Detection of Aeromonas salmonicida subsp. salmonicida infection in zebrafish by labelling bacteria with GFP and a fluorescent probe based on the siderophore amonabactin

Zebrafish (Danio rerio) is an excellent model to study bacterial infections in fish and their treatment. We used zebrafish as a model of infection for Aeromonas salmonicida subsp. salmonicida (hereinafter A. salmonicida), the causative agent of fish furunculosis. The infection process of A. salmonicida was studied by immersion of zebrafish larvae in 2 different doses of the bacteria and the fish mortality was monitored for three days. The bacterium caused a high mortality (65 %) in zebrafish larvae only when they were exposed to a high bacterial concentration (107 bacterial cells/mL). To evaluate the use of fluorescence microscopy to follow A. salmonicida infection in vivo, two different fluorescent strains generated by labeling an A. salmonicida strain with either, the green fluorescent protein (GFP), or with a previously reported siderophore amonabactin-sulforhodamine B conjugate (AMB-SRB), were used. The distribution of both labeled bacterial strains in the larvae tissues was evaluated by conventional and confocal fluorescence microscopy. The fluorescent signal showed a greater intensity with the GFP-labeled bacteria, so it could be observed using conventional fluorescence microscopy. Since the AMB-SRB labeled bacteria showed a weaker signal, the larvae were imaged using a laser scanning confocal microscope after 48 h of exposure to the bacteria. Both fluorescent signals were mainly observed in the larvae digestive tract, suggesting that this is the main colonization route of zebrafish for waterborne A. salmonicida. This is the first report of the use of a siderophore-fluorophore conjugate to study a bacterial infection in fish. The use of a siderophore-fluorophore conjugate has the advantage that it is a specific marker and that does not require genetic manipulation of the bacteria.

Expression of Gene Trios as Predictive Markers of Response to Doxorubicin Based Primary Chemotherapy in Breast Cancer Patients

Some studies have been carried out to identify a gene expression profile predictive of drug response in breast cancer patients and assessed the reproducibility of the model in an independent group of patients. In common, these studies have used the same technique already used to identify the panel of genes in a training set, to verify accuracy of the model in a validation set. We have previously identified through cDNA microarray technology gene trios whose expression was capable of predicting response to neoadjuvant chemotherapy based in doxorubicin and cyclophosphamide in breast cancer patients. We have now evaluated whether expression of these genes analyzed by real time RT-PCR, which represents a more accessible technique, would reproduce cDNA microarray results in separating responsive from non-responsive patients. Twenty eight samples, already studied by cDNA microarray, were analyzed as a technical validation group and subsequently, another 14 samples were evaluated, as a biological validation group. Expression of nine genes (defining five trio combinations, previously identified) was evaluated by RT-PCR in samples from the technical validation group, to define the separating plane, using linear discriminant analysis. Among the five trios, the best separation of tumors was conferred by RPL37A, XLHSRF-1 based trios (with NOTCH1 or NUP210, as third genes), which correctly classified 86% of samples from the technical validation group and 82% in a cross-validation analysis (leave-one-out). Next, samples from the biological validation group were spatially distributed using the pre-established features from these two trios, resulting in 71% correct classification. Additionally, other gene combinations were searched for a higher accuracy in discriminating response and expression of a new trio, RPL37A, SMYD2 and MTSS1, correctly classified 86% and 79% of samples from the technical validation (leave-one-out cross-validation) and the biological validation groups, respectively. Expression values evaluated by cDNA microarray and RT-PCR are reproducible, however they are not exactly the same as these methods are based on different technical principles and normalization approaches. Our data indicate that care should be taken when substituting techniques in an attempt to reproduce a model. In conclusion, expression of the gene trio RPL37A, SMYD2, MTSS1, as evaluated by RT-PCR, is a potential candidate as predictive marker of response to neoadjuvant chemotherapy in breast cancer patients.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2040.

Breast Cancer Gene Expression Profile in Post-Menopausal Patients Supplemented with Vitamin D

