Flow cytometric method for determining folate receptor expression on ovarian carcinoma cells.

The alpha-folate receptor (alpha-FR) is a folate transporter with restricted expression levels in normal tissues. It is over-expressed in several cancers, particularly epithelial carcinomas, including nonmucinous ovarian carcinoma. It offers a novel therapeutic target for selective imaging and cytotoxic agents. Measurement of the receptor could be a valuable tool in selecting patients more likely to respond to new drugs that target the alpha-FR, and monitoring them while on treatment. While tumor samples are often unavailable, a number of patients who relapse develop ascites, which are often rich in tumor cells. We have therefore developed a triple antibody flow cytometric method to assess alpha-FR expression on tumor cells from ascites. An antibody to BerEP4, an epithelial cell marker expressed on >90% ovarian cancers, labeled with fluorescein, and an alpha-FR antibody labeled with antimouse-phycoerythrin have been used to label tumor cells, with a CD45-phycoerythrin-cyanine5 antibody used to exclude white blood cells from the analysis. The method was optimized using human carcinoma cell lines (JEG-3, IGROV-1, and KB cells). Calibrated beads were used to quantify the number of antibodies bound per cell. The triple antibody protocol successfully measured alpha-FR expression levels in cell lines spiked with blood. Tumor cells were obtained from ascites in 25 patients with relapsed ovarian cancer. In each case sufficient cells were harvested to identify an epithelial cell population to estimate the number of binding sites/cell. All the samples contained a single population of BerEP4, alpha-FR positive cells between 5x10(3) and 5x10(5) antibody binding sites/cell. The method can be used to determine the number of anti-alpha-FR antibodies bound per epithelial cell in ascites from patients with ovarian carcinoma. The results obtained were reproducible and the method could be applied to specimens that had been stored at -80 degrees C.

Potentiation of paclitaxel activity by the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin in human ovarian carcinoma cell lines with high levels of activated AKT.

Activation of the phosphatidylinositol-3-kinase (PI3K)/AKT survival pathway is a mechanism of cytotoxic drug resistance in ovarian cancer, and inhibitors of this pathway can sensitize to cytotoxic drugs. The HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) depletes some proteins involved in PI3K/AKT signaling, e.g., ERBB2, epidermal growth factor receptor (EGFR), and phosphorylated AKT (p-AKT). 17-AAG and paclitaxel were combined (at a fixed 1:1 ratio of their IC(50)) in four ovarian cancer cell lines that differ in expression of p-AKT, EGFR, and ERBB2. The EGFR-overexpressing A431 and KB epidermoid cell lines were also included. Combination indices (CI) were calculated using the median-effect equation and interpreted in the context of 17-AAG-mediated inhibition of PI3K signaling. Synergy was observed in IGROV-1- and ERBB2-overexpressing SKOV-3 ovarian cancer cells that express a high level of constitutively activated p-AKT [CI at fraction unaffected (fu)(0.5) = 0.50 and 0.53, respectively]. Slight synergy was observed in A431 cells (moderate p-AKT/overexpressed EGFR; CI at fu(0.5) = 0.76) and antagonism in CH1 (moderate p-AKT), HX62 cells (low p-AKT), and KB cells (low p-AKT/overexpressed EGFR; CI at fu(50) = 3.0, 3.5, and 2.0, respectively). The observed effects correlated with changes in the rate of apoptosis induction. 17-AAG induced a decrease in HSP90 client proteins (e.g., C-RAF, ERBB2, and p-AKT) or in downstream markers of their activity (e.g., phosphorylated extracellular signal-regulated kinase or p-AKT) in SKOV-3, IGROV-1, and CH1 cells at IC(50) concentrations. A non-growth-inhibitory concentration (6 nmol/L) reduced the phosphorylation of AKT (but not extracellular signal-regulated kinase) and sensitized SKOV-3 cells to paclitaxel. In conclusion, 17-AAG may sensitize a subset of ovarian cancer to paclitaxel, particularly those tumors in which resistance is driven by ERBB2 and/or p-AKT.

