Androgen regulation of the cell-cell adhesion molecule-1 (Ceacam1) gene

High-calorie diet exacerbates prostate neoplasia in mice with haploinsufficiency of Pten tumor suppressor gene

Objective

Association between prostate cancer and obesity remains controversial. Allelic deletions of PTEN, a tumor suppressor gene, are common in prostate cancer in men. Monoallelic Pten deletion in mice causes low prostatic intraepithelial neoplasia (mPIN). This study tested the effect of a hypercaloric diet on prostate cancer in Pten^+/− mice.

Methods

1-month old mice were fed a high-calorie diet deriving 45% calories from fat for 3 and 6 months before prostate was analyzed histologically and biochemically for mPIN progression. Because Pten^+/− mice are protected against diet-induced insulin resistance, we tested the role of insulin on cell growth in RWPE-1 normal human prostatic epithelial cells with siRNA knockdown of PTEN.

Results

In addition to activating PI3 kinase/Akt and Ras/MAPkinase pathways, high-calorie diet causes neoplastic progression, angiogenesis, inflammation and epithelial–mesenchymal transition. It also elevates the expression of fatty acid synthase (FAS), a lipogenic gene commonly elevated in progressive cancer. SiRNA-mediated downregulation of PTEN demonstrates increased cell growth and motility, and soft agar clonicity in addition to elevation in FAS in response to insulin in RWPE-1 normal human prostatic cells. Downregulating FAS in addition to PTEN, blunted the proliferative effect of insulin (and IL-6) in RWPE-1 cells.

Conclusion

High-calorie diet promotes prostate cancer progression in the genetically susceptible Pten haploinsufficient mouse while preserving insulin sensitivity. This appears to be partly due to increased inflammatory response to high-caloric intake in addition to increased ability of insulin to promote lipogenesis.

CEA-Related CAMs

The carcinoembryonic antigen (CEA) family comprises a large number of cellular surface molecules, the CEA-related cell adhesion molecules (CEACAMs), which belong to the Ig superfamily. CEACAMs exhibit a complex expression pattern in normal and malignant tissues. The majority of the CEACAMs are cellular adhesion molecules that are involved in a great variety of distinct cellular processes, for example in the integration of cellular responses through homo- and heterophilic adhesion and interaction with a broad selection of signal regulatory proteins, i.e., integrins or cytoskeletal components and tyrosine kinases. Moreover, expression of CEACAMs affects tumor growth, angiogenesis, cellular differentiation, immune responses, and they serve as receptors for commensal and pathogenic microbes. Recently, new insights into CEACAM structure and function became available, providing further elucidation of their kaleidoscopic functions.

Vitamin D inhibits CEACAM1 to promote insulin/IGF-I receptor signaling without compromising anti-proliferative action

Population studies suggest putative links between vitamin D (VD)-deficiency and risk of cancer and diabetes. The insulin/IGF-I receptor represents a signaling target of the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) that is implicated in both diabetes and cancer, therefore we hypothesized that VD actions may be mediated through this adhesion molecule. In this study, we show that 1,25 vitamin D3 and its analogues EB1089 and KH1060 potently inhibit CEACAM1 expression in cancer cells. This effect was associated with significant reductions in mRNA and protein levels, resulting from transcriptional and posttranslational actions respectively. Insulin/IGF-I-mediated IRS-1 and Akt activation were enhanced by VD treatment. Similarly, CEACAM1 downregulation significantly upregulated the insulin and IGF-I receptors and mimicked the effect of VD-mediated enhanced insulin/IGF-I receptor signaling. Despite improved insulin/IGF-I signaling, the anti-proliferative actions of VD were preserved in the absence or presence of forced CEACAM1 expression. Forced CEACAM1, however, abrogated the anti-invasive actions of VD. Our findings highlight CEACAM1 as a target of VD action. The resulting inhibition of CEACAM1 has potentially beneficial effects on metabolic disorders without necessarily compromising the anticancer properties of this vitamin.

