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Dpep is a cell-penetrating peptide that targets transcription factors ATF5, CEBPB and CEBPD to selectively suppress growth and survival of diverse tumor cell types in vitro and in vivo. Due to these actions and its apparent safety, the peptide has potential as a cancer therapeutic. How Dpep might be combined with other anti-cancer agents to achieve synergistic efficacy and to overcome possible peptide resistance has not been assessed in depth. Based on prior work indicating that Dpep promotes apoptotic cancer cell death and up-regulates multiple pro-apoptotic and tumor suppressor genes, we studied combinations of Dpep with ABT-263, a pro-apoptotic BCL2 family inhibitor, and decitabine, a hypomethylating drug. Combining Dpep with each agent alone or together synergistically suppressed the growth of a range of solid and liquid tumor cell types. Moreover, the combinations synergistically inhibited the growth of cells lines that were selected either in vivo or in vitro for Dpep resistance. Finally, we tested the combination of Dpep with ABT-263 in a mouse melanoma xenograft model. The combination more effectively inhibited tumor growth than either agent alone and, in contrast to vehicle or ABT-263, produced a 40% durable survival rate. Taken together, these observations highlight potential drug partners for the therapeutic development of Dpep.

Immune rejection is one of the most serious challenges in allogeneic transplantation, including allogeneic induced pluripotent stem cell (allo-iPSC)-derived cell therapy. Beta-2-Microglobulin gene-knockout, human leukocyte antigen (HLA) class I-deficient iPSCs can evade immune rejection by host T cells, which occurs due to HLA mismatches. However, natural killer (NK) cells recognize HLA class Ⅰ-deficient cells and reject them, which is known as the missing-self response. Introducing chimeric HLA-E protein to HLA class Ⅰ-deficient iPSCs suppresses the missing-self response of NK cells expressing the inhibitory receptor NKG2A; however, technology to suppress NKG2A-negative NK cells is still required. Here, we developed novel agonists for the other inhibitory receptor, killer immunoglobulin receptor (KIR), on NK cells. We found that antibodies that bind to activating KIR enhance NK cell activation and developed selective agonists for inhibitory KIRs (KIR2DL1, KIR2DL2/3, and KIR3DL1). Introducing these selective inhibitory KIR agonists on T cells and HLA class Ⅰ-deficient iPSCs allowed them to evade immune rejection by NK cells. Additionally, we identified an NKG2A-selective agonist as an alternative to chimeric HLA-E, which stimulates the activating receptor NKG2C. This technology enhances immune tolerance in allo-iPSCs and facilitates the development of various iPSC-derived regenerative medicines. The online version contains supplementary material available at 10.1038/s41598-025-18394-z. Subject terms: Allotransplantation, NK cells

Natural killer (NK) cells are an important innate defense against malignancies, and exogenous sources of NK cells have been developed as anti-cancer agents. Nevertheless, the apparent limitations of NK cells in clearing cancers have suggested that their efficacy might be augmented by combination with other treatments. We have developed cell-penetrating peptides that target the transcription factors ATF5, CEBPB, and CEBPD and that promote apoptotic cancer cell death both in vitro and in vivo without apparent toxicity to non-transformed cells. We report here that one such peptide, Dpep, significantly sensitizes a variety of tumor cell types to the cytotoxic activity of the NK cell line, NK-92MI. Such sensitization requires pre-exposure of tumor cells to Dpep and does not appear due to effects of Dpep on NK cells themselves. Our findings suggest that Dpep acts in this context to lower the apoptotic threshold of tumor cells to NK cell toxicity. Additionally, while Dpep pre-treatment does not prevent tumor cells from causing NK cell “inactivation”, it sensitizes cancer cells to repeated rounds of exposure to fresh NK cells. These findings thus indicate that Dpep pre-treatment is an effective strategy to sensitize cancer cells to the cytotoxic actions of NK cells.