JAK-STAT-activated, fratricide-resistant CAR-T cells targeting membrane-bound TNF effectively treat AML and solid...

Prior research has shown that chimeric antigen receptor T-cell therapies provide significant clinical benefits for patients with B-cell malignancies and multiple myeloma. These engineered cells utilize synthetic receptors to recognize specific surface proteins on malignant cells, triggering a potent immune response. However, the application of this technology to acute myeloid leukemia and various solid tumors remains limited by a severe shortage of validated, tumor-specific antigens. Tumor necrosis factor often appears on the surface of these difficult-to-treat cancer cells before undergoing proteolytic shedding into the microenvironment. This shedding process typically leaves behind a small membrane-bound remnant that is often ignored by conventional therapeutic antibodies. This protein fragment remains anchored to the plasma membrane even after the functional cytokine is released. This absence of evidence motivated the current investigation into targeting the residual fragments of surface-expressed cytokines.

The investigators designed a novel cellular immunotherapy targeting the N-terminal fragment of tumor necrosis factor to overcome antigen scarcity in myeloid leukemia. They prioritized the identification of monoclonal antibodies that specifically bind the membrane-retained portion of the cytokine after its extracellular domain is shed. By engineering T cells with these antibody sequences, the team created a precise tool for eliminating malignant cells while sparing healthy hematopoietic progenitors. A secondary objective involved addressing the inherent instability and poor persistence of these cells within the immunosuppressive tumor environment. The researchers integrated a modified cytokine receptor, known as G6/7R, to provide continuous survival signals through intracellular pathways. This specific mutation was selected to provide a robust and steady-state proliferative stimulus to the T cells. This comprehensive approach sought to validate a new target for chimeric receptors across both liquid and solid tumor models.

The experimental workflow began with the generation of monoclonal antibodies specifically reactive to the N-terminal fragment of tumor necrosis factor (TNF-NTF). These sequences were subsequently incorporated into a chimeric antigen receptor construct to produce TNF-NTF CAR-T cells. To enhance intracellular signaling, the team utilized a chimeric cytokine receptor (G6/7R) composed of GP130, IL6R, and a constitutively active IL7R containing the M452L mutation. CRISPR-Cas9 technology enabled the genetic knockout of the endogenous TNF gene to prevent self-recognition and subsequent fratricide among the engineered population. The researchers evaluated cytotoxic performance using in vitro lysis assays against various leukemia cell lines and TNF-expressing ovarian tumor cells. In vivo efficacy and persistence were monitored in mouse models of acute myeloid leukemia and ovarian cancer using bioluminescence imaging. The team also performed extensive screening of antibody libraries to ensure high affinity for the specific N-terminal epitope.

The G6/7R-expressing TNF-knockout TNF-NTF CAR-T cells demonstrated superior persistence and durable antileukemic efficacy in vivo compared to standard constructs. Initial tests showed that while the cells efficiently lysed targets in vitro, they suffered from poor expansion due to T-cell-mediated fratricide. Deleting the TNF gene significantly improved the viability and proliferative capacity of the therapeutic cells without compromising their core cytotoxic functions. The integration of the G6/7R receptor provided constitutive activation of the janus kinase (JAK)-signal transducers and activators of transcription (STAT) pathway. The researchers observed that the modified cells maintained their phenotypic markers and functional potency over extended periods in the systemic circulation. The engineered cells successfully eliminated primary leukemia-initiating cells while showing no toxicity toward normal CD34-positive hematopoietic progenitors. Final experiments confirmed the curative potential of this approach in a xenograft model of TNF-expressing ovarian cancer, where mice showed complete tumor clearance.

These findings establish the N-terminal fragment of tumor necrosis factor as a viable and safe target for chimeric antigen receptor therapy. The successful elimination of leukemia-initiating populations suggests that this approach could prevent disease relapse in patients with acute myeloid leukemia. By overcoming the challenge of fratricide through genetic modification, the study provides a blueprint for targeting other antigens that are upregulated during T-cell activation. The use of the G6/7R chimeric receptor highlights the importance of supplemental cytokine signaling for maintaining CAR-T cell fitness in challenging tumor niches. Future clinical trials may utilize these multi-engineered cells to address the limitations of current immunotherapies in non-B-cell cancers. The research underscores the necessity of combining target discovery with sophisticated intracellular engineering to achieve curative outcomes. These results suggest that membrane-bound cytokine fragments represent a largely untapped reservoir of tumor-specific antigens for future drug development.