Susceptibility to diet-induced hepatic steatosis and glucocorticoid resistance in FK506-binding protein 52-deficient mice

Although FK506-binding protein 52 (FKBP52) is an established positive regulator of glucocorticoid receptor (GR) activity, an in vivo role for FKBP52 in glucocorticoid control of metabolism has not been reported. To address this question, FKBP52(+/-) mice were placed on a high-fat (HF) diet known to induce obesity, hepatic steatosis, and insulin resistance. Tissue profiling of wild-type mice showed high levels of FKBP52 in the liver but little to no expression in muscle or adipose tissue, predicting a restricted pattern of FKBP52 effects on metabolism. In response to HF, FKBP52(+/-) mice demonstrated a susceptibility to hyperglycemia and hyperinsulinemia that correlated with reduced insulin clearance and reduced expression of hepatic CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1), a mediator of clearance. Livers of HF-fed mutant mice had high lipid content and elevated expression of lipogenic genes (peroxisome proliferator-activated receptor gamma, fatty acid synthase, and sterol regulatory element-binding protein 1c) and inflammatory markers (TNFalpha). Interestingly, mutant mice under HF showed elevated serum corticosterone, but their steatotic livers had reduced expression of gluconeogenic genes (phosphoenolpyruvate carboxy kinase, glucose 6 phosphatase, and pyruvate dehydrogenase kinase 4), whereas muscle and adipose expressed normal to elevated levels of glucocorticoid markers. These data suggest a state of glucocorticoid resistance arising from liver-specific loss of GR activity. Consistent with this hypothesis, reduced expression of gluconeogenic genes and CEACAM1 was observed in dexamethasone-treated FKBP52-deficient mouse embryonic fibroblast cells. We propose a model in which FKBP52 loss reduces GR control of gluconeogenesis, predisposing the liver to steatosis under HF-diet conditions attributable to a shunting of metabolism from glucose production to lipogenesis.

Generation of human CEACAM1 transgenic mice and binding of Neisseria Opa protein to their neutrophils

BACKGROUND

Human CEACAM1 is a cell-cell adhesion molecule with multiple functions including insulin clearance in the liver, vasculogenesis in endothelial cells, lumen formation in the mammary gland, and binding of certain human pathogens.

PRINCIPAL FINDINGS

Three genomic BAC clones containing the human CEACAM1 gene were microinjected into pronuclei of fertilized FVB mouse oocytes. The embryos were implanted in the oviducts of pseudopregnant females and allowed to develop to term. DNA from newborn mice was evaluated by PCR for the presence of the human CEACAM1 gene. Feces of the PCR positive offspring screened for expression of human CEACAM1. Using this assay, one out of five PCR positive lines was positive for human CEACAM1 expression and showed stable transmission to the F1 generation with the expected transmission frequency (0.5) for heterozygotes. Liver, lung, intestine, kidney, mammary gland, and prostate were strongly positive for the dual expression of both murine and human CEACAM1 and mimic that seen in human tissue. Peripheral blood and bone marrow granulocytes stained strongly for human CEACAM1 and bound Neisseria Opa proteins similar to that in human neutrophils.

CONCLUSION

These transgenic animals may serve as a model for the binding of human pathogens to human CEACAM1.

Stimulation of CEACAM1 expression by 12- O -tetradecanoylphorbol-13-acetate (TPA) and calcium ionophore A23187 in endometrial carcinoma cells

Downregulation of carcinoembryonic antigen-related cell adhesion molecule (CEACAM1), a cell adhesion molecule with tumor suppressing properties has been observed in a high percentage of carcinomas of the endometrium and other malignancies. The mechanisms for the dysregulation and the role of hormones and cytokines on the expression of CEACAM1 in endometrial carcinomas is unknown. We therefore studied the effect of estradiol, medroxyprogesterone acetate (MPA), RU486, gamma-interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), 12-O-tetradecanoylphorbol-13-acetate (TPA) and calcium ionophore A23187 on the expression in the non-expressing endometrial tumor cell lines Hec1B and Skut1B, respectively. No induction of CEACAM1 expression was observed in Hec1B endometrial adenocarcinoma cells in response to hormones and cytokines whereas treatment with TPA and calcium ionophore A23187 resulted in the strong expression of endogenous CEACAM1 on the mRNA and protein levels. In contrast, no induction of CEACAM1 expression was observed in endometrial mixed mesenchymal Skut1B cells. Studies of other members of the CEACAM family revealed that the re-expression in Hec1B carcinoma cells is restricted to CEACAM1 suggesting a cell type-specific and cell type-independent mechanism of CEACAM1 activation via the protein kinase C (PKC) pathway. Induction of CEACAM1 expression was dependent on protein kinase C protein synthesis and luciferase reporter assays with CEACAM1 promoter constructs demonstrated that the re-expression of CEACAM1 is regulated at the transcriptional level. This is the first report demonstrating that activators of PKC are able to specifically induce the expression of CEACAM1 in human carcinoma cells and our findings may provide a basis for the therapeutic inhibition of tumor growth in malignancies in which CEACAM1 is downregulated.

