In the Wnt-er of life: Wnt signalling in melanoma and ageing

Rab7a is an enhancer of TPC2 activity regulating melanoma progression through modulation of the GSK3β/β-Catenin/MITF-axis

Melanoma arising from pigment-producing melanocytes is the deadliest form of skin cancer. Extensive ultraviolet light exposure is a major cause of melanoma and individuals with low levels of melanin are at particular risk. Humans carrying gain-of-function polymorphisms in the melanosomal/endolysosomal two-pore cation channel TPC2 present with hypopigmentation, blond hair, and albinism. Loss of TPC2 is associated with decreased cancer/melanoma proliferation, migration, invasion, tumor growth and metastasis formation, and TPC2 depleted melanoma cells show increased levels of melanin. How TPC2 activity is controlled in melanoma and the downstream molecular effects of TPC2 activation on melanoma development remain largely elusive. Here we show that the small GTPase Rab7a strongly enhances the activity of TPC2 and that effects of TPC2 on melanoma hallmarks, in vitro and in vivo strongly depend on the presence of Rab7a, which controls TPC2 activity to modulate GSK3β, β-Catenin, and MITF, a major regulator of melanoma development and progression.

Entering the TiME machine: How age-related changes in the tumor immune microenvironment impact melanoma progression and therapy response

Melanoma is the deadliest form of skin cancer in the United States, with its incidence rates rising in older populations. As the immune system undergoes age-related changes, these alterations can significantly influence tumor progression and the effectiveness of cancer treatments. Recent advancements in understanding immune checkpoint molecules have paved the way for the development of innovative immunotherapies targeting solid tumors. However, the aging tumor microenvironment can play a crucial role in modulating the response to these immunotherapeutic approaches. This review seeks to examine the intricate relationship between age-related changes in the immune system and their impact on the efficacy of immunotherapies, particularly in the context of melanoma. By exploring this complex interplay, we hope to elucidate potential strategies to optimize treatment outcomes for older patients with melanoma, and draw parallels to other cancers.

Upregulation and functional roles of miR-450b in canine oral melanoma

Canine oral melanoma (COM) is a common and highly aggressive disease with the potential to model human melanomas. Dysregulated microRNAs represent an interesting line of research for COM because they are implicated in tumor progression. One example is miR-450b, which has been investigated for its molecular mechanisms and biological functions in multiple human cancers, but not human or canine melanoma. Here, we aimed to investigate miR-450b as a potential diagnostic biomarker of COM and its functional roles in metastatic and non-metastatic forms of the disease. We investigated the expression of miR-450b and its target mRNA genes in clinical (tumor tissue and plasma) samples and metastatic and primary-tumor cell lines. Knockdown and overexpression experiments were performed to determine the influence of miR-450b on cell proliferation, migration, colony formation, and apoptosis. miR-450b was significantly upregulated in COM and differentiated between metastatic and non-metastatic tumors, and its potential as a biomarker of metastatic and non-metastatic COM was further confirmed in ROC analysis. miR-450b knockdown promoted cell proliferation, migration, and clonogenicity and inhibited apoptosis, whereas its overexpression yielded the reverse pattern. miR-450b directly binds 3' UTR of PAX9 mRNA and modulates its function leading to BMP4 downregulation and MMP9 upregulation at the transcript level. Furthermore, we surmised that miR-450b activates the Wnt signaling pathway based on gene ontology and enrichment analyses. We concluded that miR-450b has the potential as a diagnostic biomarker and could be a target candidate for COM treatment.

Pathogenesis of Warthin's Tumor: Neoplastic or Non-Neoplastic?

Warthin's tumor is the second most frequent neoplasm next to pleomorphic adenoma in the salivary gland, mostly in the parotid gland. The epithelial cells constituting a tumor are characterized by the presence of mitochondria that undergo structural and functional changes, resulting in the development of oncocytes. In addition to containing epithelial cells, Warthin's tumors contain abundant lymphocytes with lymph follicles (germinal centers) that are surrounded by epithelial cells. The pathogenesis of Warthin's tumor is not fully understood, and several hypotheses have been proposed. The risk factors for the development of Warthin's tumor, which predominantly occurs in males, include aging, smoking, and radiation exposure. Recently, it has been reported that chronic inflammation and aging cells promote the growth of Warthin's tumor. Several reports regarding the origin of the tumor have suggested that (1) Warthin's tumor is an IgG4-related disease, (2) epithelial cells that compose Warthin's tumor accumulate mitochondria, and (3) Warthin's tumor is a metaplastic lesion in the lymph nodes. It is possible that the pathogenesis of Warthin's tumor includes mitochondrial metabolic abnormalities, accumulation of aged cells, chronic inflammation, and senescence-associated secretory phenotype (SASP). In this short review, we propose that DNA damage, metabolic dysfunction of mitochondria, senescent cells, SASP, human papillomavirus, and IgG4 may be involved in the development of Warthin's tumor.

RIPK4 downregulation impairs Wnt3A-stimulated invasiveness via Wnt/β-catenin signaling in melanoma cells and tumor growth in vivo

PURPOSE

The role of Wnt signaling in oncogenesis and drug resistance is well known. Receptor-interacting protein kinase (RIPK4) contributing to the increased activity of many signaling pathways, including Wnt/β-catenin, may be an important target for designing new drugs for metastatic melanoma, but its role in melanoma is not fully understood.

METHODS

We tested the effect of genetic manipulation of RIPK4 (CRISPR/Cas9) on xenograft growth. In addition, immunohistochemistry was used to detect active β-catenin, Ki67 and necrosis in xenografts. Wnt signaling pathway activity was examined using Western blot and Top-Flash. The effect of RIPK4 knockout on melanoma cells in vitro stimulated Wnt3A on wound overgrowth, migration and invasion ability was then evaluated.

RESULTS

Our study showed that CRISPR/Cas9-mediated RIPK4 knockout (KO) significantly reduced tumor growth in a mouse model of melanoma, particularly of WM266.4 cells. RIPK4 KO tumors exhibited lower percentages of Ki67+ cells as well as reduced necrotic area and decreased levels of active β-catenin. In addition, we observed that RIPK4 knockout impaired Wnt3A-induced activation of LRP6 and β-catenin, as manifested by a decrease in the transcriptional activity of β-catenin in Top-Flash in both tested melanoma cell lines, A375 and WM266.4. Prolonged incubation (48 h) with Wnt3A showed reduced level of MMP9, C-myc, and increased SOX10, proteins whose transcription is also dependent on β-catenin activity. Moreover, RIPK4 knockout led to the inhibition of scratch overgrowth, migration and invasion of these cells compared to their controls.

CONCLUSION

RIPK4 knockdown inhibits melanoma tumor growth and Wnt3A stimulated migration and invasion indicating that RIPK4 might be a potential target for melanoma therapy.

Matricellular Proteins in the Homeostasis, Regeneration, and Aging of Skin

Matricellular proteins are secreted extracellular proteins that bear no primary structural functions but play crucial roles in tissue remodeling during development, homeostasis, and aging. Despite their low expression after birth, matricellular proteins within skin compartments support the structural function of many extracellular matrix proteins, such as collagens. In this review, we summarize the function of matricellular proteins in skin stem cell niches that influence stem cells' fate and self-renewal ability. In the epidermal stem cell niche, fibulin 7 promotes epidermal stem cells' heterogeneity and fitness into old age, and the transforming growth factor-β-induced protein ig-h3 (TGFBI)-enhances epidermal stem cell growth and wound healing. In the hair follicle stem cell niche, matricellular proteins such as periostin, tenascin C, SPARC, fibulin 1, CCN2, and R-Spondin 2 and 3 modulate stem cell activity during the hair cycle and may stabilize arrector pili muscle attachment to the hair follicle during piloerections (goosebumps). In skin wound healing, matricellular proteins are upregulated, and their functions have been examined in various gain-and-loss-of-function studies. However, much remains unknown concerning whether these proteins modulate skin stem cell behavior, plasticity, or cell-cell communications during wound healing and aging, leaving a new avenue for future studies.

