CAR-T cell therapy, a groundbreaking form of personalized medicine, has revolutionized the treatment of certain blood cancers by genetically modifying a patient’s immune T cells to recognize and attack diseased tissues. Approved for clinical use in 2017, it has been transformative for blood cancers such as leukemias and lymphomas. However, the therapy has faced significant challenges when applied to solid tumors—cancers that develop in organs like the liver, kidneys, or pancreas. These tumors have proven much harder for engineered immune T cells to identify and destroy.
Now, researchers at Columbia University have potentially found a new approach. Sophie Hanina, driven by what she describes as a “hunch,” has identified a marker called CD70 that is displayed by all cancer cells. By programming CAR-T cells to target CD70, Hanina successfully eradicated tumors in mice implanted with various human cancers.
Understanding CAR-T Cell Therapy
A T-cell is a crucial component of the immune system, acting as a frontline soldier that travels through the blood to identify and eliminate infected or abnormal cells. Cancer cells, however, are adept at evading detection by the immune system, which is where CAR-T cell therapy comes into play. This therapy transforms T-cells into highly trained “serial killers” capable of recognizing cancer cells more effectively.
The term CAR stands for Chimeric Antigen Receptor—a synthetic receptor added to T-cells to enhance their ability to recognize cancer cells. Essentially, this process involves programming the T-cell with a specific target found on a patient’s cancer, growing these cells in a lab, and then infusing them back into the patient. Once inside the body, these engineered CAR-T cells focus on the cancer and begin their attack. As Hanina explains, “Really it’s a living drug, it’s your immune system upgraded to hunt down cancer.”
Challenges with Solid Tumors
Despite the success of CAR-T therapy in treating blood cancers, solid tumors present a different set of challenges. In blood cancers, the target is present on nearly every cancer cell, making it easier for CAR-T cells to identify and attack. However, in solid tumors, the target is often also found on healthy cells, complicating efforts to attack the tumor without harming normal tissues.
Furthermore, potential targets in solid tumors are not always uniformly expressed across all cancer cells. For instance, the protein CD70, which Hanina is studying, is found in about 20 different solid tumor cancer types and shows promise as a CAR target due to its limited expression on healthy cells. However, within a patient’s cancer, expression can be patchy, with only some cancer cells displaying the target, allowing others to evade detection and continue growing.
A New Hope: Targeting CD70
Hanina’s research suggests that tumor cells appearing negative for CD70 might not be truly negative. Instead, they may retain ultra-low levels of CD70, undetectable by normal methods and invisible to current clinical CAR-T cells. By designing a more sensitive receptor, Hanina’s team was able to eradicate entire tumors in mice using human CAR-T cells and a sensitive receptor targeting CD70.
“It was a hunch. I basically found that tumor cells that look like they’re negative for CD70 might not be negative at all.” — Sophie Hanina
This discovery could mark a significant advancement in the treatment of solid tumors, potentially turning a vulnerability of the tumor cell into its Achilles heel. However, Hanina acknowledges the possibility that cancer cells could evolve to evade detection, although in her mouse models, the cancers did not return.
Implications and Future Directions
The implications of this research are profound, offering hope for more effective treatments for solid tumors. If successful in humans, this approach could significantly improve the prognosis for patients with solid tumors, which have historically been more difficult to treat with CAR-T therapy.
Looking forward, further research is needed to confirm these findings in clinical trials and to explore the potential for similar strategies targeting other markers. As the field of cancer immunotherapy continues to evolve, breakthroughs like this could pave the way for new, more effective treatments, offering renewed hope to patients and their families.
In summary, the work of Sophie Hanina and her team represents a promising step forward in the fight against cancer, highlighting the potential of CAR-T cell therapy to tackle even the most challenging solid tumors.
