Bayesian model-averaged benchmark dose analysis via reparameterized quantal-response models.

An important objective in biomedical and environmental risk assessment is estimation of minimum exposure levels that induce a pre-specified adverse response in a target population. The exposure points in such settings are typically referred to as benchmark doses (BMDs). Parametric Bayesian estimation for finding BMDs has grown in popularity, and a large variety of candidate dose-response models is available for applying these methods. Each model can possess potentially different parametric interpretation(s), however. We present reparameterized dose-response models that allow for explicit use of prior information on the target parameter of interest, the BMD. We also enhance our Bayesian estimation technique for BMD analysis by applying Bayesian model averaging to produce point estimates and (lower) credible bounds, overcoming associated questions of model adequacy when multimodel uncertainty is present. An example from carcinogenicity testing illustrates the calculations.

Statistical modeling and analyses of a base-specific Salmonella mutagenicity assay.

Statistical features of a base-specific Salmonella mutagenicity assay are considered in detail, following up on a previous report comparing responses of base-specific Salmonella (Ames II) strains with those of traditional tester strains. In addition to using different Salmonella strains, the new procedure also differs in that it is performed as a microwell fluctuation test, as opposed to the standard plate or preincubation test. This report describes the statistical modeling of data obtained from the use of these new strains in the microwell test procedure. We emphasize how to assess any significant interactions between replicate cultures and exposure doses, and how to identify a significant increase in the mutagenic response to a series of concentrations of a test substance.

Higher-dose and less frequent dendritic cell infusions with PSMA peptides in hormone-refractory metastatic prostate cancer patients.

BACKGROUND: Infusion of dendritic cells (DCs) pulsed with PSMA peptides was considered possible in hormone-refractory metastatic prostate cancer patients both with or without prior treatment with a greater number of DCs and for lesser infusions than previously administered. METHODS: DCs + PSMA peptides in patients undergoing leukapheresis were administered monthly 1-4 times, at rates greater than 20 million DCs in 17 patients not previously treated, and in 11 patients previously treated. RESULTS: Three partial responders and one complete responder were noted in the 17 previously untreated persons. DCs + PSMA peptides averaged 28.5 million cells (range in millions, 21.0-42.3). All responders received 3 or 4 infusions of greater than 22 million cells (3-4 times). In the previously treated group of 11 patients, DCs infused averaged 29.3 million cells (range in millions, 20-40.5). One new responder (bone scan) was noted. Two prior responders continued. Observation times were similar. Toxicity was minimal. CONCLUSIONS: These results suggest that DCs + PSMA peptide infusions can be given with greater numbers of DCs with a lesser number of infusions (1-4 monthly) with no loss of response rates compared to those noted previously, and without increased side effects. In previously treated patients (both relapsing and nonrelapsing), adverse effects were not noted, and new responses can be anticipated to be without harmful side effects. However, the follow-up time, and number of patients in this group, were small.

Prostate-specific membrane antigen (PSMA): current benefits and future value.

We will review the evolution, benefits, and limitations of PSMA testing in the past, as well as its current and future value. Prostate cancer has been the most frequently diagnosed cancer and the second leading cause of cancer death in men in the United States. It has a wide spectrum of biological behavior between latent (indolent) and progressive (aggressive). Further identification of prostate-specific membrane antigen (PSMA) as a prognostic proliferation marker may enhance our understanding of the types of prostate cancer. A review of PSMA testing in the past as well as currently was conducted. Studies were reviewed that deal with detection of PSMA in serum and seminal fluid, reverse transcriptase-polymerase chain reaction (RT-PCR), immunoscintigraphy, and immunohistochemical assays. PSMA is expressed primarily in benign and cancerous prostatic epithelial cells. It is up-regulated in hormone resistant states, and in metastatic situations or other clinical situations where there is tumor recurrence or extension. Based on current results, PSMA detected in the serum by western blotting can assist in the identification, staging, and monitoring of metastatic prostate cancer. In addition, PSMA shows a promising role in directed imaging and therapy of recurrent or metastatic disease.

Use of artificial neural networks in evaluating prognostic factors determining the response to dendritic cells pulsed with PSMA peptides in prostate cancer patients.

