Nonionizing Millimeter-Wave Therapy: Effects on Lung Cancer Spheroids

Non‑thermal millimeter‑wave (MMW) irradiation (75–110 GHz) represents a promising non‑invasive strategy for cancer therapy. Lung cancer remains the leading cause ‎of cancer‑related mortality worldwide, highlighting the need for alternative therapeutic modalities that can overcome resistance and minimize toxicity. Yet the effects ‎of MMW exposure in physiologically relevant 3D systems remain insufficiently ‎characterized. Here, we evaluated the anti‑cancer efficacy of MMW exposure in 3D ‎lung cancer spheroids (NCI‑H1299, A549) alongside noncancerous WI‑38 fibroblasts. ‎Cells were irradiated using two antenna types—a waveguide (WG; localized, ‎high-power density) and a pyramidal horn (PH; broader coverage, lower power ‎density)—with or without a frequency multiplier to modulate local energy delivery. ‎Acute responses were assessed by XTT viability assays (day 2) and apoptosis (flow ‎cytometry), while chronic effects were evaluated using clonogenic survival (day 10) ‎and senescence markers. ‎ MMW exposure reduced cancer cell survival in a time‑ and power‑dependent manner ‎and induced sustained growth inhibition. Apoptosis was markedly higher in cancer ‎cells than in non‑cancerous WI‑38 cells and was further amplified under power-enhanced conditions. WG irradiation produced strong localized antiproliferative ‎effects, whereas the PH antenna enabled broader coverage while maintaining selective cytotoxicity toward NCI‑H1299 cells. Notably, p53‑deficient NCI‑H1299 cells ‎exhibited up to ~64% apoptosis after 60 min of exposure, whereas WI‑38 fibroblasts ‎remained below ~20%, demonstrating robust cancer selectivity. These findings high-‎light the selective, non‑thermal anticancer potential of MMW irradiation in 3D tumor ‎models and provide a mechanistic and experimental foundation for further preclinical ‎optimization of MMW‑based therapeutic strategies.