Triple-Frequency Electromagnetic Stimulation Combined with Fingolimod Reduces Breast Cancer Cell Proliferation and Metastasis-Associated Extracellular Vesicle Protein Levels

Background: Triple-negative breast cancer (TNBC) remains a major cause of cancer mortality due to its aggressive behavior, metabolic adaptability, and high therapeutic resistance. Extracellular vesicles (EVs) within the tumor microenvironment contribute to tumor progression and metastasis by transferring pro-tumorigenic cargo. While conventional Tumor Treating Fields use high-frequency alternating fields to disrupt mitosis, low-energy triple-frequency bioelectromagnetic approaches remain poorly characterized. Methods: We evaluated a device–drug strategy combining triple-frequency low-intensity electromagnetic stimulation (EMS2: 396 Hz, 285 Hz, 528 Hz) with the pleiotropic drug Fingolimod (FTY720). Treatments were tested in MDA-MB-231 and ARM-G breast cancer cells, with Paclitaxel as a positive control. Cell proliferation was assessed by MTS assay, and extracellular vesicles were isolated following individual and combination treatments. Quantitative LC-MS/MS proteomics was used to characterize treatment-induced changes in EVs cargo. Results: EMS2 reduced proliferation in both cell lines and produced morphological changes consistent with altered cell-cycle progression. EMS2 alone triggered adaptive metabolic responses, whereas combination with Fingolimod suppressed these compensatory signatures. EVs proteomics revealed combination-specific alterations associated with mitochondrial stress, ER stress, NF-κB suppression, and autophagy-associated pathways. The combination also reduced levels of metastasis- and stroma-associated proteins, including Mitogen-Activated Protein Kinase 12 (MAPK12) and collagen-associated ECM components (Collagen Type I Alpha 1 Chain (COL1A1), Collagen Type VI Alpha 1 Chain (COL6A1), Collagen Type VI Alpha 3 Chain (COL6A3), and Matrilin 3 (MATN3)) in EVs. Bliss independence analysis identified a subset of metastasis-associated proteins suppressed in EVs beyond the level predicted by an additive model, an exploratory finding that will require further validation with dose–response and functional assays. Conclusions: Combined triple-frequency EMS2 and Fingolimod treatment altered the extracellular vesicle proteome, inducing signatures consistent with mitochondrial and endoplasmic reticulum stress, metabolic disruption, and reduced levels of metastasis-associated and stromal/ECM remodeling proteins, along with reduced proliferation. These findings suggest a coordinated anti-cancer effect of this tunable device–drug strategy, warranting further functional and in vivo validation to confirm therapeutic potential.