Transplantable Melanomas in Hamsters and Gerbils as Models for Human Melanoma. Sensitization in Melanoma Radiotherapy-From Animal Models to Clinical Trials

Vaginal Mucosal Melanoma Cell Activation in Response to Photon or Carbon Ion Irradiation

Purpose

Primary gynecological melanomas are uncommon with lower survival rates compared to cutaneous melanomas. Although melanocytes have been identified in a variety of mucosal membranes, little is known about their interactions or roles inside the mucosa layer. Melanin is a common pigment in nature and is endowed with several peculiar chemical, paramagnetic, and semiconductive characteristics. One of its latest explored functions is its interaction with ionizing radiation as a protective mechanism as well as its implication in the metastatic cascade of tumor cells.

Materials and Methods

In this work, we analyzed in vitro the effects of different doses of photon and carbon ion irradiation on dendrite formation, pigmentation, migration, and invasion abilities of human mucosal melanoma cells of the vagina. We evaluated the morphology and melanin production of HMV-II cells exposed to photon and carbon ion beams with single doses between 0.5 and 10 Gy.

Results

Our results showed that irradiation induces dendrite formation or elongation and pigmentation in HMV-II cells in a dose-type-dependent and radiation-type-dependent way but also a decrease in cell motility.

Conclusion

The present study describes for the first time an induction of dendritic formation, melanin production, and alterations in migration and invasion abilities by low-linear energy transfer and high-linear energy transfer radiation in human mucosal melanoma cells, suggesting a radioprotective response to further possible exposures increasing the radioresistance of these cells.

Reconnoitring signaling pathways and exploiting innovative approaches tailoring multifaceted therapies for skin cancer

Nowadays, skin cancer is widespread just like a varied malignant cancer which can cause serious health issues. Skin cancer, which encompasses malignant melanoma, basal cell carcinoma, and squamous cell carcinoma, is a prevalent form of cancer among humans. Due to its broad prevalence, financial burden, mortality rates, and cosmetic effects, it is a major public health issue. Skin cancer treatment involves surgery, chemotherapy, and radiation. Recently, personalized treatment in the fields of targeted therapies and precision medicine has been shown to diagnose early detection of every individual tumor by knowing their genetic and molecular characteristics. To target the molecular pathways responsible for tumor growth and reduce the damage to healthy tissue, new targeted therapies have emerged for melanoma, basal cell carcinoma, and squamous cell carcinoma. B-raf serine/threonine kinase (BRAF) and mitogen-activated protein kinase (MEK) inhibitors, immune checkpoint inhibitors, and precision medications have strong response rates to improve patient survival. Targeted therapeutics like nanocarriers have shown promising results by reducing skin irritation and protecting encapsulated therapeutics. These formulations have been shown to improve the transdermal permeability of anticancer drugs. The consideration of employing physical techniques to enhance the permeation of nanocarriers warrants attention to augment the dermal permeation of anticancer agents and facilitate targeted drug delivery within neoplastic cells. Targeted therapies face obstacles like resistance mechanisms and treatment strategy monitoring. Taken together, this review delves into the basic mechanisms of skin cancer, current treatment methods, drug resistance processes, and nano-based targeted techniques for cancer treatment. It will also delineate the challenges and perspectives in pre-clinical and clinical contexts.

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

Melanoma, originating through malignant transformation of melanin-producing melanocytes, is a formidable malignancy, characterized by local invasiveness, recurrence, early metastasis, resistance to therapy, and a high mortality rate. This review discusses etiologic and risk factors for melanoma, diagnostic and prognostic tools, including recent advances in molecular biology, omics, and bioinformatics, and provides an overview of its therapy. Since the incidence of melanoma is rising and mortality remains unacceptably high, we discuss its inherent properties, including melanogenesis, that make this disease resilient to treatment and propose to use AI to solve the above complex and multidimensional problems. We provide an overview on vitamin D and its anticancerogenic properties, and report recent advances in this field that can provide solutions for the prevention and/or therapy of melanoma. Experimental papers and clinicopathological studies on the role of vitamin D status and signaling pathways initiated by its active metabolites in melanoma prognosis and therapy are reviewed. We conclude that vitamin D signaling, defined by specific nuclear receptors and selective activation by specific vitamin D hydroxyderivatives, can provide a benefit for new or existing therapeutic approaches. We propose to target vitamin D signaling with the use of computational biology and AI tools to provide a solution to the melanoma problem.

Unaddressed Challenges in the Treatment of Cutaneous Melanoma?

