Malignant Melanoma: An Overview, New Perspectives, and Vitamin D Signaling

Role of ELP6 in tumour progression and impact on ERK1/2 signalling pathway inhibitors in skin cutaneous melanoma

Elongator acetyltransferase complex subunit 6 (ELP6), a subunit of the elongator complex, can increase the migratory potential of melanoma cells in vitro. However, the clinical relevance of ELP6 in patients with melanoma remains unclear. The present study aimed to investigate the role of ELP6 expression in melanoma progression and association with patient survival rates. Transcriptomic data from patients with melanoma available in The Cancer Genome Atlas, Gene Expression Profiling Interactive Analysis and cBioPortal databases were analysed to evaluate the associations between ELP6 expression levels and patient survival. In vitro experiments were conducted using short hairpin RNAs to downregulate ELP6, with a focus on cell viability, cell cycle regulation and the ERK1/2 signalling pathway. ELP6 expression levels were significantly elevated in patients with melanoma and were associated with poor survival outcomes. Knockdown of ELP6 resulted in decreased expression levels of p42 MAPK, reduced cell viability, G1 phase cell cycle arrest and led to reduced responsiveness to the MEK1/2 inhibitor U0126. ELP6 promotes melanoma progression via the ERK1/2 signalling pathway. Therefore, assessing ELP6 expression may offer potential therapeutic strategies for patients with melanoma.

Neuro-immuno-endocrinology of the skin: how environment regulates body homeostasis

The skin, including the hypodermis, is the largest organ of the body. The epidermis, the uppermost layer, is in direct contact with the environment and is exposed to environmental stressors, including solar radiation and biological, chemical and physical factors. These environmental factors trigger local responses within the skin that modulate homeostasis on both the cutaneous and systemic levels. Using mediators in common with brain pathways, immune and neuroendocrine systems within the skin regulate these responses to activate various signal transduction pathways and influence the systemic endocrine and immune systems in a context-dependent manner. This skin neuro-immuno-endocrine system is compartmentalized through the formation of epidermal, dermal, hypodermal and adnexal regulatory units. These units can act separately or in concert to preserve skin integrity, allow for adaptation to a changing environment and prevent the development of pathological processes. Through activation of peripheral nerve endings, the release of neurotransmitters, hormones, neuropeptides, and cytokines and/or chemokines into the circulation, or by priming circulating and resident immune cells, this system affects central coordinating centres and global homeostasis, thus adjusting the body's homeostasis and allostasis to optimally respond to the changing environment.

PPAR-γ in Melanoma and Immune Cells: Insights into Disease Pathogenesis and Therapeutic Implications

Changes in skin pigmentation, like hyperpigmentation or moles, can affect appearance and social life. Unlike locally containable moles, malignant melanomas are aggressive and can spread rapidly, disproportionately affecting younger individuals with a high potential for metastasis. Research has shown that the peroxisome proliferator-activated receptor gamma (PPAR-γ) and its ligands exhibit protective effects against melanoma. As a transcription factor, PPAR-γ is crucial in functions like fatty acid storage and glucose metabolism. Activation of PPAR-γ promotes lipid uptake and enhances sensitivity to insulin. In many cases, it also inhibits the growth of cancer cell lines, like breast, gastric, lung, and prostate cancer. In melanoma, PPAR-γ regulates cell proliferation, differentiation, apoptosis, and survival. During tumorigenesis, it controls metabolic changes and the immunogenicity of stromal cells. PPAR-γ agonists can target hypoxia-induced angiogenesis in tumor therapy, but their effects on tumors can be suppressive or promotional, depending on the tumor environment. Published data show that PPAR-γ-targeting agents can be effective in specific groups of patients, but further studies are needed to understand lesser-known biological effects of PPAR-γ and address the existing safety concerns. This review provides a summary of the current understanding of PPAR-γ and its involvement in melanoma.

