PTX3 governs trastuzumab-induced cardiotoxicity. (A and B) The level of PTX3 in HUVECs medium. (A) Western blot and quantification of PTX3 (n = 3). (B) ELISA analysis of PTX3 (n = 3). (C) ELISA analysis of PTX3 on the plasma from patients as indicated. (D–G) The conditioned medium and PTX3-neutralizing antibody were used to treat CCC-HEH-2 cells and iPSC-CMs. (D) The contractility of CCC-HEH-2 cells (n = 8). (E–G) The normalized survival rate, contraction amplitude, and beat rate of iPSC-CMs (n = 6 individuals). (H) The transcriptional level of PTX3 was measured by qPCR in HUVECs (WT and PTX3 KO, n = 5). (I) The secretion level of PTX3 was measured by western blot (n = 3). (J–M) The conditioned medium from HUVECs (WT and PTX3 KO) were treated with CCC-HEH-2 cells and iPSC-CMs. (J) The contractility of CCC-HEH-2 cells (n = 8). (K–M) The normalized viability, contraction amplitude, and beat rate of iPSC-CMs (n = 6 individuals). The P-value was calculated by one-way ANOVA (Dunnett’s or Sidak multiple comparisons tests). NS, no significance; *P < 0.05, **P < 0.01, ***P < 0.001. Ctrl-Medium, control medium; Tra-Medium, trastuzumab medium; PTX3 Neu-Antibody, PTX3-neutralizing antibody.