The Expression of Both Peroxisome Proliferator-Activated Receptor Delta and Cyclooxygenase-2 in Tissues Is Associated with Poor Prognosis in Colorectal Cancer Patients

The role of peroxisome proliferator-activated receptor delta (PPAR delta) in the development and progression of colorectal cancer (CRC) remains controversial. We investigated the impact of PPAR delta expression in tissues on liver metastasis of CRC. We analyzed samples of primary CRC and matched normal adjacent tissues from 52 patients for the expression of PPAR delta, cyclooxygenase (COX)-2, vascular endothelial growth factor (VEGF)-A, and CXC chemokine receptor 4 (CXCR4). Correlations of the molecules expressions with clinical characteristics and prognosis of patients were studied. The number of patients positive for PPAR delta, COX-2, CXCR4, and VEGF-A was 25, 33, 18, and 19, respectively. Among the PPAR delta (+)/COX-2 (+), PPAR delta (-)/COX-2 (+), PPAR delta (+)/COX-2 (-), and PPAR delta (-)/COX-2 (-) patient groups, PPAR delta (+)/COX-2 (+) patients had the highest incidence of liver metastasis (p < 0.01). PPAR delta (+)/COX-2 (+) expression was a significant independent prognostic factor (HR = 7.108, 95% CI 1.231-41.029, p = 0.0283) by Cox proportional analysis. PPAR delta (+)/COX-2 (+) patients had the highest positivity for CXCR4 or VEGF-A in tissues (p < 0.01). Among the patients in the CXCR4 (+)/VEGF-A (+), CXCR4 (+)/VEGF-A (-), CXCR4 (-)/VEGF-A (+), and CXCR4 (-)/VEGF-A (-) groups, CXCR4 (+)/VEGF-A (+) patients had the highest incidence of liver metastasis (p < 0.01). The expression of both PPAR delta and COX-2 in tissues may lead to liver metastasis and consequent poor prognosis in CRC patients.