Vitamin D supplementation is indicated for post-menopausal women to prevent osteoporosis and lower 25(OH)2D3 or 1,25(OH)2D3 serum levels have been associated with breast cancer incidence or prognosis (metastasis). The antiproliferative effects of vitamin D are observed in breast cancer cell lines exposed to phamacological doses of calcitriol (1,25(OH)2D3, 100nM) but whether physiological doses are sufficient to produce growth inhibition in vivo is not known. The aim of our study was to investigate gene expression profile changes of breast cancer samples from patients supplemented with calcitriol, presenting an anti-proliferative effect on the tumor. Post-menopausal women diagnosed with breast cancer were instructed to take one (0.25ug/day, n=8) or two (0.50ug/day, n=8) tablets of calcitriol after tumor biopsy. Median time of supplementation was 30 days. Sixteen tumor samples were collected during biopsy (before supplementation) and breast surgery (after supplementation). Proliferation index was evaluated by tumor Ki-67 immunohistochemistry (IHC) expression in breast cancer samples before and after calcitirol supplementation and 1000 cells were counted by three observers (p < 0,001, Pearson's correlation). After establishing a counting error between observers, the cut-off value was fixed in 26.53% (percentile 60%) to define response. Patients were then categorized as responsive (a reduction of more than 26.53% on positive Ki-67 positive cells) and non-responsive (difference between samples before and after supplementation not exceeding 26.53%). Among our sixteen patients, all were categorized as responsive to calcitriol supplementation except for two. So far, gene expression profile of two patients (both categorized as responsive) has been analyzed using the U133 Plus 2.0 Affymetrix Gene Chips from 100ng of total RNA. To verify signalling pathways possibly involved in response to vitamin D exposure, additional five samples from a parallel study, in which breast cancer samples from post menopausal patients were collected at surgery and treated in vitro with a low concentration of calcitriol, 0.5nM (that can be attained with subcutaneous administration of doses of 8ug calcitriol, without hypercalcemia) for 24h, were included in the analysis. All samples had RNA hybridized to the same gene chips. Results were normalized and analyzed using RMA and Mev.TM4 softwares. CYP24A1, a target gene of vitamin D, presented a positive regulation after calcitriol supplementation in all samples analyzed. Differentially expressed genes were involved in the regulation of cell cycle [SMAD2, cyclin E, YWHAQ (14-3-3 family] and calcium signalling (HTR7, PTGER1 and PTGER2). Our results indicate that the tumor proliferation index is reduced upon calcitriol supplementation. Moreover, potentially regulated pathways in breast cancer specimens after administration of low doses of calcitriol are regulation of cell cycle and calcium signaling.Supported by FAPESP 2007/01111-0 – 2007/04799-2

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6128.

Differential Gene Expression Profiles in Breast Cancer Tumors from Young and Post-Menopausal Patients

Breast cancer in young patients (<35 yrs) has been hypothesized to be more histologically aggressive than those occurring in older cohorts, based mainly in their histopahtological features and worse prognosis. Our current knowledge of the genes involved in such differences is limited. To obtain insight into the molecular processes underlying tumorigenesis in young women we have used 44K cDNA microarrays (Agilent) to compare the gene expression profiles of 30 samples obtained from patients younger than 35 years (median 32,5, range 25-35) and 19 post-menopausal patients (median 66, range 55-88 ), all of them with ductal invasive carcinoma. Both age groups showed similar incidence of ER and PR-positive cases (70 and 60%, respectively). We considered as differentially expressed genes those presenting a p value below 0.01(t test) and fold variation of+/- 2.5.Gene ontology was performed using the GOTree machine tool (GOTM). By such criteria, 121 genes (86% down-regulated) were identified between the two groups here analyzed. In tumors arising in younger women we found an overrepresentation of genes involved with G-protein receptor signaling,cytoskeleton and muscle development, including ankyrin 3,filamin B, gfsarcoglycan and small proline- rich protein, one of the cornified-envelope structural precursor protein. In addition, solely in the younger women set we compared the gene profiles between women with (n =19) or without (n = 10) familial history of breast carcinoma. Using the same criteria, 59 transcripts distinguished the two subsets: GO categories over represented in tumors from patients with familial history included cell-cell adhesion, cytoskeleton organization,cell motility and protein binding related genes. These results indicate that breast cancer tumors arising in young women, besides their uniqueness regarding tumorigenesis, also differ among familial and non-familial cases as revealed by gene expression profiles.Support: FAPESP 04/14029-1

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6138.

Experimental study of the connections of the preglomerular nuclei and corpus mamillare in the rainbow trout, Oncorhynchus mykiss

The preglomerular complex of trout consists of the anterior (aPGN) and medial (mPGN) preglomerular nuclei and the corpus mamillare (CM). In order to improve knowledge on this complex, we applied a lipophilic neuronal tracer (DiI) to the three nuclei. These nuclei received afferents from the medial part of the dorsal telencephalic area (Dm), the ventral part of the ventral telencephalic area (Vv), the preoptic nucleus, the periventricular layer of the rostral optic tectum and the central posterior thalamic nucleus. The aPGN also received numerous toral projections and, sent efferents to the anterior tuberal nucleus. In addition, both the aPGN and the mPGN nuclei gave rise to efferents to the dorsal region of the dorsal telencephalic area (Dd), whereas the medial preglomerular nucleus and the CM sent fibers to the torus lateralis and the diffuse nucleus, as confirmed by reciprocal labeling. A small mPGN/CM subgroup projected to the optic tectum. These results suggest close functional inter-relationship between the trout preglomerular complex and two telencephalic regions (Dm and Vv). In addition, all nuclei of the complex receive preoptic, tectal and dorsal thalamic afferents, whereas the aPGN and mPGN are related with acoustic-lateral ascending pathways, and the mPGN and CM with the central region of the dorsal telencephalic area and visceral/gustatory pathways.