Background and Objectives: While the management of noninvasive cutaneous melanoma (CM) is typically limited to a secondary excision to reduce recurrence risk and periodic follow-up, treating patients with advanced melanoma presents ongoing challenges. Materials and Methods: This review provides a comprehensive examination of both established and emerging pharmacologic strategies for advanced CM management, offering an up-to-date insight into the current therapeutic milieu. The dynamic landscape of advanced CM treatment is explored, highlighting the efficacy of immune checkpoint inhibitors and targeted therapies, either in monotherapy or combination regimens. Additionally, ongoing investigations into novel treatment modalities are thoroughly discussed, reflecting the evolving nature of melanoma management. Results: The therapeutic landscape for melanoma management is undergoing significant transformation. Although various treatment modalities exist, there remains a critical need for novel therapies, particularly for certain stages of melanoma or cases resistant to current options. Conclusions: Consequently, further studies are warranted to identify new treatment avenues and optimize the utilization of existing drugs.

Paradoxical Radiosensitizing Effect of Carnosic Acid on B16F10 Metastatic Melanoma Cells: A New Treatment Strategy

Carnosic acid (CA) is a phenolic diterpene characterized by its high antioxidant activity; it is used in industrial, cosmetic, and nutritional applications. We evaluated the radioprotective capacity of CA on cells directly exposed to X-rays and non-irradiated cells that received signals from X-ray treated cells (radiation induced bystander effect, RIBE). The genoprotective capacity was studied by in vivo and in vitro micronucleus assays. Radioprotective capacity was evaluated by clonogenic cell survival, MTT, apoptosis and intracellular glutathione assays comparing radiosensitive cells (human prostate epithelium, PNT2) with radioresistant cells (murine metastatic melanoma, B16F10). CA was found to exhibit a genoprotective capacity in cells exposed to radiation (p < 0.001) and in RIBE (p < 0.01). In PNT2 cells, considered as normal cells in our study, CA achieved 97% cell survival after exposure to 20 Gy of X-rays, eliminating 67% of radiation-induced cell death (p < 0.001), decreasing apoptosis (p < 0.001), and increasing the GSH/GSSH ratio (p < 0.01). However, the administration of CA to B16F10 cells decreased cell survival by 32%, increased cell death by 200% (p < 0.001) compared to irradiated cells, and increased cell death by 100% (p < 0.001) in RIBE bystander cells (p < 0.01). Furthermore, it increased apoptosis (p < 0.001) and decreased the GSH/GSSG ratio (p < 0.01), expressing a paradoxical radiosensitizing effect in these cells. Knowing the potential mechanisms of action of substances such as CA could help to create new applications that would protect healthy cells and exclusively damage neoplastic cells, thus presenting a new desirable strategy for cancer patients in need of radiotherapy.

Amelanotic Uveal Melanomas Evaluated by Indirect Ophthalmoscopy Reveal Better Long-Term Prognosis Than Pigmented Primary Tumours-A Single Centre Experience

(1) Background: There is a constant search for new prognostic factors that would allow us to accurately determine the prognosis, select the type of treatment, and monitor the patient diagnosed with uveal melanoma in a minimally invasive and easily accessible way. Therefore, we decided to evaluate the prognostic role of its pigmentation in a clinical assessment. (2) Methods: The pigmentation of 154 uveal melanomas was assessed by indirect ophthalmoscopy. Two groups of tumours were identified: amelanotic and pigmented. The statistical relationships between these two groups and clinical, pathological parameters and the long-term survival rate were analyzed. (3) Results: There were 16.9% amelanotic tumours among all and they occurred in younger patients (p = 0.022). In pigmented melanomas, unfavourable prognostic features such as: epithelioid cells (p = 0.0013), extrascleral extension (p = 0.027), macronucleoli (p = 0.0065), and the absence of BAP1 expression (p = 0.029) were statistically more frequently observed. Kaplan−Meier analysis demonstrated significantly better overall (p = 0.017) and disease-free (p < 0.001) survival rates for patients with amelanotic tumours. However, this relationship was statistically significant for lower stage tumours (AJCC stage II), and was not present in larger and more advanced stages (AJCC stage III). (4) Conclusions: The results obtained suggested that the presence of pigmentation in uveal melanoma by indirect ophthalmoscopy was associated with a worse prognosis, compared to amelanotic lesions. These findings could be useful in the choice of therapeutic and follow-up options in the future.

Development and Validation of a Novel Survival Model for Cutaneous Melanoma Based on Necroptosis-Related Genes

Background

Necroptosis is crucial for organismal development and pathogenesis. To date, the role of necroptosis in skin cutaneous melanoma (SKCM) is yet unveiled. In addition, the part of melanin pigmentation was largely neglected in the bioinformatic analysis. In this study, we aimed to construct a novel prognostic model based on necroptosis-related genes and analysis the pigmentation phenotype of patients to provide clinically actionable information for SKCM patients.

