PGR and breast cancer: Our research further demonstrates that targeting ERα-positive cells with the ERα-positive/PR-positive/HER2-negative receptor profile using the MELK inhibitor alone or in combination with the endocrine therapy drug Tam, as well as targeting ERα-positive cells representing the ERα-positive/PR-negative/HER2-positive phenotype with the ALK inhibitor AP alone or in combination with HER2 activity-blocking drugs such as gefitinib and erlotinib, offer promising strategies to curb the cell proliferation of specific ERα-positive BC subtypes.