European consensus-based interdisciplinary guideline for melanoma. Part 1: Diagnostics - Update 2024

Combination Immunotherapy for Mucosal Melanoma: Molecular Mechanism, Research Status, and Future Directions

OPINION STATEMENT

Mucosal melanoma is a rare and aggressive subtype of melanoma, accounting for 1%-2% of new cases in the United States in 2023, and 20%-30% in China and other Asian countries. Its origin is often occult, with the lack of early clinical features, the absence of actionable driver mutations, and poor response to immunotherapy, all contributing to its poor prognosis. The rarity of this subtype leads to limited awareness and interventions. Furthermore, due to its immune evasion mechanisms, mucosal melanoma shows resistance to traditional immune checkpoint inhibitors. Consequently, new therapeutic strategies are urgently needed to improve patient outcomes. Recent clinical trials have suggested that combination immunotherapy can overcome immune evasion, reduce resistance to treatment, produce synergistic anti-tumor effects, and improve survival. Epidemiological factors and clinical characteristics play significant roles in diagnosis and prognosis, while the mutational landscape influences responses to immunotherapy. This review provides an overview of these aspects and systematically discusses current research on combination therapies and emerging immunotherapy approaches for mucosal melanoma. It also explores potential future directions for treatment, aiming to enhance therapeutic strategies for this rare cancer and improve patient outcomes.

KS-NailMel-1: a novel cell line of nail apparatus melanoma

Nail apparatus melanoma (NAM) is a specific type of cutaneous melanoma that develops in the nail apparatus of the hands and feet. The prognosis for metastatic NAM is poor due to a lack of fully effective systemic therapies. However, the difficulty in obtaining a NAM model has hindered basic research aimed at discovering effective treatment strategies. In this study, we established a NAM cell line, named KS-NailMel-1, from a primary tumor located on the nail apparatus of the left ring finger of a 68-year-old Japanese female. The cells were successfully maintained for over 9 months, exhibiting a doubling time of 38.6 ± 1.94 h. KS-NailMel-1 displayed consistent growth, spheroid formation, and invasiveness, and was confirmed to be identical to the original tumor through short tandem repeat analyses, whole-exome sequencing, and immunohistochemistry. Western blotting of the cells demonstrated the protein expression of NECTIN4, which has recently attracted attention as a potential therapeutic target for melanoma. The KS-NailMel-1 cell line represents a valuable resource for basic and preclinical research on NAM, deepening our understanding of the tumor characteristics and facilitating the development of treatment strategies for this rare form of cancer.

Clinical Applications of the Molecular Landscape of Melanoma: Integration of Research into Diagnostic and Therapeutic Strategies

The molecular landscape of cutaneous melanoma is complex and heterogeneous, and a deeper understanding of the genesis and progression of the tumor driven by genetic alterations is essential for the development of effective diagnostic and therapeutic strategies. Molecular diagnostics and the use of biomarkers are increasingly playing a role in treatment decisions. However, further research is urgently needed to elucidate the relationships between complex genetic alterations and the effectiveness of target therapies (although BRAF mutation is still the only targeted genetic alteration). Further research is required to exploit other targetable genetic alterations such as NRAS, KIT or rare mutations. Treatment guidelines for cutaneous melanoma are continually evolving based on data from recent and ongoing clinical trials. These advancements reflect changes mainly in the optimal timing of systemic therapy and the choice of combination therapies increasingly tailored to molecular profiles of individual tumors. Mono- or combination immunotherapies demonstrated unprecedented success of melanoma treatment; still, there is room for improvement: though several factors of primary or acquired resistance are known, they are not part of patient management as biomarkers. The novel developments of cancer vaccines to treat melanoma (melanoma-marker-based or personalized neoantigen-based) are encouraging; introduction of them into clinical practice without proper biomarkers would be the same mistake made in the case of first-generation immunotherapies.

Cutaneous melanoma

Cutaneous melanoma is a common cancer in Australia and New Zealand, Europe, and North America, and its incidence is still increasing in many regions. Ultraviolet (UV) radiation exposure (for example, through excessive sunlight exposure) remains the primary risk factor for melanoma; however, public awareness campaigns have led to a marked reduction in mortality. In addition to genetic damage from UV radiation, specific genetic alterations have been linked to melanoma. The stage of the tumour at the time of diagnosis is of greater importance for melanoma prognosis than in almost any other cancer. Context-dependent genetic mutations that attenuate tumour-suppressive mechanisms or activate growth-promoting signalling pathways are crucial factors in the development of cutaneous melanoma. In addition to external factors such as UV radiation, the tumour microenvironment can contribute to melanoma progression, invasion and metastasis. Cutaneous melanoma treatment has improved considerably over the past decade with the discovery and development of immune checkpoint inhibitors and therapy targeting BRAF and MEK. Over the next decade, several priorities are likely to influence melanoma research and management, including the continued advance of precision medicine methods to identify the most suitable patients for the most effective treatment, with the aim of improving clinical outcomes.