Magnetic resonance imaging: value of diffusion-weighted imaging in differentiating benign from malignant breast lesions.

OBJECTIVES: Although magnetic resonance imaging (MRI) has a high sensitivity in the detection of tumours, there is still much discussion about its role in breast cancer detection. MRI is not yet routinely used to further characterize lesions in patients diagnosed with breast cancer. This study investigated the impact of preoperative MRI on the surgical treatment of women with biopsy proven breast cancer. The diagnostic value of preoperative MRI was compared with that of conventional imaging (mammography and ultrasonography), and the diffusion-weighted imaging technique was also evaluated. STUDY DESIGN: 40 women underwent conventional imaging and biopsy as part of the clinical workup. In addition, preoperative MRI was performed in each patient. The kinetics of contrast captation were monitored and apparent diffusion coefficients were calculated. All imaging findings were compared with the histopathologic results, which were used as the gold standard. Differences in tumour extent, as determined by ultrasonography, MRI and histopathology, were evaluated. RESULTS: Contrast captation kinetics curves are mostly aspecific, while apparent diffusion coefficient values seem to correlate much better with tumour malignancy. MRI correlated more accurately with histopathological findings than ultrasonography and even revealed unsuspected multifocal and multicentric breast carcinoma in 20 patients (50%). The surgical plan of seven patients (18%) was changed as a result of the additional information provided by MRI. CONCLUSION: Diffusion-weighted imaging as a complementary tool to contrast captation kinetics and morphologic measurements may increase the specificity of MRI and help in differentiating between benign and malignant breast lesions. In addition, MRI yields more precise information than mammography and ultrasonography about the exact location, the extent, the multifocality or multicentricity of the tumour and can also detect possible additional tumours. Although MRI will never replace mammography (screening) or ultrasonography as a test for breast cancer in women with no high risk (e.g. BRCA 1 or 2 carriers), its use in a preoperative setting may allow more accurate staging of the disease, which in turn could result in a change in the treatment planning.

Diffusion of myelin oligodendrocyte glycoprotein in living OLN-93 cells investigated by raster-scanning image correlation spectroscopy (RICS).

Many membrane proteins and lipids are partially confined in substructures ranging from tens of nanometers to micrometers in size. Evidence for heterogeneities in the membrane of oligodendrocytes, i.e. the myelin-producing cells of the central nervous system, is almost exclusively based on detergent methods. However, as application of detergents can alter the membrane phase behaviour, it is important to investigate membrane heterogeneities in living cells. Here, we report on the first investigations of the diffusion behavior of the myelin-specific protein MOG (myelin oligodendrocyte glycoprotein) in OLN-93 as studied by the recently developed RICS (raster-scanning image correlation spectroscopy) technique. We implemented RICS on a standard confocal laser-scanning microscope with one-photon excitation and analog detection. Measurements on FITC-dextran were used to evaluate the performance of the system and the data analysis procedure.

Probing diffusion laws within cellular membranes by Z-scan fluorescence correlation spectroscopy.

The plasma membrane of various mammalian cell types is heterogeneous in structure and may contain microdomains, which can impose constraints on the lateral diffusion of its constituents. Fluorescence correlation spectroscopy (FCS) can be used to investigate the dynamic properties of the plasma membrane of living cells. Very recently, Wawrezinieck et al. (Wawrezinieck, L., H. Rigneault, D. Marguet, and P. F. Lenne. 2005. Biophys. J. 89:4029-4042) described a method to probe the nature of the lateral microheterogeneities of the membrane by varying the beam size in the FCS instrument. The dependence of the width of the autocorrelation function at half-maximum, i.e., the diffusion time, on the transverse area of the confocal volume gives information on the nature of the imposed confinement. We describe an alternative approach that yields essentially the same information, and can readily be applied on commercial FCS instruments by measuring the diffusion time and the particle number at various relative positions of the cell membrane with respect to the waist of the laser beam, i.e., by performing a Z-scan.

Diffusion of sphingomyelin and myelin oligodendrocyte glycoprotein in the membrane of OLN-93 oligodendroglial cells studied by fluorescence correlation spectroscopy.

Evidence has been accumulated that the plasma membrane of various mammalian cell types is heterogeneous in structure and may contain lipid microdomains (lipid rafts). This study focuses on the membrane organization of living oligodendrocytes, which are the myelin-producing cells of the central nervous system. Fluorescence correlation spectroscopy (FCS) was used to monitor the lateral diffusion of a lipid and of a protein in the oligodendroglial cell line OLN-93. The lipid was fluorescently labelled sphingomyelin (Bodipy FL-C5 SM). The protein was the myelin oligodendrocyte glycoprotein (MOG). In order to monitor the lateral diffusion of MOG, OLN-93 cells were transfected with a MOG-EGFP (enhanced green fluorescent protein) fusion plasmid. The measurements were performed at room temperature. FCS data were analyzed for two-dimensional (2D) diffusion according to three models which all included a triplet fraction: (a) 2D 1 component (2D1C), (b) 2D anomalous diffusion (2D1Calpha), and (c) 2D 2 components (2D2C). Preliminary results indicate that for the lipid case, the best fits are obtained with 2D2C. In the case of MOG-EGFP, 2D2C and 2D1Calpha give fits of similar quality. The parameter estimates obtained with 2D1Calpha, however, have a lower standard deviation. The anomaly parameter for MOG-EGFP is 0.59+/-0.01.

Cytokine-induced cell death in human oligodendroglial cell lines. II: Alterations in gene expression induced by interferon-gamma and tumor necrosis factor-alpha.

Cytokines, such as interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), can initiate dual effects resulting in either cell growth or cell death. In this study, the human oligodendroglial cell lines HOG and MO3.13 were used as a model to study the molecular mechanisms of cytokine-induced cell death in human oligodendrocytes. We have previously shown that TNF-alpha and IFN-gamma induce apoptosis in both oligodendroglial cell lines within 72 hr. In the present study, the cell death pathways operating within these cells were further investigated at the gene expression level. Both cell lines express a broad repertoire of caspases and apoptosis-related genes. Some of these genes are specifically up-regulated by cytokine treatment; e.g., caspase-1 is up-regulated by IFN-gamma. In addition to direct cytotoxic effects, IFN-gamma and TNF-alpha also enhance the expression of Fas, TNFR1, and MHC class I molecules in both cell lines. This suggests that cytokines can make oligodendrocytes more vulnerable to different cell death pathways in an inflammatory environment. cDNA microarray analysis of the HOG cell line revealed that TNF-alpha induces genes that regulate apoptosis, survival, inflammation, cell metabolism, and cell signaling. The data suggest that oligodendroglial cells activate both death and survival pathways upon cytokine challenges. However, the survival pathways seem to be unable to compete with the death signal after more than 24 hr of cytokine treatment. These results may contribute to the development of therapeutic strategies aimed at interfering with cytokine-induced cell death of oligodendrocytes in patients with multiple sclerosis.