Down-regulation of X-linked inhibitor of apoptosis synergistically enhanced peroxisome proliferator-activated receptor γ ligand-induced growth inhibition in colon cancer

Abstract

We found previously that X-linked inhibitor of apoptosis protein (XIAP), a potent endogenous inhibitor of apoptosis, is overexpressed in colon cancer. Ligand-induced activation of peroxisome proliferator-activated receptor ; (PPAR;) has been shown to exert proapoptotic and antiproliferative effects in many cancer cell types. However, neither XIAP down-regulation alone nor monotherapy using PPAR; ligands is potent enough to control colon cancer. We explored whether XIAP inhibition and PPAR; activation offer a synergistic anticancer effect in colon cancer. HCT116-XIAP

Peroxisome Proliferator-Activated Receptor-γ Contributes to the Inhibitory Effects of Embelin on Colon Carcinogenesis

“…Human colon cancer cell line HCT116 was cultured in McCoy's 5A medium as we described (1). Empty vector pcDNA3 for control transfection was purchased from Invitrogen.…”

“…Cell proliferation was determined by [ 3 H]thymidine incorporation assay (19). Apoptosis was detected by cell death ELISA assay, Annexin V/PI staining, and caspase 3 activity assay, as reported previously (1,19,20).…”

“…Primers used for human PPARg detection were forward, 5 ¶-GGTGGCCATCCGCATCT-3 ¶; reverse, 5 ¶-TGCTTTTGGCATACTCTGT-GATCT-3 ¶. Western blot was performed as we described (1,2).…”

“…We have recently observed that down-regulation of XIAP (X-linked inhibitor of apoptosis protein) coupled with peroxisome proliferator-activated receptor-g (PPARg) ligands could synergistically induce apoptosis in colon cancer cells, and such an approach could significantly suppress the growth of colon cancer in mice (1)(2)(3). Indeed, XIAP plays a critical role in the resistance of many cancer cells to chemotherapy and radiotherapy (4,5).…”

Embelin Reduces Colitis-Associated Tumorigenesis through Limiting IL-6/STAT3 Signaling

“…Western blot analysis and qPCR were performed as we described (12,20), and the following primary antibodies were used: anti-glyceraldehyde-3-phosphatedehydrogenase (GAPDH, Abcam), anti-p-STAT3, anti-STAT3, antiTyr580 phoshho-SHP2 (p-SHP2), anti-SHP2 (Cell Signaling Technology), anti-IL-6Ra and anti-gp130 (Santa Cruz). All secondary antibodies were from Dako.…”