Implementation of a Patient Specific QA Protocol for a Novel Dedicated Stereotactic Radiosurgery Linear Accelerator

PURPOSE/OBJECTIVE(S)

To describe the patient specific QA (Quality Assurance) protocol implemented for plan integrity verification, in stereotactic radiosurgery (SRS) and radiotherapy (SRT) treatments performed on a novel dedicated frameless image guided radiosurgery system using conical collimator, and a combination of yoked gimbals to cover near2pi solid angle. Startup and commissioning results obtained for planned vs measured dose distributions with several detectors are presented.

MATERIALS/METHODS

The patient specific QA protocol includes: A) Review of the approved plan based on AAPM TG 275 report recommendations B) 1D verification using small volume ionization chambers inside an anthropomorphic head phantom C) 2D dose verification of a coronal and sagittal dose plan performed with high resolution 2D Array and respective phantom apparatus D) In-house independent MU (Monitor Unit) calculation using the same formalism of the vendor TPS (Treatment Planning Systems) RayTracing dose-calculation algorithm E) Monte Carlo based secondary dose check & plan QA. A retrospective analysis of the results of the first 15 patients treated is presented, focusing on plan complexity vs QA results.

RESULTS

The 1D results obtained for the 15 SRS plans were within ±5% for all reported cases, with a mean percent difference of -1,25%, confirming an overall good agreement and, as expected, a partial volume effect in plans with smaller collimators. For the 2D dose verifications, with a 10% dose threshold, gamma passing rates of 97,5% (coronal) and 96,78 (sagittal) with 3% 1mm criteria, 95,1% (coronal) and 94,3% (sagittal) for 2% 1 mm criteria and 90,7% (coronal) and 90,0% (sagittal) for 1% 1mm criteria were obtained. Moreover, the results showed a correlation between lesion volume or number of collimators used with gamma passing rates. All MU verification results were within ±0,3% and provides an efficient risk mitigation approach for this new delivery technique.

CONCLUSION

The verification results of the first 15 treated SRS plans confirmed point dose and planar measurements in agreement with TPS calculations, with superior results for planes with smaller lesions and fewer collimators. This also represents an integral validation of the image-based alignment system and fine treatment couch movements, as treatments are intrinsically multi-isocentric.

Accuracy comparison of several common implicit solvent models and their implementations in the context of protein-ligand binding

In this study several commonly used implicit solvent models are compared with respect to their accuracy of estimating solvation energies of small molecules and proteins, as well as desolvation penalty in protein-ligand binding. The test set consists of 19 small proteins, 104 small molecules, and 15 protein-ligand complexes. We compared predicted hydration energies of small molecules with their experimental values; the results of the solvation and desolvation energy calculations for small molecules, proteins and protein-ligand complexes in water were also compared with Thermodynamic Integration calculations based on TIP3P water model and Amber12 force field. The following implicit solvent (water) models considered here are: PCM (Polarized Continuum Model implemented in DISOLV and MCBHSOLV programs), GB (Generalized Born method implemented in DISOLV program, S-GB, and GBNSR6 stand-alone version), COSMO (COnductor-like Screening Model implemented in the DISOLV program and the MOPAC package) and the Poisson-Boltzmann model (implemented in the APBS program). Different parameterizations of the molecules were examined: we compared MMFF94 force field, Amber12 force field and the quantum-chemical semi-empirical PM7 method implemented in the MOPAC package. For small molecules, all of the implicit solvent models tested here yield high correlation coefficients (0.87-0.93) between the calculated solvation energies and the experimental values of hydration energies. For small molecules high correlation (0.82-0.97) with the explicit solvent energies is seen as well. On the other hand, estimated protein solvation energies and protein-ligand binding desolvation energies show substantial discrepancy (up to 10kcal/mol) with the explicit solvent reference. The correlation of polar protein solvation energies and protein-ligand desolvation energies with the corresponding explicit solvent results is 0.65-0.99 and 0.76-0.96 respectively, though this difference in correlations is caused more by different parameterization and less by methods and indicates the need for further improvement of implicit solvent models parameterization. Within the same parameterization, various implicit methods give practically the same correlation with results obtained in explicit solvent model for ligands and proteins: e.g. correlation values of polar ligand solvation energies and the corresponding energies in the frame of explicit solvent were 0.953-0.966 for the APBS program, the GBNSR6 program and all models used in the DISOLV program. The DISOLV program proved to be on a par with the other used programs in the case of proteins and ligands solvation energy calculation. However, the solution of the Poisson-Boltzmann equation (APBS program) and Generalized Born method (implemented in the GBNSR6 program) proved to be the most accurate in calculating the desolvation energies of complexes.

