S100A1 and breast cancer: To further clarify the effect of PQQ on different BC subtypes, we divided bc into 6 groups based on classic markers, including precursor B cells (PreBC), naïve B cells (NBC), proliferating B cells (ProBC), S100A+ B cells (S100BC), plasma cells (PC), and age‐associated B cells (ABC) (Figure 4D, Figure S4D).