Transgenic mice expressing human cholesteryl ester transfer protein (HuCETPTg mice) were crossed with apolipoprotein CI-knocked out (apoCI-KO) mice. Although total cholesterol levels tended to be reduced as the result of CETP expression in HuCETPTg heterozygotes compared with C57BL6 control mice (؊13%, not significant), a more pronounced decrease (؊28%, p < 0.05) was observed when human CETP was expressed in an apoCI-deficient background (HuCETPTg/apoCI-KO mice). Gel permeation chromatography analysis revealed a significant, 6.1-fold rise (p < 0.05) in the cholesteryl ester content of very low density lipoproteins in HuCETPTg/apoCI-KO mice compared with control mice, whereas the 2.7-fold increase in HuCETPTg mice did not reach the significance level in these experiments. Approximately 50% decreases in the cholesteryl ester content and cholesteryl ester to triglyceride ratio of high density lipoproteins (HDL) were observed in HuCETPTg/apoCI-KO mice compared with controls (p < 0.05 in both cases), with intermediate ؊20% changes in HuCETPTg mice. The cholesteryl ester depletion of HDL was accompanied with a significant reduction in their mean apparent diameter (8.68 ؎ 0.04 nm in HuCETPTg/apoCI-KO mice versus 8.83 ؎ 0.02 nm in control mice; p < 0.05), again with intermediate values in HuCETPTg mice (8.77 ؎ 0.04 nm). In vitro purified apoCI was able to inhibit cholesteryl ester exchange when added to either total plasma or reconstituted HDL-free mixtures, and coincidently, the specific activity of CETP was significantly increased in the apoCI-deficient state (173 ؎ 75 pmol/g/h in HuCETPTg/apoCI-KO mice versus 72 ؎ 19 pmol/g/h in HuCETPTg, p < 0.05). Finally, HDL from apoCI-KO mice were shown to interact more readily with purified CETP than control HDL that differ only by their apoCI content. Overall, the present observations provide direct support for a potent specific inhibition of CETP by plasma apoCI in vivo.

Fatty acid synthase (FASN), a key player in the de novo synthetic pathway of long-chain fatty acids, has been shown to contribute to the tumorigenesis in various types of solid tumors. We here report that FASN is highly and consistently expressed in mantle cell lymphoma (MCL), an aggressive form of B-cell lymphoid malignancy. Specifically, the expression of FASN was detectable in all four MCL cell lines and 15 tumors examined. In contrast, benign lymphoid tissues and peripheral blood mononuclear cells from normal donors were negative. Treatment of MCL cell lines with orlistat, a FASN inhibitor, resulted in significant apoptosis. Knockdown of FASN expression using siRNA, which also significantly decreased the growth of MCL cells, led to a dramatic decrease in the cyclin D1 level. β-catenin, which has been previously reported to be upregulated in a subset of MCL tumors, contributed to the high level of FASN in MCL cells, Interesting, siRNA knock-down of FASN in turn down-regulated β-catenin. In conclusion, our data supports the concept that FASN contributes to the pathogenesis of MCL, by collaborating with β-catenin. In view of its high and consistent expression in MCL, FASN inhibitors may hold promises for treating MCL.

