Higher Levels of Tumour-Infiltrating Lymphocytes (TILs) are Associated with a Better Prognosis, While CDK5 Plays a Different Role Between Nonmetastatic and Metastatic Colonic Carcinoma

OBJECTIVE We investigated the prognostic value of cyclin-dependent kinase 5 (CDK5) in a true population-based cohort of patients with colon cancer. METHODS 1. Immunohistochemical (IHC) staining was used to retrospectively analyse the expression of CDK5 in colon cancer tissue samples of 296 patients. The χ2 test, Kaplan-Meier method and Cox proportional regression model were used to analyse the difference between the patients with differential expression of CDK5 and with different stages (metastatic and nonmetastatic); 2. The number of tumour-infiltrating lymphocytes (TILs) in tumour sections was determined, and its relationship with prognosis was explored. RESULTS 1. Among 296 patients stained for CDK5, 18 cases (6.09%) showed negative expression, 77 cases (26.01%) showed weak expression (+1), 124 cases (41.89%) showed medium positive expression (2+), and 77 cases (26.01%) showed strong positive expression (3+). The expression of CDK5 was neither related to mismatch repair nor TILs (p > .05). In non-metastatic patients, longer progression-free survival (PFS) and cancer-specific survival (CSS) were observed in patients with high CDK5 expression (2+ or 3+) than low CDK5 expression (- or 1+), while in metastatic disease, the opposite was true (p < .001). 2. TILs in 226 patients were detected in the study. Among them, 115 cases (50.88%) showed a low number of TILs (TILs-L), and 111 cases (49.12%) showed a high number of TILs (TILs-H). Patients with a TIL ratio greater than .2 had a significantly better CSS (p < .001) or PFS (p = .008) than patients with a lower TIL ratio. By multivariate analysis, TILs-H was a protective factor for CSS, however failed to reach a significant difference (hazard ratio: .59, 95% CI: .33∼1.06, p = .079), and so was the PFS (HR: .65, 95% CI: .29∼1.43, p = .279). CONCLUSION High expression of CDK5 indicates a good prognosis in nonmetastatic colon cancer, while it is the opposite in metastatic colon cancer, and the expression of CDK5 is unrelated to TILs. Patients with TIL-H have a better prognosis, with a proper cut-off value of 20% for colon cancer.