived supernatants induced endothelial cell sprouting in vitro. In addition, observed A375-RhS tissue contraction was correlated to increased TGFβ release and α-SMA expression, all indicative of differentiation of fibroblasts into cancer-associated fibroblast-like cells and reminiscent of epithelial-to-mesenchymal transition, consistent with A375's most prominent invasive behavior. In conclusion, we successfully generated several Mel-RhS models mimicking different stages of melanoma progression, which can be further tailored for future studies to investigate individual aspects of the disease and serve as three-dimensional models to assess efficacy of therapeutic strategies.

Plasma exosome-derived connexin43 as a promising biomarker for melanoma patients

BACKGROUND

To examine the levels of exosome-derived connexin 43 (Cx43) in plasma and estimate its forecast value in patients with melanoma.

METHODS

We measured the plasma exosome-derived Cx43 levels in the plasma of 112 melanoma patients and 50 healthy controls.

RESULTS

The plasma exosome-derived Cx43 levels in patients with melanoma were substantially downregulated as opposed to the levels in healthy controls (P < 0.001). Kaplan-Meier analysis indicated that overall survival (OS) and disease-free survival (DFS) were poorer in patients with melanoma who exhibited lower levels of plasma exosome-derived Cx43 (both P < 0.001). The levels of plasma exosome-derived Cx43 were considerably elevated in patients with melanoma whose tumor was situated in the skin, tumor size < 10 cm, with Clark level I-III, TNM stages IIb-IV, and had no lymph node metastasis as opposed to patients whose tumor was situated in the viscera or mucosa, tumor size ≥ 10 cm, Clark level IV-V, TNM stages IIb-IV and had lymph node metastasis (all P < 0.05). The receiver operating characteristic (ROC) of plasma exosome-derived Cx43 for forecasting 5-year DFS in patients with melanoma was 0.78 (95% confidence interval (CI): 0.70-0.86), with a specificity of 77.78% and a sensitivity of 81.55%. The ROC of plasma exosome-derived Cx43 for forecasting 5-year OS of patients with melanoma was 0.77 (95% CI: 0.68-0.84), with a specificity of 80.0% and sensitivity of 65.98%.

CONCLUSION

The overall findings indicated that the levels of plasma exosome-derived Cx43 in patients with melanoma were considerably downregulated. It can therefore be inferred that the levels of plasma exosome-derived Cx43 might be a prospective prognostic indicator for 5 5-year OS and 5-year DFS of patients with melanoma.

ADAMTS13 protease or lack of von Willebrand factor protects irradiation and melanoma-induced thrombotic microangiopathy in zebrafish

BACKGROUND

Severe deficiency of plasma ADAMTS13 activity may result in potentially fatal thrombotic thrombocytopenic purpura and relative deficiency of plasma ADAMTS13 activity may be associated with adverse outcomes of certain malignancies. Here, we report the role of ADAMTS13 or lack of von Willebrand factor (VWF) in reducing irradiation and melanoma-induced thrombotic microangiopathy (TMA) and mortality in zebrafish.

METHODS

Zebrafish melanoma cell line (ZMEL) was injected subcutaneously into wild-type (wt), adamts13-/- (a13-/- ), von Willebrand factor (vwf-/- ), and a13-/- vwf-/- zebrafish following total body irradiation; the tumor growth, its gene expression pattern, the resulting thrombocytopenia, and the mortality were determined.

RESULTS

Total body irradiation at 30 Gy alone resulted in a transient thrombocytopenia in both wt and a13-/- zebrafish. However, thrombocytopenia occurred earlier and more profound in a13-/- than in wt zebrafish, which was resolved 2 weeks following irradiation alone. An inoculation of ZMEL following the irradiation resulted in more severe and persistent thrombocytopenia, as well as earlier death in a13-/- than in wt zebrafish. The vwf-/- or a13-/- vwf-/- zebrafish were protected from developing severe thrombocytopenia following the same maneuvers. RNA-sequencing revealed significant differentially expressed genes associated with oxidation-reduction, metabolism, lipid, fatty acid and cholesterol metabolic processes, steroid synthesis, and phospholipid efflux in the melanoma explanted from a13-/- zebrafish compared with that from the wt controls.

CONCLUSIONS

Our results indicated that plasma ADAMTS13 or lack of VWF may offer a significant protection against the development of irradiation- and/or melanoma-induced TMA. Such a microenvironment may directly affect melanoma cell phenotypes via alternation in the oxidation-reduction and lipid metabolic pathways.

cAMP Signaling in Cancer: A PKA-CREB and EPAC-Centric Approach

Cancer is one of the most common causes of death globally. Despite extensive research and considerable advances in cancer therapy, the fundamentals of the disease remain unclear. Understanding the key signaling mechanisms that cause cancer cell malignancy may help to uncover new pharmaco-targets. Cyclic adenosine monophosphate (cAMP) regulates various biological functions, including those in malignant cells. Understanding intracellular second messenger pathways is crucial for identifying downstream proteins involved in cancer growth and development. cAMP regulates cell signaling and a variety of physiological and pathological activities. There may be an impact on gene transcription from protein kinase A (PKA) as well as its downstream effectors, such as cAMP response element-binding protein (CREB). The position of CREB downstream of numerous growth signaling pathways implies its oncogenic potential in tumor cells. Tumor growth is associated with increased CREB expression and activation. PKA can be used as both an onco-drug target and a biomarker to find, identify, and stage tumors. Exploring cAMP effectors and their downstream pathways in cancer has become easier using exchange protein directly activated by cAMP (EPAC) modulators. This signaling system may inhibit or accelerate tumor growth depending on the tumor and its environment. As cAMP and its effectors are critical for cancer development, targeting them may be a useful cancer treatment strategy. Moreover, by reviewing the material from a distinct viewpoint, this review aims to give a knowledge of the impact of the cAMP signaling pathway and the related effectors on cancer incidence and development. These innovative insights seek to encourage the development of novel treatment techniques and new approaches.

UVB-Induced Microvesicle Particle Release and Its Effects on the Cutaneous Microenvironment

Ultraviolet B radiation (UVB) has profound effects on human skin that results in a broad spectrum of immunological local and systemic responses and is the major cause of skin carcinogenesis. One important area of study in photobiology is how UVB is translated into effector signals. As the skin is exposed to UVB light, subcellular microvesicle particles (MVP), a subtype of bioactive extracellular vesicles, are released causing a variety of local and systemic immunological effects. In this review, we highlight keratinocyte MVP release in keratinocytes in response to UVB. Specifically, Platelet-activating factor receptor agonists generated by UVB result in MVP released from keratinocytes. The downstream effects of MVP release include the ability of these subcellular particles to transport agents including the glycerophosphocholine-derived lipid mediator Platelet-activating factor (PAF). Moreover, even though UVB is only absorbed in the epidermis, it appears that PAF release from MVPs also mediates systemic immunosuppression and enhances tumor growth and metastasis. Tumor cells expressing PAF receptors can use this mechanism to evade chemotherapy responses, leading to treatment resistance for advanced cancers such as melanoma. Furthermore, novel pharmacological agents provide greater insight into the UVB-induced immune response pathway and a potential target for pharmacological intervention. This review outlines the need to more clearly elucidate the mechanism linking UVB-irradiation with the cutaneous immune response and its pathological manifestations. An improved understanding of this process can result in new insights and treatment strategies for UVB-related disorders from carcinogenesis to photosensitivity.

Targeting GPCRs and Their Signaling as a Therapeutic Option in Melanoma

Simple Summary

Sixteen G-protein-coupled receptors (GPCRs) have been involved in melanogenesis or melanomagenesis. Here, we review these GPCRs, their associated signaling, and therapies.