Negative modulation of androgen receptor transcriptional activity by Daxx

The transcriptional activity of the androgen receptor (AR) modulated by positive or negative regulators plays a critical role in controlling the growth and survival of prostate cancer cells. Although numerous positive regulators have been identified, negative regulators of AR are less well understood. We report here that Daxx functions as a negative AR coregulator through direct protein-protein interactions. Overexpression of Daxx suppressed AR-mediated promoter activity in COS-1 and LNCaP cells and AR-mediated prostate-specific antigen expression in LNCaP cells. Conversely, downregulation of endogenous Daxx expression by RNA interference enhances androgen-induced prostate-specific antigen expression in LNCaP cells. In vitro and in vivo interaction studies revealed that Daxx binds to both the amino-terminal and the DNA-binding domain of the AR. Daxx proteins interfere with the AR DNA-binding activity both in vitro and in vivo. Moreover, sumoylation of AR at its amino-terminal domain is involved in Daxx interaction and trans-repression. Together, these findings not only provide a novel role of Daxx in controlling AR transactivation activity but also uncover the mechanism underlying sumoylation-dependent transcriptional repression of the AR.

Identification of Sp2 as a transcriptional repressor of carcinoembryonic antigen-related cell adhesion molecule 1 in tumorigenesis

Down-regulation of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) tumor suppressor gene expression is common in several malignancies including prostate, colon, and breast cancer. The mechanism that mediates this down-regulation is not known. Here, we report that down-regulation of CEACAM1 expression in prostate cancer cells occurs primarily at the transcriptional level and is mediated by Sp2, a member of the Sp family of transcription factors. Sp2 binds to the CEACAM1 promoter in vitro and in vivo, and transient overexpression of Sp2 down-regulates endogenous CEACAM1 expression in normal prostate epithelial cells. Sp2 appears to repress CEACAM1 gene expression by recruiting histone deacetylase activity to the CEACAM1 promoter. In human prostate cancer specimens, Sp2 expression is high in prostate cancer cells but low in normal prostate epithelial cells and is inversely correlated with CEACAM1 expression. Our studies show that transcriptional repression by Sp2 represents one mechanism by which CEACAM1 tumor suppressor gene is down-regulated in prostate cancer.

AKT-independent protection of prostate cancer cells from apoptosis mediated through complex formation between the androgen receptor and FKHR

Recent studies suggested that the protection of cell apoptosis by AKT involves phosphorylation and inhibition of FKHR and related FOXO forkhead transcription factors and that androgens provide an AKT-independent cell survival signal in prostate cancer cells. Here, we report receptor-dependent repression of FKHR function by androgens in prostate cancer cells. Transcriptional analysis demonstrated that activation of the androgen receptor caused an inhibition of both wild-type FKHR and a mutant in which all three known AKT sites were mutated to alanines, showing that the repression is AKT independent. In vivo and in vitro coprecipitation studies demonstrated that the repression is mediated through protein-protein interaction between FKHR and the androgen receptor. Mapping analysis localized the interacting domains to the carboxyl terminus between amino acids 350 and 655 of FKHR and to the amino-terminal A/B region and the ligand binding domain of the receptor. Further analysis demonstrated that the activated androgen receptor blocked FKHR's DNA binding activity and impaired its ability to induce Fas ligand expression and prostate cancer cell apoptosis and cell cycle arrest. These studies identify a new mechanism for androgen-mediated prostate cancer cell survival that appears to be independent of the activity of the receptor on androgen response element-mediated transcription and establish FKHR and related FOXO forkhead proteins as important nuclear targets for both AKT-dependent and -independent survival signals in prostate cancer cells.