Inhibition of TGFBIp expression reduces lymphangiogenesis and tumor metastasis

Transforming growth factor-β-induced protein (TGFBIp) is an extracellular matrix protein that has a role in a wide range of pathological conditions. However, the role of TGFBIp signaling in lymphangiogenesis is poorly understood. The purpose of this study was therefore to analyze the effects of TGFBIp on lymphangiogenesis and determine whether TGFBIp-related lymphangiogenesis is important for the metastasis of tumor cells. TGFBIp increased adhesion, migration, and morphologic differentiation of human lymphatic endothelial cells (LECs), consistent with an increase in lymphatic vessel sprouting in a three-dimensional lymphatic ring assay. TGFBIp also induced phosphorylation of intracellular signaling molecules SRC, FAK, AKT, JNK and ERK. TGFBIp-induced lymphatic vessel sprouting was inhibited by addition of anti-integrin β3 antibody and pharmacologic inhibitors of FAK, AKT, JNK or ERK. TGFBIp increased both CCL21 expression in LECs, a chemokine that actively recruits tumor cells expressing the cognate chemokine receptors to lymphatic vessels and LEC permeability by inducing the dissociation of VE-cadherin junctions between LECs via the activation of SRC signaling. In vivo, inhibition of TGFBIp expression in SW620 cancer cells dramatically reduced tumor lymphangiogenesis and metastasis. Collectively, our findings demonstrate that TGFBIp is a lymphangiogenic factor contributing to tumor dissemination and represents a potential target to inhibit metastasis.

Transgene-enforced co-stimulation of CD4+ T cells leads to enhanced and sustained anti-tumor effector functioning

Background The role of co-stimulation in CD4+ T cell activation by professional APC is well established, while less is known of the role co-stimulation plays when CD4+ T cells interact directly with tumor cells. Methods Through genetic engineering of human CD4+ T cells, we tested the hypothesis that integration of co-stimulatory signaling domains within a tumor-targeting chimeric Ag receptor (CAR), the IL-13Ralpha2-specific IL-13-zetakine (IL13zeta), would enhance CD4+ T cell mediated responses against tumors that fail to express ligands for co-stimulatory receptors. Results Compared with CD3zeta-mediated activation alone, CD4+ effector T cells expressing the IL13-CD28-41BBzeta CAR exhibited augmented/sustained MAPK and AKT activity, up-regulated Th1 cytokine production, and enhanced cytolytic potency against tumor targets. Moreover, upon recursive stimulation with tumor, the IL13-CD28-41BBzeta+ cells retained/recycled their lytic function, whereas IL-13zeta+ CD4+ cells became anergic/exhausted. These in vitro observations correlated with enhanced in vivo control of established orthotopic CNS glioma xenografts in immunodeficient mice mediated by adoptively transferred ex vivo-expanded CD4+ T cells expressing the co-stimulatory CAR. Discussion Together these studies demonstrate the importance of integrating co-stimulation with CD3zeta signaling events to activate fully CD4+ anti-tumor effector cells for sustained function in the tumor microenvironment.

