New discovery about moles may lead to treatment for skin cancer

IRVINE, Calif. — While most moles will turn out to be harmless, their ties to skin cancer still remain. A new study looking at how these tiny tumors form finds moles stop growing after reaching a certain size. This occurs despite having cancer-associated gene mutations and researchers say that discovery could lead to a new treatment for preventing skin cancer.

A mole is a benign, or non-cancerous, pigmented tumor. The American Cancer Society says these growths usually form during childhood or when a person becomes an adult. Babies are rarely born with a mole. The vast majority of these moles never go on to cause problems, but rare cases can evolve into melanoma.

A team from the University of California, Irvine believe the limitations of mole growth can point scientists towards a way to control cell growth in the body. Their study finds mutations that trigger the protein made by BRAF genes may contribute to the onset of skin cancer. Despite this connection, these mutations also commonly form harmless moles.

“Exploring why moles stop growing might lead us to a better understanding of what goes wrong in skin cancer,” says lead author Roland Ruiz-Vega in a media release.

Of mice and moles

Researchers have theorized the stress of rapid cell growth may play a role in stopping moles from getting too big. This process is called oncogene-induced senescence (OIS) and scientists are still working to prove if this connection is real.

Image showing the progression of pigmented moles in the paw of a mouse. (Credit: Rolando Ruiz-Vega and Emaad Razzak (CC BY 4.0))

In this study, researchers focused on “senescence,” which are the changes cells go through as they age. The UC Irvine team examined BRAF mutations in numerous moles found on mice. Using single-cell RNA sequencing to compare moles with normal skin, the team finds moles are no more senescent than normal skin cells. The cells also don’t have any significant differences in their genes which would back up the idea OIS controls their growth.

Instead, the study’s computer models suggest that mole cells actually communicate with each other after reaching a certain size. This communication also occurs in normal cell tissue which helps the body maintain its size.

“Our results suggest that moles stop growing as a result of normal cell-to-cell communication, not as a response to stress from cancer genes, potentially changing the way we think about skin cancer,” explains senior author Arthur Lander. “This work paves the way for further research into the mechanisms that control skin cell growth, with the aim of better understanding what goes wrong to cause skin cancer and ultimately developing new treatments to help prevent the disease.”

The study appears in the journal eLife.

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