What is cancer spread, and how do we treat it?

Cancer becomes most dangerous when it spreads, or metastasizes, to other parts of the body. Despite decades of research, we still don’t fully understand how and why this happens. This month, we had the opportunity to sit down with Assistant Professor at the Hormel Institute and MCC researcher Eric Rahrmann, PhD to dive into the science behind cancer spread and discuss the latest innovations in predicting, preventing, and treating metastasis.

Be sure to join us for our Fireside Chat on August 20, where Dr. Rahrmann will be our special expert guest!

What brought you to the Hormel Institute, University of Minnesota?

I grew up in Byron, Minnesota, and my wife is from Fairmont, so in a way, this move was a homecoming for both of us. After nearly nine years living and working in the United Kingdom, most recently as a Senior Research Associate at Cancer Research UK at the University of Cambridge, we were ready to come back to be closer to family. Now, our daughter gets to grow up surrounded by grandparents, aunts, uncles, and cousins, and we get to be part of those everyday family moments we’d been missing. There’s something special about returning to the place that shaped you and being able to give back, both through my work and through the life we’re building here. The Hormel Institute offered the perfect professional match, world-class research facilities, a collaborative spirit, and an ideal location for building partnerships with places like Mayo Clinic and the University of Minnesota Twin Cities. It’s an environment where bold ideas have the resources and partnerships they need to become reality, a place where I can drive high-impact science while also putting down deep roots in the community I’ve always called home.

What does “cancer spread” mean?

When people talk about “cancer spread,” they’re usually referring to metastasis, the process where cancer cells break away from the original tumor, travel through the body, and start growing in new places. But here’s something most people don’t realize: the ability for cells to move and take up residence somewhere else isn’t unique to cancer. Our bodies use similar processes in other settings, even in normal, healthy biology, and in certain diseases like endometriosis or scleroderma. In cancer, this natural system gets hijacked. Tumor cells slip into the bloodstream or lymphatic system, survive the journey, and set up in a new organ, like the liver, lungs, or brain. Once there, they can behave differently than the original tumor, making them harder to detect, predict, and treat. More than a century ago, English surgeon Stephen Paget described this as the “seed and soil” hypothesis, cancer cells are like seeds, and they can only grow in certain soils that are just right for them. That image still resonates today and helps explain why understanding both the traveling cells and the environments they land in is key to stopping metastasis.

How is cancer spread typically treated?

Treating cancer once it has spread is one of the biggest challenges in medicine. That’s because each metastatic tumor can be different, not only from the original tumor, but from each other. A spot in the liver may respond to treatment in one way, while a spot in the brain or lung may respond very differently, depending on the local environment and the tumor’s genetic makeup. Right now, most treatments for metastatic cancer are systemic therapies, drugs that travel throughout the body, like chemotherapy, targeted therapy, hormone therapy, or immunotherapy. These aim to reach cancer cells wherever they’ve gone. In some cases, surgery or radiation is used to remove or shrink specific metastatic sites, especially if they’re causing symptoms. Even with precision medicine, where treatments are matched to specific genetic changes in the tumor, results aren’t always predictable. That’s partly because metastatic tumors can evolve over time, developing new traits that make them resistant to treatment. The good news is researchers, including many across the University of Minnesota, are tackling these challenges from new angles. For example, the UN-TIL initiative, led by MCC’s Branden Moriarity and Beau Webber, is advancing tumor-infiltrating lymphocyte (TIL) therapy, an approach that has already shown success in treating metastatic colorectal cancer. It’s a strong example of how collaboration between scientists, clinicians, and institutions can accelerate progress. By focusing directly on metastasis—studying how cancer cells travel, survive, and grow in new environments—we’re identifying strategies to block those steps before they cause harm, bringing us closer to treatments that can stop cancer’s spread entirely.

Are there any preventative measures that people can take to reduce the risk of cancer spread?

We can’t always prevent metastasis, but the best way to lower the risk is to catch and treat cancer early. That’s why staying up to date with recommended screenings, like mammograms, colonoscopies, or skin checks, is so important. For some cancers, doctors also use additional treatments before or after surgery, called neoadjuvant or adjuvant therapy, to target any cells that might already be on the move. Healthy habits can also make a difference for your overall cancer risk: eating a balanced diet, staying active, maintaining a healthy weight, avoiding tobacco, and limiting alcohol. Vaccines like the HPV vaccine can even prevent certain cancers from developing in the first place. Scientists, including many here at the University of Minnesota, are now exploring entirely new prevention strategies, from keeping cancer cells in a “dormant” state, to blocking the body from creating the supportive environments (sometimes called “pre-metastatic niches”) that help cancer grow in new places. While these approaches are still in research, the fact that we’re talking about stopping metastasis before it starts is a huge shift in thinking, and it’s opening the door to more ways to protect patients in the future.

How is your research advancing understanding of cancer spread and how we prevent, treat, and diagnose cancer?

Most people think of metastasis as something that only happens in cancer, but my lab’s research shows it’s a normal biological process that cancer has learned to exploit. In healthy situations, certain cells can break away, travel through the body, and settle into new tissues as part of repair or maintenance. In cancer, those same pathways get hijacked, letting tumor cells seed new tumors in distant organs. We focus on two of the deadliest cancer types, metastatic breast cancer and metastatic colorectal cancer, to understand exactly how and why cancer cells break away, travel, and take root elsewhere in the body.

A central theme of our work is studying the bioelectric properties of epithelial cells—these are the electrical signals that help control when and where cells move. We discovered that a single ion channel, which is like a tiny doorway in a cell’s outer wall, called NALCN, acts like a “gatekeeper” for this movement. When NALCN is working properly, it helps keep cell travel in check. We’ve learned that NALCN isn’t only important in cancer cells themselves; it also matters  in the surrounding cells that support a tumor.  When these support cells change, they can create conditions that make it easier for cancer to spread. We also discovered that NALCN has a new role in controlling primary cilia, tiny, antenna-like structures on cells that help them sense and respond to their surroundings. Working with  Dr. Sergio Gradilone at the Hormel Institute, a world expert on cilia biology, we’re studying how to block the “green lights” that let cancer cells spread, and how to strengthen the “red lights” that stop them. At the same time,, we’re exploring whether this biology could also be used to repair tissues, taking a process cancer uses and turning it into something that helps the body heal.

Metastasis is very complex. It involves many steps, cell types, tissues, and signals, so no single lab can solve it alone. That’s why I started the Minnesota Metastasis Research Network (MnMet), which brings together experts from the Hormel Institute, the Mayo Clinic, and the University of Minnesota Twin Cities. The Hormel Institute has played a key role in making this possible by providing the tools, partnerships, and shared vision we need.By combining expertise in genetics, immunology, imaging, computational biology, and clinical care, we can study every stage of how cancer spreads. Working together, we’re moving faster to create better ways to detect, prevent, and treat metastatic cancer.