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Yale Study Identifies Causes of Cancers

Yale Public Health Magazine, Yale Public Health: Fall 2022
by Matt Kristoffersen


A team of Yale-led researchers can now quantify the factors causing changes in DNA that contribute most to cancer growth in tumors of most major tumor types.

In a paper published in Molecular Biology and Evolution, the researchers said their novel molecular analysis approach brings clarity to a long-standing debate over how much control humans have over developing cancer across time.

Looking at instances of specific genetic mutations can reveal the extent to which preventable exposures like ultraviolet light caused tumor growth in 24 cancers, said Jeffrey Townsend, PhD, the Elihu Professor of Biostatistics in the department of biostatistics at YSPH.

“We can now answer the question—to the best of our knowledge—‘What is the underlying source of the key mutations that changed those cells to become a cancer instead of remaining normal tissue?’” he said.

Some of the most prevalent cancers in the United States are known to be highly preventable by human decisions. Skin cancers like melanoma emerge in large part because of prolonged exposure to ultraviolet light, and lung cancers can often be traced back to tobacco use. But scientists have long struggled to gauge how much any individual’s tumor developed as a result of preventable actions compared with aging or “chance.”

Previously, scientists have shown that they can reliably predict how certain factors cause specific mutations that alter the genome in tissues. By combining this knowledge with a method that quantifies the contribution of each mutation to cancer, Townsend and his colleagues showed the specific percentage of the blame to be assigned to known and unknown but identified factors in the emergence of cancer.

“That gives us the last puzzle piece to connect what happened to your genome with cancer,” he explained. “This is really direct: We look in your tumor, and we see the signal written in your tumor of what caused that cancer.”