Abstract P1-02-02: Processing of GPNMB by ADAM-10 in Breast Tumors Releases an Extracellular Domain with Angiogenic Properties

Background: Glycoprotein non-metastatic B (GPNMB), also known as Osteoactivin, is a cell surface bound, transmembrane protein that is expressed in 41-74% of breast cancers. We have shown that it promotes migration, invasion and metastasis of breast cancer cells, that it is associated with shorter recurrence-free and overall survival times, and that it is most commonly expressed among breast tumors of the basal/triple-negative subtypes. Patients with basal/triple-negative breast cancer have aggressive disease and are not amenable to currently available targeted therapies. For these reasons GPNMB is an attractive target for therapeutic intervention in breast cancer; indeed, a GPNMB-targeted antibody-drug conjugate (CDX-011) has shown impressive clinical response among patients with GPNMB-positive breast cancer and is being investigated in Phase IIb clinical trials. Despite its promise as a therapeutic target in breast cancer, little is known about the functional role of GPNMB the primary tumor microenvironment.

Materials and Methods: We have employed 66cl4 murine mammary carcinoma cells and human BT549 breast cancer cells to investigate the effects of GPNMB on tumor growth and angiogenesis, respectively in vivo. Control and GPNMB-expressing tumors were analyzed using immunohistochemistry for degree of proliferation apoptosis and angiogenesis. To better characterize functionally important domains of GPNMB we employed immunoblot and ELISA analyses to assess levels of full length, intact GPNMB and shed GPNMB ectodomain in breast cancer cells. Transient siRNA-mediated knockdown studies were used to identify sheddases responsible for GPNMB shedding. Finally, we employed in vitro migration assays to assess function of the shed extracellular domain (ECD) of GPNMB.

Results: In this study we show that GPNMB promotes the outgrowth of mammary tumors in vivo and enhances their microvascular density. In an effort to investigate the functional domains of GPNMB that are responsible for this pro-angiogenic effect, we found that that the extracellular domain (ECD) of GPNMB is constitutively shed in breast cancer cells and show that this ECD is capable of inducing endothelial migration. Finally, we have implicated a disintegrin and metalloprotease-10 (ADAM10) as a novel sheddase responsible for liberation GPNMB ectodomain.

Conclusion: In this study we have described ADAM10-mediated shedding of GPNMB ECD - a protein fragment that induces endothelial cell migration - as a novel mechanism by which GPNMB can promote angiogenesis in breast cancer. Further efforts to characterize the effect of GPNMB on endothelial cell function will be discussed.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-02-02.

Sphingosine-1-phosphate phosphohydrolase-1 regulates ER stress-induced autophagy

The sphingolipid metabolites ceramide and sphingosine-1-phosphate (S1P) have recently been implicated in autophagy. In this study, we report that depletion of sphingosine-1-phosphate phosphohydrolase-1 (SPP1), an endoplasmic reticulum (ER)-resident enzyme that specifically dephosphorylates S1P, induced autophagy. Although the mammalian target of rapamycin and class III phosphoinositide 3-kinase/Beclin-1 pathways were not involved and this autophagy was p53 independent, C/EBP homologous protein, BiP, and phospho-eucaryotic translation initiation factor-2α, and cleavage of procaspases 2 and 4, downstream targets of ER stress, were increased after SPP1 depletion. Autophagy was suppressed by depletion of protein kinase regulated by RNA-like ER kinase (PERK), inositol-requiring transmembrane kinase/endonuclease-1α, or activating transcription factor 6, three sensors of the unfolded protein response (UPR) to ER stress. Autophagy triggered by downregulation of SPP1 did not lead to apoptosis but rather stimulated, in a PERK dependent manner, the survival signal Akt, whose inhibition then sensitized cells to apoptosis. Although depletion of SPP1 increased intracellular levels of S1P and its secretion, activation of cell surface S1P receptors did not induce autophagy. Nevertheless, increases in intracellular pools of S1P, but not dihydro-S1P, induced autophagy and ER stress. Thus, SPP1, by regulating intracellular S1P homeostasis, can control the UPR and ER stress-induced autophagy.