Molecular insights of vitamin D receptor SNPs and vitamin D analogs: a novel therapeutic avenue for vitiligo

Vitamin D receptor (VDR) agonists play a pivotal role in modulating immune responses and promoting melanocyte survival, making them potential candidates for vitiligo treatment. The VDR gene is integral to mediating the effects of vitamin D in the immune system, and disruptions in its structure due to missense mutations may significantly contribute to the pathogenesis of vitiligo. Missense single-nucleotide polymorphisms (SNPs) can alter the amino acid sequence of the VDR protein, potentially affecting its ligand-binding affinity and downstream signaling. Investigating these missense SNPs provides critical insights into the genetic underpinnings of vitiligo and may help identify biomarkers for early detection and precision-targeted therapies. This study explored the therapeutic potential of vitamin D analogs in vitiligo management, with a particular focus on their binding interactions and molecular efficacy. Using molecular docking and virtual screening, 24 vitamin D analogs were evaluated. Calcipotriol exhibited the highest binding affinity (-11.4 kcal/mol) and unique interactions with key residues in the VDR ligand-binding domain. Additionally, an analysis of structural variations stemming from missense mutations in the VDR gene highlighted potential impacts on receptor-ligand interactions, further emphasizing the importance of genetic factors in treatment response. These findings underscore the potential of calcipotriol to promote melanogenesis and modulate pigmentation in vitiligo. A comparative analysis identified structural variations influencing the efficacy of other analogs, such as calcitriol and tacalcitol. Although the in silico methods provided valuable insights, the study acknowledges the limitations of excluding dynamic cellular environments and emphasizes the need for experimental validation. Overall, this study enhances our understanding of VDR-targeted therapies, and calcipotriol is a promising candidate for further development in the management of vitiligo.

Iron metabolism and the tumor microenvironment: A new perspective on cancer intervention and therapy (Review)

Iron metabolism plays a crucial role in the tumor microenvironment, influencing various aspects of cancer cell biology and tumor progression. This review discusses the regulatory mechanisms of iron metabolism within the tumor microenvironment and highlights how tumor cells and associated stromal cells manage iron uptake, accumulation and regulation. The sources of iron within tumors and the biological importance of ferroptosis in cancer were explored, focusing on its mechanisms, biological effects and, in particular, its tumor‑suppressive properties. Furthermore, the protective strategies employed by cancer cells to evade ferroptosis were examined. This review also delves into the intricate relationship between iron metabolism and immune modulation within the tumor microenvironment, detailing the impact on tumor‑associated immune cells and immune evasion. The interplay between ferroptosis and immunotherapy is discussed and potential strategies to enhance cancer immunotherapy by modulating iron metabolism are presented. Finally, the current ferroptosis‑based cancer therapeutic approaches were summarized and future directions for therapies that target iron metabolism were proposed.

Small-Molecule Tyrosinase Inhibitors for Treatment of Hyperpigmentation

Increasing attention is being focused on skin health currently, especially the excessive deposition of melanin in the skin. Tyrosinase, the rate-limiting enzyme in melanin biosynthesis, is a crucial enzyme in melanin synthesis. However, existing tyrosinase inhibitors pose some degree of toxicity to humans. Therefore, the development of more efficient and low-toxicity tyrosinase inhibitors is urgently needed. This review briefly depicts the melanin biosynthesis process and the crystal structure and catalytic mechanism of tyrosinase. The latest research progress regarding small-molecule tyrosinase inhibitors is also reviewed. Moreover, the structure-function relationships are analyzed and summarized. This is expected to provide new and more scientific insights to enable researchers to explore safer and more potent tyrosinase inhibitors.

