Kruppel-like transcription factor 5 promotes breast cell survival through pERK-mediated MKP-1 protein stabilization

Abstract #3019

Kruppel-like Factor 5 (KLF5) is a transcription factor promoting cell survival and tumorigenesis in multiple cancers. High level of KLF5 mRNA is associated with a shorter survival for breast cancer patients. However, the role of KLF5 and mechanism of KLF5 actions in breast cancer remain unclear. In this study, we found that KLF5 knockdown by siRNA in two basal type breast cell lines MCF10A and BT20 induces apoptosis, as indicated by loss of cell viability and cleaved PARP and caspase 3. Interestingly, a survival phosphotase, MKP-1, is downregulated at protein level by KLF5 ablation. Consistently, KLF5 over-expression increases the MKP-1 protein expression. However, MKP-1 is not a KLF5 direct target gene because the MKP-1 mRNA level is not regulated by KLF5. By the cycloheximide chase assays, we found that KLF5 decreases the MKP-1 protein degradation. However, KLF5 does not decrease the MKP-1 E3 ubiquitin ligase SKP2 expression. The ERK inhibitor U0126 specifically blocks the KLF5 induced MKP-1, suggesting that KLF5 up-regulates MKP-1 through activating ERK signaling. Finally, we demonstrated that MKP-1 over-expression blocks KLF5 knockdown induced apoptosis in MCF10A cells. These findings suggest that KLF5 is a survival factor which promotes breast cell survival partially through pERK-mediated MKP-1 stabilization. The KLF5-pERK-MKP-1 signaling axis may provide new therapeutic targets for invasive breast cancer.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3019.

Krupple-like factor 5 promotes breast cancer proliferation through activating fibroblast growth factor-binding protein transcription

Abstract #4071

Breast cancer is the second leading cause of cancer death in U.S. women. The estrogen receptor negative basal breast cancer is usually invasive and the prognosis is poor. Kruppel-like Factor 5 (KLF5) is a zinc-finger transcription factor promoting cell proliferation, survival, cell cycle, and angiogenesis. High expression level of KLF5 has been shown to be associated with shorter breast cancer patient survival time. In our previous microarray studies, fibroblast growth factor binding protein (FGF-BP) is suggested to be one of the KLF5's downstream target genes in the TSU-Pr1 bladder cancer cell line. FGF-BP has been appreciated to be overexpressed in breast tumors and promotes tumorigenesis. To test whether KLF5 promotes cell proliferation through inducing FGF-BP gene transcription in breast cells, we first examined the KLF5 and FGF-BP protein levels in a panel of breast cell lines and found that KLF5 and FGF-BP are co-expressed in ER-negative basal breast cell lines. Over-expression of KLF5 by adenovirus dramatically increased the FGF-BP mRNA and protein expression in MCF7 and BT474. In contrast, KLF5 knockdown decreased the FGF-BP mRNA and protein expression in HCC1937, BT20, and SW527. Importantly, we found that FGF-BP, like KLF5, promotes cell proliferation in MCF10A, SW527 and TSU-Pr1 cells by H3-thymidine incorporation assay. Furthermore, we demonstrated that KLF5 activates the FGF-BP promoter through a putative KLF5 binding site by luciferase reporter assays. We further showed that KLF5 binds to the FGF-BP promoter in vitro by oligo pull down assays and in vivo by chromatin immunoprecipetation (CHIP) assays. These findings suggest that KLF5 may promote breast cancer cell proliferation through directly activating the FGF-BP mRNA transcription. This study will yield valuable insights into the mechanism of KLF5 induced cancer pathogenesis, and will result in useful diagnostic and therapeutic targets.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4071.

Sensitive biomarker of polycyclic aromatic hydrocarbons (PAHs): urinary 1-hydroxyprene glucuronide in relation to smoking and low ambient levels of exposure

The study was conducted in a Chinese population with occupational or environmental exposures to polycyclic aromatic hydrocarbons (PAHs). A total of 106 subjects were recruited from coke-oven workers (workers), residents in a metropolitan area (residents) and suburban gardeners (gardeners). All subjects were monitored twice for their personal exposures to PAHs. The biological samples were collected for measurements of 1-hydroxypyrene (1-OHP) and cotinine in urine. The geometric means of personal exposure levels of pyrene, benz(a)anthracene (BaA) and benzo(a)pyrene (BaP) in workers were 1.470, 0.978 and 0.805 microg m-3, respectively. The corresponding levels in residents were 0.050, 0.034 and 0.025 microg m-3; and those in gardeners were 0.011, 0.020 and 0.008 microg m-3, respectively. The conjugate of 1-OHP with glucuronide (1-OHP-G) is the predominant form of pyrene metabolite in urine and it showed strong associations with exposures not only to pyrene, but also to BaA, BaP and total PAHs. Most importantly, a significant difference in 1-OHP-G was even detected between the subgroups with exposures to BaP at < 0.010 and > 0.010 but < 0.020 microg m-3, suggesting that 1-OHP-G is a good marker that can be used for the risk assessment of BaP exposure at levels currently encountered in ambient air. Furthermore, multiple regression analyses of 1-OHP-G on PAHs exposure indicated that cigarette smoke was a major confounding factor and should be considered and adjusted for while using 1-OHP to estimate PAHs exposure.

