As a Grade 10 student in Montreal, Quebec, Catherine O’Brien experienced an “aha” moment. It was Career Day and, with an unlimited choice of occupational options to choose from, she chose to observe a female surgeon. This deﬁning experience put young Catherine on a path that would forever change the course of her life and the lives of countless cancer patients.
Years later, as a surgical resident, Dr. O’Brien lost her father and then an aunt to cancer, strengthening her resolve and fueling her relentless pursuit to ﬁnd new treatments for this disease.
Eventually, as a Senior Scientist and Surgeon at Princess Margaret Cancer Centre, specializing in gastrointestinal cancer, Dr. O’Brien and her team were trying to unlock the secret to why certain types of colorectal cancer seemed resistant to chemotherapy. In 2020, she attended a talk being given by a visiting surgeon who described cellular mechanisms driving a survival strategy in mouse embryos, not unlike the hibernation we associate with bears.
That was “aha” moment number two.
Dr. O’Brien explains: “Something clicked for me whenI heard that talk. Could the cancer cells be using this hibernation-like mechanism to evade chemotherapy?” Her suspicions proved correct. Soon, cancer cells were discovered to enter this protective state during chemo, only to emerge and grow later. These ﬁndings also seem to apply to certain leukemia, breast cancer, and prostate cancer cells when treated with chemotherapy. “I think that there’s more to be learned about this, but we now know for a fact that, in colorectal cancer, if you keep somebody on chemotherapy for a long period, over time they’re going to lose that response,” she says.
From that initial Career Day to the present day, Dr. O’Brien’s passion and commitment have never wavered. “Everybody involved in research is working together to try and push things forward. That sense of community and collaboration that you have at The Princess Margaret and UHN, pushing to see something that changes the outcomes for patients, makes this such a great place to work.”
“Everybody involved in research is working together to try and push things forward. That sense of community and collaboration, pushing to see something that changes the outcomes for patients, makes [The Princess Margaret] such a great place to work.”
Breakthroughs that have been driven by creativity at The Princess Margaret