Evaluating the impact of anatomical and physiological variability on human equivalent doses using PBPK models

Addressing human anatomical and physiological variability is a crucial component of human health risk assessment of chemicals. Experts have recommended probabilistic chemical risk assessment paradigms in which distributional adjustment factors are used to account for various sources of uncertainty and variability, including variability in the pharmacokinetic behavior of a given substance in different humans. In practice, convenient assumptions about the distribution forms of adjustment factors and human equivalent doses (HEDs) are often used. Parameters such as tissue volumes and blood flows are likewise often assumed to be lognormally or normally distributed without evaluating empirical data for consistency with these forms. In this work, we performed dosimetric extrapolations using physiologically based pharmacokinetic (PBPK) models for dichloromethane (DCM) and chloroform that incorporate uncertainty and variability to determine if the HEDs associated with such extrapolations are approximately lognormal and how they depend on the underlying distribution shapes chosen to represent model parameters. We accounted for uncertainty and variability in PBPK model parameters by randomly drawing their values from a variety of distribution types. We then performed reverse dosimetry to calculate HEDs based on animal points of departure (PODs) for each set of sampled parameters. Corresponding samples of HEDs were tested to determine the impact of input parameter distributions on their central tendencies, extreme percentiles, and degree of conformance to lognormality. This work demonstrates that the measurable attributes of human variability should be considered more carefully and that generalized assumptions about parameter distribution shapes may lead to inaccurate estimates of extreme percentiles of HEDs.

Enhancing classical swine fever virus identification: the advantages of Field-LAMP testing

Classical swine fever virus (CSFV) identification has witnessed significant advancements with the development of rapid reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assays. However, conventional RT-LAMP assays for CSFV diagnosis are hindered by a laborious RNA extraction step. Moreover, the need for thermal incubators and expensive micropipettes has limited their application in field settings. Addressing these challenges, our study presents a groundbreaking solution-an electro-free and point-of-care (POC) tool known as the field-LAMP assay-for the rapid clinical detection of CSFV. By eliminating the RNA extraction requirement, advancing the colorimetric read-out and lyophilized reaction reagents, our field-LAMP assay streamlines the diagnostic process, saving valuable time and effort. This novel approach also overcomes the dependency on electric-dependent thermal incubators and expensive micropipettes, making it practical and accessible for use in the field. The successful development of the field-LAMP assay marks a significant milestone in CSFV detection. This electro-free and POC tool offers several advantages, including its ability to deliver rapid results without compromising accuracy, facilitating prompt response and containment measures.

Circulating tumor DNA and radiological tumor volume identify patients at risk for relapse with resected, early-stage non-small-cell lung cancer

BACKGROUND

Predicting relapse and overall survival (OS) in early-stage non-small-cell lung cancer (NSCLC) patients remains challenging. Therefore, we hypothesized that detection of circulating tumor DNA (ctDNA) can identify patients with increased risk of relapse and that integrating radiological tumor volume measurement along with ctDNA detectability improves prediction of outcome.

PATIENTS AND METHODS

We analyzed 366 serial plasma samples from 85 patients who underwent surgical resections and assessed ctDNA using a next-generation sequencing liquid biopsy assay, and measured tumor volume using a computed tomography-based three-dimensional annotation.

RESULTS

Our results showed that patients with detectable ctDNA at baseline or after treatment and patients who did not clear ctDNA after treatment had a significantly worse clinical outcome. Integrating radiological analysis allowed the stratification in risk groups prognostic of clinical outcome as confirmed in an independent cohort of 32 patients.

CONCLUSIONS

Our findings suggest ctDNA and radiological monitoring could be valuable tools for guiding follow-up care and treatment decisions for early-stage NSCLC patients.

Integrating cytokines and angiogenic factors and tumour bulk with selected clinical criteria improves determination of prognosis in advanced renal cell carcinoma

Background:

In two clinical trials of the vascular endothelial growth factor (VEGF) receptor inhibitor pazopanib in advanced renal cell carcinoma (mRCC), we found interleukin-6 as predictive of pazopanib benefit. We evaluated the prognostic significance of candidate cytokines and angiogenic factors (CAFs) identified in that work relative to accepted clinical parameters.

Methods:

Seven preselected plasma CAFs (interleukin-6, interleukin-8, osteopontin, VEGF, hepatocyte growth factor, tissue inhibitor of metalloproteinases (TIMP-1), and E-selectin) were measured using multiplex ELISA in plasma collected pretreatment from 343 mRCC patients participating in the phase 3 registration trial of pazopanib vs placebo (NCT00334282). Tumour burden (per sum of longest diameters (SLD)) and 10 other clinical factors were also analysed for association with overall survival (OS; based on initial treatment assignment).

Results:

Osteopontin, interleukin-6, and TIMP-1 were independently associated with OS in multivariable analysis. A model combining the three CAFs and five clinical variables (including SLD) had higher prognostic accuracy than the International Metastatic Renal Cell Carcinoma Database Consortium criteria (concordance-index 0.75 vs 0.67, respectively), and distinguished two groups of patients within the original intermediate risk category.

Conclusions:

A prognostic model incorporating osteopontin, interleukin-6, TIMP-1, tumour burden, and selected clinical criteria increased prognostic accuracy for OS determination in mRCC patients.

A high burden of late-onset sepsis among newborns admitted to the largest neonatal unit in central Vietnam

OBJECTIVE

The objective of this study is to determine the prevalence, causes and outcome of sepsis in hospitalized neonates in the largest neonatal unit in central Vietnam.

STUDY DESIGN

A 1-year prospective cohort study of newborns admitted to the neonatal unit in Da Nang. A sepsis work-up including blood culture was undertaken before commencing antibiotics for neonates with suspected sepsis.

RESULT

Of 2555 neonatal admissions, 616 neonates had 729 episodes of suspected invasive sepsis. A pathogen was isolated from blood in 115 (16%) episodes in 106 neonates. The prevalence of early-onset sepsis (EOS) was 8 (95% confidence interval (CI): 4 to 11) per 1000 admissions, and of late-onset sepsis (LOS) was 34 (95% CI: 27 to 41) per 1000 admissions. Of 86 neonates with LOS, 69 (80%) also fulfilled the criteria for nosocomial sepsis. The commonest bacterial causes of EOS were coagulase-negative Staphylococcus (CoNS) and Staphylococcus aureus, and of LOS were Acinetobacter, CoNS and Klebsiella pneumoniae. Fungal sepsis occurred in 35 neonates of which most were nosocomial sepsis. In vitro resistance to multiple antibiotics was common among Gram-negative bacteria. Antibiotics were prescribed and given to 68% of all admissions, and 14% of all admissions received four or more different antibiotics. The case fatality rate for confirmed sepsis was 46%.

CONCLUSION

Late-onset, nosocomial sepsis was common and associated with a high mortality in hospitalized newborns in the largest neonatal unit in central Vietnam. These findings highlighted the need for improved infection control measures and antibiotic stewardship, which have since been implemented.

