Mark Lemmon, Penn Medicine (IMAGE) Children's Hospital of Philadelphia Caption Mark A. Lemmon, Ph.D., chair of Biochemistry and Biophysics at Penn Medicine, focuses on cell receptors in cancer. Credit Perelman School of Medicine at the University of Pennsylvania Usage Restrictions None 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.