When Dr. Dan Regan talks about his work in cancer research, he boils it down to a simple analogy known as the seed and soil theory. He wants to understand how cancer cells (seeds) know where to find welcoming locations to take root (soil). In science speak, Regan studies the tumor microenvironment and metastatic disease.
Regan trained as a veterinarian at the University of Georgia and is a board-certified pathologist. He then completed a Ph.D. in tumor immunology at Colorado State University. He recently received a faculty position at CSU following postdoctoral research at the Flint Animal Cancer Center.
His new research program at the FACC is based on the work of Stephen Paget, an English surgeon during the late 19th century who was the first to theorize that the microenvironment played an important role in the spread of cancer.
“When a plant goes to seed, its seeds are carried in all directions; but they can only live and grow if they fall on congenial soil. … While many researchers have been studying ‘the seeds,’ the properties of ‘the soils’ may reveal valuable insights into the metastatic peculiarities of cancer cases.”
– Stephen Paget
“During my doctoral studies in tumor immunology, I came across a paper from 2005 describing how cancer cells condition distant sites before metastasizing,” said Regan. “The paper cited the work of Stephen Paget that had been forgotten for more than 100 years. For me, it was a mind-blowing idea and quickly became my passion.”
At the same time, it also became personal when Regan’s father was diagnosed with cancer.
As Regan learned more about the tumor microenvironment, he discovered it was not well understood and a field ripe for exploration. After nearly a decade of study, Regan believes one key to combating metastatic disease is understanding how the primary tumor conditions the soil in distant locations. In both pets and people, metastatic disease continues to puzzle scientists and challenge clinicians. Once the cancer spreads, there are few treatment options. Regan is on a mission to change that fact.
His current projects include investigations relating to two highly metastatic cancer types. The first study focuses on breast cancer, which is the most common cause of female cancer mortality, with the majority of these deaths resulting from metastatic disease. While the initial response rate to tumor treatment can be up to 90 percent, recurrence is frequent, and the tumors that eventually spread are typically resistant to anti-cancer therapies. His study aims to understand changes within the host tissues/organs of metastatic sites that support this drug resistance, in hopes of identifying treatments that can prevent or reverse these changes and restore tumor cell drug sensitivity.
In a second study, Regan is on a quest to improve outcomes for patients diagnosed with osteosarcoma. Unfortunately, the prognosis for this disease has not changed in more than 25 years, primarily due to an inability to predict and therapeutically target lung metastasis, the most common site for the cancer to spread. This project hopes to define the critical elements of non-malignant host cells that promote this lung metastasis. He believes the results of this study will provide the foundation for future investigations to evaluate new therapies and identify patients who may be prime candidates for these treatments to slow or prevent metastasis.
“More than anything, I want to give hope to patients, both pets and people, with metastatic disease,” said Regan. “I’m grateful for the opportunity and ready to make an impact.”