NECTIN4-targeted antibody-drug conjugate is a potential therapeutic option for extramammary Paget disease.

Extramammary Paget disease (EMPD) is a rare skin cancer mainly found in areas rich in apocrine sweat glands. Since the effective treatments for advanced and/or metastasized EMPD are limited, there is an urgent need to develop novel therapeutic approaches. Nectin cell adhesion molecule 4 (NECTIN4) is highly expressed in cancers and considered to be a promising therapeutic target. NECTIN4 is also expressed in EMPD, but its role and the efficacy of NECTIN4-targeted therapy in EMPD remain unclear. This study investigated the potential of NECTIN4 as a novel therapeutic target for EMPD. NECTIN4 expression was immunohistochemically analysed in EMPD patients' primary (118 samples) and metastatic (21 samples) lesions. Using an EMPD cell line, KS-EMPD-1, the effects of NECTIN4 inhibition on cell proliferation and migration were investigated. NECTIN4 was expressed in primary and metastatic EMPD lesions, and the H-score of NECTIN4 staining was significantly higher in metastatic lesions than in primary ones. Knockdown of NECTIN4 significantly inhibited cell proliferation and affected cell migration. The cytotoxic effects of NECTIN4-targeted antibody-drug conjugate (ADC) were further evaluated, revealing a significant decrease in EMPD cell viability. In conclusion, NECTIN4 is a potential therapeutic target and NECTIN4-targeted ADC is promising as a therapeutic option for EMPD.

TROP2 Expression and Therapeutic Implications in Cutaneous Squamous Cell Carcinoma: Insights From Immunohistochemical and Functional Analysis.

Cutaneous squamous cell carcinoma (cSCC) is a common form of skin cancer, but treatments for advanced cases have limited efficacy. Trophoblast cell-surface antigen 2 (TROP2) is a cell-surface protein that is widely expressed in various tumours, where it exerts significant influence over critical processes such as tumour cell growth, apoptosis, migration, invasion and metastasis. Sacituzumab govitecan, an antibody-drug conjugate (ADC) targeting TROP2, is emerging as a promising strategy for anticancer therapy. In this study, we investigated TROP2 expression in cSCC tissues from 51 patients and evaluated its function in the A431 human SCC cell line. Immunohistochemical analysis revealed TROP2 expression on the plasma membrane of cSCC tissues and A431 cells. A431 cells showed sensitivity to sacituzumab govitecan with a significant concentration-dependent decrease in viable cell number. In addition, Knockdown of TROP2 resulted in decreased expression of cyclin D1 and BCL-2, along with reduced cell viability. Knockdown of TROP2 also resulted in decreased expression of vimentin, along with reduced migratory capacity. These findings suggest that TROP2 plays a crucial role in cSCC cell proliferation and migration, and highlight the potential of sacituzumab govitecan as a promising therapeutic option for cSCC.

Efficacy and safety of TM5614 in combination with paclitaxel in the treatment of paclitaxel-resistant cutaneous angiosarcoma: Phase II study protocol.

Cutaneous angiosarcoma (CAS) is an endothelial cell-derived, highly aggressive type of vascular tumour. Although chemoradiotherapy with paclitaxel (PTX) is recognized as a first-line therapy for CAS, second-line therapy for CAS remains controversial, and there is no standard therapy for taxane-resistant CAS. Plasminogen activator inhibitor-1 (PAI-1) is associated with poor clinical outcomes, and elevated levels of PAI-1 in both tissue and serum are correlated with poor response to therapy in various cancers, including skin cancers. Since PAI-1 protects endothelial cells from Fas ligand-mediated apoptosis, PAI-1 inhibition might induce apoptosis of endothelial cell-derived tumours such as CAS. This is a single-arm, open-label, multi-institutional, Phase 2 clinical trial to assess the efficacy and safety of PTX in combination with TM5614 (PAI-1 inhibitor) in patients with PTX-resistant CAS. PTX will be administered for 28 weeks, with oral administration of TM5614. The primary endpoint of this study will be the overall response rate (ORR) at 28 weeks after starting treatment (central image evaluation). The secondary endpoint will include the ORR at 28 weeks after starting treatment (investigator evaluation), ORR at 8 weeks and 16 weeks after initiation of treatment (central and investigator evaluation), progression-free survival, overall survival, disease control rate and safety profiles. Assuming the null hypothesis of a response rate of 13.6% and an alternative hypothesis of 45%, a minimum of 15 patients are required to achieve a two-sided, Type I error of 5% and power of 70% based on the exact binomial distribution. Data quality control will be conducted by a combination of centralized (remote) and on-site monitoring. This study will contribute to the development of novel combination therapy for PTX-resistant CAS patients, which remains an unmet clinical need.

