T cell landscape in the microenvironment of human solid tumors

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• T cells are key mediators of anti-tumor immunity, differentiating into effector and memory cells.
• Tumor cells can evade immune surveillance, leading to T cell exhaustion and expansion of regulatory T cells within the tumor microenvironment (TME).
• Resident T cell subsets in peripheral tissues may offer rapid, localized anti-cancer responses.

Purpose of the Study:

• To review the characteristics of T cells within solid tumor microenvironments (TME) in adult and pediatric cancers.
• To explore mechanisms of immune checkpoint upregulation and transcriptional/epigenetic changes leading to T cell dysfunction and exhaustion.
• To discuss how interactions with tumor and non-neoplastic cells influence T cell plasticity and promote immune evasion, ultimately proposing novel immunotherapy strategies.

Main Methods:

• Literature review of current knowledge on T cells in the tumor microenvironment.
• Analysis of mechanisms driving T cell exhaustion, including immune checkpoints and epigenetic modifications.
• Examination of T cell interactions with other cells and molecules within the TME.
• Discussion of current cancer immunotherapy limitations and future therapeutic approaches.

Main Results:

• T cells in the TME exhibit dysfunction and exhaustion due to factors like immune checkpoint upregulation and altered transcriptional/epigenetic landscapes.
• Interactions with tumor and stromal cells within the TME compromise T cell plasticity, promoting immune evasion.
• Regulatory T cells play a significant role in establishing an immunosuppressive TME, facilitating tumor growth and metastasis.
• Many current immunotherapies, including checkpoint inhibitors and CAR T cell therapy, face resistance in a significant proportion of tumors.

Conclusions:

• Understanding T cell behavior and dysfunction within the TME is critical for developing effective cancer treatments.
• Novel strategies are needed to overcome T cell exhaustion and the immunosuppressive nature of the TME.
• Improving T cell-based cancer immunotherapies requires addressing intrinsic T cell plasticity and external suppressive factors to enhance anti-tumor responses.