Significant and Various Effects of ML329-Induced MITF Suppression in the Melanoma Cell Line.

To study the inhibitory effects on microphthalmia-associated transcription factor (MITF)-related biological aspects in malignant melanomas (MMs) in the presence or absence of the low-molecular MITF specific inhibitor ML329, cell viability, cellular metabolic functions, and three-dimensional (3D) spheroid formation efficacy were compared among MM cell lines including SK-mel-24, A375, dabrafenib- and trametinib-resistant A375 (A375DT), and WM266-4. Upon exposure to 2 or 10 µM of ML329, cell viability was significantly decreased in WM266-4, SK-mel-24, and A375DT cells, but not A375 cells, in a dose-dependent manner, and these toxic effects of ML329 were most evident in WM266-4 cells. Extracellular flux assays conducted using a Seahorse bioanalyzer revealed that treatment with ML329 increased basal respiration, ATP-linked respiration, proton leakage, and non-mitochondrial respiration in WM266-4 cells and decreased glycolytic function in SK-mel-24 cells, whereas there were no marked effects of ML329 on A375 and A375DT cells. A glycolytic stress assay under conditions of high glucose concentrations also demonstrated that the inhibitory effect of ML329 on the glycolytic function of WM266-4 cells was dose-dependent. In addition, ML329 significantly decreased 3D-spheroid-forming ability, though the effects of ML329 were variable among the MM cell lines. Furthermore, the mRNA expression levels of selected genes, including STAT3 as a possible regulator of 3D spheroid formation, KRAS and SOX2 as oncogenic-signaling-related factors, PCG1a as the main regulator of mitochondrial biogenesis, and HIF1a as a major hypoxia transcriptional regulator, fluctuated among the MM cell lines, possibly supporting the diverse ML329 effects mentioned above. The findings of diverse ML329 effects on various MM cell lines suggest that MITF-associated biological activities are different among various types of MM.

Effects of temozolomide on tumor mutation burden and microsatellite instability in melanoma cells.

The efficacy of combination therapy with an immune checkpoint inhibitor (ICI) and cytotoxic chemotherapeutic agents has been investigated in cancer, including melanoma. Before ICIs were introduced, dacarbazine or temozolomide (TMZ) were used to treat melanoma. Several studies using glioma or colorectal cancer cells showed that TMZ can increase the tumor mutation burden (TMB) and induce mismatch repair (MMR) deficiency associated with microsatellite instability (MSI). These could increase immunoreactivity to an ICI, but this has not been evaluated in melanoma cells. We investigated the effects of TMZ on MSI status and TMB in melanoma cells. To evaluate the TMB, we performed whole-exome sequencing using genomic DNA from the human melanoma cell lines Mel18, A375, WM266-4, G361, and TXM18 before and after TMZ treatment. Polymerase chain reaction amplification of five mononucleotide repeat markers, BAT25, BAT26, NR21, NR24, and MONO27, was performed, and we analyzed changes in the MSI status. In all cell lines, the TMB was increased after TMZ treatment (the change amount of TMB with ≤ 5% variant allele frequency [VAF] was 18.0-38.3 mutations per megabase) even in the condition without obvious cytological damage. MSI after TMZ treatment was not observed in any cells. TMZ increased TMB but did not change MSI status in melanoma cells.

3D Spheroid Configurations Are Possible Indictors for Evaluating the Pathophysiology of Melanoma Cell Lines.

To study the molecular mechanisms responsible for inducing the spatial proliferation of malignant melanomas (MM), three-dimension (3D) spheroids were produced from several MM cell lines including SK-mel-24, MM418, A375, WM266-4, and SM2-1, and their 3D architectures and cellular metabolisms were evaluated by phase-contrast microscopy and Seahorse bio-analyzer, respectively. Several transformed horizontal configurations were observed within most of these 3D spheroids, and the degree of their deformity was increased in the order: WM266-4, SM2-1, A375, MM418, and SK-mel-24. An increased maximal respiration and a decreased glycolytic capacity were observed within the lesser deformed two MM cell lines, WM266-4 and SM2-1, as compared with the most deformed ones. Among these MM cell lines, two distinct cell lines, WM266-4 and SK-mel-24, whose 3D appearances were the closest and farthest, respectively, from being horizontally circular-shaped, were subjected to RNA sequence analyses. Bioinformatic analyses of the differentially expressed genes (DEGs) identified KRAS and SOX2 as potential master regulatory genes for inducing these diverse 3D configurations between WM266-4 and SK-mel-24. The knockdown of both factors altered the morphological and functional characteristics of the SK-mel-24 cells, and in fact, their horizontal deformity was significantly reduced. A qPCR analysis indicated that the levels of several oncogenic signaling related factors, including KRAS and SOX2, PCG1α, extracellular matrixes (ECMs), and ZO1 had fluctuated among the five MM cell lines. In addition, and quite interestingly, the dabrafenib and trametinib resistant A375 (A375DT) cells formed globe shaped 3D spheroids and showed different profiles in cellular metabolism while the mRNA expression of these molecules that were tested as above were different compared with A375 cells. These current findings suggest that 3D spheroid configuration has the potential for serving as an indicator of the pathophysiological activities associated with MM.

