CD8 + Tumor infiltrating lymphocyte (TIL) in human melanomas express high levels of PD-1 and are functionally impaired. However, adoptive cell therapy using in vitro-expanded TIL can be a highly effective therapy for patients with advanced melanoma. This discrepancy led us to further analyze the CD8 + PD-1 + TILs. We found that the percentage of PD-1 expressing CD8 + T-cells was higher in the tumor digests that generate tumor-reactive TILs after in vitro culture in IL-2 (P=0.0007). Also sorted and expanded CD8 + PD-1 + T-cells in tumor digests showed much higher tumor specific IFN-γ production compared with CD8 + PD-1 -T-cells. These results suggested that tumor-specific CD8 + T-cells in melanoma tumor digests are largely PD-1 + , and this population can recover function after culturing in IL-2. PD-1 has been reported as an inhibitory receptor on T-cells. We found that the in vitro functional suppression of cultured-TILs from native levels of PD-L1 expression on melanomas was minimal, and moreover expression level of PD-1 on CD8 + tumor-specific TILs decreased during the culture. As a consequence, the PD-1 receptor can be a useful biomarker for enriching tumor specific T-cells from fresh melanomas.

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Recently T cell immunoreceptor with Ig and ITIM domains (TIGIT) was reported as a candidate for novel immune checkpoints. However, the impact of TIGIT on melanoma specific CTLs in the effector phase remains still unclear. In this study, we demonstrated that melanoma cells control anti-melanoma CTL responses via the TIGIT-CD155 interaction in the effector phase. TIGIT is an inhibitory receptor expressed on T cells, and CD155 is one of the cognate ligands expressed on the tumor cells or antigen-presenting cells. First, we confirmed that CD155 was constitutively expressed on melanoma cells. We then demonstrated that CD155 on melanoma cells suppressed cytokine release from melanoma-specific CTLs via interaction with TIGIT. Overexpression of CD155 enhanced, and its downregulation attenuated the suppressive effect. This suggested that anti-melanoma CTL responses are controlled not only by an imbalance in CD226 (an activating molecule binds to CD155) and TIGIT expression on T cells but also by the expression levels of CD155 on melanoma cells. In addition, co-blockade of TIGIT and PD-1 signals synergistically elicited a response of tumor-infiltrating lymphocytes (TILs) on autologous melanoma cells. These results suggest that the CD155-TIGIT interaction should be blocked for enhancement of anti-melanoma immune responses.Journal of Investigative Dermatology accepted article preview online, 12 October 2015. doi:10.1038/jid.2015.404.

PurposeThis phase I b study evaluated the safety and anti-tumor activity of pembrolizumab in Japanese patients with advanced melanoma.MethodsPembrolizumab (2 mg/kg) was given every 3 weeks (Q3W) for up to 2 years or until confirmed progression or unacceptable toxicity. The tumor response was assessed as per the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) by both investigator review and central review.ResultsForty-two patients with advanced melanoma received pembrolizumab. A primary cutaneous histology was observed in 34 patients (81.0%), while a primary mucosal histology was observed in 8 patients (19.0%). Thirty-four patients (81.0%) experienced treatment-related adverse events (AEs). The most common treatment-related AEs were pruritus, maculopapular rash, malaise, and hypothyroidism. Grade 3–5 treatment-related AEs occurred in 8 patients (19.0%). The only grade 3–5 treatment-related AE reported in at least two patients was anemia. There were two treatment-related deaths (unknown cause and cerebral hemorrhage). Among the 37 evaluable patients, the confirmed overall response rates (ORRs) determined by central review were 24.1% (95% CI 10.3–43.5) for cutaneous melanoma and 25.0% (95% CI 3.2–65.1) for mucosal melanoma. The responses were durable, and the median duration of response was not reached in either population. The median overall survival (OS) was not reached, with a 12-month OS of 82.7% for cutaneous melanoma and 51.4% for mucosal melanoma.ConclusionThe safety profile of pembrolizumab in Japanese patients was similar to that reported in the previous clinical studies. Pembrolizumab provided promising anti-tumor activity in Japanese patients with advanced melanoma.

Highlights d The tumor microenvironment has both skewed T ex and T non-ex clonotypes d Among skewed clonotypes, T ex , but not T non-ex , directly attack tumor cells d PD-1 blockade promotes T ex clonotype infiltration d TDLNs can be the origin of such T ex clonotypes