Abstract P6-12-11: Celecoxib inhibits the growth of IBC tumors by suppressing the regulation of cancer stem-like cells by nodal

Background: Inflammatory breast cancer (IBC) is an aggressive type of breast cancer with no known molecular targets for treatment. Although erythema is commonly associated with IBC, the molecular mechanism of inflammation in the pathogenesis of IBC remains unknown. We have previously shown that EGFR is an emerging target in IBC (Zhang D. et al Clin Can Res 2009). As crosstalk between EGFR and COX-2 plays an important role in the inflammatory response in several cancers, including breast cancer, we hypothesized that COX-2 promotes the tumorigenesis and metastasis of IBC cells.

Methods: Using clinically derived IBC and non-IBC tumor samples, a Spearman's Rank correlation coefficient analysis was performed to analyze the expression levels of COX-2 and EGFR in IBC and non-IBC. The levels of COX-2 metabolites, prostaglandins (PGs) PGE2 and PGF2α, were measured in IBC and non-IBC cell lines by HPLC/MS method. Cell migration and invasion assays were performed using SUM149 and KPL-4 IBC cell lines treated with PGs or the COX-2 inhibitor, celecoxib. We evaluated the epithelial to mesenchymal transition (EMT)-like phenotype in 3D culture of SUM149 cells treated with celecoxib, and the stem-like population by mammosphere formation, and CD44+/CD24− and aldefluor+ population by FACS. We treated preclinical IBC xenograft mice with celecoxib and measured tumor growth, PGs levels, and the expression of EMT protein markers. Nodal, a stem cell regulator and potential biomarker for breast cancer progression, was evaluated in IBC cells following treatment with celecoxib and recombinant Nodal or transfection with Nodal cDNA.

Results: EGFR and COX-2 expression levels positively correlated within IBC, but not non-IBC tumors. Elevated levels of PGE2 and PGF2α were identified in multiple IBC cell lines suggesting that COX activity is elevated within IBC compared to non-IBC cells. PGs altered EMT protein markers and promoted cell migration and invasion, while Celecoxib inhibited EMT and migration and invasion in SUM149 and KPL-4 cells. Celecoxib treatment inhibited tumor growth in mice, and downregulated the expression of EMT protein markers, including Nodal. Celecoxib decreased the stem-like CD44+/CD24−, and aldefluor+ population and the formation of mammospheres. Exogenous Nodal mitigated the effects of celecoxib on cell migration and invasion and the stem-like population in SUM149 cells.

Conclusion: We conclude that activation of the COX-2 inflammatory signaling pathway is critical in the development and progression of IBC. This study provides a novel insight into how inflammation may regulate cancer stem cells via Nodal, and will guide future research into the development of stem cell targeted therapies for IBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-12-11.

Abstract P5-03-09: Receptor Activator of Nuclear Factor Kappa B (RANK) as a potential therapeutic target in triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) has a poorer prognosis in comparison to other breast cancer subtypes because of its high metastatic rate. There is evidence that cancer stem cells (CSCs), known to have an epithelial-to-mesenchymal (EMT) phenotype, may contribute to the metastasis of breast cancer. Denosumab (an anti-RANK ligand antibody) is currently being explored as a treatment for breast cancer in phase II and III clinical trials. RANK is thought to regulate mammary stem cells. Therefore, we hypothesized that RANK promotes tumorigenicity and metastasis of TNBC via the regulation of EMT and enrichment of CSCs. We sought to determine the effects of RANK expression on the tumorigenic and metastatic activities of TNBC cells and whether RANK is a potential therapeutic target in TNBC.

Methods: Primary breast tumor specimens from the MD Anderson Cancer Center Tumor Bank were stratified by ER/HER2 status. We analyzed RANK mRNA expression levels, obtained by Affymetrix gene chip array, in ER+/HER2-negative breast tumors (n = 22) and ER−/HER2-negative breast tumors including TNBC tumors (n = 18). To study the effects of RANK suppression in TNBC cells, we generated two stable RANK shRNA MDA-MB-231 TNBC cell lines and a negative shRNA cell line as a control and examined whether knockdown of RANK expression correlated with a decrease in mesenchymal markers, vimentin and snail, and stem cell marker, ALDH1, invasion, migration, and tumorigenicity in TNBC cells.

