When many people hear CAR T-cell therapy, they think about a treatment designed to address cancer. Recently, a new study done on mice models has suggested that an experimental form of CAR T-cell therapy could be used to treat patients with retinoblastoma. According to the National Cancer Institute (NCI), researchers injected “packaged” cells directly into tumors. Discover the full study findings published in Nature Cancer.

CAR T-Cell Therapy

According to the Dana-Farber Cancer Institute, CAR T-cell therapy is:

a form of immunotherapy that uses specially altered T cells — a part of the immune system — to fight cancer. A sample of a patient’s T cells are collected from the blood, then modified to produce special structures called chimeric antigen receptors (CARs) on their surface; when these CAR T cells are reinfused into the patient, the new receptors enable them to latch onto a specific antigen on the patient’s tumor cells and kill them.

However, the CAR T-cell therapy used in the Nature Cancer study is slightly different. First, researchers “packaged” T-cells into hydrogel, a type of biodegradable material. Next, they injected these packaged cells directly into tumors.

One huge concern for patients with retinoblastoma is blindness or complete vision loss. However, the study determined that this experimental treatment preserved vision while also completely destroying ocular tumors. Interestingly, the therapy still had a significant effect on advanced tumors.

Past treatments for retinoblastoma include radiation, chemotherapy, ophthalmic artery chemosurgery, and enucleation (removal of the affected eye). However, these treatments are both invasive and potentially dangerous; some have the potential to cause serious adverse reactions or even the development of additional cancers. Thus, packaged CAR T-cell therapy has the potential to be safer and less invasive.

Developing a New Therapy for Retinoblastoma

After CAR T-cell therapy was shown as potentially effective for neuroblastoma, researchers wondered if it might also show promise for retinoblastoma. In fact, it was so successful for neuroblastoma in mouse models that it is currently being evaluated in a clinical trial.

In both cancers, cancer and tumor cells produce GD2. Since this is not expressed on normal cells, or expressed in a very small capacity, it offers a treatment target. The therapy targets and finds GD2, then kills the cancer cells. However, the first round of CAR T-cell therapy for retinoblastoma was not incredibly effective. While the therapy shrunk the tumors, the tumors later regrew.

Next, researchers hypothesized that interleukin 15 (IL-15), which plays a role in the immune system, could create longer-lasting CAR T-cells. The researchers then engineered the experimental therapy to produce IL-15 when injected. Not only did this completely destroy the tumors in over 50% of mice models, but it stopped any tumors from re-growing.

Then, researchers made one last attempt to increase efficacy: packaging these newly engineered cells into hydrogel. As a result, the therapy would be extended-release. Once researchers tested the packaged therapy, it destroyed tumors in 100% of mice models and stopped tumors from re-growing. Additionally, the therapy stayed for an extended period in the area, which also stops regrowth.

Retinoblastoma

Although retinoblastoma is a rare ocular cancer, it is still the most common ocular cancer in children. Typically, retinoblastoma affects children at a much higher rate than adults, though it can still occur in adult patients. This cancer forms in the retina, a sensitive inner-eye lining. Retinoblastoma can affect one or both eyes. Additionally, without treatment, it can spread to other areas of the body. In some cases, genetic mutations cause retinoblastoma. In others, mutated nerve cells form a tumor, and doctors are not exactly sure of the cause.

Symptoms of retinoblastoma include:

• Ocular inflammation
• Eye redness
• Eyes that seem to look in different directions
• Whiteness in the pupil when a light is shone on it
• Squinting
• Eyelid pain and swelling
• Vision loss

Learn more about retinoblastoma.