Genetic analyses of a secondary poroma and trichoblastoma in a HRAS-mutated sebaceous nevus.

A sebaceous nevus is a congenital skin hamartoma caused by postzygotic HRAS or KRAS mosaic mutations. With age, affected individuals may develop secondary tumors within a sebaceous nevus. RAS mutations are harbored from the onset of sebaceous nevus, and further mutations can be expected to be required in order to explain the initiation of secondary tumors. However, genetic analyses of the secondary tumors have not been conducted. Herein, we describe the rare coexistence of a poroma and a trichoblastoma arising in a sebaceous nevus. This is the first report of an investigation of multiple genes in a secondary tumor in an SN. First, HRAS c.37G>C, which is the common mutation in sebaceous nevus, was detected in all three lesions (sebaceous nevus, poroma, and trichoblastoma). Next, to elucidate the potential second-hit mutations in the secondary poroma and trichoblastoma, we applied a panel sequencing for skin cancers that was newly developed in our institution. Our comparison of the mutational profile of 95 skin cancer-related genes in each of the three lesions newly revealed TP53 p.R158P in the poroma and NOTCH2 p.G329S in the trichoblastoma. TP53 p.R158P has been determined as a pathogenic mutation in other tumors, and NOTCH2 p.G329S was a novel mutation. We identified two novel mutations that may have contributed to the pathogenesis of the secondary tumor's development. The roles of the mutations remain unclear.

Usefulness of neuron-specific enolase as a serum marker of metastatic melanoma.

Treatment strategies for advanced melanoma are dramatically changing, due to immune-checkpoint inhibitors and BRAF/MEK inhibitors. Nevertheless, reliable serum markers for evaluation of treatment responses and the outcome are still limited. Some previous reports suggested that serum neuron-specific enolase (sNSE) may be a useful marker for melanoma; however, its usefulness is controversial. Moreover, NSE has not been examined in vitro by using melanoma cell lines. We retrospectively evaluated sNSE and serum lactate dehydrogenase (sLDH) levels at the initial diagnosis and during therapy in 33 melanoma patients of various stages. We analyzed the NSE concentrations in cell lysates and supernatants from melanoma cell lines by enzyme-linked immunosorbent assay. The median sNSE was significantly higher in stage IV patients compared with stages I/II and III (16.3, 12.7 and 12.1 ng/mL, respectively). sNSE was elevated in 20% (2/10) of stage III and 61.1% (11/18) of stage IV patients but not in stages I/II. sNSE and sLDH tended to correspond to the total tumor volume (P = 0.48 and 0.58; 95% confidence intervals, 0.005-0172 and 0.776-0.836, respectively). The coincidence rate of sNSE and sLDH in stage IV at the initial diagnosis was 11 of 18 (61.1%). Of the remaining patients, elevated sNSE but not sLDH was observed in five patients (27.8%) and elevated sLDH but not sNSE was observed in two (11.1%). Four of the five patients showing elevated sNSE and normal sLDH were of the mucosal type. NSE was detected in both supernatant and cell lysate of all four melanoma cell lines (0.30-237.32 ng/mL and 137-483.04 ng/mg, respectively). Two cell lines with a high supernatant NSE level contained many dead cells in the supernatant. The combination of sNSE and sLDH could contribute to the early detection of distant metastasis and disease condition evaluations for advanced melanoma patients.

Genetic analyses of mosaic neurofibromatosis type 1 with giant café-au-lait macule, plexiform neurofibroma and multiple melanocytic nevi.

