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Biomedical subjects

L M Weiner

Publications and source records attributed to L M Weiner.

At least 19 recordsLinked to original sources
PubMed2005

Synthesis and evaluation of peptidic metal chelators for neuroprotection in neurodegenerative diseases.

A series of novel derivatives of neuropeptides with a metal-chelating moiety was synthesized and examined for various properties related to iron (Fe) chelation and neuroprotective action. All derivatives chelated Fe to form stable Fe complexes in water. Some strongly inhibited Fe-induced lipid peroxidation with an IC(50) value of about 12 microm. In PC12 cell culture, several compounds, at concentrations as low as 1 microm, attenuated serum-free stimulated cell death and improved cell survival by 20-35%. At this concentration, these analogs also protected against 6-hydroxydopamine (6-OHDA)-induced cell death, increasing cell viability by 20-30%. Electron paramagnetic resonance (EPR) studies indicated that besides being good Fe chelators, these analogs act as radical scavengers to directly scavenge hydroxyl radicals. Together, the data indicate that some of the analogs could be further developed as possible neuroprotective agents for treatment of neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington's diseases, Friedreich's atxia, amyotrophic, and lateral sclerosis where Fe misregulation has been reported.

Animals↗
PubMed2001

A structural motif of acetylcholinesterase that promotes amyloid beta-peptide fibril formation.

Acetylcholinesterase (AChE) has been found to be associated with the core of senile plaques. We have shown that AChE interacts with the amyloid beta-peptide (Abeta) and promotes amyloid fibril formation by a hydrophobic environment close to the peripheral anionic binding site (PAS) of the enzyme. Here we present evidence for the structural motif of AChE involved in this interaction. First, we modeled the docking of Abeta onto the structure of Torpedo californica AChE, and identified four potential sites for AChE-Abeta complex formation. One of these, Site I, spans a major hydrophobic sequence exposed on the surface of AChE, which had been previously shown to interact with liposomes [Shin et al. (1996) Protein Sci. 5, 42-51]. Second, we examined several AChE-derived peptides and found that a synthetic 35-residue peptide corresponding to the above hydrophobic sequence was able to promote amyloid formation. We also studied the ability to promote amyloid formation of two synthetic 24-residue peptides derived from the sequence of a Omega-loop, which has been suggested as an AChE-Abeta interacting motif. Kinetic analyses indicate that only the 35-residue hydrophobic peptide mimics the effect of intact AChE on amyloid formation. Moreover, RP-HPLC analysis revealed that the 35-residue peptide was incorporated into the growing Abeta-fibrils. Finally, fluorescence binding studies showed that this peptide binds Abeta with a K(d) = 184 microM, independent of salt concentration, indicating that the interaction is primarily hydrophobic. Our results indicate that the homologous human AChE motif is capable of accelerating Abeta fibrillogenesis.

Acetylcholinesterase↗
PubMed2001

High affinity restricts the localization and tumor penetration of single-chain fv antibody molecules.

Antitumor monoclonal antibodies must bind to tumor antigens with high affinity to achieve durable tumor retention. This has spurred efforts to generate high affinity antibodies for use in cancer therapy. However, it has been hypothesized that very high affinity interactions between antibodies and tumor antigens may impair efficient tumor penetration of the monoclonal antibodies and thus diminish effective in vivo targeting (K. Fujimori et al., J. Nucl. Med., 31: 1191-1198, 1990). Here we show that intrinsic affinity properties regulate the quantitative delivery of antitumor single-chain Fv (scFv) molecules to solid tumors and the penetration of scFv from the vasculature into tumor masses. In biodistribution studies examining a series of radioiodinated scFv mutants with affinities ranging from 10(-7)-10(-11) M, quantitative tumor retention did not significantly increase with enhancements in affinity beyond 10(-9) M. Similar distribution patterns were observed when the scFv were evaluated in the absence of renal clearance in anephric mice, indicating that the rapid renal clearance of the scFv was not responsible for these observations. IHC and IF evaluations of tumor sections after the i.v. administration of scFv affinity mutants revealed that the lowest affinity molecule exhibited diffuse tumor staining whereas the highest affinity scFv was primarily retained in the perivascular regions of the tumor. These results indicate that antibody-based molecules with extremely high affinity have impaired tumor penetration properties that must be considered in the design of antibody-based cancer therapies.

