Abstract P6-06-27: Expression of ATP-binding cassette transporter C1 (ABCC1) and activated sphingosine kinase 1 in breast cancer are associated with significantly shorter disease free survival

Background and specific objectives: ATP-binding cassette (ABC) transporters are known to be multidrug resistance proteins that efflux various compounds out of cells including chemotherapeutic agents. A number of clinical trails have been conducted targeting ABCB1: however, none showed beneficial effects. The pleiotropic bioactive lipid mediator sphingosine-1-phosphate (S1P), which is generated by sphingosine kinase 1 (SphK1) inside breast cancer cells and exerts its functions by binding to its specific cell surface G-protein coupled receptors (S1PR1-5) after being exported, is now known as a key regulatory molecule in breast cancer progression. We have previously demonstrated that ABCC1 and ABCG2, but not ABCB1 export S1P out of MCF7 human breast cancer cells. We hypothesized that ABCC1 expression in the presence of S1P produced by activated SphK1 in human breast cancer is associated with poor prognosis.

Methods: We constructed a tissue microarray with 281 breast tumors from patients, and analyzed expressions of ABCB1, ABCC1, and ABCG2, activated SphK1 (pSphK1), and S1P receptor-1 (S1PR1) immunohistochemically. Breast cancer subtypes were determined by immunohistochemistry of ER, PR, and HER2. Protein expressions were correlated to clinicopathological characteristics, clinical follow-up, and pathological complete response to neoadjuvant chemotherapy. For in vitro experiments, MCF7 human breast cancer cells were transfected with ABCB1 or ABCC1 and stimulated with estradiol. Cell proliferation was analyzed by WST-8 assay.

Results: The tissue microarray was comprised of 191 luminal A (68.0%), 17 luminal B (6.0%), 27 HER2 (9.6%), and 46 triple-negative (16.4%) tumors. Activated SphK1 was highly expressed in the patients with lymph node metastasis (40.1% vs 27.3%, P = 0.037) and the pSphK1 high expression group had significantly shorter disease free survival (DFS) (P = 0.05). Eighty percent of the patients expressed S1PR1; however, there were no significant differences in prognosis. On the other hand, ABCC1 expression was associated with significantly shorter DFS (P = 0.027). ABCC1 and ABCG2, but not ABCB1, were significantly higher and more frequently expressed in aggressive subtypes. Patients with tumors expressing both pSphK1 and ABCC1 had significantly shorter DFS (P = 0.002), while patients expressing both ABCB1 and pSphK1 did not. Overexpression of ABCC1 in MCF7 cells not only increased S1P secretion, it significantly increased estradiol-dependent proliferation, compared to MCF7 cells transfected with control vector or ABCB1 (P = 0.010 and P = 0.027, respectively).

Conclusions: We have shown that ABCC1 and ABCG2 are highly expressed in aggressive breast cancer subtypes, and that co-expression of pSphK1 and ABCC1 in the tumors is associated with poor prognosis. Our results suggest that inside-out signaling of S1P via ABCC1 may play a significant role in the course of human breast cancer progression.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-27.

Abstract P2-05-06: Does the lipid mediator sphingosine-1-phosphate have a role in obesity-related cancer progression?

INTRODUCTION: Obesity, which is the number one health risk in US ranked by the CDC, is an established independent prognostic factor for breast cancer patients. While the link between obesity and elevated breast cancer mortality is well known, the underlying mechanisms are poorly understood. The pleiotropic bioactive lipid mediator sphingosine-1-phosphate (S1P) has emerged as a key regulatory molecule in cancer progression and inflammation. S1P is generated by two sphingosine kinases, SphK1 and SphK2, and exerts its functions by binding to specific G protein-coupled receptors (S1PR1-5). We have recently shown that SphK1, but not SphK2, produces S1P that is exported from breast cancer cells, mediated by the ATP-binding cassette transporter, ABCC1. Furthermore, we discovered that another S1P transporter, Spns2, is important for the lymphatic network formation in the LNs. FTY720, which after phosphorylation is a S1PR1 functional antagonist, was recently approved by FDA for multiple sclerosis. FTY720 also has been suggested to have some anti-cancer actions. Our hypothesis is that obesity up-regulates SphK1, which produces more S1P; the elevated levels of S1P in both tumor and its microenvironment stimulate breast cancer progression. FTY720 is expected to disrupt the SphK1/S1P/S1PR1 axis, which is strengthened by obesity, and to reduce cancer metastasis and prolong survival. We tested our hypothesis by utilizing animal models of breast cancer with obesity treated with FTY720.

