ESR1 and cancer: AR induces telomerase expression in primary hematopoietic stem cells (HSCs) through aromatase-dependent conversion of testosterone into oestrogen and ERα activation, whereas oestrogens are pro-angiogenic and enhance endothelial cell proliferation and migration mediated by diffusible factors, such as vascular endothelial growth factor A (VEGFA) and platelet activating factor, both secreted regularly in response to oestrogen by cancer cells.