Animals↗
PubMed2001

Increasing the affinity for tumor antigen enhances bispecific antibody cytotoxicity.

We tested the hypothesis that bispecific Abs (Bsab) with increased binding affinity for tumor Ags augment retargeted antitumor cytotoxicity. We report that an increase in the affinity of Bsab for the HER2/neu Ag correlates with an increase in the ability of the Bsab to promote retargeted cytotoxicity against HER2/neu-positive cell lines. A series of anti-HER2/neu extracellular domain-directed single-chain Fv fragments (scFv), ranging in affinity for HER2/neu from 10(-7) to 10(-11) M, were fused to the phage display-derived NM3E2 human scFV: NM3E2 associates with the extracellular domain of human FcgammaRIII (CD16). The resulting series of Bsab promoted cytotoxicity of SKOV3 human ovarian carcinoma cells overexpressing HER2/neu by human PBMC preparations containing CD16-positive NK cells. The affinity for HER2/neu clearly influenced the ability of the Bsab to promote cytotoxicity of (51)Cr-labeled SKOV3 cells. Lysis was 6.5% with an anti-HER2/neu K(D) = 1.7 x 10(-7) M, 14.5% with K(D) = 5.7 x 10(-9) M, and 21.3% with K(D) = 1.7 x 10(-10) M at 50:1 E:T ratios. These scFv-based Bsab did not cross-link receptors and induce leukocyte calcium mobilization in the absence of tumor cell engagement. Thus, these novel Bsab structures should not induce the dose-limiting cytokine release syndromes that have been observed in clinical trials with intact IgG BSAB: Additional manipulations in Bsab structure that improve selective tumor retention or facilitate the ability of Bsab to selectively cross-link tumor and effector cells at tumor sites should further improve the utility of this therapeutic strategy.

Adjuvants, Immunologic↗
PubMed2001

Expression of single-chain Fv-Fc fusions in Pichia pastoris.

Phage display technology makes possible the direct isolation of monovalent single-chain Fv antibody fragments. For many applications, however, it is useful to restore Fc mediated antibody functions such as avidity, effector functions and a prolonged serum half-life. We have constructed vectors for the convenient, rapid expression of a single-chain antibody Fv domain (scFv) fused to the Fc portion of human IgG1 in the methylotrophic yeast Pichia pastoris. The scFv-Fc fusion protein is secreted and recovered from the culture medium as a disulfide-linked, glycosylated homodimer. The increased size of the dimer (approximately 106 kDa vs. approximately 25 kDa for a scFv) results in a prolonged serum half-life in vivo, with t(1/2) of the beta phase of clearance increasing from 3.5 h for a typical scFv to 93 h for a scFv-Fc fusion in mice. The scFv-Fc fusion is capable of mediating antibody-dependent cellular cytotoxicity against tumor target cells using human peripheral blood mononuclear cells as effectors. Finally, the Fc domain is a convenient, robust affinity handle for purification and immunochemical applications, eliminating the need for proteolytically sensitive epitope and/or affinity tags on the scFv.

Amino Acid Sequence↗
PubMed2001

Fluorouracil modulation in colorectal cancer: lack of improvement with N -phosphonoacetyl- l -aspartic acid or oral leucovorin or interferon, but enhanced therapeutic index with weekly 24-hour infusion schedule--an Eastern Cooperative Oncology Group/Cancer and Leukemia Group B Study.

