Search Results (345)

Uveal melanoma is a melanocyte-derived malignancy of the eye with a high propensity for liver metastasis. Metastatic uveal melanoma is associated with high mortality and is poorly responsive to currently available therapies. Most uveal melanoma cases are driven by activating mutations in GNAQ and GNA11 genes, which convey oncogenic signaling through the mitogen-activated protein kinase (MAPK) pathway. Despite promising early results, safe doses of pharmacological inhibitors of the MAPK cascade failed to effectively control uveal melanoma in human trials. Considering the role of the RAC/PAK signaling axis as a co-regulator of the MAPK cascade, we set forth to investigate whether the efficacy of MAPK cascade inhibitors in pre-clinical models may be enhanced by direct inhibition of RAC and PAK proteins, or by indirect control of RAC via inhibition of guanylate biosynthesis. We observed that pharmacological inhibition of RAC, PAK and the key guanylate biosynthesis enzyme IMPDH significantly synergized with various inhibitors of the MAPK cascade in suppressing oncogenic signaling and the growth of uveal melanoma cells. In a mouse model, the addition of an IMPDH inhibitor to the treatment regimen significantly enhanced the ability of a MAPK cascade inhibitor to improve the survival of tumor-bearing animals. Targeting of the RAC/PAK axis provides a new strategy to increase the efficacy of targeted therapies in uveal melanoma. While RAC and PAK inhibitors are still undergoing pre-clinical development, clinically available inhibitors of IMPDH offer an opportunity to test the efficacy of this novel synergistic combination in the context of human disease. Full article

Tigecycline is an antibiotic belonging to the glycylcycline group of tetracyclines. Similar to other tetracycline derivatives, tigecycline is used in dermatology because of its bacteriostatic effect. Despite an overall favorable safety profile, tetracyclines are associated with a spectrum of cutaneous adverse effects, notably pigmentary disorders and phototoxic reactions. These dermatologic manifestations are presumed to result from tigecycline’s affinity for melanin biopolymer and its subsequent accumulation within the pigment-containing tissues. This study aimed to assess the impact of tigecycline on human normal skin cell homeostasis varied by melanin content. The study was conducted on HEMn-LP melanocytes and human dermal fibroblasts. The aim was achieved by determining the cell number, cell cycle, mitochondrial potential, and redox homeostasis and determining in silico the possibility of binding tigecycline to melanin biopolymers. In this study, it was shown that the cells more sensitive to tigecycline were HEMn-LP melanocytes. The obtained results showed that tigecycline decreased cell number in a dose-dependent manner. In addition, tigecycline was shown to reduce mitochondrial potential, increase the level of oxidized thiols, and increase ROS content in melanocytes, contributing to oxidative stress. In silico studies have shown that the binding of tigecycline to melanin may play a role in the induction of the toxic effects of tigecycline on the skin. Full article

The skin protects the body from damaging external stressors. The function of its outermost compartment, the epidermis, depends on high rates of protein synthesis and the production of protective molecules, both requiring amino acids as precursors. Conversely, the degradation of the epidermal barrier protein filaggrin releases free amino acids. Here, we review the epidermal amino acid metabolism, focusing on the metabolism of histidine, arginine and tyrosine, which are subjected to epidermal cell-specific control mechanisms. Histidine and arginine are metabolized by enzymes that are transcriptionally upregulated during terminal differentiation of keratinocytes, while tyrosine is specifically metabolized in melanocytes. Arginase converts arginine into ornithine and urea. While ornithine is decarboxylated to putrescine, a regulator of cellular proliferation, urea contributes to the moisturization of the skin surface. Histidase, also known as histidine ammonia lyase, converts histidine into urocanic acid (UCA) and ammonia. UCA is the main ultraviolet-absorbing molecule of the cornified layer of the epidermis, serving as a natural sunscreen of human skin. In melanocytes, tyrosinase initiates the polymerization of tyrosine to melanin, the main skin pigment that absorbs both visible light and ultraviolet radiation. The current evidence indicates that the metabolism of histidine, arginine, tyrosine and other amino acids critically influences normal and diseased skin. Full article