Phase II trial of everolimus and erlotinib in patients with platinum-resistant recurrent and/or metastatic head and neck squamous cell carcinoma

BACKGROUND

Enhanced phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is one of the key adaptive changes accounting for epidermal growth factor receptor (EGFR) inhibitor-resistant growth in head and neck squamous cell carcinoma (HNSCC). We designed a phase II clinical trial of EGFR tyrosine kinase inhibitor (TKI), erlotinib, in association with the mTOR inhibitor, everolimus, based on the hypothesis that the downstream effects of Akt through inhibition of mTOR may enhance the effectiveness of the EGFR-TKI in patients with recurrent/metastatic HNSCC.

PATIENTS AND METHODS

Patients with histologically or cytologically confirmed platinum-resistant HNSCC received everolimus 5 mg and erlotinib 150 mg daily orally until disease progression, intolerable toxicity, investigator or patient decision. Cytokines and angiogenic factors profile, limited mutation analysis and p16 immunohistochemistry status were included in the biomarker analysis.

RESULTS

Of the 35 assessable patients, 3 (8%) achieved partial response at 4 weeks, 1 confirmed at 12 weeks; overall response rate at 12 weeks was 2.8%. Twenty-seven (77%) patients achieved disease stabilization at 4 weeks, 11 (31%) confirmed at 12 weeks. Twelve-week progression-free survival (PFS) was 49%, median PFS 11.9 weeks and median overall survival (OS) 10.25 months. High neutrophil gelatinase lipocalin (P = 0.01) and vascular endothelial growth factor (VEGF) (P = 0.04) plasma levels were significantly associated with worse OS.

CONCLUSIONS

The combination of erlotinib and everolimus did not show significant benefit in unselected patients with platinum-resistant metastatic HNSCC despite a manageable toxicity profile. Markers of tumor invasion and hypoxia identify a group of patients with particularly poor prognosis.

CLINICAL TRIAL NUMBER

NCT00942734.

Potential role of chitinases and chitin-binding proteins in host-microbial interactions during the development of intestinal inflammation

The small and large intestines contain an abundance of luminal antigens derived from food products and enteric microorganisms. The function of intestinal epithelial cells is tightly regulated by several factors produced by enteric bacteria and the epithelial cells themselves. Epithelial cells actively participate in regulating the homeostasis of intestine, and failure of this function leads to abnormal and host-microbial interactions resulting in the development of intestinal inflammation. Major determinants of host susceptibility against luminal commensal bacteria include genes regulating mucosal immune responses, intestinal barrier function and microbial defense. Of note, it has been postulated that commensal bacterial adhesion and invasion on/into host cells may be strongly involved in the pathogenesis of inflammatory bowel disease (IBD). During the intestinal inflammation, the composition of the commensal flora is altered, with increased population of aggressive and detrimental bacteria and decreased populations of protective bacteria. In fact, some pathogenic bacteria, including Adherent-Invasive Escherichia coli, Listeria monocytogenes and Vibrio cholerae are likely to initiate their adhesion to the host cells by expressing accessory molecules such as chitinases and/or chitin-binding proteins on themselves. In addition, several inducible molecules (e.g., chitinase 3-like 1, CEACAM6) are also induced on the host cells (e.g. epithelial cells, lamina proprial macrophages) under inflammatory conditions, and are actively participated in the host-microbial interactions. In this review, we will summarize and discuss the potential roles of these important molecules during the development of acute and chronic inflammatory conditions.

A cytokine and angiogenic factor (CAF) analysis in plasma for selection of sorafenib therapy in patients with metastatic renal cell carcinoma

BACKGROUND

We investigated cytokines and angiogenic factors (CAFs) in patients with metastatic renal cell carcinoma (mRCC) treated in a randomized phase II clinical trial of sorafenib versus sorafenib+ interferon-α (IFN-α) that yielded no differences in progression-free survival (PFS). We aimed to link the CAF profile to PFS and select candidate predictive and prognostic markers for further study.

METHODS

The concentrations of 52 plasma CAFs were measured pretreatment (n = 69), day 28, and day 56 using multiplex bead arrays and enzyme-linked immunosorbent assay. We investigated the association between baseline levels of CAFs with PFS and posttreatment changes.

RESULTS

Unsupervised CAF clustering analysis revealed two distinct mRCC patient groups with elevated proangiogenic or proinflammatory mediators. A six-marker baseline CAF signature [osteopontin, vascular endothelial growth factor (VEGF), carbonic anhydrase 9, collagen IV, VEGF receptor-2, and tumor necrosis factor-related apoptosis-inducing ligand] correlated with PFS benefit (hazard ratio 0.20 versus 2.25, signature negative versus positive, respectively; P = 0.0002). While changes in angiogenic factors were frequently attenuated by the sorafenib+ IFN combination, most key immunomodulatory mediators increased.

CONCLUSIONS

Using CAF profiling, we identified two mRCC patient groups, a candidate plasma signature for predicting PFS benefit, and distinct marker changes occurring with each treatment. This platform may provide valuable insights into renal cell carcinoma biology and the molecular consequences of targeted therapies.

Cytokine and angiogenic factor (CAF) profiling for identification of markers associated with response to cediranib in metastatic renal cell carcinoma (mRCC)

362

Background: Cediranib is a highly potent and selective signaling inhibitor of vascular endothelial growth factor (VEGF) receptors−1, −2, −3 and c-Kit. In a phase II trial, patients (pts) with mRCC were randomized 3:1 to treatment with cediranib or placebo to primarily assess the difference in change in tumor size at 12 weeks. Cediranib resulted in a significant reduction in tumor size vs. placebo (Mulders et al. ESMO. 2009). Here we investigated soluble biomarkers in serum and concentration changes during treatment.

Methods: Pts received cediranib 45 mg/day PO or placebo for the first 12 weeks on treatment. At that time (or upon progression if earlier), treatment was unblinded and pts on placebo were given the option of receiving cediranib. Serum was collected from 61 pts at baseline (BL; cediranib 46, placebo 15), from 50 pts on day (D) 28, and from 45 pts on D84. Multiplex bead suspension arrays and ELISA were used to measure CAF concentrations including VEGF, placental growth factor (PlGF), sVEGFR-2, PDGFbb, HGF, MMP-9, multiple chemokines and interleukins (IL). The objectives of this exploratory analysis were to assess whether baseline CAFs were associated with changes in tumor size after 12 weeks of treatment and whether CAF levels changed while on treatment.

Results: Of 39 CAFs available at BL, lower than median (‘low') concentrations of IL-10, VEGF, PlGF, stem cell factor (SCF), and monokine-induced by interferon-gamma (MIG) were associated with larger decreases in tumor size than high concentrations (independent of treatment arm), whereas the opposite trend was observed for IL-5 and TRAIL. Consistent with inhibition of VEGF signaling, cediranib treatment resulted in changes over time in VEGF (increase), sVEGFR-2 (decrease) and PlGF (increase) concentrations. In addition, SCF, a c-Kit ligand and M-CSF decreased, while VCAM-1 and TRAIL increased during cediranib treatment.