Cell-cycle analysis of asynchronous populations.

Cells are incubated continuously in bromodeoxyuridine (BrdUrd), which is incorporated into cells synthesizing DNA. At intervals, cells are harvested and nuclei are prepared and stained with a bis-benzimidazole, Hoechst 33258, and propidium iodide. In the flow cytometer, the dyes are excited by UV and blue and red fluorescences recorded. BrdUrd quenches the blue fluorescence of the Hoechst dye. The degree of quenching records the progress of the cell through S phase(s); the red (PI) fluorescence yields the cell cycle phases. By this means, the progress of cells around the cell cycle can be followed and the effects of cytotoxic drugs, radiation, and other treatments observed.

Measurement of proliferation marker Ki67 in breast tumour FNAs using laser scanning cytometry in comparison to conventional immunocytochemistry.

BACKGROUND: A variety of markers, including Ki67, estrogen receptors (ER), and progesterone receptors (PgR), are frequently measured in fine needle aspirates from human breast carcinomas. Previously, we demonstrated the use of laser scanning cytometry (LSC) for the measurement of Ki67, ER, and PgR in a human breast carcinoma cell line, MCF7 (21). In the present study, we investigated the expression of Ki67 in breast tumour fine needle aspirates (FNAs) using LSC and compared the results to the data obtained using conventional immunocytochemistry (ICC). METHODS: A total of 11 sets of cytospins of FNAs taken from breast tumours at various stages of tamoxifen treatment were used. For LSC, the cytospins were stained for Ki67 with fluorescein using immunofluorescence; the nuclei were counterstained with propidium iodide. A parallel set of cytospins was stained using horseradish peroxidase and diaminobenzidine and scored manually by conventional light microscopy. RESULTS: Values for Ki67 obtained using the LSC were generally lower than ICC scores. The changes in Ki67 measured by the LSC were almost all parallel to those obtained by manual scoring of immunocytochemical stains. CONCLUSIONS: It should be possible to use LSC for the routine measurement of Ki67 marker in FNAs from human breast carcinomas.

Cell filtration-laser scanning cytometry for the characterisation of circulating breast cancer cells.

BACKGROUND: Epithelial cells may be detected in the circulation of the majority of patients with metastatic breast cancer. Quantification of such presumptive cancer cells might allow for the monitoring of patients with early or late stage disease as an early index of relapse. Additionally, biomarker analysis may allow a more rational approach to therapeutics. We have developed a new method for the detection and characterisation of these cells. METHODS: Blood was filtered through polycarbonate membranes containing cylindrical pores, 8 microm in diameter. All the red cells and a large majority of the white blood cells passed through the filter while the larger epithelial cells were trapped. Cells on the membrane were fixed in ethanol, stained with propidium iodide and anti-pan-cytokeratin-FITC (to identify epithelial cells). The filters were then examined by laser scanning cytometry (LSC), which allowed enumeration and localisation of cells. RESULTS: With normal blood spiked with cells from breast carcinoma cell lines, 99.9% of the leukocytes passed through the membrane, while close to 100% of the epithelial cells were trapped, with a detection limit of less than one epithelial cell/ml of blood. All of 20 samples from patients with widespread metastatic disease contained cytokeratin-positive cells with the morphological characteristics of carcinoma cells, the number of cells ranging from 0.2 to 5.7/ml of blood. CONCLUSIONS: Cell filtration-LSC is a viable technique for detecting and studying breast carcinoma cells in peripheral blood.

Investigating the relationship between the cell cycle and apoptosis using flow cytometry.

Methods for using flow cytometry to investigate the relationship between the induction of apoptosis and the cell cycle are discussed. Methods for following cell cycle progression are also briefly reviewed. The methods are illustrated using a specific example of the effect of withdrawing an essential growth factor from a cell line.