Hepatoblastoma, the most common pediatric liver cancer, is tightly linked to excessive Wnt/beta-catenin signaling. Here, we used microarray analysis to identify two tumor subclasses resembling distinct phases of liver development and a discriminating 16-gene signature. beta-catenin activated different transcriptional programs in the two tumor types, with distinctive expression of hepatic stem/progenitor markers in immature tumors. This highly proliferating subclass was typified by gains of chromosomes 8q and 2p and upregulated Myc signaling. Myc-induced hepatoblastoma-like tumors in mice strikingly resembled the human immature subtype, and Myc downregulation in hepatoblastoma cells impaired tumorigenesis in vivo. Remarkably, the 16-gene signature discriminated invasive and metastatic hepatoblastomas and predicted prognosis with high accuracy.

Tbx3 encodes a transcriptional repressor that is important for diverse patterning events during development, and Tbx3 mutation in humans causes the ulnar-mammary syndrome. Here, we describe the identification of Tbx3 in array-based search for genes downstream Wnt/B-catenin that are implicated in liver tumorigenesis. Overexpression of Tbx3 is closely associated with the mutational status of B-catenin in murine liver tumors induced by Myc as well as in human hepatocellular carcinomas and hepatoblastomas. Moreover, Tbx3 transcription is activated by ectopic expression of B-catenin in mouse liver and in human tumor cell lines. Evidence that Tbx3 transcription is directly regulated by B-catenin is provided by chromatin immunoprecipitation and reporter assays. Although HepG2 cells stably transfected with Tbx3 display moderately enhanced growth rate, the dominant negative mutant Tbx3-Y149S drastically inhibits hepatoma cell growth in vitro and in vivo. Moreover, small interfering RNAs (siRNA) directed against Tbx3 inhibit anchorageindependent growth of liver and colon carcinoma cells. We further show that inhibition of Tbx3 expression by specific siRNAs blocks B-catenin-mediated cell survival and renders cells sensitive to doxorubicin-induced apoptosis. Conversely, ectopic expression of Tbx3 inhibits apoptosis induced by B-catenin depletion. Marked overexpression of Tbx3 in a subset of hepatoblastomas is associated with chemotherapyresistant phenotype and unfavorable patient outcome. These results reveal an unsuspected role of Tbx3 as a mediator of B-catenin activities on cell proliferation and survival and as an important player in liver tumorigenesis. [Cancer Res 2007;67(3):901-10]