cGMP-independent anti-tumour actions of the inhibitor of soluble guanylyl cyclase, ODQ, in prostate cancer cell lines

BACKGROUND AND PURPOSE

Soluble guanylyl cyclase (sGC) is a receptor for nitric oxide that generates cGMP. This second messenger molecule has established roles in cellular physiology; however, less is known about its effects in tumour cells.

EXPERIMENTAL APPROACH

The effects of 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and 4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one (NS2028), both selective sGC inhibitors on proliferation, death and migration were determined in prostate cancer cell lines.

KEY RESULTS

Western blot analysis confirmed the presence of alpha1 and beta1 subunits of sGC in LNCaP and PC-3 cells. Sodium nitroprusside (SNP) increased cGMP accumulation in LNCaP and PC-3, but not DU-145 cells. SNP-stimulated cGMP production in LNCaP cells was dose-dependently reduced by ODQ, with more than 90% inhibition being observed at 0.1 microM. ODQ activated caspase-3 in all three cell lines, but not in normal prostate epithelial cells, at concentrations over 10 muM. High concentrations of ODQ also promoted DNA fragmentation and nucleosome accumulation in the cytosol of LNCaP cells. Interestingly, the chemically related inhibitor, NS2028 was without effect on caspase-3. In addition, ODQ inhibited LNCaP, Du145 and PC-3 cell growth. Finally, although fibroblast growth factor-2 did not enhance cGMP levels in LNCaP cells, its ability to stimulate LNCaP motility was abolished by ODQ.

CONCLUSIONS AND IMPLICATIONS

These observations taken together suggest that the action of ODQ in LNCaP cells did not reflect sGC inhibition. We conclude that ODQ promotes cell death and inhibits growth and migration of prostate cancer cells and that these actions are independent of its effects on GMP levels.

Charge form factor of the neutron at low momentum transfer from the 2H-->(e-->,e'n)1H reaction

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.

Design of annular photonic crystal slabs

We present the design of realistic annular photonic-crystal (APC) structures of finite thickness aiming to obtain a complete photonic bandgap (PBG). The APC is composed of dielectric rods and circular air holes in a triangular lattice such that each rod is centered within each hole. The optical and geometrical values of the structure are studied, and the interplay between various design parameters is highlighted. The coupled role of the inner-dielectric-rod radius, material types, and slab thickness is investigated. It is shown that the slab thickness is vital to obtain a complete photonic bandgap below the light line, and the specific value of the inner-dielectric-rod radius to sustain the maximum PBG if the hole radius is fixed at proper value is found.

Covalent regulation of ULVWF string formation and elongation on endothelial cells under flow conditions

BACKGROUND AND OBJECTIVES

The adhesion ligand von Willebrand factor (VWF) is a multimeric glycoprotein that mediates platelet adhesion to exposed subendothelium. On endothelial cells, freshly released ultra-large (UL) VWF multimers form long string-like structures to which platelets adhere.

METHODS

The formation and elongation of ULVWF strings were studied in the presence of the thiol-blocking N-ethylmaleimide (NEM). The presence of thiols in ULVWF and plasma VWF multimers was determined by maleimide-PEO(2)-Biotin labeling and thiol-chromatography. Finally, covalent re-multimerization of ULVWF was examined in a cell- and enzyme-free system.

RESULTS

We found that purified plasma VWF multimers adhere to and elongate ULVWF strings under flow conditions. The formation and propagation of ULVWF strings were dose-dependently reduced by blocking thiols on VWF with NEM, indicating that ULVWF strings are formed by the covalent association of perfused VWF to ULVWF anchored to endothelial cells. The association is made possible by the presence of free thiols in VWF multimers and by the ability of (UL) VWF to covalently re-multimerize.

CONCLUSION

The data provide a mechanism by which the thrombogenic ULVWF strings are formed and elongated on endothelial cells. This mechanism suggests that the thiol-disulfide state of ULVWF regulates the adhesion properties of strings on endothelial cells.

