Impaired amyloid β-degrading enzymes in brain of streptozotocin-induced diabetic rats

Enzymes that degrade the amyloid β-peptide (Aβ) are important regulators of cerebral Aβ levels. High level of Aβ was found in the brain of diabetic patients and diabetic animals. Aim of the study was to investigate whether activities of Aβ-degrading enzymes neprilysin (NEP), endothelin-converting enzyme 1 (ECE-1) and insulin-degrading enzyme (IDE) were impaired in the brain of diabetic rats. Diabetes was induced in rats by ip administration of 65 mg/kg streptozotocin. The temporal cortex and hippocampus were obtained for activity and mRNA level assays of the three enzymes on the 35th day after induction. ECE-1 activity was significantly decreased both in the hippocampus and cortex of diabetic rats, while for IDE significantly lower activity occurred only in the cortex. NEP activity was slightly decreased in both brain regions. The hippocampus of diabetic rats showed significant decrease in mRNA levels of NEP and ECE-1 and moderate increase in IDE mRNA level. The cortex of diabetic rats showed slight decrease in mRNA levels of the three enzymes. The results indicated that the three Aβ-degrading enzymes were damaged to different extents in the brain of diabetic rats, and impairment of ECE-1 and IDE partly contributed to the elevated Aβ(1-40) levels in brain of diabetic rats.

Abstract P6-04-13: Gene and microRNA Signatures of the Mesenchymal Epithelial Transition in Pre-Clinical Models of Inflammatory Breast Cancer

Inflammatory breast cancer (IBC) is the most aggressive form of locally advanced breast cancer The pathological hallmark of IBC is lymphovasculogenesis resulting in the invasion of tightly adhered cells, defined as tumor emboli, into lymphovascular spaces of the dermis. IBC tumor emboli have been reported to over-express the glycoprotein E-cadherin, which is at odds with the current hypothesis that tumors with a metastatic phenotype lose E-cadherin, and gain expression of specific transcription factors and microRNAs (miRs) that mediate the process of epithelial mesenchymal transition (EMT). Immunohistochemical staining confirms the presence of E-cadherin on tumor emboli in IBC patient tissues as well as in Mary-X tumor xenografts, which is the only model to recapitulate tumor emboli in vivo. Using unbiased global transcriptional profiling, microRNA microarrays, real time PCR, Western blot validation, immunohistochemistry, immunofluorescence and confocal microscopy, we found that IBC cell lines, and Mary-X tumor emboli from xenografts had significantly elevated expression of genes and their corresponding proteins that collectively mediate tight homotypic cell:cell aggregation, including CDH1 which encodes for E-cadherin, DSC2, which encodes for Desmocollin 2 and JUP/CTNNG1, which encodes for junctional plakoglobin/gamma catenin. Regardless of molecular subtype, IBC cell lines and Mary-X tumor spheroids lacked detectable mRNA or protein for zinc finger E-box binding homeobox 1 gene, ZEB1, with very low levels of ZEB2 gene expression. The expression of CDH1, loss of ZEB1 and low gene expression of ZEB2 by IBC cell lines and Mary-X tumor spheroids was associated with increased expression of specific families of microRNAs including the miR 200 family known to be transcriptional regulators of E-cadherin. In contrast to lack of ZEB1 expression, IBC cell lines expressed either one or all of the SNAI1, SNAI2 and TWIST1 genes, which encode for transcription factors that have been associated with the process of EMT. IBC cell lines that contained ZEB1 cDNA lacked expression of CDH1 and did not produce E-cadherin protein, however the IBC/ZEB1 clones exhibited little difference in their ability to invade across an artificial Matrigel membrane compared to either vector control cells or the parental IBC cells. Taken together, the present observations suggest that pre-clinical models of IBC have distinct gene and microRNA signatures characterized by expression of genes and miRs that collectively support the persistence of compact tightly aggregated tumor cells within IBC tumor emboli, while maintaining an invasive and metastatic phenotype, suggesting that IBC tumor emboli display characteristics of the process of mesenchymal-epithelial transition (MET). Supported in part by the American Airlines-Komen For the Cure Foundation Promise Grant KGO81287 (FMR, MC) and The State of Texas Fund for Rare and Aggressive Breast Cancer (FMR, SK).

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-13.

