Discover how combining 4-1BB and CD28 signaling creates synergistic effects in umbilical cord blood T-cells for enhanced cancer immunotherapy.
Every year, thousands of parents make the decision to store their newborn's umbilical cord blood, a biological insurance policy rich with stem cells that could potentially treat future diseases. What makes this substance so valuable? Cord blood contains powerful immune cells called T-cells that can be harnessed to fight cancer. However, there's a catch – these neonatal T-cells are notably naive and underdeveloped compared to their adult counterparts, often lacking the punch needed for effective cancer therapy.
Recent research has revealed that combining 4-1BB and CD28 signaling creates a powerful synergistic effect, redirecting umbilical cord blood T-cells into potent weapons against B-cell malignancies 1 .
For decades, scientists have sought to overcome this limitation. The breakthrough came when researchers discovered how to genetically engineer these T-cells with chimeric antigen receptors (CARs), effectively creating guided missiles that can target and destroy cancer cells. This advancement not only enhances cancer treatment but also unlocks the full potential of cord blood banks worldwide.
Chimeric antigen receptor (CAR) T-cells represent a revolutionary approach to cancer treatment that merges the targeting ability of antibodies with the killing power of T-cells.
Think of CARs as specialized navigation systems that can be installed into immune cells. These systems consist of three main components:
First-generation CARs contained only the activation signal (CD3ζ), which proved insufficient for sustained anti-tumor responses 3 .
In the natural immune response, T-cells require two signals for complete activation. Scientists have replicated this requirement in CAR design by incorporating co-stimulatory domains. The two most common such domains are derived from CD28 and 4-1BB, each offering distinct advantages 2 :
Provide a powerful initial burst of activity, driving rapid proliferation and immediate cancer-killing capacity.
High Glycolysis Effector PhenotypePromote long-term persistence by enhancing mitochondrial fitness and memory formation.
Oxidative Metabolism Memory FormationLeverages strengths of both signals for optimal cancer-fighting capability in cord blood T-cells 1 .
Metabolic Plasticity Balanced ResponseThe remarkable discovery came when researchers found that combining both CD28 and 4-1BB signaling domains creates a synergistic effect far greater than either domain alone. This combination leverages the unique strengths of both signals:
Research demonstrates that the spatial organization of these domains within the CAR structure critically impacts their effectiveness 3 .
Traditional "third-generation" CARs that simply fuse both domains in a single linear sequence have shown disappointing clinical results.
Innovative "parallel CAR" designs that position each co-stimulatory domain in its natural membrane-proximal location have proven far more effective.
| CAR Design | Metabolic Profile | Persistence | Anti-Tumor Activity | Best Use Case |
|---|---|---|---|---|
| CD28-based | High glycolysis | Short-term | Potent initial response | Rapid tumor reduction |
| 4-1BB-based | Oxidative metabolism | Long-term | Sustained activity | Preventing recurrence |
| Combined (Synergistic) | Metabolic plasticity | Balanced | Comprehensive | Challenging malignancies |
To investigate the synergistic potential of 4-1BB and CD28 signaling in umbilical cord blood T-cells, researchers designed a comprehensive study using lentiviral vectors to engineer four distinct CAR configurations 1 .
Four different CD19-targeting CARs were created with varying signaling domains.
Umbilical cord blood units were obtained from cord blood banks.
Cells were activated and transduced with lentiviral vectors.
The results consistently demonstrated the advantage of incorporating both costimulatory domains:
Both UCB-19BBζ and UCB-1928BBζ T-cells exhibited enhanced killing capability against CD19+ leukemia and lymphoma cell lines.
In mouse models, UCB-19BBζ and UCB-1928BBζ T-cells mounted the most potent antitumor response.
UCB-1928BBζ T-cells demonstrated a more robust antitumor response than UCB-19BBζ in controlling disseminated disease 1 .
| Treatment Group | Average Survival (Days) | Long-Term Survivors | Tumor Clearance |
|---|---|---|---|
| No Treatment | 35 | 0% | None |
| UCB-19ζ CAR | 42 | 10% | Partial |
| UCB-1928ζ CAR | 49 | 20% | Partial |
| UCB-19BBζ CAR | 63 | 40% | Complete in 40% |
| UCB-1928BBζ CAR | 77 | 60% | Complete in 60% |
The molecular basis for this synergy lies in the complementary signaling pathways activated by each costimulatory domain. CD28 signaling promotes rapid IL-2 production and metabolic reprogramming toward glycolysis, while 4-1BB signaling enhances mitochondrial biogenesis and upregulates anti-apoptotic proteins 2 6 .
Essential research reagents and tools used in CAR T-cell development and studies:
| Reagent / Tool | Function in Research | Application in CAR T-Cell Studies |
|---|---|---|
| Lentiviral Vectors | Gene delivery system | Introducing CAR constructs into T-cells |
| Anti-CD3/CD28 Beads | T-cell activation | Mimicking natural T-cell stimulation prior to engineering |
| Cytokine Arrays | Multiplex protein detection | Measuring IFN-γ, IL-2, TNF-α release upon target engagement |
| Flow Cytometry | Cell surface marker analysis | Confirming CAR expression and profiling memory markers |
| Mouse Xenograft Models | In vivo testing platform | Evaluating anti-tumor efficacy and T-cell persistence |
The discovery that 4-1BB and CD28 signaling play a synergistic role in redirecting umbilical cord blood T-cells against B-cell malignancies represents a significant advancement in cancer immunotherapy. This approach maximizes the therapeutic potential of cord blood – an increasingly available resource in cord blood banks worldwide – while addressing the historical limitations of these cells in adoptive therapy.
As these technologies mature, we move closer to a future where a child's cord blood could potentially treat their own cancer years or decades later, or where banked cord blood units become reliable sources for off-the-shelf cellular therapies 1 3 .
The synergistic combination of 4-1BB and CD28 in cord blood CAR T-cells exemplifies how understanding and respecting nature's complexity leads to the most powerful therapeutic solutions.