Methods

We downloaded the SKCM data from the TCGA and GEO databases in this study and identified the differently expressed and prognostic necroptosis-related genes. Patients’ pigmentation phenotype was evaluated by the GSVA method. Then, using Lasso and Cox regression analysis, a novel prognostic model was constructed based on the intersected genes. The risk score was calculated and the patients were divided into two groups. The survival differences between the two groups were compared using Kaplan-Meier analysis. The ROC analysis was performed and the area under curves was calculated to evaluate the prediction performances of the model. Then, the GO, KEGG and GSEA analyses were performed to elucidate the underlying mechanisms. Differences in the tumor microenvironment, patients’ response to immune checkpoint inhibitors (ICIs) and pigmentation phenotype were analyzed. In order to validate the mRNA expression levels of the selected genes, quantitative real-time PCR (qRT-PCR) was performed.

Results

Altogether, a novel prognostic model based on four genes (BOK, CD14, CYLD and FASLG) was constructed, and patients were classified into high and low-risk groups based on the median risk score. Low-risk group patients showed better survival status. The model showed high accuracy in the training and the validation cohort. Pathway and functional enrichment analysis indicated that immune-related pathways were differently activated in the two groups. In addition, immune cells infiltration patterns and sensitivity of ICIs showed a significant difference between patients from two risk groups. The pigmentation score was positively related to the risk score in pigmentation phenotype analysis.

Conclusion

In conclusion, this study established a novel prognostic model based on necroptosis-related genes and revealed the possible connections between necroptosis and melanin pigmentation. It is expected to provide a reference for clinical treatment.

Melanoma, Melanin, and Melanogenesis: The Yin and Yang Relationship

Melanin pigment plays a critical role in the protection against the harmful effects of ultraviolet radiation and other environmental stressors. It is produced by the enzymatic transformation of L-tyrosine to dopaquinone and subsequent chemical and biochemical reactions resulting in the formation of various 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI) oligomers-main constituents of eumelanin, and benzothiazine and benzothiazole units of pheomelanin. The biosynthesis of melanin is regulated by sun exposure and by many hormonal factors at the tissue, cellular, and subcellular levels. While the presence of melanin protects against the development of skin cancers including cutaneous melanoma, its presence may be necessary for the malignant transformation of melanocytes. This shows a complex role of melanogenesis in melanoma development defined by chemical properties of melanin and the nature of generating pathways such as eu- and pheomelanogenesis. While eumelanin is believed to provide radioprotection and photoprotection by acting as an efficient antioxidant and sunscreen, pheomelanin, being less photostable, can generate mutagenic environment after exposure to the short-wavelength UVR. Melanogenesis by itself and its highly reactive intermediates show cytotoxic, genotoxic, and mutagenic activities, and it can stimulate glycolysis and hypoxia-inducible factor 1-alpha (HIF-1α) activation, which, combined with their immunosuppressive effects, can lead to melanoma progression and resistance to immunotherapy. On the other hand, melanogenesis-related proteins can be a target for immunotherapy. Interestingly, clinicopathological analyses on advanced melanomas have shown a negative correlation between tumor pigmentation and diseases outcome as defined by overall survival and disease-free time. This indicates a "Yin and Yang" role for melanin and active melanogenesis in melanoma development, progression, and therapy. Furthermore, based on the clinical, experimental data and diverse effects of melanogenesis, we propose that inhibition of melanogenesis in advanced melanotic melanoma represents a realistic adjuvant strategy to enhance immuno-, radio-, and chemotherapy.

Tyrosine-Dependent Phenotype Switching Occurs Early in Many Primary Melanoma Cultures Limiting Their Translational Value

The use of patient-derived primary cell cultures in cancer preclinical assays, including drug screens and genotoxic studies, has increased in recent years. However, their translational value is constrained by several limitations, including variability that can be caused by the culture conditions. Here, we show that the medium composition commonly used to propagate primary melanoma cultures has limited their representability of their tumor of origin and their cellular plasticity, and modified their sensitivity to therapy. Indeed, we established and compared cultures from different melanoma patients propagated in parallel in low-tyrosine (Ham's F10) or in high-tyrosine (Ham's F10 supplemented with tyrosine or RPMI1640 or DMEM) media. Tyrosine is the precursor of melanin biosynthesis, a process particularly active in differentiated melanocytes and melanoma cells. Unexpectedly, we found that the high tyrosine concentrations promoted an early phenotypic drift towards either a mesenchymal-like or senescence-like phenotype, and prevented the establishment of cultures of melanoma cells harboring differentiated features, which we show are frequently present in human clinical biopsies. Moreover, the invasive phenotype emerging in these culture conditions appeared irreversible and, as expected, associated with intrinsic resistance to MAPKi. In sharp contrast, differentiated melanoma cell cultures retained their phenotypes upon propagation in low-tyrosine medium, and importantly their phenotypic plasticity, a key hallmark of melanoma cells. Altogether, our findings underline the importance of culturing melanoma cells in low-tyrosine-containing medium in order to preserve their phenotypic identity of origin and cellular plasticity.

