ESR1 and breast carcinoma: Cancer-Associated-Fibroblast (CAF)-derived microvesicles, containing oncomiR-221 promoted de novo endocrine resistance—as overexpression of oncomiR-221/222 in luminal breast cancer cells reduces ER expression (182) Furthermore CAFs can promote the cancer stem cell phenotype by secreting CCL2, inducing Notch1 (183).