A patient-designed tissue-engineered model of the infiltrative glioblastoma microenvironment.

Glioblastoma is an aggressive brain cancer characterized by diffuse infiltration. Infiltrated glioma cells persist in the brain post-resection where they interact with glial cells and experience interstitial fluid flow. We use patient-derived glioma stem cells and human glial cells (i.e., astrocytes and microglia) to create a four-component 3D model of this environment informed by resected patient tumors. We examine metrics for invasion, proliferation, and putative stemness in the context of glial cells, fluid forces, and chemotherapies. While the responses are heterogeneous across seven patient-derived lines, interstitial flow significantly increases glioma cell proliferation and stemness while glial cells affect invasion and stemness, potentially related to CCL2 expression and differential activation. In a screen of six drugs, we find in vitro expression of putative stemness marker CD71, but not viability at drug IC50, to predict murine xenograft survival. We posit this patient-informed, infiltrative tumor model as a novel advance toward precision medicine in glioblastoma treatment.

Evidence that the autoimmune antigen myelin basic protein (MBP) Ac1-9 binds towards one end of the major histocompatibility complex (MHC) cleft.

The NH2-terminal peptide of myelin basic protein (MBP) bound to the class II major histocompatibility complex (MHC) protein I-Au is an immunodominant epitope in experimental autoimmune encephalomyelitis, a murine model of multiple sclerosis. However, the MBP-I-Au complex is very unstable. To investigate this, we performed site-directed mutagenesis of the I-Au MHC protein and the MBP peptide. Biochemical, T cell activation, and molecular modeling studies of mutant complexes demonstrate that the MBP peptide's key residue for MHC binding, lysine 4, is buried in the P6 pocket of I-Au, which is predominantly hydrophobic. This implies that the MBP-I-Au complex differs from more stable complexes in two respects: (a) the peptide leaves the NH2-terminal region of the MHC peptide-binding cleft unoccupied; (b) the peptide is not anchored by typical favorable interactions between peptide side chains and MHC pockets. To test these hypotheses, a modified MBP peptide was designed based on molecular modeling, with the aim of producing strong I-Au binding. Extension of the NH2 terminus of MBP with six amino acids from the ova peptide, and replacement of the lysine side chain in the P6 pocket with an aromatic anchor, results in >1,000-fold increased binding stability. These results provide an explanation for the unusual peptide-MHC-binding kinetics of MBP, and should facilitate an understanding of why mice are not tolerant to this self-peptide- MHC complex.

A randomized controlled trial to evaluate the use of the endocervical brush after endocervical curettage.

OBJECTIVE: To determine if using the endocervical brush after curetting the endocervix will increase the yield of endocervical tissue retrieved for an endocervical curettage (ECC) specimen. METHODS: Between March 1, 1995, and June 30, 1996, we recruited for participation patients with abnormal Papanicolaou smears referred for colposcopy. Exclusion criteria were pregnancy, previous hysterectomy, and a history of diethylstilbestrol exposure. Colposcopy and biopsies were performed by residents under direct supervision of the attending staff. Endocervical curettages were performed using the Kevorkian endocervical curette. The subjects were then assigned randomly to one of two ways of collecting the ECC tissue: with either a curette or an endocervical brush. Specimens were reviewed by pathologists, who were blinded to the method of ECC collection. RESULTS: During the study period, 124 patients agreed to participate; 62 were assigned to the control group, and 62 to the study group. Six subjects had missing data, leaving 118 patients available for analysis. In the control group, six of the 58 ECC samples obtained contained insufficient endocervical tissue for pathologic diagnosis. None of the 60 samples from the endocervical brush group was insufficient. The difference between the two groups was statistically significant (P = .01). CONCLUSION: The addition of the endocervical brush to endocervical tissue sampling at colposcopy in the study decreased the number of insufficient samples. The endocervical brush method of collection of an ECC specimen from the canal after the Kevorkian curette is used is a valuable addition to this diagnostic tool. We recommend its use in obtaining an ECC specimen.

Novel genetic regulation of T helper 1 (Th1)/Th2 cytokine production and encephalitogenicity in inbred mouse strains.