The Challenging Melanoma Landscape: From Early Drug Discovery to Clinical Approval

Melanoma is recognized as the most dangerous type of skin cancer, with high mortality and resistance to currently used treatments. To overcome the limitations of the available therapeutic options, the discovery and development of new, more effective, and safer therapies is required. In this review, the different research steps involved in the process of antimelanoma drug evaluation and selection are explored, including information regarding in silico, in vitro, and in vivo experiments, as well as clinical trial phases. Details are given about the most used cell lines and assays to perform both two- and three-dimensional in vitro screening of drug candidates towards melanoma. For in vivo studies, murine models are, undoubtedly, the most widely used for assessing the therapeutic potential of new compounds and to study the underlying mechanisms of action. Here, the main melanoma murine models are described as well as other animal species. A section is dedicated to ongoing clinical studies, demonstrating the wide interest and successful efforts devoted to melanoma therapy, in particular at advanced stages of the disease, and a final section includes some considerations regarding approval for marketing by regulatory agencies. Overall, considerable commitment is being directed to the continuous development of optimized experimental models, important for the understanding of melanoma biology and for the evaluation and validation of novel therapeutic strategies.

Melanization as unfavorable factor in amelanotic melanoma cell biology

The biology of three amelanotic melanoma cell lines (Ab, B16F10, and A375) of different species origin was analyzed during in vitro induced melanization in these cells. Melanin production was induced by DMEM medium characterized by a high level of L-tyrosine (a basic amino acid for melanogenesis). The biodiversity of amelanotic melanoma cells was confirmed by their different responses to melanogenesis induction; Ab hamster melanomas underwent intensive melanization, mouse B16F10 darkened slightly, while human A375 cells did not show any change in melanin content. Highly melanized Ab cells entered a cell death pathway, while slight melanization did not influence cell biology in a significant way. The rapid and high melanization of Ab cells induced apoptosis documented by phosphatidylserine externalization, caspase activation, and mitochondrial energetic state decrease. Melanoma cell type, culture medium, and time of incubation should be taken into consideration during amelanotic melanoma cell culture in vitro. L-tyrosine, as a concentration-dependent factor presented in the culture media, could stimulate some amelanotic melanoma cell lines (Ab, B16F10) to melanin production. The presence of melanin should be considered in the examination of antimelanoma compounds in vitro, because induction of melanin may interfere or be helpful in the treatment of amelanotic melanoma.

Pigmentation Levels Affect Melanoma Responses to Coriolus versicolor Extract and Play a Crucial Role in Melanoma-Mononuclear Cell Crosstalk

Melanoma, the malignancy originating from pigment-producing melanocytes, is the most aggressive form of skin cancer and has a poor prognosis once the disease starts to metastasize. The process of melanin synthesis generates an immunosuppressive and mutagenic environment, and can increase melanoma cell resistance to different treatment modalities, including chemo-, radio- or photodynamic therapy. Recently, we have shown that the presence of melanin pigment inhibits the melanoma cell response to bioactive components of Coriolus versicolor (CV) Chinese fungus. Herein, using the same human melanoma cell line in which the level of pigmentation can be controlled by the L-tyrosine concentration in culture medium, we tested the effect of suppression of melanogenesis on the melanoma cell response to CV extract and investigated the cell death pathway induced by fungus extract in sensitized melanoma cells. Our data showed that susceptibility to CV-induced melanoma cell death is significantly increased after cell depigmentation. To the best of our knowledge, we are the first to demonstrate that CV extract can induce RIPK1/RIPK3/MLKL-mediated necroptosis in depigmented melanoma cells. Moreover, using the co-culture system, we showed that inhibition of the tyrosinase activity in melanoma cells modulates cytokine expression in co-cultured mononuclear cells, indicating that depigmentation of melanoma cells may activate immune cells and thereby influence a host anticancer response.

Biophysical characterization of melanoma cell phenotype markers during metastatic progression

Melanoma is the most fatal form of skin cancer, with increasing prevalence worldwide. The most common melanoma genetic driver is mutation of the proto-oncogene serine/threonine kinase BRAF; thus, the inhibition of its MAP kinase pathway by specific inhibitors is a commonly applied therapy. However, many patients are resistant, or develop resistance to this type of monotherapy, and therefore combined therapies which target other signaling pathways through various molecular mechanisms are required. A possible strategy may involve targeting cellular energy metabolism, which has been recognized as crucial for cancer development and progression and which connects through glycolysis to cell surface glycan biosynthetic pathways. Protein glycosylation is a hallmark of more than 50% of the human proteome and it has been recognized that altered glycosylation occurs during the metastatic progression of melanoma cells which, in turn facilitates their migration. This review provides a description of recent advances in the search for factors able to remodel cell metabolism between glycolysis and oxidative phosphorylation, and of changes in specific markers and in the biophysical properties of cells during melanoma development from a nevus to metastasis. This development is accompanied by changes in the expression of surface glycans, with corresponding changes in ligand-receptor affinity, giving rise to structural features and viscoelastic parameters particularly well suited to study by label-free biophysical methods.

