Background Prostate cancer (PCa) is the second leading cause of mortality and a leading cause of malignant tumors in males. Prostate cancer stem cells (PCSCs) are likely the responsible cell types for cancer initiation, clinical treatment failure, tumor relapse, and metastasis. Estrogen receptor alpha (ERα) is mainly expressed in the basal layer cells of the normal prostate gland and has key roles in coordinating stem cells to control prostate organ development. Here, we investigated the roles of the estrogen-ERα signaling pathway in regulating PCSCs. Methods Correlation of CD49f and ERα/NOTCH1 was analyzed in human clinical datasets and tissue samples. Flow cytometry was used to sort CD49f Hi and CD49f Low cells. EZH2 recruitment by ERα and facilitation of ERα binding to the NOTCH1 promoter was validated by Co-IP and ChIP. Primary tumor growth, tumor metastasis and sensitivity to 17β-estradiol (E2) inhibitor (tamoxifen) were evaluated in castrated mice. Results ERα expression was significantly higher in CD49f Hi prostate cancer basal stem-like cells (PCBSLCs), which showed basal and EMT features with susceptibility to E2 treatment. ERα-induced estrogen effects were suggested to drive the NOTCH1 signaling pathway activity via binding to the NOTCH1 promoter. Moreover, EZH2 was recruited by ERα and acted as a cofactor to assist ERα-induced estrogen effects in regulating NOTCH1 in PCa. In vivo, E2 promoted tumor formation and metastasis, which were inhibited by tamoxifen. Conclusions Our results implicated CD49f+/ERα + prostate cancer cells associated with basal stem-like and EMT features, named EMT-PCBSLCs, in heightened potential for promoting metastasis. NOTCH1 was regulated by E2 in CD49f Hi EMT-PCBSLCs. These results contribute to insights into the metastatic mechanisms of EMT-PCBSLCs in PCa. Electronic supplementary material The online version of this article (10.1186/s12964-019-0367-x) contains supplementary material, which is available to authorized users.

Cancer‐associated fibroblasts (CAFs) can promote the development and metastasis of prostate cancer partly by mediating tumor‐associated inflammation. An increasing amount of studies have focused on the functional interactions between CAFs and immune cells in the tumor microenvironment (TME). We previously reported that G protein‐coupled receptor 30 (GPR30) was highly expressed in prostate CAFs and plays a crucial role in prostate stromal cell activation. However, the effect and underlying mechanism of GPR30 expression in prostate CAFs affecting the interaction between CAFs and tumor‐associated macrophages (TAMs) need further elucidation. Here, we found that, compared with CAF‐shControl, CAF‐shGPR30 inhibited macrophage migration through transwell migration assays, which should be attributed to the decreased expression of C‐X‐C motif chemokine ligand 12 (CXCL12). In addition, macrophages treated with a culture medium of CAF‐shGPR30 exhibited attenuated M2 polarization with downregulated M2‐like markers expression. Moreover, macrophages stimulated with a culture medium of CAF‐shGPR30 were less efficient in promoting activation of fibroblast cells and invasion of PCa cells. Finally, cocultured CAF‐shGPR30 and macrophages suppressed PCa cell invasion compared to cocultured CAF‐shControl and macrophages by decreasing interleukin‐6 (IL‐6) secretion, and this effect could be abrogated with rescue expression of IL‐6. Our results pinpoint the function of GPR30 in prostate CAFs on regulating the CAF‐TAM interaction in the TME and provide new insights into PCa therapies via regulating TME.