RYK Gene Expression Associated with Drug Response Variation of Temozolomide and Clinical Outcomes in Glioma Patients

Temozolomide (TMZ) chemotherapy is an important tool in the treatment of glioma brain tumors. However, variable patient response and chemo-resistance remain exceptionally challenging. Our previous genome-wide association study (GWAS) identified a suggestively significant association of SNP rs4470517 in the RYK (receptor-like kinase) gene with TMZ drug response. Functional validation of RYK using lymphocytes and glioma cell lines resulted in gene expression analysis indicating differences in expression status between genotypes of the cell lines and TMZ dose response. We conducted univariate and multivariate Cox regression analyses using publicly available TCGA and GEO datasets to investigate the impact of RYK gene expression status on glioma patient overall (OS) and progression-free survival (PFS). Our results indicated that in IDH mutant gliomas, RYK expression and tumor grade were significant predictors of survival. In IDH wildtype glioblastomas (GBM), MGMT status was the only significant predictor. Despite this result, we revealed a potential benefit of RYK expression in IDH wildtype GBM patients. We found that a combination of RYK expression and MGMT status could serve as an additional biomarker for improved survival. Overall, our findings suggest that RYK expression may serve as an important prognostic or predictor of TMZ response and survival for glioma patients.

Localized immune surveillance of primary melanoma in the skin deciphered through executable modeling

While skin is a site of active immune surveillance, primary melanomas often escape detection. Here, we have developed an in silico model to determine the local cross-talk between melanomas and Langerhans cells (LCs), the primary antigen-presenting cells at the site of melanoma development. The model predicts that melanomas fail to activate LC migration to lymph nodes until tumors reach a critical size, which is determined by a positive TNF-α feedback loop within melanomas, in line with our observations of murine tumors. In silico drug screening, supported by subsequent experimental testing, shows that treatment of primary tumors with MAPK pathway inhibitors may further prevent LC migration. In addition, our in silico model predicts treatment combinations that bypass LC dysfunction. In conclusion, our combined approach of in silico and in vivo studies suggests a molecular mechanism that explains how early melanomas develop under the radar of immune surveillance by LC.

Association between hypertension and cutaneous melanoma, and the effect of aspirin: extended follow-up of a large randomised controlled trial

BACKGROUND

The association between hypertension and melanoma is unclear, and previous analyses of data from the ASPirin in Reducing Events in the Elderly (ASPREE) study demonstrated a reduced number of invasive melanoma events amongst aspirin-exposed hypertensive individuals.

METHODS

Data from the ASPREE study which included (1) the intervention period with a median follow-up of 4.7 years, and (2) the observational period with an additional 2 years follow-up, were combined for this analysis. Logistic regression analyses examined the association between baseline hypertension and treatment status and past melanoma history. Survival analyses examined the association between hypertension and melanoma risk, and the effect of aspirin across hypertension groups. Cox proportional hazards models were used to compare incidence across groups.

RESULTS

19,114 participants (median age of 74 years) were randomised to daily 100 mg aspirin or placebo. At baseline, hypertension and past melanoma history were recorded in 14,195 and 685 individuals, respectively. After adjustment for confounders, hypertension was significantly associated with past melanoma history (OR=1.34, 95%CI: 1.11-1.62). In a prospective analysis, baseline hypertension was not associated with melanoma risk. However, aspirin was associated with a reduced risk of incident melanoma amongst individuals with uncontrolled hypertension (blood pressure ≥140/90 mmHg; HR=0.63, 95%CI 0.44-0.89), but not in those with controlled hypertension (HR=1.04, 95%CI 0.74-1.46).

CONCLUSION

Our results support a reduced melanoma incidence amongst individuals with uncontrolled hypertension exposed to aspirin. Additional studies are required to confirm these findings.

Effect of Aspirin on Melanoma Incidence in Older Persons: Extended Follow-up of a Large Randomized Double-blind Placebo-controlled Trial

The effects of aspirin on melanoma are unclear, with studies reporting conflicting results. Data from two periods of the ASPirin in Reducing Events in the Elderly (ASPREE) study; the randomized placebo-controlled trial period examining daily 100 mg aspirin in older adults with a median follow-up of 4.7 years, and the second period, an additional 2 years of observational follow-up, were utilized in this secondary analysis to examine whether aspirin exposure is associated with a reduced cutaneous melanoma incidence. All melanoma cases were adjudicated and Cox proportional hazards models were used to compare incidence between randomized treatment groups. ASPREE recruited 19,114 participants with a median age of 74 years. During the trial period, 170 individuals (76 aspirin, 94 placebo) developed an invasive melanoma, and no significant effect of aspirin was observed on incident melanoma [HR = 0.81; 95% confidence interval (CI), 0.60-1.10]. Including the additional 2 years of observational follow-up (median follow-up of 6.3 years), 268 individuals (119 aspirin, 149 placebo) developed an invasive melanoma, and similar results were observed (HR = 0.81; 95% CI, 0.63-1.03). A reduced number of events was observed with aspirin among females in a subgroup analysis (HR = 0.65; 95% CI, 0.44-0.92); however, the interaction effect with males (HR = 0.92; 95% CI, 0.68-1.25) was nonsignificant (P = 0.17). Our findings from this randomized trial do not provide strong support that aspirin is associated with a reduced risk of invasive melanoma in older individuals. Additional studies are required to further explore this relationship.

PREVENTION RELEVANCE

Melanoma prevention is an important strategy to improve outcomes and while preventive efforts have largely focused on sun protection, the role of potential chemopreventive agents such as aspirin warrants investigation.

Novel GSK-3 kinase inhibitor Pym-5 induces GSK-3β rather than GSK-3α-dependent melanogenesis in murine melanoma cells

BACKGROUND

Glycogen synthase kinase-3 (GSK-3) inhibitors are considered to activate Wnt/β-Catenin, which remains a controversial topic in melanoma treatment.

OBJECTIVE

Here, we have developed Pym-5, an attractive GSK-3 inhibitor. Using Pym-5 as a chemical tool to probe the GSK-3 biology, we aimed to investigate the potential of GSK-3 inhibition as a strategy of melanoma treatment and underlying mechanisms.

METHODS

Using pigment B16 and B16BL6 murine melanoma model in vitro and a zebrafish pigmentation model in vivo, we investigated Pym-5-meditaed activation of Wnt/β-Catenin, melanogenesis and antitumor response in melanoma treatment.

RESULTS

We found that Pym-5 delayed the growth and promoted melanogenesis of melanoma cells. Pym-5 activated the transcription of β-Catenin and responsive targets genes (AXIN2 and MITF), melanin biosynthesis genes (TYR, TYRP1 and TYRP2) and eventually elevated the production of melanin. Interestingly, genetic inactivation of GSK-3β, but not its paralogue GSK-3α, compromised Pym-5-mediated melanogenesis in B16 and B16BL6 cells.

CONCLUSION

These data provide insight into the potential therapeutic benefits obtained from activation of Wnt/β-Catenin signaling pathway and how Pym-5 can regulate melanin production and the rationale for future clinical application of GSK-3 inhibitor in melanoma patients.

Stromal changes in the aged lung induce an emergence from melanoma dormancy

Disseminated cancer cells from primary tumours can seed in distal tissues, but may take several years to form overt metastases, a phenomenon that is termed tumour dormancy. Despite its importance in metastasis and residual disease, few studies have been able to successfully characterize dormancy within melanoma. Here we show that the aged lung microenvironment facilitates a permissive niche for efficient outgrowth of dormant disseminated cancer cells-in contrast to the aged skin, in which age-related changes suppress melanoma growth but drive dissemination. These microenvironmental complexities can be explained by the phenotype switching model, which argues that melanoma cells switch between a proliferative cell state and a slower-cycling, invasive state1-3. It was previously shown that dermal fibroblasts promote phenotype switching in melanoma during ageing4-8. We now identify WNT5A as an activator of dormancy in melanoma disseminated cancer cells within the lung, which initially enables the efficient dissemination and seeding of melanoma cells in metastatic niches. Age-induced reprogramming of lung fibroblasts increases their secretion of the soluble WNT antagonist sFRP1, which inhibits WNT5A in melanoma cells and thereby enables efficient metastatic outgrowth. We also identify the tyrosine kinase receptors AXL and MER as promoting a dormancy-to-reactivation axis within melanoma cells. Overall, we find that age-induced changes in distal metastatic microenvironments promote the efficient reactivation of dormant melanoma cells in the lung.