Conversion of a tumor-binding peptide identified by phage display to a functional chimeric T cell antigen receptor

Adoptive transfer of ex vivo expanded tumor-specific T cells is a promising therapeutic modality for promoting or augmenting antitumor immunity. Several groups, including ours, are developing antigen receptor gene transfer strategies as a means of generating effector cells for adoptive therapy. Chimeric antigen receptors (CARs) have been described that use single-chain antibodies or cytokine ligands as tumor targeting domains. Here, we describe the capacity of a tumor-binding peptide identified by phage display combinatorial library screening to serve as a CAR targeting domain. A phage library-selected high-affinity 12-mer peptide (Bpep) specific for alpha(v) beta(6) integrin (alpha v beta6) was chosen for these studies. Primary human T cells were genetically modified to express the Bpep-CAR consisting of an alpha v beta6-specific peptide and human IgG4 hinge-Fc extracellular domain fused to the cytoplasmic tail of CD3-zeta. T cell expression of the Bpep-CAR was assessed by Western blot analysis, and trafficking of the Bpep-CAR to the cell surface was demonstrated by flow cytometry. Functionally, Bpep-CAR redirected cytotoxic T lymphocytes specifically kill integrin alpha v beta6+ ovarian tumor targets, and are activated for interferon gamma secretion. Our data suggest that large new repertoires of tumor-specific T cell antigen receptor transgenes might be available through merging combinatorial peptide libraries with CAR construct design.

Differences in the incidence of apoptosis between in vivo and in vitro produced blastocysts of farm animal species: a comparative study

The occurrence of pregnancies and births after embryo transfer (ET) of in vivo produced embryos is generally more successful compared to that of embryos produced in vitro. This difference in ET success has been observed when embryos of morphological equal (high) quality were used. The incidence of apoptosis has been suggested as an additional criterion to morphological embryo evaluation in order to assess embryo quality and effectively predict embryo viability. In this study, equine, porcine, ovine, caprine and bovine in vivo and in vitro produced morphologically selected high quality (grade-I) blastocysts were compared for the occurrence of apoptosis in blastomeres. The total number of cells per embryo and the number of cells with damaged plasma membranes, fragmented DNA and fragmented nuclei per embryo were assessed in selected blastocysts by combining Ethidium homodimer (EthD-1), terminal dUTP nick end labeling (TUNEL) and Hoechst 33342 staining. In general, the level of blastomere apoptosis was low. A higher level of apoptosis was observed in in vitro produced equine, porcine and bovine blastocysts compared to their in vivo counterparts. Interestingly, 4 of the initially selected 29 bovine in vitro produced blastocysts exhibited extensive signs of apoptosis affecting the inner cell mass (ICM), which is not compatible with a viable conceptus. Repeated occurrence of this observation may explain the lower ET outcome of in vitro produced bovine embryos compared to in vivo produced embryos. It is concluded that, although in morphologically high quality blastocysts of several farm animal species a significant difference exists in the percentages of apoptotic cells between in vivo and in vitro produced embryos, the incidence of apoptosis at the blastocyst stage is at such a low level that it cannot reflect the substantial differences in embryo viability that have been described between in vivo and in vitro produced blastocysts following ET.

Ultrastructural characteristics of fresh and frozen-thawed ovine embryos using two cryoprotectants

Cryopreservation of sheep embryos with ethylene glycol as a protectant appears to be more effective than glycerol, particularly at the morula stage, as has been demonstrated on the basis of in vitro and in vivo development rates after thawing. In this study we compare the ultrastructure of fresh morulae, thawed morulae, and blastocysts cryopreserved with either ethylene glycol or glycerol at the electron microscopic level, to look for cellular damage that could be responsible for proven differences in embryo survival after transfer. Embryos cryopreserved with glycerol showed unequal degrees of conservation even among blastomeres within a single embryo. In morulae, inner blastomeres were completely damaged, whereas external ones appeared to be intact. Both morulae and blastocysts cryopreserved with ethylene glycol showed a higher uniformity in blastomere conservation than embryos with glycerol. The most remarkable features in this experimental group were the presence of desmosomes following tight junctions between blastomeres and the presence of many microvilli on the outer surface of external blastomeres. These characteristics are similar in fresh embryos of the control group. Our results show that ethylene glycol protects membrane and cytoplasmic structures of embryonic cells from cryoinjury much better than glycerol. In vivo survival of embryos confirmed the ultrastructural observations. A limited permeability of glycerol would explain the observed ultrastructural differences in blastomere integrity, which depends on blastomere location and the differences between morulae and blastocysts. We conclude that the low reproductive yield after cryopreservation using glycerol can be attributed to the lack of protection of inner cells.

