The Immune Environment in Colorectal Adenoma: A Systematic Review.

Area of Science:

• Oncology
• Immunology
• Gastroenterology

Background:

• Colorectal adenoma, a precursor to colorectal cancer, has less research compared to carcinoma.
• Immune responses within the tumor microenvironment may influence adenoma progression.
• Understanding these immune interactions is key to identifying factors preventing malignant transformation.

Purpose of the Study:

• To systematically review immune infiltration patterns in sporadic colorectal adenoma.
• To analyze changes in immune cells, cytokines, and immunological factors along the adenoma-carcinoma sequence.
• To synthesize current research on the immunological landscape of premalignant colorectal lesions.

Main Methods:

• Systematic review of research up to December 2024.
• Inclusion of studies from PubMed and Web of Science databases.
• Analysis of immune cell counts, densities, and cytokine expression in colorectal adenoma and carcinoma tissues.

Main Results:

• Significant differences in immune cell counts and cytokine expression between adenoma and carcinoma.
• No consensus on CD4+ and CD8+ T cell tendencies; decreasing mDCs, plasma, and naïve B cells observed.
• Eosinophil density decreases from adenoma to carcinoma; specific cytokines (IL-1α, IL-4, IL-6, etc.) increase, while others (IL-12A, IL-18, IFN-γ, TNFα) decrease.
• Overexpression of COX-2, PD-1/PD-L1, CTLA-4, and ICOS/ICOSLG noted in adenomatous and cancerous tissues.

Conclusions:

• Further research is essential to fully understand colorectal adenoma-associated immunity.
• Investigating the immune system's role is critical for predicting adenoma progression potential.
• Elucidating these immune dynamics may offer insights into cancer prevention and treatment strategies.