β-Catenin Signaling Evokes Hair Follicle Senescence by Accelerating the Differentiation of Hair Follicle Mesenchymal Progenitors

Rationale: β-catenin signaling controls multiple fibroblast subsets, with its overactivity promoting the differentiation of hair follicle dermal stem cells (hfDSCs) and the hyperactivation of interfollicular fibroblasts. Understanding the concept of hfDSC activation and modulation offers hope towards the therapeutic armamentarium in dermatology and related comorbidities, as well as their potential applications in gerontology (the study of physiological aging). Having a comprehensive understanding in this stochastic process could also further yield important, novel insights into the molecular basis of skin aging to improve lifespan and preventing aging-related diseases.

Methods: A new CD34CrePGR mouse line was generated. Through fate-tracing models and a series of β-catenin genetic experiments, our study depicts how the wound environment increases phosphorylated β-catenin in hfDSCs and facilitates their differentiation into dermal papilla (DP) and dermal sheath (DS). In mice carrying hfDSC-specific activated allele of β-catenin, hfDSCs accelerated their differentiation into DP cells.

Results: Notably, with β-catenin stabilization in CD34-expressing cells and potential activation of canonical Wnt signaling, the mutant mice showed a brief increase of hair density in the short term, but over time leads to a senescence phenotype developing premature canities and thinning [hair follicle (HF) miniaturization].

Conclusion: β-catenin signaling drove HF senescence by accelerating differentiation of CD34⁺ hfDSCs, resulting in phenotypes attributable to the differentiation of the hfDSCs into DP cells and the loss of their stem cell potential. Therefore, our study reveals that the regulation of β-catenin signaling in hfDSCs may potentially become an important subject for future exploration in development of clinically effective therapies for hair loss treatment and an excellent model for revealing new therapeutic approaches to reverse aging or retarding the development of alopecia.

Stepwise-edited, human melanoma models reveal mutations' effect on tumor and microenvironment

Establishing causal relationships between genetic alterations of human cancers and specific phenotypes of malignancy remains a challenge. We sequentially introduced mutations into healthy human melanocytes in up to five genes spanning six commonly disrupted melanoma pathways, forming nine genetically distinct cellular models of melanoma. We connected mutant melanocyte genotypes to malignant cell expression programs in vitro and in vivo, replicative immortality, malignancy, rapid tumor growth, pigmentation, metastasis, and histopathology. Mutations in malignant cells also affected tumor microenvironment composition and cell states. Our melanoma models shared genotype-associated expression programs with patient melanomas, and a deep learning model showed that these models partially recapitulated genotype-associated histopathological features as well. Thus, a progressive series of genome-edited human cancer models can causally connect genotypes carrying multiple mutations to phenotype.

Characterization of aging tumor microenvironment with drawing implications in predicting the prognosis and immunotherapy response in low-grade gliomas

Aging tumor microenvironment (aging TME) is emerging as a hot spot in cancer research for its significant roles in regulation of tumor progression and tumor immune response. The immune and stromal scores of low-grade gliomas (LGGs) from TCGA and CGGA databases were determined by using ESTIMATE algorithm. Differentially expressed genes (DEGs) between high and low immune/stromal score groups were identified. Subsequently, weighted gene co-expression network analysis (WGCNA) was conducted to screen out aging TME related signature (ATMERS). Based on the expression patterns of ATMERS, LGGs were classified into two clusters with distinct prognosis via consensus clustering method. Afterwards, the aging TME score for each sample was calculated via gene set variation analysis (GSVA). Furthermore, TME components were quantified by MCP counter and CIBERSORT algorithm. The potential response to immunotherapy was evaluated by Tumor Immune Dysfunction and Exclusion analysis. We found that LGG patients with high aging TME scores showed poor prognosis, exhibited an immunosuppressive phenotype and were less likely to respond to immunotherapy compared to those with low scores. The predictive performance of aging TME score was verified in three external datasets. Finally, the expression of ATMERS in LGGs was confirmed at protein level through the Human Protein Atlas website and western blot analysis. This novel aging TME-based scoring system provided a robust biomarker for predicting the prognosis and immunotherapy response in LGGs.

NEAT1 in bone marrow mesenchymal stem cell-derived extracellular vesicles promotes melanoma by inducing M2 macrophage polarization

Bone marrow mesenchymal stem cells (BMSCs)-derived extracellular vesicles (EVs) reportedly play an important role in melanoma pathogenesis. This study aimed to explore the mechanisms of EVs-carried long non-coding RNA (lncRNA) NEAT1 involvement in melanoma. Gain- and loss-of-function experiments were performed to determine biological characteristics of A-375 melanoma cells. Bioinfomatic prediction, RNA immunoprecipitation (RIP), and dual luciferase reporter gene experiments were applied to investigate the roles of NEAT1 and microRNA-374a-5p (miR-374a-5p), and leucine-rich repeat-containing G protein-coupled receptor 4 (LGR4). A subcutaneous tumor model was constructed using nude mice, and in vivo fluorescence imaging was used to observe the effect of NEAT1 on the growth and metastasis of melanoma cells in vivo. The results indicated that BMSC-EVs could be internalized by macrophages to promote the expression of macrophages M2 markers. M2 type macrophages promoted malignancy of melanoma cells. NEAT1 derived from BMSC-EVs promoted the progression of melanoma by promoting M2 polarization of macrophages. NEAT1 inhibits miR-374 expression, while miR-374 could upregulate LGR4-dependent IQGAP1 expression. The tumor-inhibiting effect of NEAT1 silencing was validated in the nude mouse xenograft model. Collectively, the results demonstrated that BMSC-EVs carrying NEAT1 can promote the progression of melanoma by inducing M2 polarization of macrophages, and thus may be considered as a potential target for melanoma therapeutics.

Aloe-emodin inhibits the proliferation, migration, and invasion of melanoma cells via inactivation of the Wnt/beta-catenin signaling pathway

BACKGROUND

Aloe-emodin is reported as a potential cancer therapeutic agent due to its inhibition of the proliferation, migration, and invasion of cancer cells. This study aimed to confirm the effects of aloe-emodin on the progression of melanoma and identify the underlying molecular mechanisms.

METHODS

The effects of aloe-emodin treatment (concentrations ranging from 0 to 25 µg, 48 h) on proliferation, apoptosis, distribution of cell cycle, migration, and invasion were detected by performing Cell Counting Kit-8 (CCK-8) assay, colony formation assay, flow cytometry, wound healing assay, and Transwell invasion experiments. Rescue experiments were carried out by overexpression of β-catenin to verify the role of β-catenin in the inhibition of melanoma by aloe-emodin. The analysis was carried out at the animal level by constructing tumor-bearing nude mice model.

RESULTS

The results showed that aloe-emodin prominently reduced the proliferation, migration, and invasion of melanoma cells. Additionally, it was found that aloe-emodin significantly enhanced the cell apoptosis and induced G2 phase arrest of melanoma cells via enhancing the expressions of cleaved-caspase3, bax, and reducing cyclinD1, c-myc, and bcl-2. In addition, aloe-emodin could also inhibit Wnt3a levels, and promote GSK3-beta and beta-catenin phosphorylation. In vivo experiments also showed that overexpression of beta-catenin reversed the effects of aloe-emodin on tumor growth.

CONCLUSIONS

In conclusion, our findings indicated that aloe-emodin might prominently inhibit the tumor growth and metastasis of melanoma via the Wnt/beta-catenin signaling pathway in vitro. Therefore, aloe-emodin may serve as a potential drug for the clinical treatment of melanoma.

Modulating skin colour: role of the thioredoxin and glutathione systems in regulating melanogenesis

Different skin colour among individuals is determined by the varying amount and types of melanin pigment. Melanin is produced in melanocytes, a type of dendritic cell located in the basal layer of the epidermis, through the process of melanogenesis. Melanogenesis consists of a series of biochemical and enzymatic reactions catalysed by tyrosinase and other tyrosinase-related proteins, leading to the formation of two types of melanin, eumelanin and pheomelanin. Melanogenesis can be regulated intrinsically by several signalling pathways, including the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA), stem cell factor (SCF)/c-kit and wingless-related integration site (Wnt)/β-catenin signalling pathways. Ultraviolet radiation (UVR) is the major extrinsic factor in the regulation of melanogenesis, through the generation of reactive oxygen species (ROS). Antioxidants or antioxidant systems, with the ability to scavenge ROS, may decrease melanogenesis. This review focuses on the two main cellular antioxidant systems, the thioredoxin (Trx) and glutathione (GSH) systems, and discusses their roles in melanogenesis. In the Trx system, high levels/activities of thioredoxin reductase (TrxR) are correlated with melanin formation. The GSH system is linked with regulating pheomelanin formation. Exogenous addition of GSH has been shown to act as a depigmenting agent, suggesting that other antioxidants may also have the potential to act as depigmenting agents for the treatment of human hyperpigmentation disorders.