Eimeria maxima recombinant Gam82 gametocyte antigen vaccine protects against coccidiosis and augments humoral and cell-mediated immunity (46.19)

Intestinal infection with Eimeria, the etiologic agent of avian coccidiosis, stimulates protective immunity to subsequent colonization by the homologous parasite, whilst cross-protection against heterologous species is poor. This study was designed to assess a purified recombinant protein from E. maxima gametocytes (Gam82) in stimulating immunity against experimental infection with live parasites. Following Gam82 intramuscular immunization and oral parasite challenge, body weight gain, fecal oocyst output, gut lesions, serum antibody response, cytokine production, and lymphoproliferation were assessed to evaluate vaccination efficacy. Animals vaccinated with Gam82 and challenged with E. maxima showed lower oocyst shedding and reduced intestinal pathology compared with non-vaccinated and parasite-challenged animals. Gam82 vaccination also stimulated the production of antigen-specific serum antibodies, induced greater levels of IL-2 and IL-15 mRNAs, and increased splenic lymphoproliferation compared with non-vaccinated controls. These results demonstrate that the Gam82 recombinant protein protects against coccidiosis and augments humoral and cell-mediated immunity.

A thermodynamically-based model for predicting microbial growth and community composition coupled to system geochemistry: Application to uranium bioreduction

'Bioimmobilization' of redox-sensitive heavy metals and radionuclides is being investigated as a way to remediate contaminated groundwater and sediments. In one approach, growth-limiting substrates are added to the subsurface to stimulate the activity of targeted groups of indigenous microorganisms and create conditions favorable for the microbially-mediated reductive precipitation ('bioreduction') of targeted contaminants. We present a theoretical framework for modeling this process that modifies conventional geochemical reaction path modeling to include thermodynamic descriptions for microbial growth and may be called biogeochemical reaction path modeling. In this approach, the actual microbial community is represented by a synthetic microbial community consisting of a collection of microbial groups; each with a unique growth equation that couples a specific pair of energy yielding redox reactions. The growth equations and their computed standard-state free energy yields are appended to the thermodynamic database used in conventional geochemical reaction path modeling, providing a direct coupling between chemical species participating in both microbial growth and geochemical reactions. To compute the biogeochemical reaction paths, growth substrates are reacted incrementally with the defined geochemical environment and the coupled equations are solved simultaneously to predict reaction paths that display changing microbial biomass, community composition (i.e. the fraction of total biomass in each microbial group), and the aqueous and mineral composition of the system, including aqueous speciation and oxidation state of the targeted contaminants. The approach, with growth equations derived from the literature using well-known bioenergetics principles, was used to predict the results of a laboratory microcosm experiment and an in situ field experiment that investigated the bioreduction of uranium. Predicted effects of ethanol or acetate addition on uranium concentration and speciation, major ion geochemistry, mineralogy, microbial biomass and community composition were in qualitative agreement with experimental observations although the available data precluded rigorous model testing. While originally developed for use in better understanding of bioimmobilization of heavy metals and radionuclides, the modeling approach is potentially useful for exploring the coupling of microbial growth and geochemical reactions in a variety of other basic and applied biotechnology research settings.

Detection and prediction of alternative splicing in Arabidopsis thaliana

Alternative splicing is an important process for increasing the diversity arising from a single gene. Presently, most studies aimed at detecting alternatively spliced genes use Expressed Sequence Tags (ESTs). However, the EST studies based on spliced transcripts analyse sequences by alignment rather than sequence patterns. Second, EST libraries can be of uncertain quality. To address these issues and to improve the quality of detection and prediction for alternative splicing, we propose a method that primarily uses pre-mRNAs. It is achieved by a decision tree algorithm using triplet nucleotides as attributes for each chromosome in Arabidopsis thaliana. In addition, we propose a novel algorithm for accurate prediction.

Coexistence of weak ferromagnetism and ferroelectricity in the high pressure LiNbO3-type phase of FeTiO3

We report the magnetic and electrical characteristics of polycrystalline FeTiO_{3} synthesized at high pressure that is isostructural with acentric LiNbO_{3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below approximately 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

Phase II study of S-1 monotherapy in taxane, cisplatin refractory gastric cancer

4551

Background: S-1 is a fourth-generation oral fluoropyrimidine that was developed to mimic protracted continuous infusion of 5-fluorouracil (5-FU). In previous study, S-1 demonstrated promising activity which is comparable to combination chemotherapy in advanced gastric cancer. This phase II study evaluated the efficacy and safety of S-1 salvage chemotherapy, in patients with taxane and cisplatin refractory gastric cancer. The primary end point was progression free survival and secondary end points were overall survival, safety and clinical benefit. Methods: Patients were eligible if they had histologically documented gastric adenocarcinoma previously treated with taxane (docetaxel or paclitaxel) and cisplatin; age≥18; Eastern Clinical Oncology Group (ECOG) performance status of 2 or less; adequate organ function; no evidence of gastrointestinal obstruction or passage disturbance. S-1 treatment was performed according to BSA as followed; < BSA 1.25, 80 mg/day, 1.25 ≤ BSA < 1.5, 100 mg/day; BSA ≥ 1.5, 120 mg/day. Every dosage was delivered divided two times and administered for 4 weeks followed by 2 weeks of resting period. Treatment continued until progression of disease or life-threatening adverse events were occurred. Results: Fifty-four patients were enrolled in this study and of the patients, forty-eight patients were evaluable. A total 194 chemotherapy cycles were administered and median number of cycles was three. Four (8.3%) patients had a partial response and 18 (37.5%) patients had stable disease. The median progression free survival and overall survival were 3.8 and 10.2 months, respectively. Grade III/IV hematologic toxicities included neutropenia in 6 patients (12.5%) and there was no febrile neutropenia. Most of nonhematologic toxicities were diarrhea, asthenia, and mucositis, and there was no grade 3 or grade 4 except two patients, who developed grade 3 anorexia and diarrhea, respectively. The clinical benefit response was observed in 16 patients (33.3%). Conclusions: This results showed that S-1 monotherapy was active and safe salvage chemotherapy in patients with advanced gastric cancer previously treated with taxane and cisplatin.