Results: An analysis of RANK mRNA expression levels among human primary breast cancer specimens revealed increased RANK expression in ER−/HER2-negative primary breast tumors including TNBC tumors, compared with ER+/HER2-negative primary breast tumors (p = 0.034). Knocking down RANK in MDA-MB-231 cells significantly inhibited migration (p = 0.0005) and invasion (p = 0.0006) and reduced the stem cell subpopulation, as shown by a decrease in mammospheres (p = 0.0188) and ALDH1 activity. Further, in a three-dimensional (3D) cell culture model, we observed significant inhibition of projections in MDA-MB-231 cells with knockdown of RANK (p < 0.05), which correlated with downregulation of the mesenchymal markers vimentin and snail shown by qRT PCR analysis.

Conclusion: Our data demonstrate that RANK may promote the tumorigenesis of TNBC by enriching cancer stem cells. In future studies, we will investigate the effect of RANK inhibition on metastasis in vivo using a TNBC xenograft model. Our long-term goal is to develop RANK-targeted therapy for TNBC.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-03-09.

Rac2 GTPase activation by angiotensin II is modulated by Ca2+/calcineurin and mitogen-activated protein kinases in human neutrophils

Angiotensin II (Ang II) highly stimulates superoxide anion production by neutrophils. The G-protein Rac2 modulates the activity of NADPH oxidase in response to various stimuli. Here, we describe that Ang II induced both Rac2 translocation from the cytosol to the plasma membrane and Rac2 GTP-binding activity. Furthermore, Clostridium difficile toxin A, an inhibitor of the Rho-GTPases family Rho, Rac and Cdc42, prevented Ang II-elicited O2-/ROS production, phosphorylation of the mitogen-activated protein kinases (MAPKs) p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase 1/2, and Rac2 activation. Rac2 GTPase inhibition by C. difficile toxin A was accompanied by a robust reduction of the cytosolic Ca(2)(+) elevation induced by Ang II in human neutrophils. Furthermore, SB203580 and PD098059 act as inhibitors of p38MAPK and ERK1/2 respectively, wortmannin, an inhibitor of phosphatidylinositol-3-kinase, and cyclosporin A, a calcineurin inhibitor, hindered both translocation of Rac2 from the cytosol to the plasma membrane and enhancement of Rac2 GTP-binding elicited by Ang II. These results provide evidence that the activation of Rac2 by Ang II is exerted through multiple signalling pathways, involving Ca(2)(+)/calcineurin and protein kinases, the elucidation of which should be insightful in the design of new therapies aimed at reversing the inflammation of vessel walls found in a number of cardiovascular diseases.

Membrane vesicles released by Actinobacillus pleuropneumoniae contain proteases and Apx toxins

Actinobacillus pleuropneumoniae serotype 1 releases vesicles containing proteases and Apx toxins into the culture medium. Vesicles were concentrated by ultracentrifugation and analyzed by electron microscopy and electrophoresis; their size ranged from 20 to 200 nm. A polyclonal antiserum raised against a purified high molecular mass secreted protease of serotype 1 recognized this protease on the surface of the vesicles by immunogold electron microscopy. Higher molecular mass polypeptides from vesicle extracts were recognized by the antiserum by Western immunoblot, indicating that the protease could form oligomers. However, these oligomers were not active against gelatin until secreted. Additionally, Apx toxins were also present in vesicles, and were recognized by Western immunoblot by an anti-serotype 1 toxins polyclonal serum. A. pleuropneumoniae antigens in vesicles were recognized by convalescent-phase pig sera from animals infected with serotype 1 or 5. The release of vesicles containing virulence factors could be a tissue damage mechanism in swine pleuropneumonia.

Purification and characterization of a protease from Actinobacillus pleuropneumoniae serotype 1, an antigen common to all the serotypes

A high molecular-mass proteolytic enzyme of Actinobacillus pleuropneumoniae serotype 1, was purified from culture supernatants (CSN) by using DEAE-cellulose and sepharose-4B-gelatin chromatography. In 10% SDS-polyacrylamide gels copolymerized with porcine gelatin, the protease showed a single band of activity of > 200 kDa. However, minor molecular-mass proteolytic bands were observed when the protease was electrophoresed in the presence of either 5% beta-mercaptoethanol, 50 mM dithiothreitol, or 0.25 M urea. Furthermore, when the > 200-kDa purified protein was passed through a sucrose gradient, several bands with proteolytic activity were found: 62, 90, 190, and 540 kDa. The proteolytic activity was increased in the presence of calcium or zinc and was not affected after being heated at 90 degrees C for 5 min. Proteolytic activities were also observed in CSN from all A. pleuropneumoniae serotypes and biotypes. The purified protease hydrolyzed porcine IgA and IgG in vitro. In addition, by immunoblot the protease was recognized by serum of naturally infected pigs with serotypes 1 and 5, and by serum of pigs experimentally infected with serotypes 1, 2, 8, or 9. Serum of a pig vaccinated with CSN of a serotype 3 strain also recognized the protease, but not sera of pigs vaccinated with a bacterin (serotype 1). Proteins from CSN of all the serotypes, which were precipitated with 70% (NH4)2SO4, were recognized by a polyclonal antibody raised against the purified protease. Taken together these results indicate that an antigenic protease is produced in vivo by all the serotypes of A. pleuropneumoniae. The results indicate that proteases could have a role in the disease and in the immune response of pigs infected with A. pleuropneumoniae.