Recent treatment and prognosis in 643 patients with extramammary Paget's disease.

Information about extramammary Paget's (EMPD) treatment is limited because of the rarity of the disease. The prognosis differs between in situ EMPD and invasive EMPD; therefore, therapy should be planned according to the disease stage. We collected data on 643 EMPD cases treated between 2015 and 2019 in Japan and assessed recent trends in EMPD treatment and prognosis based on the EMPD-oriented TNM staging. Among the 643 patients, 317 had stage 0 (49.3%), 185 had stage I (28.8%), 51 had stage II (7.9%), 18 had stage IIIA (2.8%), 48 had stage IIIB (7.5%) and 24 had stage IV (3.7%) disease. Each stage showed a distinct survival curve, with the exception of stages II and IIIA. Curative surgery was most common in patients with stage 0-III disease. Chemotherapy was the first-line therapy, mainly in patients with stage IIIB and IV disease, most commonly with docetaxel (DTX), followed by DTX + tegafur gimeracil oteracil potassium (TS-1) and TS-1. Patients with local disease exhibited a 4.4% recurrence rate. Univariate analysis revealed no prognostic differences according to age, sex or primary tumour site. SLNB was not related to disease-specific survival. In multivariate analysis, female sex significantly predicted local relapse in stage 0-I (HR 3.09; 95% CI, 1.13-8.43), and initial treatment with curative surgery was significantly protective in terms of disease-specific survival in stage II-IIIA (HR, 0.17; 95% CI, 0.04-0.71) and stage IIIB-IV (HR 0.16; 95% CI, 0.05-0.51). Further clinical studies are needed to improve the prognosis of patients with stage II-IV EMPD.

Pigmented epithelioid melanocytoma arising from a teratoma of a Carney complex patient.

A 25-year-old female Carney complex patient with a PRKAR1A mutation who had undergone surgery to remove teratomas visited our dermatology department. She was suspected of having a malignant melanoma in a teratoma. On clinical examination, a black nodule was found within the cyst. On histopathological examination, the black lesion was composed of heavily pigmented round cells with vesicular nuclei and single prominent nucleoli. Additionally, there were large cells with irregularly shaped nuclei. Upon immunohistochemical examination, the large, irregularly shaped cells were positively stained with Melan A, HMB45, S-100 protein, SOX10, CD10 (focally), and BRAFV600E , but negatively stained with PRAME. Based on the histopathological features, we diagnosed the patient with pigmented epithelioid melanocytoma (PEM) in a teratoma of a Carney complex patient. This is the first case of PEM developing from a teratoma. Since PEM lesions may spread to regional lymph nodes, careful follow-up is necessary.

Regulatory Mechanism of the IL-33-IL-37 Axis via Aryl Hydrocarbon Receptor in Atopic Dermatitis and Psoriasis.