METHODS: We utilized two different syngeneic breast cancer mouse models: 4T1-luc2 cells in BALB/c mice and E0771 cells in C57Bl/6 mice, both inoculated into mammary fat pads of mice fed with normal or high fat diet. FTY720 was given orally. Western blot, QPCR and LC-ESI-MS/MS assays were used.

RESULTS: We observed that breast tumors in obese animals expressed higher levels of SphK1 and S1P transporters, such as ABCC1 and Spns2, as compared to animals on a normal diet. The levels of S1P in the plasma of obese mice were also elevated, which appears to be a consequence of the higher production of S1P by SphK1 in the tumor and its microenvironment. Importantly, tumor progression in both models was suppressed significantly by administration of FTY720. Interestingly, the cancer progression was suppressed more efficiently in the obese mice than the lean mice. Further, LC-ESI-MS/MS analysis showed that FTY720 suppressed S1P levels not only in the blood, but also in the tumor interstitial fluid.

CONCLUSIONS: These results suggest that the S1P axis is strengthened by obesity, and has a role in cancer progression. Targeting the S1P axis with FTY720 may be useful for treating breast cancer in individuals with obesity. M.N. is a Japan Society for the Promotion of Science Postdoctoral Fellow. This work was supported by NIH grants R37GM043880, R01CA61774 (to S.S.) and R01CA160688 (to K.T.).

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-05-06.

Subcellular localization of fructosyl amino acid oxidases in peroxisomes of Aspergillus terreus and Penicillium janthinellum

Fructosyl amino acid oxidase (FAOD) is the enzyme catalyzing the oxidative deglycation of Amadori compounds, such as fructosyl amino acids, yielding the corresponding amino acids, glucosone, and H(2)O(2). In a previous report, we determined the primary structures of cDNAs coding for FAODs from two fungal strains Aspergillus terreus AP1 and Penicillium janthinellum and we found that both fungal FAODs included the putative peroxisome targeting signal 1 (PTS1) at the carboxyl terminal (Yoshida, N. et al., Eur. J. Biochem., 242, 499-505, 1996). In this study, we determined the intracellular localization of FAODs in these two fungi. Subcellular fractionation experiments and immuno-electronmicroscopic observations, together with the previous findings indicated that the FAODs were localized in peroxisomes of A. terreus AP1 and P. janthinellum. These FAODs were also found to belong to a new member of "peroxisomal sarcosine oxidase family protein" in eucaryotic cells.

Xylan deposition on secondary wall of Fagus crenata fiber

Delignified and/or xylanase-treated secondary walls of Fagus crenata fibers were examined by field emission scanning electron microscopy. Microfibrils with a smooth surface were visible in the innermost surface of the differentiating fiber secondary wall. There was no ultrastructural difference between control and delignified sections, indicating that lignin deposition had not started in the innermost surface of the cell wall. There was no ultrastructural difference between control and xylanase-treated sections. Microfibrils on the outer part of the differentiating secondary wall surface had globular substances in delignified sections. These globular substances disappeared following xylanase treatment, indicating that these globules are xylan. The globular substances were not visible near the inner part of the differentiating secondary wall but gradually increased toward the outer part of the secondary wall, indicating that xylan penetrated into the cell wall and continuously accumulated on the microfibrils. Mature-fiber secondary walls were also examined by field emission scanning electron microscopy. Microfibrils were not apparent in the secondary wall in control specimens. Microfibrils with many globular substances were observed in the delignified specimens. Following xylanase treatment, the microfibrils had a smooth surface without any globules, indicating that the globular substance is xylan. These results suggest that cellulose microfibrils synthesized on the plasma membrane are released into the innermost surface of the secondary wall and coated with a thin layer of xylan. Successive deposition of xylan onto the cell wall increases the microfibril diameter. The large amounts of xylan that accumulated on microfibrils appear globular but are covered with lignin after they are deposited.

