Electrical conductance time constants for freely decaying arcs

Electrical conductance time constants for the early stages of free decay after current modulation have been calculated from experimental measurements on a 5 mm diameter cascade arc at atmospheric pressure. The time constants were found by measuring the electric field response of the asymptotic portion of the arc column immediately after a sudden step decrease of arc current. The electric field strength was monitored by means of the copper cooling disks of the cascade, whose probe characteristics were studied thoroughly. The initial high current was supplied by a capacitor discharge circuit which was inductively compensated to produce a square wave pulse of ∼ 2 msec duration. Time constants for initial decay were measured in both argon and nitrogen for initial currents ranging from 100 to 400 amperes. The initial free decay time constants of nitrogen were found to increase weakly from approximately 25 to 35 usec over the initial current range considered. The time constants of argon decreased from approximately 100 to 60 Μsec over the same initial current range.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45820/1/10050_2005_Article_BF01392412.pd

Gene expression of breast cancer related genes in circulating tumour cells (CTCs) from patients with metastatic breast cancer

Introduction: Detection of circulating tumour cells (CTCs) in peripheral blood has an established prognostic significance in patients with metastatic breast cancer. Change in the number of detected CTCs is also an indication of response to therapy. Characterisation of CTCs could provide easily accessible treatment predictive information of present cancer cells within the patient and could reveal important knowledge about the metastatic process. The aim of this pilot study was to characterize CTCs with regard to both treatment predictive and more experimental markers by analysing the expression of genes associated with breast cancer.Methods: Blood samples from twelve patients with metastatic breast cancer included in the ongoing CTC-MBC study at Lund University, Sweden (Clinical Trials Id. NCT01322893) were analysed in this pilot study. Systemic treatment included endocrine, targeted and chemotherapy regimen. Blood samples were collected before start of 1st line therapy and at four time points. If progression occurred, a new round of samples was taken. CTCs were isolated from whole blood using the commercial kits AdnaTest EMT1/stem cell and AdnaTest EMT2/stem cell (AdnaGen AG, Langenhagen, Germany). With this method, CTCs are captured using antibodies directed against EpCAM and MUC-1 (EMT1-kit) or EpCAM, HER2 and EGFR (EMT2-kit). Gene expression analyses from CTCs at each time point was performed by TATAA Biocenter (Gothenburg, Sweden) using qPCR. 38 breast cancer related genes were analysed including the oestrogen receptor (ESR), HER2, VEGFR2, ALDH1, PI3K, PTEN and TWIST1.Results: Using positive expression of pseudo-markers EpCAM, MUC1 and HER2 as definition of CTCs, 6 of 12 patients were positive for CTCs. However, gene expression of additional markers in potential CTCs suggests complex patterns such as an increase in TWIST1, ALDH1 and SATB1 at time of progression.Conclusions: We present gene expression data from CTCs isolated before and during therapy in metastatic breast cancer patients. This type of characterisation could provide information of importance for treatment response and clinical outcome.Clinical trial identification: NCT01322893, March 24 201

Molecular characterization of circulating tumor cells from patients with metastatic breast cancer reflects evolutionary changes in gene expression under the pressure of systemic therapy

Resistance to systemic therapy is a major problem in metastatic breast cancer (MBC) that can be explained by initial tumor heterogeneity as well as by evolutionary changes during therapy and tumor progression. Circulating tumor cells (CTCs) detected in a liquid biopsy can be sampled and characterized repeatedly during therapy in order to monitor treatment response and disease progression. Our aim was to investigate how CTC derived gene expression of treatment predictive markers (ESR1/HER2) and other cancer associated markers changed in patient blood samples during six months of first-line systemic treatment for MBC. CTCs from 36 patients were enriched using CellSearch (Janssen Diagnostics) and AdnaTest (QIAGEN) before gene expression analysis was performed with a customized gene panel (TATAA Biocenter). Our results show that antibodies against HER2 and EGFR were valuable to isolate CTCs unidentified by CellSearch and possibly lacking EpCAM expression. Evaluation of patients with clinically different breast cancer subgroups demonstrated that gene expression of treatment predictive markers changed over time. This change was especially prominent for HER2 expression. In conclusion, we found that changed gene expression during first-line systemic therapy for MBC could be a possible explanation for treatment resistance. Characterization of CTCs at several time-points during therapy could be informative for treatment selection