Interleukin (IL)-33 and IL-37 have been identified as novel cytokines involved in various inflammatory diseases. However, their specific roles remain largely unknown. Recent studies have shown that IL-33, which triggers inflammation, and IL-37, which suppresses it, cooperatively regulate the balance between inflammation and anti-inflammation. IL-33 and IL-37 are also deeply involved in the pathogenesis of inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis. Furthermore, a signaling pathway by which aryl hydrocarbon receptor (AHR), a receptor for dioxins, regulates the expression of IL-33 and IL-37 has been revealed. Here, we outline recent findings on the mechanisms regulating IL-33 and IL-37 expression in AD and psoriasis. IL-33 expression is partially dependent on mitogen-activated protein kinase (MAPK) activation, and IL-37 has a role in suppressing MAPK in human keratinocytes. Furthermore, IL-33 downregulates skin barrier function proteins including filaggrin and loricrin, thereby downregulating the expression of IL-37, which colocalizes with these proteins. This leads to an imbalance of the IL-33-IL-37 axis, involving increased IL-33 and decreased IL-37, which may be associated with the pathogenesis of AD and psoriasis. Therefore, AHR-mediated regulation of the IL-33-IL-37 axis may lead to new therapeutic strategies for the treatment of AD and psoriasis.

Current Management and Treatment of Extramammary Paget's Disease.

OPINION STATEMENT: Extramammary Paget's disease (EMPD) is a rare neoplastic disease affecting areas rich in apocrine glands in the elderly. EMPD clinically resembles a benign inflammatory skin disease, and ill-defined tumor borders can lead to misdiagnosis and incomplete excision. Several prognostic factors have been reported, including nodule formation, tumor thickness, tumor invasion, lymphovascular invasion, and a perianal location, which are characteristic of primary tumors. EMPD typically presents as an in situ tumor spreading horizontally within the epidermis and then invading into the dermis as it transitions to a vertical growth phase. For this reason, tumor thickness, rather than tumor size, is correlated with patient prognosis. The best treatment for resectable EMPD is complete surgical removal of the tumor. EMPD sometimes has unclear tumor borders, and it can unexpectedly spread beyond its clinical boundaries. Surgical resection in such cases is often associated with tumor-positive margins, which can result in recurrence. However, surgical excision with wide margins may deteriorate patients' organ functions and quality of life. Mohs micrographic surgery may be ideal for controlling the surgical margins and minimizing the sacrifice of normal tissue, but this technique is not always feasible because of constraints associated with the medical environment. No standard treatment for unresectable or metastatic EMPD has been established. Although conventional chemotherapy has been used as the first-line treatment, it frequently causes adverse events, and consequently, targeted therapy will become more valuable in the near future.

Nectin-4: a Novel Therapeutic Target for Skin Cancers.

OPINION STATEMENT: Nectin-4 is a tumor-associated antigen that is highly expressed on various cancer cells, and it has been further proposed to have roles in tumor development and propagation ranging from cellular proliferation to motility and invasion. Nectin-4 blockade reduces tumor proliferation and induces apoptosis in several malignancies. Nectin-4 has been used as a potential target in antibody-drug conjugate (ADC) development. Enfortumab vedotin, an ADC against Nectin-4, has demonstrated efficacy against solid tumor malignancies. Enfortumab vedotin has received US Food and Drug Administration approval for treating urothelial cancer. Furthermore, the efficacy of ADCs against Nectin-4 against solid tumors other than urothelial cancer has been demonstrated in preclinical studies, and clinical trials examining the effects of enfortumab vedotin are ongoing. Recently, Nectin-4 was reported to be highly expressed in several skin cancers, including malignant melanoma, cutaneous squamous cell carcinoma, and extramammary Paget's disease, and involved in tumor progression and survival in retrospective studies. Nectin-4-targeted therapies and ADCs against Nectin-4 could therefore be novel therapeutic options for skin cancers. This review highlights current knowledge on Nectin-4 in malignant tumors, the efficacy of enfortumab vedotin in clinical trials, and the prospects of Nectin-4-targeted agents against skin cancers.

Adjuvant Anti-PD-1 Antibody Therapy for Advanced Melanoma: A Multicentre Study of 78 Japanese Cases.

