Edward H. Cho

Secreted Semaphorins Modulate Synaptic Transmission in the Adult Hippocampus

Modulation of synaptic activity is critical for neural circuit function and behavior. The semaphorins are a large, phylogenetically conserved protein family with important roles in neural development. However, semaphorin function in the adult brain has yet to be determined. Here, we show that the coreceptors for secreted semaphorins, the neuropilins, are found at synapses and localize to molecular layers of the adult mouse hippocampus and accessory olfactory cortex. Moreover, application of the secreted semaphorin Sema3F to acute hippocampal slices modulates both the frequency and amplitude of miniature EPSCs in granule cells of the dentate gyrus and pyramidal neurons of CA1. Finally, we show that mice lacking Sema3F are prone to seizures. These results suggest a novel role for semaphorins as synaptic modulators and illustrate the diverse repertoire of these guidance cues in both the formation and function of neural circuits.

Characterization of circulating tumor cell aggregates identified in patients with epithelial tumors

Circulating tumor cells (CTCs) have been implicated as a population of cells that may seed metastasis and venous thromboembolism (VTE), two major causes of mortality in cancer patients. Thus far, existing CTC detection technologies have been unable to reproducibly detect CTC aggregates in order to address what contribution CTC aggregates may make to metastasis or VTE. We report here an enrichment-free immunofluorescence detection method that can reproducibly detect and enumerate homotypic CTC aggregates in patient samples. We identified CTC aggregates in 43% of 86 patient samples. The fraction of CTC aggregation was investigated in blood draws from 24 breast, 14 non-small cell lung, 18 pancreatic, 15 prostate stage IV cancer patients and 15 normal blood donors. Both single CTCs and CTC aggregates were measured to determine whether differences exist in the physical characteristics of these two populations. Cells contained in CTC aggregates had less area and length, on average, than single CTCs. Nuclear to cytoplasmic ratios between single CTCs and CTC aggregates were similar. This detection method may assist future studies in determining which population of cells is more physically likely to contribute to metastasis and VTE.

Fluid biopsy for circulating tumor cell identification in patients with early-and late-stage non-small cell lung cancer: a glimpse into lung cancer biology

Circulating tumor cell (CTC) counts are an established prognostic marker in metastatic prostate, breast and colorectal cancer, and recent data suggest a similar role in late stage non-small cell lung cancer (NSCLC). However, due to sensitivity constraints in current enrichment-based CTC detection technologies, there are few published data about CTC prevalence rates and morphologic heterogeneity in early-stage NSCLC, or the correlation of CTCs with disease progression and their usability for clinical staging. We investigated CTC counts, morphology and aggregation in early stage, locally advanced and metastatic NSCLC patients by using a fluid-phase biopsy approach that identifies CTCs without relying on surface-receptor-based enrichment and presents them in sufficiently high definition (HD) to satisfy diagnostic pathology image quality requirements. HD-CTCs were analyzed in blood samples from 78 chemotherapy-naïve NSCLC patients. 73% of the total population had a positive HD-CTC count (>0 CTC in 1 mL of blood) with a median of 4.4 HD-CTCs mL⁻¹ (range 0-515.6) and a mean of 44.7 (±95.2) HD-CTCs mL⁻¹. No significant difference in the medians of HD-CTC counts was detected between stage IV (n = 31, range 0-178.2), stage III (n = 34, range 0-515.6) and stages I/II (n = 13, range 0-442.3). Furthermore, HD-CTCs exhibited a uniformity in terms of molecular and physical characteristics such as fluorescent cytokeratin intensity, nuclear size, frequency of apoptosis and aggregate formation across the spectrum of staging. Our results demonstrate that despite stringent morphologic inclusion criteria for the definition of HD-CTCs, the HD-CTC assay shows high sensitivity in the detection and characterization of both early- and late-stage lung cancer CTCs. Extensive studies are warranted to investigate the prognostic value of CTC profiling in early-stage lung cancer. This finding has implications for the design of extensive studies examining screening, therapy and surveillance in lung cancer patients.

