In a groundbreaking advance that could redefine the future of cancer immunotherapy, researchers from Mass General Brigham and the Broad Institute of MIT and Harvard have harnessed the power of CRISPR gene-editing technology to optimize chimeric antigen receptor (CAR)-T cell therapies against multiple myeloma. This innovative study, recently published in Nature, unveils how systematic genetic modifications can significantly enhance the persistence and efficacy of CAR-T cells, revealing previously uncharted mechanisms that govern their function both in laboratory cultures and living organisms.
CAR-T cell therapy, an immunotherapeutic approach that engineers a patient’s own T cells to recognize and target cancer cells, has been a transformative treatment for hematologic malignancies. Despite its success in blood cancers, CAR-T therapy has struggled with limited effectiveness against solid tumors and relapsed forms of multiple myeloma. One major obstacle lies in the dwindling numbers and diminished functional capacity of CAR-T cells following infusion, which undermines sustained tumor eradication. Understanding the genetic regulators that influence CAR-T cell survival and functionality has thus become a critical frontier in the field.
The research team employed an unparalleled in vivo CRISPR screening approach, targeting 135 genes implicated in T cell biology, to methodically interrogate their roles in CAR-T cell performance. Unlike traditional screening methods limited to in vitro analysis, this comprehensive lifecycle screen tracked CRISPR-edited CAR-T cells after infusion into a preclinical mouse model of multiple myeloma for up to 21 days. This dual setting approach enabled the identification of genetic modifiers whose effects manifest distinctly within the complex tumor microenvironment—insights that static laboratory cultures alone cannot provide.
Among the pivotal findings, deletion of the cell cycle regulator gene CDKN1B emerged as a potent enhancer of CAR-T cell proliferation and long-term persistence. CDKN1B, known to encode the protein p27^Kip1, acts as a brake on cell cycle progression, limiting cellular replication. By knocking out this gene, the modified CAR-T cells demonstrated accelerated expansion and sustained anti-tumor activity, ultimately improving tumor clearance. This discovery highlights how fine-tuning cell-intrinsic checkpoints can unlock superior therapeutic potential without compromising safety.
Interestingly, the study also highlighted the complexity and contextual dependency of gene function. Certain genes that influenced CAR-T cell activity robustly in vitro failed to confer benefits in vivo, whereas others that promoted early proliferation within tumors did not translate to durable responses. These discrepancies emphasize the critical need for in vivo validation using physiologically relevant models in the development of next-generation immunotherapies.
The implications of these findings extend beyond multiple myeloma. By integrating this sophisticated CRISPR screening platform, researchers now possess a scalable and high-throughput tool to uncover genetic determinants that modulate CAR-T cell behavior across diverse cancers. This could revolutionize how combinatorial gene edits are employed to engineer customizable, fine-tuned cell therapies engineered to overcome tumor heterogeneity and immune evasion.
Co-senior author Dr. Robert Manguso, a leading immunotherapy scientist at Massachusetts General Hospital and the Broad Institute, underscored the novelty of screening throughout the entire T cell lifecycle, noting that the in vivo context unveiled key regulatory genes invisible to in vitro experiments. Meanwhile, Dr. Marcela Maus, director of the Cellular Immunotherapy Program at Mass General Brigham, emphasized the practical advantage of this approach: “Testing hundreds of genetic modifications simultaneously accelerates discovery that previously would have taken years and immense resources.”
The study was supported by federal funding, including grants from the National Institutes of Health and the Krantz Breakthrough Award, underscoring the importance of foundational research investments in catalyzing biomedical innovation. The authors detail a meticulous experimental design involving human donor-derived CAR-T cells, sophisticated CRISPR gene editing, and rigorous functional assays to validate results across ex vivo and in vivo conditions.
At its core, this work exemplifies how cutting-edge genome engineering, combined with clinically relevant disease models, holds the key to cracking the enigma of cancer resistance to immunotherapy. By enhancing CAR-T cell durability and anti-tumor function through targeted genetic modifications, this research charts a promising path toward improving patient outcomes in multiple myeloma—and potentially a broad spectrum of malignancies.
Future studies inspired by this breakthrough are poised to systematically explore combinations of gene edits to refine CAR-T cell therapies further. The integration of multiplexed CRISPR screens with emerging single-cell technologies and systems immunology could illuminate the intricate cellular crosstalk and evolutionary dynamics that dictate therapeutic response and resistance.
In conclusion, the identification of CDKN1B as a crucial genetic modifier opens new therapeutic avenues and underscores the necessity of precision genome editing to elevate cancer immunotherapy to new heights. As CAR-T cell therapy evolves from single target modifications to holistic reprogramming of immune cells, patients with multiple myeloma and other challenging cancers may soon benefit from more potent, persistent, and adaptable cellular treatments.
Subject of Research: Cells
Article Title: In vivo CRISPR screens identify modifiers of CAR-T cell function in myeloma
News Publication Date: 24-Sep-2025
Web References:
https://www.nature.com/articles/s41586-025-09489-8
http://dx.doi.org/10.1038/s41586-025-09489-8
References:
Knudson NH et al. “In vivo CRISPR screens identify modifiers of CAR-T cell function in myeloma” Nature DOI: 10.1038/s41586-025-09489-8
Keywords:
Cancer immunotherapy, Chimeric antigen receptor therapy, Immunology, Cancer, Multiple myeloma, Blood cancer, CRISPRs
