A bleomycin-mimicking manganese-porphyrin-conjugated mitochondria-targeting peptoid for cancer therapy

Bleomycin (BLM) is a natural product with established anticancer activity, attributed to its ability to cleave intracellular DNA. BLM complexes with iron (BLM-Fe³⁺) exhibit peroxidase-like activity, generate reactive oxygen species (ROS), and cause DNA cleavage. Inspired by the mechanism of BLM, we synthesized a novel conjugate of manganese tetraphenylporphyrin (MnTPP) with a biomimetic peptoid (i.e., oligo-N-substituted glycines); this conjugate harnesses the oxidative capabilities of manganese porphyrins combined with the cell-penetrating ability of a previously reported mitochondria-targeting peptoid (MTP). UV-vis spectroscopy showed the formation of Mn(V)-oxo porphyrin, a potent oxidative species, in the presence of hydrogen peroxide, simulating metallobleomycin reactivity. Biological assays demonstrated that MnTPP-MTP significantly boosted ROS production and induced cytotoxicity toward cancer cells, while sparing normal fibroblasts. Tetramethylrhodamine ethyl ester (TMRE) assay revealed reversible, dose-dependent impairment of the mitochondrial membrane potential by MnTPP-MTP treatment. DNA cleavage assays showed that MnTPP-MTP, specifically in the presence of hydrogen peroxide, could elicit substantial DNA damage, in a similar way to BLM. In vivo studies using liposome-encapsulated MnTPP-MTP (lipo-peptoid) indicated superior tumor suppression, without systemic toxicity, when administered locally. Immunofluorescence staining for Ki67 and TUNEL confirmed reduced cell proliferation and increased apoptosis, respectively, validating the anticancer efficacy of lipo-peptoid. These results suggest that MnTPP-MTP, particularly in a liposomal formulation, is a promising new chemotherapeutic agent with robust oxidative mechanisms, poised for further development and application against diverse cancers.