Abstract

G-protein-coupled receptors (GPCRs) serve prominent roles in melanocyte lineage physiology, with an impact at all stages of development, as well as on mature melanocyte functions. GPCR ligands are present in the skin and regulate melanocyte homeostasis, including pigmentation. The role of GPCRs in the regulation of pigmentation and, consequently, protection against external aggression, such as ultraviolet radiation, has long been established. However, evidence of new functions of GPCRs directly in melanomagenesis has been highlighted in recent years. GPCRs are coupled, through their intracellular domains, to heterotrimeric G-proteins, which induce cellular signaling through various pathways. Such signaling modulates numerous essential cellular processes that occur during melanomagenesis, including proliferation and migration. GPCR-associated signaling in melanoma can be activated by the binding of paracrine factors to their receptors or directly by activating mutations. In this review, we present melanoma-associated alterations of GPCRs and their downstream signaling and discuss the various preclinical models used to evaluate new therapeutic approaches against GPCR activity in melanoma. Recent striking advances in our understanding of the structure, function, and regulation of GPCRs will undoubtedly broaden melanoma treatment options in the future.

The Role of the CREB Protein Family Members and the Related Transcription Factors in Radioresistance Mechanisms

In the framework of space flight, the risk of radiation carcinogenesis is considered a "red" risk due to the high likelihood of occurrence as well as the high potential impact on the quality of life in terms of disease-free survival after space missions. The cyclic AMP response element-binding protein (CREB) is overexpressed both in haematological malignancies and solid tumours and its expression and function are modulated following irradiation. The CREB protein is a transcription factor and member of the CREB/activating transcription factor (ATF) family. As such, it has an essential role in a wide range of cell processes, including cell survival, proliferation, and differentiation. Among the CREB-related nuclear transcription factors, NF-κB and p53 have a relevant role in cell response to ionising radiation. Their expression and function can decide the fate of the cell by choosing between death or survival. The aim of this review was to define the role of the CREB/ATF family members and the related transcription factors in the response to ionising radiation of human haematological malignancies and solid tumours.

Sorafenib treatment of metastatic melanoma with c-Kit aberration reduces tumor growth and promotes survival

Melanomas are highly malignant tumors that readily metastasize and have poor prognosis. Targeted therapy is a cornerstone of treatment for patients with melanoma. Although c-Kit gene aberration has found in 5-10% of melanoma cases, research on c-Kit inhibitors for melanoma with c-Kit aberration have been disappointing. Sorafenib is a tyrosine kinase inhibitor, whose targets include c-Kit, platelet derived growth factor receptor (PDGFR), VEGFR and RAF. The present study aimed to examine the effect of sorafenib on metastatic melanoma with c-Kit aberration. Cell viability was assessed via trypan blue assay. Migration and invasion were analyzed using cell culture inserts. The anti-metastatic effects and antitumour activity of sorafenib were determined in an in vivo model. Protein expression was detected via western blotting, and the expression of MMP and very late antigen (VLA) was detected via reverse transcription-quantitative PCR. It was identified that sorafenib decreased cell viability, migration and invasion in vitro. Furthermore, sorafenib inhibited metastasis and tumor growth in vivo. Mechanistically, sorafenib inhibited c-Kit, PDGFR, VEGFR, B-Raf and c-Raf phosphorylation both in vitro and in vivo. In addition, sorafenib reduced the expression levels of MMPs and VLA. Importantly, there was a significant effect of sorafenib treatment on overall survival in mice. Collectively, this study suggests that sorafenib may serve as a novel therapeutic option for melanoma with c-Kit dysregulation.

The Platelet-Activating Factor Receptor's Association with the Outcome of Ovarian Cancer Patients and Its Experimental Inhibition by Rupatadine

The platelet-activating factor receptor (PAFR) and its ligand (PAF) are important inflammatory mediators that are overexpressed in ovarian cancer. The receptor is an important player in ovarian cancer development. In this study, we aimed to evaluate the prognostic value of PAFR in epithelial ovarian cancer (EOC) and the potential use of its antagonist, rupatadine, as an experimental treatment. Tissue microarrays of ovarian cancer patients, most markedly those with a non-mucinous subtype, immunohistochemically overexpressed PAFR. Elevated cytoplasmic PAFR expression was found to significantly and independently impair patients' overall and recurrence-free survival (OS: median 83.48 vs. 155.03 months; p = 0.022; RFS: median 164.46 vs. 78.03 months; p = 0.015). In vitro, the serous ovarian cancer subtypes especially displayed an elevated PAFR gene and protein expression. siRNA knockdown of PAFR decreased cell proliferation significantly, thus confirming the receptor's protumorigenic effect on ovarian cancer cells. The clinically approved PAFR antagonist rupatadine effectively inhibited in vitro cell proliferation and migration of ovarian cancer cells. PAFR is a prognostic marker in ovarian cancer patients and its inhibition through rupatadine may have important therapeutic implications in the therapy of ovarian cancer patients.

Multi-Omics Analysis Identifying Key Biomarkers in Ovarian Cancer

Ovarian cancer is one of the most common malignant tumors. Here, we aimed to study the expression and function of the CREB1 gene in ovarian cancer via the bioinformatic analyses of multiple databases. Previously, the prognosis of ovarian cancer was based on single-factor or single-gene studies. In this study, different bioinformatics tools (such as TCGA, GEPIA, UALCAN, MEXPRESS, and Metascape) have been used to assess the expression and prognostic value of the CREB1 gene. We used the Reactome and cBioPortal databases to identify and analyze CREB1 mutations, copy number changes, expression changes, and protein-protein interactions. By analyzing data on the CREB1 differential expression in ovarian cancer tissues and normal tissues from 12 studies collected from the "Human Protein Atlas" database, we found a significantly higher expression of CREB1 in normal ovarian tissues. Using this database, we collected information on the expression of 25 different CREB-related proteins, including TP53, AKT1, and AKT3. The enrichment of these factors depended on tumor metabolism, invasion, proliferation, and survival. Individualized tumors based on gene therapy related to prognosis have become a new possibility. In summary, we established a new type of prognostic gene profile for ovarian cancer using the tools of bioinformatics.

Connexins in melanoma: Potential role of Cx46 in its aggressiveness

Melanoma is the most aggressive skin cancer, and in metastatic advanced states, it is completely refractory to chemotherapy. Therefore, it is relevant to understand the molecular bases that rule their aggressiveness. Connexins (Cxs) are proteins that under normal physiological conditions participate in intercellular communication, via the exchange of signaling molecules between the cytoplasm and extracellular milieu and the exchange of ions/second messengers between the cytoplasm of contacting cells. These proteins have shown important roles in cancer progression, chemo- and radiotherapy resistance, and metastasis. Accordingly, Cx26 and Cx43 seem to play important roles in melanoma progression and metastasis. On the other hand, Cx46 is typically expressed in the eye lens, where it seems to be associated with oxidative stress protection in fiber lens cells. However, in the last decade, Cx46 expression has been associated with breast and brain cancers, due to its role in potentiation of both extracellular vesicle release and cancer stem cell-like properties. In this review, we analyzed a potential role of Cx46 as a new biomarker and therapeutic target in melanoma.