BACKGROUND: Our purpose was to compare the importance of over 22 measurements used in evaluating the clinical responses of patients with metastatic or locally recurrent prostate cancer, treated by dendritic cell (DC) infusions with prostate-specific membrane antigen (PSMA) peptides. METHODS: Artificial neural networks (ANNs) were employed for assessment, as well as the traditional methods of logistic regression. RESULTS: Twenty-six patients with metastatic disease and 37 patients with local recurrence were available for evaluation and comparison. ANN evaluation ranked the collective effects of DC infusion, immune responses (CD3+ cells, CD16+ cells, zeta chain+ cells), and cytokines, e.g., IL-6 and PSMA levels, very highly. Logistic regression identified all of these parameters to some degree, but in a different rank order. Patients with metastases showed a sharp rate of response secondary to the level of DC infusion, in contrast to those patients with local recurrence, in which it was more gradual. CONCLUSIONS: ANN analysis emphasizes the importance of level of DC infusion, immune parameters, cytokines, and markers such as PSMA in determining the response to PSMA peptide immunotherapy. The criteria of response were judged to be correct in 86% of metastatic patients and 83% of locally recurrent patients evaluated in this study.

Follow-up evaluation of a phase II prostate cancer vaccine trial.

BACKGROUND: A phase II trial, involving infusions of autologous dendritic cells (DC) and two human histocompatibility antigen (HLA-A2)-specific prostate-specific membrane antigen (PSMA) peptides, was recently completed. Thirty percent of the participants, including subjects with hormone-refractory metastastic disease, and those with suspected local recurrence of prostate cancer, were identified as clinical responders. This report describes the follow-up evaluation of 19 responders in the two study groups. METHODS: After conclusion of the study, study participants were subjected to follow-up evaluations at 6-8-week intervals. Each responder was reevaluated for response status, and duration of response was determined. RESULTS: Subjects were observed for an average of 291 days (metastastic group, group A-2) and 557 days (local recurrence group, group B), which included the treatment and follow-up periods. The average duration of response was 149 days for group A-2, and 187 days for group B. A majority of responders (11/19; 58%) were still responsive at the end of the current follow-up. CONCLUSIONS: The responses observed may be significant and relatively durable. This study suggests that DC-based cancer vaccines in the future may provide an additional therapy for advanced prostate cancer.

GM-CSF as a systemic adjuvant in a phase II prostate cancer vaccine trial.

BACKGROUND: Recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF; Leukine [sargramostim], Immunex Corp., Seattle, WA) was administered to a subgroup of 44 patients in a phase II clinical trial for prostate cancer using DC pulsed with HLA-A2-specific prostate-specific membrane antigen (PSMA) peptides. Our purpose was to determine if GM-CSF caused any enhancement of patients' immune responses, including enhancement of clinical response to the DC-peptide treatment. This report compares the clinical responses to DC-peptide infusions with and without systemic GM-CSF treatment. METHODS: GM-CSF was administered by subcutaneous injection at a dose of 75 microg/m2/day for 7 days with each of six infusion cycles. Prefilled syringes were supplied to the patients for self-administration. RESULTS: One complete and 8 partial responders were identified among 44 patients who received GM-CSF, as compared to 2 complete and 17 partial responders among 51 patients who did not receive GM-CSF. For patients who received GM-CSF and were tested by delayed-type hypersensitivity (DTH) skin test, 3 cases of improved immune response were identified, compared to 5 cases of improvement in patients who did not receive GM-CSF. The main GM-CSF side effects reported were local reactions at the site of injection, fatigue, pain, and fever. Most reported side effects were of mild severity, with some cases of moderate severity leading to discontinuation of GM-CSF. CONCLUSIONS: Our results suggest GM-CSF as employed in this trial did not detectably enhance clinical response to DC-peptide infusions, or significantly enhance the measured immune response.

Phase II prostate cancer vaccine trial: report of a study involving 37 patients with disease recurrence following primary treatment.

BACKGROUND: A phase II trial was conducted to assess the efficacy of infusions of dendritic cells (DC) and two HLA-A2-specific prostate-specific membrane antigen (PSMA) peptides (PSM-P1 and -P2). This report describes the evaluation of 37 subjects admitted with presumed local recurrence of prostate cancer after primary treatment failure. METHODS: All subjects received six infusions of DC pulsed with PSM-P1 and -P2 at 6-week intervals. Clinical monitoring was conducted pre-, during, and post-phase II study. Data included: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint scan, and chest X-ray, as well as other assays to monitor cellular and humoral immune responses. RESULTS: One complete and 10 partial responders were identified from this group based on National Prostate Cancer Project criteria, or on a 50% reduction of prostate-specific antigen (PSA), or on a significant resolution in lesions (biopsy-proven when possible) on ProstaScint scan. CONCLUSIONS: About 30% of study participants in this group showed a positive response at the conclusion of the trial. This study suggests that DC-based cancer vaccines may provide an alternative therapy for prostate cancer patients whose primary treatment failed.

