6-C-(E-phenylethenyl)naringenin induces cell growth inhibition and cytoprotective autophagy in colon cancer cells

6-C-(E-phenylethenyl)naringenin (6-CEPN) is a small molecule found in naringenin fortified fried beef. It has been shown to suppress colon Cancer cell proliferation, but the underlying mechanisms are not fully understood. Here we demonstrate that 6-CEPN suppresses tumour cell proliferation through cell cycle arrest in G₁ phase, induces necrotic cell death and Autophagy in colon Cancer cells. Blockade of Autophagy by knockdown of the essential Autophagy proteins, Atg7 or beclin-1, resulted in aggravated cell death in response to 6-CEPN treatment. In addition, genome-wide transcriptome expression profiling by RNA-sequencing revealed that 6-CEPN-mediated gene expression pattern was extremely similar to the transcriptome response induced by a Ras Inhibitor salirasib (farnesylthiosalicylic acid [FTS; salirasib]). Subsequent molecular biological and biochemical experiments demonstrated that 6-CEPN indeed strongly inhibited Ras activation, leading to the inhibition of the downstream effector pathways c-Raf/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase kinase and phosphoinositide 3-kinase/Akt/mammalian target of rapamycin. More importantly, our computational molecular docking data showed that 6-CEPN could bind to the active site of isoprenylcysteine carboxyl methyltransferase (ICMT), a critical Enzyme for the activation of Ras. ICMT activity assay showed that 6-CEPN inhibited its activity significantly. Knockdown of ICMT by siRNA attenuated 6-CEPN-mediated Autophagy and cell death. The present study demonstrates that 6-CEPN induces cell growth inhibition and cytoprotective Autophagy in colon Cancer cells, at least in part, though inhibition of the ICMT/Ras signalling pathways.

6-CEPN; Anticancer; Colon cancer; RAS.