Retinoic acid synergizes with cyclic AMP to enhance MMP-2 basal promoter activity

A mechanistic study on the metastasis inducing function of FUS-CHOP fusion protein in liposarcoma

The FUS-CHOP fusion protein has been found to be instrumental for specific oncogenic processes in liposarcoma, but its ability to induce metastasis and the underlying mechanisms by which this can be achieved remain unknown. To dissect its functional role in this context, we stably overexpressed this protein in SW872 liposarcoma and HT1080 fibrosarcoma cell lines, and were able to demonstrate that forced expression of FUS-CHOP significantly increases migration and invasion, as well as enhances lung and liver metastasis in the in vivo chicken chorioallantoic membrane (CAM) model, that is proliferation independent. Additionally, FUS-CHOP enhances the expression of matrix-metalloproteinases -2 and -9, and transactivates their promoters in vitro. Mutational analysis showed that C/EBP-β- (-769/-755), NF-κB (-525/-516) and CREB/AP-1 (-218/-207) sites were important for MMP-2 and NF-κB (-604/-598), AP-1 (-539/-532) and AP-1 (-81/-72) for MMP-9 transactivation. Moreover, a direct in vivo interaction of FUS-CHOP was observed in case of the MMP-2 promoter within region (-769/-207). siRNA data revealed that MMP-2 expression is essential in the FUS-CHOP induced metastatic phenotype. MMP-2-mRNA and protein expression correlated significantly with FUS-CHOP positivity in 46 resected patient liposarcoma tissues. We have for the first time provided substantial evidence for the FUS-CHOP oncoprotein as an inducer of metastasis that is due to the transcriptional induction of specific tumor-associated proteases. Insights gained from this study not only support a deeper understanding of the mechanistic properties of FUS-CHOP, but also open up new avenues for targeted therapy.

C/EBPepsilon directs granulocytic-vs-monocytic lineage determination and confers chemotactic function via Hlx

OBJECTIVE

Mutations in the CCAAT enhancer binding protein epsilon (C/EBPepsilon) gene have been identified in the cells of patients with neutrophil specific granule deficiency, a rare congenital disorder marked by recurrent bacterial infections. Their neutrophils, in addition to lacking specific granules required for normal respiratory burst activity, also lack normal phagocytosis and chemotaxis. Although the specific granule deficiency phenotype has been replicated in C/EBPepsilon(-/-) (knockout [KO]) mice, the mechanisms by which C/EBPepsilon mutations act to decrease neutrophil function are not entirely clear.

MATERIALS AND METHODS

In order to determine the role of C/EBPepsilon in neutrophil differentiation and migration, we generated immortalized progenitor cell lines from C/EBPepsilon KO and wild-type mice and performed expression and flow cytometric analysis and functional studies.

RESULTS

Expression of lineage-specific cell surface antigens on our in vitro differentiated cell lines revealed persistent expression of monocytic markers on KO granulocytes. We verified this in primary murine peripheral blood and bone marrow cells. In addition, KO bone marrow had an increase in immature myeloid precursors at the common myeloid progenitor and granulocyte/monocyte progenitor levels, suggesting a critical role for C/EBPepsilon not only in granulocyte maturation beyond the promyelocyte stage, but also in the monocyte/granulocyte lineage decision. We found that restoration of Hlx (H2.0-like homeo box 1) expression, which was decreased in C/EBPepsilon KO cells, rescued chemotaxis, but not the other defects of C/EBPepsilon KO neutrophils.

CONCLUSIONS

We show two new regulatory functions of C/EBPepsilon in myelopoiesis: in the absence of C/EBPepsilon, there is not only incomplete differentiation of granulocytes, but myelopoiesis is disrupted with the appearance of an intermediate cell type with monocyte and granulocyte features, and the neutrophils have abnormal chemotaxis. Restoration of expression of Hlx provides partial recovery of function; it has no effect on neutrophil maturation, but can completely ameliorate the chemotaxis defect in C/EBPepsilon KO cells.

Human CC chemokine CCL23 enhances expression of matrix metalloproteinase-2 and invasion of vascular endothelial cells

Human CCL23 (also known as CKbeta8, MPIF-1, or MIP-3) has been recently reported to induce endothelial cell migration and tube formation via CCR1. Matrix metalloproteinases (MMPs) are involved in the degradation of the extracellular matrix and also appear to play critical roles in angiogenesis. In the present study, we have demonstrated that CCL23 enhances the expression of MMP-2 mRNA and protein levels in endothelial cells in a dose-dependent manner, but has no effect on the expression levels of MMP-9, TIMP-1, TIMP-2, and MT1-MMP. CCL23 was shown to dose-dependently activate the expression of the MMP-2/Luc reporter gene, thereby indicating that it stimulates the transcription of the MMP-2 gene. Vascular endothelial cells, when exposed to CCL23, showed a marked ability to invade through a 3D Matrigel. This increase in invasion was also correlated with enhancements in the expression and activity of MMP-2. Neutralization with anti-CCL23 and anti-CCR1 antibodies, as well as the heat-induced inactivation of CCL23, resulted in a blockage of the CCL23-activated invasion, indicating that the invasion of HUVECs was induced by CCL23 specifically. Furthermore, we showed that the CCL23-induced invasion was inhibited by MMP inhibitors such as GM6001 and a specific MMP-2 Inhibitor I. Our results indicate that CCL23 may play a direct role in angiogenesis, via the upregulation of MMP-2 expression.

