Exploring the tumor microenvironment of colorectal cancer patients post renal transplantation by single-cell analysis

Patients with colorectal cancer (CRC) following renal transplantation require long-term immunosuppressants to prevent graft rejection. However, the impact of these immunosuppressants on the tumor immune microenvironment and the roles of immune cells within it remain poorly understood. We conducted comprehensive single-cell RNA sequencing on tumor and normal tissues from four CRC patients post renal transplantation and compared these with published data from 23 non-transplant CRC patients. We set four groups for detailed comparative analysis based on the renal transplantation status and tissue origin: non-renal transplantation normal (nRT_Normal), non-renal transplantation tumor (nRT_Tumor), renal transplantation normal (RT_Normal), renal transplantation tumor (RT_Tumor). Our analysis revealed significant tumor immune microenvironment landscape alterations in the transplantation group. CD8⁺effector T cells of RT_Tumor showed significantly diminished cytotoxicity and tumor neoantigen recognition (p < 0.0001), while CD4⁺FOXP3 regulatory T cells of RT_Tumor displayed a higher inhibitory score (p < 0.05), indicating preserved immunomodulatory potential compared with non-transplant CRC. Notably, significantly increased CTLA4 expression in T cells of RT_Tumor was found and testified (p < 0.05). Our findings provide novel mechanistic insights for understanding the immune landscape in renal transplant recipients with CRC and pave the way for potential immunotherapeutic strategies that may improve survival and quality of life for this patient population.