Effect of MED28 on Glucose Transporters and Glycolysis in Human Colorectal Cancer Cells
Abstract Objectives MED28 exhibits several cellular roles, including a Mediator subunit for transcriptional activation as well as an interactor with merlin, NF2 tumor suppressor protein, and Grb2, a signaling adaptor. Our laboratory has previously reported that MED28 not only mediates cell growth but also appears to regulate glucose metabolism in human colorectal cancer cells. Therefore, the objective of the current study is to investigate the in vivo effect of MED28 on glucose metabolism and cell growth in colorectal cancer. Methods HCT116 colorectal cancer cells were transfected with MED28 siRNA or non-target siRNA for 72 h, and then undergone Western blotting or immunofluorescence analysis, by incubating with anti-c-Myc antibodies and DAPI for nuclear staining. We also established shMED28-transfected HCT116 cells and employed a NOD/SCID immunodeficient mouse xenograft model by subcutaneously implanting 1 × 107 stably transfected cells to the flanks of the animals to study the in vivo effect of MED28 expression on glucose metabolism. The animal study continued for 21 days, and the animal use protocol was approved by the Institutional Animal Care and Use Committee. The subcutaneous tumors were analyzed for the expression of MED28, glucose transporter 1 (GLUT1), and glycolysis-associated enzymes, including hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA). Results The expression of c-Myc was decreased upon MED28 knockdown in HCT116 cells. Our in vivo data indicated smaller xenograft volumes and lower expression levels of MED28, GLUT1, HK2, and LDHA in tumors carrying shMED28-transfected HCT116 cells than those of control counterparts. Conclusions MED28 upregulates glucose transporters and glycolysis-associated enzymes as well as cell growth in NOD/SCID subcutaneous xenografts, suggesting nutrient-gene interactions between glucose metabolism and MED28 in human colorectal cancer cells. Funding Sources This work was supported by the grants MOST106–2320-B-039–062-MY3 and CMU108-SR-31 to M-F Lee, and MOST108–2813-C-039–058-B to Y-T Chang.
