Dll4-notch signalling blockade synergizes combined ultrasound-stimulated microbubble and radiation therapy in human colon cancer xenografts

PLoS One. 2014 Apr 15;9(4):e93888. doi: 10.1371/journal.pone.0093888. eCollection 2014.


Tumour vasculature acts as an essential lifeline for tumour progression and facilitates metastatic spread. Novel vascular targeting strategies aiming to sustain vascular shutdown could potentially induce substantial damage, resulting in a significant tumour growth delay. We investigated the combination of two novel complementary vascular targeting agents with radiation therapy in a strategy aiming to sustain vascular disruption. Experiments were carried out with delta-like ligand 4 (Dll4) blockade (angiogenesis deregulator) treatment administered in combination with a radiation-based vascular destruction treatment in a highly aggressive well-perfused colon cancer tumour line implanted in female athymic nude mice. Tumours were treated with permutations of radiation, ultrasound-stimulated microbubbles (USMB) and Dll4 monoclonal antibody (mAb). Tumour vascular response was assessed with three-dimensional power Doppler ultrasound to measure active flow and immunohistochemistry. Tumour response was assessed with histochemical assays and longitudinal measurements of tumour volume. Our results suggest a significant tumour response in animals treated with USMB combined with radiation, and Dll4 mAb, leading to a synergistic tumour growth delay of up to 24 days. This is likely linked to rapid cell death within the tumour and a sustained tumour vascular shutdown. We conclude that the triple combination treatments cause a vascular shutdown followed by a sustained inhibition of angiogenesis and tumour cell death, leading to a rapid tumour vascular-based 'collapse' and a significant tumour growth delay.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Death
  • Cell Line, Tumor
  • Colonic Neoplasms / diagnostic imaging
  • Colonic Neoplasms / metabolism*
  • Colonic Neoplasms / radiotherapy
  • Disease Models, Animal
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Membrane Proteins / metabolism*
  • Mice
  • Microbubbles*
  • Platelet Endothelial Cell Adhesion Molecule-1 / metabolism
  • Receptors, Notch / metabolism*
  • Signal Transduction* / drug effects
  • Tumor Burden
  • Ultrasonography, Doppler, Color
  • Xenograft Model Antitumor Assays


  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Platelet Endothelial Cell Adhesion Molecule-1
  • Receptors, Notch
  • delta protein

Grant support

This work was supported by the Terry Fox Foundation through a program project grant “Ultrasound for Cancer Therapy”. Dr. Gregory Czarnota is a clinician-scientist and is supported by a CCO Research Chair in Experimental Therapeutics and Imaging. Dr. Stanley Liu is a clinician-scientist and is supported by an OICR (Ontario Institute of Cancer Research) early stage investigator award and acknowledges the support of PCC (Prostate Cancer Canada). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.