No significant financial relationships to disclose.

GSTP1 promoter hypermethylation during breast cancer development

Abstract #5042

Background. Promoter hypermethylation in precursor lesions of the breast cancer may be biomarkers of cancer risk and targets for cancer chemoprevention. GSTP1 is inactivated by promotor hypermethylation in invasive breast cancers. However, little is known about epigenetic silencing of GSTP1 gene by promoter hypermethylation in precursor lesions.&#x2028; Method. To determine the significance of GSTP1 promoter hypermethylation in breast carcinogenesis, methylation status of GSTP1 gene was studied by nested methylation-specific PCR and GSTP1 expression was studied by immunohistochemistry in invasive ductal carcinoma (IDC), ductal carcinoma in situ (DCIS), usual ductal hyperplasia (UDH) and normal breast tissue.&#x2028; Results. GSTP1 promoter hypermethylation was detected in 4/24 (16.7%) of UDH, 18/49 (36.7%) of DCIS, and 14/36 (38.9%) of IDC. No hypermethylation was detected in normal breast tissues. GSTP1 promoter hypermethylation was found to be progressively elevated during breast carcinogenesis (P &lt; 0.01). GSTP1 promoter hypermethylation was associated with loss of GSTP1 expression (P &lt; 0.01 for UDH, P &lt; 0.001 for DCIS and IDC).&#x2028; Conclusion. Our results suggest that GSTP1 promoter hypermethylation is an early event in breast carcinogenesis and appears to functionally silence GSTP1 expression. GSTP1 promoter hypermethylation in the precursor lesions of breast cancer may be used as a target for cancer chemoprevention.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5042.

Induction of cell cycle arrest and apoptosis in breast cancer cells by troglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-γ) ligand

Abstract #5034

Background: Peroxisome proliferator-activated receptor-gamma(PPAR-γ) ligands inhibit cell proliferation and induce apoptosis in cancer cells. And, it is reported that PPAR-γ ligands could serve as negative regulators of breast cancer development and progression, but their mechanism is still unknown. Here we wished to determine whether the PPAR-γ ligand induces cell cycle arrest and apoptosis of MDA-MB-231(ERα-negative) and MCF-7(ERα-positive) breast cancer cell.&#x2028; Methods: The effect of PPAR-γ ligands on the cell viability of breast cancer cells was determined using mitochondrial tetrazolium(MTT) assay. The cell cycle distribution and apoptosis induction were evaluated by using the flow cytometry. The expression of apoptosis-related proteins were measured with Western blot analysis. Statistical analysis was performed using Student's t test, and p&lt;0.05 was considered significant.&#x2028; Results: The treatment of MDA-MB-231 cell with PPAR-γ ligand, troglitazone was shown to induce cell cycle G1 arrest and induction of apoptosis. Moreover, troglitazone treatment, applied in a dose-dependent manner, caused a marked decrease in phosphorylated retinoblastoma(pRb), cyclin D1, D2, D3, cyclin dependent kinase(Cdk) 2, 4, and 6 expression as well as a significant increase in Cdk inhibitor, p21 and p27. Troglitazone showed antiproliferative effect on MCF-7 cell with tamoxifen, respectively and synergically. Troglitazone and tamoxifen could induce G1 arrest and apoptosis of MCF-7 cell, through upregulation of Bax and downregulation of Bcl-2 and cyclin D1.&#x2028; Conclusion: PPAR-γ ligand, troglitazone induces cell cycle arrest and apoptosis of MDA-MB-231 cell and increases the sensitivity of anti-hormonal therapy in MCF-7 cell. These results suggest that troglitazone has anticancer effect on both ERα-negative and positive breast cancer cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5034.