Development of T helper cell (Th)1 or Th2 cytokine responses is essential for effector and regulatory functions of T helper cells. We have compared cytokine profiles of myelin basic protein (MBP) Ac1-16 peptide-specific T helper cells from inbred mouse strains expressing identical k haplotype-derived MHC class II molecules B10.A and B10.BR, B10.BR T cell lines (TCL) produced Th1 cytokines (including high levels of TNF-alpha) and induced experimental autoimmune encephalomyelitis after adoptive transfer. In contrast, B10.A TCL produced Th2 cytokines (including low levels of TNF-alpha) and were poorly encephalitogenic. The contributions of the genetic origin of the T cells and the APC were explored. Serial restimulations of the B10.BR TCL with B10.A or (B10.A x B10.BR) F1 splenic antigen presenting cells (APC) during the establishment of TCL markedly reduced both Th1 cytokine production and encephalitogenicity. In addition, a single restimulation with B10. A splenic APC reduced IFN-gamma and TNF-alpha production by established Th1 MBP-specific Ak-restricted B10.BR TCL and by a Th1 KLH-specific, Ek-restricted B10.BR T cell clone. These studies suggest that B10.A and B10.BR APC differ in their ability to stimulate IFN-gamma and TNF-alpha production by mature Th1 cells and also influence their Th1/Th2 commitment in vivo. The nature of the downregulatory activity of B10.A APC on IFN-gamma and TNF-alpha production was explored. 2-hour supernatants from antigen-activated B10.A APC/TCL cultures or from B10.A APC activated by LPS had the same inhibitory effects on IFN-gamma and TNF-alpha production by B10.BR TCL. The downregulatory effects of B10.A APC are independent of TNF-alpha, IL-4, IL-10, IL-12p40, IFN-gamma, IL-13, TGF-beta, and PGE2. Thus, genetic difference(s) between B10.A and B10.BR APC appear(s) to control the production or activity of a novel soluble cytokine regulatory factor that influences Th1/Th2 commitment and controls production of IFN-gamma and TNF-alpha by mature Th1 cells.

A sensitive ELISPOT assay to detect low-frequency human T lymphocytes.

We extended the sensitivity of the ELISPOT assay by including an antigen-driven proliferation step prior to a final restimulation with antigen and irradiated antigen presenting cells (APCs). This improved sensitivity made the modified ELISPOT assay better suited to the detection of rare or low frequency T lymphocytes than the standard ELISPOT assay or alternatives such as limiting dilution analysis or in situ hybridization. Use of ELISA-grade plastic or polyvinylidene difluoride (PVDF) plates for the detection of different cytokines improved the signal-to-noise ratio for counting cytokine spots, and use of video computer imaging software improved objective quantitation. Analysis of antigen-reactive peripheral blood mononuclear cells (PBMC) from multiple sclerosis (MS) patients using both the traditional and our modified ELISPOT assay demonstrate a > 10-fold increase in numbers of myelin basic protein (MBP)-responsive T cells detected (an average of less than 1 spot forming cell (SFC) per 2 x 10(5) PBMC with the standard assay compared to 19 SFC per 2 x 10(5) PBMC with the modified assay). In addition, the modified ELISPOT assay could be performed with frozen PBMC, which permitted greater flexibility in sample processing, multiple use of a single sample as an internal standard, and simultaneous analysis of samples collected at different time points. This modified ELISPOT assay has many applications, including analysis of cytokine profiles in rare T cell populations, identification of antigen-responsive individuals as PBMC donors for T lymphocyte cloning or for therapeutic intervention, and assessment of vaccine or therapeutic efficacy as a surrogate clinical marker.

Interactions among polymorphic and conserved residues in MHC class II proteins affect MHC-peptide conformation and T cell recognition.

The structural basis for MHC-restricted T cell recognition of the N-terminal peptide of myelin basic protein (MBP Ac1-11) presented by two mouse class II alleles, Ak and Au, was examined, focusing on the roles of A beta chain polymorphic residues 38 beta (in the beta sheet) and 61 beta (in the alpha helix) in controlling the responses of panels of Ak- and Au-restricted T cell hybridomas. Despite the conservative nature of the substitutions at 38 beta (k = Val, u = Leu) and 61 beta (k = Trp, u = Tyr), transfectants expressing Ak or Au proteins carrying allelic substitutions at 38 beta and/or 61 beta gave dramatically reduced T cell responses. The modest reduction in peptide binding detected using a biotinylated MBP peptide analog appear insufficient to explain the reduced responses, suggesting that changes at 38,61 beta create conformational changes in the MHC-peptide complex. The impact of allelic substitutions at 38,61 beta on T cell responses is also modulated by other residues differing between Ak and Au. To explore the structural basis for these phenomena, protein models were developed of the Ak, Au and 38,61 beta mutant proteins using self-consistent ensemble optimization methodologies. Substitutions of the alternative allelic residue at 38 beta and/or 61 beta, which are in van der Waals contact, change the configuration of this region of the peptide-binding groove, and potentially might affect the conformation of the bound peptide and its hydrogen-bonding to residue 61 beta. The models predict that this region of the groove is markedly altered by allelic differences at A beta residue 9 beta (k = His, u = Val) which determine the position of the side-chain of Tyr30 beta, adjacent to residues 38 beta and 61 beta. Thus, interactions among polymorphic and conserved residues control the antigen presentations functions of MHC class II proteins.

Expression of three human beta-adrenergic-receptor subtypes in transfected Chinese hamster ovary cells.

The genes coding for three pharmacologically distinct subtypes of human beta-adrenergic receptors (beta 1 AR, beta 2 AR and beta 3 AR) were transfected for expression in Chinese hamster ovary (CHO) cells. Stable cell lines expressing each receptor were analyzed by ligand binding, adenylate cyclase activation and photoaffinity labeling, and compared to beta AR subtypes observed in previously described tissues, primary cultures and transfected cell lines. Each of the three receptor subtypes displayed saturable [125I]iodocyanopindolol-binding activity. They showed the characteristic rank order of potencies for five agonists, determined by measuring the accumulation of intracellular cAMP. These recombinant cell lines express a homogeneous population of receptors and display the known pharmacological properties of beta 1 AR and beta 2 AR, in human tissues. It is therefore likely that the pattern of ligand binding and adenylate cyclase activation, mediated by the new beta 3 AR in CHO cells, also reflects the yet-undetermined pharmacological profile in humans.