Conclusions: Candidate CAFs associated with response to cediranib in mRCC such as IL-10 and VEGF were identified. Patients treated with cediranib showed distinct CAF changes compared with placebo. These results require independent validation in a larger trial.

[Table: see text]

Plasma cytokine and angiogenic factors (CAFs) predictive of clinical benefit and prognosis in patients (Pts) with advanced or metastatic renal cell cancer (mRCC) treated in phase III trials of pazopanib (PAZO)

334

Background: PAZO is a multikinase inhibitor approved for the treatment of mRCC. From phase II study of PAZO in mRCC (VEG102616), plasma CAF analysis from 3 different platforms (cross platform correlation r >0.70) revealed several candidate CAFs including HGF, IL-6, IL-8, TIMP-1, VEGF, E-Selectin and OPN were found to be significantly correlated with clinical benefit (Tran ASCO 2010, #4522). To validate these findings, plasma were analyzed for CAFs from mRCC pts enrolled in phase III randomized, placebo controlled trial with PAZO where progression-free survival (PFS) of 9.2 months of PAZO and 4.2 months of placebo (hazard ratio:0.46 p<.0001) and overall response rate 30% was observed (Sternberg, JCO, 2010).

Methods: Plasma samples (n=344) from phase III randomized, placebo-controlled trial (VEG105192) were analyzed for candidate CAFs by a CLIA-certified laboratory (Aushon Biosystems, MA). These markers of PAZO and placebo arms were correlated with PFS by Cox regression and plotted in Kaplan Meier by using median concentration of each marker as a cutoff.

Results: Higher levels of IL-8 (p<0.006), HGF (p<0.01), OPN (p<0.001) and TIMP-1 (p<0.006) were associated with shorter PFS in PAZO treated pts. Higher levels of all these markers except HGF were also associated with shorter PFS in the placebo arm (IL-8 (p<0.002), OPN (p<0.001), IL-6 (<0.001), TIMP-1 borderline at p= 0.052) and were therefore prognostic. Only IL-6 was predictive of PFS benefit; pts with high IL-6 had a greater relative benefit from PAZO compared to placebo with a HR of 0.32 in the high IL-6 group and 0.57 in the low IL-6 group (p value for interaction 0.009).

Conclusions: This study validated HGF, IL-8, OPN, and TIMP-1 as markers associated with clinical benefit with PAZO treatment. IL-8 and OPN were confirmed as prognostic markers in the placebo arm and IL-6 was both a prognostic marker and predictive marker for pazopanib therapy.

[Table: see text]

Afm Study of CeO2 Growth on Sapphire as a Buffer Layer for YBa2Cu3O7

The structure of CeO2 films grown on (1102) sapphire and on YBCO thin films was investigated. The films reported on here were grown by pulsed excimer laser deposition and their surface structure was probed using atomic force microscopy. We found that CeO2 films grown on sapphire were epitaxial with a granular structure which is smooth on an atomic scale. We see evidence of a surface reconstruction on a very smooth CeO2 (100) oriented surface. At higher growth temperatures, three dimensional islands begin to form. When a CeO2 film is grown on top of a YBCO film, the growth mode is two dimensional. The steps in this layer by layer growth are a surprisingly large 2 nm. This is about equal to 4 times the CeO2 lattice constant. This step height appears to be temperature dependent.

Association of circulating cytokine and angiogenic factors (CAFs) with outcomes to second-line FOLFOX plus bevacizumab or cediranib in metastatic colorectal cancer

406

Background: Chemotherapy combined with inhibitors of VEGF signaling is associated with improved outcomes, but biomarkers of therapeutic benefit have been elusive. Cediranib (Ced) is an oral VEGFR tyrosine kinase inhibitor that has been investigated as a treatment for metastatic colorectal cancer (mCRC).

Methods: 215 patients with progressive disease and no prior VEGF inhibitor therapy were enrolled in a randomized phase II study of FOLFOX + Ced 20mg/d, Ced 30mg/d or bevacizumab (Bev) 10mg/kg (Cunningham D, et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 4028). 36 CAFs were analyzed at 3 time points (baseline, wk 4, wk 8). Groups were dichotomized by median CAF value. Hazard ratios (HRs) were estimated from a Cox model with a single term.

Results: Data were available for > 85% patients for each CAF. When pooled across all arms, several baseline CAFs including VEGF, interleukin (IL)-2Rα, IL-8 and PDGF were associated with improved PFS (Table). Low and high baseline CAF subgroups were evaluated for potential predictive CAFs. Pts with elevated baseline IL-8 did better with Ced 30mg/d than Bev (HR 0.6 for PFS, CI 0.3-1.0) while low IL-8 was associated with greater benefit from Bev than Ced (HR 2.1, CI 1.0 to 4.2). For Ced 20mg/d, PFS HRs were 0.9 (CI 0.5, 1.6) and 1.7 (CI 0.9, 3.2) for elevated and low baseline IL-8 respectively. Hepatocyte-growth factor (HGF) demonstrated a similar relationship, while a trend for the inverse association was seen with IP-10. Distinct patterns of cytokine modulation were seen between Ced and Bev during the 8 wks, including decreases of sVEGFR2, IL-13 and increases in osteopontin.

Conclusions: Several potential prognostic factors for second-line mCRC therapy were identified including VEGF and IL-8. Further work in larger placebo-controlled studies is required to further evaluate predictive markers for VEGF signaling inhibitors.

[Table: see text]

[Table: see text]

Relative impact of chemotherapy with or without bevacizumab on cytokines and angiogenic factors (CAFs) in metastatic colorectal cancer

401

Background: CAFs were previously shown to be modulated in patients (pts) with metastatic colorectal cancer (mCRC) after bevacizumab-containing chemotherapy. Validation of these prior findings is warranted. In addition, the relative impact of bevacizumab and the cytotoxic chemotherapy components on CAFs has not been previously described.

Methods: Plasma samples from 403 mCRC pts were obtained prior to any chemotherapy (Group A) or after progression on a regimen without or with bevacizumab (Group B and C, respectively) between 2002 and 2008. Samples were matched for number of metastatic disease sites (Groups A, B, C) and for prior chemotherapy duration, and time from last chemotherapy dose to sample collection (Groups B, C). Levels of 48 CAFs were measured by suspension bead multiplex assays (BioRad and EMD). Comparisons of Groups A v C (n=169 pairs) and Groups B v C (n=65 pairs) were by the two-sided, nonparametric Wilcoxon paired test, with p<0.05 significance for confirmation of previous CAF results.

Results: Prior chemotherapy duration (6.5mo, 6.7mo), and time from last chemotherapy dose to sample collection (1.3mo, 1.2 mo) were similar for Groups B and C, respectively. Results were available for 80% of the samples. Compared to Group A, Group B had reductions in multiple CAFs, including IL-8 (-38%, p<0.0001) and PDGF (-62%, p<0.0001). Commensurate with prior results, PlGF, Eotaxin and TRAIL were increased in Group C by 30% (p<0.0001), 23% (p=0.024) and 19% (p=0.008) respectively. Most CAF changes were attributable to chemotherapy alone. However, PlGF (-31%, p<0.0001) and TRAIL (+26%, p=0.037) significantly differed in Groups B v C. In group C compared to A, multiple changes were seen in the EGFR-axis including decreases in EGF (-52%, p=0.032), epiregulin (-25%, p=0.0023), and HB-EGF (-40%, p<0.0001) as well as an increase in sEGFR (+10%, p=0.004).