Identification of ALOX5 as a gene regulating adiposity and pancreatic function

AIMS/HYPOTHESIS

We previously used an integrative genetics approach to demonstrate that 5-lipoxygenase (5-LO) deficiency in mice (Alox5 (-/-)) protects against atherosclerosis despite increasing lipid levels and fat mass. In the present study, we sought to further examine the role of 5-LO in adiposity and pancreatic function.

METHODS

Alox5 (-/-) and wild-type (WT) mice were characterised with respect to adiposity and glucose/insulin metabolism using in vivo and in vitro approaches. The role of ALOX5 in pancreatic function in human islets was assessed through short interfering RNA (siRNA) knockdown experiments.

RESULTS

Beginning at 12 weeks of age, Alox5 (-/-) mice had significantly increased fat mass, plasma leptin levels and fasting glucose levels, but lower fasting insulin levels (p<0.05). Although Alox5 (-/-) mice did not exhibit insulin resistance, they had impaired insulin secretion in response to a bolus glucose injection. Histological analyses revealed that Alox5 (-/-) mice had increased islet area, beta cell nuclear size, and numbers of beta cells/mm(2) islet (p<0.05), indicative of both hyperplasia and hypertrophy. Basal and stimulated insulin secretion in isolated Alox5 (-/-) islets were significantly lower than in WT islets (p<0.05) and accompanied by a three- to fivefold decrease in the expression of the genes encoding insulin and pancreatic duodenal homeobox 1 (Pdx1). Direct perturbation of ALOX5 in isolated human islets with siRNA decreased insulin and PDX1 gene expression by 50% and insulin secretion by threefold (p<0.05).

CONCLUSIONS/INTERPRETATION

These results provide strong evidence for pleiotropic metabolic effects of 5-LO on adiposity and pancreatic function and may have important implications for therapeutic strategies targeting this pathway for the treatment of cardiovascular disease.

CYP1A/regucalcin gene expression and edema formation in zebrafish embryos exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

In this study, zebrafish eggs were exposed to a relatively low concentration (50 pg/mL) of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) for 72 h and then transferred to vehicle/TCDD-free water for the remainder of the experiments. Mortality, heart rates, edema severity, CYP1A, and regucalcin gene expressions were investigated to study TCDD-induced toxicity in zebrafish during the early life stage. Results indicated that the 50 pg/mL TCDD caused severe and visible developmental toxicity. Further research of the long term and low concentration of TCDD exposure is required.

Differential binding patterns of monoclonal antibody 2C4 to the ErbB3-p185her2/neu and the EGFR-p185her2/neu complexes

2C4 (Pertuzumab, Omnitarg) is a monoclonal antibody targeting p185(her2/neu), which is overexpressed in 30% of invasive breast cancer. 2C4 is currently in phase II clinical trials for several types of cancers. This antibody has been reported to disrupt the association between p185(her2/neu) and ErbB3. In our studies of epidermal growth factor receptor (EGFR)-p185(her2/neu) heterodimerization, we noted that 2C4 formed associations with the EGFR-p185(her2/neu) receptor complex. Our data argue against 2C4 as a universal heterodimerization blocker for p185(her2/neu), but indicate that cocktails of monoclonal antibodies binding distinct interaction surfaces of p185(her2/neu) will emerge as the most potent targeted therapy.

Effect of ceramic conversion treatments on the surface damage and nickel ion release of NiTi alloys under fretting corrosion conditions

Recent researches have demonstrated that surface modification can improve the fretting wear resistance of NiTi alloys in air or enhance their aqueous corrosion resistance without fretting. However, little is known about the behaviour of surface engineered NiTi under fretting corrosion conditions. This is important for such body implants as orthodontic arch wires and orthopedic bone fixation devices because they need to withstand the combined attack of corrosion from body fluid and mechanical fretting. In this study, a NiTi alloy was ceramic conversion (CC) treated at 400 and 650 degrees C. The effect of the surface treatment on the fretting corrosion behaviour of NiTi alloy was investigated using fretting corrosion tests in the Ringer's solution. The experimental results have shown that the CC treatment can convert the surface of NiTi into a TiO2 layer, which can effectively improve the fretting corrosion resistance of NiTi alloy and significantly reduce Ni ion release into the Ringer's solution. Detailed SEM observations revealed that the untreated samples were severely damaged by adhesion and delamination; the high temperature (HT) (650 degrees C/1 h) treated samples were damaged mainly by spallation and adhesion; and the low temperature (LT) (400 degrees C/50 h) treated samples were characterised by mild abrasion. Mild oxidation and corrosion were also observed for all three types of samples tested under fretting corrosion conditions.