Paradigm of biomarkers in metastatic melanoma (Review)

Metastatic melanoma is an aggressive and deadly form of skin cancer, known for its rapid ability to spread to other organs. Melanoma metastasis involves several steps: Local invasion, lymphovascular invasion and proliferation to new sites. This process is facilitated by genetic alterations, interactions with the tumor microenvironment and evasion of the immune system. Despite advances in therapies, the 5-year survival rate remains low at ~22.5%. Notably, current research is focused on identifying patients who may benefit from specific treatments, considering factors such as mutational load and programmed death ligand 1 expression. BRAF inhibitors and immune checkpoint inhibitors have improved survival, although numerous patients do not respond or develop resistance, underscoring the need for novel biomarkers to optimize treatment and monitoring of the disease. In summary, the purpose of the present article is to review the different serological, histological, microRNA and circulating tumor cell biomarkers that have proven useful in the diagnosis, follow-up and prognosis of metastatic melanoma. These biomarkers represent a promising area for research and clinical application, with the aim of offering more precise and personalized treatments.

Temozolomide-Promoted MGMT Transcription Contributes to Chemoresistance by Activating the ERK Signalling Pathway in Malignant Melanoma

Tumour cells possess a multitude of chemoresistance mechanisms, which could plausibly contribute to the ineffectiveness of chemotherapy. O6-methylguanine-DNA methyltransferase (MGMT) is an important effector protein associated with Temozolomide (TMZ) resistance in various tumours. To some extent, the expression level of MGMT determines the sensitivity of cells to TMZ, but the mechanism of its expression regulation has not been fully elucidated. Cultured malignant melanoma cell lines A375 and Sk-MEL28 were employed. A luciferase assay was used to detect the transcriptional activity of the MGMT promoter. Western blotting was used to compare the expression levels of phosphorylated ERK1/2 (P-ERK1/2) after TMZ treatment. Immunofluorescent staining was used to detect TMZ-induced DNA damage protein levels. The sensitivity of melanoma cells to TMZ was detected by MTT assay and animal experiments. The expression of MGMT mRNA was tested by Quantitative real-time PCR (RT-qPCR). Flow cytometry was used to measure the apoptosis of TMZ-treated cells. TMZ enhanced the transcription of MGMT through activating the ERK pathway. ERK inhibitors U0126 and vemurafenib (vMF) inhibited the TMZ induced transcription of MGMT. The expression of MGMT and p-ERK1/2 was closely related in human MM tissues. vMF increased the sensitivity of melanoma (MM) to TMZ in vitro and in vivo through downregulating MGMT and promoting the TMZ induced DNA damage in MM. TMZ-promoted MGMT transcription contributed to instinctive chemoresistance by activating the ERK signalling pathway in malignant melanoma. Our study indicates that the use of the ERK inhibitor in combination with TMZ could potentially enhance the effectiveness of clinical treatment for malignant melanoma.

Deep Learning for Melanoma Detection: A Deep Learning Approach to Differentiating Malignant Melanoma from Benign Melanocytic Nevi

Background/Objectives: Melanoma, an aggressive form of skin cancer, accounts for a significant proportion of skin-cancer-related deaths worldwide. Early and accurate differentiation between melanoma and benign melanocytic nevi is critical for improving survival rates but remains challenging because of diagnostic variability. Convolutional neural networks (CNNs) have shown promise in automating melanoma detection with accuracy comparable to expert dermatologists. This study evaluates and compares the performance of four CNN architectures-DenseNet121, ResNet50V2, NASNetMobile, and MobileNetV2-for the binary classification of dermoscopic images. Methods: A dataset of 8825 dermoscopic images from DermNet was standardized and divided into training (80%), validation (10%), and testing (10%) subsets. Image augmentation techniques were applied to enhance model generalizability. The CNN architectures were pre-trained on ImageNet and customized for binary classification. Models were trained using the Adam optimizer and evaluated based on accuracy, area under the receiver operating characteristic curve (AUC-ROC), inference time, and model size. The statistical significance of the differences was assessed using McNemar's test. Results: DenseNet121 achieved the highest accuracy (92.30%) and an AUC of 0.951, while ResNet50V2 recorded the highest AUC (0.957). MobileNetV2 combined efficiency with competitive performance, achieving a 92.19% accuracy, the smallest model size (9.89 MB), and the fastest inference time (23.46 ms). NASNetMobile, despite its compact size, had a slower inference time (108.67 ms), and slightly lower accuracy (90.94%). Performance differences among the models were statistically significant (p < 0.0001). Conclusions: DenseNet121 demonstrated a superior diagnostic performance, while MobileNetV2 provided the most efficient solution for deployment in resource-constrained settings. The CNNs show substantial potential for improving melanoma detection in clinical and mobile applications.