Pannexin 1 binds β-catenin to modulate melanoma cell growth and metabolism

Melanoma is the most aggressive skin malignancy with increasing incidence worldwide. Pannexin1 (PANX1), a member of the pannexin family of channel-forming glycoproteins, regulates cellular processes in melanoma cells including proliferation, migration, and invasion/metastasis. However, the mechanisms responsible for coordinating and regulating PANX1 function remain unclear. Here, we demonstrated a direct interaction between the C-terminal region of PANX1 and the N-terminal portion of β-catenin, a key transcription factor in the Wnt pathway. At the protein level, β-catenin was significantly decreased when PANX1 was either knocked down or inhibited by two PANX1 blockers, Probenecid and Spironolactone. Immunofluorescence imaging showed a disrupted pattern of β-catenin localization at the cell membrane in PANX1-deficient cells, and transcription of several Wnt target genes, including MITF, was suppressed. In addition, a mitochondrial stress test revealed that the metabolism of PANX1-deficient cells was impaired, indicating a role for PANX1 in the regulation of the melanoma cell metabolic profile. Taken together, our data show that PANX1 directly interacts with β-catenin to modulate growth and metabolism in melanoma cells. These findings provide mechanistic insight into PANX1-mediated melanoma progression and may be applicable to other contexts where PANX1 and β-catenin interact as a potential new component of the Wnt signaling pathway.

Age-related transcriptome changes in melanoma patients with tumor-positive sentinel lymph nodes

Age is an important factor for determining the outcome of melanoma patients. Sentinel lymph node (SLN) status is also a strong predictor of survival for melanoma. Paradoxically, older melanoma patients have a lower incidence of SLN metastasis but a higher mortality rate when compared with their younger counterparts. The mechanisms that underlie this phenomenon remain unknown. This study uses three independent datasets of RNA samples from patients with melanoma metastatic to the SLN to identify age-related transcriptome changes in SLNs and their association with outcome. Microarray was applied to the first dataset of 97 melanoma patients. NanoString was performed in the second dataset to identify the specific immune genes and pathways that are associated with recurrence in younger versus older patients. qRT-PCR analysis was used in the third dataset of 36 samples to validate the differentially expressed genes (DEGs) from microarray and NanoString. These analyses show that FOS, NR4A, and ITGB1 genes were significantly higher in older melanoma patients with positive SLNs. IRAK3- and Wnt10b-related genes are the major pathways associated with recurrent melanoma in younger and older patients with tumor-positive SLNs, respectively. This study aims to elucidate age-related differences in SLNs in the presence of nodal metastasis.

Cyclin F Downregulation Affects Epithelial-Mesenchymal Transition Increasing Proliferation and Migration of the A-375 Melanoma Cell Line

Background

Cyclins are well-known cell cycle regulators. The activation of cyclin-dependent kinases by cyclins allows orchestration of the complicated cell cycle machinery and drives the cell from the G1 phase to the end of the mitotic phase. In recent years, it has become evident that cyclins are involved in processes beyond the cell cycle. Cyclin F does not activate CDKs but forms part of the Skp1-Cul1-F-box (SCF) complex where it is responsible for protein target recognition and subsequent degradation in a proteasome-dependent manner.

Results

Here, we report that the downregulation of cyclin F in the A-375 melanoma cell line increases cell viability and colony formation in a cell cycle independent manner. Lower levels of cyclin F do not appear to affect the cell cycle, based on flow cytometry measuring BrdU incorporation and propidium iodide staining. By means of immunofluorescence staining and Western blot analysis, we observed changes in cell morphology-related markers which suggested ongoing epithelial-mesenchymal transition (EMT) in response to cyclin F downregulation. Increases in vimentin and N-cadherin protein levels, decreases in levels of epithelial markers such as ZO-1, along with changes in morphology to a spindle-like shape with the appearance of actin stress fibers, are all hallmarks of EMT. These changes are associated with increased invasive and migratory potential, based on 2D migration assays. Moreover, we observe an increase in RhoABC, talin and paxillin levels, the proteins involved in controlling cell signaling and motility. Lastly, upon knocking down cyclin F expression, we observed a decrease in thrombospondin-1 expression, suggesting a role of cyclin F in angiogenesis.

Conclusion

Cyclin F depletion induces proliferation and EMT processes in the A-375 melanoma model.

Making a melanoma: Molecular and cellular changes underlying melanoma initiation

Melanoma arises from the melanocyte lineage and is the most aggressive and lethal form of skin cancer. There are several genetic, genomic, and cellular changes associated with melanoma initiation. Here, we discuss these alterations and the melanoma cells of origin in which they are proposed to promote melanomagenesis.

Pharmacological targeting and the diverse functions of the metastasis suppressor, NDRG1, in cancer

N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that is regulated by hypoxia, metal ions including iron, the free radical nitric oxide (NO^.), and various stress stimuli. This intriguing molecule exhibits diverse functions in cancer, inhibiting epithelial-mesenchymal transition (EMT), cell migration and angiogenesis by modulation of a plethora of oncogenes via cellular signaling. Thus, pharmacological targeting of NDRG1 signaling in cancer is a promising therapeutic strategy. Of note, novel anti-tumor agents of the di-2-pyridylketone thiosemicarbazone series, which exert the "double punch" mechanism by binding metal ions to form redox-active complexes, have been demonstrated to markedly up-regulate NDRG1 expression in cancer cells. This review describes the mechanisms underlying NDRG1 modulation by the thiosemicarbazones and the diverse effects NDRG1 exerts in cancer. As a major induction mechanism, iron depletion appears critical, with NO^. also inducing NDRG1 through its ability to bind iron and generate dinitrosyl-dithiol iron complexes, which are then effluxed from cells. Apart from its potent anti-metastatic role, several studies have reported a pro-oncogenic role of NDRG1 in a number of cancer-types. Hence, it has been suggested that NDRG1 plays pleiotropic roles depending on the cancer-type. The molecular mechanism(s) underlying NDRG1 pleiotropy remain elusive, but are linked to differential regulation of WNT signaling and potentially differential interaction with the tumor suppressor, PTEN. This review discusses NDRG1 induction mechanisms by metal ions and NO^. and both the anti- and possible pro-oncogenic functions of NDRG1 in multiple cancer-types and compares the opposite effects this protein exerts on cancer progression.

Normal Aging and Its Role in Cancer Metastasis

Metastasis is the most common cause of death, with treatments failing to provide a durable response. Aging is a key prognostic factor in many cancers. Emerging data suggest that normal age-related changes in the tumor microenvironment can contribute to metastatic progression. These changes encompass secreted factors, biophysical changes, and changes in both stromal and immune cell populations. These data also highlight the importance of conducting studies in preclinical models of appropriate age. Ultimately, therapies may also need to be tailored to reflect patient age, as markers of metastatic disease differ in young and aged populations. In this review, we will discuss some of the changes that occur during aging that increase the metastatic capacity of tumor cells.

The Canonical Wnt Signaling (Wnt/β-Catenin Pathway): A Potential Target for Cancer Prevention and Therapy

Precise regulation of signal transduction pathways is crucial for normal animal development and for maintaining cellular and tissue homeostasis in adults. The Wnt/Frizzled-mediated signaling includes canonical and non-canonical signal transduction pathways. Upregulation or downregulation of the canonical Wnt signaling (or the Wnt/β-Catenin signal transduction) leads to a variety of human diseases, including cancers, neurodegenerative disorders, skin and bone diseases, and heart deficiencies. Therefore, Wnt/β-Catenin signal transduction is a potential clinical target for the treatment of not only human cancers but also some other human chronic diseases. Here, some recent results including those from my laboratory highlighting the role of Wnt/β-Catenin signal transduction in human cancers will be reviewed. After a brief overview on canonical Wnt signaling and introducing some critical β-Catenin/T-cell factor-target genes, the interaction of canonical Wnt signaling with some common human cancers will be discussed. In the end, the different segments of the aforesaid signaling pathway, which have been considered as targets for clinical purposes, will be scrutinized.

