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Moles and melanomas are both skin tumors that come from the same cell called melanocytes. The difference is that moles are usually harmless, while melanomas are cancerous and often deadly without treatment. published today in eLife Magazine, , Huntsman Cancer Institute researcher and (the U) assistant professor of dermatology and oncological sciences, explains how common moles and melanomas form and why moles can change into melanoma.

Melanocytes are cells that give color to the skin to protect it from the sun’s rays. Specific changes to the DNA sequence of melanocytes, called BRAF gene mutations, are found in over 75% of moles. The same change is also found in 50% of melanomas and is common in cancers like colon and lung. It was thought that when melanocytes only have the BRAFV600E mutation the cell stops dividing, resulting in a mole. When melanocytes have other mutations with BRAFV600E, they divide uncontrollably, turning into melanoma. This model is called “oncogene-induced senescence.”

“A number of studies have challenged this model in recent years,” says Judson-Torres. “These studies have provided excellent data to suggest that the oncogene-induced senescence model does not explain mole formation but what they have all lacked is an alternative explanation—which has remained elusive.”

With help from collaborators across Huntsman Cancer Institute and the University of California San Francisco, the study team took moles and melanomas donated by patients and used transcriptomic profiling and digital holographic cytometry. Transcriptomic profiling lets researchers determine molecular differences between moles and melanomas. Digital holographic cytometry helps researchers track changes in human cells.