Core Needle Biopsy-Derived Organoids for Docetaxel Sensitivity Assessment in HR-Positive/HER2- Negative Breast Cancer: Exploratory Implications of Morphology and Treatment-Induced TUBB3 Dynamic Patterns

Breast cancer is not a single disease but a collection of different conditions, each behaving in its own way. Doctors sort these conditions into groups based on specific proteins found on the surface of the cancer cells. One of the most common groups is called hormone receptor-positive and HER2-negative. These cancers grow because of natural hormones in the body, but they do not have a specific protein called HER2 that drives more aggressive growth. For patients with this type of cancer, doctors often recommend a treatment before surgery known as neoadjuvant chemotherapy. This approach aims to shrink the tumor early on. A common drug used in these treatments is docetaxel, which works by freezing the tiny internal scaffolding that cells need to divide and grow. However, a major challenge remains: this drug does not work equally well for everyone. Some patients see their tumors shrink dramatically, while others see little to no change. Because the current methods for predicting who will respond are limited, many patients undergo a grueling treatment that may not help them, or worse, they might miss out on a therapy that could have worked.

To solve this puzzle, a team of researchers in China turned to a technique that brings a patient's own cancer into the laboratory for a direct test. They focused on a specific type of tissue sample called a core needle biopsy. This is the small piece of tissue doctors take with a hollow needle to diagnose cancer in the first place. Usually, this sample is just enough to identify the disease, and the rest is discarded or used for standard testing. The researchers asked a simple but difficult question: could they use this tiny, precious piece of tissue to grow a living model of the patient's tumor? They wanted to see if they could take these small samples, grow them into three-dimensional clusters of cells in a dish, and then test the drug docetaxel on them before the patient even started treatment. If successful, this would create a personalized platform to see how a specific patient's cancer might react to the medicine, offering a glimpse into the future of treatment decisions.

The team worked with three women who had been diagnosed with the hormone-positive, HER2-negative type of breast cancer. They collected the core needle biopsy samples from each woman before any chemotherapy began. In the laboratory, the researchers carefully processed these tiny tissue fragments. They washed the samples and placed them into a special nutrient-rich gel that mimics the environment inside the human body. Over the course of a few weeks, the tissue fragments began to reorganize themselves. Instead of spreading out flat like cells in a traditional petri dish, they curled up into tight, round balls. These structures, which the scientists call organoids, looked and acted like miniature versions of the original tumors. The researchers watched them grow, passed them into new dishes to ensure they could survive over time, and even froze them down to see if they could be brought back to life later. All three samples successfully grew into these living models, proving that the tiny biopsy pieces were enough to create a robust testing system.

Once the models were established, the researchers needed to be sure they were truly representing the original patients. They compared the new lab-grown balls to the original tumor tissue taken from the women's bodies. Under a microscope, the shapes and structures of the cells in the lab models matched the original tumors very closely. They also checked the genetic code of the cells. The mutations found in the lab-grown cells were the same ones found in the patients' original cancers. Furthermore, the lab models kept the same protein markers as the original tumors, remaining positive for hormone receptors and negative for the HER2 protein. This confirmed that the models were faithful copies, retaining the unique biological identity of each patient's disease. This fidelity is crucial because it means any test done on the model is likely to reflect what would happen inside the patient.

With the models ready, the team began the real experiment: testing the drug docetaxel. They exposed the three different sets of organoids to varying amounts of the drug to see how they reacted. The results were striking because each patient's model reacted in a completely different way, mirroring the diverse experiences seen in real-world treatment. The first patient's cancer model showed a strong resistance to the drug. Even when exposed to high doses, the tiny balls of cells remained intact and continued to grow, showing very little sign of damage. This matched the patient's actual clinical outcome, where the cancer did not respond well to the treatment. The second patient's model showed a middle-ground response. The cells were damaged by the drug, but not completely destroyed. The balls of cells shrank in size as the dose increased, but they did not fall apart entirely. This corresponded to the patient's actual experience of a partial response to the therapy. The third patient's model was highly sensitive. When the drug was introduced, the cells lost their structure quickly. The tight balls fell apart, and the individual cells scattered and died. This dramatic collapse matched the patient's excellent clinical response, where the cancer shrank significantly.

To understand exactly what was happening inside the cells, the researchers looked at two specific biological markers. One was a protein called Ki67, which acts as a sign that cells are actively dividing. In all three cases, the drug caused the levels of this protein to drop, indicating that the cells were slowing down their growth. The second marker was a protein called TUBB3, which is part of the cell's internal scaffolding that the drug targets. The researchers found that the behavior of this protein changed in interesting ways depending on the drug's effect. In the resistant model, the cells kept their structure and the TUBB3 protein remained high, suggesting the cells had found a way to ignore the drug's attack. In the sensitive model, the drug caused the cells to fall apart, and the levels of this protein dropped as the structure collapsed. These changes provided a deeper look at why some cells survived and others did not, offering clues that go beyond simply counting how many cells are left alive.

The study concludes that it is possible to grow living models of breast cancer from the tiny samples taken during a routine biopsy. These models can be grown, frozen, and tested with drugs like docetaxel. The results from these tests showed a clear pattern: the models reacted in ways that closely matched the actual outcomes of the patients they came from. The resistant tumors stayed strong, the sensitive ones fell apart, and the intermediate ones showed a mix of both. While the researchers note that this is an early exploration with a small number of patients, the findings suggest a promising path forward. By combining the measurement of cell survival with the observation of how the cells change shape and how their internal proteins behave, doctors might one day be able to predict with greater accuracy which patients will benefit from specific chemotherapy drugs. This approach does not replace the need for larger studies, but it offers a tangible, working method to move toward truly personalized cancer care, where treatment is chosen based on how a patient's specific tumor is likely to respond.