Skin Stem Cells Producing Keratin 15 (IMAGE) Cold Spring Harbor Laboratory Caption Ras and DNp63a expression maintains the survival of the more mature Keratin 15-Expressing Stem Cells (red) but not other stem cells in the skin such as the more primitive nestin-producing stem cells (green). The Keratin-15 stem cells expressing Ras and DNp63a eventually transform into carcinoma cells. Credit Mills@CSHL Usage Restrictions image may only be used with appropriate caption or credit. 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.