Japanese immunologist Tasuku Honjo, a winner of this year's Nobel Prize in physiology or medicine, gave his Nobel lecture Friday in Stockholm, projecting that many more cancers may be treated by immunotherapy in the not-so-distant future.

"Someday, I don't know whether it's 2030 or not, cancer may not completely disappear but be controlled by immunotherapy. Cancer may become one of the chronic diseases," said Honjo, at the Karolinska Institute, following a lecture by American immunologist James Allison, who shared the prize with Honjo.

"You still have a tumor, but no growth. That's OK, especially for elderly people. You can keep your quality of life," he said.

The 76-year-old professor and deputy director general at the Kyoto University Institute for Advanced Study started his research on the immune system in earnest during the 1970s after doing his fellowship at the Carnegie Institution of Washington in Baltimore and at the National Institutes of Health in Bethesda, both in Maryland.

Humans and other animals have innate immunity and acquired immunity, with the latter producing immunological memory as a mechanism to avoid getting the same infectious disease twice.

Although cancer cells used to be the body's own cells, they become recognized as "foreign" by the immune system because of accumulated mutations, several hundred to several thousand times of normal cells, through repeated proliferation, according to Honjo's research.

However, cancer cells sometimes find ways to evade attacks of the immune system by using molecules on certain immune cells called checkpoints.

PD-1, discovered by Honjo in the early 1990s, is a checkpoint protein on the surface of T-cells that helps keep T-cells from attacking other cells, cancer or normal, when it attaches to another protein PD-L1. Some cancer cells are known to possess large amounts of PD-L1.

Honjo's discovery led to the development of Opdivo, a drug that can block that binding and boost the immune response against cancer cells.

Following successful clinical trials in the United States and Japan, Opdivo, a PD-1 immune checkpoint inhibitor, received regulatory approval in 2014.

"Acquired immunity is critical...this must be the bonus of evolution," Honjo said.

Meanwhile, treatment by weakening the braking function is effective, but it can cause autoimmune diseases as adverse reactions, his study also showed.

Nobel lectures by the year's prize winners are major events during the Nobel Week, and Honjo said in Japan prior to departing to Stockholm, "It was the most difficult task in the process of preparation (for the Nobel Week), as it covers a wide variety of issues including how I started the award-winning research as well as future outlook."

Honjo is scheduled to attend the award ceremony and Nobel banquet on Monday, as well as the royal banquet at the royal palace on Tuesday.

Honjo and Allison were awarded the prize for their discovery of cancer therapy by inhibition of negative immune regulation.