Honjo, 76, was named to share this year's prize by the Nobel Assembly at the Karolinska Institute in Stockholm with James Allison, 70, of the MD Anderson Cancer Center at the University of Texas. Checkpoint therapy has now revolutionized cancer treatment and has fundamentally changed the way we view how cancer can be managed.
He said a member of his golf club, whom he did not know well, came up to him one day and thanked him, saying: "Thanks to your medicine".
"This important discovery has opened a whole new area of cancer treatment and we are proud of both Dr. Allison and Dr. Honjo's impactful research", said Janet Rossant, president and scientific director of the Toronto-based Gairdner Foundation.
They winners will receive their prize from King Carl XVI Gustaf at a ceremony in Stockholm on December 10, the anniversary of the 1896 death of Alfred Nobel, who created the prizes in his last will and testament.
Such a discovery led to the development of therapies in 2012 that proved to be incredibly effective in our ongoing effort to eliminate cancer. The "future of cancer treatment" According to Dr GK Rath, professor and head, BRA-Institute Rotary Cancer Hospital, AIIMS, "Immunotherapy is not the present of cancer care".
Medicine is normally the first of the Nobel Prizes awarded each year.
He leads the immunotherapy platform for MD Anderson's Moon Shots Program, which conducts immune monitoring by analyzing tumour samples before, during and after treatment, aiming to understand why these drugs work for some patients but not for others.
Allison was studying a protein (called CTLA-4) that is a critical brake for our immune system.
Honjo said, "I am pleased the very basic studies I have been carrying out since 1992 have been applied to clinical treatment as a new cancer therapy".
"I never dreamed my research would take the direction it has", he said in a statement on his university's website.
The announcement in Helsinki was the first of several prizes to be given out this week.
A ceremony at which the prizes are bestowed will be held December 10. A maximum of three laureates are selected.
The Nobel Prize for physics is set to be announced on Tuesday.
Honjo is the 26th Japanese person to win a Nobel Prize.
Among the numerous awards and honours that Honjo has received are the Order of Culture, the Robert Koch Prize and the Imperial Prize of the Japan Academy.