Graphene Oxide Normal (GO + Mn2+) and Ultrapure: Short-Term Impact on Selected Antioxidant Stress Markers and Cytokines in NHDF and A549 Cell Lines

Since biological applications and toxicity of graphene-based materials are structure dependent, studying their interactions with the biological systems is very timely and important. We studied short-term (1, 24, and 48 h) effects of ultrapure (GO) and Mn²⁺-contaminated (GOS) graphene oxide on normal human dermal fibroblasts (NHDF) and adenocarcinomic human alveolar basal epithelial cells (A549) using selected oxidative stress markers and cytokines: glutathione reductase (GR) and catalase (CAT) activity, total antioxidative capacity (TAC), and malondialdehyde (MDA) concentration, levels of vascular endothelial growing factor (VEGF), tumor necrosis factor-alpha (TNF-α), platelet-derived growth factor-BB (PDGF-BB), and eotaxin. GOS induced higher levels of oxidative stress, measured with CAT activity, TAC, and MDA concentration than GO in both cell lines when compared to control cells. GR activity decreased in time in NHDF cells but increased in A549 cells. The levels of cytokines were related to the exposure time and graphene oxide type in both analyzed cell lines and their levels comparably increased over time. We observed higher TNF-α levels in NHDF and higher levels of VEGF and eotaxin in the A549 cell line. Both types of cells showed similar susceptibility to GO and GOS. We concluded that the short-time exposure to GOS induced the stronger response of oxidative stress markers without collapsing the antioxidative systems of analysed cells. Increased levels of inflammatory cytokines after GO and GOS exposure were similar both in NHDF and A549 cells.

Cell Adhesion Molecules in Plasticity and Metastasis

Prior to metastasis, modern therapeutics and surgical intervention can provide a favorable long-term survival for patients diagnosed with many types of cancers. However, prognosis is poor for patients with metastasized disease. Melanoma is the deadliest form of skin cancer, yet in situ and localized, thin melanomas can be biopsied with little to no postsurgical follow-up. However, patients with metastatic melanoma require significant clinical involvement and have a 5-year survival of only 34% to 52%, largely dependent on the site of colonization. Melanoma metastasis is a multi-step process requiring dynamic changes in cell surface proteins regulating adhesiveness to the extracellular matrix (ECM), stroma, and other cancer cells in varied tumor microenvironments. Here we will highlight recent literature to underscore how cell adhesion molecules (CAM) contribute to melanoma disease progression and metastasis.

What turns CREB on? And off? And why does it matter?

Altered expression and function of the transcription factor cyclic AMP response-binding protein (CREB) has been identified to play an important role in cancer and is associated with the overall survival and therapy response of tumor patients. This review focuses on the expression and activation of CREB under physiologic conditions and in tumors of distinct origin as well as the underlying mechanisms of CREB regulation by diverse stimuli and inhibitors. In addition, the clinical relevance of CREB is summarized, including its use as a prognostic and/or predictive marker as well as a therapeutic target.

Cyclic adenosine monophosphate (cAMP) signaling in melanocyte pigmentation and melanomagenesis

The second messenger cyclic adenosine monophosphate (cAMP) regulates numerous functions in both benign melanocytes and melanoma cells. cAMP is generated from two distinct sources, transmembrane and soluble adenylyl cyclases (tmAC and sAC, respectively), and is degraded by a family of proteins called phosphodiesterases (PDEs). cAMP signaling can be regulated in many different ways and can lead to varied effects in melanocytes. It was recently revealed that distinct cAMP signaling pathways regulate pigmentation by either altering pigment gene expression or the pH of melanosomes. In the context of melanoma, many studies report seemingly contradictory roles for cAMP in tumorigenesis. For example, cAMP signaling has been implicated in both cancer promotion and suppression, as well as both therapy resistance and sensitization. This conundrum in the field may be explained by the fact that cAMP signals in discrete microdomains and each microdomain can mediate differential cellular functions. Here, we review the role of cAMP signaling microdomains in benign melanocyte biology, focusing on pigmentation, and in melanomagenesis.

The lncRNA SLNCR Recruits the Androgen Receptor to EGR1-Bound Genes in Melanoma and Inhibits Expression of Tumor Suppressor p21

Melanoma is the deadliest form of skin cancer, affecting men more frequently and severely than women. Although recent studies suggest that differences in activity of the androgen receptor (AR) underlie the observed sex bias, little is known about AR activity in melanoma. Here we show that AR and EGR1 bind to the long non-coding RNA SLNCR and increase melanoma proliferation through coordinated transcriptional regulation of several growth-regulatory genes. ChIP-seq reveals that ligand-free AR is enriched on SLNCR-regulated melanoma genes and that AR genomic occupancy significantly overlaps with EGR1 at consensus EGR1 binding sites. We present a model in which SLNCR recruits AR to EGR1-bound genomic loci and switches EGR1-mediated transcriptional activation to repression of the tumor suppressor p21^Waf1/Cip1. Our data implicate the regulatory triad of SLNCR, AR, and EGR1 in promoting oncogenesis and may help explain why men have a higher incidence of and more rapidly progressive melanomas compared with women.

Research of the mechanism on miRNA193 in exosomes promotes cisplatin resistance in esophageal cancer cells

Purpose

Chemotherapy resistance of esophageal cancer is a key factor affecting the postoperative treatment of esophageal cancer. Among the media that transmit signals between cells, the exosomes secreted by tumor cells mediate information transmission between tumor cells, which can make sensitive cells obtain resistance. Although some cellular exosomes play an important role in tumor’s acquired drug resistance, the related action mechanism is still not explored specifically.

Methods

To elucidate this process, we constructed a cisplatin-resistant esophageal cancer cell line, and proved that exosomes conferring cellular resistance in esophageal cancer can promote cisplatin resistance in sensitive cells. Through high-throughput sequencing analysis of the exosome and of cells after stimulation by exosomes, we determined that the miRNA193 in exosomes conferring cellular resistance played a key role in sensitive cells acquiring resistance to cisplatin. In vitro experiments showed that miRNA193 can regulate the cell cycle of esophageal cancer cells and inhibit apoptosis, so that sensitive cells can acquire resistance to cisplatin. An in vivo experiment proved that miRNA193 can promote tumor proliferation through the exosomes, and provide sensitive cells with slight resistance to cisplatin.

Results

Small RNA sequencing of exosomes showed that exosomes in drug-resistant cells have 189 up-regulated and 304 down-regulated miRNAs; transcriptome results showed that drug-sensitive cells treated with drug-resistant cellular exosomes have 3446 high-expression and 1709 low-expression genes; correlation analysis showed that drug-resistant cellular exosomes mainly affect the drug resistance of sensitive cells through paths such as cytokine–cytokine receptor interaction, and the VEGF and Jak-STAT signaling pathways; miRNA193, one of the high-expression miRNAs in drug-resistant cellular exosomes, can promote drug resistance by removing cisplatin’s inhibition of the cell cycle of sensitive cells.

Conclusion

Sensitive cells can become resistant to cisplatin through acquired drug-resistant cellular exosomes, and miRNA193 can make tumor cells acquire cisplatin resistance by regulating the cell cycle.

Hypoxia-mediated alterations and their role in the HER-2/neuregulated CREB status and localization

The cAMP-responsive element-binding protein (CREB) is involved in the tumorigenicity of HER-2/neu-overexpressing murine and human tumor cells, but a link between the HER-2/neu-mediated CREB activation, its posttranslational modification and localization and changes in the cellular metabolism, due to an altered (tumor) microenvironment remains to be established. The present study demonstrated that shRNA-mediated silencing of CREB in HER-2/neu-transformed cells resulted in decreased tumor formation, which was associated with reduced angiogenesis, but increased necrotic and hypoxic areas in the tumor. Hypoxia induced pCREBSer133, but not pCREBSer121 expression in HER-2/neu-transformed cells. This was accompanied by upregulation of the hypoxia-inducible genes GLUT1 and VEGF, increased cell migration and matrix metalloproteinase-mediated invasion. Treatment of HER-2/neu+ cells with signal transduction inhibitors targeting in particular HER-2/neu was able to revert hypoxia-controlled CREB activation. In addition to changes in the phosphorylation, hypoxic response of HER-2/neu+ cells caused a transient ubiquitination and SUMOylation as well as a co-localization of nuclear CREB to the mitochondrial matrix. A mitochondrial localization of CREB was also demonstrated in hypoxic areas of HER-2/neu+ mammary carcinoma lesions. This was accompanied by an altered gene expression pattern, activity and metabolism of mitochondria leading to an increased respiratory rate, oxidative phosphorylation and mitochondrial membrane potential and consequently to an enhanced apoptosis and reduced cell viability. These data suggest that the HER-2/neu-mediated CREB activation caused by a hypoxic tumor microenvironment contributes to the neoplastic phenotype of HER-2/neu+ cells at various levels.

