Natural Killer Cells, Shown in Green, are Attacking a Mouse Tumor (video) The Ottawa Hospital Share Print E-Mail Loading video... Caption Natural Killer cells, shown in green, are attacking a mouse tumor. These often-overlooked cells may be key to cancer immunotherapy. Blood vessels are shown in blue. Credit Dr. Michele Ardolino and Dr. Brian Weist Usage Restrictions For use only in conjunction with stories about this research. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.