Updated project metadata. Hypoxia is an important driver of cancer progression, and rapidly growing tumors often result in intratumoral hypoxic regions. Hypoxia is associated with metabolic reprogramming and angiogenesis, resulting in enhanced tumor progression. Here, we aimed to study breast cancer hypoxia responses at the proteomic level, and we wanted to identify differences in protein secretion from luminal-like and basal-like cell lines before and after hypoxia.