Effect of Rosmarinic Acid and Ionizing Radiation on Glutathione in Melanoma B16F10 Cells: A Translational Opportunity

To explain a paradoxical radiosensitizing effect of rosmarinic acid (RA) on the melanoma B16F10 cells, we analyzed the glutathione (GSH) intracellular production on this cell (traditionally considered radioresistant) in comparison with human prostate epithelial cells (PNT2) (considered to be radiosensitive). In PNT2 cells, the administration of RA increased the total GSH content during the first 3 h (p < 0.01) as well as increased the GSH/oxidized glutathione (GSSG) ratio in all irradiated cultures during all periods studied (1h and 3h) (p < 0.001), portraying an increase in the radioprotective capacity. However, in B16F10 cells, administration of RA had no effect on the total intracellular GSH levels, decreasing the GSH/GSSG ratio (p < 0.01); in addition, it caused a significant reduction in the GSH/GSSG ratio in irradiated cells (p < 0.001), an expression of radioinduced cell damage. In B16F10 cells, the administration of RA possibly activates the metabolic pathway of eumelanin synthesis that would consume intracellular GSH, thereby reducing its possible use as a protector against oxidative stress. The administration of this type of substance during radiotherapy could potentially protect healthy cells for which RA is a powerful radioprotector, and at the same time, cause significant damage to melanoma cells for which it could act as a radiosensitive agent.

Chloroacridine derivatives as potential anticancer agents which may act as tricarboxylic acid cycle enzyme inhibitors

PURPOSE

This paper concerns the cytotoxicity of 9-chloro-1-nitroacridine (1a) and 9-chloro-4-methyl-1-nitroacridine (1b) against two biologically different melanoma forms: melanotic and amelanotic. Melanomas are tumors characterized by high heterogeneity and poor susceptibility to chemotherapies. Among new analogs synthesized by us, compound 1b exhibited the highest anticancer potency. Because of that, in this study, we analyzed the mechanism of action for 1a and its 4-methylated derivative, 1b, against a pair of biological melanoma forms, with regard to proliferation, cell death mechanism and energetic state.

METHODS

Cytotoxicity was evaluated by XTT assay. Cell death was estimated by plasma membrane structure changes (phosphatidylserine externalization), caspase activation, and ROS presence. The energetic state of cells was estimated based on NAD and ATP levels, and the activity of tricarboxylic acid cycle enzymes (pyruvate dehydrogenase complex, aconitase, isocitrate dehydrogenase).

RESULTS

The chloroacridines affect biological forms of melanoma in different ways. Amelanotic (Ab) melanoma (with inhibited melanogenesis and higher malignancy) was particularly sensitive to the action of the chloroacridines. The Ab melanoma cells died through apoptosis and through death without caspase activation. Diminished activity of TAC enzymes was noticed among Ab melanoma cells together with ATP/NAD depletion, especially in the case of 1b.

CONCLUSION

Our data show that the biological forms of the tumors responded to 1a and its 4-methylated analog in different ways. 1a and 1b could be inducers of regulated melanoma cell death, especially the amelanotic form. Although the mechanism of the cell death is not fully understood, 1b may act by interfering with the TAC enzymes and blocking specific pathways leading to tumor growth. This could encourage further investigation of its anticancer activity, especially against the amelanotic form of melanoma.

Forty-year prognosis after plaque brachytherapy of uveal melanoma

In this study, the long-term patient survival after plaque brachytherapy of uveal melanoma is examined. All patients treated between 1980 and 1999 at a single institution were included (n = 677). 533 (79%) had deceased before the end of follow-up. The median follow-up for the 144 survivors was 25.4 years (SD 5.2). Uveal melanoma-related mortality was 18% by 5 years, 28% by 10 years, 32% by 15 years, 35% by 20 years, and 36% by 25 to 40 years. 172 of 209 (82%) uveal melanoma-related deaths occurred within the first decade after brachytherapy. Relative survival rates were 74% at 5 years, 64% at 10 years, 62% at 20 years, 83% at 30 years and ≥100% at 32 to 40 years. Tumor diameter and local recurrence were independent predictors of uveal melanoma-related mortality in multivariate Cox proportional hazards analysis. In conclusion, uveal melanoma has a high mortality rate and most uveal melanoma-related deaths occur in the first decade after treatment. Long-term survivors may have a survival advantage to individuals of the same sex and age from the general population.