Conclusions: Most changes in CAFs after treatment with bevacizumab-containing chemotherapy appear to be due to chemotherapy alone and not attributable to anti-VEGF therapy, with several notable exceptions. Chemotherapy-induced changes in the EGFR-axis have not previously been described in mCRC and warrant further investigation.

[Table: see text]

A cytokine and angiogenic factor (CAF) plasma signature for selection of sorafenib (SR) therapy in patients (pts) with metastatic renal cell carcinoma (mRCC)

5114

Background: SR, an oral inhibitor of Raf kinase, RET-receptor (R), VEGFR-1, 2, and 3, PDGFR-β, FLT-3, and c-KIT tyrosine kinases, has been shown to prolong progression-free survival (PFS) in mRCC after cytokine failure. In a phase II trial, mRCC pts were randomized to first line treatment with SR vs. SR plus interferon (IFN) to assess whether combination therapy improved PFS. Both treatment arms showed similar outcomes (Tannir et al, ASCO. 2008). Here we investigated predictive and prognostic biomarkers in plasma. Methods: Pts received SR 400 mg PO BID or same dose SR plus IFN 0.5 MU SC BID. Plasma was collected from 69 pts at baseline (BL; SR 34, SR+IFN 35), 59 on day (D) 28, and 57 pts on D56. We used multiplex bead suspension arrays to measure concentrations of 54 CAFs, including VEGF, PDGFbb, EGF, HGF, MMP-9, and multiple chemokines and interleukins (IL). Osteopontin (OPN), soluble carbonic anhydrase 9 (sCA9), placental growth factor (PlGF), collagen type IV (ColIV) and sVEGFR-2 were measured by ELISA. The primary objective of this analysis was to establish a CAF signature based on a set of individual markers at BL with a significant and differential impact on the association between treatment arm and PFS. Results: Among 52 CAFs available at BL, higher than median EGF concentrations associated with poor outcome independently of treatment arm, whereas low IL-2 had the opposite effect (p = 0.003 for both). Only OPN showed a significant treatment by factor interaction at BL (p < 0.01), suggesting that OPN has a differential effect on PFS in the two arms. Pts with high OPN benefitted more from single agent SR (7.74 vs. 3.93 mos for the combination; p = 0.007), but no differences were found for those with low OPN. Lower than median on-treatment increases in sCA9 (D28, p = 0.01) and GRO-alpha (D56, p = 0.04) on SR only were also associated with a better outcome. A 6-marker CAF signature at BL containing OPN, sCA9, VEGF, sVEGFR-2, ColIV, and TRAIL demonstrated predictive value on PFS. Conclusions: A CAF signature showed potential value in predicting differential benefit from single agent SR vs. SR+IFN in mRCC. Broad-based screening of circulating CAFs may identify predictive and prognostic biomarkers in the context of clinical trials.

[Table: see text]

Plasma cytokine concentrations and quality of life in patients with non-small cell lung cancer in a phase II trial of first-line treatment with carboplatin-paclitaxel and/or vandetanib

9596

Background: A randomized phase II trial (JCO 26:5407–15, 2008) compared carboplatin-paclitaxel (CP) with vandetanib (VEGFR-EGFR inhibitor) monotherapy (V) and V plus CP (VCP) 1st-line for advanced NSCLC (N=181). PFS was superior for VCP vs CP (HR 0.76). We performed analyses of quality of life (QOL) and its correlations with plasma concentrations of cytokines and angiogenic factors (CAF) among the participants in this trial. Methods: QOL was serially measured by Functional Assessment of Cancer Therapy-Lung (FACT-L) and Trial Outcome Index (TOI) scores. Concentrations of 35 plasma CAFs were measured at baseline and multiple timepoints during treatment with multiplexed bead suspension arrays and ELISAs. We performed exploratory analyses for the following associations: (1) QOL with plasma CAF levels at baseline; (2) changes in QOL with changes in plasma CAF levels. Spearman correlation coefficient, log-rank test and mixed linear models were applied in the analyses. P-value < 0.05 was considered significant. Results: Baseline QOL and plasma samples were both available for 120 patients. Lower baseline FACT-L scores (inferior QOL) were associated with higher pre-treatment plasma levels of INF-γ, IL-1RA, IL-6, IL-12, IL-15, TNF-α, RANTES, MIG, MIP-1β, MMP-9, bFGF, VEGF and sVEGFR-2 (all P<0.05). Lower baseline TOI scores (inferior QOL) were also associated with higher pre-treatment plasma levels of multiple CAFs, including GCSF, HGF, INF-α, INF-γ, IL-2, IL-6, IL-8, IL-12, IL-15, TNF-α, bFGF, sVEGFR-2 and VEGF (all P<0.05). Among all patients, decreasing TOI scores post cycle 2 (HR=2.57 [1.28,5.17], P=0.008) and cycle 4 (HR=2.58 [1.01,6.56], P=0.049) were associated with increased progression risk. Trends for FACT-L were similar, but did not reach statistical significance. Rises in GCSF, HGF, IL-2, IL-8, IL-15, MCP-1, MIP-1β, and VEGF from baseline to post cycle 2 were associated with decreased FACT-L and/or TOI scores (all P<0.05). Conclusions: High plasma concentrations of multiple CAFs pre-treatment in patients with NSCLC correlated with inferior QOL, and rises in these factors during treatment were associated with worsening QOL. This work was funded in part by grant from ACS (FK).

[Table: see text]

Correlative analyses of plasma cytokine/angiogenic factor (C/AF) profile, gender and outcome in a randomized, three-arm, phase II trial of first-line vandetanib (VAN) and/or carboplatin plus paclitaxel (CP) for advanced non-small cell lung cancer (NSCLC)