Mammalian cell transient expression of tissue factor for the production of antigen.

We describe a mammalian cell expression system used to rapidly produce microgram quantities of a membrane protein used as an immunogen. A fusion protein expression vector was constructed which contained the signal sequence and 27 amino acids of the Herpes simplex virus glycoprotein D (gD), followed by a factor VIII (fVIII) thrombin cleavage site and the mature tissue factor (TF) sequence. This fusion protein was transiently expressed and then purified using an antibody to gD. The purified fusion protein, gDTF, was incubated with thrombin to remove the gD-fVIII moiety and the resulting rTF served as antigen for the generation of TF-specific antibodies. The antibodies produced were then used for a comparison of the turnover rates of the constitutively and transiently produced fusion protein. In addition, sensitivity to glycosidases indicated that the transiently and constitutively produced recombinant proteins do not contain identical carbohydrate structures.

Purification of recombinant human tissue factor.

Tissue factor (TF) is a 263 amino acid membrane-bound procoagulant protein that serves as a cofactor for the serine protease factor VII (fVII). Recombinant human TF (rTF) produced in both human kidney 293 cells and Escherichia coli has been immunoaffinity purified by using a TF-specific monoclonal antibody. Recombinant TF produced in 293 cells is glycosylated and migrates on reducing SDS-PAGE with an apparent molecular weight (Mr) of 45K. Some interchain disulfide-bonded rTF dimers are observed under nonreducing conditions. The E. coli produced rTF has a molecular weight of 33K and 35K, with the 33K band missing nine amino acids at the carboxy terminus. Although the E. coli produced rTF does not contain any carbohydrate, it is fully functional in both a chromogenic assay and a one-stage prothrombin time assay. A variant has been constructed wherein the cytoplasmic cysteine (residue 245) has been mutagenized to a serine residue. The amount of disulfide-linked aggregates is dramatically reduced following immunoaffinity purification of this four-cysteine variant (C2455), which is active in the chromogenic and prothrombin time assays.

Factor VIII-bypassing activity of bovine tissue factor using the canine hemophilic model.

The bleeding disorder of hemophilia A currently treated by replacement therapy of the missing coagulation factor, factor VIII, is frequently complicated by the development of neutralizing antibodies. The therapeutic potential of attenuated forms of the lipid-associated glycoprotein tissue factor, a known initiator of coagulation, was investigated as a factor VIII-by-passing activity. The protein moiety of tissue factor (Apo-TF) was partially purified and exhibited minimal procoagulant activity before relipidation in vitro. In pilot studies, Apo-TF injection into rabbits previously anticoagulated with an antibody to factor VIII was found to have a procoagulant effect. The efficacy of the material was further demonstrated when injection of Apo-TF in hemophilic dogs resulted in a normalization of the cuticle bleeding time. Little or no change in the blood parameters associated with disseminated intravascular coagulation was observed at lower doses, although mild to moderate effects were seen at higher doses. These data suggest a novel role for Apo-TF preparations as a potential therapeutic agent for hemophiliacs with antibodies to factor VIII once the potential thrombogenicity of such materials is evaluated.

Functional role of proteolytic cleavage at arginine-275 of human tissue plasminogen activator as assessed by site-directed mutagenesis.

Activation of the zymogen form of a serine protease is associated with a conformational change that follows proteolysis at a specific site. Tissue-type plasminogen activator (t-PA) is homologous to mammalian serine proteases and contains an apparent activation cleavage site at arginine-275. To clarify the functional consequences of cleavage at arginine-275 of t-PA, site-specific mutagenesis was performed to convert arginine-275 to a glutamic acid. The mutant enzyme (designated Arg-275----Glu t-PA) could be converted to the two-chain form by Staphylococcus aureus V8 protease but not by plasmin. The one-chain form was 8 times less active against the tripeptide substrate H-D-isoleucyl-L-prolyl-L-arginine-p-nitroanilide (S-2288), and the ability of the enzyme to activate plasminogen in the absence of fibrinogen was reduced 20-50 times compared to the two-chain form. In contrast, one-chain Arg-275----Glu t-PA has equal activity to the two-chain form when assayed in the presence of physiological levels of fibrinogen and plasminogen. Fibrin bound significantly more of the one-chain form of t-PA than the two-chain form for both the wild-type and mutated enzymes. One- and two-chain forms of the wild-type and mutated plasminogen activators slowly formed complexes with plasma protease inhibitors, although the one-chain forms showed decreased complex formation with alpha 2-macroglobulin. The one-chain form of t-PA therefore is fully functional under physiologic conditions and has an increased fibrin binding compared to the two-chain form.