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Abbreviations: 3-MA, 3-methyladenine; AKT, v-akt murine thymoma viral oncogene homolog; ALB, albumin; ATG7, autophagyrelated 7; CD, cluster of differentiation; CD5L, CD5 molecule-like; FCS, fetal calf serum; FSL1, pam2CGDPKHPKSF; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; IL, interleukin; MAP1LC3A/B (LC3), microtubule-associated protein 1 light chain 3 a/b; LPS, lipopolysaccharide; LTA, lipoteichoic acid; MK, macrophages; MAPK, mitogen-activated protein kinase; moAb, monoclonal antibody;; NFKB, nuclear factor of kappa light polypeptide gene enhancer in B-cells; oxLDL, oxidized low-density lipoprotein; PB monocytes, peripheral blood monocytes; PBS, phosphate-buffered saline; PI3K, phosphoinositide 3-kinase; PIK3C3, phosphatidylinositol 3-kinase, catalytic subunit type 3; poAb, polyclonal antibody; PMA, phorbol 12-myristate 13-acetate; PtdIns3K, phosphatidylinositol 3-kinase; PtdIns3P, phosphatidylinositol 3-phosphate; r-HsCD5L, recombinant human (Homo sapiens) CD5L; RELA, v-rel avian reticuloendotheliosis viral oncogene homolog A; siRNA, short interference RNA; SRCR, scavenger receptor cysteine-rich; TBS, tris-buffered saline; TLRs, toll-like receptors; TNF, tumor necrosis factor.CD5L (CD5 molecule-like) is a secreted glycoprotein that participates in host response to bacterial infection. CD5L influences the monocyte inflammatory response to the bacterial surface molecules lipopolysaccharide (LPS) and lipoteichoic acid (LTA) by inhibiting TNF secretion. Here we studied the intracellular events that lead to macrophage TNF inhibition by human CD5L. To accomplish this goal, we performed functional analyses with human monocytic THP1 macrophages, as well as with peripheral blood monocytes. Inhibition of phosphatidylinositol 3-kinase (PtdIns3K) reversed the inhibitory effect of CD5L on TNF secretion. Among the various PtdIns3K isoforms, our results indicated that CD5L activates PtdIns3K (whose catalytic subunit is termed PIK3C3), a key modulator involved in autophagy. Further analysis revealed a concomitant enhancement of autophagy markers such as cellular LC3-II content, increased LC3 puncta, as well as LC3-LysoTracker Red colocalization. Moreover, electron microscopy showed an increased presence of cytosolic autophagosomes in THP1 macrophages overexpressing CD5L. Besides preventing TNF secretion, CD5L also inhibited IL1B and enhanced IL10 secretion. This macrophage anti-inflammatory pattern of CD5L was reverted upon silencing of autophagy protein ATG7 by siRNA transfection. Additional siRNA experiments in THP1 macrophages indicated that the induction of autophagy mechanisms by CD5L was achieved through cell-surface scavenger receptor CD36, a multiligand receptor expressed in a wide variety of cell types. Our data represent the first evidence that CD36 is involved in autophagy and point to a significant contribution of the CD5L-CD36 axis to the induction of macrophage autophagy.

CD5L (CD5 molecule-like) is a secreted glycoprotein that controls key mechanisms in inflammatory responses, with involvement in processes such as infection, atherosclerosis, and cancer. In macrophages, CD5L promotes an anti-inflammatory cytokine profile in response to TLR activation. In the present study, we questioned whether CD5L is able to influence human macrophage plasticity, and drive its polarization toward any specific phenotype. We compared CD5L-induced phenotypic and functional changes to those caused by IFN/LPS, IL4, and IL10 in human monocytes. Phenotypic markers were quantified by RT-qPCR and flow cytometry, and a mathematical algorithm was built for their analysis. Moreover, we compared ROS production, phagocytic capacity, and inflammatory responses to LPS. CD5L drove cells toward a polarization similar to that induced by IL10. Furthermore, IL10- and CD5L-treated macrophages showed increased LC3-II content and colocalization with acidic compartments, thereby pointing to the enhancement of autophagy-dependent processes. Accordingly, siRNA targeting ATG7 in THP1 cells blocked CD5L-induced CD163 and Mer tyrosine kinase mRNA and efferocytosis. In these cells, gene expression profiling and validation indicated the upregulation of the transcription factor ID3 by CD5L through ATG7. In agreement, ID3 silencing reversed polarization by CD5L. Our data point to a significant contribution of CD5L-mediated autophagy to the induction of ID3 and provide the first evidence that CD5L drives macrophage polarization.

These results provide evidence that PLC-PDX preclinical platform can strongly contribute to accelerate the identification and diversification of anticancer treatment for aggressive subtypes of pediatric liver cancer. (Hepatology 2016;64:1121-1135).