Site-specific DNA-antibody conjugates for specific and sensitive immuno-PCR

Antibody conjugates are widely used as diagnostics and imaging reagents. However, many such conjugates suffer losses in sensitivity and specificity due to nonspecific labeling techniques. We have developed methodology to site-specifically conjugate oligonucleotides to antibodies containing a genetically encoded unnatural amino acid with orthogonal chemical reactivity. These oligobody molecules were used in immuno-PCR assays to detect Her2+ cells with greater sensitivity and specificity than nonspecifically coupled fragments, and can detect extremely rare Her2+ cells in a complex cellular environment. Such designed antibody-oligonucleotide conjugates should provide sensitive and specific reagents for diagnostics, as well as enable other unique applications based on oligobody building blocks.

Cytometric comparisons between circulating tumor cells from prostate cancer patients and the prostate tumor derived LNCaP cell line

Many important experiments in cancer research are initiated with cell line data analysis due to the ease of accessibility and utilization. Recently, the ability to capture and characterize circulating tumor cells (CTCs) has become more prevalent in the research setting. This ability to detect, isolate and analyze CTCs allows us to directly compare specific protein expression levels found in patient CTCs to cell lines. In this study, we use immunocytochemistry to compare the protein expression levels of total cytokeratin (CK) and androgen receptor (AR) in CTCs and cell lines from patients with prostate cancer to determine what translational insights might be gained through the use of cell line data. A non-enrichment CTC detection assay enables us to compare cytometric features and relative expression levels of CK and AR by indirect immunofluorescence from prostate cancer patients against the prostate cancer cell line LNCaP. We measured physical characteristics of these two groups and observed significant differences in cell size, fluorescence intensity and nuclear to cytoplasmic ratio. We hope that these experiments will initiate a foundation to allow cell line data to be compared against characteristics of primary cells from patients.

Relative contribution of preload and afterload to the reduction in cardiac output caused by nitric oxide synthase inhibition with L-N(G)-methylarginine hydrochloride 546C88

Objective: The nitric oxide synthase inhibitor L‐NG‐methylarginine hydrochloride (L‐NMMA HC1 546C88) causes reductions in cardiac output (CO), a potential limitation to clinical application. This drop in CO exceeds that from phenylephrine at matched systemic arterial pressure. We tested the hypothesis that the greater fall in CO attributable to L‐NMMA primarily reflects a difference in venoconstriction between agents, such that phenylephrine produces larger increases in preload (an independent determinant of CO). Design: Random infusion of phenylephrine or L‐NMMA. Setting: An animal research laboratory. Subjects: Eight healthy, conscious, male dogs. Interventions: L‐NG‐methylarginine hydrochloride (20 mg/kg for 1 hr) and phenylephrine (0.5 to 3 μg/kg/min) were administered into eight dogs chronically instrumented to measure left ventricular pressure and dimension. Data were measured at a constant heart rate (140 beats/min) to render CO proportional to stroke dimension. Measurements and Main Results: At a matched increase in afterload (effective arterial elastance), L‐NMMA increased preload (end‐diastolic dimension) to a lesser degree (3.8% ± 1.5%, p < .05) than phenylephrine (9.6% ± 1.6%, p < .05 vs. L‐NMMA). Neither L‐NMMA nor phenylephrine affected the slope of the end‐systolic pressure dimension relationship, although L‐NMMA shifted the relationship rightward (1.7 ± 0.7 mm, p < .05), consistent with a mild negative inotropic effect. L‐NMMA decreased the stroke dimension to a greater extent than phenylephrine (−24.1% ± 6.8% and −10.6% ± 3.4%, respectively, p < .05). Conclusions: Differential CO responses to phenylephrine and L‐NMMA were primarily attributable to changes in preload. Variable venular vs. arteriolar constrictor effects must be considered when evaluating the integrated cardiovascular response to a vasoactive agent.

