▪Treatment time‐dependent generation of H2O2, NO2–, and HOCl with modest pH increase in culture medium▪Treatment time‐dependent cytotoxicity and decline in metabolic activity in 2D cultures and 3D tumour spheroids▪At 24h and 48h, increased surface expression of CRT, HSP70, HSP90, MHC I, and PD‐L1 in both cell lines▪LC3 (autophagy) increase in MCF‐7, and elevated ATP and HSP70 secretion in both cell lines. Here, CD274 is linked to neoplasm.