Additionally, Ruenraroengsak et al. examined the in vitro chemotherapeutic effectiveness of ZnONPs loaded through a mesoporous silica nanolayer (MSN) against drug-sensitive breast cancer cells (MCF-7: estrogen receptor-positive, CAL51: triple-negative) and their drug-resistant counterparts (MCF-7TX, CALDOX). This evidence concerns the gene ESR1 and breast cancer.