7593

Background: VAN (ZD6474) is an oral inhibitor of VEGFR, EGFR and RET. In a phase II trial, 181 patients with advanced NSCLC were randomized to 1st-line treatment with VAN, CP or VAN + CP. Progression free survival (PFS) was prolonged for VAN + CP vs CP (Heymach et al, submitted for ASCO 2007). Exploratory subgroup analyses suggest gender differences in PFS benefit for VAN + CP vs CP (HR 0.47 in females vs 1.05 in males). We performed exploratory analyses of plasma levels of 35 C/AFs to investigate gender differences and potential prognostic or predictive markers. Methods: Plasma was collected at baseline (n = 123; VAN 55, CP 32, VAN + CP 36), day (D) 8 (n = 104), D22 (n = 95), and D43 (n = 83). We used multiplex bead assays to measure 33 plasma C/AFs, including VEGF, basic FGF, EGF, HGF, E-selectin, ICAM-1, MMP-9, multiple chemokines and interleukins (IL). Osteopontin and sVEGFR-2 were measured by ELISA. Cox models were applied on PFS to identify prognostic/predictive markers after rank transformation and adjusted for covariates. Results: Significant gender differences in baseline C/AF levels were seen for IL-15, IL-1RA, IL-2R, MIG, and MIP-1A (all higher in females, all p = 0.022). Controlling for gender and treatment, high baseline E-selectin (p = .01), IL-6 (p = 0.018), and IL-2R (p = 0.008) were adverse prognostic indicators for PFS. Controlling for gender, the tests for treatment by factor interactions (to assess whether treatment effect was different in patients with low and high C/AF levels) were significant for baseline HGF (p = 0.04) and IL-2R (p = 0.008). For both HGF and IL- 2R, low levels were associated with prolonged PFS in the VAN arm, but were not associated with differences in the CP or VAN + CP arms. Significant changes in VEGF (rise) and sVEGFR-2 (decrease) occurred with treatment in the VAN arm; IL12, IL-1RA, MMP-9 and MCP-1 changed in the CP and VAN + CP arms. Conclusions: There are gender differences in PFS benefit from VAN and in plasma C/AF profile. Several C/AFs were of prognostic value, whereas low HGF and IL-2R were predictive of benefit in the VAN but not CP and VAN + CP arms. These gender differences and markers warrant further investigation.

[Table: see text]

Once-daily intravenous busulfan given with fludarabine as conditioning for allogeneic stem cell transplantation: study of pharmacokinetics and early clinical outcomes

The availability of an i.v. form of busulfan (Bu) has prompted investigation of administration schedules other than the 4-times-daily dosage commonly used with oral Bu. We have studied an allogeneic stem cell transplantation (SCT) preparative regimen comprising fludarabine (FLU) 50 mg/m2 on days -6 to -2 plus i.v. Bu 3.2 mg/kg daily in a 3-hour infusion on days -5 to -2. The regimen was given to 70 patients aged 15 to 64 years (median, 41 years) with hematologic malignancy. Thirty-six patients (51%) had high-risk malignancy, 28 (40%) had unrelated or genotypically mismatched related donors (alternate donors [AD]) and 29 (41%) received bone marrow rather than blood as stem cell source. Acute GVHD prevention comprised antithymocyte globulin 4.5 mg/kg over 3 days pretransplantation, cyclosporin A, and short-course methotrexate with folinic acid. Hepatic toxicity was transient and there was no clinically diagnosed veno-occlusive disease. Grade II stomatitis occurred in 49 patients (70%) and hemorrhagic cystitis in 9 patients (13%). One patient with subtherapeutic phenytoin levels had a convulsion 8 hours after the third i.v. Bu dose, but no other neurotoxicity was apparent. Incidence of acute GVHD grades II to IV was 8% and incidence of grade III-IV was 3%, with no deaths from this cause. Actuarial incidence of chronic GVHD at 2 years is 38%. There were 2 cases of graft failure in unrelated donor BMT recipients, 1 of which was reversed by asecond transplantation. With a median follow-up of 16 months (range, 6-27 months), transplantation-related mortality at 100 days and 2 years was 2% and 5% for matched related donor (MRD) SCT and 8% and 19% for AD SCT, respectively (P = not significant). Relapse rates were 21% for 34 patients with acute myeloid leukemia (AML) in complete remission or chronic myeloid leukemia in chronic phase (low-risk), 66% for 19 patients with high-risk AML, and 18% for 17 patients with other active malignancy. Projected disease-free and overall survival rates at 2 years were 74% and 88% for low-risk disease, 26% and 37% for advanced AML, and 65% and 71% for other high-risk disease, respectively. Pharmacokinetic studies were done using 11 samples with the first and fourth doses of Bu. Kinetics were linear, and for the first and fourth doses, the half-lives were 2.60 +/- 0.44 and 2.57 +/- 0.36 hours, respectively. Clearances were 106.77 +/- 16.68 and 106.86 +/- 21.57 mL/min per m2, peak concentrations (Cmax) were 3.92 +/- 0.31 and 3.96 +/- 0.28 mcg/mL, and Bu areas under the plasma concentration versus time curve (AUC) were 4866.51 +/- 771.42 and 4980 +/- 882.80 microM x min, respectively. Bu was completely cleared within 24 hours and the day 4 pharmacokinetic values were very similar to those on day 1 for every patient. The cumulative AUC was comparable to the target range established for p.o. Bu. This regimen incorporating once-daily i.v. Bu is convenient to give, is relatively well tolerated, gives predictable blood levels, and deserves further study in circumstances in which cytoreduction as well as immune suppression is needed.

Purification and properties of Arabidopsis thaliana type 1 protein phosphatase (PP1)

The Arabidopsis thaliana type 1 protein phosphatase (PP1) catalytic subunit was released from its endogenous regulatory subunits by ethanol precipitation and purified by anion exchange and microcystin affinity chromatography. The enzyme was identified by MALDI-TOF mass spectrometry from a tryptic digest of the purified protein as a mixture of PP1 isoforms (TOPP 1-6) indicating that at least 4-6 of the eight known PP1 proteins are expressed in sufficient quantities for purification from A. thaliana suspension cells. The enzyme had a final specific activity of 8950 mU/mg using glycogen phosphorylase a as substrate, had a subunit molecular mass of 35 kDa as determined by SDS-PAGE and behaved as a monomeric protein of approx. 39 kDa on Superose 12 gel filtration chromatography. Similar to the mammalian type 1 protein phosphatases, the A. thaliana enzyme was potently inhibited by Inhibitor-2 (IC(50)=0.65 nM), tautomycin (IC(50)=0.06 nM), microcystin-LR (IC(50)=0.01 nM), nodularin (IC(50)=0.035 nM), calyculin A (IC(50)=0.09 nM), okadaic acid (IC(50)=20 nM) and cantharidin (IC(50)=60 nM). The enzyme was also inhibited by fostriecin (IC(50)=22 microM), NaF (IC(50)=2.1 mM), Pi (IC(50)=9.5 mM), and PPi (IC(50)=0.07 mM). Purification of the free catalytic subunit allowed it to be used to probe protein phosphatase holoenzyme complexes that were enriched on Q-Sepharose and a microcystin-Sepharose affinity matrix and confirmed several proteins to be PP1 targeting subunits.

Surface display of recombinant proteins on Bacillus subtilis spores

We developed a novel surface display system based on the use of bacterial spores. A protein of the Bacillus subtilis spore coat, CotB, was found to be located on the spore surface and used as fusion partner to express the 459-amino-acid C-terminal fragment of the tetanus toxin (TTFC). Western, dot blot and fluorescent-activated cell sorting analyses were used to monitor TTFC surface expression on purified spores. We estimated that more than 1.5 x 10(3) TTFC molecules were exposed on the surface of each spore and recognized by TTFC-specific antibodies. The efficient surface presentation of the heterologous protein, together with the simple purification procedure and the high stability and safety record of B. subtilis spores, makes this spore-based display system a potentially powerful approach for surface expression of bioactive molecules.

