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This process is tightly regulated by the rates of myosin light chain phosphorylation through the myosin light chain kinase and subsequent dephosphorylation via myosin phosphatase (MLCP) 2 (1-6). MLCP is a heterotrimer comprised of a 130-kDa myosin binding subunit (MBS), a 37-kDa protein phosphatase inhibitor catalytic subunit, and a 20-kDa subunit with no ascribed function (1-5). The importance of cGMP-dependent PKG-I␣ in vascular smooth muscle tone is supported by extensive studies demonstrating that PKG-I␣ regulates pathways of NO-dependent vascular relaxation that involve the MBS of MLCP (6). Protein-protein interactions between PKG-I␣ and MLCP are believed to be mediated by the N-terminal leucine zipper (LZ) domain of 59 residues in PKG-I␣ (PKG-I␣ 1-59 ) and C-terminal 180 residues of MBS (MBS CT180 ) in MLCP (1).In previous studies by Atkinson et al. (7), they described the dimer properties of PKG-I␣ (residues 1-39) and determined the structure of the PKG-I␣ monomer within this leucine-zipper dimer. We and others have shown that N-terminal PKG-I␣ is a homodimer in solution (7-9). Recently we have demonstrated that the LZ region of PKG-I␣, PKG-I␣ 1-59 , is indeed a coiled coil (CC) LZ dimer of ϳ38 residues commencing at residue Ala 9 and extending through to Gln 44 on the basis of our 15 N R 1 and R 2 relaxation data (10). Our NMR structure of this region of PKG-I␣ was determined using residual dipolar couplings as structural restraints, whereas the parallel orientation of this homodimer was determined using Prediction of Alignment from Structure (PALES), a method that evaluates the structural charge distribution of the monomer and dimer structures (10).The interaction between PKG-I␣ 1-59 and the CC and/or LZ domain of MBS CT180 has recently been documented by several workers (8,11,12). MBS CT180 is comprised of a predicted bind-

Purpose: Proteomic profiling of patients undergoing intensity-modulated radiotherapy (IMRT) for prostate cancer can identify unique biomarkers that reflect acute toxicity in normal tissues. Our objectives were to measure inflammatory cytokine proteins during IMRT and assess the variability of individual proteomic signatures. Experimental Design: Forty-two patients with intermediate-risk prostate cancer were recruited as follows: group 1, definitive IMRT (78 Gy in 39 fractions, n = 22), and group 2, IMRT postprostatectomy (66 Gy in 33 fractions, n = 20). Blood/urine samples were collected at baseline and weekly during IMRT. Acute toxicity was graded weekly during radiotherapy using CTC-AE v3.0 criteria. Multiplexed immunoassays were used to quantify cytokines including granulocyte macrophage colony-stimulating factor, IFN-γ, tumor necrosis factor-α, interleukin (IL)-1α, IL-2, IL6, IL-8, IL-10, and IL-12p70. Results: We observed positive correlations between cytokine expression between serum and plasma, but not between serum/plasma and urine. The Mann-Whitney test showed a significant increase in IFN-γ and IL-6 during IMRT (P = 0.0077, 0.0035). Increasing IL-2 and IL-1 expression were associated with increased probability of acute gastrointestinal and genitourinary toxicity, respectively. Conclusions: Determination of radiation-response signatures is feasible using multiplexed immunoassays and is a promising predictive early biomarker of toxicity outcomes. (Clin Cancer Res 2009;15(17):5576-83) Cellular damage caused by ionizing radiation induces specific proteins involved in DNA repair, cell death, inflammation, and other pathophysiologic responses (1). The majority of biomarker studies in radiation oncology have focused on predicting tumor response and survival (2). Clinically, the acute toxicity of prostate cancer radiotherapy manifest as gastrointestinal and genitourinary symptoms based on validated scoring criteria, [e.g., Common Terminology Criteria for Adverse Events (CTC-AE); ref. 3]. Radiotherapy dose escalation using intensity-modulated radiotherapy (IMRT) is associated with improved biochemical tumor control, yet still has radiation-induced toxicity. Dose-dependent markers of acute normal toxicity could help predict individuals at increased risk of radiotherapy-related injury and help to maximize the therapeutic ratio for individual patients.Rubin and colleagues were among the first to describe the role of cytokines (small glycoproteins involved in intercellular signaling) in mediating radiation toxicity (4). They showed in preclinical and clinical lung studies that levels of interleukin (IL)-1, transforming growth factor (TGF)-β, and tumor necrosis factor (TNF)-α were increased immediately after radiation exposure, and that chronically elevated TGF-β levels were associated with increased risk of pulmonary fibrosis. The link between radiation toxicity and cytokine expression is supported by studies showing that prolonged cytokine expression postradiotherapy is correlated to specific lung radi...

