Zebrafish functional xenograft vasculature platform identifies PF-502 as a durable vasculature normalization drug

Tumor vasculature are structurally chaotic and functionally inefficient. Restoring aberrant tumor blood vessels, or “normalize” the tumor vasculature can alleviate hypoxia and enhance intra-tumoral drug delivery. However, identifying tumor vascular normalizing drugs are currently hampered by an absence of efficient screening platform. We aimed to develop a robust method to visualize, digitalize and evaluate the structural and functional changes of tumor vasculature in batch: zebrafish functional xenograft vasculature platform (zFXVP). As proof of principle, we applied zFXVP to a small compound library which has been implicated in affecting the morphology of tumor vasculature. zFXVP identified PF-502 as a durable tumor vascular normalization agent. Further molecular analysis using RNA-Seq, pharmaceutical inhibition and gene knockout indicate PF-502 can induce endothelial cell cycle arrest and simplify redundant tumor vasculature by blocking PI3K/mTOR signaling and stabilize the vessel lumen and stimulate the blood function by activating Notch1 signaling with mediating S3 cleavage. Last, in mouse tumor xenograft model, PF-502 reproduced a potent vascular normalizing effect at a sub MTD (maximum tolerated dose) and showed its ability to improve intra-tumoral drug delivery and synergize chemotherapy, which confirms the reliability of zFXVP and implicates the potential application of PF-502 in clinical practice as an adjuvant vascular normalization drug. Overall design: RNA-seq was performed in HUVEC cells treated the following day with either vehicle(DMSO) or PF-502(0.15µM) for 12hrs