FLT1 and neoplasm: Indeed, by immunohistochemical analysis, we observed a striking increase in levels of both phosphorylated FLT1 (Tyr1213; referred to as “pFLT1” hereafter) and total FLT1 in tumor cells from PARPi-resistant tumors compared to PARPi-sensitive tumors (Figs. 3A,B; EV3A,B).