ZNF197-AS1/miR-425/GABARAPL1 axis: a novel regulatory mechanism in uveal melanoma

This study investigates the role of the long noncoding RNA (lncRNA) ZNF197-AS1 in uveal melanoma (UM), focusing on its function within a competing endogenous RNA (ceRNA) network. Using the UM-related TCGA (The Cancer Genome Atlas) dataset, we analyzed the expression levels of ZNF197-AS1 and its correlation with miR-425 and GABARAPL1, an essential autophagy-related gene. Our analysis revealed that ZNF197-AS1 acts as a ceRNA by competitively binding to miR-425, resulting in the upregulation of GABARAPL1. This interaction plays a crucial role in the growth and metastasis of UM. The expression of GABARAPL1 showed a strong correlation with the clinical outcomes of patients with UM. Furthermore, in vitro assays confirmed that ZNF197-AS1 impedes UM cell proliferation, migration, and invasion by modulating the miR-425/GABARAPL1 axis. These findings suggest that ZNF197-AS1 can effectively inhibit UM progression through this ceRNA regulatory network. This study provides valuable insights into the molecular mechanisms underlying UM and highlights the potential of targeting the ZNF197-AS1/miR-425/GABARAPL1 axis as a therapeutic strategy for UM.NEW & NOTEWORTHY This study identifies the ZNF197-AS1/miR-425/GABARAPL1 axis as a novel regulatory mechanism in uveal melanoma. ZNF197-AS1 upregulates GABARAPL1 by sponging miR-425, inhibiting UM cell proliferation, migration, and invasion. This discovery highlights a potential therapeutic target, providing new insights into UM progression and patient outcomes.

Marizomib Promotes Senescence or Long-Term Apoptosis in Melanoma Cancer Cells

Cellular senescence is cell cycle arrest and the inhibition of cell proliferation. New anticancer approaches include the elimination of cancer cells through the induction of senescence followed by senolysis. New prosenescence compounds are still being searched for. Little is known about the ability of proteasome inhibitors to induce senescence in tumor cells, especially in malignant melanoma. The aim of our study was to verify the activity of a natural proteasome inhibitor-marizomib (MZB)-directly after incubation and after its removal to assess its potential to induce senescence or long-term apoptosis in malignant melanoma cell lines (A375 and G361). After 48 h of incubation with MZB, we observed an increased number of SA-β-galactosidase-positive cells, upregulated expression of P21 and P-P53 proteins and an increased number of cells at the subG1 phase (line G361) or at both the subG1 and G2/M phases (line A375). After 96 h from inhibitor removal, the G361 line presented signs of senescence (increased level of SA-β-galactosidase, IL-8, P-P53, G2/M and S phases of cell cycle, decreased lamin B1 and cleaved lamin B1), while the A375 line demonstrated more signs of apoptosis (increased subG1 phase, P-P53, cleaved lamin B1). The gathered findings suggest that MZB resulted in the induction of cellular senescence (line G361) or enhanced apoptosis (line A375) in the melanoma cell lines tested here and could be a promising therapeutic factor in malignant melanoma treatment.