Requirement of co-factors for the ligand-mediated activity of the insect ecdysteroid receptor in yeast

In insects, a steroid hormone 20-hydroxyecdysone has an important role in regulating critical events such as development and reproduction. The action of 20-hydroxyecdysone is mediated by its binding to the ecdysteroid receptor (EcR), which requires a heterodimeric partner, ultraspiracle protein (USP), a homologue of the retinoid X receptor (RXR). The EcR-USP heterodimer represents a functional receptor complex capable of initiating transcription of early genes. Our goal was to establish a ligand-dependent transactivation system in yeast utilizing an insect EcR-USP heterodimer. This has been achieved using mosquito Aedes aegypti AaEcR-USP. Expression of AaEcR alone, but not USP, resulted in constitutive transcription of the ecdysone reporter gene coupled with the Drosophila heat shock protein-27 ecdysone response elements. Removal of the N-terminal A/B domain of AaEcR abolished its constitutive transcription. Constitutive transcription was also eliminated in the presence of its heterodimeric partner, AaUSPa, AaUSPb or mammalian RXR. This suggests that the A/B domain is essential for the EcR ligand-independent transactivation and its interaction with the yeast transcription complex. A ligand-mediated transactivation of Aa(Delta A/B)EcR-USP or Aa(Delta A/B)EcR-RXR heterodimers in response to an ecdysteroid agonist RH-5992 was observed only in the presence of GRIP1, a mouse co-activator. In the presence of a co-repressor, SMRT, Aa(Delta A/B)EcR-USP heterodimer exhibited a ligand-dependent repression activity. In addition, ligand-dependent transactivation systems for spruce budworm and fruit fly ecdysone receptors were also reported. This is the first report establishing the requirements of co-factors for a highly efficient ligand-dependent function of the insect EcR-USP in yeast. These findings open a way to study insect EcR-USP structure and function and to identify ligands that are specific for a certain group of insects, such as mosquitoes.

Reconstruction of ligand-dependent transactivation of Choristoneura fumiferana ecdysone receptor in yeast

Ecdysteroids play an important role in regulating development and reproduction in insects. Interaction of 20-hydroxyecdysone (20E) with ecdysone receptor (EcR) as a heterodimer with ultraspiracle (USP) protein triggers the activation of 20E-responsive genes. In this paper we describe a ligand-mediated transactivation system in yeast using the spruce budworm Choristoneura fumiferana ecdysone receptor (CfEcR). Coexpression of C. fumiferana USP (CfUSP) with CfEcR in yeast led to constitutive transcription of the reporter gene. However, deletion of the A/B domain of CfUSP abolished constitutive activity observed for the CfUSP:CfEcR complex. Replacement of USP with its mammalian homolog retinoid X receptors (RXRs) abolished the constitutive activity of the heterodimer but it did not restore EcR ligand-mediated transactivation. These data suggest that USP and its A/B domain play a role in the constitutive function of CfEcR:USP in yeast. A ligand-mediated transactivation was observed when GRIP1, a mouse coactivator gene, was added to EcR:RXR or EcR:DeltaA/BUSP complexes. Deletion of the A/B domain of EcR in the context of DeltaA/BEcR:RXR:GRIP1 or DeltaA/BEcR:DeltaA/BUSP:GRIP1 dramatically improved the ligand-dependent transactivation. This is the first example of highly efficient ligand-dependent transactivation of insect EcR in yeast. Analysis of transactivation activity of different ecdysteroidal compounds showed that the yeast system remarkably mimics the response observed in insect tissue culture cells and whole insect systems. The results open the way to develop assays that can be used to screen novel species-specific ecdysone agonist/antagonist insecticides.

Physiologically based pharmacokinetic modeling of benzene metabolism in mice through extrapolation from in vitro to in vivo

Benzene (C6H6) is a highly flammable, colorless liquid. Ubiquitous exposures result from its presence in gasoline vapors, cigarette smoke, and industrial processes. Benzene increases the incidence of leukemia in humans when they are exposed to high doses for extended periods; however, leukemia risks in humans at low exposures are uncertain. The exposure-dose-response relationship of benzene in humans is expected to be nonlinear because benzene undergoes a series of metabolic transformations, detoxifying and activating, in the liver, resulting in multiple metabolites that exert toxic effects on the bone marrow. We developed a physiologically based pharmacokinetic model for the uptake and elimination of benzene in mice to relate the concentration of inhaled and orally administered benzene to the tissue doses of benzene and its key metabolites, benzene oxide, phe nol, and hydroquinone. As many parameter values as possible were taken from the literature; in particular, metabolic parameters obtained from in vitro studies with mouse liver were used since comparable parameters are also available for humans. Parameters estimated by fitting the model to published data were first-order rate constants for pathways lacking in vitro data and the concentrations of microsomal and cytosolic protein, which effectively alter overall enzyme activity. The model was constrained by using the in vitro metabolic parameters (maximum velocities, first-order rate constants, and saturation parameters), and data from multiple laboratories and experiments were used. Despite these constraints and sources of variability, the model simulations matched the data reasonably well in most cases, showing that in vitro metabolic constants can be successfully extrapolated to predict in vivo data for benzene metabolism and dosimetry. Therefore in vitro metabolic constants for humans can subsequently be extrapolated to predict the dosimetry of benzene and its metabolites in humans. This will allow us to better estimate the risks of adverse effects from low-level benzene exposures.

Acute safety and pharmacokinetics of intravenous busulfan when used with oral busulfan and cyclophosphamide as pretransplantation conditioning therapy: a phase I study

The unpredictable intestinal absorption and erratic bioavailability of oral busulfan (Bu) has limited the drug's use in high-dose pretransplantation conditioning therapy. To standardize drug delivery, we solubilized Bu for parenteral use. This new intravenous (i.v.) Bu formulation was combined with oral Bu and cyclophosphamide (Cy) to evaluate (1) the human acute toxicity of i.v. Bu and its solvent system and (2) the pharmacokinetics of Bu in patients undergoing hematopoietic progenitor cell transplantation (HPCT). One dose of i.v. Bu (escalating from 0.08 to 0.8 mg/kg) was given over 2 hours by pump; 6 hours later, an oral Bu regimen was begun, consisting of 1 mg/kg every 6 hours for 15 doses, followed by Cy, 60 mg/kg daily for 2 days. After 1 day of rest, HPCT was performed. The i.v. Bu dose was well tolerated and did not produce any acute toxicity reaction that could be attributed to the solvent system of dimethylacetamide and polyethylene glycol (PEG)-400. All observed treatment-related toxicity was as would be expected after high-dose oral Bu plus Cy. When the i.v. Bu was used as reference solution, the pharmacokinetic analysis indicated an average bioavailability of oral high-dose Bu of 69%, ranging from <10% to virtually 100%. Further, the 2-hour infusion of i.v. Bu gave a time to maximum plasma concentration following drug administration similar to that of oral Bu (2 hours and 1.8 hours, respectively), and i.v. Bu had a clearance similar to that of oral Bu. Based on the data in this study, we suggest that the optimal (starting) dose of i.v. Bu (in combination with Cy) in our forthcoming phase 2 trial should be on the order of 0.8 mg/kg to target an area under the curve (AUC) of 1100 to 1200 micromol/L per minute. This would secure myeloablation and engraftment but save the vast majority of patients from the increased risk of serious hepatic veno-occlusive disease that has been reported when the AUC level exceeds 1500 micromol/L per minute. Bu administration via the i.v. route will assure complete bioavailability and reliable systemic drug exposure with more predictable blood levels and, therefore, possibly lower the risks for serious/life-threatening toxicity, graft rejection, and recurrent leukemia.