Neurofibromatosis type 1 (NF1) is a genodermatosis caused by heterozygous germ line variations in the NF1 gene. A second-hit NF1 aberration results in the formation of café-au-lait macules, cutaneous neurofibroma and plexiform neurofibroma (PNF). Mosaic NF1 (mNF1), caused by a postzygotic NF1 mutation, is characterized by localized or generalized NF1-related manifestations. Although NF1 and mNF1 are associated with pigmentary skin lesions, clinically recognizable melanocytic nevi that developed over PNF have not been reported. Here, we report the first case of multiple melanocytic nevi that developed on a giant café-au-lait macule and PNF. The PNF had biallelic NF1 deletions, a whole deletion of NF1 and a novel intragenic deletion involving exons 25-30. The deletions were not detected in the blood, which resulted in the diagnosis of mNF1. Furthermore, the nevus cells had not only biallelic NF1 deletions but also NRAS Q61R, a common mutation found in congenital melanocytic nevi. These analyses revealed the coexistence of the two different mosaic diseases, mNF1 and congenital melanocytic nevi. For a diagnosis of cases with atypical NF1-like symptoms, genetic analyses using blood and lesional tissues are useful and aid in genetic counseling.

The potent pro-oxidant activity of rhododendrol-eumelanin induces cysteine depletion in B16 melanoma cells.

RS-4-(4-Hydroxyphenyl)-2-butanol (rhododendrol, RD), a skin-whitening agent, is known to induce leukoderma in some people. To explore the mechanism underlying this effect, we previously showed that the oxidation of RD with mushroom or human tyrosinase produces cytotoxic quinone oxidation products. We then examined the metabolism of RD in B16F1 melanoma cells in vitro and detected RD-pheomelanin and RD-quinone bound to non-protein and protein thiols. In this study, we examined the changes in glutathione (GSH) and cysteine in B16 cells exposed to RD for up to 24 h. We find that the levels of cysteine, but not those of GSH, decrease during 0.5- to 3-h exposure, due to oxidation to cystine. This pro-oxidant activity was then examined using synthetic melanins. Indeed, we find that RD-eumelanin exerts a pro-oxidant activity as potent as Dopa-pheomelanin. GSH, cysteine, ascorbic acid, and NADH were oxidized by RD-eumelanin with a concomitant production of H2 O2 . We propose that RD-eumelanin induces cytotoxicity through its potent pro-oxidant activity.

Biochemical effects of the flavanol-rich lychee fruit extract on the melanin biosynthesis and reactive oxygen species.

An ingredient of fruit polyphenol, resveratrol, is known to have an inhibitory effect on melanogenesis. In order to examine the functional differences between resveratrol and other fruit polyphenols, we compared biochemical effects of a resveratrol-free polyphenol, flavanol-rich lychee fruit extract (FRLFE), with other phenolic compounds including resveratrol. FRLFE as well as hydroquinone and resveratrol suppressed growth of B16F1 melanoma cells more significantly than rhododendrol or arbutin. Resveratrol suppressed mushroom tyrosinase at the lowest concentration (23.0 µmol/L) among the compounds tested. FRLFE and hydroquinone suppressed tyrosinase at almost the same concentration (half maximal inhibitory concentration [IC50 ], 83.5 and 94.6 µmol/L, respectively), which was higher than rhododendrol, ascorbic acid and arbutin (IC50 , 245, 345 and 421 µmol/L, respectively). Western blot analysis revealed that although resveratrol decreased expressions of tyrosinase and tyrosinase-related protein 1, FRLFE did not affect their expressions. Both FRLFE and resveratrol suppressed antimycin A-mediated reactive oxygen species (ROS) production in melanocytic cells. Resveratrol-mediated ROS suppression was inhibited by nicotinamide, a SIRT1 inhibitor. However, FRLFE-mediated suppression was not affected by nicotinamide. Moreover, FRLFE directly decreased superoxide in vitro, as detected by superoxide dismutase-like scavenging activity assay. These results suggest that FRLFE can protect melanocytes from cytotoxicity caused by an excess amount of melanin and ROS in a different manner from resveratrol.

Diagnosis of eight groups of xeroderma pigmentosum by genetic complementation using recombinant adenovirus vectors.