WNT Signaling in Melanoma

WNT-signaling controls important cellular processes throughout embryonic development and adult life, so any deregulation of this signaling can result in a wide range of pathologies, including cancer. WNT-signaling is classified into two categories: β-catenin-dependent signaling (canonical pathway) and β-catenin-independent signaling (non-canonical pathway), the latter can be further divided into WNT/planar cell polarity (PCP) and calcium pathways. WNT ligands are considered as unique directional growth factors that contribute to both cell proliferation and polarity. Origin of cancer can be diverse and therefore tissue-specific differences can be found in WNT-signaling between cancers, including specific mutations contributing to cancer development. This review focuses on the role of the WNT-signaling pathway in melanoma. The current view on the role of WNT-signaling in cancer immunity as well as a short summary of WNT pathway-related drugs under investigation are also provided.

A Driver Never Works Alone-Interplay Networks of Mutant p53, MYC, RAS, and Other Universal Oncogenic Drivers in Human Cancer

The knowledge accumulating on the occurrence and mechanisms of the activation of oncogenes in human neoplasia necessitates an increasingly detailed understanding of their systemic interactions. None of the known oncogenic drivers work in isolation from the other oncogenic pathways. The cooperation between these pathways is an indispensable element of a multistep carcinogenesis, which apart from inactivation of tumor suppressors, always includes the activation of two or more proto-oncogenes. In this review we focus on representative examples of the interaction of major oncogenic drivers with one another. The drivers are selected according to the following criteria: (1) the highest frequency of known activation in human neoplasia (by mutations or otherwise), (2) activation in a wide range of neoplasia types (universality) and (3) as a part of a distinguishable pathway, (4) being a known cause of phenotypic addiction of neoplastic cells and thus a promising therapeutic target. Each of these universal oncogenic factors—mutant p53, KRAS and CMYC proteins, telomerase ribonucleoprotein, proteasome machinery, HSP molecular chaperones, NF-κB and WNT pathways, AP-1 and YAP/TAZ transcription factors and non-coding RNAs—has a vast network of molecular interrelations and common partners. Understanding this network allows for the hunt for novel therapeutic targets and protocols to counteract drug resistance in a clinical neoplasia treatment.

The anti-DKK1 antibody DKN-01 as an immunomodulatory combination partner for the treatment of cancer

INTRODUCTION

The Wnt/beta-catenin pathway is a complex signaling pathway known to be dysregulated in several cancers; Dickkopf-1 (Dkk1) is an inhibitor of canonical Wnt signaling via negative feedback. Elevated Dkk1 is associated with a poor prognosis in several cancers, including gynecologic and gastroesophageal malignancies. This review focuses on the potential therapeutic benefit of targeting Dkk1 with the IgG4 monoclonal antibody, DKN-01.

AREAS COVERED

We highlight current treatment approaches for advanced gynecologic and esophageal malignancies highlighting the need for more effective therapies, specifically improved immune-modulating agents and combinations. Our discussion of DKN-01 addresses the rationale for targeting Dkk1, available safety, pharmacokinetic and efficacy data.

EXPERT OPINION

DKN-01 presents an interesting therapeutic consideration in advanced gynecologic and gastroesophageal malignancies. It has been especially promising in patients with high-Dkk1-expressing tumors or known Wnt mutations. We postulate that the complementary mechanisms, limited adverse effects and emerging biomarker data position DKN-01 as a promising agent for combination therapy in patients with advanced malignancies. Specifically, we believe this occurs through an immuno-modulatory effect, primarily acting through the innate arm of the immune system. This highlights the possibility for addressing innate immune resistance and expanding the portion of patients who may benefit, possibly in a biomarker-selected manner.

Temporal activation of WNT/β-catenin signaling is sufficient to inhibit SOX10 expression and block melanoma growth

Despite advances in the systemic treatment of patients with metastatic melanoma using immune checkpoint and tyrosine kinase inhibitors (TKI), the majority of stage IV melanoma patients eventually succumb to the disease. We have previously identified the transcription factor Sox10 as a crucial player in melanoma, yet the underlying molecular mechanisms mediating Sox10-dependent tumorigenesis remain largely uncharacterized. Here, we show that MEK and RAF inhibitors do not suppress levels of SOX10 protein in patient-derived cells in vitro, as well as in melanoma patients in vivo. In a search for pharmacological inhibitors of SOX10, we performed a mass spectrometry-based screen in human melanoma cells. Subsequent analysis revealed that SOX10 directly interacts with β-catenin, which is a key mediator of canonical Wnt/β-catenin signaling. We demonstrate that inhibitors of glycogen synthase kinase 3 alpha/beta (GSK3α/β) efficiently abrogate SOX10 protein in human melanoma cells in vitro and in melanoma mouse models in vivo. The mechanism of action of GSK3-mediated SOX10 suppression is transcription-independent and relies on the presence of a proteasome degradable form of β-catenin. Taken together, we provide evidence that activation of canonical Wnt signaling has a profound effect on melanoma growth and is able to counteract Sox10-dependent melanoma maintenance both in vitro and in vivo.

The Role of PTEN Loss in Immune Escape, Melanoma Prognosis and Therapy Response

Checkpoint blockade therapies have changed the clinical management of metastatic melanoma patients considerably, showing survival benefits. Despite the clinical success, not all patients respond to treatment or they develop resistance. Although there are several treatment predictive biomarkers, understanding therapy resistance and the mechanisms of tumor immune evasion is crucial to increase the frequency of patients benefiting from treatment. The PTEN gene is thought to promote immune evasion and is frequently mutated in cancer and melanoma. Another feature of melanoma tumors that may affect the capacity of escaping T-cell recognition is melanoma cell dedifferentiation characterized by decreased expression of the microphtalmia-associated transcription factor (MITF) gene. In this study, we have explored the role of PTEN in prognosis, therapy response, and immune escape in the context of MITF expression using immunostaining and genomic data from a large cohort of metastatic melanoma. We confirmed in our cohort that PTEN alterations promote immune evasion highlighted by decreased frequency of T-cell infiltration in such tumors, resulting in a worse patient survival. More importantly, our results suggest that dedifferentiated PTEN negative melanoma tumors have poor patient outcome, no T-cell infiltration, and transcriptional properties rendering them resistant to targeted- and immuno-therapy.

How the ageing microenvironment influences tumour progression

Most cancers arise in individuals over the age of 60. As the world population is living longer and reaching older ages, cancer is becoming a substantial public health problem. It is estimated that, by 2050, more than 20% of the world's population will be over the age of 60 - the economic, healthcare and financial burdens this may place on society are far from trivial. In this Review, we address the role of the ageing microenvironment in the promotion of tumour progression. Specifically, we discuss the cellular and molecular changes in non-cancerous cells during ageing, and how these may contribute towards a tumour permissive microenvironment; these changes encompass biophysical alterations in the extracellular matrix, changes in secreted factors and changes in the immune system. We also discuss the contribution of these changes to responses to cancer therapy as ageing predicts outcomes of therapy, including survival. Yet, in preclinical studies, the contribution of the aged microenvironment to therapy response is largely ignored, with most studies designed in 8-week-old mice rather than older mice that reflect an age appropriate to the disease being modelled. This may explain, in part, the failure of many successful preclinical therapies upon their translation to the clinic. Overall, the intention of this Review is to provide an overview of the interplay that occurs between ageing cell types in the microenvironment and cancer cells and how this is likely to impact tumour metastasis and therapy response.