Human plasma, unlike mouse plasma, contains the cholesteryl ester transfer protein (CETP) that may influence the reverse cholesterol transport. Liver X receptor (LXR), an oxysterol-activated nuclear receptor induces CETP transcription via a direct repeat 4 element in the CETP gene promoter. The aim of the study was to assess in vivo the impact of LXR activation on CETP expression and its consequences on plasma lipid metabolism and hepatic and bile lipid content. Wild-type and humanized mice expressing CETP were treated for five days with T0901317 LXR agonist. This treatment produced marked rises in both hepatic CETP mRNA and plasma CETP activity levels. Interestingly, the LXR agonist-mediated, 2-fold rise in both total and HDL cholesterol levels in treated wild-type mice was not observed in CETPTg mice, and the accumulation of cholesterol in the liver of Recently, the use of synthetic liver X receptor (LXR) agonists appeared as a potential new pharmacological approach to stimulating reverse cholesterol transport (RCT) in vivo (1, 2). LXRs ␣ and ␤ are nuclear receptors that are activated by oxysterols (3, 4). They are involved in the regulation of cholesterol homeostasis, lipogenesis, glucose metabolism, and inflammation (4-9). Moreover, LXR agonist administration inhibits the development of atherosclerosis in LDL receptor (LDLR)-deficient and apolipoprotein E (apoE)-deficient mouse models, an effect that probably results from the modulation of the expression of both metabolic and inflammatory genes (10, 11). With regard to cholesterol metabolism, LXRs regulate RCT by inducing the expression of genes that are involved in cellular efflux, plasma transport, and biliary excretion of cholesterol. In animal models, the activation of LXR by synthetic agonists was shown to increase plasma HDL concentration, probably as the result of the induction of phospholipid transfer protein (PLTP), and ATP binding cassette (ABC) transporters A1 and G1 (12-14). LXR activation is also associated with a decrease in cholesterol content of the liver, an increase in biliary cholesterol secretion, and an increase in fecal neutral sterol excretion (5,15,16). Expression of the transporters ABCG5/G8 is known to be required for the latter phenomena to occur (15).It is worth noting that most of the previous studies with LXR agonists were conducted in the mouse, an animal model having no plasma cholesteryl ester transfer protein (CETP) activity (17). CETP is a plasma glycoprotein that promotes the exchange of neutral lipids, i.e., cholesteryl Abbreviations: CE, cholesteryl ester; CETP, cholesteryl ester transfer protein; LXR, liver X receptor; PLTP, phospholipid transfer protein; RCT, reverse cholesterol transport; SREBP, sterol-responsive element binding protein.

Mantle cell lymphoma (MCL) is a type of aggressive B-cell non-Hodgkin's lymphoma characterized by frequent resistance to conventional chemotherapy. In this study we provided evidence that fenofibrate, which is widely known as an agonist for peroxisome proliferator-activated receptor-a (PPARa), can induce effective apoptosis in treating MCL cells. Addition of fenofibrate to MCL cell lines significantly decreased the number of viable cells by 50% at approximately 20 lM at 72 h. This decrease in cell growth was due to apoptosis, as evidenced by the cleavage of caspase 3 and poly(ADP-ribose) polymerase. The fenofibrate-mediated effects were not significantly affected by GW6471, a specific PPARa antagonist. Using an apoptosis pathway-specific oligonucleotide array, we found that fenofibrate significantly downregulated several pro-survival genes, including tumor necrosis factor-a (TNFa). Importantly, addition of recombinant TNF-a conferred partial protection against fenofibrate-induced apoptosis. Fenofibrate also decreased the nuclear translocation of nuclear factor (NF)-jB-p65 and significantly inhibited the DNA binding of NF-jB in a dose-dependent manner. To conclude, fenofibrate shows efficacy against MCL, and the mechanism can be attributed to its inhibitory effects on the TNF-a/NF-jB signaling axis. In view of the documented safety of fenofibrate in humans, it may provide a valuable therapeutic option for MCL patients.

Mantle cell lymphoma (MCL) is a specific type of aggressive B-cell non-Hodgkin lymphoma. We recently found that IL-22RA1, one of the two subunits of the interleukin 22 (IL-22) receptor, is expressed in MCL cell lines but not benign lymphocytes. In view of normal functions of IL-22 signaling, we hypothesized that the aberrant expression of IL-22RA1 may contribute to the deregulation of various cell signaling pathways, thereby promoting cell growth in MCL. In this study, we first demonstrated the expression of IL-22RA1 in all three MCL cell lines and eight frozen tumors examined using reverse transcription-polymerase chain reaction and Western blot analysis. In support of the concept that IL-22 signaling is biologically important in MCL, we found that MCL cells treated with recombinant IL-22 had a significant increase in cell growth that was associated with STAT3 activation. To investigate the mechanism underlying the aberrant expression of IL-22RA1, we analyzed the gene promoter of IL-22RA1, and we found multiple binding sites for NF-κB, a transcriptional factor strongly implicated in the pathogenesis of MCL. Pharmacologic inhibition of NF-κB resulted in a substantial reduction in the level of IL-22RA1 protein expression in MCL cells. To conclude, IL-22RA is aberrantly expressed in MCL, and we have provided evidence that IL-22 signaling contributes to the pathogenesis of MCL.