Modulation of hepatocyte growth factor induction in human skin fibroblasts by retinoic acid

Topical treatment of skin with all-trans-retinoic acid (ATRA), the major biologically active form of vitamin A, results in hyperproliferation of basal keratinocytes, leading to an accelerated turnover of epidermis cells and thickening of the epidermis, probably via induction of production of paracrine growth factors for keratinocytes in epidermal suprabasal keratinocytes and/or dermal fibroblasts. Since hepatocyte growth factor (HGF) is a factor mitogenic to epidermal keratinocytes secreted from dermal fibroblasts, the effect of ATRA on basal and induced HGF production in human dermal fibroblasts in culture was examined. ATRA alone did not induce HGF production, but it significantly enhanced HGF production induced by the cAMP-elevating agent cholera toxin or the membrane-permeable cAMP analog 8-bromo-cAMP. Cholera toxin-induced activation of cAMP responsive element (CRE)-binding protein (CREB) was enhanced by pretreating cells with ATRA for 24 h. In contrast, HGF production induced by epidermal growth factor (EGF) or phorbol 12-myristate 13-acetate (PMA) was potently inhibited by ATRA. These modulatory effects of ATRA were different from the effects of transforming growth factor-beta1 (TGF-beta) and dexamethasone, both of which inhibited HGF production induced by all of the four inducers. Up-regulation of HGF gene expression by cholera toxin and EGF was also enhanced and inhibited, respectively, by ATRA. Both 9-cis-retinoic acid (9-cis-RA) and 13-cis-retinoic acid (13-cis-RA), which are stereo-isomers of ATRA, showed a modulatory effect on HGF induction similar to that of ATRA. These results suggest that ATRA augments the induction of HGF production caused by increased intracellular cAMP.

Regulation of matrix metalloproteinases (type IV collagenases) and their inhibitors in the virgin, timed pregnant, and postpartum rat uterus and cervix by prostaglandin E(2)-cyclic adenosine monophosphate

OBJECTIVE

Our purpose was to examine whether the type IV collagenases (metalloproteinase [MMP]-2 and MMP-9) and their inhibitors (TIMP-1 and TIMP-2) are regulated by a prostaglandin E(2) (PGE(2))-cyclic adenosine monophosphate (cAMP) mechanism in nonpregnant virgin, preterm and term pregnant and postpartum rats.

STUDY DESIGN

Sprague-Dawley rats were infused with either saline solution or PGE(2) over 24 hours or were noninfused. Plasma and tissue were analyzed for cAMP, MMP-2 and MMP-9, and TIMP-1 and TIMP-2.

RESULTS

PGE(2) evoked elevations in plasma and tissue levels of cAMP and MMP-2 in the preterm and term pregnant rats. MMP-9 levels were elevated in the preterm plasma and uterus, whereas in the term pregnant and postpartum rats, MMP-9 levels were increased in the cervix.

CONCLUSIONS

MMP levels in the pregnant and postpartum rat uterus and cervix are regulated in part by a PGE(2)-cAMP mechanism. Specifically, MMP-9 may be involved in preterm labor, cervical maturity, and involution of the postpartum uterus.

ATF3 represses 72-kDa type IV collagenase (MMP-2) expression by antagonizing p53-dependent trans-activation of the collagenase promoter

The murine homologue of the ATF3 transcription factor increases tumor metastases but, surprisingly, represses 72-kDa type IV metalloproteinase (MMP-2) expression. The current study describes a novel mechanism by which ATF3 regulates transcription. Progressive deletions of the MMP-2 promoter indicated a 38-base pair region (-1659/-1622) necessary for the ATF3-mediated repression. This region lacked CREB/AP-1 motifs but contained a consensus p53 motif shown previously to regulate MMP-2 expression. The activity of a p53 response element-driven luciferase reporter was reduced in ATF3-expressing HT1080 clones. Although MMP-2 promoter activity was not repressed by ATF3 in p53-deficient Saos-2 cells, p53 re-expression increased MMP-2 promoter activity and restored the sensitivity to ATF3. The activity of a GAL4-driven reporter in HT1080 cells co-expressing the full-length p53 sequence fused to the GAL4 DNA binding domain was diminished by ATF3. p53-ATF3 protein-protein interactions were demonstrated both in vivo and in vitro. Cell cycle analysis, performed as an independent assay of p53 function, revealed that gamma-irradiation-induced slowed G(2)/M cell cycle progression (attributable to p53) was countered by ATF3. Thus, ATF3 represses MMP-2 expression by decreasing the trans-activation of this gene by p53.