Uveal melanoma pathobiology: Metastasis to the liver

Uveal melanoma (UM) is a type of intraocular tumor with a propensity to disseminate to the liver. Despite the identification of the early driver mutations during the development of the pathology, the process of UM metastasis is still not fully comprehended. A better understanding of the genetic, molecular, and environmental factors participating to its spread and metastatic outgrowth could provide additional approaches for UM treatment. In this review, we will discuss the advances made towards the understanding of the pathogenesis of metastatic UM, summarize the current and prospective treatments, and introduce some of the ongoing research in this field.

Relevance of Vitamin D in Melanoma Development, Progression and Therapy

Melanoma is one of the most lethal types of skin cancer, with a poor prognosis once the disease enters metastasis. The efficacy of currently available treatment schemes for advanced melanomas is low, expensive, and burdened by significant side-effects. Therefore, there is a need to develop new treatment options. Skin cells are able to activate vitamin D via classical and non-classical pathways. Vitamin D derivatives have anticancer properties which promote differentiation and inhibit proliferation. The role of systemic vitamin D in patients with melanoma is unclear as epidemiological studies are not definitive. In contrast, experimental data have clearly shown that vitamin D and its derivatives have anti-melanoma properties. Furthermore, molecular and clinicopathological studies have demonstrated a correlation between defects in vitamin D signaling and progression of melanoma and disease outcome. Therefore, adequate vitamin D signaling can play a role in the treatment of melanoma.

Verification of 5-Aminolevurinic Radiodynamic Therapy Using a Murine Melanoma Brain Metastasis Model

Melanoma is a highly aggressive cancer with a propensity for brain metastases. These can be treated by radiotherapy, but the radiation-resistant nature of melanoma makes the prognosis for melanoma patients with brain metastases poor. Previously, we demonstrated that treatment of mice with subcutaneous melanoma with 5-aminolevurinic acid (5-ALA) and X-rays in combination, (“radiodynamic therapy (RDT)”), instead of with 5-ALA and laser beams (“photodynamic therapy”), improved tumor suppression in vivo. Here, using the B16-Luc melanoma brain metastasis model, we demonstrate that 5-ALA RDT effectively treats brain metastasis. We also studied how 5-ALA RDT damages cells in vitro using a B16 melanoma culture. Cell culture preincubated with 5-ALA alone increased intracellular photosensitizer protoporphyrin IX. On X-ray irradiation, the cells enhanced their ∙OH radical generation, which subsequently induced γH2AX, a marker of DNA double-strand breaks in their nuclei, but decreased mitochondrial membrane potential. After two days, the cell cycle was arrested. When 5-ALA RDT was applied to the brain melanoma metastasis model in vivo, suppression of tumor growth was indicated. Therapeutic efficacy in melanoma treatment has recently been improved by molecular targeted drugs and immune checkpoint inhibitors. Treatment with these drugs is now expected to be combined with 5-ALA RDT to further improve therapeutic efficacy.

Coriolus versicolor-derived protein-bound polysaccharides trigger the caspase-independent cell death pathway in amelanotic but not melanotic melanoma cells

We have investigated the potential cell death mechanism promoted by Coriolus versicolor fungus-derived protein-bound polysaccharides (PBPs) in melanoma cells. Knowing that melanogenesis has the potential to affect the tumor behavior and melanoma therapy outcome, the cytotoxic effects of PBPs were evaluated in human SKMel-188 melanoma cell line, whose phenotype, amelanotic versus pigmented, depends on the concentration of melanin precursors in the culture medium. Our results showed that inhibitory effect of PBPs (100 and 200 μg/ml) towards melanoma cells is inversely associated with the pigmentation level. This cytotoxicity induced in nonpigmented melanoma cells by PBPs was caspase-independent; however, it was accompanied by an increased intracellular reactive oxygen species (ROS) generation. The ROS production was controlled by c-Jun N-terminal kinase (JNK) because SP600125, a JNK inhibitor, significantly reduced ROS generation and protected cells against PBPs-induced death. We also found that PBPs-induced lactate dehydrogenase release in amelanotic melanoma cells was abolished by co-treatment with receptor-interacting serine/threonine-protein kinase 1 inhibitor, implying engagement of this kinase in PBPs-induced death pathway. The results suggest that PBPs induce an alternative programmed cell death, regulated by receptor-interacting protein-1 and ROS and that this process is modified by melanin content in melanoma cells. These findings are remarkable when considering the use of commercially available Coriolus versicolor by patients who suffer from melanoma cancer.

