We have established an immune cell therapy with immortalized induced pluripotent stem-cell–derived myeloid lines (iPS-ML). The benefits of using iPS-ML are the infinite proliferative capacity and ease of genetic modification. In this study, we introduced 4-1BBL gene to iPS-ML (iPS-ML-41BBL). The analysis of the cell-surface molecules showed that the expression of CD86 was upregulated in iPS-ML-41BBL more than that in control iPS-ML. Cytokine array analysis was performed using supernatants of the spleen cells that were cocultured with iPS-ML or iPS-ML-41BBL. Multiple cytokines that are beneficial to cancer immunotherapy were upregulated. Peritoneal injections of iPS-ML-41BBL inhibited tumor growth of peritoneally disseminated mouse melanoma and prolonged survival of mice compared to that of iPS-ML. Furthermore, the numbers of antigen-specific CD8⁺ T cells were significantly increased in the spleen and tumor tissues treated with epitope peptide-pulsed iPS-ML-41BBL compared to those treated with control iPS-ML. The number of CXCR6-positive T cells were increased in the tumor tissues after treatment with iPS-ML-41BBL compared to that with control iPS-ML. These results suggest that iPS-ML-41BBL could activate antigen-specific T cells and promote their infiltration into the tumor tissues. Thus, iPS-ML-41BBL may be a candidate for future immune cell therapy aiming to change immunological “cold tumor” to “hot tumor”.

Numerous clinical trials have demonstrated a significant improvement in recurrence‐free survival among melanoma patients receiving high‐dose interferon‐α, immune checkpoint inhibitors (pembrolizumab, nivolumab), and BRAF/MEK inhibitors (dabrafenib‐trametinib). This study aimed to investigate whether these findings hold true in real‐world conditions for patients with stage III and IV melanoma. In particular, the study explores the efficacy and side effects of adjuvant therapies, focusing on anti‐PD‐1 antibodies and BRAF/MEK inhibitors. While clinical trials have shown comparable efficacy, differences in side‐effect profiles, especially the persistence of immune‐related adverse events with anti‐PD‐1 antibodies, highlight the need for careful consideration in adjuvant settings. In the absence of established biomarkers for guiding adjuvant therapy decisions, it becomes imperative to transparently communicate the advantages and disadvantages of drug administration to patients. The study also delved into the impact of melanoma subtype and BRAF mutation status on the effectiveness of adjuvant therapy, emphasizing the need for further investigation.