ESR1 and breast neoplasm: When these synthesized SNIPERS tested against ER-α-positive breast tumor cells (MCF-7 and T47D) and ER-α-negative breast tumor cells (MDA-MB-231), a significant number of MCF-7 cells, but not T47D cells were underwent apoptosis under microscopic analysis, which later confirmed by flow cytometric analysis and annexin V/propidium iodide (PI) staining.