Two Genetic Edits That Supercharge CAR-T Cells Against Solid Tumors

GNAS Knockout: Sustaining Cancer-Fighting Activity

Once inside the tumor, T cells face a hostile microenvironment filled with suppressive signals. GNAS (which encodes the Gαs protein) acts as a central signaling hub that processes multiple suppressive signals from the tumor microenvironment. Deleting GNAS makes T cells largely unresponsive to those signals, allowing them to maintain high production of interferon-gamma (IFN-γ), a key anti-tumor effector molecule . This makes the T cells resistant to the immunosuppressive conditions that normally cripple immune function within solid tumors.

Synergistic Combination: Infiltration and Activity

Removing both P2RY8 and GNAS together produces a synergistic benefit: the T cells both enter the tumor in greater numbers and remain highly active once inside. In a lung cancer mouse model, even at a very low CAR-T cell dose, two-thirds of mice were tumor-free at the end of the study, whereas none of the mice that received control-edited CAR-T cells cleared their tumors .

Breadth Across Solid Tumor Models

The benefits of these edits extend beyond lung cancer. CAR-T cells lacking GNAS alone shrank tumors across multiple solid tumor models, including melanoma, lung cancer, pancreatic cancer, gastroesophageal adenocarcinoma, and uterine sarcoma . The combination edits also worked when tested in T cells derived from ovarian cancer and melanoma patients, confirming translatability to patient-derived cells .

No long-term side effects were observed in mice followed for more than six months after tumor clearance, suggesting a favorable safety profile .

A New Platform for Discovery

The identification of P2RY8 and GNAS was enabled by a novel in vivo CRISPR screening platform developed by the same team. This platform allows genome-scale loss-of-function screens in primary human T cells within tumor-bearing mice, overcoming previous limitations that confined CRISPR screens to in vitro settings or required large numbers of animals . The system involves overexpressing a CD3 scFv on tumor cells to achieve high recovery of tumor-infiltrating T cells, permitting comprehensive analysis with a relatively small number of animals .

Implications for Cancer Immunotherapy

These findings represent a significant step toward making CAR-T cell therapy effective against solid tumors, which account for the vast majority of cancers. The dual-editing strategy addresses two of the most critical barriers to solid tumor immunotherapy: poor T cell infiltration and the immunosuppressive tumor microenvironment. The favorable safety profile observed in long-term mouse studies also supports further development toward clinical testing .