Control of CREB expression in tumors: from molecular mechanisms and signal transduction pathways to therapeutic target

The cyclic AMP response element binding (CREB) protein has pleiotropic activities in physiologic processes. Due to its central position downstream of many growth signaling pathways CREB has the ability to influence cell survival, growth and differentiation of normal, but also of tumor cells suggesting an oncogenic potential of CREB. Indeed, increased CREB expression and activation is associated with tumor progression, chemotherapy resistance and reduced patients' survival. We summarize here the different cellular functions of CREB in tumors of distinct histology as well as its use as potential prognostic marker. In addition, the underlying molecular mechanisms to achieve constitutive activation of CREB including structural alterations, such as gene amplification and chromosomal translocation, and deregulation, which could occur at the transcriptional, post-transcriptional and post-translational level, will be described. Since downregulation of CREB by different strategies resulted in inhibition of cell proliferation, invasion and induction of apoptosis, the role of CREB as a promising target for cancer therapy will be also discussed.

In vitro inhibited effect of gap junction composed of Cx43 in the invasion and metastasis of testicular cancer resistanced to cisplatin

The effect of gap junction intercellular communication composed of connexin on cancer invasion/metastasis has been thoroughly explored; however, its effect on testicular cancer resistanced to chemotherapy is still unclear. In this study, we found that the capability of invasion and migration of I-10/DDP (cisplatin (DDP)-resistance) cells were elevated. Furthermore, the expression of Cx43 and the function of gap junction (GJ) in I-10/DDP cells were decreased compared with parental I-10 cells. Pharmacological inhibition of GJs by oleamide (Olea) enhanced invasion and migration. However, enhancement of GJs by retinoic acid (RA) decreased invasion and migration of I-10/DDP cells. To further clarify the invasion/migration inhibited effect of GJ in the testicular cancer resistanced to DDP, GJ function was modulated by overexpression and knockdown of Cx43 expression. Overexpression of Cx43 reduced invasion and migration of I-10/DDP cells. Conversely, knockdown of Cx43 expression increased invasion and migration of I-10/DDP cells. In summary, GJ composed of Cx43 inhibits I-10/DDP cells invasion and migration, and it may become the potential therapeutic target for testicular cancer chemotherapy.

EPAC-RAP1 Axis-Mediated Switch in the Response of Primary and Metastatic Melanoma to Cyclic AMP

Cyclic AMP (cAMP) is an important second messenger that regulates a wide range of physiologic processes. In mammalian cutaneous melanocytes, cAMP-mediated signaling pathways activated by G-protein-coupled receptors (GPCR), like melanocortin 1 receptor (MC1R), play critical roles in melanocyte homeostasis including cell survival, proliferation, and pigment synthesis. Impaired cAMP signaling is associated with increased risk of cutaneous melanoma. Although mutations in MAPK pathway components are the most frequent oncogenic drivers of melanoma, the role of cAMP in melanoma is not well understood. Here, using the Braf(V600E)/Pten-null mouse model of melanoma, topical application of an adenylate cyclase agonist, forskolin (a cAMP inducer), accelerated melanoma tumor development in vivo and stimulated the proliferation of mouse and human primary melanoma cells, but not human metastatic melanoma cells in vitro The differential response of primary and metastatic melanoma cells was also evident upon pharmacologic inhibition of the cAMP effector protein kinase A. Pharmacologic inhibition and siRNA-mediated knockdown of other cAMP signaling pathway components showed that EPAC-RAP1 axis, an alternative cAMP signaling pathway, mediates the switch in response of primary and metastatic melanoma cells to cAMP. Evaluation of pERK levels revealed that this phenotypic switch was not correlated with changes in MAPK pathway activity. Although cAMP elevation did not alter the sensitivity of metastatic melanoma cells to BRAF(V600E) and MEK inhibitors, the EPAC-RAP1 axis appears to contribute to resistance to MAPK pathway inhibition. These data reveal a MAPK pathway-independent switch in response to cAMP signaling during melanoma progression.Implications: The prosurvival mechanism involving the cAMP-EPAC-RAP1 signaling pathway suggest the potential for new targeted therapies in melanoma. Mol Cancer Res; 15(12); 1792-802. ©2017 AACR.

Linking CREB function with altered metabolism in murine fibroblast-based model cell lines

The cAMP-responsive element binding protein CREB is frequently overexpressed and activated in tumors of distinct histology, leading to enhanced proliferation, migration, invasion and angiogenesis as well as reduced apoptosis. The de-regulated expression of CREB might be linked with transcriptional as well as post-transcriptional regulation mechanisms. We show here that altered CREB expression levels and function are associated with changes in the cellular metabolism. Using comparative proteome-based analysis an altered expression pattern of proteins involved in the cellular metabolism in particular in glycolysis was found upon CREB down-regulation in HER-2/neu-transfected cell lines. This was associated with diminished expression levels of the glucose transporter 1, reduced glucose uptake and reduced glycolytic activity in HER-2/neu-transfected cells with down-regulated CREB when compared to HER-2/neu⁺ cells. Furthermore, hypoxia-induced CREB activity resulted in changes of the metabolism in HER-2/neu transfected cells. Low pH values in the supernatant of HER-2/neu transformants were restored by CREB down-regulation, but further decreased by hypoxia. The altered intracellular pH values were associated with a distinct expression of lactate dehydrogenase, and its substrate lactate. Moreover, enhanced phosphorylation of CREB on residue Ser133 was accompanied by a down-regulation of pERK and an up-regulation of pAKT. CREB promotes the detoxification of ROS by catalase, therefore protecting the mitochondrial activity under oxidative stress. These data suggest that there might exists a link between CREB function and the altered metabolism in HER-2/neu-transformed cells. Thus, targeting these altered metabolic pathways might represent an attractive therapeutic approach at least for the treatment of patients with HER-2/neu overexpressing tumors.

Comprehensive DNA methylation study identifies novel progression-related and prognostic markers for cutaneous melanoma

BACKGROUND

Cutaneous melanoma is the deadliest skin cancer, with an increasing incidence and mortality rate. Currently, staging of patients with primary melanoma is performed using histological biomarkers such as tumor thickness and ulceration. As disruption of the epigenomic landscape is recognized as a widespread feature inherent in tumor development and progression, we aimed to identify novel biomarkers providing additional clinical information over current factors using unbiased genome-wide DNA methylation analyses.

METHODS

We performed a comprehensive DNA methylation analysis during all progression stages of melanoma using Infinium HumanMethylation450 BeadChips on a discovery cohort of benign nevi (n = 14) and malignant melanoma from both primary (n = 33) and metastatic (n = 28) sites, integrating the DNA methylome with gene expression data. We validated the discovered biomarkers in three independent validation cohorts by pyrosequencing and immunohistochemistry.

RESULTS

We identified and validated biomarkers for, and pathways involved in, melanoma development (e.g., HOXA9 DNA methylation) and tumor progression (e.g., TBC1D16 DNA methylation). In addition, we determined a prognostic signature with potential clinical applicability and validated PON3 DNA methylation and OVOL1 protein expression as biomarkers with prognostic information independent of tumor thickness and ulceration.