Role of the putative membrane-bound endo-1,4-beta-glucanase KORRIGAN in cell elongation and cellulose synthesis in Arabidopsis thaliana

A temperature-sensitive, elongation-deficient mutant of Arabidopsis thaliana was isolated. At the non-permissive temperature of 31 degrees C, the mutation impaired tissue elongation; otherwise, tissue development was normal. Hypocotyl cells that had established cell walls at 21 degrees C under light-dark cycles ceased elongation and swelled when the mutant was shifted to 31 degrees C and darkness, indicating that the affected gene is essential for cell elongation. Analysis of the cell walls of mutant plants grown at 31 degrees C revealed that the cellulose content was reduced to 40% and the pectin content was increased to 162% of the corresponding values for the wild type grown at the same temperature. The increased amounts of pectin in the mutant were bound tightly to cellulose microfibrils. No change in the content of hemicellulose was apparent in the 31 degrees C-adapted mutant. Field emission-scanning electron microscopy suggested that the structure of cellulose bundles was affected by the mutation; X-ray diffraction, however, revealed no change in the crystallite size of cellulose microfibrils. The regeneration of cellulose microfibrils from naked mutant protoplasts was substantially delayed at 31 degrees C. The recessive mutation was mapped to chromosome V, and map-based cloning identified it as a single G-->A transition (resulting in a Gly(429)-->Arg substitution) in KORRIGAN, which encodes a putative membrane-bound endo-1,4-beta-glucanase. These results demonstrate that the product of this gene is required for cellulose synthesis.

Autolysis during in vitro tracheary element differentiation: formation and location of the perforation

Tracheary elements differentiated from isolated Zinnia: mesophyll cells were observed at various times of culture under a scanning electron microscope. Perforation occurred on the primary wall at one of the longitudinal ends in single tracheary elements. In double tracheary elements, which both of two cells derived from a single cell differentiated into, the pore opened on the primary walls both at the junction of the two tracheary elements and at a longitudinal end of one of the two tracheary elements. These results suggest not only that a single tracheary element has its own program to form a perforation at one end without being affected by neighboring cells, but also that isolated cells indeed hold some traces of polarity and cell-cell communication.

Computed tomography (CT) findings of gastric rupture after blunt trauma

A 49-year-old carpenter was hit by timber around his upper abdomen 1 hour after breakfast. Immediate computed tomography was taken, followed by emergency laparotomy showing gastric rupture accompanied with hemorrhage from the superior mesenteric vein. Hemostasis and distal partial gastrectomy followed by Billroth-I anastomosis reconstruction was performed. Here, we report the abdominal computed tomography findings from a patient with gastric rupture after blunt trauma. The present case, which is only the second such case reported in English literature, suggested that computed tomography is useful for assessing associated injuries in gastric rupture patients, for detecting intraperitoneal free air which can be missed by X-rays, and for locating the laceration of the rupture.

Boron nutrition of cultured tobacco BY-2 cells. III. Characterization of the boron-rhamnogalacturonan II complex in cells acclimated to low levels of boron

Cultured cells of tobacco (Nicotiana tabacum L.) BY-2 which could propagate at the same rate as the parent cells (1 mg B liter(-1)) under a lower level of boron (0.01 mg B liter(-1)) were obtained. The selected cells had swollen cell walls. In the parent cells, all the RG-II occurred as a B-RG-II complex, however, two-thirds of the RG-II occurred in a monomeric form in the selected cells.

Production of fungal fructosyl amino acid oxidase useful for diabetic diagnosis in the peroxisome of Candida boidinii

A high-level production of fructosyl amino acid oxidase (FAOD), whose production was toxic in Escherichia coli, was investigated through attempts to utilize the peroxisome of Candida boidinii as the place for protein accumulation. The alcohol oxidase-depleted strain (strain aod1Delta) produced FAOD at a four to five times higher level than the wild type strain in terms of protein amount and enzyme activity, although the transcriptional level was similar. As a result of this study, we could improve FAOD productivity approximately 47-fold from the original transformant, and FAOD accumulated within membrane-bound peroxisomes up to 18% of the total soluble proteins.