Infusion of dendritic cells pulsed with HLA-A2-specific prostate-specific membrane antigen peptides: a phase II prostate cancer vaccine trial involving patients with hormone-refractory metastatic disease.

BACKGROUND: A phase II trial was conducted to assess the efficacy of infusions of dendritic cells (DC) and two HLA-A2-specific PSMA peptides (PSM-P1 and -P2). This report describes thirty three subjects with hormone-refractory metastatic prostate cancer without prior vaccine therapy history who were evaluated and reported as a group. METHODS: All subjects received six infusions of DC pulsed with PSM-P1 and -P2 at six week intervals. Clinical monitoring was conducted pre-, during, and post- phase II study. Data collected include: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint scan, chest x-ray, as well as assays to monitor cellular immune responses. RESULTS: Six partial and two complete responders were identified in the phase II study based on NPCP criteria, plus 50% reduction of prostate-specific antigen (PSA), or resolution in previously measurable lesions on ProstaScint scan. CONCLUSIONS: Over 30% of study participants in this group showed a positive response at the conclusion of the trial. This study suggested that DC-based cancer vaccines may provide an alternative therapy for prostate cancer patients whose disease no longer responds to hormone therapy.

Evaluation of phase I/II clinical trials in prostate cancer with dendritic cells and PSMA peptides.

BACKGROUND: A phase I trial involving patients with advanced prostate cancer was conducted to assess the safe administration of dendritic cells (DC) and HLA-A0201-specific prostate-specific membrane antigen (PSMA) peptides (PSM-P1 or -P2). Thirty-three of the phase I participants were subsequently enrolled in a phase II trial, which involved six infusions of DC pulsed with PSM-P1 and -P2 peptides. METHODS: Clinical monitoring was conducted up to 770 days from the start of the phase I study. Data collected included: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint scan, and chest X-ray, as well as assays to monitor cellular immune responses. RESULTS: Nine partial responders were identified in the phase II study based on National Prostate Cancer Project (NPCP) criteria, plus 50% reduction of prostate-specific antigen. Four of the partial responders were also responders in the phase I study, with an average response duration of 225 days. Their combined average total response period was over 370 days. Five other responders were nonresponders in the phase I study. Their average partial response period was 196 days. CONCLUSIONS: The responses observed in the phase I and II clinical trials were significant and of long duration. The partial-responder group included patients who continued to respond from phase I, as well as those who started to respond during the phase II trial.

Different estrogen receptor structural domains are required for estrogen- and tamoxifen-dependent anti-proliferative activity in human mammary epithelial cells expressing an exogenous estrogen receptor.

Estrogen (E) inhibits the growth of both non-tumorigenic, immortal human mammary epithelial cells (HMEC) and breast cancer cells which stably express exogenous estrogen receptors (ER). The anti-estrogenic compounds 4-hydroxy-tamoxifen (HT) and ICI 164384 (ICI) have different effects on the growth of the ER-transfectants. HT is a potent growth inhibitor, while ICI has no effect by itself but is able to block the anti-proliferative effects of E and HT. In order to elucidate the mechanism by which E or HT-bound ER inhibit cell growth, we have evaluated the effects of these compounds on the growth of HMEC stably expressing ER with mutations or deletions in the N-terminal A/B domain, the DNA-binding domain (DBD), and the C-terminal ligand-binding domain. These studies revealed that E and HT require different structural domains of the ER for their anti-proliferative activities. The N-terminal A/B domain is required for HT-, but not E-dependent growth inhibition. The DNA-binding domain of the ER is not essential for HT-mediated anti-proliferative effects, but is important for E-dependent activity. The effect of ER mutations on the ligand-inducible expression of the endogenous progesterone receptor (PR) and pS2 genes was also evaluated. Neither gene was induced in the cells containing the ER mutated in the DBD, even though cell growth was inhibited. These results suggest that E and HT use different pathways to elicit their anti-proliferative effects and that this occurs via modulation of genes that are controlled by mechanisms different from those important for activation of the PR and pS2 genes.

Variant cDNA sequences of human ATP:citrate lyase: cloning, expression, and purification from baculovirus-infected insect cells.

