High Density Cells (IMAGE) Georgetown University Medical Center Caption Researchers noticed that cancer cells crowded back-to-back -- high density -- were less effective at invading cancer-free tissue than cells grown in a low density -- less crowded -- environment. Credit Courtesy Ghada M. Sharif/Georgetown Usage Restrictions With credit, please. License Licensed content 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.