Background: Continuous intra-arterial administration of peplomycin (PEP) through a tumor-feeding artery using an intravascular indwelling catheter is one of the best treatments for cutaneous squamous cell carcinoma (SCC) on cosmetic areas. Although this reagent is useful for the treatment of SCC, its immunomodulatory effect on the tumor microenvironment is still unknown. Objective/Methods: In this study, we investigated the immunomodulatory effects of PEP on the tumor-infiltrating regulatory T cells and tumor-associated macrophages as well as CD8+TIA-1+ cytotoxic T cells in the lesional skin of 5 patients with SCC on the lips. Results: Our data suggest that, in addition to the direct antitumor effects, PEP decreased immunosuppressive cells and increased cytotoxic T lymphocytes at the tumor sites, which might maintain antitumor immune response against SCC.
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