Abstract PD04-09: Multiple Biomarker Expression in Circulating Tumor Cells from Metastatic Breast Cancer Patients

Background: Numeration of circulating tumor cells, CTCs, from metastatic breast cancer (MBC) patients (pts) is predictive of outcome. Biomarker characterization of CTCs may be a useful adjunctive guide for personalized targeted and systemic treatment (Rx) selection.

Method: A multimarker assay was used to simultaneously quantify expression of HER2, ER and ERCC1. A fast laser scanning instrument was used for sensitive location of CTCs on large glass substrates. CTCs are identified using automated digital microscopy by morphology, the presence of cytokeratin and a nucleus, and the absence of CD45. At the COHCC pts with newly diagnosed/progressing MBC were accrued. Blood samples (10 ml) were procured prior to initiating systemic Rx and at subsequent 3 month intervals and sent to PARC for analysis. Cell lines with expression of each marker were used for normalization of the cell intensities. Sample scores were derived from the percentage of CTCs expressing the marker and the average expression level.

Results: The multiple-marker assay was done on CTCs at repeat time points and results were compared to findings from the original primary BCs (P) and biopsied metastases (M) in 30 and 20 MBC pts respectively. While P and M tissue scores were concordant for HER2, the CTC score was discordant in 58% of the samples; HER2 expression changed during Rx in 19% of pts. While the status for ERCC1 was discordant between P and M tissue in 13% of the pts, CTCs scores were discordant with P and M tumors in 63% and 67% of the patients respectively, and CTC expression status changed during Rx in 15% and 7% of pts respectively. While the status for ER was discordant between P and M tissue in 15% of the pts, CTC scores were discordant from the P and M tumors in 42% and 71% of pts respectively, and CTC ER status changed in 7% and 17% respectively of pts during Rx.

Conclusions: Significant discordances in expression level of ER, HER2 andERCC 1 was observed between CTCs, and both primary and metastatic BC tissue. Changes in CTC expression patterns were also observed during the course of Rx for all three markers. Correlation of CTC biomarker expression patterns and changes with response to Rx therapy is ongoing to validate medical significance. Multimarker testing may ultimately lead to improvements in personalized Rx for pts with MBC.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD04-09.

Abstract P4-01-05: Lapatinib Resistance Confers Cross-Resistance to Microtubule Inhibitors in ErbB2-Overexpressing Breast Cancer Cells

ErbB2 gene amplification occurs in approximately 20% of all breast cancers and is associated with an aggressive subtype with poor clinical prognosis. Acquired resistance to erbB2-targeted therapies is a common occurance even in patients who show an initial clinical response to trastuzumab or lapatinib-based regimens. Optimal treatment for relapsed disease following erbB2 targeted therapies has not been defined. Therefore, we sought to evaluate whether cytotoxic agents have cross-resistance to lapatinib in cell lines that have acquired resistance to lapatinib. Here we established a model of acquired lapatinib resistance derived from erbB2 overexpressing breast cancer cell lines, BT474 and SKBR3. Lapatinib resistant cell lines, BTLapR and SKLapR, were generated by growth in the continuous presence of 2.6 uM lapatinib (peak plasma concentration in human subjects) resulting in IC50 of 4.72 uM (BTLapR) and 0.083 uM (BT474) (P<0.0001). IC50 of SKLapR and SKBR3 were 17.72 uM and 0.1637 uM (P<0.0001), respectively. Next, resulting cells were treated with different classes of chemotherapeutics (2 taxanes, 2 vinca-alkaloids, 1 epothilone, 1 anthracycline, 1 antimetabolite, 2 platinums, and 1 alkylating agent) in order to address cross-resistance to lapatinib. BT474 and BTLapR as well as SKBR3 and SKLapR were exposed to each chemotherapeutic agent and cell viability was evaluated at 72h using a cell proliferation assay (AlamarBlue®). We found that BTLapR was significantly cross-resistant to 5 microtubule inhibitors (paclitaxel, docetaxel, vinorelbine, vinblastine, and ixabepilone), but SKLapR was not (shown in table below).