Relationship quality of aggressive children and their siblings: a multiinformant, multimeasure investigation

Sibling influence on the learning and enactment of aggressive behavior has been consistently demonstrated in studies of sibling relationships. Available evidence suggests that, compared with nonaggressive children's sibling interactions, the sibling interactions of aggressive children are marked by more frequent, intense, and prolonged aggressive behaviors. Although research on normative and aggressive children's sibling interactions has increased recently, a number of limitations in this literature were addressed in this study by: (1) including both an aggressive and nonaggressive comparison group, (2) examining both positive and negative features of sibling relationships, (3) employing a multimethod/multiinformant approach to data collection, and (4) utilizing an improved self-report method. In support of our hypotheses and consistent with previous research, results showed that aggressive children's sibling relationships were marked by higher levels of observed conflict and lower levels of self-reported positive features. When gender was examined, results showed that older brother/younger sister dyads were characterized by higher levels of negative features and lower levels of positive features.

Binding of a surface protein of Staphylococcus aureus to cultured ovine mammary gland epithelial cells

Staphylococcus aureus is the most persistent pathogen causing ovine mastitis. This study investigated S. aureus binding to cultured epithelial cells obtained from the mammary gland. A staphylococcal 145kDa cell wall adhesin, originally isolated from a bovine mastitis strain, was detected in lysostaphin-solubilized ovine mastitis strains and in the encapsulated strain A. This adhesin was able to bind to cultured ovine mammary gland epithelial cells (MGEC) and to a rat intestinal epithelial cell line (RIE-1), exhibiting different electrophoretic mobilities that could be attributable to protein polymorphism. Inhibition assays using antibodies against 145kDa adhesin and against whole bacteria showed the specificity of the binding to cells. The role of this protein in adherence was assessed by adherence inhibition tests carried out in vitro with radiolabeled bacteria and cultured epithelial cells. Preincubation of bacteria with antibodies against adhesin 145kDa or against strain c195 resulted in a statistically significant decrease of adherence. These experiments suggest that adherence of S. aureus to MGEC may be critical for colonization.

Effect of slime on adherence of Staphylococcus aureus isolated from bovine and ovine mastitis

The interactions between slime, Staphylococcus aureus and ovine mammary gland epithelial cells (MGEC) were studied in vitro. Suspensions of radiolabelled bacteria incubated with slime significantly increased the ability of S. aureus strains to adhere to a filter. When suspensions of radiolabelled bacteria were incubated with MGEC treated with trypsin, the ability of slime to improve S. aureus adherence was also shown, indicating that it was not dependent on cell membrane proteins. The interaction of radiolabelled bacteria with slime prior to the adherence test with MGEC demonstrated that the adherence process requires the interaction between slime and bacteria. This interaction is inhibited by anti-slime antibodies. This study provides evidence that a specific interaction between bacteria coated with slime and MGEC could be a critical part of mammary gland infection.

Distinguishing the early-onset/persistent and adolescence-onset antisocial behavior types: from birth to 16 years

Moffitt's theory regarding two types of adolescent antisocial behavior was investigated using a prospective, longitudinal study of normal and abnormal development in a primarily low socioeconomic status, ethnically diverse sample. Results supported the presence of an early-onset/persistent (EOP) group and an adolescence-onset (AO) group. Groups were most reliably and significantly distinguished by indices of socioemotional history within the first 3 years, but no significant differences were found on early measures of temperament or neuropsychological functioning. EOPs scored significantly lower than other groups on measures of neuropsychological functioning only during late childhood and adolescence, suggesting that the declines in verbal functioning that have been so reliably found in this and other samples of early-starting antisocial adolescents are progressive and consequent to adverse experience. In adolescence, AOs were significantly more likely to report high levels of internalizing symptoms and life stress, suggesting that AO antisocial behavior is not a benign phenomenon. Implications of these findings for etiologic theories of adolescent antisocial behavior are discussed.