Anti-PD-1 antibodies (Abs) are among the optimal adjuvant therapies for melanoma at high risk of recurrence, especially BRAF wild-type melanoma, but the anti-tumour effects of anti-PD-1 Abs in the adjuvant setting for acral melanoma have not been evaluated previously. The aim of this study was to analyse the efficacy and safety profiles of anti-PD-1 Ab monotherapy in the adjuvant setting in an Asian population including a high ratio of acral melanoma. The efficacy and safety profiles of anti-PD-1 Ab monotherapy in the adjuvant setting were retrospectively analysed in 78 Japanese patients with advanced melanoma, including 31 cases (40%) of acral melanoma. Overall relapse-free survival was 60.3% (47 of 78 cases, 95% confidence interval (CI) 49.2-70.4%), and 39.7% of patients (31 of 78 patients, 95% CI 29.6-50.8%) relapsed during the adjuvant PD-1 Ab treatment. Six cases (7.9%) discontinued the protocol due to serious adverse events. One case (1.3%) discontinued the protocol due to trauma. The relapse-free survival of acral melanoma was 25.8%, whereas that of high cumulative sun damage was 60.0%, and that of low cumulative sun damage was 57.1%. The acral type had a significantly lower 12-month relapse-free survival than other cutaneous types (p = 0.029). The acral type appeared to be an independent prognostic factor on multivariate analysis (p = 0.015). Adverse events due to anti-PD-1 antibody were observed in 37.1% overall. The results of this study suggest that anti-PD-1 Ab therapy in the adjuvant setting is less effective for acral melanoma than for other cutaneous types.

BRAF Heterogeneity in Melanoma.

OPINION STATEMENT: In the era of molecular targeted therapy, the accurate detection of BRAF mutation in melanoma has become increasingly important. With the advances of molecular analyses and immunohistochemistry, the presence of BRAF mutational heterogeneity in melanoma has been widely recognized. Although most patients with melanoma have a homogeneous BRAF mutation status because the BRAF mutation occurs at an early stage of melanoma development and acts as a driver gene mutation, BRAF mutational heterogeneity does exist, among different tumor sites of a single patient (intertumor heterogeneity) and/or even within a single tumor (intratumor heterogeneity). To summarize the published reports, about 10% of melanoma patients may show intertumorally discordant BRAF status and about 15% of BRAF-mutated melanomas may have intratumor BRAF heterogeneity, although the reported results vary strikingly among the studies and methods used. Considering the BRAF heterogeneity of melanoma, a single biopsy from a single tumor may not be sufficient to uncover the entire BRAF status of a patient. Multiple samples from different sites may be preferable to assess the indication of BRAF/MEK inhibitors, as recommended by the current clinical guidelines. The impact of BRAF heterogeneity on patient survival or the response to treatment with BRAF/MEK inhibitors is an interesting issue, but requires further investigation.

NECTIN4: A Novel Therapeutic Target for Melanoma.

Malignant melanoma is the most common lethal skin cancer and causes death in a short time when metastasized. Although BRAF inhibitors (BRAFi) have greatly improved the prognosis of BRAF-mutated melanoma, drug resistance is a major concern even when they are combined with MEK inhibitors. Alternative treatments for BRAFi-resistant melanoma are highly anticipated. Nectin cell adhesion molecule 4 (NECTIN4) is highly expressed and associated with progression in tumors. We aimed to investigate the role of NECTIN4 in melanoma and its potency as a therapeutic target using 126 melanoma samples and BRAFi-resistant cells. Immunohistochemically, most of the clinical samples expressed NECTIN4, at least in part. NECTIN4 was highly expressed in BRAF-mutated melanoma and its high expression was associated with disease-free survival. In BRAFi-resistant melanoma cells, NECTIN4 and the PI3K/Akt pathway were upregulated, along with the acquisition of BRAFi resistance. Monomethyl auristatin E, a cytotoxic part of NECTIN4-targeted antibody-drug conjugate, was effective for BRAF-mutated or BRAFi-resistant melanoma cells. NECTIN4 inhibition increased the sensitivity of BRAFi-resistant cells to BRAFi and induced apoptosis. In conclusion, we revealed the expression and roles of NECTIN4 in melanoma. Targeted therapies against NECTIN4 can be a novel treatment strategy for melanoma, even after the acquisition of BRAFi resistance.

