Background/Objectives: Cancer is one of the leading causes of death worldwide, and skin cancer is especially prevalent and lethal in Brazil. Despite advancements in treatment, there is still a need for new anticancer agents that are effective, selective, and less toxic. This study aimed to evaluate the cytotoxic and therapeutic potential of the peptide PEPAD. Methods: The cytotoxicity of PEPAD was assessed by MTT assay in murine melanoma (B16F10-Nex2), human melanoma (SK-MEL-28), breast (MCF-7), and cervical (HeLa) cancer cell lines. Selectivity was evaluated in healthy cells (RAW 264.7 and FN1). Morphological changes were analyzed by microscopy. Cell migration was assessed using scratch assays. Apoptotic features were evaluated using MitoTracker Deep Red, NucBlue, CaspACETM labeling, and flow cytometry. Immunogenic cell death was investigated by calreticulin and HMGB1 release. Molecular dynamics simulations explored peptide structure and interaction with lipid membranes. Results: PEPAD showed IC₅₀ values of 7.4 µM and 18 µM in B16F10-Nex2 and SK-MEL-28 cells, respectively, and >60 µM in MCF-7 and HeLa cells. Low toxicity was observed in healthy cells (IC₅₀ > 56 µM), indicating high selectivity. Apoptotic morphology and reduced cell migration were observed. Flow cytometry and fluorescence probes confirmed apoptosis and mitochondrial swelling. Calreticulin and HMGB1 release indicated immunogenic cell death. Simulations showed that PEPAD maintains a stable α-helical conformation and interacts with membranes. Conclusions: These findings highlight PEPAD’s selective cytotoxicity and its potential as an anticancer agent with apoptotic and immunogenic properties, making it a promising candidate for therapeutic development.

Cancer therapy remains limited by drug resistance and poor selectivity, while inflammation-driven tumor progression further complicates treatment outcomes. Antimicrobial peptides (AMPs) have emerged as promising therapeutic alternatives due to their multifunctional properties. In this study, we investigated the anticancer and immunomodulatory activities of KI17, a rationally designed peptide derived from GL18, a peptide fragment identified from the talisin protein of Talisia esculenta. KI17 exhibited dose-dependent antiproliferative effects against murine and human melanoma (B16F10-Nex2, SK-MEL-2, A375) and cervical cancer (HeLa) cell lines, while displaying reduced cytotoxicity toward non-tumoral BV-2 microglial cells, resulting in a favorable selectivity index. Mechanistic analyses revealed that KI17 induces morphological alterations, mitochondrial dysfunction, caspase activation, and late-stage apoptosis, together with G0/G1 cell cycle arrest accompanied by accumulation of the Sub-G0 population, indicating coordinated regulation of cell death and cell cycle progression. KI17 effectively suppressed lipopolysaccharide (LPS)-induced microglial activation, markedly reducing pro-inflammatory cytokine and nitric oxide production without compromising cell viability. These biological activities are consistent with the peptide’s optimized physicochemical features, including increased cationicity, amphipathicity, and α-helical folding. Overall, our findings demonstrate that KI17 combines selective anticancer activity with potent immunomodulatory effects, highlighting its potential as a bioinspired peptide for further preclinical development in cancer therapy.