Transposon tagging of the Defective embryo and meristems gene of tomato

The shoot and root apical meristems (SAMs and RAMs, respectively) of higher plants are mechanistically and structurally similar. This has led previously to the suggestion that the SAM and RAM represent modifications of a fundamentally homologous plan of organization. Despite recent interest in plant development, especially in the areas of meristem regulation, genes specifically required for the function of both the SAM and RAM have not yet been identified. Here, we report on a novel gene, Defective embryo and meristems (Dem), of tomato. This gene is required for the correct organization of shoot apical tissues of developing embryos, SAM development, and correct cell division patterns and meristem maintenance in roots. Dem was cloned using transposon tagging and shown to encode a novel protein of 72 kD with significant homology to YNV2, a protein of unknown function of Saccharomyces cerevisiae. Dem is expressed in root and shoot meristems and organ primordia but not in callus. The expression pattern of Dem mRNA in combination with the dem mutant phenotype suggests that Dem plays an important role within apical meristems.

Comparison of the cervical cytology test using the PAPNET method and conventional microscopy

From August 1994 to June 1995, laboratories in 28 Mexican states and the Federal District submitted a total of 10098 diagnosed Pap test slides to Mexico's National Institute of Epidemiologic Diagnosis and Reference (INDRE) for reexamination by conventional methods and also by the automated PAPNET system in Suffern, New York, U.S.A. The aim was to determine the degree of agreement obtained by these various methods. Most of the slides examined (at least 78%) yielded negative results or merely indicated an inflammatory process; 8% to 14% indicated mild or moderate cervical dysplasia; and 2% to 3% indicated conditions ranging from severe dysplasia to invasive cervical cancer. Comparison of the state laboratory and INDRE diagnoses yielded a Kappa correlation coefficient of 0.62, near the lower limit of agreement, the agreement being poorest in cases where it was necessary to distinguish between degrees of abnormality. Although state laboratory underestimation appeared lowest with respect to cases of atypia and of mild, moderate, and severe dysplasia (between 12% and 20%), these percentages are alarming because it is at these stages that the patient may be treated to prevent evolution to carcinoma. While the Kappa correlation coefficient was better (0.80) when the INDRE and PAPNET diagnoses were compared, PAPNET showed only limited ability to distinguish between various pathologic alterations, and the percentages of underestimates (false negatives) obtained with PAPNET were also high. Overall, the results indicate a need to improve the quality of cervical cytology diagnoses at state public health laboratories in Mexico through stepped-up training and supervision. They also indicate that the use of PAPNET involves greater difficulty than does manual microscopic examination of cervical smears, and that a way still needs to be found to detect and review the false negative results generated by PAPNET before approving use of this technology.

Blood levels in macular cystoid spaces and their relationship to retinal vein obstruction

BACKGROUND

Blood levels in macular cystoid spaces are commonly seen in patients with branch or central retinal vein obstruction, but have not been previously reported.

METHODS

To determine blood levels in cystoid spaces, a retrospective study was conducted of 102 eyes with branch retinal vein obstruction, 54 eyes with central retinal vein obstruction, 207 eyes with clinically significant diabetic macular edema, and 109 eyes with aphakic or pseudophakic cystoid macular edema seen over a 5-year period.

RESULTS

Definite blood levels in cystoid spaces were found in 26 eyes (25%) with branch vein obstruction and in 4 eyes (8%) with central vein obstruction. In contrast, this clinical change was detected in only 1 of 207 eyes (1%) with diabetic cystoid macular edema, and in only 2 of 109 eyes (2%) with aphakic or pseudophakic cystoid macular edema (P < 0.001). When blood levels in cystoid spaces were detected in patients with branch vein obstruction, the site of obstruction tended to be superotemporal (P < 0.05).

CONCLUSION

Blood levels in cystoid spaces are an important sign of retinal vein obstruction, and may help establish the diagnosis in certain cases.