Because patients with xeroderma pigmentosum (XP) must avoid ultraviolet (UV) light from an early age, an early diagnosis of this disorder is essential. XP is composed of seven genetic complementation groups, XP-A to -G, and a variant type (XP-V). To establish an easy and accurate diagnosis of the eight disease groups, we constructed recombinant adenoviruses that expressed one of the XP cDNA. When fibroblasts derived from patients with XP-A, -B, -C, -D, -F or -G were infected with the adenovirus expressing XPA, XPB, XPC, XPD, XPF or XPG, respectively, and UV-C at 5-20 J/m2 was irradiated, cell viability was clearly recovered by the corresponding recombinant adenoviruses. In contrast, XP-E and XP-V cells were not significantly sensitive to UV irradiation and were barely complemented by the matched recombinant adenoviruses. However, co-infection of Ad-XPA with Ad-XPE increased survival rate of XP-E cells after UV-C exposure. When XP-V cell strains, including one derived from a Japanese patient, were infected with Ad-XPV, exposed to UV-B and cultured with 1 mmol/L of caffeine, flow cytometry detected a characteristic decrease in the S phase in all the XP-V cell strains. From these results, the eight groups of XP could be differentiated by utilizing a set of recombinant adenoviruses, indicating that our procedure provides a convenient and correct diagnostic method for all the XP groups including XP-E and XP-V.

Two Cases of Cutaneous Squamous Cell Carcinoma Arising in Immunosuppressed Patients with Chronic Human Papillomavirus Infection.

Increasing evidence has suggested that human papillomaviruses (HPVs) are linked to a large subset of numerous malignant tumors, including mucosal squamous cell carcinoma (SCC); however, its involvement in cutaneous SCC has not fully been elucidated. Cutaneous SCC is the second most common type of skin cancer and is increasing in frequency every year. Since we have no satisfactory treatment for advanced SCC, it is important to provide a definitive diagnosis and appropriate therapeutic intervention at an early stage. Here, we present two cases of SCC arising in immunosuppressed patients. In these cases, we suspected the association between SCC and HPV infection histopathologically and succeeded in proving the presence of high-risk type HPV by PCR analysis (HPV 14 in case 1 and HPV 23 and 38 in case 2). Although it is unclear whether HPV actually induced SCC in our cases, our cases showed rapid progression comparing to typical courses of actinic keratosis (AK)/SCC. SCC and AK are common diseases; in daily practice, dermatologists examine many patients with immunosuppression of various causes. We should apply increased oncological vigilance to these patients to prevent an aggressive course of SCC/AK.

Effects of rhododendrol and its metabolic products on melanocytic cell growth.

BACKGROUND: Rhododendrol (RD), a skin-whitening agent, is believed to be associated with cases of cosmetics-related leukoderma that have been reported in Japan. Recently, we have shown that RD is catalyzed by tyrosinase to produce putative toxic metabolites RD-catechol and RD-cyclic catechol. OBJECTIVE: To examine the cytotoxicity and production of reactive oxygen species (ROS) in melanocytic cells by RD and its metabolic products. METHODS: The growth inhibitory effect of RD or its metabolite on the normal human epidermal melanocyte (NHEM) and B16F1 cells was assessed by cell counting or WST assay. ROS production was detected by flow cytometry and confocal microscopy after cells were treated with 2',7'-dichlorofluorescein and RD or its metabolite. RESULTS: Growth of NHEM derived from African American (NHEMb) and B16F1 cells was suppressed by 300µM or more RD. Growth inhibitory activity of RD (IC50 of B16F1: 671µM) was weaker than hydroquinone (IC50 of B16F1: 28.3µM) or resveratrol (IC50 of B16F1: 27.1µM). Flow cytometric analysis detected ROS production in the NHEMb and B16F1 cells exposed to RD. However, neither RD nor H2O2 increased the subG1 fraction of these melanocytic cells. RD-catechol and RD-cyclic catechol inhibited growth of NHEMb and B16F1 cells much more strongly than did RD. RD-catechol, as well as RD, produced ROS detected by both flow cytometry and immunostaining, while RD-cyclic catechol produced a hardly detectable amount of ROS in B16F1 cells. CONCLUSIONS: These results suggest that RD exerts the cytotoxicity in melanocytic cells through its oxidative metabolites and that ROS plays a role in RD-mediated cytotoxicity.