AIM is expressed by macrophages in response to agonists of the nuclear receptors LXR/RXR. In mice, it acts as an atherogenic factor by protecting macrophages from the apoptotic effects of oxidized lipids. In humans, it is detected in atherosclerotic lesions, but no role related to atherosclerosis has been reported. This study aimed to investigate whether the role of hAIM extends beyond inhibiting oxidized lipid-induced apoptosis. To accomplish this goal, functional analysis with human monocytic THP1 cells and macrophages differentiated from peripheral blood monocytes were performed. It was found that hAIM reduced oxLDL-induced macrophage apoptosis and increased macrophage adhesion to endothelial ICAM-1 by enhancing LFA-1 expression. Furthermore, hAIM increased foam cell formation, as shown by Oil Red O and Nile Red staining, as well as quantification of cholesterol content. This was not a result of decreased reverse cholesterol transport, as hAIM did not affect the efflux significantly from [(3)H] Cholesterol-laden macrophages driven by plasma, apoA-I, or HDL2 acceptors. Rather, flow cytometry studies indicated that hAIM increased macrophage endocytosis of fluorescent oxLDL, which correlated with an increase in the expression of the oxLDLR CD36. Moreover, hAIM bound to oxLDL in ELISA and enhanced the capacity of HEK-293 cells expressing CD36 to endocytose oxLDL, as studied using immunofluorescence microscopy, suggesting that hAIM serves to facilitate CD36-mediated uptake of oxLDL. Our data represent the first evidence that hAIM is involved in macrophage survival, adhesion, and foam cell formation and suggest a significant contribution to atherosclerosis-related mechanisms in the macrophage.

The LIM-only protein FHL2 acts as a transcriptional modulator that positively or negatively regulates multiple signaling pathways. We recently reported that FHL2 cooperates with CREB-binding protein/p300 in the activation of ␤-catenin/T cell factor target gene cyclin D1. In this paper, we demonstrate that FHL2 is associated with the cyclin D1 promoter at the T cell factor/CRE site, providing evidence that cyclin D1 is a direct target of FHL2. We show that deficiency of FHL2 greatly reduces the proliferative capacity of spontaneously immortalized mouse fibroblasts, which is associated with decreased expression of cyclin D1 and p16INK4a , and hypophosphorylation of Rb. Reexpression of FHL2 in FHL2-null fibroblasts efficiently restores cyclin D1 levels and cell proliferative capacity, indicating that FHL2 is critical for cyclin D1 activation and cell growth. Moreover, ectopic cyclin D1 expression is sufficient to override growth inhibition of immortalized FHL2-null fibroblasts. Gene expression profiling revealed that FHL2 deficiency triggers a broad change of the cell cycle program that is associated with down-regulation of several G 1 /S and G 2 /M cyclins, E2F transcription factors, and DNA replication machinery, thus correlating with reduced cell proliferation. This change also involves down-regulation of the negative cell cycle regulators, particularly INK4 inhibitors, which could counteract the decreased expression of cyclins, allowing cells to grow. Our study illustrates that FHL2 can act on different aspects of the cell cycle program to finely regulate cell proliferation.The LIM-only protein FHL2 is a member of the four-and-ahalf LIM (FHL) family (1). Individual LIM domains consist of two zinc finger motifs rich in cysteine and histidine that serve as protein-binding interface for the assembly of multiprotein complexes. The zinc fingers of some transcriptional regulators can interact with DNA, but there is no evidence for DNA binding activity of a LIM domain. FHL2 interacts with multiple transcription factors, including the androgen receptor, AP1, CREB, PLZF, SKI, and ␤-catenin (2-8). It functions as either a coactivator or a corepressor, depending on cell type and promoter contexts (7, 9). Moreover, FHL2 can bind several transcription factors simultaneously and participates in the assembly of multiprotein complexes (10, 11).FHL2 is found in both the cytoplasm and the nucleus (8, 12). In the cytoplasm, FHL2 interacts with integrins and focal adhesion kinase at focal adhesions (13,14). Integrins bind extracellular matrix proteins and certain cell surface receptors, serving as sensors for both chemical and mechanical cues (15). FHL2 shuttles between focal adhesions and nuclei to relay the flow of genetic information at different execution points. Serum response factor, which regulates the expression of immediate early genes, directly controls FHL2 expression in a RhoA-dependent manner (16), and the timing of FHL2 induction is coordinated with that of the early response proteins Fos and Jun (3). Following stimu...