ESR1 and breast cancer: Eg5 could also be a valid marker in ER+/PR+ BC: again, its pharmacological inhibition demonstrated a reduction in cell viability and proliferation probably correlated with the induction of apoptosis when Eg5 is completely inhibited: In parallel, a role for Eg5 in controlling events not related to mitotic activity, such as migration, invasion, and the occurrence of angiogenesis, was revealed.