Enhancement of resistance in mice treated with Lactobacillus casei: effect on Trichinella spiralis infection

The ability of viable Lactobacillus casei, administered by an intraperitoneal route, to induce resistance in mice against Trichinella spiralis infection was tested. The percent reduction of adult worms in the intestine 5 days after T. spiralis infection observed in L. casei-treated animals, compared with those of the control group, fluctuated between 70.9 and 88.5%; reductions of larvae per gram of muscle tissue, evaluated at 30 days after infection, varied from 46.6 to 84.4% in L. casei-treated mice compared with controls. At 5 days after infection, intestinal villus height was shorter in T. spiralis-infected animals than in L. casei-treated or uninfected mice. There were fewer mast cells/crypt unit in L. casei-treated and uninfected mice than in T. spiralis-infected animals. Lactobacilli-treated mice showed twice as many mononuclear cells/crypt unit as T. spiralis-infected animals. The IFN-gamma serum level was higher in L. casei-treated animals at the time of worm challenge as compared with T. spiralis-infected or uninfected mice. The results indicate that: (1) L. casei increased resistance that acted against T. spiralis infection in mice, (2) this resistance apparently was directed against adult worms in the intestine.

A generic method for the production of cell lines expressing high levels of 7-transmembrane receptors

G-protein-coupled or 7-transmembrane receptors (7TMRs) are often studied after heterologous expression in mammalian cells such as COS-7, CHO-K1, or HEK-293s. In this paper, we describe the development of a rapid and generic method for producing stable Chinese hamster ovary cell lines expressing high levels of recombinant 7TMRs by N-terminal tagging these proteins with the hemagglutinin (HA) sequence. To illustrate the broad applicability of this technique, we have presented data from cell lines expressing a glycoprotein hormone receptor for follicle-stimulating hormone (FSHR), CXC- (CXCR-2), and CC-chemokine (CCR-1) receptors and peptide receptors from the somatostatin (SSTR1, 2, 5) and neuropeptide Y (NPY-Y2, -Y4 Rs) families. Typically, cell lines with a receptor density of 1 to 15 pmol/mg protein are produced with this method. The presence of the HA tag does not adversely affect the binding or functional activity of the receptors.

Differential stability of HLA-DR alleles independent of endogenous peptides

Purified HLA DRB1*0101 was shown to be inherently more stable to dissociation than DRB1*0401. The residues responsible for the differential stability were defined by constructing hybrid molecules, which contained a small number of residues from DRB1*0101 substituted into the framework of DRB1*0401. One of the hybrid molecules, containing six substituted amino acids, was as stable as DRB1*0101, but exhibited the binding specificity of DRB1*0401. This result indicated that the differential stability between the alleles arose from structural differences, and was not due solely to varying populations of endogenous peptides.

Differential stability of HLA-DR alleles independent of endogenous peptides

Purified HLA DRB1*0101 was shown to be inherently more stable to dissociation than DRB1*0401. The residues responsible for the differential stability were defined by constructing hybrid molecules, which contained a small number of residues from DRB1*0101 substituted into the framework of DRB1*0401. One of the hybrid molecules, containing six substituted amino acids, was as stable as DRB1*0101, but exhibited the binding specificity of DRB1*0401. This result indicated that the differential stability between the alleles arose from structural differences, and was not due solely to varying populations of endogenous peptides.

Role of the polymorphic residues in HLA-DR molecules in allele-specific binding of peptide ligands

Analysis of peptide binding to a set of HLA-DR alleles has allowed the proteins to be segregated into functional subsets, depending on the amino acids at positions 57 and 86 of the beta-chain. DR proteins with glycine at 86 beta and aspartic acid at 57 beta bound a simplified peptide with significantly lower IC50 values than alleles that did not have this combination of amino acids. The size of the amino acid at 86 beta seemed to modify the steric requirements for the single most important side chain of the peptide. Within each of the four subgroups, other polymorphic amino acids define allele-specific binding requirements. These were explored by analyzing the ability of eight different DR alleles to bind 13 known T cell determinants. The side chains in the peptides that seemed to be responsible for allele specificity were determined by correlating their common structural features with complementary polymorphic residues in the binding site. The importance of these residues was tested by incorporating them into a polyalanine backbone, and was confirmed by the ability of these residues to transfer allele specificity to these simplified analogues. Even though polymorphic contacts affected peptide affinity, the majority of the free energy of binding in all cases arose from interactions with the peptide backbone and the single hydrophobic amino acid at the third position. These constraints seem to orient all peptides in a similar location, forcing them to adopt a closely related conformation in the binding site. The corresponding side chain in each peptide contacts the same pocket in the binding site, regardless of the allele. This apparent similarity should allow any DR allele to be analyzed by extrapolation from the DR1 crystal structure.

