Anti-colon cancer effect of caffeic acid p-nitro-phenethyl ester in vitro and in vivo and detection of its metabolites

Caffeic acid phenethyl ester (CAPE), extracted from propolis, was proven to inhibit colon cancer. Caffeic acid p-nitro-phenethyl ester (CAPE-pNO(2)), a derivative of CAPE, was determined to be an anti-platelet agent and a protector of myocardial ischaemia with more potent effects. In the present study, CAPE-pNO(2) showed stronger cytotoxic activity than CAPE. We revealed interactions between CAPE-pNO(2) and experimental cells. CAPE-pNO(2) induced apoptosis in HT-29 cells by up-regulating P53, cleaved-caspase-3, Bax, P38 and CytoC; CAPE-pNO(2) also up-regulated P21(Cip1) and P27(Kip1) and down-regulated CDK2 and c-Myc to promote cell cycle arrest in G0/G1. In xenograft studies, CAPE-pNO(2) remarkably suppressed tumour growth dose dependently and decreased the expression of VEGF (vascular endothelial growth factor) in tumour tissue. Moreover, HE staining showed that no observable toxicity was found in the heart, liver, kidney and spleen. In addition, metabolites of CAPE-pNO(2) in HT-29 cells and organs were detected. In conclusion, para-nitro may enhance the anticancer effect of CAPE by inhibiting colon cancer cell viability, inducing apoptosis and cell cycle arrest via the P53 pathway and inhibiting tumour growth and reducing tumour invasion by decreasing the expression of VEGF; additionally, metabolites of CAPE-pNO(2) showed differences in cells and organs.