Yoko Funasaka

Metabotropic glutamate receptor subtype-1 is essential for in vivo growth of melanoma

Ectopic expression of metabotropic glutamate receptor subtype 1 (mGluR1) in mouse melanocytes induces melanoma formation. Although requirement of mGluR1 for development of melanoma in the initial stage has been demonstrated, its role in melanoma growth in vivo remains unclear. In this study, we developed novel transgenic mice that conditionally express mGluR1 in melanocytes, using a tetracycline regulatory system. Pigmented lesions on the ears and tails of the transgenic mice began to appear 29 weeks after activation of the mGluR1 transgene, and the transgenic mice produced melanomas at a frequency of 100% 52 weeks after transgene activation. Subsequent inactivation of the mGluR1 transgene in melanoma-bearing mice inhibited melanoma growth with reduction of immunoreactivity to phosphorylated ERK1/2, whereas mice with persistent expression of mGluR1 developed larger melanoma burdens. mGluR1 expression is thus required not only for melanoma development but also for melanoma growth in vivo. These findings suggest that growth of melanoma can be inhibited in vivo by eliminating only one of the multiple genetic anomalies involved in tumorigenesis.

Guide for medical professionals (i.e., dermatologists) for the management of Rhododenol-induced leukoderma.

Because some users develop depigmentation after the use of melanogenesis‐inhibiting products containing the quasi‐drug ingredient Rhododenol, Japanese Dermatological Association (JDA) established a Special Committee on the Safety of Cosmetics Containing Rhododenol on July 17, 2013 and management guide for dermatologists has been updated on the website in order to delineate the diagnostic criteria for Rhododenol‐induced leukoderma and provides a broad guide for standard treatment based on current knowledge. This guide is produced on the basis of the guide (version 7) updated on June 20, 2014 in the website. Rhododenol‐induced leukoderma refers to depigmentation of varying severity that develops after the use of cosmetics containing Rhododenol, mainly at the site of use. In most cases, repigmentation of part or all the affected area is evident after discontinuation. Histopathologically cellular infiltration around the hair follicles and melanophages are present in most cases. The number of melanocytes in the lesion is declined but not totally absent in most cases. Rhododenol itself is a good substrate for tyrosinase, resulting in the formation of Rhododenol metabolites (e.g., Rhododenol quinone). Melanocytes are damaged by Rhododenol metabolites during the subsequent metabolic process. The continued use of cosmetics containing Rhododenol thus induces tyrosinase activity‐dependent cytotoxicity in melanocytes in the epidermis at application sites, resulting in decreasing the amount of melanin produced by melanocytes; the addition of some other factor to this process is believed to subsequently cause the decrease or disappearance of melanocytes themselves from the epidermis.

Effect of chemical peeling on the skin in relation to UV irradiation

Abstract:  Chemical peeling is one of the dermatological treatments available for certain cutaneous diseases and conditions or improvement of cosmetic appearance of photoaged skin. However, it needs to be clarified whether the repetitive procedure of chemical peeling on photodamaged skin is safe and whether the different chemicals used for peeling results in similar outcomes or not. In this article, we reviewed the effect of peeling or peeling agents on the skin in relation to ultraviolet (UV) radiation. The pretreatment of peeling agents usually enhance UV sensitivity by inducing increased sunburn cell formation, lowering minimum erythematous dose and increasing cyclobutane pyrimidine dimers. However, this sensitivity is reversible and recovers to normal after 1‐week discontinuation. Using animals, the chronic effect of peeling and peeling agents was shown to prevent photocarcinogenesis. There is also an in vitro study using culture cells to know the detailed mechanisms of peeling agents, especially on cell proliferation and apoptotic changes via activating signalling cascades and oxidative stress. It is important to understand the effect of peeling agents on photoaged skin and to know how to deal with UV irradiation during the application of peeling agents and treatment of chemical peeling in daily life.

Effective treatment by glycolic acid peeling for cutaneous manifestation of familial generalized acanthosis nigricans caused by FGFR3 mutation

Acanthosis nigricans (AN) can occur as a cutaneous manifestation of genetic diseases, one of which is associated with activating mutations of the fibroblast growth factor receptor 3 gene (FGFR3).

Investigation by in vivo reflectance confocal microscopy: melanocytes at the edges of solar lentigines

Abstract:  In vivo reflectance confocal microscopy (RCM) provides high‐resolution, real‐time optical sections of the skin in a non‐invasive manner, allowing visualization of the skin in its native state. Highly reflective skin components including melanin, collagen and keratin appear bright (white) in RCM images. RCM examination of solar lentigines is known to show features that correlate well with histologic findings such as supranuclear melanin caps, but there are a limited number of reports on melanocyte dendrites. In this study, we utilized RCM to investigate the melanocyte dendricity and distribution within solar lentigines. Seventeen healthy Japanese females who had fairly large solar lentigines on their faces were recruited to join our clinical study, and we examined them by using RCM on their non‐lesional areas, and the inside and the outer rim of the lesional areas. As a result, we discovered that dendritic melanocytes were rarely seen in the center of a solar lentigo (SL), but were seen at a very high frequency in the outer rim of a SL. The results suggest that the melanocytes are more active at the edge of a SL, produce more melanin, and often spread their dendrites widely in a horizontal direction. The findings in this report might shed light on the dynamic pathomechanisms of solar lentigines in vivo.