CONCLUSIONS

Our data underscores the importance of epigenomic regulation in triggering metastatic dissemination through the inactivation of central cancer-related pathways. Inactivation of cell-adhesion and differentiation unleashes dissemination, and subsequent activation of inflammatory and immune system programs impairs anti-tumoral defense pathways. Moreover, we identify several markers of tumor development and progression previously unrelated to melanoma, and determined a prognostic signature with potential clinical utility.

CAS (CSE1L) signaling pathway in tumor progression and its potential as a biomarker and target for targeted therapy

CSE1L (chromosome segregation 1-like protein), also named as CAS (cellular apoptosis susceptibility protein), is highly expressed in most cancer types. CSE1L/CAS is a multiple functional protein that plays roles in apoptosis, cell survival, chromosome assembly, nucleocytoplasmic transport, microvesicle formation, and cancer metastasis; some of the functions are explicitly correlated. CSE1L is also a cancer serum biomarker. The phosphorylation of CAS is regulated by the extracellular signal-regulated kinase (ERK). The RAS/RAF/MAPK/ERK signaling pathways are the essential targets of most targeted cancer drugs, thus serum phosphorylated CSE1L may be a potential biomarker for monitoring drug resistance in targeted therapy. CSE1L can regulate Ras-induced ERK phosphorylation. CSE1L also regulates the expression and phosphorylation of CREB (cAMP response element binding protein) and MITF (microphthalmia-associated transcription factor) and is thus involved in the melanogenesis and progression of melanoma. CAS is an exosome/microvesicle membrane protein. Tumor cells consistently secrete microvesicles and tumor-derived microvesicles may be accumulated around tumors. Therefore, microvesicle membrane CSE1L may be a potential target for the development of high-efficacy antibody-drug conjugates (ADCs) for cancer therapy. This review will focus on CSE1L expression in cancers, its relationship to Ras/ERK and cAMP/PKA signaling pathways in melanoma development, its potential for the development of ADCs and tumor imaging reagents, and secretory phosphorylated CSE1L for monitoring the emergence of drug resistance in targeted cancer therapy.

Simultaneous blocking of IL-6 and IL-8 is sufficient to fully inhibit CAF-induced human melanoma cell invasiveness

Tumour microenvironment plays a critical role in cell invasion and metastasis. To investigate the role of cancer-associated fibroblasts (CAFs) in melanoma cell invasiveness, we used 3D spheroid invasion assay. The effect of conditioned media from normal fibroblasts and CAFs cultivated alone or co-cultivated with melanoma cells on BLM or A2058 melanoma spheroid invasion was analysed. We found that conditioned media from CAFs and CAFs co-cultured with melanoma cells, especially, promote invasion and migration, without significant effect on melanoma cell proliferation. We further analysed the expression of pro-invasive cytokines IL-8 and IL-6 in media and found that melanoma cells are dominant producers of IL-8 and fibroblasts are dominant producers of IL-6 in 2D monocultures, while co-cultivation of CAFs with melanoma cells induces production/secretion of IL-6 and IL-8 into the media. The analyses of IL-6 levels in 3D cultures and human melanoma samples, however, revealed that at least in some cases IL-6 is also produced directly by melanoma cells. Analysis of the role of IL-6 and IL-8 in CAF-induced melanoma invasion, using neutralising antibodies, revealed that simultaneous blocking of IL-6 and IL-8 is sufficient to fully inhibit CAF-induced human melanoma cell invasiveness. In summary, these experiments indicate the important role of CAFs and IL-8 and IL-6 cytokines in melanoma cell invasiveness.

Tumor cell vascular mimicry: Novel targeting opportunity in melanoma

In 1999, the American Journal of Pathology published an article, entitled "Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry" by Maniotis and colleagues, which ignited a spirited debate for several years and earned the journal's distinction of a "citation classic" (Maniotis et al., 1999). Tumor cell vasculogenic mimicry (VM), also known as vascular mimicry, describes the plasticity of aggressive cancer cells forming de novo vascular networks and is associated with the malignant phenotype and poor clinical outcome. The tumor cells capable of VM share the commonality of a stem cell-like, transendothelial phenotype, which may be induced by hypoxia. Since its introduction as a novel paradigm for melanoma tumor perfusion, many studies have contributed new findings illuminating the underlying molecular pathways supporting VM in a variety of tumors, including carcinomas, sarcomas, glioblastomas, astrocytomas, and melanomas. Of special significance is the lack of effectiveness of angiogenesis inhibitors on tumor cell VM, suggesting a selective resistance by this phenotype to conventional therapy. Facilitating the functional plasticity of tumor cell VM are key proteins associated with vascular, stem cell, extracellular matrix, and hypoxia-related signaling pathways--each deserving serious consideration as potential therapeutic targets and diagnostic indicators of the aggressive, metastatic phenotype. This review highlights seminal findings pertinent to VM, including the effects of a novel, small molecular compound, CVM-1118, currently under clinical development to target VM, and illuminates important molecular pathways involved in the suppression of this plastic, aggressive phenotype, using melanoma as a model.

AP2α controls the dynamic balance between miR-126&126* and miR-221&222 during melanoma progression

Accumulating evidences have shown the association between aberrantly expressed microRNAs (miRs) and cancer, where these small regulatory RNAs appear to dictate the cell fate by regulating all the main biological processes. We demonstrated the responsibility of the circuitry connecting the oncomiR-221&222 with the tumor suppressors miR-126&126* in melanoma development and progression. According to the inverse correlation between endogenous miR-221&222 and miR-126&126*, respectively increasing or decreasing with malignancy, their enforced expression or silencing was sufficient for a reciprocal regulation. In line with the opposite roles of these miRs, protein analyses confirmed the reverse expression pattern of miR-126&126*-targeted genes that were induced by miR-221&222. Looking for a central player in this complex network, we revealed the dual regulation of AP2α, on one side directly targeted by miR-221&222 and on the other a transcriptional activator of miR-126&126*. We showed the chance of restoring miR-126&126* expression in metastatic melanoma to reduce the amount of mature intracellular heparin-binding EGF like growth factor, thus preventing promyelocytic leukemia zinc finger delocalization and maintaining its repression on miR-221&222 promoter. Thus, the low-residual quantity of these two miRs assures the release of AP2α expression, which in turn binds to and induces miR-126&126* transcription. All together these results point to an unbalanced ratio functional to melanoma malignancy between these two couples of miRs. During progression this balance gradually moves from miR-126&126* toward miR-221&222. This circuitry, besides confirming the central role of AP2α in orchestrating melanoma development and/or progression, further displays the significance of these miRs in cancer and the option of utilizing them for novel therapeutics.

CSE1L Links cAMP/PKA and Ras/ERK pathways and regulates the expressions and phosphorylations of ERK1/2, CREB, and MITF in melanoma cells

The Ras/ERK (extracellular signal-regulated protein kinase) and cAMP/PKA (protein kinase A) pathways are essential for the transcriptional activities of CREB (cAMP response element binding protein) and MITF (microphthalmia-associated transcription factor) in melanogenesis and the progression of melanoma. However, the interaction between Ras/ERK and cAMP/PKA pathways in the melanogenesis and progression of melanoma is not fully known. Here, we report that CSE1L (chromosome segregation 1-like protein) regulates cAMP/PKA-induced CREB and MITF expressions as well as Ras-induced ERK1/2 phosphorylation. IBMX, a cAMP/PKA activator, treatment induced CSE1L phosphorylation and augmented Ras-induced ERK1/2 phosphorylation. CSE1L knockdown by CSE1L shRNA expression vectors inhibited Ras-induced ERK1/2 phosphorylation and melanogenesis in melanoma cells. CSE1L overexpression increased phospho-CREB expression; CSE1L knockdown also inhibited Ras-induced phospho-CREB, MITF, and tyrosinase expressions, regardless of the presence of IBMX. This study identifies CSE1L links and controls the Ras/ERK and cAMP/PKA pathways in the melanogenesis of melanoma cells. Melanomas frequently develop drug resistance via paradoxical activation of Ras/Raf/MEK/ERK or alternatively activated Ras/ERK and cAMP/PKA pathways. Thus CSE1L may be a potential target for treating melanomas that harbor Ras mutations or are resistant to drugs targeting Raf/MEK/ERK. © 2015 Wiley Periodicals, Inc.