ATP:citrate lyase (ACL) is a major generator of cytosolic acetyl-coenzymeA, which is required for both fatty acid and cholesterol biosynthesis. The human ACL (hACL) cDNA was cloned by RT-PCR, and our results indicate the existence of previously unknown sequence variations in hACL. Expression of the hACL cDNA in Spodoptera frugiperda 9 insect cells resulted in the production of high levels of soluble, active enzyme. The recombinant protein (re-hACL) was purified to homogeneity from the soluble lysate of infected cells and was observed to exist as a tetramer by gel filtration chromatography. Kinetic analyses indicated that the re-hACL and rat ACL have very similar enzymological properties. The facile preparation of milligram quantities of purified, active re-hACL affords the opportunity to characterize the enzyme for structure-based design of hypolipidemic drugs, and to further examine the functional significance of the sequence variations.

The complete set of predicted genes from Saccharomyces cerevisiae in a readily usable form.

Nearly all of the open reading frames (ORFs) of the yeast Saccharomyces cerevisiae have been synthesized by PCR using a set of approximately 6000 primer pairs. Each of the forward primers has a common 22-base sequence at its 5' end, and each of the back primers has a common 20-base sequence at its 5' end. These common termini allow reamplification of the entire set of original PCR products using a single pair of longer primers-in our case, 70 bases. The resulting 70-base elements that flank each ORF can be used for rapid and efficient cloning into a linearized yeast vector that contains these same elements at its termini. This cloning by genetic recombination obviates the need for ligations or bacterial manipulations and should permit convenient global approaches to gene function that require the assay of each putative yeast gene.

Production of active human interleukin-1 beta-converting enzyme in a baculovirus expression system.

The cDNA coding for the precursor form of human interleukin-1 beta-converting enzyme (proICE) was expressed in Spodoptera frugiperda (Sf9) insect cells using a baculovirus expression system. The 45-kDa recombinant protein was further processed to several smaller forms of 32, 24, 20, 13 and 10 kDa. Active recombinant ICE derived from the baculovirus expression system (bvICE) was found to be present in soluble lysates of insect cells as an associated heterodimer consisting of 10- and 20-kDa subunits. The activity of bvICE was determined by conversion of precursor interleukin-1 beta (preIL-1 beta) to the mature form (mIL-1 beta) and via site-specific cleavage of a decapeptide which spans the ICE cleavage site in preIL-1 beta. The bvICE system was inhibited by an ICE inhibitor to the same extent as native ICE from the monocytic cell line THP-1. Expression of an active-site mutant (Cys285 to Ser) of proICE in insect cells resulted in the accumulation of partially processed (32-kDa) ICE. The availability of a facile expression system will permit further characterization of the biochemical properties and processing pathway of this unique protease.

Explaining health-promoting lifestyles of Navy personnel.

This study examined the relationship of six dimensions of health-promoting lifestyle (self-actualization, health responsibility, interpersonal support, exercise, nutrition, and stress management) with selected sociodemographic and attitudinal variables in a random sample of 421 active duty Navy personnel. Participants who were older, officers, shore-based, married, and who reported high levels of perceived health all had significantly higher scores for overall health-promoting life-style and several lifestyle dimensions. Exercise of self-care agency--a composite health attitude indicator--accounted for 35% of the variance in health-promoting lifestyle patterns. Among the sociodemographic variables, educational level, race, and perceived health state were differentially predictive of healthy lifestyle dimensions.

The Sea of Life: a metaphorical vehicle for theory explication.

Metaphorical expression is viewed as a fundamental way of symbolizing used to develop nursing theory. The Sea of Life poem depicts a metaphor for explicating a theoretical structure derived from principles of the human becoming theory: Transforming occurs in the revealing-concealing of valuing. The Sea of Life, an original poem, sets forth the idea that unique meanings are co-created through human-environment relationships. The concepts of valuing, revealing-concealing, and transforming are linked through the poem to lived experiences. The easily recognizable concrete lived experiences which flow from the poem are re-conceptualized to formulate research questions.

The Health-Promoting Self-Care System Model: directions for nursing research and practice.

In an effort to theoretically integrate perspectives of self-care and health promotion, the Health-Promoting Self-Care System Model is proposed as a framework for identifying and explaining sequential patterns among factors which influence the decision-making, performance and outcomes of health-promoting lifestyles. The model is based upon a synthesis of elements comprising constructs of the Self-Care Deficit Nursing Theory as well as certain factors in the Interaction Model of Client Health Behaviour and the Health Promotion Model. Directions for research and practice provided by the model should encourage the development of a cumulative nursing knowledge base and contribute to the goal of enhancing the health and well-being of persons across developmental and sociocultural contexts.