Proanthocyanidins Inhibit In vitro and In vivo Growth of Human Non–Small Cell Lung Cancer Cells by Inhibiting the Prostaglandin E₂ and Prostaglandin E₂ Receptors

Abstract

Overexpression of cyclooxygenase-2 (COX-2) and prostaglandins (PG) is linked to a wide variety of human cancers. Here, we assessed whether the chemotherapeutic effect of grape seed proanthocyanidins (GSP) on non–small cell lung cancer (NSCLC) cells is mediated through the inhibition of COX-2 and PGE₂/PGE₂ receptor expression. The effects of GSPs on human NSCLC cell lines in terms of proliferation, apoptosis, and expression of COX-2, PGE₂, and PGE₂ receptors were determined using Western blotting, fluorescence-activated cell sorting analysis, and reverse transcription-PCR. In vitro treatment of NSCLC cells (A549, H1299, H460, H226, and H157) with GSPs resulted in significant growth inhibition and induction of apoptosis, which were associated with the inhibitory effects of GSPs on the overexpression of COX-2, PGE₂, and PGE₂ receptors (EP1 and EP4) in these cells. Treatment of cells with indomethacin, a pan-COX inhibitor, or transient transfection of cells with COX-2 small interfering RNA, also inhibited cell growth and induced cell death. The effects of a GSP-supplemented AIN76A control diet fed to nude mice bearing tumor xenografts on the expression of COX-2, PGE₂, and PGE₂ receptors in the xenografts were also evaluated. The growth-inhibitory effect of dietary GSPs (0.5%, w/w) on the NSCLC xenograft tumors was associated with the inhibition of COX-2, PGE₂, and PGE₂ receptors (EP1, EP3, and EP4) in tumors. This preclinical study provides evidence that the chemotherapeutic effect of GSPs on lung cancer cells in vitro and in vivo is mediated, at least in part, through the inhibition of COX-2 expression and subsequently the inhibition of PGE₂ and PGE₂ receptors. Mol Cancer Ther; 9(3); 569–80