Trop2 Expression in Extramammary Paget's Disease and Normal Skin.

Extramammary Paget's disease (EMPD) is a rare skin cancer arising in the apocrine gland-rich areas. Most EMPD tumors are dormant, but metastatic lesions are associated with poor outcomes owing to the lack of effective systemic therapies. Trophoblast cell surface antigen 2 (Trop2), a surface glycoprotein, has drawn attention as a potential therapeutic target for solid tumors. Sacituzumab govitecan, an antibody-drug conjugate of Trop2, has recently entered clinical use for the treatment of various solid cancers. However, little is known about the role of Trop2 in EMPD. In this study, we immunohistochemically examined Trop2 expression in 116 EMPD tissue samples and 10 normal skin tissues. In normal skin, Trop2 was expressed in the epidermal keratinocytes, inner root sheaths, and infundibulum/isthmus epithelium of hair follicles, eccrine/apocrine glands, and sebaceous glands. Most EMPD tissues exhibited homogeneous and strong Trop2 expression, and high Trop2 expression was significantly associated with worse disease-free survival (p = 0.0343). These results suggest the potential use of Trop2-targeted therapy for EMPD and improve our understanding of the skin-related adverse effects of current Trop2-targeted therapies such as sacituzumab govitecan.

The CCL20 and CCR6 axis in psoriasis.

Psoriasis is a TNF-α/IL-23/IL-17A-mediated inflammatory skin disease that causes a significant socioeconomic burden in afflicted patients. IL-17A-producing immune cells, including Th17 cells, are crucial effector cells in the development of psoriasis. IL-17A stimulates epidermal keratinocytes to produce CCL20, which eventually recruits CCR6 + Th17 cells into the lesional skin. Thus, the CCL20/CCR6 axis works as a driving force that prepares an IL-17A-rich cutaneous milieu. In this review, we summarize the current research topics on the CCL20/CCR6 axis and the therapeutic intervention of this axis for psoriasis.

CK1α ablation in keratinocytes induces p53-dependent, sunburn-protective skin hyperpigmentation.

Casein kinase 1α (CK1α), a component of the ß-catenin destruction complex, is a critical regulator of Wnt signaling; its ablation induces both Wnt and p53 activation. To characterize the role of CK1α (encoded by Csnk1a1) in skin physiology, we crossed mice harboring floxed Csnk1a1 with mice expressing K14-Cre-ERT2 to generate mice in which tamoxifen induces the deletion of Csnk1a1 exclusively in keratinocytes [single-knockout (SKO) mice]. As expected, CK1α loss was accompanied by ß-catenin and p53 stabilization, with the preferential induction of p53 target genes, but phenotypically most striking was hyperpigmentation of the skin, importantly without tumorigenesis, for at least 9 mo after Csnk1a1 ablation. The number of epidermal melanocytes and eumelanin levels were dramatically increased in SKO mice. To clarify the putative role of p53 in epidermal hyperpigmentation, we established K14-Cre-ERT2 CK1α/p53 double-knockout (DKO) mice and found that coablation failed to induce epidermal hyperpigmentation, demonstrating that it was p53-dependent. Transcriptome analysis of the epidermis revealed p53-dependent up-regulation of Kit ligand (KitL). SKO mice treated with ACK2 (a Kit-neutralizing antibody) or imatinib (a Kit inhibitor) abrogated the CK1α ablation-induced hyperpigmentation, demonstrating that it requires the KitL/Kit pathway. Pro-opiomelanocortin (POMC), a precursor of α-melanocyte-stimulating hormone (α-MSH), was not activated in the CK1α ablation-induced hyperpigmentation, which is in contrast to the mechanism of p53-dependent UV tanning. Nevertheless, acute sunburn effects were successfully prevented in the hyperpigmented skin of SKO mice. CK1α inhibition induces skin-protective eumelanin but no carcinogenic pheomelanin and may therefore constitute an effective strategy for safely increasing eumelanin via UV-independent pathways, protecting against acute sunburn.