PURPOSE: To investigate mechanism-directed regimens in maximizing the efficacy of fluorouracil (5-FU) in advanced colorected cancer. PATIENTS AND METHODS: Based on promising phase II data, a randomized comparison of various methods for the biochemical modulation of 5-FU was undertaken in patients with advanced colorectal cancer. The control group received single-agent 5-FU as a 24-hour infusion weekly. Patients (N = 1,120) with no prior chemotherapy for metastatic disease were randomized to one of the following arms: arm A, 5-FU 2,600 mg/m2 by 24-hour infusion, weekly; arm B, N-phosphonoacetyl-l-aspartic acid 250 mg/m2 day l, 5-FU 2,600 mg/m2 by 24-hour infusion day 2, weekly; arm C, 5-FU 600 mg/m2 with oral leucovorin (LV) 125 mg/m2 hourly for the preceding 4 hours, weekly; arm D, 5-FU 600 mg/m2 with intravenous (IV) LV 600 mg/m2, weekly; arm E, 5-FU 750 mg/m2/d IV by continuous infusion for 5 days, then 750 mg/m2 weekly, and recombinant interferon alfa-2a 9 million units subcutaneously three times weekly. Median follow-up was 4.8 years. RESULTS: Of the 1,098 assessable patients, 57% had measurable disease. The toxicity of all the regimens was tolerable. Grade 4 or worse toxicity occurred in 11%, 11%, 30%, 24%, and 22% on each arm, respectively; diarrhea was the most common adverse effect. These toxicity patterns favored significantly (P <.001) the 24-hour infusion arms. Median survival (months) by arm was A, 14.8; B, 11.9; C, 13.5; D, 13.6; and E, 15.2. These survival durations did not differ significantly. CONCLUSION: We conclude that a weekly infusion regimen of 5-FU is significantly less toxic than and as effective as 5-FU bolus regimens modulated by either LV or interferon in patients with metastatic colorectal cancer.

Administration, Oral↗
PubMed2001

Phase I trial of multiple cycles of high-dose carboplatin, paclitaxel, and topotecan with peripheral-blood stem-cell support as front-line therapy.

PURPOSE: To determine the safety and feasibility of delivering multiple cycles of front-line high-dose carboplatin, paclitaxel, and topotecan with peripheral-blood stem-cell (PBSC) support. PATIENTS AND METHODS: Patients were required to have a malignant solid tumor for which they had received no prior chemotherapy. Mobilization of PBSC was achieved with either filgrastim alone or in combination with cyclophosphamide and paclitaxel. Patients then received three or four cycles of high-dose carboplatin (area under the concentration-time curve [AUC] 16), paclitaxel (250 mg/m(2)), and topotecan (10-15 mg/m(2)), with the latter two agents administered as 24-hour infusions and supported with PBSC and filgrastim. Cycles were repeated every 28 days. RESULTS: Twenty patients were enrolled onto the trial and were assessable for toxicity and clinical outcome. Dose-limiting toxicities were stomatitis and prolonged hematopoietic recovery. The maximum-tolerated dose of topotecan was 12.5 mg/m(2) when given with high-dose carboplatin and paclitaxel for three cycles. Four cycles were able to be given with a dose of topotecan of 10 mg/m(2). The pharmacokinetics of each compound were not affected by the other agents. Eleven (85%) of 13 patients with assessable disease responded. CONCLUSION: Multiple cycles of high-dose carboplatin, paclitaxel, and topotecan can be safely administered with filgrastim and PBSC support. The recommended doses for phase II study are carboplatin AUC 16, paclitaxel 250 mg/m(2), and topotecan 10 mg/m(2). Trials are currently being conducted with this regimen as front-line treatment in patients with advanced ovarian cancer and extensive small-cell carcinoma. This approach remains experimental and should be used only in the context of a clinical trial.

Adult↗
PubMed2001

Megestrol and tamoxifen in patients with advanced endometrial cancer: an Eastern Cooperative Oncology Group Study (E4882).

To investigate the effect of adding tamoxifen to megestrol in the hormonal therapy for advanced endometrial cancer, 66 patients were entered in this study. Initially, 41 patients were randomized to either the standard progestin therapy of megestrol or to the combination of megestrol and tamoxifen between October 1982 and October 1984. The megestrol arm was terminated because of poor accrual and 25 patients were directly assigned to the combination arm. Among the 20 eligible cases on the megestrol arm, the response rate of 20% consisted of I complete response and 3 partial responses. The response rate on the megestrol plus tamoxifen arm was 19% with 1 (2%) complete response and 7 (17%) partial responses among 42 eligible cases. The median survival times were 12.0 months and 8.6 months, respectively. Only mild and moderate toxicities were observed on megestrol compared with more toxic complications observed on the combination of megestrol and tamoxifen, including a life-threatening case of pulmonary embolism. Although we could not carry out a comparative evaluation as intended, we conclude that the combination of megestrol and tamoxifen offers no clinical advantage over megestrol alone in the treatment of advanced endometrial carcinoma.

