Dual-isotope subtraction SPECT-CT in parathyroid localization.

OBJECTIVE: The aim of this study was to investigate the accuracy of locating parathyroid adenomas using dual-Isotope subtraction single-photon emission computed tomography-computed tomography (SPECT-CT) in comparison with clinical follow-up and pathology findings from surgery. PATIENTS AND METHODS: A retrospective cohort study of dual-isotope subtraction SPECT-CT was carried out on 224 consecutive patients who were diagnosed with primary hyperparathyroidism. All the patients were injected with 20 MBq of iodine-123-iodide, followed 20 min later by 900 MBq of technetium-99m-sestamibi. Planar neck and chest views and SPECT-CT images were acquired 15 min after administration, followed by an additional planar image set at 2 h to view washout; all images were dual energy. In all, 115 out of 224 of the patients imaged underwent parathyroid surgery. The imaging results were compared with pathology findings when available and, in those who did not undergo surgery, and in some complex cases, with clinical measures after a 2-year clinical follow-up period. FINDINGS: Out of the 224 patients, 135 patients had complete pathology and/or clinical follow-up data and were included in the analysis. The sensitivity of the subtraction SPECT-CT findings was measured to be 95%, with a specificity of 89% for the detection and localization of parathyroid adenomas. The positive predictive value was found to be 97% and the negative predictive value was found to be 83%. The accuracy of the technique was 94% in detecting parathyroid adenoma and 92% in accurate localization. CONCLUSION: Dual-isotope subtraction SPECT-CT imaging has a very high sensitivity and specificity in detecting and locating a parathyroid adenoma, showing that it is a very reliable preoperative imaging technique in primary hyperparathyroidism.

IGFBP5 induces cell adhesion, increases cell survival and inhibits cell migration in MCF-7 human breast cancer cells.

Maintenance of tissue boundaries is crucial for control of metastasis. We describe a new signalling pathway in which epithelial cell disruption can be minimised and thereby restricts epithelial-mesenchymal transgressions. This involves the release of insulin-like growth factor (IGF)-binding protein 5 (IGFBP5) from apoptotic cells, which increases the adhesion of epithelial cells on mesenchymal but not epithelial extracellular matrix (ECM), and involves the direct interaction of IGFBP5 and α2ß1 integrins. IGFBP5 also induced cell adhesion to vitronectin in the absence of αVß3 integrin, the vitronectin receptor, again through an α2ß1-integrin-dependent action, suggesting that IGFBP5 can induce spreading on matrices, even in the absence of the integrins normally used in this process. Using IGFBP5 mutants we demonstrate that the effect is IGF-independent but requires the heparin-binding domain in the C-terminus of IGFBP5. A truncated mutant containing only the C-terminal of IGFBP5 also induced adhesion. Adhesion induced by IGFBP5 was dependent on Cdc42 and resulted in activation of integrin-linked kinase (ILK) and Akt. Consistent with these changes, IGFBP5 facilitated prolonged cell survival in nutrient-poor conditions and decreased phosphorylation of the stress-activated kinase p38 MAPK (MAPK14). Whereas IGFBP5 enhanced adhesion, it inhibited cell migration, although this was not evident using the truncated C-terminal mutant, suggesting that effects of IGFBP5 on adhesion and migration involve different mechanisms. We anticipate that these responses to IGFBP5 would reduce the metastatic potential of cells.

Molecular interactions in the insulin-like growth factor (IGF) axis: a surface plasmon resonance (SPR) based biosensor study.

This review describes a comprehensive analysis of a surface plasmon resonance (SPR)-based biosensor study of molecular interactions in the insulin-like growth factor (IGF) molecular axis. In this study, we focus on the interaction between the polypeptide growth factors IGF-I and IGF-II with six soluble IGF binding proteins (IGFBP 1-6), which occur naturally in various biological fluids. We have describe the conditions required for the accurate determination of kinetic rate constants for these interactions and highlight the experimental and theoretical pitfalls, which may be encountered in the early stages of such a study. We focus on IGFBP-5 and describe a site-directed mutagenesis study, which examines the contribution of various residues in the protein to high affinity interaction with IGF-I and -II. We analyse the interaction of IGFBP-5 (and IGFBP-3) with heparin and other biomolecules and describe experiments, which were designed to monitor multi-protein complex formation in this molecular axis.

Cumulative mutagenesis of the basic residues in the 201-218 region of insulin-like growth factor (IGF)-binding protein-5 results in progressive loss of both IGF-I binding and inhibition of IGF-I biological action.

We have reported previously that mutation of two conserved nonbasic amino acids (G203 and Q209) within the highly basic 201-218 region in the C-terminal domain of IGF-binding protein-5 (IGFBP-5) decreases binding to IGFs. This study reveals that cumulative mutagenesis of the 10 basic residues in this region, to create the C-Term series of mutants, ultimately results in a 15-fold decrease in the affinity for IGF-I and a major loss in heparin binding. We examined the ability of mutants to inhibit IGF-mediated survival of MCF-7 cells and were able to demonstrate that this depended not only upon the affinity for IGF-I, but also the kinetics of this interaction, because IGFBP-5 mutants with similar affinity constants (K(D)) values, but with different association (Ka) and dissociation (Kd) rate values, had markedly different inhibitory properties. In contrast, the affinity for IGF-I provided no predictive value in terms of the ability of these mutants to enhance IGF action when bound to the substratum. Instead, these C-Term mutants appeared to enhance the actions of IGF-I by a combination of increased dissociation of IGF-IGFBP complexes from the substratum, together with dissociation of IGF-I from IGFBP-5 bound to the substratum. These effects of the IGFBPs were dependent upon binding to IGF-I, because a non-IGF binding mutant (N-Term) was unable to inhibit or enhance the actions of IGF-I. These results emphasize the importance of the kinetics of association/dissociation in determining the enhancing or inhibiting effects of IGFBP-5 and demonstrate the ability to generate an IGFBP-5 mutant with exclusively IGF-enhancing activity.