Estrogen receptor-positive MCF-7 and triple-negative MDA-MB-231 breast cancer cell lines were exposed to CTet to evaluate cell cycle perturbation (propidium iodide staining and cytofluorimetric acquisition), induction of autophagic morphological features (co-localization of LC3b autophagosome marker and LAMP2a lysosome marker by immunofluorescence) and changes in protein expression (immunoblot and microarray-based gene expression analyses). Here, ESR1 is linked to breast cancer.