The Researcher
University of British Columbia postdoctoral researcher Stephen Yiu Chuen Choi
The Challenge
Determining if lactic acid plays a role in cancer spread
The Solution
Proof that lactic acid promotes rapid cancer cell growth and prevents immune cells from effectively fighting cancer
The Outcome
Development of a drug therapy capable of suppressing lactic acid and reducing cancer growth
Postdoctoral researcher works to fundamentally change the treatment of aggressive prostate tumours by focusing on suppressing lactic acid, a by-product generated by cancer cells, which has up until now largely been ignored
Novel drug is first to target lactic acid as a way to improve the immune system’s natural ability to stop cancer spread
After turning conventional wisdom on its head — by exploring the role that lactic acid plays in cancer cells even though scientists have long considered it a harmless waste product — University of British Columbia (UBC) researcher Stephen Yiu Chuen Choi is using his breakthrough discovery to develop a first-of-its-kind treatment for difficult-to-treat prostate cancers.
Choi — a postdoctoral cancer researcher under the supervision of Professors Christopher Ong and Yuzhuo Wang in the Department of Urologic Sciences at UBC — is working to fundamentally change the treatment of aggressive prostate tumours by focusing on suppressing lactic acid, a by-product generated by cancer cells that has up until now largely been ignored. For nearly a century, cancer researchers believed it served no purpose, but Choi has proved the opposite, that lactic acid actually promotes rapid cancer cell growth and prevents immune cells from effectively fighting cancer.
“I hypothesized that lactic acid might be worth investigating, and to my surprise, it ended up being quite important,” said Choi, whose experiments showed that lactic acid should be viewed as a critical immunosuppressive player.
Choi found that when lactic acid is excreted out of cancer cells, it creates a “tumour microenvironment” that is more acidic than other areas of the body. It is now widely recognized that this environment encourages the growth of blood vessels necessary to feed tumours. It also allows the cancer to spread to adjacent areas, increases resistance to common cancer treatments, and helps the cancer to spread to distant areas of the body, he explained. More importantly, lactic acid allows cancer to evade the immune system and continue growing unchecked.
Building on his discovery, Choi is now part of a team working to develop a drug therapy capable of suppressing lactic acid and thereby reducing cancer growth. The idea is that stopping the ability of cancer cells to secrete lactic acid will normalize the pH so that tumours won’t grow as aggressively, and the body’s natural anti-cancer immune response will be restored.
To identify chemical compounds that effectively stop lactic acid production in cancer cells, Choi is using a unique computer-based drug discovery platform that can quickly screen billions of chemical molecules to determine which ones are most effective at inhibiting the molecular protein responsible for lactic acid generation. Working with Vancouver-based industry partner LAST Innovations Ltd., the team has successfully narrowed the list to a small promising number and they expect to begin clinical trials in two to four years. The current focus is on developing small molecule cancer drugs — similar to aspirin — that can be produced at a low cost. 
“The best part is that this breakthrough is not limited to prostate cancer only, but will also be applicable to treating a wide variety of aggressive tumours, including liver, lung, and breast cancers,” Choi said.
The innovative research has earned Choi the Mitacs Award for Outstanding Innovation—Postdoctoral, which was presented at a ceremony at the National Arts Centre in Ottawa on November 22, 2022.
Choi credits Mitacs for introducing him to the industry side of research and for giving him the opportunity to get his hands wet when it comes to understanding intellectual property law and talking to investors. “Coming from academia, I’m more familiar with scientific hypotheses, experiments, and data,” he said. “Through Mitacs, I learned that there’s a lot more to it when it comes to direct product development. I was always interested in science but now I have the chance to do something useful with it.”
The Mitacs Award for Outstanding Innovation—Postdoctoral is presented to a Mitacs intern who has made a significant achievement in research and development innovation during their Mitacs-funded research.
Mitacs’s programs receive funding from valued partners across Canada. We thank the Government of Canada, the Government of Alberta, the Government of British Columbia, Research Manitoba, the Government of New Brunswick, the Government of Newfoundland and Labrador, the Government of Nova Scotia, the Government of Ontario, Innovation PEI, the Government of Quebec, the Government of Saskatchewan, and the Government of Yukon for supporting us to foster innovation and economic growth throughout the country.
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Mitacs Team
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