Akt Kinase-Interacting Protein 1 Signals through CREB to Drive Diffuse Malignant Mesothelioma

Diffuse malignant mesothelioma (DMM) is a tumor of serosal membranes with propensity for progressive local disease. Because current treatment options are largely ineffective, novel therapeutic strategies based on molecular mechanisms and the disease characteristics are needed to improve the outcomes of patients with this disease. Akt kinase interacting protein 1 (Aki1; Freud-1/CC2D1A) is a scaffold protein for the PI3K-PDK1-Akt signaling module that helps determine receptor signal selectivity for EGFR. Aki1 has been suggested as a therapeutic target, but its potential has yet to be evaluated in a tumor setting. Here, we report evidence supporting its definition as a therapeutic target in DMM. In cell-based assays, Aki1 silencing decreased cell viability and caused cell-cycle arrest of multiple DMM cell lines via effects on the PKA-CREB1 signaling pathway. Blocking CREB activity phenocopied Aki1 silencing. Clinically, Aki1 was expressed in most human DMM specimens where its expression correlated with phosphorylated CREB1. Notably, Aki1 siRNA potently blocked tumor growth in an orthotopic implantation model of DMM when administered directly into the pleural cavity of tumor-bearing mice. Our findings suggest an important role for the Aki1-CREB axis in DMM pathogenesis and provide a preclinical rationale to target Aki1 by intrathoracic therapy in locally advanced tumors.

Role of host β1- and β2-adrenergic receptors in a murine model of B16 melanoma: functional involvement of β3-adrenergic receptors

Complex interactions between tumor cells and their surrounding compartment are strongly influenced by the host in which the tumor grows. In melanoma, for instance, stress-associated norephinephrine (NE), acting at β-adrenergic receptors (β-ARs), stimulates melanoma cell proliferation and tumor angiogenesis. Among β-ARs, β3-ARs play a role acting not only at tumor cells but also at non-neoplastic stromal cells within the melanoma. In the present study, we used a murine model of B16 melanoma to evaluate the role of the host β1- and β2-ARs in melanoma growth and we determined whether the role of β3-ARs can be influenced by the absence of stromal β1- and β2-ARs. As compared to wild-type mice, β1/2-AR knockout mice displayed (i) increased intratumoral levels of both NE and β3-ARs, as evidentiated at both messenger and protein levels; (ii) increased tumor vascularization; (iii) decreased tumor cell proliferation but increased tumor cell apoptosis; and (iv) increased responsiveness to intratumoral injection of the β3-AR blocker L-748,337 in terms of decrease in tumor growth, tumor vascular response, tumor cell proliferation, and increase in tumor cell death. These findings together validate the role of β-AR signaling in melanoma microenvironment suggesting that non-neoplastic stromal cells may be targeted by β-AR-related drugs. The additional fact that β3-ARs play an important role in melanoma growth suggests selective β3-AR antagonists as important proapoptotic agents.

Multiple Molecular Pathways in Melanomagenesis: Characterization of Therapeutic Targets

Molecular mechanisms involved in pathogenesis of malignant melanoma have been widely studied and novel therapeutic treatments developed in recent past years. Molecular targets for therapy have mostly been recognized in the RAS–RAF–MEK–ERK and PI3K–AKT signaling pathways; small-molecule inhibitors were drawn to specifically target key kinases. Unfortunately, these targeted drugs may display intrinsic or acquired resistance and various evidences suggest that inhibition of a single effector of the signal transduction cascades involved in melanoma pathogenesis may be ineffective in blocking the tumor growth. In this sense, a wider comprehension of the multiple molecular alterations accounting for either response or resistance to treatments with targeted inhibitors may be helpful in assessing, which is the most effective combination of such therapies. In the present review, we summarize the known molecular mechanisms underlying either intrinsic and acquired drug resistance either alternative roads to melanoma pathogenesis, which may become targets for innovative anticancer approaches.

Functional cross-talk between the cellular prion protein and the neural cell adhesion molecule is critical for neuronal differentiation of neural stem/precursor cells

Cellular prion protein (PrP) is prominently expressed in brain, in differentiated neurons but also in neural stem/precursor cells (NPCs). The misfolding of PrP is a central event in prion diseases, yet the physiological function of PrP is insufficiently understood. Although PrP has been reported to associate with the neural cell adhesion molecule (NCAM), the consequences of concerted PrP-NCAM action in NPC physiology are unknown. Here, we generated NPCs from the subventricular zone (SVZ) of postnatal day 5 wild-type and PrP null (-/-) mice and observed that PrP is essential for proper NPC proliferation and neuronal differentiation. Moreover, we found that PrP is required for the NPC response to NCAM-induced neuronal differentiation. In the absence of PrP, NCAM not only fails to promote neuronal differentiation but also induces an accumulation of doublecortin-positive neuronal progenitors at the proliferation stage. In agreement, we noted an increase in cycling neuronal progenitors in the SVZ of PrP-/- mice compared with PrP+/+ mice, as evidenced by double labeling for the proliferation marker Ki67 and doublecortin as well as by 5-bromo-2'-deoxyuridine incorporation experiments. Additionally, fewer newly born neurons were detected in the rostral migratory stream of PrP-/- mice. Analysis of the migration of SVZ cells in microexplant cultures from wild-type and PrP-/- mice revealed no differences between genotypes or a role for NCAM in this process. Our data demonstrate that PrP plays a critical role in neuronal differentiation of NPCs and suggest that this function is, at least in part, NCAM-dependent.

CREB-induced inflammation is important for malignant mesothelioma growth

Malignant mesothelioma (MM) is an aggressive tumor with no treatment regimen. Previously we have demonstrated that cyclic AMP response element binding protein (CREB) is constitutively activated in MM tumor cells and tissues and plays an important role in MM pathogenesis. To understand the role of CREB in MM tumor growth, we generated CREB-inhibited MM cell lines and performed in vitro and in vivo experiments. In vitro experiments demonstrated that CREB inhibition results in significant attenuation of proliferation and drug resistance of MM cells. CREB-silenced MM cells were then injected into severe combined immunodeficiency mice, and tumor growth in s.c. and i.p. models of MM was followed. We observed significant inhibition in MM tumor growth in both s.c. and i.p. models and the presence of a chemotherapeutic drug, doxorubicin, further inhibited MM tumor growth in the i.p. model. Peritoneal lavage fluids from CREB-inhibited tumor-bearing mice showed a significantly reduced total cell number, differential cell counts, and pro-inflammatory cytokines and chemokines (IL-6, IL-8, regulated on activation normal T cell expressed and secreted, monocyte chemotactic protein-1, and vascular endothelial growth factor). In vitro studies showed that asbestos-induced inflammasome/inflammation activation in mesothelial cells was CREB dependent, further supporting the role of CREB in inflammation-induced MM pathogenesis. In conclusion, our data demonstrate the involvement of CREB in the regulation of MM pathogenesis by regulation of inflammation.

