A new approach that delivers a “double punch” to help T cells attack solid tumors is the focus of a preclinical study by researchers from the Perelman School of Medicine at the University of Pennsylvania. Results published in Proceedings of the National Academy of Sciences (PNAS)And showed that targeting two regulators that control the functions of inflammation-related genes increased T-cell expansion by at least 10-fold in models, resulting in increased antitumor immune activity and robustness.
CAR T-cell therapy was pioneered in Penn Medicine by Carl H. John, MD, Richard W. Fagg Professor of Immunotherapy at Penn and director of the Center for Cellular Immunotherapy (CCI) at Abramson Cancer Center, whose work led to the first approved cell therapy CAR T cells were used in the treatment of B-cell acute lymphoblastic leukemia in 2017. Since then, personalized cell therapies have revolutionized the treatment of leukemia, but they have remained stubbornly ineffective against solid tumours, such as lung and breast cancer.
“We want to unlock CAR T-cell therapy for patients with solid tumors, which include the most common types of cancer,” said John, senior author of the new study. “Our study shows that targeting an immune regulator of inflammation deserves further investigation to enhance T-cell potency.”
One of the challenges of CAR T-cell therapy in solid tumors is a phenomenon known as T-cell depletion, in which continued exposure to antigen from the solid mass of tumor cells decimates T cells to the point that they are unable to mount an antitumor response. Engineering already results in depleting T cells from patients for CAR T cell therapy in a less effective product because the T cells do not proliferate enough or remember their task as well.
Previous observational studies have hinted at the inflammatory regulator Regnase-1 as a potential target to indirectly overcome the effects of T-cell depletion because it can cause excessive inflammation when it malfunctions in T cells – activating them to produce an antitumor response. The research team, including lead author David May, a bioengineering graduate student in the College of Engineering and Applied Sciences, and co-author Neil Sheppard, Dr. Roquin-1 regulator can simultaneously enhance the responses further.
“Each of these two regulator genes has a role in restricting T-cell inflammatory responses, but we found that inactivating them together produces much greater anticancer effects than inactivating them individually,” May said. “By building on previous research, we are starting to move closer to strategies that appear promising in the context of solid tumor.”
The team used CRISPR-Cas9 gene-editing technology to knock down Regnase-1 and Roquin-1 individually and in combination in healthy donor T cells with two different immune receptors currently being investigated in phase I clinical trials: a mesothelin M5 CAR (mesoCAR) targeting. and NY-ESO-1-Target 8F TCR (NYESO TCR). None of the engineered T cell products target CD19, the antigen targeted by most approved CAR T cell therapies, because this antigen is not present in solid tumours.
After CRISPR editing, the T cells were expanded and implanted into mouse models with solid tumors, where the authors noted that the double knockout resulted in at least 10 times as many engineered T cells as compared to inactivation of Regnase-1 alone, as well as increased antitumor activity and immunogenicity. Longevity of engineered T cells. In some mice, it also increased lymphocyte production, causing toxicity.
“CRISPR is a useful tool to completely attenuate the expression of target genes such as Regnase and Roquin, resulting in a pronounced phenotype, but there are other strategies to consider for translating this work into the clinical setting, such as forms of conditional gene regulation,” Sheppard said. “We are certainly impressed with the anti-tumor efficacy unleashed by knocking out these two non-redundant proteins together. In studies of solid tumors, we often see limited expansion of CAR T cells, but if we can make each cell stronger, and replicate in larger quantities, we expect that T-cell therapy has a better effect in attacking solid tumours.”
Additional authors include Omar Johnson, Jordan Reeve, Ting Jia Fan, and John Shuler. The research was supported by the National Institutes of Health (1P01CA214278, R01CA226983), the Parker Institute for Cancer Immunotherapy, the Emerson Group, the Fontaine Fellowship, the Norman and Selma Crone Research Fellowship, and the Robert Wood Johnson Foundation Health Policy Research Scholars.