IC 50 of Significant Drugs on Lapatinib Resistant BT474 cells

Previous studies have shown that resistance to lapatinib can switch cell survival signaling from the erbB2 to ER pathway, and that ER signaling can stimulate beta III tubulin expression. We therefore hypothesize the differential responses to microtubule inhibitors in BTLapR and SKLapR might be explained by the fact that BT474 has both estrogen (ER) and progesterone receptor (PR), but SKBR3 express neither. Moreover, beta-III tubulin is known to be a key resistance mechanism of microtubule inhibition. Western blot analysis of baseline protein expression in both acquired lapatinib-resistant and parental cells indicates that ER signaling is involved in stimulating beta III tubulin and is linked to the development of resistance to microtubule inhibitors. These findings point to a potential mechanism to address cross resistance between lapatinib and microtubule-interacting agents, which could have potential clinical implications when considering salvage therapies following lapatinib treatment.

In vivo evaluation of safety of nanoporous silicon carriers following single and multiple dose intravenous administrations in mice

Porous silicon (pSi) is being extensively studied as an emerging material for use in biomedical applications, including drug delivery, based on the biodegradability and versatile chemical and biophysical properties. We have recently introduced multistage nanoporous silicon microparticles (S1MP) designed as a cargo for nanocarrier drug delivery to enable the loaded therapeutics and diagnostics to sequentially overcome the biological barriers in order to reach their target. In this first report on biocompatibility of intravenously administered pSi structures, we examined the tolerability of negatively (-32.5±3.1mV) and positively (8.7±2.5mV) charged S1MP in acute single dose (10(7), 10(8), 5×10(8) S1MP/animal) and subchronic multiple dose (10(8) S1MP/animal/week for 4 weeks) administration schedules. Our data demonstrate that S1MP did not change plasma levels of renal (BUN and creatinine) and hepatic (LDH) biomarkers as well as 23 plasma cytokines. LDH plasma levels of 145.2±23.6, 115.4±29.1 vs. 127.0±10.4; and 155.8±38.4, 135.5±52.3 vs. 178.4±74.6 were detected in mice treated with 10(8) negatively charged S1MP, 10(8) positively charged S1MP vs. saline control in single and multiple dose schedules, respectively. The S1MPs did not alter LDH levels in liver and spleen, nor lead to infiltration of leukocytes into the liver, spleen, kidney, lung, brain, heart, and thyroid. Collectively, these data provide evidence of a safe intravenous administration of S1MPs as a drug delivery carrier.

Autophagy is increased in prostate cancer cells overexpressing acid ceramidase and enhances resistance to C6 ceramide

Acid ceramidase (AC) overexpression has been observed in prostate cancer cell lines and primary tumors, and contributes to resistance to chemotherapy and radiation. The consequence of AC overexpression is the ability to convert ceramide, which is often produced as a proapoptotic response to stress, to sphingosine, which can then be converted to the prosurvival molecule sphingosine-1-phosphate. In addition to their ability to metabolize ceramide produced in response to stress, we show here that prostate cancer cell lines overexpressing AC also have increased lysosomal density and increased levels of autophagy. Furthermore, pretreatment with 3-methyladenine restores sensitivity of these cells to treatment with C(6) ceramide. We also observed increased expression of the lysosomal stabilizing protein KIF5B and increased sensitivity to the lysosomotropic agent LCL385. Thus, we conclude that AC overexpression increases autophagy in prostate cancer cells, and that increased autophagy enhances resistance to ceramide.

Identification of an intracellular microdomain of the P2X7 receptor that is crucial in basolateral membrane targeting in epithelial cells

We investigated membrane targeting of the P2X(7) receptor (P2X(7)R) in polarized epithelial cells using immunofluorescent confocal imaging. The wild-type receptor was targeted to the basolateral membrane, independently of adaptor protein μ1B. Deletion of the majority of the intracellular C-terminus, or the last 26 residues (P570-Y595), conferred targeting of the protein to the apical membrane. Alanine substitution in the microdomain P582-Q587 caused similar apical membrane targeting without major effect on the receptor function and surface expression. Our results show basolateral membrane targeting of the P2X(7)R in epithelial cells and that the intracellular C-terminal microdomain P582-Q587 is crucial in this process.

Transplantation of immortalized human fetal hepatocytes prevents acute liver failure in 90% hepatectomized mice

AIM

The aim of this study was to investigate whether human fetal hepatocytes are amenable to simian virus 40 large T-antigen (SV40Tag) mediated immortalization and whether the immortalized cells rescue mice with acute liver failure induced by 90% hepatectomy.

METHODS

We constructed a retroviral vector expressing a thermolabile mutant SV40Tag for transfer into primary human fetal hepatocytes. We quantitatively detected the synthetic ability for albumin and urea by the immortalized cells, which were subcutaneously inoculated into mice with severe combined immunodeficiency (SCID) to evaluate tumorigenzcity. The immortalized cells were also transplanted into the spleens of mice with acute liver failure.