The expression of platelet-activating factor receptor modulates the cisplatin sensitivity of ovarian cancer cells: a novel target for combination therapy

BACKGROUND

Ovarian cancer has the highest mortality rate of the gynaecological cancers. Although cisplatin (CDDP) is an effective treatment for ovarian cancer, recurrence is frequent and leads to death. The objective was to explore the role and possible mechanisms of platelet-activating factor receptor (PAFR) signalling in CDDP-treated ovarian cancer cells.

METHODS

The upregulation of PAFR in CDDP-treated ovarian cancer cells was observed using realtime PCR and Western blot. The potential role of PAFR in modulating the CDDP sensitivity was assessed using a pharmacological inhibitor and siRNA knockdown. The PAFR-activated signalling pathways involved in cell responses to CDDP were assessed.

RESULTS

Cisplatin induced increased PAFR expression in two ovarian cancer cell lines. The upregulation of PAFR by CDDP correlated with the time-dependent accumulation of NF-κB and HIF-1α in the nucleus. The inhibition of PAFR sensitised the ovarian cancer cells to CDDP. The PI3K and ERK pathways lie downstream of activated PAFR in CDDP-treated cells and their inhibition enhanced CDDP sensitivity. Finally, co-treatment with a PAFR antagonist (Ginkgolide B) and CDDP markedly reduced tumour growth in an in vivo model of ovarian cancer.

CONCLUSIONS

Together, these findings suggest that PAFR is a novel and promising therapeutic target for sensitising ovarian cancer cells to CDDP.

The role of chemoattractant receptors in shaping the tumor microenvironment

Chemoattractant receptors are a family of seven transmembrane G protein coupled receptors (GPCRs) initially found to mediate the chemotaxis and activation of immune cells. During the past decades, the functions of these GPCRs have been discovered to not only regulate leukocyte trafficking and promote immune responses, but also play important roles in homeostasis, development, angiogenesis, and tumor progression. Accumulating evidence indicates that chemoattractant GPCRs and their ligands promote the progression of malignant tumors based on their capacity to orchestrate the infiltration of the tumor microenvironment by immune cells, endothelial cells, fibroblasts, and mesenchymal cells. This facilitates the interaction of tumor cells with host cells, tumor cells with tumor cells, and host cells with host cells to provide a basis for the expansion of established tumors and development of distant metastasis. In addition, many malignant tumors of the nonhematopoietic origin express multiple chemoattractant GPCRs that increase the invasiveness and metastasis of tumor cells. Therefore, GPCRs and their ligands constitute targets for the development of novel antitumor therapeutics.

Redox modulation of FAK controls melanoma survival--role of NOX4

Studies have demonstrated that reactive oxygen species (ROS) generated by NADPH oxidase are essential for melanoma proliferation and survival. However, the mechanisms by which NADPH oxidase regulates these effects are still unclear. In this work, we investigate the role of NADPH oxidase-derived ROS in the signaling events that coordinate melanoma cell survival. Using the highly metastatic human melanoma cell line MV3, we observed that pharmacological NADPH oxidase inhibition reduced melanoma viability and induced dramatic cellular shape changes. These effects were accompanied by actin cytoskeleton rearrangement, diminished FAK^Y397 phosphorylation, and decrease of FAK-actin and FAK-cSrc association, indicating disassembly of focal adhesion processes, a phenomenon that often results in anoikis. Accordingly, NADPH oxidase inhibition also enhanced hypodiploid DNA content, and caspase-3 activation, suggesting activation of the apoptotic machinery. NOX4 is likely to be involved in these effects, since silencing of NOX4 significantly inhibited basal ROS production, reduced FAK^Y397 phosphorylation and decreased tumor cell viability. Altogether, the results suggest that intracellular ROS generated by the NADPH oxidase, most likely NOX4, transmits cell survival signals on melanoma cells through the FAK pathway, maintaining adhesion contacts and cell viability.

CXC and CC chemokines as angiogenic modulators in nonhaematological tumors

Chemokines are a superfamily of structurally homologous heparin-binding proteins that includes potent inducers and inhibitors of angiogenesis. The imbalance between angiogenic and angiostatic chemokine activities can lead to abnormalities, such as chronic inflammation, dysplastic transformation, and even tumor development and spreading. In this review, we summarize the current literature regarding the role of chemokines as modulators of tumor angiogenesis and their potential role as therapeutic targets in patients with nonhaematological tumors.

Synergistic effects of combined platelet-activating factor receptor and epidermal growth factor receptor targeting in ovarian cancer cells

Background

Genetic alterations, including the overexpression of epidermal growth factor receptor (EGFR), play a crucial role in ovarian carcinogenesis. To date, EGFR targeting has shown limited antitumor effects in ovarian cancer when administered as monotherapy. We previously identified platelet-activating factor receptor (PAFR) as being overexpressed in ovarian cancer and found that its ligand PAF evoked EGFR phosphorylation. To determine whether PAFR targeting can enhance the antitumor efficacy of EGFR inhibition, we investigated the effects of a PAFR antagonist (WEB2086) in conjunction with an EGFR inhibitor (AG1478).

Methods

The expression of EGFR and PAFR in CAOV-3 and SKOV-3 ovarian cancer cell lines was measured by Western blot and immunocytochemistry. Synergy was determined using isobologram analysis. The effects of combined PAFR and EGFR targeting on both cells were assessed by using CCK-8, transwell, flow cytometry, western blot analysis. In vivo studies were conducted using CAOV-3 cells xenografted in nu/nu mice.

Results

Treatment with combination WEB2086 and AG1478 resulted in significantly greater inhibition of proliferation and invasion compared to either drug alone. When examining equipotent combinations of WEB2086 and AG1478 to determine potential synergy, a combination index (CI) of 0.49 was identified for CAOV-3 cells and a CI of 0.58 for SKOV-3 cells indicating synergy. This co-inhibition induced significantly more apoptosis and arrested the cells at G0/G1 phase in both cell lines. The activation of PAFR and/or EGFR induced phosphorylation of the mTOR, AKT, and MAPK pathways. Combined PAFR and EGFR targeting synergistically diminished the expression of PAFR and EGFR phosphorylation and downstream signaling. In vivo studies further verified the antitumor effects of combined PAFR and EGFR targeting in a CAOV-3 xenograft model.

Conclusions

These results suggest that WEB2086 and AG1478 are synergistic in ovarian cancer cells with high expression of both PAFR and EGFR. The presented approach may have important therapeutic implications in the treatment of ovarian cancer patients.

Epidermal growth factor induces platelet-activating factor production through receptors transactivation and cytosolic phospholipase A2 in ovarian cancer cells

Background

Among the pro-inflammatory lipid mediators, platelet-activating factor (PAF) is a major primary and secondary messenger that binds to the PAF-receptor (PAFR). Epidermal growth factor (EGF) is a polypeptide growth factor that binds to the EGF-receptor (EGFR). Evidence suggests that both PAF and EGF play a significant role in oncogenic transformation, tumor growth, neoangiogenesis and metastasis, including ovarian cancer. PAF has the potential to transactivate EGFR in ovarian cancer cells. This study explores the mechanisms involved in EGF-induced PAF production.

Methods

The effect of EGF on PAF production in ovarian cancer cells was observed using enzyme-linked immunosorbent assay. The receptors transactivation and the role of cytosolic phospholipase A₂ (cPLA₂) in modulating PAF production induced by EGF was assessed using pharmacological inhibitors, si-RNA knockdown, targeted gene overexpression and immunocytochemistry. The signaling pathways invovled in PAF production induced by EGF in ovarian cancer cells were assessed.

