Overall, the above findings indicate that combined stimulation of HR+/HER2− human breast cancer cells (MCF-7 and T47D) by factors that represent three different arms of the TME—hormonal, inflammatory and growth-promoting—strongly promotes the proportions of CSCs, the release of the pro-metastatic chemokine CXCL8 and PD-L1 expression (the latter by MCF-7 cells only). Here, CD274 is linked to breast carcinoma.