Array Comparative Genomic Hybridization Analysis Reveals Significantly Enriched Pathways in Canine Oral Melanoma

Human Mucosal Melanoma (hMM) is an aggressive neoplasm of neuroectodermal origin with distinctive features from the more common cutaneous form of malignant melanoma (cMM). At the molecular level, hMMs are characterized by large chromosomal aberrations rather than single-nucleotide mutations, typically observed in cMM. Given the scarcity of available cases, there have been many attempts to establish a reliable animal model. In pet dogs, Canine Oral Melanoma (COM) is the most common malignant tumor of the oral cavity, sharing clinical and histological aspects with hMM. To improve the knowledge about COM's genomic DNA alterations, in the present work, formalin-fixed, paraffin-embedded (FFPE) samples of COM from different European archives were collected to set up an array Comparative Genomic Hybridization (aCGH) analysis to estimate recurrent Copy Number Aberrations (CNAs). DNA was extracted in parallel from tumor and healthy fractions and 19 specimens were successfully submitted to labeling and competitive hybridization. Data were statistically analyzed through GISTIC2.0 and a pathway-enrichment analysis was performed with ClueGO. Recurrent gained regions were detected, affecting chromosomes CFA 10, 13 and 30, while lost regions involved chromosomes CFA 10, 11, 22, and 30. In particular, CFA 13 showed a whole-chromosome gain in 37% of the samples, while CFA 22 showed a whole-chromosome loss in 25%. A distinctive sigmoidal trend was observed in CFA 10 and 30 in 25 and 30% of the samples, respectively. Comparative analysis revealed that COM and hMM share common chromosomal changes in 32 regions. MAPK- and PI3K-related genes were the most frequently involved, while pathway analysis revealed statistically significant perturbation of cancer-related biological processes such as immune response, drug metabolism, melanocytes homeostasis, and neo-angiogenesis. The latter is a new evidence of a significant involvement of neovascularization-related pathways in COMs and can provide the rationale for future application in anti-cancer targeted therapies.

Pharmaceutical Topical Delivery of Poorly Soluble Polyphenols: Potential Role in Prevention and Treatment of Melanoma

Melanoma is regarded as the fifth and sixth most common cancer in men and women, respectively, and it is estimated that one person dies from melanoma every hour in the USA. Unfortunately, the treatment of melanoma is difficult because of its aggressive metastasis and resistance to treatment. The treatment of melanoma continues to be a challenging issue due to the limitations of available treatments such as a low response rate, severe adverse reactions, and significant toxicity. Natural polyphenols have attracted considerable attention from the scientific community due to their chemopreventive and chemotherapeutic efficacy. It has been suggested that poorly soluble polyphenols such as curcumin, resveratrol, quercetin, coumarin, and epigallocatechin-3-gallate may have significant benefits in the treatment of melanoma due to their antioxidant, anti-inflammatory, antiproliferative, and chemoprotective efficacies. The major obstacles for the use of polyphenolic compounds are low stability and poor bioavailability. Numerous nanoformulations, including solid lipid nanoparticles, polymeric nanoparticles, micelles, and liposomes, have been formulated to enhance the bioavailability and stability, as well as the therapeutic efficacy of polyphenols. This review will provide an overview of poorly soluble polyphenols that have been reported to have antimetastatic efficacy in melanomas.

Blocking Wnt as a therapeutic target in mice model of skin cancer

Wnt pathway plays an important role in controlling metabolism in cancer cells. It acts as positive modulator for both cell inflammation, through activation of NFκB, and fibrosis, through activation of TGF-β. Therefore, the aim of this study is to investigate the therapeutic effects of blocking Wnt pathway by IWP12 on skin cancer by studying its effects on skin cancer-induced inflammation and fibrosis in a mice model of skin cancer. Skin cancer was induced by application of 7,12-dimethylbenz[a]anthracene (DMBA) and croton oil on the dorsal skin of mice. Dorsal skin was removed for estimation of gene and protein expression of Wnt, β-catenin, SMAD, TGF-β, NFκB, TNF-α, IL-4 and IL-10. Part of the skin is stained with hematoxylin/eosin for assessment of cell structure. Treatment of mice with IWP12 completely blocked Wnt in skin cancer mice without affecting the control mice. Skin of tumorigenic mice showed marked skin hyperkeratosis, parakeratosis, acanthosis and dysplasia. Treatment with IWP12 markedly attenuated epidermal atypia and hyperplasia. In addition, IWP12 reduced expression of β-catenin, SMAD, TGF-β, NFκB and TNF-α associated with increase in the expression of IL-4 and IL-10. In conclusion, blocking Wnt production ameliorated skin cancer via blocking pro-inflammatory cytokines and enhancing the anti-inflammatory cytokines. Moreover, blocking Wnt attenuated skin cancer-induced activation of fibrosis pathway.

Macroenvironment-gene-microenvironment interactions in ultraviolet radiation-induced melanomagenesis

Cutaneous malignant melanoma is one of the few major cancers that continue to exhibit a positive rate of increase in the developed world. A wealth of epidemiological data has undisputedly implicated ultraviolet radiation (UVR) from sunlight and artificial sources as the major risk factor for melanomagenesis. However, the molecular mechanisms of this cause-and-effect relationship remain murky and understudied. Recent efforts on multiple fronts have brought unprecedented expansion of our knowledge base on this subject and it is now clear that melanoma is caused by a complex interaction between genetic predisposition and environmental exposure, primarily to UVR. Here we provide an overview of the effects of the macroenvironment (UVR) on the skin microenvironment and melanocyte-specific intrinsic (mostly genetic) landscape, which conspire to produce one of the deadliest malignancies.

SFRP5 inhibits the migration and invasion of melanoma cells through Wnt signaling pathway

Background

Secreted frizzled-related protein 5 (SFRP5) plays a key role in the development and progression of multiple tumors. However, the role and underlying mechanisms of SFRP5 in melanoma cells remain unknown.

Materials and methods

We used immunohistochemistry and Western blot analysis to detect the expression of SFRP5 in melanoma tissues and melanoma cells, respectively. Furthermore, both in vitro and in vivo assays were used to determine the effect of SFRP5 on malignant behavior in melanoma cells.

Results

We found that SFRP5 was markedly downregulated in melanoma tissues and cell lines. The SFRP5 overexpression exhibited no effect on the proliferation and apoptosis of melanoma cells but markedly suppressed the migration and invasion of melanoma cells in vitro. Regarding mechanisms, the SFRP5 overexpression inhibited the migration and invasion of melanoma cells by suppressing the epithelial–mesenchymal transition process and decreasing the matrix metalloproteinase-2/9 expression through the Wnt signaling pathway. Finally, in a xenograft animal model, we illustrated that the SFRP5 overexpression suppressed the tumor growth by decreasing angiogenesis and declined lung metastasis.

Conclusion

This study suggests that SFRP5 expression could be potentially useful in the invasion and metastasis of melanoma and serve as a putative promising target for human melanoma therapy.

Tissue-engineered 3D melanoma model with blood and lymphatic capillaries for drug development

While being the rarest skin cancer, melanoma is also the deadliest. To further drug discovery and improve clinical translation, new human cell-based in vitro models are needed. Our work strives to mimic the melanoma microenvironment in vitro as an alternative to animal testing. We used the self-assembly method to produce a 3D human melanoma model exempt of exogenous biomaterial. This model is based on primary human skin cells and melanoma cell lines while including a key feature for tumor progression: blood and lymphatic capillaries. Major components of the tumor microenvironment such as capillaries, human extracellular matrix, a stratified epidermis (involucrin, filaggrin) and basement membrane (laminin 332) are recapitulated in vitro. We demonstrate the persistence of CD31+ blood and podoplanin+/LYVE-1+ lymphatic capillaries in the engineered tissue. Chronic treatment with vemurafenib was applied to the model and elicited a dose-dependent response on proliferation and apoptosis, making it a promising tool to test new compounds in a human-like environment.

Antagonistic role of Klotho-derived peptides dynamics in the pancreatic cancer treatment through obstructing WNT-1 and Frizzled binding

Klotho is an anti-aging protein that is engaged in the suppression of canonical WNT signaling. In this study, we investigated the expression pattern of human WNTs and Klotho in the pancreatic cancer. In the cancerous cells, WNT-1 exhibited much higher expression as compared to other WNTs, while no WNT expression was detected in the normal tissue. In contrast, Klotho expression was significantly low in the cancerous tissue. Based on these observations, we intended to explore Klotho binding to WNT-1 and cystein-rich domains (CRDs) of Frizzled (FZD) homologs through molecular docking and dynamics simulation assays. Interestingly, similar region of WNT-1 was detected in binding with Klotho and CRDs of FZD-1/2. FZD-CRDs were grasped by the association of peripheral hydrophobic residues of WNT-1 U-shaped cavity. Subsequently, WNT-1-bound Klotho-peptides were isolated and reevaluated for their binding abilities against WNT-1 and FZD-CRDs., The conformational readjustements of these complexes were deeply analyzed by calculating the size of WNT-1 U-shaped cavity. In comparison to apo-WNT-1, cavity opening was markedly enhanced (8.2 Å to 15.64 Å, 32.89 Å and 35.11 Å) in WNT-1-a, WNT-1-c and WNT-1-e complexes, respectively. Thus Klotho-derived peptides may facilitate distinct conformational changes in the WNT-1-FZD associated region. As a result, aberrant loss of FZD binding may lead to augment WNT signaling. Overall, current study opens up new avenues in the pancreatic cancer therapeutics through antagonizing WNT-1 by Klotho.

