HDACi-dependent Microenvironmental Normalization Overcomes Tumor Burden-induced T-cell Exhaustion.

Area of Science:

• Immunology
• Cancer Biology
• Epigenetics

Background:

• T-cell exhaustion limits the effectiveness of immunotherapies like adoptive T-cell therapy (ACT) in solid tumors.
• Tumor burden significantly impacts T-cell responses and immunotherapy outcomes.
• Identifying mechanisms of T-cell exhaustion is crucial for improving cancer treatment.

Purpose of the Study:

• To investigate tumor burden-related pathway changes that contribute to T-cell exhaustion.
• To determine if epigenetic modulation can reverse T-cell exhaustion and enhance immunotherapy response.

Main Methods:

• Developed a murine syngeneic tumor model with varying tumor burdens.
• Utilized transcriptome analysis to identify immunosuppressive pathways in large tumors.
• Administered epigenetic modifier MS-275 in combination with ACT and assessed T-cell exhaustion and therapeutic efficacy.

Main Results:

• Adoptive T-cell therapy (ACT) effectively regressed small tumors but failed against large tumors, associated with systemic T-cell exhaustion.
• MS-275 treatment reversed immunosuppressive pathways in large tumors, leading to durable tumor regression when combined with ACT.
• Transferred T cells showed reduced exhaustion markers but enhanced activation signaling, shifting towards a terminal effector phenotype.

Conclusions:

• Epigenetic reprogramming can overcome tumor burden-induced T-cell exhaustion.
• Reversing immunosuppressive pathways through epigenetic modulation enhances the efficacy of ACT.
• This strategy converts exhausted T cells into effector cells, improving immunotherapy outcomes in solid tumors.