Key immune cells in the tumor immune microenvironment of colorectal cancer: Roles and research advances (Review)

Colorectal cancer (CRC) is the third most common cancer globally and the second leading cause of cancer‑related mortalities. Surgery‑centered multimodal therapy remains the cornerstone of care, yet outcomes are poor in advanced or drug‑resistant disease. The tumor immune microenvironment (TIME), a network of immune cells, cytokines and stromal elements, shapes antitumor immunity and can either restrain or encourage tumor growth. Specific immune cells within the TIME influence CRC biology, while immune‑checkpoint blockade has delivered notable benefits, especially in microsatellite instability‑high tumors. The present review discusses the principal immune cell populations in the CRC TIME, outlines their mechanisms of action and discusses emerging cell‑based immunotherapies that may guide future precision treatment.