Results

We demonstrate that EGF increases the production of PAF in CAOV3 and SKOV3 ovarian cancer cell lines. EGF induces the transactivation of PAFR, which can be blocked by an EGFR inhibitor. Inhibition of EGFR and/or PAFR blocks PAF production in response to EGF. EGF-induced PAF production involves the phosphorylation of extracellular-regulated protein kinase (ERK) and cytosolic phospholipase A₂ (cPLA₂). A cPLA₂ inhibitor blocks EGF-induced PAF production as well as si-cPLA₂, while overexpression of cPLA₂ increases PAF production.

Conclusions

These results indicate that EGF stimulates PAF production in ovarian cancer cells in a manner that requires cPLA₂. We have also determined that crosstalk can occur bidirectionally between EGFR and PAFR, suggesting that EGF-induced PAF production could result in positive feedback that acts on the PAF-receptor to promote ovarian cancer progression.

Influence of platelet-activating factor, lyso-platelet-activating factor and edelfosine on Langmuir monolayers imitating plasma membranes of cell lines differing in susceptibility to anti-cancer treatment: the effect of plasmalogen level

Three structurally related but differing in biological activities single-chained ether phospholipids (PAF (platelet-activating factor) and lyso-PAF) and an anti-cancer drug (edelfosine (ED)) were investigated in Langmuir monolayers imitating natural membranes. The aim of the undertaken experiments was to study the influence of these lipids on monolayers mimicking plasma membranes of cell lines differing in susceptibility to the anti-cancer activity of ED, i.e. promyelocytic leukaemia cells (HL-60) and promyeloblastic leukaemia cells (K-562). As these cells differ essentially in the cholesterol/phospholipid ratio and plasmalogen concentration in the membrane, we have carried out systematic investigations in artificial systems of various compositions. The results for model leukaemia cell membrane were compared with data acquired for systems imitating normal leucocytes. Our results show that the level of plasmalogens significantly modulates the influence of the single-chained phospholipids on the investigated systems. The experiments confirmed also that the interactions of ether lipids with a model membrane of HL-60 cells (in biological tests sensitive to ED) have opposite character when compared with K-562, being resistant to ED. Moreover, the values of the parameters characterizing monolayers serving as membrane models (strength of interactions, monolayers fluidity and morphology) proved both sensitivity of these cells to ED and lack of their susceptibility towards PAF. Interestingly, it has been found that lyso-PAF, which is usually described as an inactive precursor of PAF, displays a stronger effect on HL-60 model membranes than ED.

Downstream signaling and genome-wide regulatory effects of PTK7 pseudokinase and its proteolytic fragments in cancer cells

Background

The full-length membrane protein tyrosine kinase 7 (PTK7) pseudokinase, an important component of the planar cell polarity and the Wnt canonical and non-canonical pathways, is a subject of step-wise proteolysis in cells and tissues. The proteolysis of PTK7 involves membrane type-matrix metalloproteinase (MT1-MMP), members of the Disintegrin Domain and Metalloproteinase (ADAM) family, and γ-secretase. This multi-step proteolysis results in the generation of the digest fragments of PTK7. These fragments may be either liberated into the extracellular milieu or retained on the plasma membrane or released into the cytoplasm and then transported into the nucleus.

Results

We employed the genome-wide transcriptional and kinome array analyses to determine the role of the full-length membrane PTK7 and its proteolytic fragments in the downstream regulatory mechanisms, with an emphasis on the cell migration-related genes and proteins. Using fibrosarcoma HT1080 cells stably expressing PTK7 and its mutant and truncated species, the structure of which corresponded to the major PTK7 digest fragments, we demonstrated that the full-length membrane 1–1070 PTK7, the N-terminal 1–694 soluble ectodomain fragment, and the C-terminal 622–1070 and 726–1070 fragments differentially regulate multiple genes and signaling pathways in our highly invasive cancer cell model. Immunoblotting of the selected proteins were used to validate the results of our high throughput assays.

Conclusions

Our results suggest that PTK7 levels need to be tightly controlled to enable migration and that the anti-migratory effect of the full-length membrane PTK7 is linked to the down-regulation of multiple migration-related genes and to the activation of the Akt and c-Jun pathway. In turn, the C-terminal fragments of PTK7 act predominantly via the RAS-ERK and CREB/ATF1 pathway and through the up-regulation of cadherin-11. In general, our data correlate well with the distinct functionality of the full-length receptor tyrosine kinases and their respective intracellular domain (ICD) proteolytic fragments.

Heparan sulfate proteoglycans and heparin regulate melanoma cell functions

BACKGROUND

The solid melanoma tumor consists of transformed melanoma cells, and the associated stromal cells including fibroblasts, endothelial cells, immune cells, as well as, soluble macro- and micro-molecules of the extracellular matrix (ECM) forming the complex network of the tumor microenvironment. Heparan sulfate proteoglycans (HSPGs) are an important component of the melanoma tumor ECM. Importantly, there appears to be both a quantitative and a qualitative shift in the content of HSPGs, in parallel to the nevi-radial growth phase-vertical growth phase melanoma progression. Moreover, these changes in HSPG expression are correlated to modulations of key melanoma cell functions.

SCOPE OF REVIEW

This review will critically discuss the roles of HSPGs/heparin in melanoma development and progression.

MAJOR CONCLUSIONS

We have correlated HSPGs' expression and distribution with melanoma cell signaling and functions as well as angiogenesis.

GENERAL SIGNIFICANCE

The current knowledge of HSPGs/heparin biology in melanoma provides a foundation we can utilize in the ongoing search for new approaches in designing anti-tumor therapy. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Why is melanoma so metastatic?

Malignant melanoma is one of the most aggressive cancers and can disseminate from a relatively small primary tumor and metastasize to multiple sites, including the lung, liver, brain, bone, and lymph nodes. Elucidating the molecular and genetic changes that take place during the metastatic process has led to a better understanding of why melanoma is so metastatic. Herein, we describe the unique features that distinguish melanoma from other solid tumors and contribute to the malignant phenotype of melanoma cells. For example, although melanoma cells are highly antigenic, they are extremely efficient at evading host immune response. Melanoma cells share numerous cell surface molecules with vascular cells, are highly angiogenic, are mesenchymal in nature, and possess a higher degree of 'stemness' than do other solid tumors. Finally, analysis of melanoma mutations has revealed that the gene expression profile of malignant melanoma is different from that of other cancers. Elucidating these molecular and genetic processes in highly metastatic melanoma can lead to the development of improved treatment and individualized therapy options.

Molecular and cellular pathogenesis of melanoma initiation and progression

Melanoma is a malignant tumor of melanocytes that can spread to other organs of the body, resulting in severe and/or lethal malignancies. Melanocytes are pigment-producing cells found in the deep layer of the epidermis and are originated from melanocytes stem cells through a cellular process called melanogenesis. Several genes and epigenetic and micro-environmental factors are involved in this process via the regulation and maintenance of the balance between melanocytes stem cells proliferation and their differentiation into melanocytes. Dysregulation of this balance through gain or loss of function of key genes implicated in the control and regulation of cell cycle progression and/or differentiation results in melanoma initiation and progression. This review aims to provide a comprehensive overview about the origin of melanocytes, the oncogenic events involved in melanocytes stem cells transformation, and the mechanisms implicated in the perpetuation of melanoma malignant phenotype.

Molecular networks in melanoma invasion and metastasis

Metastatic melanoma accounts for approximately 80% of skin cancer-related deaths. Up to now there has been no effective treatment for stage IV melanoma patients due to the complexity and dissemination potential of this disease. Melanomas are heterogeneous tumors in which conventional therapies fail to improve overall survival. Targeted therapies are being developed, but the final outcome can be hampered by the incomplete knowledge of the process of melanoma progression. Even if the intracellular pathways are similar, the interaction of the cells with the surrounding environment should be taken into consideration. This article seeks to highlight some of the advances in the understanding of the molecular mechanisms underlying melanoma dissemination.