The expression of the Secreted Protein, Acidic and Rich in Cysteine (SPARC) gene in human melanoma increases during progression and is associated with epithelial-to-mesenchymal transition (EMT), which is a major determinant of metastasis in melanoma patients. However, the underlying molecular mechanisms that control SPARC expression in this context remain elusive. Herein, we identified Paired-related homeobox 1 (PRRX1), an EMT transcription factor, as a transcriptional activator of SPARC by direct binding to the promoter, thereby increasing its activity. Moreover, we found a strong positive correlation between SPARC and PRRX1 expression levels in clinical samples and cell lines. Furthermore, the switch from the proliferative/melanocytic phenotype toward the invasive/mesenchymal-like phenotype favors the expression of TCF7L2, a β-catenin cofactor, which, together with Sp1, binds to the proximal SPARC promoter, thereby bolstering protein expression. We also show that SPARC is a target of the miR-29 family, whose members are expressed in clinical melanoma samples and cell lines. Indeed, we found that miR-29b1~a expression is inversely correlated with SPARC levels, and it is significantly reduced in samples with a mesenchymal-like phenotype. Taken together, SPARC expression in melanoma cells relies on transcriptional activation by PRRX1/TCF7L2-Sp1 and is modulated through miR-29b1~a, which provides fine-tuning regulation over the switch between phenotypic states. Full article

Vitiligo is a chronic autoimmune dermatosis defined by selective melanocyte depletion and patchy depigmentation. IFN–γ-driven recruitment of autoreactive CD8⁺ T cells and induction of melanocyte apoptosis are central to its pathogenesis. Current therapies—including UVB phototherapy, tacrolimus, vitamin D3 analogs, and surgical methods—show limited and inconsistent efficacy. Emerging treatments like JAK inhibitors and WNT activators offer potential but require further validation. Translational progress is hindered by a lack of scalable human models. Here, we describe a tunable in vitro vitiligo platform in which human iPSC-derived melanocytes (iMc) are co-cultured with keratinocytes on Matrigel and exposed to precise graded IFN-γ concentrations. Our data revealed dose-dependent decreases in iMc survival and dendritic structure, faithfully mirroring derived melanocyte pathology. Leveraging this platform, we first evaluated the short-term efficacy of the ROCK inhibitor Y27632 under early-stage patient IFN-γ concentrations representative of patient lesional thresholds. At three days, Y27632 significantly upregulated adhesion molecules E-cadherin and DDR1, and two central factors—ET1 and bFGF. Importantly, ROCK inhibition reversed dendritic retraction and improved overall viability of iMc-keratinocytes. These findings position ROCK blockade as a promising adjunctive strategy and establish a pre-clinical platform for evaluating combination therapies for durable pigment restoration. Full article

Skin dullness contributes to a fatigued and aged appearance, often exceeding one’s biological age. It is a common dermatological concern influenced by aging and poor lifestyle habits, regardless of ethnicity or age. This study aimed to examine advanced glycation end products (AGEs) and their receptor (receptor for AGEs [RAGE]) as contributing factors to skin dullness. AGEs themselves have a yellowish hue, contributing to “yellow dullness.” Additionally, AGE–RAGE signaling promotes melanin production in melanocytes and impairs keratinocyte differentiation as a result of inflammation. Therefore, regulating the AGE–RAGE interaction may help reduce skin dullness. Through screening various natural ingredients, we found that peony root extract (PRE) inhibits AGE formation and blocks AGE–RAGE binding. Furthermore, the presence of PRE leads to the suppression of AGE-induced melanin production in melanocytes and the restoration of impaired keratinocyte differentiation in glycated basement membrane components. In a human clinical study, topical application of a 1% PRE-containing lotion for 2 weeks significantly reduced melanin content, with a trend toward decreased AGE accumulation and visible spots on the cheeks. These findings support the potential of PRE as a multifunctional cosmetic ingredient that comprehensively addresses skin dullness by modulating the AGE–RAGE interaction. Full article