BRN2, a POUerful driver of melanoma phenotype switching and metastasis

The POU domain family of transcription factors play a central role in embryogenesis and are highly expressed in neural crest cells and the developing brain. BRN2 is a class III POU domain protein that is a key mediator of neuroendocrine and melanocytic development and differentiation. While BRN2 is a central regulator in numerous developmental programs, it has also emerged as a major player in the biology of tumourigenesis. In melanoma, BRN2 has been implicated as one of the master regulators of the acquisition of invasive behaviour within the phenotype switching model of progression. As a mediator of melanoma cell phenotype switching, it coordinates the transition to a dedifferentiated, slow cycling and highly motile cell type. Its inverse expression relationship with MITF is believed to mediate tumour progression and metastasis within this model. Recent evidence has now outlined a potential epigenetic switching mechanism in melanoma cells driven by BRN2 expression that induces melanoma cell invasion. We summarize the role of BRN2 in tumour cell dissemination and metastasis in melanoma, while also examining it as a potential metastatic regulator in other tumour models.

Multi‑layered prevention and treatment of chronic inflammation, organ fibrosis and cancer associated with canonical WNT/β‑catenin signaling activation (Review)

β-catenin/CTNNB1 is an intracellular scaffold protein that interacts with adhesion molecules (E-cadherin/CDH1, N-cadherin/CDH2, VE-cadherin/CDH5 and α-catenins), transmembrane-type mucins (MUC1/CD227 and MUC16/CA125), signaling regulators (APC, AXIN1, AXIN2 and NHERF1/EBP50) and epigenetic or transcriptional regulators (BCL9, BCL9L, CREBBP/CBP, EP300/p300, FOXM1, MED12, SMARCA4/BRG1 and TCF/LEF). Gain-of-function CTTNB1 mutations are detected in bladder cancer, colorectal cancer, gastric cancer, liver cancer, lung cancer, pancreatic cancer, prostate cancer and uterine cancer, whereas loss-of-function CTNNB1 mutations are also detected in human cancer. ABCB1, ALDH1A1, ASCL2, ATF3, AXIN2, BAMBI, CCND1, CD44, CLDN1, CTLA4, DKK1, EDN1, EOMES, FGF18, FGF20, FZD7, IL10, JAG1, LEF1, LGR5, MITF, MSX1, MYC, NEUROD1, NKD1, NODAL, NOTCH2, NOTUM, NRCAM, OPN, PAX3, PPARD, PTGS2, RNF43, SNAI1, SP5, TCF7, TERT, TNFRSF19, VEGFA and ZNRF3 are representative β-catenin target genes. β-catenin signaling is involved in myofibroblast activation and subsequent pulmonary fibrosis, in addition to other types of fibrosis. β-catenin and NF-κB signaling activation are involved in field cancerization in the stomach associated with Helicobacter pylori (H. pylori) infection and in the liver associated with hepatitis C virus (HCV) infection and other etiologies. β-catenin-targeted therapeutics are functionally classified into β-catenin inhibitors targeting upstream regulators (AZ1366, ETC-159, G007-LK, GNF6231, ipafricept, NVP-TNKS656, rosmantuzumab, vantictumab, WNT-C59, WNT974 and XAV939), β-catenin inhibitors targeting protein-protein interactions (CGP049090, CWP232228, E7386, ICG-001, LF3 and PRI-724), β-catenin inhibitors targeting epigenetic regulators (PKF118-310), β-catenin inhibitors targeting mediator complexes (CCT251545 and cortistatin A) and β-catenin inhibitors targeting transmembrane-type transcriptional outputs, including CD44v6, FZD7 and LGR5. Eradicating H. pylori and HCV is the optimal approach for the first-line prevention of gastric cancer and hepatocellular carcinoma (HCC), respectively. However, β-catenin inhibitors may be applicable for the prevention of organ fibrosis, second-line HCC prevention and treating β-catenin-driven cancer. The multi-layered prevention and treatment strategy of β-catenin-related human diseases is necessary for the practice of personalized medicine and implementation of precision medicine.

Dimerization of p15RS mediated by a leucine zipper-like motif is critical for its inhibitory role on Wnt signaling

We previously demonstrated that p15RS, a newly discovered tumor suppressor, inhibits Wnt/β-catenin signaling by interrupting the formation of β-catenin·TCF4 complex. However, it remains unclear how p15RS helps exert such an inhibitory effect on Wnt signaling based on its molecular structure. In this study, we reported that dimerization of p15RS is required for its inhibition on the transcription regulation of Wnt-targeted genes. We found that p15RS forms a dimer through a highly conserved leucine zipper-like motif in the coiled-coil terminus domain. In particular, residues Leu-248 and Leu-255 were identified as being responsible for p15RS dimerization, as mutation of these two leucines into prolines disrupted the homodimer formation of p15RS and weakened its suppression of Wnt signaling. Functional studies further confirmed that mutations of p15RS at these residues results in diminishment of its inhibition on cell proliferation and tumor formation. We therefore concluded that dimerization of p15RS governed by the leucine zipper-like motif is critical for its inhibition of Wnt/β-catenin signaling and tumorigenesis.

Nanoparticle-Mediated Trapping of Wnt Family Member 5A in Tumor Microenvironments Enhances Immunotherapy for B-Raf Proto-Oncogene Mutant Melanoma

Development of an effective treatment against advanced tumors remains a major challenge for cancer immunotherapy. Approximately 50% of human melanoma is driven by B-Raf proto-oncogene mutation (BRAF mutant). Tumors with such mutation are desmoplastic, highly immunosuppressive, and often resistant to immune checkpoint therapies. We have shown that immunotherapy mediated by low-dose doxorubicin-induced immunogenic cell death was only partially effective for this type of tumor and not effective in long-term inhibition of tumor progression. Wnt family member 5A (Wnt5a), a signaling protein highly produced by BRAF mutant melanoma cells, has been implicated in inducing dendritic cell tolerance and tumor fibrosis, thus hindering effective antigen presentation and T-cell infiltration. We hypothesized that Wnt5a is a key molecule controlling the immunosuppressive tumor microenvironment in metastatic melanoma. Accordingly, we have designed and generated a trimeric trap protein, containing the extracellular domain of Fizzled 7 receptor that binds Wnt5a with a K_d ∼ 278 nM. Plasmid DNA encoding for the Wnt5a trap was delivered to the tumor by using cationic lipid-protamine-DNA nanoparticles. Expression of Wnt5a trap in the tumor, although transient, was greater than that of any other major organs including liver, resulting in a significant reduction of the Wnt5a level in the tumor microenvironment without systematic toxicity. Significantly, combination of Wnt5a trapping and low-dose doxorubicin showed great tumor growth inhibition and host survival prolongation. Our findings indicated that efficient local Wnt5a trapping significantly remodeled the immunosuppressive tumor microenvironment to facilitate immunogenic cell-death-mediated immunotherapy.