Clinical studies of angiogenesis inhibitors: the University of Texas MD Anderson Center Trial of Human Endostatin

Most solid-tumor malignancies remain incurable. Novel agents that target and counteract biologic mechanisms are now being developed. It is hoped that these drugs will allow for more effective, less toxic cancer treatments and long-term maintenance approaches. One important class of agents functions by an anti-angiogenic mechanism, targeting the blood vessel supply of the tumor and inhibiting tumor growth. Several principles are common to these new agents. First, because many of these agents are growth-inhibiting molecules that work exclusively against the tumor vasculature, single agents will have little effect on tumor size in advanced disease. Second, because these agents are relatively non-toxic, they are unlikely to induce the side effects associated with chemotherapy. Because endothelial cells seldom divide in a human host, anti-angiogenic compounds are expected to produce little toxicity. Third, most of these agents work synergistically with chemotherapy and/or radiotherapy. Ironically, combining these relatively non-toxic agents with chemotherapy often produces the toxicities usually associated with anticancer regimens. Anti-angiogenic agents might ultimately be studied in minimal disease. Clinical studies must demonstrate that these agents affect tumor vasculature, and phase I trials should include built-in surrogate endpoints. This article defines the general principles of anti-angiogenic drug action and explains how these principles have been used to design a phase I trial of human endostatin.

Individualizing high-dose oral busulfan: prospective dose adjustment in a pediatric population undergoing allogeneic stem cell transplantation for advanced hematologic malignancies

We investigated whether adjusting the oral busulfan (BU) dosage on the basis of early pharmacokinetic data to achieve a targeted drug exposure could reduce transplant-related complications in children with advanced hematologic malignancies. Twenty-five children received a preparative regimen consisting of thiotepa (250 mg/m2 i.v. daily for 3 days), BU (40 mg/m2 per dose p.o. every 6 h for 12 doses), and cyclophosphamide (60 mg/kg i.v. daily for 2 days) and then underwent allogeneic stem cell transplantation. Busulfan clearance and area under concentration time-curve (AUC) were determined after the first dose using a one-compartment pharmacokinetic (PK) model with first-order absorption. The initial PK analysis was successfully completed after the first BU dose in 21 patients (84%). A final AUC of 1000-1500 microM x min/dose was targeted and subsequent doses were modified as necessary to achieve this value. Fourteen of the 25 patients (56%) required dose adjustment. Follow-up PK analysis was completed in 21 patients and 16 of these achieved the targeted BU exposure for the course of therapy. Interpatient variability in BU clearance was high (up to five-fold). The most frequent regimen-related toxicities were cutaneous and gastrointestinal (stomatitis and diarrhea). Only one patient developed hepatic veno-occlusive disease. Our study demonstrates the feasibility of adjusting the oral BU dose in individual pediatric patients. Although toxicity associated with BU seemed to be reduced, this conclusion is tempered by the fact that the overall regimen-related toxicity (RRT) remains substantial and reflected the effects of all agents used in the preparative regimen.

Stability of the human respiratory control system. I. Analysis of a two-dimensional delay state-space model

A number of mathematical models of the human respiratory control system have been developed since 1940 to study a wide range of features of this complex system. Among them, periodic breathing (including Cheyne-Stokes respiration and apneustic breathing) is a collection of regular but involuntary breathing patterns that have important medical implications. The hypothesis that periodic breathing is the result of delay in the feedback signals to the respiratory control system has been studied since the work of Grodins et al. in the early 1950's [12]. The purpose of this paper is to study the stability characteristics of a feedback control system of five differential equations with delays in both the state and control variables presented by Khoo et al. [17] in 1991 for modeling human respiration. The paper is divided in two parts. Part I studies a simplified mathematical model of two nonlinear state equations modeling arterial partial pressures of O2 and CO2 and a peripheral controller. Analysis was done on this model to illuminate the effect of delay on the stability. It shows that delay dependent stability is affected by the controller gain, compartmental volumes and the manner in which changes in the ventilation rate is produced (i.e., by deeper breathing or faster breathing). In addition, numerical simulations were performed to validate analytical results. Part II extends the model in Part I to include both peripheral and central controllers. This, however, necessitates the introduction of a third state equation modeling CO2 levels in the brain. In addition to analytical studies on delay dependent stability, it shows that the decreased cardiac output (and hence increased delay) resulting from the congestive heart condition can induce instability at certain control gain levels. These analytical results were also confirmed by numerical simulations.

Stability of the human respiratory control system. II. Analysis of a three-dimensional delay state-space model

A number of mathematical models of the human respiratory control system have been developed since 1940 to study a wide range of features of this complex system. Among them, periodic breathing (including Cheyne-Stokes respiration and apneustic breathing) is a collection of regular but involuntary breathing patterns that have important medical implications. The hypothesis that periodic breathing is the result of delay in the feedback signals to the respiratory control system has been studied since the work of Grodins et al. in the early 1950's [1]. The purpose of this paper is to study the stability characteristics of a feedback control system of five differential equations with delays in both the state and control variables presented by Khoo et al. [4] in 1991 for modeling human respiration. The paper is divided in two parts. Part I studies a simplified mathematical model of two nonlinear state equations modeling arterial partial pressures of O2 and CO2 and a peripheral controller. Analysis was done on this model to illuminate the effect of delay on the stability. It shows that delay dependent stability is affected by the controller gain, compartmental volumes and the manner in which changes in the ventilation rate is produced (i.e., by deeper breathing or faster breathing). In addition, numerical simulations were performed to validate analytical results. Part II extends the model in Part I to include both peripheral and central controllers. This, however, necessitates the introduction of a third state equation modeling CO2 levels in the brain. In addition to analytical studies on delay dependent stability, it shows that the decreased cardiac output (and hence increased delay) resulting from the congestive heart condition can induce instability at certain control gain levels. These analytical results were also confirmed by numerical simulations.

