FLT1 and breast cancer: Consistent with our preclinical observations (Figs. 3 and EV3), a blinded pathological examination revealed a statistically significant association between FLT1 expression (both activated and total) at pre-treatment and shorter progression-free survival (p = 0.012 for pFLT1 and p = 0.005 for total FLT1, Fig. 7A–C; Appendix Fig. S2A,B) in patients with breast cancer.