Role of the polymorphic residues in HLA-DR molecules in allele-specific binding of peptide ligands

Analysis of peptide binding to a set of HLA-DR alleles has allowed the proteins to be segregated into functional subsets, depending on the amino acids at positions 57 and 86 of the beta-chain. DR proteins with glycine at 86 beta and aspartic acid at 57 beta bound a simplified peptide with significantly lower IC50 values than alleles that did not have this combination of amino acids. The size of the amino acid at 86 beta seemed to modify the steric requirements for the single most important side chain of the peptide. Within each of the four subgroups, other polymorphic amino acids define allele-specific binding requirements. These were explored by analyzing the ability of eight different DR alleles to bind 13 known T cell determinants. The side chains in the peptides that seemed to be responsible for allele specificity were determined by correlating their common structural features with complementary polymorphic residues in the binding site. The importance of these residues was tested by incorporating them into a polyalanine backbone, and was confirmed by the ability of these residues to transfer allele specificity to these simplified analogues. Even though polymorphic contacts affected peptide affinity, the majority of the free energy of binding in all cases arose from interactions with the peptide backbone and the single hydrophobic amino acid at the third position. These constraints seem to orient all peptides in a similar location, forcing them to adopt a closely related conformation in the binding site. The corresponding side chain in each peptide contacts the same pocket in the binding site, regardless of the allele. This apparent similarity should allow any DR allele to be analyzed by extrapolation from the DR1 crystal structure.

Adherence of ruminant mastitis Staphylococcus aureus strains to epithelial cells from ovine mammary gland primary cultures and from a rat intestinal cell line

Staphylococcus aureus isolated from mastitis (14 bovine and 11 ovine strains) exhibited an ability to adhere to epithelial primary cultures from ovine mammary gland and to a rat epithelial cell line, RIE-1. Strain differences in the degree of adherence were observed in both cases. These differences were maintained when comparing different epithelial sources (rat vs. ovine). RIE-1 cells can thus be used as a model for studying staphylococcal adherence to epithelial cells. Changes in bacterial adherence were observed according to the bacterial growth phase. The magnitude of these changes differed among strains. Bacterial cell surface hydrophobicity was not related to the degree of adherence to mammalian epithelial cells.

An efficient microtest to study adherence of bacteria to mammalian cells

A simple, fast and highly reproducible microtest was developed for in vitro adherence studies. A rat epithelial cell line was investigated for the adherence of clinical and subclinical ovine and bovine Staphylococcus aureus strains isolated from mastitis. Staphylococcus aureus strains differed in their ability to adhere to epithelial cells, the degree of adherence being dependent on the concentration of bacteria used in the test.

Factors influencing the degree of in vitro bacterial adhesion to ovine mammary gland epithelial cells

Bacterial adhesion to mammary gland epithelial cells (EC) may play a role in the pathogenesis of mastitis. In vitro adherence systems have been developed to study mastitis in cattle but little has been done in sheep. In this work, a method is described for obtaining mammary gland cell preparations containing greater than or equal to 65% EC from live or dead ewes, using a Ficoll-Hypaque flotation method (cell viability = 70-90%). An in vitro adhesion assay procedure was also developed to study the interaction between EC and ovine mastitis bacterial strains. It was observed that, under the test conditions, adherence increased as the incubation time was prolonged from 30 to 120 min (P less than 0.05). Adhesion was greater at incubation temperature of 37 degrees C than at 22 degrees C (P less than 0.001). An acidic pH (5.9) was associated with an increase in adhesion, when compared with a higher pH (7.2; P less than 0.05). Tween 20, Tween 80 and bovine serum albumin helped to eliminate a background of unbound bacteria from the test slides, but they also inhibited adhesion to some strains. Strain differences in adhesion and in ability to form a background were also observed. Some of these findings may have in vivo implications.