Short leukocyte telomere length predicts poor prognosis and indicates altered immune functions in colorectal cancer patients

Short leukocyte telomere length is associated with poor prognosis in CRC. Leukocyte telomere length and TNM stage show a significant joint effect in prognosis prediction of CRC. Short leukocyte telomere length is associated with altered immune functions in CRC.Numerous studies indicate that the leukocyte telomere length is associated with the risk of cancers, including colorectal cancer (CRC). However, the prognostic value of leukocyte telomere length in CRC patients has not been investigated. Relative telomere length (RTL) of peripheral blood leukocytes (PBLs) from 571 CRC patients receiving surgical resection was measured using a polymerase chain reaction-based method. The Cox proportional hazards ratio model and the Kaplan-Meier curve were used to estimate the association between RTL and the clinical outcome of CRC patients in the training set (90 patients) and the testing set (86 patients). Finally, an independent cohort of 395 patients was used as an external validation set. The immunophenotype of PBLs and the plasma concentration of several immune-related cytokines were determined by flow cytometry and enzyme-linked immunosorbent assay, respectively. Patients with shorter RTL had significantly poorer overall survival and relapse-free survival than those with longer RTL in the training, testing and validation sets. Furthermore, leukocyte RTL and Tumor-Node-Metastasis (TNM) stage exhibited a significant joint effect in the prognosis prediction of combined CRC patients, indicating that patients with both short RTL and advanced stages had the worst prognosis, when compared with other subgroups. In addition, patients with short RTL showed the higher percentage of CD4(+) T cell and the lower percentage of B cell in peripheral blood mononuclear cells, as well as the lower concentration of plasma transforming growth factor-beta 1, suggesting a possibility that the immune functions changed with RTL alteration. Our study for the first time demonstrates that leukocyte RTL is an independent prognostic marker complementing TNM stage and associated with the immune functions in CRC patients.