ESR1 and breast carcinoma: The network pharmacology-based experimental strategy should be useful for molecular subtypes of clinical breast cancer such as Luminal A, Luminal B, HER-2-enriched, and TNBC, where the gene expression status of genes coding for the hormone receptors ESR1 (ER-α), ESR2 (ER-β), and PR (progesterone receptor) and of genes coding for the growth factor receptors IGF1-R (insulin-like growth factor 1), EGFR (epidermal growth factor receptor), and HER-2 (human epidermal growth factor receptor-2) are associated with chemo-endocrine resistance.