HOUSTON, May 6 (UPI) -- A University of Texas study has contradicted previous research by finding early life exposure to ultraviolet-A light does not cause melanoma in a fish model.
Scientists at the university's MD Anderson Cancer Center said their finding reinforces untraviolet-B light as the culprit since the fish model has been the only animal model to indicate a connection between exposure to UVA at a young age and later development of melanoma.
The data doesn't suggest UVA is harmless, said Professor David Mitchell, the study's lead author at the cancer center's department of carcinogenesis. "UVA is just not as dangerous as we thought because it doesn't cause melanoma."
The scientists said they exposed a hybrid form of the genus Xiphophorus -- more commonly known as platyfishes and swordtails -- to either UVA or UVB daily between their fifth and 10th day of life. The fish were then scored for melanoma 14 months later.
"We found UVB exposure induced melanoma in 43 percent of the 194 treated fish, a much higher rate than the 18.5 percent incidence in the control group that received no UV exposure," Mitchell said. But only 12.4 percent of 282 fish exposed to UVA developed the disease, which is not statistically different from the control group, he added.
The study appears in the early online edition of the Proceedings of the National Academy of Sciences.