Aged↗
PubMed2001

The influence of granulocyte macrophage colony-stimulating factor and prior chemotherapy on the immunological response to a vaccine (ALVAC-CEA B7.1) in patients with metastatic carcinoma.

Granulocyte macrophage colony-stimulating factor (GM-CSF) has been shown to be an effective vaccine adjuvant because it enhances antigen processing and presentation by dendritic cells. ALVAC-CEA B7.1 is a canarypox virus encoding the gene for the tumor-associated antigen carcinoembryonic antigen (CEA) and for a T-cell costimulatory molecule, B7.1. After an initial dose escalation phase, this study evaluated vaccination with 4.5 x 10(8) plaque-forming units ALVAC-CEA B7.1 alone (n = 30) or with GM-CSF (n = 30) in patients with advanced CEA-expressing tumors to determine whether the addition of the adjuvant GM-CSF enhances induction of CEA-specific T-cells. Patients were vaccinated with vaccine intradermally every other week for 8 weeks. GM-CSF was given s.c. for 5 days beginning 2 days before vaccination. Patients with stable or responding disease after four immunizations received monthly boost injections alone or with GM-CSF. Biopsies of vaccine sites were obtained 48 h after vaccination to evaluate leukocytic infiltration and CEA expression. Induction of peripheral blood CEA-specific T-cell precursors was assessed in HLA-A2 positive patients by an ELISPOT assay looking for the production of IFN-gamma. Therapy was well tolerated. All of the patients had evidence of leukocytic infiltration and CEA expression in vaccine biopsy sites. In the patients receiving GM-CSF, leukocytic infiltrates were greater in cell number but were less likely to have a predominant lymphocytic infiltrate compared with patients receiving vaccine in the absence of the cytokine adjuvant. After four vaccinations, CEA-specific T-cell precursors were statistically increased in HLA-A2 positive patients who received vaccine alone. However, the GM-CSF plus vaccine cohort of HLA-A2 positive did not demonstrate a statistically significant increase in their CEA-specific T-cell precursor frequencies compared with baseline results. The number of prior chemotherapy regimens was negatively correlated with the generation of a T-cell response, whereas there was a positive correlation between the number of months from the last chemotherapy regimen and the T-cell response. ALVAC-CEA B7.1 is safe in patients with advanced, recurrent adenocarcinomas that express CEA, is associated with the induction of a CEA-specific T-cell response in patients treated with vaccine alone but not with vaccine and GM-CSF, and can lead to disease stabilization for up to 13 months.

Adult↗
PubMed2000

New approaches to antibody therapy.

Antibody-based therapy of human cancers has led to several remarkable outcomes, particularly in the therapy of breast cancer and lymphoma. Many solid tumors have proven less responsive, due in part to difficulties in the tumor-selective delivery of antibodies and potential cytolytic effectors. However, antibodies that directly perturb signaling mechanisms in cells derived from epithelial malignancies have shown benefit; examples include antibodies directed against the extracellular domains of HER2/neu and epidermal growth factor receptor. A long-term goal of immunotherapy has been to induce anti-tumor inflammatory responses that can directly cause tumor regression or induce adaptive responses against tumor-related antigens. This review focuses on the use of antibodies to provide a means for initiating anti-tumor immune responses, and on the use of antibodies as delivery vehicles of radionuclides.

Animals↗
PubMed2000

Targeting of bivalent anti-ErbB2 diabody antibody fragments to tumor cells is independent of the intrinsic antibody affinity.