Polygenic Risk Score Improves Melanoma Risk Assessment in a Patient Cohort from the Veneto Region of Italy

Recent genome-wide association studies (GWASs) have identified many single nucleotide polymorphisms (SNPs) that alone weakly affect melanoma risk, but their combined effect on a polygenic risk score (PRS) can have a far bigger impact on estimating risk. However, the PRS is not yet at the stage of being utilized in clinical practice, and further evidence is needed. In this study, 270 melanoma patients fulfilling the criteria for a suspected genetic predisposition but with a negative genetic test for high/medium-penetrance genes were genotyped for 57 SNPs selected in previous GWASs to construct a PRS model. We found a significantly higher mean PRS57 in all melanoma cases than in controls (0.58 vs. 0.00, p < 0.001), and the mean PRS57 in multiple primary melanoma cases was twice that in single melanoma cases (0.689 vs. 0.362, p = 0.025). Interestingly, our results confirm the association of the PRS57 not only with other melanoma risk factors but also with a younger age at diagnosis. This evidence supports the potentially powerful discriminative role of PRS in the selection of high-risk patients who should undergo stricter surveillance protocols.

1α,25-hydroxyvitamin D/VDR suppresses stem-like properties of ovarian cancer cells by restraining nuclear translocation of β-catenin

Several studies have indicated that 1α,25-hydroxyvitamin D [1α,25(OH)2D3] inhibits the proliferation and metastasis of cancer cells through suppressing epithelial-mesenchymal transition. However, its influence on the translocation of β-catenin remains unclear. In the present study, ovarian cancer stem-like cells (CSCs), including side population (SP) and CD44+/CD117+, were isolated from mouse ovarian surface epithelial (MOSE) cells with malignant transformation. The findings revealed that 1α,25(OH)2D3 obviously reduced the sphere-forming ability, as well as Notch1 and Klf levels. Moreover, the limiting dilution assay demonstrated that 1α,25(OH)2D3 effectively hindered the tumorigenesis of ovarian CSCs in vitro. Notably, treatment with 1α,25(OH)2D3 led to a substantial increase in the cell population of CD44+/CD117+ forming one tumor from ≤ 100 to 445 in orthotopic transplanted model, indicating a pronounced suppression of stemness of ovarian CSCs. Additionally, 1α,25(OH)2D3 robustly promoted the translocation of β-catenin from the nuclear to the cytoplasm through directly binding to VDR, which resulted in decreased levels of c-Myc and CyclinD1 within late MOSE cells. Taken together, these results strongly supported the role of 1α,25(OH)2D3 in inhibiting stem-like properties in ovarian cancer cells by restraining nuclear translocation of β-catenin, thereby offering a promising target for cancer therapeutics.

Anticancer Activity of Vitamin D, Lumisterol and Selected Derivatives against Human Malignant Melanoma Cell Lines

Despite the recent development of improved methods of treating melanoma such as targeted therapy, immunotherapy or combined treatment, the number of new cases worldwide is increasing. It is well known that active metabolites of vitamin D3 and lumisterol (L3) exert photoprotective and antiproliferative effects on the skin, while UV radiation is a major environmental risk factor for melanoma. Thus, many natural metabolites and synthetic analogs of steroidal and secosteroidal molecules have been tested on various cancer cells and in animal models. In this study, we tested the anti-melanoma properties of several natural derivatives of vitamin D3 and L3 in comparison to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). A significant decrease in melanoma cell proliferation and cell mobility was observed for selected derivatives, with (25R)-27-hydroxyL3 showing the highest potency (lowest IC50) in A375 cells but lower potency in SK-MEL-28 cells, whereas the parent L3 failed to inhibit proliferation. The efficacy (% inhibition) by 1,24,25(OH)3D3 and 1,25(OH)2D3 were similar in both cell types. 1,25(OH)2D3 showed higher potency than 1,24,25(OH)3D3 in SK-MEL-28 cells, but lower potency in A375 cells for the inhibition of proliferation. As for 1,25(OH)2D3, but not the other derivatives tested, treatment of melanoma cells with 1,24,25(OH)3D3 markedly increased the expression of CYP24A1, enhanced translocation of the vitamin D receptor (VDR) from the cytoplasm to the nucleus and also decreased the expression of the proliferation marker Ki67. The effects of the other compounds tested were weaker and occurred only under certain conditions. Our data indicate that 1,24,25(OH)3D3, which has undergone the first step in 1,25(OH)2D3 inactivation by being hydroxylated at C24, still shows anti-melanoma properties, displaying higher potency than 1,25(OH)2D3 in SK-MEL-28 cells. Furthermore, hydroxylation increases the potency of some of the lumisterol hydroxy-derivatives, as in contrast to L3, (25R)-27(OH)L3 effectively inhibits proliferation and migration of the human malignant melanoma cell line A375.