NECTIN4 Expression in Extramammary Paget's Disease: Implication of a New Therapeutic Target.

Extramammary Paget's disease (EMPD) is a rare skin cancer arising in the anogenital area. Most EMPD tumors remain dormant as in situ lesions, but the outcomes of patients with metastatic EMPD are poor because of the lack of effective systemic therapies. Nectin cell adhesion molecule 4 (NECTIN4) has attracted attention as a potential therapeutic target for some cancers. Urothelial cancer is one such cancer, and clinical trials of enfortumab vedotin, a drug-conjugated anti-NECTIN4 antibody, are ongoing. However, little is known regarding the role of NECTIN4 in EMPD. In this study, we conducted immunohistochemical analysis of NECTIN4 expression in 110 clinical EMPD samples and normal skin tissue. In normal skin, positive signals were observed in epidermal keratinocytes (particularly in the lower part of the epidermis), eccrine and apocrine sweat glands, inner and outer root sheaths, and matrix of the hair follicles. The most EMPD lesions exhibited strong NECTIN4 expression, and high NECTIN4 expression was significantly associated with increased tumor thickness, advanced TNM stage, and worse disease-specific survival. These results support the potential use of NECTIN4-targeted therapy for EMPD. Our report contributes to the better understanding of the pathobiology of NECTIN4 in the skin and the skin-related adverse effects of NECTIN4-targeted therapy.

The EGFR-ERK/JNK-CCL20 Pathway in Scratched Keratinocytes May Underpin Koebnerization in Psoriasis Patients.

Epidermal keratinocytes represent a rich source of C-C motif chemokine 20 (CCL20) and recruit CCR6+ interleukin (IL)-17A-producing T cells that are known to be pathogenic for psoriasis. A previous study revealed that scratch injury on keratinocytes upregulates CCL20 production, which is implicated in the Koebner phenomenon characteristically seen in psoriasis patients. However, the molecular mechanisms leading to scratch-induced CCL20 production remain elusive. In this study, we demonstrate that scratch injury upregulates the phosphorylation of epidermal growth factor receptor (EGFR) and that the specific EGFR inhibitor PD153035 attenuates scratch-induced CCL20 upregulation in an extracellular signal-related kinase (ERK)-dependent, and to a lesser extent, a c-Jun N-terminal kinase (JNK)-dependent but p38 mitogen-activated protein kinase (MAPK)-independent manner. Immunoreactive CCL20 was visualized in the keratinocytes that lined the scratched wound. IL-17A also induced the phosphorylation of EGFR and further augmented scratch-induced CCL20 upregulation. The EGFR-ERK/JNK-CCL20 pathway in scratched keratinocytes may explain why Koebnerization is frequently seen in psoriasis patients.

The IL-13-OVOL1-FLG axis in atopic dermatitis.

Despite sharing interleukin-4 receptor α (IL-4Rα) in their signaling cascades, IL-4 and IL-13 have different functions in atopic inflammation. IL-13 preferentially participates in the peripheral tissues because tissue-resident group 2 innate lymphoid cells produce IL-13 but not IL-4. In contrast, lymph node T follicular helper cells express IL-4 but not IL-13 to regulate B-cell immunity. The dominant microenvironment of IL-13 is evident in the lesional skin of atopic dermatitis (AD). The IL-13-rich local milieu causes barrier dysfunction by down-regulating the OVOL1-filaggrin (FLG) axis and up-regulating the periostin-IL-24 axis. Genome-wide association studies also point to the crucial involvement of the IL-13, OVOL1 and FLG genes in the pathogenesis of AD. Biologics targeting IL-13, such as the anti-IL-4Rα antibody dupilumab and the anti-IL-13 antibody tralokinumab, successfully improve AD lesions and further highlight the importance of IL-13 in the pathogenesis of AD.

