4 questions with immunology researcher Susan Bullman

Susan Bullman, Ph.D., has studied bacteria and how it contributes to cancer for decades. Her research led her from her home in Ireland and eventually to MD Anderson and the James P. Allison Institute, where she serves as an associate member.

We asked Bullman four questions about her research and her career. Here’s what she had to say.

How did you get your start as a cancer researcher?

During my graduate studies in Ireland, I focused on understanding how bacteria contribute to gastrointestinal diseases, though I wasn’t working on cancer at the time. Around that period, the Human Microbiome Project was uncovering groundbreaking insights into how microbes influence human health and disease, including cancer. I was fascinated by the idea that these tiny organisms could profoundly impact complex diseases like cancer, shaping everything from its progression to treatment outcomes. I knew this was where I needed to direct my efforts — to explore the critical role these microbes play in cancer biology.

To pursue this, I realized I needed to step out of my comfort zone. I made the life-changing decision to move across the Atlantic. I worked at a few different U.S. institutes focused on cancer research and strengthened my understanding of the complex relationship between microbes and cancer. Eventually, I shaped the central focus of my research program: determining how the microbes within us influence cancer biology and uncovering new possibilities to improve patient outcomes.

You’ve been studying the human microbiota and cancer for over a decade. What most excites you about this area?

What excites me most is the incredible interplay between the human and microbial components of our bodies. For every human cell we have, there are approximately 1.3 microbial cells, and for every human gene, we have 150 microbial genes. This means our bodies are a remarkable union of human and microbial systems, working together in ways we are only beginning to understand. In microbiome science, we focus on how the microbial component impacts the human component — especially because the microbial component is malleable. We can modify and manipulate it, giving us a unique opportunity to influence health and disease.

In cancer biology, microbes are far from passive bystanders. They actively shape the tumor microenvironment, influence immune responses and even affect how a patient responds to therapy. If we can determine how these microbes contribute to cancer, it opens the door to entirely new therapeutic avenues. There’s immense potential to harness this knowledge to develop innovative, personalized diagnostics and therapies, and that’s what continues to inspire and push forward my work in this field.

What’s next for your lab?

Our lab is focused on uncovering how specific microbes infiltrate human tumors and alter the behavior of cancer. Our previous work has shown that these microbes not only infiltrate tumors but also interact with immune cells and cancer cells within the tumor microenvironment, contributing to poorer outcomes for patients. A major focus of our research is understanding why these microbes are associated with a worse prognosis and how they impact the way patients respond to cancer treatments.

To tackle these questions, we are adapting and applying advanced technologies like single-cell spatial transcriptomics and proteomics. These tools allow us to precisely map microbes within human tumors and investigate the mechanisms by which they help cancer grow and survive. By identifying microbial biomarkers and determining how these microbes interact with the tumor microenvironment, we aim to intercept these harmful interactions and develop new therapeutic strategies. Another key focus is on creating narrow-spectrum antimicrobials targeting Fusobacterium nucleatum, a microbe that contributes to colorectal cancer, with the goal of improving patient responses to current cancer treatments and reducing the risk for cancer relapse or metastases.

You joined MD Anderson last year. What about MD Anderson excites you most?

What excites me most is MD Anderson’s highly collaborative environment. There is a clear focus on asking: How can this work? How can these discoveries reach patients? The James P. Allison Institute exemplifies this approach, seamlessly transitioning groundbreaking discoveries from the lab to the clinic. Basic and translational researchers collaborate closely with clinical trialists, medicinal chemists, oncologists, and surgeons to maximize the potential for research to directly impact patients.

MD Anderson offers a truly unique environment to ensure that my research has a real-world impact. I want my work to be meaningful — I don’t want it to remain confined to the research lab. I want it to reach patients, where it can truly make a difference. MD Anderson is unparalleled in its ability to integrate research findings into the clinical setting, bridging the gap between discovery and patient care.

Having worked at major cancer centers across the U.S., I can confidently say that MD Anderson is uniquely positioned to transform research into action. Being part of this institution gives me the opportunity to move my work beyond the lab and into the clinic, where it can hopefully help patients with cancer — a mission that is deeply motivating.

Learn about research careers at MD Anderson.