Given our finding that HSP27 is directly related to chemoresistance in HER2+ BC, we prepared two HER2+ TZMB-resistant breast cancer cell lines to elucidate the detailed role played by HSP27 in the TZMB-refractory mechanism: JIMT-1 (ER-/PR-/HER2+ subtype, from a TZMB-treating patient showing innate resistance) and the TZMB-refractory BT474 (BT-TR; ER+/PR+/HER2+ subtype; acquired resistance) (Figure S2A). Here, ESR1 is linked to breast cancer.