We have established an immune cell therapy with immortalized induced pluripotent stem‐cell‐derived myeloid lines (iPS‐ML). The benefits of using iPS-ML is the infinite proliferative capacity and ease of genetical modification. We have reported the effectiveness of type I interferon-expressing iPS-ML against malignant melanoma. 
 4-1BB is an inducible receptor of the TNF superfamily expressed on activated T cells. The interaction between the receptor 4-1BB and its ligand 4-1BBL provides co-stimulatory signals for T-cell activation. In this study, we introduced 4-1BBL gene to iPS-ML (iPS-ML-41BBL). The analysis of the cell-surface molecules showed that the expressions of CD80 and CD86 were upregulated in iPS-ML-41BBL compared to control iPS-ML. Peritoneal injections of iPS-ML-41BBL reduced the tumor growth of peritoneally disseminated mouse melanoma (OVA-expressing melanoma; MO4) and prolonged survival of mice compared to iPS-ML. Furthermore, the numbers of OVA-specific CD8+ T cells were significantly increased in spleen and tumor tissues treated with OVA epitope peptide-pulsed iPS-ML-41BBL than those without. The cytokine array analysis was performed using the supernatants of spleen cells that were co-cultured with iPS-ML or iPS-ML-41BBL. Multiple cytokines were upregulated such as CXCR16, MMP-2, Eotaxin, TIMP1 and TCA3. Among them, we focused on CXCL16 and its receptor, CXCR6. CXCR6-potitive T cells were up regulated in the spleen and tumor tissues by the treatments with iPS-ML-41BBL than those without.
 These results suggested that iPS-ML-41BBL could activate antigen specific T cells and might be a candidate for future immune cell therapy utilizing iPS cells.

Immunotherapy with 4-1BBL-expressing iPScell-derived myeloid lines