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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.

More about Dr. Bullman

How beautiful images can advance immunotherapy

They say a picture is worth 1,000 words.

In the case of MD Anderson’s immunotherapy platform, part of the James P. Allison Institute, a picture generated by spatial omics technology provides a wealth of information to bring immunotherapy to more patients.

Immune checkpoint inhibitors can treat a variety of cancers, but patients respond differently to these combination therapies based on their unique tumor microenvironment, which is made up of many cell types, including:

tumor cells
immune cells
fibroblasts
blood vessels
other cellular components

The immunotherapy platform uses breakthrough imaging and bioinformatics tools to paint a clear picture of the tumor microenvironment before and after immunotherapy treatment. This allows clinicians and researchers to see which cell types are present within the tumor microenvironment and how the cell types change after treatment is given. These data help researchers develop more personalized strategies to target specific cell subsets and improve responses for future patients.

We spoke with Sonali Jindal, M.D., associate director of the immunotherapy platform, to understand how these beautiful images are advancing immunotherapy treatments.

What is spatial omics, and why does it matter?

Spatial omics refers to advanced molecular techniques that analyze biological molecules within their exact location in tissue samples, creating snapshots of the tumor microenvironment. This allows researchers to see the distribution of genes and proteins being expressed, different cell-states and cell-to-cell interactions at the time the sample was collected.

The tumor microenvironment is an ecosystem that includes tumor and immune cells, blood vessels, fibroblasts and signaling proteins in and around a tumor, many of which have their own unique functions and interactions with each other, creating unique cell neighborhoods. Researchers have learned that these neighborhoods can affect whether immune cells are able to recognize and attack cancer cells and influence a tumor’s resistance to treatment.

How does the immunotherapy platform utilize spatial omics?

The immunotherapy platform aims to evaluate immune responses in patients in order to understand which specific therapies or combination therapies will need to be given so that all patients can benefit from immunotherapy. Our platform collects samples, including tumor and blood samples, for immune monitoring from patients enrolled in immunotherapy studies at MD Anderson. More than 5,000 patients have enrolled from over 100 clinical studies across various cancer types.

The samples are carefully tracked and analyzed by a collaborative network of clinicians, physician-scientists and bioinformaticians who can provide real-time monitoring of patients enrolled in clinical trials. Spatial omics is a critical part of that analysis.

How do you create these beautiful images?

We use imaging to gain detailed information about the tumor microenvironment from these samples. Each unique type of cell has certain targets that can be tagged with a marker, usually an antibody or probe. These targets are stained using fluorescent dyes.

It works similar to “paint by number” instructions: each color corresponds to a specific target being studied. Advanced imaging tools then capture these colored sections, mapping out where each cell type or molecule is located.

For the last 50 to 60 years, it was only possible to color one or two markers on a given sample, which provided very basic information on a small scale. Even when researchers added up to nine color markers at a time, it still limited the amount of information that could be generated, given the complex environment.

Fortunately, we have new technology that significantly improves our depth of analysis. For example, CODEX (CO-Detection by indEXing) technology allows simultaneous image staining of dozens of proteins, cells and other targets in a single tumor sample. This technology also attaches a unique barcode to each antibody in order to track and quantify each target.

We want to make sure that we’re able to accurately detect the biologically relevant markers within the tumor microenvironment so that we can integrate all of the data to understand the cell-to-cell interactions and the interactions of specific markers. The data from these studies provide information about why some patients respond – or don’t respond – to treatment and which specific markers need to be targeted with new treatments so that immunotherapy can lead to clinical benefit for more patients.

How does the platform use these images to guide patient care?

The immunotherapy platform provides detailed datasets regarding the tumor microenvironment across thousands of patients, enabling researchers to focus in on specific cell subsets or molecular targets that may be important for the development of new therapies or the selection of specific patient groups for immunotherapy treatments.

We at the immunotherapy platform are very involved in studying each sample, with analyses of hundreds to thousands of molecular markers using various “omic” assays, to determine how cells are responding to treatments, and defining the specific cellular and biologic pathways that drive immune response to eliminate tumor cells.

This allows researchers to generate road maps of the different cellular interactions and neighborhoods involved in various types of cancer response or resistance to immunotherapy.

Generating and analyzing these comprehensive images is no easy task, but it is one that I consider paramount to my role. It is a big privilege for all of us to be able to do this at MD Anderson’s truly collaborative environment, where clinicians and researchers work together so closely. These beautiful pictures are a way to show the impact of immunotherapy so patients can see and understand what can be done for them. It’s all about helping patients. That is what the platform strives for.

Learn about research careers at MD Anderson.

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