Single-cell integration analysis reveals molecular signatures of the tumor microenvironment in early-onset colorectal cancer.

The incidence of early-onset colorectal cancer (CRC), defined as cases diagnosed in individuals under 50, is rising globally. However, its molecular and immune characteristics remain poorly understood. In this study, we analyze single-cell RNA sequencing data from 168 CRC patients, aged 22 to 91, to investigate differences between early-onset and standard-onset CRC. We find a reduced proportion of tumor-infiltrating myeloid cells, a higher burden of copy number variations, and decreased tumor-immune interactions in early-onset CRC. Additionally, immune signatures unique to early-onset CRC are associated with differential responses to immunotherapy, underscoring the need for tailored therapeutic strategies for this group of patients. These findings provide valuable insights into the molecular and immune landscape of early-onset CRC, emphasizing the importance of developing targeted prevention and treatment strategies.