Beyond organoids: restoring the value of patient-derived two- dimensional colorectal cancer models

Colorectal cancer is a disease of the large intestine that remains one of the most common and deadly forms of cancer worldwide. To fight it effectively, scientists need to understand how individual tumors behave and which medicines might stop them. For decades, researchers have relied on growing cancer cells in flat layers on plastic dishes, known as two-dimensional cultures. These models are inexpensive and easy to use for testing new drugs, but they have a major flaw: they are very difficult to create directly from a patient's fresh tumor tissue. Often, the cells die before they can be studied, or they are overwhelmed by bacteria. In recent years, a different approach has gained popularity: growing tumors in tiny, three-dimensional clusters called organoids, or growing them inside special mice. While these methods work better, they are expensive and complex. The question remained whether the old, simple flat-culture method could be revived to work reliably for patients, offering a cheaper and faster way to study the disease without losing the unique characteristics of the individual tumor.

A team of researchers at the University Medical Center Rostock in Germany set out to answer this question by looking back at nearly a decade of work with colorectal cancer samples. They examined 158 tissue samples taken from 136 patients between 2015 and 2023. Some of these samples came directly from the patients' tumors, while others came from tumors that had been previously grown inside mice, a process that helps clean the tissue of bacteria and enriches the cancer cells. The researchers tested twelve different liquid environments, or media, to see which ones would allow the cancer cells to survive and multiply. These included older recipes containing animal serum and newer, carefully defined mixtures that contain no animal products but include specific growth factors. They also tested whether adding a specific chemical compound, known as a ROCK inhibitor, helped the cells stick to the dish and survive the stress of being moved from the body to the lab.

The results showed that the old ways of growing these cells were indeed inefficient, but the new methods changed the game. When the researchers used the newer, defined, serum-free media, the success rate jumped significantly compared to the older, serum-containing recipes. The addition of the ROCK inhibitor provided a further boost, turning failed attempts into successful ones in many cases. Perhaps most importantly, using tissue that had been grown in mice first proved to be a powerful strategy. Cultures derived from these mouse-grown tumors succeeded about 58 percent of the time, compared to only 39 percent for fresh tissue taken directly from patients. When the team used both approaches together—trying fresh tissue first and then falling back on the mouse-grown tissue if that failed—they were able to create a stable cell line from more than 80 percent of the specimens. This success rate is now comparable to the more expensive and complex three-dimensional organoid methods, suggesting that the simple, flat-culture model is once again a viable and efficient tool for precision medicine.

Despite these technical successes, the researchers found that they could not predict which tumors would grow and which would fail based on the patient's medical history or the specific genetic makeup of the cancer. They looked at factors such as the patient's age, the stage of the cancer, the size of the tumor, and specific genetic mutations, but none of these clues reliably indicated whether a culture would be successful. This is actually a positive finding for the scientific community, as it means the resulting collection of cell lines is not biased toward a specific type of patient or a particular genetic subgroup. The panel of cell lines represents the full diversity of colorectal cancer, making it a fair and representative resource for testing new treatments.

The study also uncovered a surprising link between the ability of a tumor to grow in a dish and the patient's outcome. Patients whose tumors successfully established a cell line in the lab tended to have shorter survival times compared to those whose tumors failed to grow, even after accounting for the stage of the cancer and whether the surgery removed all visible disease. The researchers suggest that tumors capable of thriving outside the body in a dish might be inherently more aggressive inside the body. However, they caution that this observation was not the main goal of the study and needs to be confirmed in larger groups of patients before any firm conclusions can be drawn.

Ultimately, this work demonstrates that with the right combination of modern, defined media, a helpful chemical additive, and a backup plan using mouse-grown tissue, scientists can now reliably create simple, two-dimensional cell lines from colorectal cancer patients. This approach offers a cost-effective and scalable way to study the disease and test drugs, without the need for complex three-dimensional structures or expensive animal models. The resulting collection of cell lines provides a broad and unbiased window into the disease, ready to help researchers develop better treatments for the diverse population of people affected by colorectal cancer.