In immunodeficient mice antitumor single-chain Fv (scFv) molecules penetrate tumors rapidly and have rapid serum clearance, leading to excellent tumor:normal organ ratios. However, the absolute quantity of scFv retained in the tumor is low due to rapid serum clearance and monovalent scFv binding. We previously demonstrated that the presence of an additional binding site prolongs in vitro and in vivo association of scFv-based molecules with tumor cells expressing relevant antigen. The contribution of the intrinsic affinity of each component scFv to the association between a dimeric scFv and its target antigen is largely unknown. Here, we have constructed bivalent diabody molecules from three affinity mutants of the human anti-ErbB2 (HER2/neu) scFv molecule C6.5 by shortening the peptide linker between the heavy (VH) and light (VL) chains variable domains from 15 to 5 amino acids. The shorter linker prevents intramolecular pairing of VH and VL, resulting in intermolecular pairing and creation of a dimeric Mr 50,000 molecule with two antigen-binding sites. The scFv used to create the diabodies span a 133-fold range of affinity for the same epitope of ErbB2 [133 nM (C6G98A), 25 nM (C6.5), and 1 nM (C6ML3-9)] and differ by only one to three amino acids. Diabody binding kinetics were determined by surface plasmon resonance on the immobilized ErbB2 extracellular domain. The association rate constants obtained for each diabody molecule were similar to that of the parental (component) scFv. However, the dissociation rate constants obtained for the bivalent diabodies were up to 15-fold slower. The magnitude of the decrease in the bivalent dissociation rate constant was inversely proportional to the monovalent interaction, ranging from only 3-fold for that of the C6ML3-9 diabody to 15-fold for the C6G98A diabody. This resulted in only a 22-fold difference in bivalent affinity, compared with a 133-fold difference in affinity for the respective scFv. Equilibrium-binding constants obtained by surface plasmon resonance correlated well with the equilibrium-binding constants determined in vitro on ErbB2 overexpressing cells. Biodistribution studies were performed in scid mice bearing established SKOV3 tumors. At 24 h, 3-37-fold more diabody was retained in tumor compared with the parental scFv monomers. This likely results from a higher apparent affinity, because of bivalent binding, and a slower serum clearance. Surprisingly, the differences in affinity between diabodies did not result in differences in quantitative tumor retention or tumor to blood ratios. In fact, the diabody constructed from the lowest affinity scFv exhibited the best tumor-targeting properties. We conclude that, above a threshold affinity, other factors regulate quantitative tumor retention. In addition, straightforward dimerization of a low-affinity scFv leads to significantly greater tumor localization than does exhaustive scFv affinity maturation.

Animals↗
PubMed2000

Delivery of the alpha-emitting radioisotope bismuth-213 to solid tumors via single-chain Fv and diabody molecules.

Intravenously administered anti-tumor single-chain Fv (scFv) and diabody molecules exhibit rapid clearance kinetics and accumulation in tumors that express their cognate antigen. In an attempt to fit the rate of isotope decay to the timing of delivery and duration of tumor retention, anti-HER2/neu CHX-A" DTPA-C6.5K-A scFv and diabody conjugates were labeled with the alpha-particle emitter (213)Bi (t(1/2) = 47 min). Radioimmunotherapy studies employing 0.64, 0.35, or 0.15 microCi of (213)Bi-labeled C6.5K-A diabody or 1.1, 0.6, or 0. 3 microCi of (213)Bi-labeled C6.5K-A scFv were performed in nude mice bearing early, established SK-OV-3 tumors. Only the 0.3 microCi dose of (213)Bi-labeled C6.5K-A scFv resulted in both acceptable toxicity and a reduction in tumor growth rate. The specificity of the anti-tumor effects was determined by comparing the efficacy of treatment with 0.3 and 0.15 microCi doses of (213)Bi-labeled C6.5K-A scFv and (213)Bi-labeled NM3E2 (an irrelevant scFv) in nude mice bearing large established tumors. The 0.3 microCi dose of (213)Bi on both the C6.5K-A and NM3E2 scFvs resulted in similar anti-tumor effects (p = 0.46) indicating that antigen-specific targeting was not a factor. This suggests that the physical half-life of (213)Bi may be too brief to be effectively paired with systemically-administered diabody or scFv molecules.

Alpha Particles↗
PubMed2000

Recent advances in immunotherapy and monoclonal antibody treatment of cancer.