Background:High plasma osteopontin (OPN) has been linked to tumour hypoxia, metastasis, and poor prognosis. This study aims to assess whether plasma osteopontin was a biomarker of increasing progression within prostate cancer (PCa) prognostic groups and whether it reflected treatment response to local and systemic therapies.Methods:Baseline OPN was determined in men with localised (n=199), locally recurrent (n=9) and castrate-resistant, metastatic PCa (CRPC-MET; n=37). Receiver-operating curves (ROC) were generated to describe the accuracy of OPN for distinguishing between localised risk groups or localised vs metastatic disease. We also measured OPN pre- and posttreatment, following radical prostatectomy, external beam radiotherapy (EBRT), androgen deprivation (AD) or taxane-based chemotherapy.Results:The CRPC-MET patients had increased baseline values (mean 219; 56–513 ng ml−1; P<0.0001) compared with the localised, non-metastatic group (mean 72; 12–438 ng ml−1). The area under the ROC to differentiate localised vs metastatic disease was improved when OPN was added to prostate-specific antigen (PSA) (0.943–0.969). Osteopontin neither distinguished high-risk PCa from other localised PCa nor correlated with serum PSA at baseline. Osteopontin levels reduced in low-risk patients after radical prostatectomy (P=0.005) and in CRPC-MET patients after chemotherapy (P=0.027), but not after EBRT or AD.Conclusion:Plasma OPN is as good as PSA at predicting treatment response in CRPC-MET patients after chemotherapy. Our data do not support the use of plasma OPN as a biomarker of increasing tumour burden within localised PCa.

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Numerous proteomic methods are being employed, including high-throughput mass spectrometry and immunoassays, and using solid tissues, blood and urine for analysis. Given the potential complexity of cytokine and other protein responses, there is a need to assess proteomic signatures within serial samples as longitudinal studies during a course of fractionated radiotherapy (RT).

The cyclic GMP-dependent protein kinase type I (PKGI) 2 mediates vascular smooth muscle cell (VSMC) relaxation via the nitric oxide/ cyclic GMP pathway. One of the PKGI-dependent mechanisms of VSMC relaxation involves the inhibition of Ca 2ϩ mobilization (reviewed in Refs. 1, 2). Smooth muscle contraction begins upon receptor-mediated generation of inositol 1,4,5-triphosphate (IP 3 ), which releases intracellular stores of Ca 2ϩ from the sarcoplasmic reticulum and is followed by an influx of extracellular Ca 2ϩ via voltage-gated Ca 2ϩ channels (1, 3, 4). A rise in intracellular Ca 2ϩ activates the Ca 2ϩ /calmodulin-dependent myosin light chain kinase, which phosphorylates the myosin light chain, activating the myosin ATPase and actomyosin cross-bridge cycling, leading to an increase in tension (1). The ability of PKGI to oppose agonist-mediated Ca 2ϩ mobilization is well established (5-9), but the relative roles of the PKGI isoforms PKGI␣ and PKGI␤ are poorly understood.Many signaling events involved in Ca 2ϩ mobilization are regulated by PKGI. The phosphorylation of the thromboxane receptor by PKGI desensitizes signaling by this receptor in a manner analogous to G-protein-coupled receptor kinases (10, 11). Some of these studies were done in human platelets, which express predominantly PKGI␤ (12), suggesting that PKGI␤ can phosphorylate and attenuate signaling by the thromboxane receptor (11). The phosphorylation and activation of the regulator of G-protein signaling 2 (RGS2) by PKGI␣ terminates thrombin receptor signaling by increasing the GTPase activity of G␣q (13). One report suggests PKGI can phosphorylate and inhibit the activation of PLC␤3 (14 (17) hyperpolarizes the cell, leading to decreased Ca 2ϩ entry and cellular relaxation. Ca 2ϩ efflux from IP 3 -sensitive intracellular stores also is inhibited by PKGI␤-mediated phosphorylation of the IP 3 receptor-associated cyclic GMP kinase substrate (IRAG) in a complex of sarcoplasmic reticulum membrane proteins, including PKGI␤, IRAG, and the IP 3 receptor (18 -21). The presence of IRAG is essential in the cyclic GMP-dependent inhibition of Ca 2ϩ signaling in colonic SMCs, suggesting that PKGI␤ is a principal regulator of intracellular Ca 2ϩ levels in these cells (19). However, in VSMCs derived from PKGI knock-out mice blood vessels, the transfection of PKGI␣, but not PKGI␤, decreases noradrenaline-induced Ca 2ϩ mobilization (9). Our laboratory has shown that PKGI␣ binds to and phosphorylates RGS2 to terminate PAR-1 thrombin receptor signaling (13), and others have shown that the stable expression of PKGI␣ in CHO cells inhibits thrombin-mediated Ca 2ϩ mobilization in the presence of 8-Br-cGMP (22). However, the role of PKGI␤ was not explored in either of these studies. The relative roles of the two PKGI isozymes, PKGI␣ and PKGI␤, in cyclic GMP-mediated inhibition of Ca 2ϩ transients in VSMCs therefore remain unresolved. In this study, we investigated the relative abilities of PKGI isoforms to inhibit a rise in Ca 2ϩ in response to thrombin receptor-activating ...

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