Scientists are testing a new type of immune cell therapy that could help patients with osteosarcoma, a serious bone cancer that often comes back or spreads. Researchers created special immune cells called CAR T cells that are designed to recognize and attack cancer cells. In laboratory and animal tests, these cells successfully eliminated tumors. This research is still in early stages, but it offers hope for patients whose cancer doesn’t respond to current treatments. The next step is testing this therapy in actual patients to see if it works as well in real life as it does in the lab.

The Quick Take

  • What they studied: Whether specially designed immune cells (called FOLR1-CAR T cells) can effectively kill osteosarcoma cancer cells in laboratory and animal models
  • Who participated: This was preclinical research using cancer cell samples from patients, cancer cell lines grown in labs, and mice with human tumors. No human patients were involved in this particular study
  • Key finding: The specially designed immune cells successfully attacked and eliminated osteosarcoma tumors in all tested models, including both localized tumors and cancers that had spread to other parts of the body
  • What it means for you: This research suggests a potential new treatment option for patients with aggressive bone cancer, especially those whose cancer has returned or spread. However, this is still early-stage research, and human clinical trials are needed to confirm safety and effectiveness

The Research Details

This was a preclinical laboratory study, meaning researchers tested their approach in test tubes and animal models before considering human trials. The team first examined tumor samples from osteosarcoma patients to understand which proteins were present on the cancer cells. They identified a protein called FOLR1 that appeared on most osteosarcoma cells, making it a good target for attack.

The researchers then created special immune cells called CAR T cells that were programmed to recognize and attack cells displaying the FOLR1 protein. They tested these cells in multiple ways: first in test tubes against cancer cells, then in mice that had human osteosarcoma tumors implanted in them. They tested both localized tumors (in one spot) and metastatic tumors (cancer that had spread to multiple locations).

This multi-step approach allowed researchers to gather evidence that their approach was safe and effective before moving toward human testing.

Osteosarcoma is a particularly aggressive cancer that often returns or spreads despite current treatments like surgery and chemotherapy. CAR T cell therapy represents a completely different approach—using the body’s own immune system as a weapon against cancer. By targeting FOLR1, which appears on most osteosarcoma cells but not on many healthy cells, this therapy may be able to attack cancer while minimizing damage to normal tissue. This preclinical work provides the scientific foundation needed to justify testing in human patients.

This study provides solid preclinical evidence because it used multiple testing approaches (cell cultures, patient samples, and animal models) and examined both localized and metastatic disease. The researchers also characterized FOLR1 expression across many different osteosarcoma samples, showing the target is consistently present. However, this is laboratory research only—animal studies don’t always predict human results. The actual effectiveness and safety in human patients remains unknown and will require clinical trials to determine.

What the Results Show

The FOLR1-CAR T cells showed strong activity against osteosarcoma in all tested scenarios. In laboratory tests, the cells successfully recognized and killed osteosarcoma cancer cells. When tested in mice carrying human osteosarcoma tumors, the CAR T cells achieved complete tumor elimination in both localized tumors and cancers that had spread to multiple sites.

The researchers also tested the cells against patient-derived samples—actual tumor tissue taken from osteosarcoma patients—and found the same strong anti-tumor activity. This is particularly important because it suggests the cells might work against real patient tumors, not just laboratory-grown cancer cells.

The FOLR1 protein target was found in the vast majority of patient tumor samples examined, suggesting that most osteosarcoma patients could potentially benefit from this therapy. The cells showed robust activation, meaning they responded strongly when encountering their target.

The research demonstrated that FOLR1 is consistently expressed across different osteosarcoma cell lines and patient samples, making it a reliable target. The CAR T cells worked effectively against both standard laboratory cancer cell lines and more complex patient-derived models that more closely resemble actual tumors. The therapy showed promise against both localized disease and metastatic disease (cancer that had spread), which is important since metastatic osteosarcoma is particularly difficult to treat.

CAR T cell therapy has shown success against certain blood cancers, but solid tumors like osteosarcoma have been more challenging to treat with this approach. This research adds to growing evidence that CAR T cells can be effective against solid tumors when the right target is identified. The focus on FOLR1 is novel for osteosarcoma treatment, though this protein has been studied as a target in other cancer types. The comprehensive characterization of FOLR1 expression in osteosarcoma provides new information that wasn’t previously well-documented.

This study only tested the therapy in laboratory conditions and animal models—it has not been tested in human patients yet. Animal studies don’t always translate to human results due to differences in immune systems and tumor biology. The study doesn’t address potential side effects that might occur in humans, such as immune-related complications. The long-term durability of the CAR T cells and whether tumors might develop resistance over time remains unknown. Additionally, the study doesn’t compare this approach to current standard treatments, so we don’t yet know if it’s better than existing options.

The Bottom Line

Based on this preclinical research, FOLR1-CAR T cell therapy appears promising enough to warrant human clinical trials in osteosarcoma patients. The researchers are already moving forward with early-phase trials at Fred Hutch Cancer Center and Seattle Children’s Hospital for patients with relapsed or refractory osteosarcoma (cancer that has returned or doesn’t respond to standard treatment). Patients with aggressive osteosarcoma, particularly those whose cancer has returned or spread, should discuss with their oncologist whether participation in these clinical trials might be appropriate. Confidence level: Moderate—this is promising preclinical evidence, but human data is needed.

This research is most relevant to patients with osteosarcoma, particularly those with metastatic disease or cancer that has returned after initial treatment. Families of osteosarcoma patients should be aware of this emerging therapy option. Oncologists treating osteosarcoma should monitor the clinical trial results. This research is less immediately relevant to patients with other cancer types, though some may have FOLR1-expressing tumors. Healthy individuals don’t need to take action based on this research.

Clinical trials are just beginning, so it will likely be several years before we know if this therapy is safe and effective in human patients. Even if trials are successful, it could take additional time for regulatory approval and wider availability. Patients interested in this therapy should discuss clinical trial timelines and enrollment with their medical team.

Want to Apply This Research?

  • If enrolled in a FOLR1-CAR T cell trial, track tumor markers (if applicable), imaging results, and any side effects or symptoms weekly using the app’s symptom and appointment tracking features
  • Users interested in this therapy should use the app to schedule consultations with their oncology team to discuss clinical trial eligibility, set reminders for trial-related appointments, and document questions about CAR T cell therapy to discuss with their doctor
  • For patients in clinical trials, use the app to maintain a detailed log of any side effects, energy levels, and overall wellness. Track imaging results and lab work dates. Create reminders for follow-up appointments and document conversations with the medical team about trial progress

This research describes preclinical laboratory and animal studies only—no human patients have been treated with this therapy yet. These results do not represent proven treatments and should not be used to make medical decisions. Clinical trials are underway to test this approach in humans. If you or a loved one has osteosarcoma, discuss all treatment options, including potential clinical trial participation, with your oncology team. This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.