RESULTS

One clone resulting after selection, referred to as HepCL, was highly differentiated, growing steadily in a chemically defined serum-free medium. HepCL cells were positive for albumin, cytokeratin 18, and cytokeratin 19 immunocytochemical staining. The average synthetic efficacies of HepCL cells for albumin and urea were comparable to that of unmodified primary human fetal hepatocytes. The population doubling time of HepCL cells in the logarithmic growth phase was approximately 17 hours. HepCL cells showed no oncogenicity in immunodeficient mice at 16 months. Mice receiving HepCL cells (G1) and primary human fetal hepatocytes (G2) showed significantly lower blood ammonia levels after 90% hepatectomy. Pairwise comparisons between the 4 groups showed that xenotransplantation of HepCL (G1) or primary fetal hepatocytes (G2) significantly improved survivals of recipient mice.

CONCLUSIONS

HepCL may be useful as a source of hepatic function for cell-based therapeutics in acute liver failure.

Intranasal brain-derived neurotrophic factor protects brain from ischemic insult via modulating local inflammation in rats

Inflammation plays a vital role in the pathogenesis of ischemic stroke. Brain-derived neurotrophic factor (BDNF) may protect brain tissues from ischemic injury. In this study, we investigated whether intranasal BDNF exerted neuroprotection against ischemic insult by modulating the local inflammation in rats with ischemic stroke. Rats were subjected to temporary occlusion of the right middle cerebral artery (120 min) and intranasal BDNF or vehicle was adminstrated 2 h after reperfusion. Infarct volume and neuron injury were measured using triphenyltetrazolium chloride, Nissl staining and TUNEL assay, respectively. Microglia were detected by immunohistofluorescence. Tumor necrosis factor-α, interleukin10 and mRNAs were evaluated by enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction. DNA-binding activity of nuclear factor-kappa B was measured by electrophoretic mobility shift assay. BDNF level in brain tissues was markedly raised following intranasal administration. There were more Nissl positive and less TUNEL positive neurons in BDNF group than in control group while intranasal BDNF did not reduce the infarct volume significantly (n=6, 0.27±0.04 vs. 0.24±0.05, P>0.05). BDNF increased the number of activated microglia (OX-42 positive) and phagocytotic microglia (ED1 positive). BDNF suppressed tumor necrosis factor-α and mRNA expression while increasing the interleukin10 and mRNA expression. BDNF also increased DNA-binding activity of nuclear factor-kappa B (n=6, 49.78±1.23 vs. 52.89±1.64, P<0.05). Our data suggest intranasal BDNF might protect the brain against ischemic insult by modulating local inflammation via regulation of the levels of cellular, cytokine and transcription factor in the experimental stroke.

Identification of the bacterial biodiversity in koumiss by denaturing gradient gel electrophoresis and species-specific polymerase chain reaction

Bacterial biodiversity in traditional koumiss fermented milk was studied by denaturing gradient gel electrophoresis (DGGE). Target DNA bands were identified according to the reference species ladder, constructed in this study. Comigrating bands present in the DGGE profiles were resolved by species-specific PCR. The results revealed a novel bacterial profile and extensive bacterial biodiversity in koumiss. The dominant lactic acid bacteria included Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus fermentum, and Lactobacillus kefiranofaciens. Frequently encountered bacterial species were Enterococcus faecalis, Lactococcus lactis, Lactobacillus paracasei, Lactobacillus kitasatonis, and Lactobacillus kefiri. Leuconostoc mesenteroides, Streptococcus thermophilus, Lactobacillus buchneri, and Lactobacillus jensenii were occasionally found in this product. In addition, L. buchneri, L. jensenii, and L. kitasatonis, which were never previously isolated by culture-dependent methods, were identified for the first time in the Xinjiang koumiss. Furthermore, conventional cultivation was performed by plating samples on M17, de Man-Rogosa-Sharpe, Halligan-Pearce, and Kenner fecal media. The results revealed that lactobacilli were the dominant species in the koumiss ecosystem, which was consistent with the results obtained by the DGGE analysis. This is the first systematic study of the microbial composition in koumiss, and our findings will be helpful in selecting appropriate strains for the manufacture of this product at the industrial level.