Melatonin Receptor Expression in Primary Uveal Melanoma

Melatonin, noted for its anti-cancer properties in various malignancies, including cutaneous melanoma, shows promise in Uveal melanoma (UM) treatment. This study aimed to evaluate melatonin receptor expression in primary UM and its association with UM-related mortality and prognostic factors. Immunohistochemical analysis of 47 primary UM tissues showed low expression of melatonin receptor 1A (MTNR1A) and melatonin receptor 1B (MTNR1B), with MTNR1A significantly higher in patients who succumbed to UM. Analysis of TCGA data from 80 UM patients revealed RNA expression for MTNR1A, retinoic acid-related orphan receptor alpha (RORα), and N-ribosyldihydronicotinamide:quinone oxidoreductase (NQO2), but not MTNR1B or G protein-coupled receptor 50 (GPR50). Higher MTNR1A RNA levels were observed in patients with a BRCA1 Associated Protein 1 (BAP1) mutation, and higher NQO2 RNA levels were noted in patients with the epithelioid tumor cell type. However, Kaplan-Meier analysis did not show distinct survival probabilities based on receptor expression. This study concludes that UM clinical samples express melatonin receptors, suggesting a potential mechanism for melatonin's anti-cancer effects. Despite finding higher MTNR1A expression in patients who died of UM, no survival differences were observed.

Thin Amelanotic and Hypomelanotic Melanoma: Clinicopathological and Dermoscopic Features

Background and Objectives: Amelanotic/hypomelanotic melanomas (AHMs) account for 2-8% of all cutaneous melanomas. Due to their clinical appearance and the lack of specific dermoscopic indicators, AHMs are challenging to diagnose, particularly in thinner cutaneous lesions. The aim of our study was to evaluate the clinicopathological and dermoscopic features of thin AHMs. Identifying the baseline clinical-pathological features and dermoscopic aspects of thin AHMs is crucial to better understand this entity. Materials and Methods: We divided the AHM cohort into two groups based on Breslow thickness: thin (≤1.00 mm) and thick (>1.00 mm). This stratification helped identify any significant clinicopathological differences between the groups. For dermoscopic analysis, we employed the "pattern analysis" approach, which involves a simultaneous and subjective assessment of different criteria. Results: Out of the 2.800 melanomas analyzed for Breslow thickness, 153 were identified as AHMs. Among these, 65 patients presented with thin AHMs and 88 with thick AHMs. Red hair color and phototype II were more prevalent in patients with thin AHMs. The trunk was the most common anatomic site for thin AHMs. Patients with thin AHMs showed a higher number of multiple melanomas. Dermoscopic analysis revealed no significant difference between thin AHMs and thick AHMs, except for a more frequent occurrence of residual reticulum in thin AHMs. Conclusions: Thin AHMs typically affect individuals with lower phototypes and red hair color. These aspects can be related to the higher presence of pheomelanin, which provides limited protection against sun damage. This also correlates with the fact that the trunk, a site commonly exposed to intermittent sun exposure, is the primary anatomical location for thin AHMs. Multiple primary melanomas are more common in patients with thin AHMs, likely due to an intrinsic predisposition as well as greater periodic dermatologic follow-ups in this class of patients. Apart from the presence of residual reticulum, no other significant dermoscopic differences were observed, complicating the differential diagnosis between thin and thick AHMs based on dermoscopy alone.