Vitamin D receptors (VDR), hydroxylases CYP27B1 and CYP24A1 and retinoid-related orphan receptors (ROR) level in human uveal tract and ocular melanoma with different melanization levels

In recent years, a significant number of studies have investigated the preventive role of vitamin D in a number of different neoplasms. In this study, we analyze various components of the vitamin D signaling pathways in the human uveal tract and uveal melanoma, including analysis of the expression of vitamin D receptors (VDR), the activating and inactivating hydroxylases, respectively, CYP27B1 and CYP24A1, and the retinoic acid-related orphan receptors (ROR) α (RORα) and γ (RORγ) in these tissues. We further analyzed the expression of VDR, CYP27B1, CYP24A1, and ROR in relation to melanin levels, clinical stage and prognosis. Our study indicated that the uveal melanoma melanin level inversely correlated with VDR expression. We further showed that vitamin D is metabolized in uveal melanoma. This is significant because until now there has been no paper published, that would describe presence of VDR, hydroxylases CYP27B1 and CYP24A1, and RORα and RORγ in the human uveal tract and uveal melanomas. The outcomes of our research can contribute to the development of new diagnostic and therapeutic methods in uveal tract disorders, especially in uveal melanoma. The presented associations between vitamin D signaling elements and uveal melanoma in comparison to uveal tract encourage future clinical research with larger patients' population.

Vitamin D and Human Health

Vitamin D is currently one of the hottest topics in research and clinics, as well as in everyday life. Over the past decades, scientists gathered overwhelming evidence indicating that the observed global vitamin D deficiency not only has a negative impact on human skeletal system, but also facilitates development and progression of multiple disease of civilization, including cardiovascular diseases, diabetes, autoimmune disease, and cancer. This Special Issue, entitled “Vitamin D and Human Health”, summarizes recent advances in our understanding of pleiotropic activity of vitamin D in the form of eight comprehensive reviews. Furthermore, eight research papers provide new insight into vitamin D research and highlight new directions.

Radiotherapy as a New Player in Immuno-Oncology

Recent development in radiation biology has revealed potent immunogenic properties of radiotherapy in cancer treatments. However, antitumor immune effects of radiotherapy are limited by the concomitant induction of radiation-dependent immunosuppressive effects. In the growing era of immunotherapy, combining radiotherapy with immunomodulating agents has demonstrated enhancement of radiation-induced antitumor immune activation that correlated with improved treatment outcomes. Yet, how to optimally deliver combination therapy regarding dose-fractionation and timing of radiotherapy is largely unknown. Future prospective testing to fine-tune this promising combination of radiotherapy and immunotherapy is warranted.

68Ga-DOTA-GGNle-CycMSHhex targets the melanocortin-1 receptor for melanoma imaging

Melanocortin-1 receptor (MC1R) is a molecular target for melanoma imaging and therapy because of its overexpression on rodent and human melanoma cells. Here, we evaluated the MC1R targeting and specificity of 68Ga-DOTA-GGNle-CycMSHhex and Cy5.5-GGNle-CycMSHhex using murine and human melanoma cells, and murine and xenografted tumors. 68Ga-DOTA-GGNle-CycMSHhex was used first in human as an imaging probe to evaluate the possibility of radionuclide therapy in patients with advanced-stage melanoma. 68Ga-DOTA-GGNle-CycMSHhex and Cy5.5-GGNle-CycMSHhex displayed MC1R-specific targeting properties in murine and human melanoma cells, as well as in murine melanoma and human melanoma-xenografted tumors. Both B16/F10 and M21 melanoma lesions could be easily imaged by positron emission tomography using 68Ga-DOTA-GGNle-CycMSHhex The first-in-human images of melanoma brain metastases in patients demonstrated the clinical relevance of MC1R as a molecular target for melanoma imaging, highlighting the potential of 68Ga-DOTA-GGNle-CycMSHhex as an MC1R-targeting melanoma imaging probe and underscoring the need to develop MC1R-targeting therapeutic agents for treating patients with metastatic melanoma.

Novel therapeutic compound acridine-retrotuftsin action on biological forms of melanoma and neuroblastoma

PURPOSE

As a continuation of our search for anticancer agents, we have synthesized a new acridine-retrotuftsin analog HClx9-[Arg(NO₂)-Pro-Lys-Thr-OCH₃]-1-nitroacridine (named ART) and have evaluated its activity against melanoma and neuroblastoma lines. Both tumors develop from cells (melanocytes, neurons) of neuroectodermal origin, and both are tumors with high heterogeneity and unsatisfactory susceptibility to chemotherapies. Thus, we analyzed the action of ART on pairs of biological forms of melanoma (amelanotic and melanotic) and neuroblastoma (dopaminergic and cholinergic) with regard to proliferation, mechanism of cell death, and effect on the activity of tricarboxylic acid cycle (TAC) enzymes.

METHODS

The cytotoxicity of ART was evaluated by XTT and trypan blue tests. Cell death was estimated by plasma membrane structure changes (phosphatidylserine and calreticulin externalization), caspase activation, presence of ROS (reactive oxygen species), activity of tricarboxylic acid cycle enzymes (pyruvate dehydrogenase complex, aconitase, and isocitrate dehydrogenase), NAD level, and ATP level.