Background/Objectives: Cutaneous melanoma is one of the aggressive forms of skin cancer originating from melanocytes. The high incidence of melanoma metastasis continues to rise, partly due to the complex nature of the molecular mechanisms driving its progression. While melanomas generally arise from melanocytes, we investigated whether aberrant keratinocyte differentiation pathways—like cornified envelope formation—discriminate primary melanoma from metastatic melanoma, revealing novel biomarkers in progression. Methods: In the present study, we retrieved four datasets (GSE15605, GSE46517, GSE8401, and GSE7553) associated with primary and metastatic melanoma tissues and identified differentially expressed genes (DEGs). Thereafter, an integrated meta-analysis and functional enrichment analysis of the DEGs were performed to evaluate the molecular mechanisms involved in melanoma metastasis, such as immune cell deconvolution and protein-protein interaction (PPI) network construction. Hub genes were identified based on four topological methods, including ‘Betweenness’, ‘MCC’, ‘Degree’, and ‘Bottleneck’. We validated the findings using the TCGA-SKCM cohort. Drug-gene interactions were evaluated using the DGIdb, whereas structural druggability was assessed using the ProteinPlus and AlphaFold databases. Results: We identified a total of eleven hub genes associated with melanoma progression. These included members of the keratin gene family (e.g., KRT5, KRT6A, KRT6B, etc.). Except for the gene CDH1, all the hub genes were downregulated in metastatic melanoma tissues. From a prognostic perspective, these hub genes were associated with poor prognosis (i.e., unfavorable). Using the Human Protein Atlas (HPA), immunohistochemistry evaluation revealed mostly undetected levels in metastatic melanoma. Additionally, the cornified envelope formation was the most enriched pathway, with a gene ratio of 17/33. The tumor microenvironment (TME) of metastatic melanomas was predominantly enriched in NK cell–associated signatures. Finally, several hub genes demonstrated favorable druggable potential for immunotherapy. Conclusions: Through integrated meta-analysis, this study identifies transcriptional, immunological, and structural pathways to melanoma metastasis and highlights keratin family genes as promising biomarkers for therapeutic targeting. Full article

Aldehyde dehydrogenase 2 (ALDH2) is a crucial detoxifying enzyme that eliminates toxic aldehydes. ALDH2 deficiency has been linked to various human diseases, including certain cancers. We have previously reported ALDH2 downregulation in human melanoma tissues. Here, we further investigated the biological significance of ALDH2 downregulation in this malignancy. Analysis of TCGA dataset revealed that low ALDH2 expression correlates with poorer survival in metastatic melanoma. Examination of human metastatic melanoma cell lines confirmed that most had ALDH2 downregulation (ALDH2-low) compared to primary melanocytes. In contrast, a small subset of metastatic melanoma cell lines exhibited normal ALDH2 levels (ALDH2-normal). CRISPR/Cas9-mediated ALDH2 knockout in ALDH2-normal A375 cells promoted tumor growth and MAPK/ERK activation. Given the pivotal role of MAPK/ERK signaling in melanoma and cellular response to acetaldehyde, we compared A375 with ALDH2-low SK-MEL-28 and 1205Lu cells. ALDH2-low cells were intrinsically resistant to BRAF and MEK inhibitors, whereas A375 cells were not. However, A375 cells acquired resistance upon ALDH2 knockout. Furthermore, melanoma cells with acquired resistance to these inhibitors displayed further ALDH2 downregulation. Our findings indicate that ALDH2 downregulation contributes to melanoma progression and therapy resistance in BRAF-mutated human metastatic melanoma cells, highlighting ALDH2 as a potential prognostic marker and therapeutic target in metastatic melanoma. Full article

Background: Melanoma is a malignant tumor of melanocytes with an increasing incidence worldwide. Plant-based products are rich in bioactive compounds, offering low toxicity and accessible alternatives for melanoma treatment. A biotechnological approach to obtaining plant-derived produce ensures continuous and high-yield production of medicinally valuable biomass. Objectives: This study aimed to induce and optimize the growth of homogenous callus cultures of Kickxia elatine (L.) Dumort., consequently established a cell suspension culture with a high biomass growth rate, analyzed the phytochemical compositions, and assessed the cytotoxic activity against melanoma cells. Methods/Results: Callus cultures were induced under controlled in vitro conditions on Murashige and Skoog (MS) media supplemented with 2.0 mg L⁻¹ Dicamba and 2.0 mg L⁻¹ 2,4-Dichlorophenoxyacetic acid. The selected callus lines exhibited a high growth index (351.71% ± 27.77) and showed a homogeneous morphology, beige colour, and had friable and watery characteristics. A combination of auxin and cytokinin was found to enhance biomass production significantly. Phytochemical investigations putatively annotated major compounds, including benzoic acid derivatives, phenolic glycosides, phenylpropanoic acids, hydroxycinnamic acid derivatives, and tyrosol derivatives. Methanolic extract (KE-Ex) and 40% methanolic fraction (KE-40Fr) were prepared and tested for cytotoxicity against human fibroblast (MRC-5) and melanoma (MeWo) cell lines using direct cell counting and MTT assay. The crude extract exhibited the strongest cytotoxicity effect on MeWo cells, with IC₅₀ values of 125 ± 8 µg mL⁻¹ after 48 h and 117 ± 7 µg mL⁻¹ after 72 h of treatment. Conclusions: The extract demonstrated a time- and dose-dependent cytotoxic effect, making it a potential candidate for melanoma treatment. Full article

