Although nivolumab is associated with a significant improvement in overall survival and progression-free survival, only 20 to 40% of patients experience long-term benefit. It is therefore of great interest to identify a predictive marker of clinical benefit for nivolumab. To address this issue, the frequencies of CD4 T cell subsets (Treg, Th1, Th2, Th9, Th17 and Th22), CD8 T cells, and serum cytokine levels (IFNγ, IL-4, IL-9, IL-10, TGF-β) were assessed in 46 patients with melanoma. Eighteen patients responded to nivolumab, and the other 28 patients did not. An early increase in Th9 cell counts during the treatment with nivolumab was associated with an improved clinical response. Before the first nivolumab infusion, the responders displayed elevated serum concentrations of TGF-β compared to non-responders. Th9 induction by IL-4 and TGF-β was enhanced by PD-1/PD-L1 blockade . The role of IL-9 in disease progression was further assessed using a murine melanoma model. IL-9 blockade promoted melanoma progression in mice using an autochthonous mouse melanoma model, and the cytotoxic ability of murine melanoma-specific CD8 T cells was enhanced in the presence of IL-9 . These findings suggest that Th9 cells, which produce IL-9, play an important role in the successful treatment of melanoma patients with nivolumab. Th9 cells therefore represent a valid biomarker to be further developed in the setting of anti-PD-1 therapy.

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These findings demonstrate that patients with melanoma have distinct and differential perturbation of both regulatory and nonregulatory FOXP3+ T cells. The degree of perturbation is associated with tumour burden and progression, suggesting that the perturbation reflects fundamental pathophysiological processes in patients with melanoma. The presented analysis provides a practical approach to investigate the immunological environment of cancer patients.

We report a case of malignant melanoma (MM) derived from cerebriform intradermal naevus (CIN) in a 66-year-old Japanese man. The patient had cutis verticis gyrata (CVG) on the posterior area of the scalp at birth. He noticed a dome-shaped nodule at the centre of the CVG at 66 years of age. Histopathological examination found a nodule of MM arising within an extensive area of intradermal naevus. There was no metastasis to lymph nodes or other organs. To our knowledge, only two cases of CIN in which MM had later developed have been reported. We estimated that the incidence of melanoma from CIN including our case is 4.5% (3 of 67 reported cases), which seems to be comparable to the frequency of malignant alteration of giant pigmented naevi. This suggests that pathological examination is recommended for CVG, and once pathological diagnosis of CIN is confirmed, long clinical follow-ups are necessary for detecting development of MM.