RESULTS

ART influences the biological forms of melanoma and neuroblastoma in different ways. Amelanotic (Ab) melanoma (with the inhibited melanogenesis, higher malignancy) and SHSY5Y neuroblastoma (with cholinergic DC cells) were especially sensitive to ART action. The Ab melanoma cells died through apoptosis, while, with SH-SY5Y-DC neuroblastoma, the number of cells decreased but not as a result of apoptosis. With Ab melanoma and SH-SY5Y-DC cells, a diminished activity of TAC enzymes was noticed, along with ATP/NAD depletion.

CONCLUSION

Our data show that the biological forms of certain tumors responded in different ways to the action of ART. As a combination of retrotuftsin and acridine, the compound can be an inducer of apoptotic cell death of melanoma, especially the amelanotic form. Although the mechanism of the interrelationships between energy metabolism and cell death is not fully understood, interference of ART with TAC enzymes could encourage the further investigation of its anticancer action.

Calcitriol and Calcidiol Can Sensitize Melanoma Cells to Low⁻LET Proton Beam Irradiation

Proton beam irradiation promises therapeutic utility in the management of uveal melanoma. Calcitriol (1,25(OH)₂D₃)—the biologically active metabolite of vitamin D₃—and its precursor, calcidiol (25(OH)D₃), exert pleiotropic effects on melanoma cells. The aim of the study was to evaluate the effect of both calcitriol and calcidiol on melanoma cell proliferation and their response to proton beam irradiation. Three melanoma cell lines (human SKMEL-188 and hamster BHM Ma and BHM Ab), pre-treated with 1,25(OH)₂D₃ or 25(OH)D₃ at graded concentrations (0, 10, 100 nM), were irradiated with 0–5 Gy and then cultured in vitro. Growth curves were determined by counting the cell number every 24 h up to 120 h, which was used to calculate surviving fractions. The obtained survival curves were analysed using two standard models: linear-quadratic and multi-target single hit. Calcitriol inhibited human melanoma proliferation at 10 nM, while only calcidiol inhibited proliferation of hamster lines at 10 and 100 nM doses. Treatment with either 1,25(OH)₂D₃ or 25(OH)D₃ radio sensitized melanoma cells to low doses of proton beam radiation. The strength of the effect increased with the concentration of vitamin D₃. Our data suggest that vitamin D₃ may be an adjuvant that modifies proton beam efficiency during melanoma therapy.

Hyperthermia induces therapeutic effectiveness and potentiates adjuvant therapy with non-targeted and targeted drugs in an in vitro model of human malignant melanoma

In the present study, we have aimed to characterize the intrinsic, extrinsic and ER-mediated apoptotic induction by hyperthermia in an in vitro model of human malignant melanoma and furthermore, to evaluate its therapeutic effectiveness in an adjuvant therapeutic setting characterized by combinational treatments with non-targeted (Dacarbazine & Temozolomide) and targeted (Dabrafenib & Vemurafenib) drugs. Overall, our data showed that both low (43 °C) and high (45 °C) hyperthermic exposures were capable of inducing cell death by activating all apoptotic pathways but in a rather distinct manner. More specifically, low hyperthermia induced extrinsic and intrinsic apoptotic pathways both of which activated caspase 6 only as opposed to high hyperthermia which was mediated by the combined effects of caspases 3, 7 and 6. Furthermore, significant involvement of the ER was evident (under both hyperthermic conditions) suggesting its role in regulating apoptosis via activation of CHOP. Our data revealed that while low hyperthermia activated IRE-1 and ATF6 only, high hyperthermia induced activation of PERK as well suggesting that ultimately these ER stress sensors can lead to the induction of CHOP via different pathways of transmitted signals. Finally, combinational treatment protocols revealed an effect of hyperthermia in potentiating the therapeutic effectiveness of non-targeted as well as targeted drugs utilized in the clinical setting. Overall, our findings support evidence into hyperthermia's therapeutic potential in treating human malignant melanoma by elucidating the underlying mechanisms of its complex apoptotic induction.

Cutaneous Melanoma-A Long Road from Experimental Models to Clinical Outcome: A Review

Cutaneous melanoma is a complex disorder characterized by an elevated degree of heterogeneity, features that place it among the most aggressive types of cancer. Although significant progress was recorded in both the understanding of melanoma biology and genetics, and in therapeutic approaches, this malignancy still represents a major problem worldwide due to its high incidence and the lack of a curative treatment for advanced stages. This review offers a survey of the most recent information available regarding the melanoma epidemiology, etiology, and genetic profile. Also discussed was the topic of cutaneous melanoma murine models outlining the role of these models in understanding the molecular pathways involved in melanoma initiation, progression, and metastasis.