Human cutaneous malignant melanoma is a skin cancer that develops from melanocytes, the cells specialised in the production of eu- and pheomelanin. A growing body of evidence suggests that pheomelanin in particular is involved in melanoma development. The aim of this study was to develop a new method enabling the determination of the pheomelanin in formalin-fixed paraffin-embedded (FFPE) tissue specimens of human nodular (NM) and superficial spreading (SSM) melanomas. The pheomelanin level was evaluated in a small amount of material obtained from FFPE melanoma samples (less than 1 mg), using a multi-step procedure of paraffin removal, tissue rehydration, and homogenisation, omitting the melanin isolation step. The obtained product was studied for pheomelanin content using the Py-GC/MS/MS method operating in a multiple reaction monitoring (MRM) mode. The results of our research confirmed the presence of all the pheomelanin markers in the FFPE human melanoma specimens and showed that the tissues analysed contained different amounts of pheomelanin isomers (5-S-cysteinylDOPA and 2-S-cysteinylDOPA). The developed Py-GC/MS/MS procedure enables sensitive quantification of pheomelanin in FFPE human melanoma samples, facilitating broader studies on its role in melanoma development and progression. This method opens new avenues for investigating pheomelanin’s involvement in melanoma malignancy. Full article

Background/Objectives: Telomerase plays a vital role in preserving telomere length, a key process in cancer development. Human telomerase reverse transcriptase (hTERT) is commonly expressed in various cancers, including melanoma. This study evaluated hTERT protein expression in melanomas compared to melanocytic nevi. Methods: In total, we examined 75 melanocytic lesions using TERT immunohistochemistry on paraffin-embedded tissues; 36 of them were thin melanomas (Breslow index ≤ 1 mm) and 39 melanocytic nevi. Results: The TERT expression differed with statistical significance between the two studied groups, melanomas and melanocytic nevi, in all three aspects examined: percentage of staining (p = 0.006), intensity of staining (p = 0.035), and localisation of staining (p = 0.012). Three quarters of the melanomas stained in over 50% of the cells at cytoplasmic level, 52.78% of the melanomas exhibited an intensity of 3+, and all melanomas were stained at the cytoplasmic level, except for the two negative cases. The values were lower in the melanocytic nevi group. Still, the diagnostic values were relatively low (sensitivity = 75%, specificity = 58.97%, PPV = 62.79%, NPV = 71.88%, and ACC = 66.67%). Conclusions: TERT immunohistochemistry differed between the two studied groups; however, the diagnostic utility is low in our study. Combining with other immunohistochemical antibodies would probably increase the diagnostic power. Full article

Although melanin is viewed as a natural sunscreen that protects pigmented cells against the adverse effects of solar radiation, recent studies have demonstrated that, under certain conditions, the pigment can actually contribute to light-induced oxidative damage of the cells. However, the main issue with such studies is finding natural pigments without photooxidative modifications. Recently, melanin obtained from melanocytes, generated from human induced pluripotent stem cells (hiPSC-Mel), was suggested as a promising source of the pigment without significant photooxidation. Although different studies have demonstrated the feasibility of the above-mentioned technique to obtain melanin-producing cells, no thorough analysis of the physicochemical properties of the pigment has been performed. To address this issue, we examined the key physicochemical parameters, including the aerobic photoreactivity of melanin isolated from hiPSC-Mel and compared them with those of melanin from other known sources of the pigment, such as bovine retinal pigment epithelium (bRPE) and phototype V (PT-V) hair. Electron paramagnetic resonance (EPR) spectroscopy, dynamic light scattering, UV–Vis absorption and HPLC analysis of melanin degradation products were used. The ability of the examined melanins to photogenerate reactive oxygen species was determined by employing EPR oximetry, EPR spin-trapping and time-resolved singlet oxygen phosphorescence. Although the results of such measurements demonstrated that melanin obtained from hiPSC-Mel exhibited the physicochemical properties typical for eumelanin, a contribution from pheomelanin with a substantial presence of benzothiazine subunits, was also evident. Importantly, the hiPSC-Mel pigment had significantly lower photoreactivity compared to bRPE melanin and PT-V hair melanin. Our findings indicate that hiPSC-Mel could be an excellent source of high-quality pigment for photoprotection studies. Full article