Adjuvant Therapy for Melanoma.

OPINION STATEMENT: In recent years, the number of patients with malignant melanoma has continued to increase globally; surgery remains the first treatment option for patients with resectable melanoma. Adjuvant therapy for patients with stage III and IV melanoma following surgical resection has gradually been approved. After complete resection, these patients can probably derive significant benefit from adjuvant therapy. New treatments that improve the long-term survival of patients with unresectable advanced or metastatic melanoma are currently under evaluation in adjuvant therapy to increase relapse-free survival and overall survival. We here review several relevant clinical trials of radiotherapy, systemic immune therapies, molecular-targeted therapies, and neoadjuvant therapies in order to shed light on most suitable adjuvant therapy. The findings of this review include the following: The use of interferon-α2b will be restricted for patients with ulcerated primary melanoma in countries with no access to new drugs in adjuvant therapy. Ipilimumab should not be considered as the first-line therapy due to its lower efficacy and severe toxicity. The use of anti-programmed death-1 antibody would be a relevant adjuvant therapy for patients without BRAF mutation. If the BRAF mutation status is positive, the combination of dabrafenib and trametinib is a plausible option. The establishment of appropriate therapeutic planning and clinical endpoints in adjuvant therapy should affect the standard of care. The choice of optimal adjuvant therapy for individual patients is an important issue.

Periostin Links Skin Inflammation to Melanoma Progression in Humans and Mice.

It is widely accepted that chronic inflammation initiates and promotes carcinogenesis and tumor progression in various cell types. However, this paradigm has not been comprehensively investigated in melanoma. To investigate the effects of chronic inflammation on the progression of melanoma, we established a murine inflammatory skin model and investigated the relationship between skin inflammation and melanoma progression. In a murine model, B16F10 melanoma cells in inflamed skin grew significantly more rapidly than cells in control skin. The stromal expression of periostin was upregulated in inflamed skin, and significantly more CD163⁺ M2 macrophages were recruited to the melanomas in inflamed skin. We then immunohistologically examined the expression of stromal periostin and the infiltration of CD163⁺ M2 macrophages in human acral lentiginous melanomas (n = 94) and analyzed the statistical associations with clinicopathological variables. In human melanomas, high periostin expression and a large number of infiltrated M2 macrophages were significantly correlated with poor prognosis. Furthermore, we confirmed that periostin promotes the proliferation of murine and human melanoma cells in vitro. Our findings indicate that periostin and M2 macrophages play a critical role in melanoma progression and prognosis in both humans and mice, indicating that periostin is a potential target for treating progressive melanoma.

Intra- and Inter-Tumor BRAF Heterogeneity in Acral Melanoma: An Immunohistochemical Analysis.

The current development of BRAF inhibitors has revolutionized the treatment of unresectable melanoma. As the potential heterogeneity of BRAF mutations in melanoma has been reported, accurate detection of BRAF mutations are important. However, the genetic heterogeneity of acral melanoma-a distinct type of melanoma with a unique genetic background-has not fully been investigated. We conducted a retrospective review of our acral melanoma patients. Of the 196 patients with acral melanoma, we retrieved 31 pairs of primary and matched metastatic melanomas. We immunostained the 31 pairs with VE1, a BRAFV600E-mutation-specific monoclonal antibody. Immunohistochemistry with VE1 showed a high degree of sensitivity and specificity for detecting BRAFV600E mutations compared with the real-time polymerase chain reaction method. A total of nine primary (29.0%) and eight metastatic (25.8%) acral melanomas were positive for VE1. In three patients (9.7%), we observed a discordance of VE1 staining between the primary and metastatic lesions. Of note, VE1 immunohistochemical staining revealed a remarkable degree of intra-tumor genetic heterogeneity in acral melanoma. Our study reveals that VE1 immunostaining is a useful ancillary method for detecting BRAFV600E mutations in acral melanoma and allows for a clear visualization of intra- and inter-tumor BRAF heterogeneity.