Abstract 3619: The absence of cleaved caspase-3 in circulating tumor cells detected using a non-enrichment-based assay

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: The role of cleaved caspase-3 as an integral player in the apoptotic process of mammalian cells has prompted the investigation of an assay to detect cleaved caspase-3 in circulating tumor cells (CTCs) as one way to assess CTC viability. Methods: Using a previously developed non-enrichment based assay, nucleated blood cells and CTCs are adhered to a single slide. An antibody for cleaved caspase-3 was incorporated into the assay in addition to the existing antibodies for cytokeratin (to identify tumor cells) and CD45 (to identify white blood cells), as well as a nuclear stain (DAPI). The modified assay was initially tested on cultured MCF 10a cells spiked into normal donor blood. Before spiking, apoptosis was induced in these cells using staurosporine. Following validation of the assay in cell lines, the assay was performed using blood samples from 9 different breast cancer patients, as well as 3 different normal donor samples. Results: CTCs were detected in the patient samples as single cells, as well as clusters. The results of the assay showed that only 1 out of 896 detected CTCs was positive for cleaved caspase-3 (0.11%). Of these CTCs, 134 of them were found to be in clusters, and all 134 were negative for cleaved caspase-3, indicating that whether in clusters or as single cells, the vast majority of CTCs detected with this assay are not undergoing irreversible apoptotic processes via cleaved caspase-3. The results also showed that 0.40% of white blood cells in healthy donors expressed cleaved caspase-3, compared to 0.51% of the white cells in cancer patients, indicating that healthy donors and cancer patients express cleaved caspase-3 in their white blood cells at nearly the same rate. Conclusions: The morphologic characterization used in this platform to select healthy-appearing cells identifies a population of circulating tumor cells with virtually no evidence of caspase-related ongoing apoptosis, a finding that supports the morphologic impression of viability. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3619. doi:1538-7445.AM2012-3619

Non-enrichment-based method for analysis of androgen receptor expression in circulating tumor cells (CTCs) in patients with metastatic castrate-resistant prostate cancer.

194 Background: We have established a fluid phase biopsy approach that identifies CTCs which preserves cytologic features in high-definition (HD) for diagnostic pathology without using immune or surface receptor-based enrichment. HD-CTCs identified with this approach can be used for enumeration and molecular characterization. METHODS Blood was collected from metastatic prostate cancer patients and normal donors in Cyto-Chex tubes (Streck, Omaha, NE) as part of IRB approved protocols at each site. Following erythrocyte lysis, 3 million nucleated cells were deposited on a glass slide. Samples were incubated with a pan-cytokeratin (CK), CD45, and androgen receptor (AR) antibodies and counter-stained with DAPI. LNCaP cells were spiked into normal blood. Images were obtained with a fluorescent scanning microscope and analyzed with a computer algorithm. Candidate HD-CTCs were subsequently verified by expert readers. Slides were re-imaged for quantitative analysis using at a fixed exposure and gain. RESULTS A total of 227 CTCs from ten patients were compared to 20 LNCaP cells. The median (range) HD-CTCs in this cohort was: 9 (1-62) cells/ml. The mean ± standard deviation measurements in HD-CTCs were observed: CK intensity 60.4±154; total cell area 89.0 ± 53.8 µm2; nuclear area 61.1 ± 36.0 µm2. LNCaP cells spiked into normal blood gave the following values: CK intensity 1166+/-306; total cell area 143 ± 48.1 µm2; nuclear area 63.1 ± 18.6 µm2. CTCs were additionally classified as either AR positive (AR+) or AR negative (AR-). 37 of the 227 (16.3%) HD-CTCs were AR+. The average CK intensity was significantly higher in AR+ versus AR- cells at 174.23 and 39.86, respectively (p<0.001). The AR expression intensity in AR+ HD-CTCs and LNCaP cells was comparable at 979.4 and 902.2, respectively (p=0.824). CONCLUSIONS We find a positive association between AR and CK expression on a per cell basis. Further, we find AR is expressed at comparable levels in CTCs from patients and human prostate cancer cells in culture. The HD-CTC based approach may be used for enumeration and molecular interrogation of CTCs in patients with prostate cancer.

