Three scientists who made important discoveries about how cells sense and adapt to different oxygen levels have won the Nobel Prize in physiology or medicine, in the first announcement of Nobel winners for 2019.

William G. Kaelin Jr. of the Dana-Farber Cancer Institute and Harvard University, Peter J. Ratcliffe of Oxford University and the Francis Crick Institute and Gregg L. Semenza of Johns Hopkins University were jointly awarded the prize.

"The seminal discoveries by this year's Nobel laureates revealed the mechanism for one of life's most essential adaptive processes," the Nobel Assembly at Sweden's Karolinska Institute said.

The scientists studied hypoxia — low oxygen levels — and while many people might know about that condition because of its link to high altitude, Ratcliffe has called hypoxia "an important component of many human diseases including cancer, heart disease, stroke, vascular disease, and anemia."

The three physicians "found the molecular switch that regulates how our cells adapt when oxygen levels drop," said Randall Johnson, a member of the Nobel Committee.

"Cells and tissues are constantly experiencing changes in oxygen availability," Johnson said. "As an embryo grows and develops, as muscles work, the oxygen available changes as the tissues themselves change. Cells need a way to adjust to the amount of oxygen they have, while still doing their important jobs."

Johnson added, "Scientists often toss around this phrase 'textbook discovery.' But I'd say this is really a textbook discovery."

The committee said the discoveries are of fundamental importance for physiology and could blaze the trail for new strategies to fight anemia, cancer and many other diseases.

"We make knowledge. That's what I do as a publicly funded scientist," Ratcliffe said by phone in an interview with the Nobel Committee. And he added that he could not have predicted the impact his work would have.

"It is important that scientists have the courage, and are allowed to derive knowledge for its own sake — i.e., independent of the perceived value at the point of creation. And the history of science tells us over and over again that the value of that knowledge can increase" in a number of random and unpredictable ways.

The prize of 9 million Swedish crowns ($913,000) will be shared equally by the three winners.

Kaelin was born in New York and received an M.D. from Duke University. He did his specialist training in internal medicine and oncology at Johns Hopkins in Baltimore and at the Dana-Farber Cancer Institute in Boston.

Ratcliffe was born in Lancashire, United Kingdom, and studied medicine at Gonville and Caius College at Cambridge University and did his specialist training in nephrology at Oxford. He is the director of clinical research at the Francis Crick Institute in London, the director of the Target Discovery Institute in Oxford and a member of the Ludwig Institute for Cancer Research.

Semenza was born in New York. He obtained a Bachelor of Arts in biology from Harvard and his M.D./Ph.D. from the University of Pennsylvania, School of Medicine. He did his specialist training in pediatrics at Duke University. He is the director of the Vascular Research Program at the Johns Hopkins Institute for Cell Engineering.

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