OBJECTIVES: To review the immune response and tumor immunology, and to provide an update on the success and obstacles to targeted therapy using monoclonal antibodies and antibody conjugates. DATA SOURCES: Research articles and textbooks. CONCLUSIONS: Ongoing studies are exploiting the targeting properties of the immune system to improve anticancer therapy. Both monoclonal antibodies and immunoconjugates have shown promise in treatment of specific diseases. IMPLICATIONS FOR NURSING PRACTICE: The rapid growth of molecular techniques has allowed for the development of new anticancer therapies. Since nurses are intimately involved in the delivery of such therapy as well as in educating patients regarding risks and benefits, they must be knowledgeable.

Antibodies, Monoclonal↗
PubMed2000

Phase II trial of yttrium-90-DOTA-biotin pretargeted by NR-LU-10 antibody/streptavidin in patients with metastatic colon cancer.

A Phase II study of yttrium-90-tetra-azacyclododecanetetra-acetic acid-biotin (90Y-DOTA-biotin) pretargeted by NR-LU-10 antibody/streptavidin (SA) was performed. The primary objectives of the study were to evaluate the efficacy and safety of this therapy in patients with metastatic colon cancer. Twenty-five patients were treated with a single dose of 110 mCi/m2 (mean administered dose, 106.5 +/- 10.3 mCi/m2) of 90Y-DOTA-biotin. There were three components of the therapy. Patients first received NR-LU-10/SA on day 1. A clearing agent (biotin-galactose-human serum albumin) was administered approximately 48 h after the NR-LU-10/SA to remove residual circulating unbound NR-LU-10/SA. Lastly, 24 h after administration of clearing agent, patients received biotin-DOTA-labeled with 110 mCi/m2 90Y. All three components of the therapy were administered i.v. Both hematological and nonhematological toxicities were observed. Diarrhea was the most frequent grade 4 nonhematological toxicity (16%; with 16% grade 3 diarrhea). Hematological toxicity was less severe with 8% grade 3 and 8% grade 4 neutropenia and 8% grade 3 and 16% grade 4 thrombocytopenia. The overall response rate was 8%. Two partial responders had freedom from progression of 16 weeks. Four patients (16%) had stable disease with freedom from progression of 10-20 weeks. Despite the relatively disappointing results of this study in terms of therapeutic efficacy and toxicity, proof of principle was obtained for the pretargeting approach. In addition, valuable new information was obtained about normal tissue tolerance to low-dose-rate irradiation that will help to provide useful guidelines for future study designs.

Adult↗
PubMed2000

Pilot study of a dual gene recombinant avipox vaccine containing both carcinoembryonic antigen (CEA) and B7.1 transgenes in patients with recurrent CEA-expressing adenocarcinomas.

Coordinated presentation of antigen and costimulatory molecules has been shown to result in the induction of an antigen-specific T-cell response rather than the development of anergy. This study evaluated the vaccine ALVAC-CEA B7.1, a canary pox virus that has been engineered to encode the gene for the tumor-associated antigen carcinoembryonic antigen (CEA) and B7.1, a T-cell costimulatory molecule. Patients with CEA-expressing tumors were immunized with 2.5 x 10(7) (n = 3), 1.0 x 10(8) (n = 6), and 4.5 x 10(8) (n = 30) plaque-forming units intradermally every other week for 8 weeks. Patients with stable or responding disease received monthly boost injections. Biopsies of vaccine sites were obtained 48 h after vaccination to evaluate leukocytic infiltration and CEA expression. Induction of CEA-specific T-cell precursors was assessed by an ELISPOT assay looking for the production of IFN-gamma. Therapy was well tolerated, without significant toxicity attributable to vaccine. All patients had evidence of leukocytic infiltration and CEA expression in vaccine biopsy sites. Six patients with elevated serum CEA values at baseline had declines in their levels lasting 4-12 weeks. These patients all had stable disease after four vaccinations. After four vaccinations, patients who were HLA-A-2-positive demonstrated increases in their CEA-specific T-cell precursor frequencies to a CEA-A2-binding peptide from baseline. The number of prior chemotherapy regimens was inversely correlated with the ability to generate a T-cell response. ALVAC-CEA B7.1 is safe in patients with advanced, recurrent adenocarcinomas that express CEA, and it is associated with the induction of a CEA-specific T-cell response.

Adenocarcinoma↗