1-Benzyl-indole-3-carbinol is a highly potent new small molecule inhibitor of Wnt/β-catenin signaling in melanoma cells that coordinately inhibits cell proliferation and disrupts expression of microphthalmia-associated transcription factor isoform-M

1-Benzyl-indole-3-carbinol (1-benzyl-I3C), a synthetic analogue of the crucifer-derived natural phytochemical I3C, displayed significantly wider sensitivity and anti-proliferative potency in melanoma cells than the natural compound. Unlike I3C, which targets mainly oncogenic BRAF-expressing cells, 1-benzyl-I3C effectively inhibited proliferation of melanoma cells with a more extensive range of mutational profiles, including those expressing wild-type BRAF. In both cultured melanoma cell lines and in vivo in melanoma cell-derived tumor xenografts, 1-benzyl-I3C disrupted canonical Wnt/β-catenin signaling that resulted in the downregulation of β-catenin protein levels with a concomitant increase in levels of the β-catenin destruction complex components such as glycogen synthase kinase-3β (GSK-3β) and Axin. Concurrent with the inhibition of Wnt/β-catenin signaling, 1-benzyl-I3C strongly downregulated expression of the melanoma master regulator, microphthalmia-associated transcription factor isoform-M (MITF-M) by inhibiting promoter activity through the consensus lymphoid enhancer factor-1 (LEF-1)/T-cell transcription factor (TCF) DNA-binding site. Chromatin immunoprecipitation revealed that 1-benzyl-I3C downregulated interactions of endogenous LEF-1 with the MITF-M promoter. 1-Benzyl-I3C ablated Wnt-activated LEF-1-dependent reporter gene activity in a TOP FLASH assay that was rescued by expression of a constitutively active form of the Wnt co-receptor low-density lipoprotein receptor-related protein (LRP6), indicating that 1-benzyl-I3C disrupts Wnt/β-catenin signaling at or upstream of LRP6. In oncogenic BRAF-expressing melanoma cells, combinations of 1-benzyl-I3C and Vemurafenib, a clinically employed BRAF inhibitor, showed strong anti-proliferative effects. Taken together, our observations demonstrate that 1-benzyl-I3C represents a new and highly potent indolecarbinol-based small molecule inhibitor of Wnt/β-catenin signaling that has intriguing translational potential, alone or in combination with other anti-cancer agents, to treat human melanoma.

RTL1 promotes melanoma proliferation by regulating Wnt/β-catenin signalling

Cutaneous melanoma is a highly malignant and metastatic skin cancer with high mortality. However, its underlying mechanisms remain largely unclear. Here, we found that retrotransposon-like 1 (RTL1) is highly enriched in melanoma tissue, especially in early and horizontal growth tissues. Knockdown of RTL1 in melanoma cells resulted in cell proliferation suppression; cell cycle arrest at G1 phase; and down-regulation of E2F1, CYCLIN D1, cyclin-dependent kinase 6 (CDK6) and c-MYC. Moreover, overexpression of RTL1 in melanoma cells accelerated cell proliferation, promoted passage of the cell cycle beyond G1 phase, and increased the expression of cell cycle related genes. Mechanistically, we found that knockdown of RTL1 inhibited the Wnt/β-Catenin pathway by regulating the expression of genes specifically involved in β-CATENIN stabilization. Furthermore, the overexpression and knockdown of β-CATENIN rescued the effects of RTL1 on melanoma cell proliferation and the cell cycle. These findings were also confirmed via tumour xenografts in nude mice. Together, our results demonstrated that RTL1 promotes melanoma cell proliferation by regulating the Wnt/β-Catenin signalling pathway.

A molecular atlas of the developing ectoderm defines neural, neural crest, placode, and nonneural progenitor identity in vertebrates

During vertebrate neurulation, the embryonic ectoderm is patterned into lineage progenitors for neural plate, neural crest, placodes and epidermis. Here, we use Xenopus laevis embryos to analyze the spatial and temporal transcriptome of distinct ectodermal domains in the course of neurulation, during the establishment of cell lineages. In order to define the transcriptome of small groups of cells from a single germ layer and to retain spatial information, dorsal and ventral ectoderm was subdivided along the anterior-posterior and medial-lateral axes by microdissections. Principal component analysis on the transcriptomes of these ectoderm fragments primarily identifies embryonic axes and temporal dynamics. This provides a genetic code to define positional information of any ectoderm sample along the anterior-posterior and dorsal-ventral axes directly from its transcriptome. In parallel, we use nonnegative matrix factorization to predict enhanced gene expression maps onto early and mid-neurula embryos, and specific signatures for each ectoderm area. The clustering of spatial and temporal datasets allowed detection of multiple biologically relevant groups (e.g., Wnt signaling, neural crest development, sensory placode specification, ciliogenesis, germ layer specification). We provide an interactive network interface, EctoMap, for exploring synexpression relationships among genes expressed in the neurula, and suggest several strategies to use this comprehensive dataset to address questions in developmental biology as well as stem cell or cancer research.

Vertebrate embryo germ layers become progressively regionalized by evolutionarily conserved molecular processes. Catching the early steps of this dynamic spatial cell diversification at the scale of the transcriptome was challenging, even with the advent of efficient RNA sequencing. We have microdissected complementary and defined areas of a single germ layer, the developing ectoderm, and explored how the transcriptome changes over time and space in the ectoderm during the differentiation of frog epidermis, neural plate, and neural crest. We have created EctoMap, a searchable interface using these regional transcriptomes, to predict the expression of the 31 thousand genes expressed in neurulae and their networks of co-expression, predictive of functional relationships. Through several examples, we illustrate how these data provide insights in development, cancer, evolution and stem cell biology.

Molecular genetics and targeted therapy of WNT-related human diseases (Review)

Canonical WNT signaling through Frizzled and LRP5/6 receptors is transduced to the WNT/β-catenin and WNT/stabilization of proteins (STOP) signaling cascades to regulate cell fate and proliferation, whereas non-canonical WNT signaling through Frizzled or ROR receptors is transduced to the WNT/planar cell polarity (PCP), WNT/G protein-coupled receptor (GPCR) and WNT/receptor tyrosine kinase (RTK) signaling cascades to regulate cytoskeletal dynamics and directional cell movement. WNT/β-catenin signaling cascade crosstalks with RTK/SRK and GPCR-cAMP-PKA signaling cascades to regulate β-catenin phosphorylation and β-catenin-dependent transcription. Germline mutations in WNT signaling molecules cause hereditary colorectal cancer, bone diseases, exudative vitreoretinopathy, intellectual disability syndrome and PCP-related diseases. APC or CTNNB1 mutations in colorectal, endometrial and prostate cancers activate the WNT/β-catenin signaling cascade. RNF43, ZNRF3, RSPO2 or RSPO3 alterations in breast, colorectal, gastric, pancreatic and other cancers activate the WNT/β-catenin, WNT/STOP and other WNT signaling cascades. ROR1 upregulation in B-cell leukemia and solid tumors and ROR2 upregulation in melanoma induce invasion, metastasis and therapeutic resistance through Rho-ROCK, Rac-JNK, PI3K-AKT and YAP signaling activation. WNT signaling in cancer, stromal and immune cells dynamically orchestrate immune evasion and antitumor immunity in a cell context-dependent manner. Porcupine (PORCN), RSPO3, WNT2B, FZD5, FZD10, ROR1, tankyrase and β-catenin are targets of anti-WNT signaling therapy, and ETC-159, LGK974, OMP-18R5 (vantictumab), OMP-54F28 (ipafricept), OMP-131R10 (rosmantuzumab), PRI-724 and UC-961 (cirmtuzumab) are in clinical trials for cancer patients. Different classes of anti-WNT signaling therapeutics are necessary for the treatment of APC/CTNNB1-, RNF43/ZNRF3/RSPO2/RSPO3- and ROR1-types of human cancers. By contrast, Dickkopf-related protein 1 (DKK1), SOST and glycogen synthase kinase 3β (GSK3β) are targets of pro-WNT signaling therapy, and anti-DKK1 (BHQ880 and DKN-01) and anti-SOST (blosozumab, BPS804 and romosozumab) monoclonal antibodies are being tested in clinical trials for cancer patients and osteoporotic post-menopausal women. WNT-targeting therapeutics have also been applied as reagents for in vitro stem-cell processing in the field of regenerative medicine.

Aberrant Wnt signaling: a special focus in CNS diseases

Wnt signals regulate cell proliferation, migration and differentiation during development, as well as synaptic transmission and plasticity in the adult brain. Abnormal Wnt signaling is central to a number of brain pathologies. We review here, the significance of this pathway focused in the contribution of the most frequent alterations in receptors, secretable modulators and downstream targets in Alzheimer's disease (AD) and Glioblastoma (GBM). β-catenin and GSK3 levels are pivotal in the neurodegeneration associated to AD contributing to memory deficits, tau phosphorylation, increased β-amyloid production and modulation of Apolipoprotein E in the brain. In consequence, β-catenin and GSK3 are targets for potential treatments in AD. Also, Wnt pathway components and secreted molecules interfering with this signaling contribute to the progression of tumoral cells. Wnt pathway activation is a bad prognosis in brain cancer; however, mutations in WNT or Frizzled (FZD) genes do not account for the cases of GBM. Instead, recent studies indicate that epigenetic modifications contribute to the development of GBMs opening novel strategies to study GBM progression.