Background/Objectives: This study aims to investigate the effects of 5,7-dihydroxy-4-methylcoumarin (5,7D-4MC) on melanogenesis in B16F10 murine melanoma cells and to evaluate its safety as a potential ingredient for functional cosmetics and therapeutic agents targeting pigmentation-related disorders. Method: The cytotoxicity of 5,7D-4MC was assessed using an MTT assay, and melanin content and tyrosinase activity were measured at different concentrations (25, 50, 100 µM). Western blot analyses were conducted to evaluate the expression of key melanogenesis-related proteins (TYR, TRP-1, TRP-2, and MITF) and to investigate the regulation of major signaling pathways, including PKA/cAMP, GSK3β, and PI3K/AKT. Additionally, a human primary skin irritation test was performed on 32 participants to assess the dermatological safety of 5,7D-4MC. Results: 5,7D-4MC did not affect cell viability at concentrations below 100 µM and significantly promoted melanin production in a dose-dependent manner. Tyrosinase activity and the expression levels of melanogenic proteins increased significantly following 5,7D-4MC treatment. PKA and GSK3β pathways were activated, while the PI3K/AKT pathway was downregulated. The skin irritation test showed that 5,7D-4MC exhibited low irritation potential at concentrations of 50 µM and 100 µM. Conclusions: 5,7D-4MC enhances melanogenesis and demonstrates low skin irritation, making it a promising candidate for therapeutic applications in treating hypopigmentation disorders, such as vitiligo, as well as a functional cosmetic ingredient. However, further studies involving human melanocytes and clinical trials are required to validate their efficacy. Full article

Background/Objectives: Oleuropein (OLP), the key bioactive in olive leaf extracts, has demonstrated various biological benefits. We previously reported on the pro-melanogenic action with increased dendricity of a patented olive leaf extract (Benolea^®) that was standardized to 16–24% OLP. In this study, purified OLP was evaluated to identify if it might be the bioactive responsible for the stimulating effects on melanocytes. Moreover, previous studies on OLP have never reported the effects on melanocyte dendricity or melanin export in the medium. Methods: Herein, the effect of OLP on melanogenesis was first evaluated using the B16F10 cell model and validated using the physiological model of normal human melanocytes from Caucasian (lightly pigmented; LP) and Asian (moderately pigmented; MP) skin. The effects of OLP on melanin export in LP and MP cells were indirectly evaluated by dendricity indices. Results: OLP lowered the intracellular melanin content in B16F10 cells by 26.36%, 24.48%, and 27.71% at 100, 150, and 200 µg/mL (all p < 0.01), respectively, with no effect on the intracellular melanin contents of LP or MP cells. OLP treatment did not influence tyrosinase activity in B16F10 cells or MP cells but significantly enhanced the activity in LP cells. The measurement of extracellular melanin showed significantly higher levels for all three cells, although the levels were considerably higher in MP cells, after the adjustment for OLP autoxidation observed in the cell-free system, which caused melanin-like brown coloration. Furthermore, OLP induced morphological alterations of extended dendrites of B16F10 cells that were retained in LP and MP cells. The quantitation of the dendricity of cells treated with OLP at 200 μg/mL revealed that the total dendrite length was increased by 35.24% (p < 0.05) in LP cells and by 58.45% (p < 0.001) in MP cells without any change in the dendrite number. Conclusions: This is the first study to demonstrate the novel finding that OLP possesses a hitherto unreported unique capacity to stimulate melanocyte dendricity, hence establishing the efficacy for use in increasing human pigmentation. Our findings show significance, with a potential application of the compound OLP for addressing human hypopigmentation disorders in clinical settings or for cosmetic uses related to sunless tanning. Full article

Melanoma is one of the most lethal cancers originating from melanocytes. Its incidence and mortality have been rising rapidly for several decades and have posed a serious threat to human health. Current melanoma treatments are hindered by the scope of application, low efficiency, high cost, and toxic side effects. Due to their affordability and minimal side effects, natural bioactive compounds derived from plants are promising candidates for melanoma treatment. This study aims to delve into the isolation, purification, and characterization of potato proteins and to explore their potential in melanoma treatment. Two potato proteins, patatin PP-1 and aspartate protease inhibitor PP-2, were isolated and purified by a newly developed method in this work, and their physicochemical properties were systematically characterized. Both potato proteins showed great antiproliferative activities and migration inhibition effects on melanoma cells. Meanwhile, Western blotting results illustrated that they could induce endogenous cell apoptosis by regulating the Bax/Bcl-2 pathway. Notably, aspartate protease inhibitor PP-2 demonstrated the best performance in inhibiting the growth and migration of melanoma cells, which might be attributed to the combined effect of its significant antioxidative activity and the inhibition effect of certain necessary protease activities in melanoma. This study provides valuable insights for developing nutraceuticals and therapeutic strategies against melanoma, which can lead to breakthroughs in melanoma treatment. Full article