BRAF, KIT and NRAS mutations and expression of c-KIT, phosphorylated extracellular signal-regulated kinase and phosphorylated AKT in Japanese melanoma patients.

To clarify the status of gene mutation and activation of growth signal in melanoma of Japanese patients in vivo, we analyzed the mutation of BRAF exon 15, NRAS exon 2, and KIT exons 9, 11, 13, 17 and 18 in melanoma cells obtained by laser capture microdissection, and performed direct sequencing in 20 cases of acral lentiginous melanoma (ALM) and 17 cases of superficial spreading melanoma (SSM). In the study of the mutation of BRAF, pyrosequencing was also done. To examine the cell proliferation signaling, immunohistochemistry for phosphorylated extracellular signal‐regulated kinase (pERK), phosphorylated AKT (phosphorylated AKT) and c‐KIT was done. The mutation of BRAF p.V600E was detected in 13 cases of ALM (65.0%) and 12 cases of SSM (70.6%). No NRAS mutation was found in all cases. The mutation in exons 9, 11, and 18 of KIT was detected in nine cases. The mutation of BRAF and KIT showed no correlation with clinical stage, lymph node metastasis, tumor thickness, ulceration and histology. pERK and pAKT was observed in small population of melanoma cells and there was no correlation with gene mutation. Our results indicate that the mutations of BRAF and KIT exist in Japanese melanoma patients, however, the cell growth signaling may be regulated by not only these mutated genes, but by other unknown regulatory factors, which may affect the prognosis of melanoma.

Effect of infrared radiation A on photoaged hairless mice harboring eumelanin and pheomelanin in the epidermis

Infrared radiation A (IRA) is absorbed by melanin and generates heat. Therefore, the effect of IRA could be well analyzed using skin, which contains melanin in the epidermis. Hairless mice harboring epidermal melanocytes that produce eumelanin, pheomelanin, or non‐melanin were generated by backcrossing K14‐stem cell factor mice, recessive yellow mice, and then albino hairless mice. High‐dose IRA was irradiated over 18 weeks after the establishment of photoaged mice by irradiation with ultraviolet B (UVB) three times a week for 14 weeks. Tumor formation was assessed every week. The formation of cyclobutane pyrimidine dimer and apoptotic cells by the irradiation of IRA and UVB was evaluated. Repetitive irradiation of IRA did not promote tumor formation in all types of mice. Pre‐irradiation of IRA to UVB, but not post‐irradiation, accelerated the elimination of cyclobutane pyrimidine dimers and enhanced apoptosis; these effects were most obvious in eumelanin‐producing mice. Real‐time polymerase chain reaction analysis showed downregulation of FLICE (cellular caspase 8)‐like inhibitory protein and B‐cell lymphoma‐extra large and upregulation of Bcl‐2‐associated X protein by UVB, but further enhancement of these molecules by pre‐irradiation of IRA was not observed. These results indicate that IRA does not confer the promotion of UVB‐induced carcinogenesis in photoaged mice harboring epidermal melanocytes and that photochemical reaction between IRA and melanin might be involved in the induction of apoptosis and the elimination of cyclobutane pyrimidine dimers by UVB. The enhancement of apoptosis by pre‐irradiation of IRA to UVB might be induced by mechanisms other than the modification of the mRNA expression of FLICE (cellular caspase 8)‐like inhibitory protein, B‐cell lymphoma‐extra large, and Bcl‐2‐associated X.

Glycosylation of tyrosinase is a determinant of melanin production in cultured melanoma cells

The majority of malignant melanoma cell types are able to produce melanin and the degree of melanin synthesis in various types of cultured cell line differs. In this study, we evaluated three types of cultured cell line, MNT‑1, HM3KO and G‑361, with differing melanin production levels. The level was greatest in the MNT‑1 cells, lower in the HM3KO cells and lowest in the G‑361 cells. In addition, a positive correlation between melanin production and tyrosinase activity was observed. The molecular masses of tyrosinases from HM3KO and G‑361 cells were marginally lower than those from MNT‑1 cells. Glycosylation inhibitor treatment on MNT‑1 cells caused decreases in the molecular mass of tyrosinase, its activity and melanin production. An immunoprecipitation assay using anti‑tyrosinase indicated that the immature glycosylated tyrosinases were associated with a type of chaperone, Hsp70. The interaction between tyrosinase and Hsp70 was also detected in HM3KO and G‑361 cells. The results indicated that the immature glycosylation of tyrosinase has a critical effect on the melanin-producing ability of melanoma cells.

Eczematous reactions mimicking psoriasiform dermatitis induced by nivolumab for advanced lung cancer

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Squamous Cell Carcinomas on Bilateral Feet Arising in Long-Standing Eczematous Lesions

We present a woman with squamous cell carcinomas on both feet in long-standing eczematous lesions. Histopathological examination of biopsies from the both feet revealed highly atypical cells invading the reticular layer of the dermis in the hyperkeratotic lesion and they were associated with surrounding dermatitis with spongiosis. Although the cause and etiology of eczema in our case is unclear, we speculate that the exceptionally long-lasting dermatitis might have induced double SCCs on bilateral feet with an unusual constitution. To the best of our knowledge, this is a first case of SCC on bilateral feet arising in long-standing eczematous lesions.