Abstract 3630: Non-enrichment based method for analysis of androgen receptor expression in circulating tumor cells (CTCs) in patients with metastatic castrate resistant prostate cancer

Background: We have established a fluid phase biopsy approach that identifies CTCs which preserves cytologic features in high-definition (HD) for diagnostic pathology without using immune or surface receptor-based enrichment. HD-CTCs identified with this approach can be used for enumeration and molecular characterization. Methods: Blood was collected from metastatic prostate cancer patients and normal donors in Cyto-Chex® tubes (Streck, Omaha, NE) as part of IRB approved protocols at each site. Following erythrocyte lysis, 3 million nucleated cells were deposited on a glass slide. Samples were incubated with a pan-cytokeratin (CK), CD45, and androgen receptor (AR) antibodies and counter-stained with DAPI. LNCaP cells were spiked into normal blood. Images were obtained with a fluorescent scanning microscope and analyzed with a computer algorithm. Candidate HD-CTCs were subsequently verified by expert readers. Slides were re-imaged for quantitative analysis using at a fixed exposure and gain. Results: A total of 227 CTCs from ten patients were compared to 20 LNCaP cells. The median (range) HD-CTCs in this cohort was: 9 (1-62) cells/ml. The mean ± standard deviation measurements in HD-CTCs were observed: CK intensity 60.4±154; total cell area 89.0 ± 53.8 μm2; nuclear area 61.1 ± 36.0 μm2. LNCaP cells spiked into normal blood gave the following values: CK intensity 1166+/−306; total cell area 143 ± 48.1 μm2; nuclear area 63.1 ± 18.6 μm2. CTCs were additionally classified as either AR positive (AR+) or AR negative (AR-). 37 of the 227 (16.3%) HD-CTCs were AR+. The average CK intensity was significantly higher in AR+ versus AR- cells at 174.23 and 39.86, respectively (p Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3630. doi:1538-7445.AM2012-3630

Abstract 5225: Quantification of circulating tumor cell aggregates in breast cancer patient blood using an enrichment-free detection method

Circulating tumor cells (CTCs) have been implicated as a potential population of cells that may seed metastasis in cancer patients. In order to characterize and understand this population of cells, an enrichment-free immunofluorescence detection method was developed by our lab. This method take whole patient blood and classifies cells based on cytokeratin (CTCs) and CD45 (WBCs) antibody staining. Using this CTC detection method, a population of cells residing in tumor cell aggregates was observed in blood draws from Stage IV breast cancer patients. It was previously observed in ex vivo mouse experiments that homotypic aggregate formation of tumor cells may increase metastatic efficiency (Glinsky, et al., Cancer Research, 2003). In this work, we seek to determine if a significant proportion of CTCs reside in homotypic aggregates in patient blood by enumerating CTC aggregates from the blood draws of 23 Stage IV breast cancer patients and 16 healthy donor patients. Preliminary analysis measuring associations of CTCs with other nucleated cells found in patient blood draws revealed that ∼43% of cytokeratin-positive (CK+) cells found in breast cancer patient samples localize with either other CK+ or white blood cells (WBCs) versus 14% in healthy donor patient samples. Furthermore, ∼19% of WBCs were found to be associated with either CK+ or other WBCs in breast cancer patient samples versus ∼7% in healthy donor patient samples. Pathological review confirming CK+ cells as CTCs revealed that of the CTCs detected in patient blood after pathological review, ∼2% of CTCs were found as homotypic aggregates versus ∼0.07% in healthy donor samples (p=0.0005). Four breast cancer patients were found to have no CTC aggregates. Two breast cancer patients had significantly higher than average CTC aggregate percentages (∼6% and ∼7%). Patients will continue to be monitored to measure any differences in disease outcome of patients with high incidence of CTC aggregates versus patients with low incidence of CTC aggregates and healthy donors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5225. doi:10.1158/1538-7445.AM2011-5225