BACKGROUND Although recent laboratory and population studies suggest that prostate cancer may be responsive to insulin, there is a gap in knowledge concerning the expression of insulin receptors on benign or malignant prostate tissue. METHODS We immunostained 644 cores on tissue microarrays prepared from 29 prostate tissue samples without malignancies, 78 Gleason grade 3 cancers, 21 Gleason grade 4 cancers and 33 Gleason grade 5 cancers with antibodies against the insulin‐like growth factor I receptor and the insulin receptor. RESULTS We observed immunoreactivity with both antibodies, which implies the presence of hybrid receptors as well as IGF‐I receptors and insulin receptors. Insulin receptor staining intensity was significantly (P < 0.001) higher on malignant than benign prostate epithelial cells. Analysis of information from public gene expression databases confirmed that co‐expression of insulin receptor mRNA and IGF‐I receptor mRNA is common in prostate cancer specimens. RT‐PCR methods provided evidence for the presence of mRNA for both IR‐A and IR‐B insulin receptor isoforms. CONCLUSION These observations document the presence of insulin receptors on primary human prostate cancers. The findings are relevant not only to ongoing clinical trials of drug candidates that target IGF‐I and/or insulin receptors, but also to the hypothesis that obesity‐associated hyperinsulinemia mediates the adverse effect of obesity on prostate cancer prognosis. Prostate 69: 33–40, 2009. © 2008 Wiley–Liss, Inc.

Many receptor tyrosine kinases possess an "activation loop" containing three similarly placed tyrosine autophosphorylation sites. To examine their roles in the TRK NGF receptor, these residues (Tyr-670, Tyr-674, and Tyr-675) were mutated singly and in all combinations to phenylalanine and stably expressed in Trk-deficient PC12nnr5 cells. All mutant receptors showed significantly diminished nerve growth factor (NGF)-stimulated autophosphorylation, indicating impaired catalytic activity. NGF-induced neurite outgrowth exhibited dose-responsive behavior when transfectants were compared by relative receptor expression and exhibited a functional hierarchy: wild type > Y670F Y674F > > Y675F YY670/674FF ‫؍‬ YY670/675FF > > YY674/675FF > YYY670/674/675FFF. NGF-induced tyrosine phosphorylation of Shc, ERKs, and SNT and immediate early gene inductions generally paralleled neurogenic potential. However, activation of phosphatidylinositol 3-kinase and tyrosine phosphorylation of phospholipase C␥-1 was essentially abolished. The latter effect appears due to selective inability of the mutated TRKs to autophosphorylate the tyrosine residue (Tyr-785) required for binding phospholipase C␥-1 and indicates that the "activation loop" tyrosines participate in NGF-dependent changes in receptor conformation. Our findings stress the importance that expression levels play in assessing the consequences of receptor mutations and that all three activation loop tyrosines have roles regulating both overall and specific NGF-mediated signaling through TRK.For many growth factors, ligand-mediated activation of receptor tyrosine kinases (RTKs) 1 is the first essential step leading to biological responses (1, 2). Nerve growth factor (NGF) and other neurotrophins bind to and activate particular members of the Trk receptor tyrosine kinase family (3, 4); NGF binds to and activates TRKA (5, 6). The pheochromocytomaderived PC12 cell line (7) has been highly useful for studying NGF signal transduction and its molecular mechanisms of action. PC12 cells respond to NGF by undergoing neuronal differentiation, survival in serum-free medium, cell hypertrophy, and regulation of numerous biochemical markers (8). NGF induces rapid tyrosine phosphorylation of TrkA and consequent phosphorylation and activation of signal transduction components including Shc, extracellular signal-regulated kinases (ERKs), phosphatidylinositol 3Ј-kinase (PI3ЈK), phospholipase C ␥-1 (PLC␥-1), and SNT (9). Activation of these signal transduction molecules culminates in downstream signaling events, including the induction of immediate early and late genes (10, 11).As with other ligands and their cognate RTKs (1, 2), NGF appears to initiate signaling through TrkA by the sequential steps of dimerization, trans-autophosphorylation on tyrosine residues and kinase activation, followed by binding and tyrosine phosphorylation of substrates (9,12,13). In vitro studies indicate that TRKA autophosphorylates at tyrosines 490, 670, 674, 675, and 785 (14, 15). To analyze the significance of thes...

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Intermittent PTH administration increased posterolateral fusion success in rabbits. Fusion bone mass and histologic determinants were also improved with PTH treatment. PTH has promise for use as an adjunctive agent to improve spinal fusion in clinical medicine.

Counter to previous reports, age, comorbidities, and sagittal balance did not influence treatment modality for AS. Operative treatment for younger patients was driven by increased coronal plane deformity. Conversely, pain and disability mandated treatment for older patients, independent of radiographic measures. These findings suggest that AS patients do not become uniformly disabled with age, and that disability can not be solely predicted by radiographic findings. These data should be considered when considering treatment for AS.

KIT receptor kinase activity is repressed, prior to stem cell factor binding, by unknown structural constraints. Using site-directed mutagenesis, we examined the role of KIT intracellular juxtamembrane residues Met-552 through Ile-563 in controlling receptor autophosphorylation. Alanine substitution for Tyr-553, Trp-557, Val-559, or Val-560, all sitting along the hydrophobic side of an amphipathic ␣-helix (Tyr-553-Ile-563) predicted by the Chou-Fasman algorithm, resulted in substantially increased spontaneous receptor phosphorylation, revealing inhibitory roles for these residues. Alanine substitution for other residues, most of which are on the hydrophilic side of the helix, caused no or slightly increased basal receptor phosphorylation. Converting Tyr-553 or Trp-557 to phenylalanine generated slight or no elevation, respectively, in basal KIT phosphorylation, indicating that the phenyl ring of Tyr-553 and the hydrophobicity of Trp-557 are critical for the inhibition. Although alanine substitution for Lys-558 had no effect on receptor phosphorylation, its substitution with proline produced high spontaneous receptor phosphorylation, suggesting that the predicted ␣-helical conformation is involved in the inhibition. A synthetic peptide comprising Tyr-553 through Ile-563 showed circular dichroism spectra characteristic of ␣-helix, supporting the structural prediction. Thus, the KIT intracellular juxtamembrane region contains important residues which, in a putative ␣-helical conformation, exert inhibitory control on the kinase activity of ligandunoccupied receptor.

Background Several studies have identified risk factors for proximal junctional kyphosis (PJK) after instrumentation for scoliosis, but the relative risks are unclear. Questions/purposes We identified risk factors for PJK in idiopathic scoliosis and determined their relative risks in a predictive model. Methods We retrospectively reviewed the charts of all 249 patients with idiopathic scoliosis who underwent surgery from 1996 to 2008. We compared those who developed PJK to those who did not. We identified risk factors for PJK and performed univariate and multivariate analyses to determine independent risk factors. We then used a Cox proportional-hazards model to evaluate the time to the development of PJK. The minimum followup time was 1.5 years (mean, 4 years; range, 1.5-9 years).

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