Scientists have identified the role of a protein in the development of typically harmless moles on our skin into the dangerous melanoma skin cancer. Both moles and melanomas originate from melanin-producing cells (melanocytes) within the skin. The researchers found that lower level of protein called p15 may promote growth of moles into melanoma.The findings also revealed what keeps typical moles stop in their usual non-cancerous, no-growth state. Scientists have known for years that a mutation in the cell growth gene called BRAF makes them start growing, but until now did not understand why they stopped. “The BRAF mutation that stimulates the initial growth of moles also stimulates the production of a tumour suppressor protein, p15, which ultimately acts as a powerful brake on further cell division,” said study senior author Todd Ridky, assistant professor at Perelman School of Medicine at the University of Pennsylvania in the US. “It is this cell division that ultimately allows the transition from a normal mole into melanoma. When mole cells lose the p15 brake, cells can start dividing again and can progress into cancer,” Ridky noted.