Novel marine-derived anticancer agents: a phase I clinical, pharmacological, and pharmacodynamic study of dolastatin 10 (NSC 376128) in patients with advanced solid tumors

Dolastatin (DOLA)-10 is a pentapeptide isolated from the mollusc Dolabella auricularia with clinically promising antitumor activity documented in various in vitro and in vivo tumor models. The objectives of this Phase I study were to determine the maximum tolerated dose, evaluate toxic effects, and document any antitumor activity of this novel agent. Using an electrospray ionization mass spectroscopy system, we also characterized the clinical pharmacokinetics, pharmacodynamics, and metabolism of DOLA-10. The maximum tolerated dose was reached at 300 microg/m2. Granulocytopenia, the dose-limiting toxicity, was documented in 33% of the patients treated at that dose level. There were no episodes of thrombocytopenia or severe anemia (Hgb < 8), and no major nonhematological toxicity was observed. Stabilization of tumor growth was observed in four patients, but no objective responses were seen. Whereas a two-compartment model described the DOLA-10 plasma concentration-time data reasonably well, a three-compartment model consistently performed better. After a rapid distribution phase, DOLA-10 plasma levels declined with mean beta and gamma half-lives of 0.99 and 18.9 h, respectively. Significant interpatient and intrapatient variability in DOLA-10 plasma clearances was observed. The mean area under the concentration-time curve increased proportionally as the dose was escalated, but there was significant overlap between dose levels. The area under the concentration-time curve and the percentage of decline in neutrophils were correlated. A single DOLA-10 metabolite was detected in five patients. Unlike the in vitro studies of DOLA-10, the principal metabolite detected was an N-demethyl derivative, confirmed by mass spectroscopy. In all five subjects, the concentration of this metabolite never exceeded 2% of the simultaneously measured parent drug concentration. The available preclinical, pharmacological, and clinical data suggest that further study of escalated DOLA-10 dosing with cytokine support is warranted.

Compound heterozygosity for novel splice site mutations in the BPAG2/COL17A1 gene underlies generalized atrophic benign epidermolysis bullosa

Generalized atrophic benign epidermolysis bullosa, GABEB (OMIM# 226650), is a nonlethal variant of epidermolysis bullosa with autosomal recessive inheritance pattern. The pathogenesis of this disorder can be caused by mutations affecting two different gene/protein systems. Most of the mutations have been identified in the BPAG2/COL17A1 gene encoding a hemidesmosomal transmembrane protein, the 180 kDa bullous pemphigoid antigen (BP180), also known as type XVII collagen. The minority of the mutations are localized in the LAMB3 gene encoding the beta3 polypeptide of laminin 5. In In this study we describe a GABEB patient who showed absent expression of BP180 in the cultured keratinocytes as well as in the skin. The patient was a compound heterozygote for two different splice site mutations, 3053-1G-->C and 3871+1G-->C, affecting the extra-cellular domain of the protein. These mutations resulted in multiple aberrant splice variants, three of them causing premature termination codons for translation. This case, dealing with out-of-frame splice site mutations in BPAG2/COL17A1, attests to the molecular heterogeneity of GABEB.

A novel role in DNA metabolism for the binding of Fen1/Rad27 to PCNA and implications for genetic risk

Fen1/Rad27 nuclease activity, which is important in DNA metabolism, is stimulated by proliferating cell nuclear antigen (PCNA) in vitro. The in vivo role of the PCNA interaction was investigated in the yeast Rad27. A nuclease-defective rad27 mutation had a dominant-negative effect that was suppressed by a mutation in the PCNA binding site, thereby demonstrating the importance of the Rad27-PCNA interaction. The PCNA-binding defect alone had little effect on mutation, recombination, and the methyl methanesulfonate (MMS) response in repair-competent cells, but it greatly amplified the MMS sensitivity of a rad51 mutant. Furthermore, the PCNA binding mutation resulted in lethality when combined with a homozygous or even a heterozygous pol3-01 mutation in the 3'-->5' exonuclease domain of DNA polymerase delta. These results suggest that phenotypically mild polymorphisms in DNA metabolic proteins can have dramatic consequences when combined.

Sex-related immune changes in young mice

Here we describe changes in selected immune parameters related to age and sex in young mice. We focused on the T cell compartment and studied thymuses and spleens from mice 3 to 9 weeks of age in order to bracket the time period around murine puberty. With regard to distribution of immune cells, no significant sex-related changes were seen in thymocyte expression of CD3, CD4, CD8, or CD4/CD8 or splenocyte expression of CD3, CD4, CD8, or CD45R/B220, a pan B cell marker. For splenocytes, significantly more cells were positive for CD3 in older (6-9 week old) compared with younger (3-4 week old) mice. Splenocyte and thymocyte cell proliferation as measured by DNA synthesis in response to in vitro mitogens was compared for cells from male and female mice over the ages studied. Thymocyte proliferation was not related to age or sex of the mice. For splenocytes of the youngest mice (3 weeks old), the response to a cell surface-receptor-independent mitogenic combination of phorbol ester and ionomycin induced a significantly greater response in cells from female mice compared with male mice. This trend was reversed for mice of 4-6 weeks of age, where the response by splenocytes from males was significantly greater than that by cells from females. For mice 7-8 weeks of age, splenocytes from female mice responded significantly less to stimulation by antibody to CD3, a component of the T-cell receptor. Our results demonstrate that depending on the assays employed, sexual dimorphism in the immune system may be demonstrated prior to puberty.

Genetic factors affecting the impact of DNA polymerase delta proofreading activity on mutation avoidance in yeast

Base selectivity, proofreading, and postreplication mismatch repair are important for replication fidelity. Because proofreading plays an important role in error correction, we have investigated factors that influence its impact in the yeast Saccharomyces cerevisiae. We have utilized a sensitive mutation detection system based on homonucleotide runs of 4 to 14 bases to examine the impact of DNA polymerase delta proofreading on mutation avoidance. The contribution of DNA polymerase delta proofreading on error avoidance was found to be similar to that of DNA polymerase epsilon proofreading in short homonucleotide runs (A4 and A5) but much greater than the contribution of DNA polymerase epsilon proofreading in longer runs. We have identified an intraprotein interaction affecting mutation prevention that results from mutations in the replication and the proofreading regions, resulting in an antimutator phenotype relative to a proofreading defect. Finally, a diploid strain with a defect in DNA polymerase delta proofreading exhibits a higher mutation rate than a haploid strain. We suggest that in the diploid population of proofreading defective cells there exists a transiently hypermutable fraction that would be inviable if cells were haploids.

Azimilide dihydrochloride: a unique class III antiarrhythmic agent

The introduction of class III (Vaughn Williams classification) antiarrhythmic agents has improved the available drug treatment modalities for managing cardiac supraventricular and ventricular tachyarrhythmia. An appreciation of the importance of the delayed rectifier potassium current in the pathogenesis of various cardiac arrhythmias has led to the development of azimilide, an oral type III potassium channel blocker agent that blocks both the rapid activating component (I(kr), common to sotalol, amiodarone, and ibutilide) and the slow activating component (I(ks), a unique action of azimilide) of the delayed rectifier potassium current. Both preclinical and clinical studies have demonstrated the efficacy of azimilide and its safety in the management of supraventricular and ventricular tachyarrhythmia. Azimilide also is being studied in a worldwide multicenter trial for prevention of sudden cardiac death in patients after myocardial infarction. Azimilide soon will become available for clinical use as a treatment for preserving normal sinus rhythm in patients with atrial fibrillation and paroxysmal atrial tachycardia.

Mutator phenotypes of yeast strains heterozygous for mutations in the MSH2 gene

Heterozygosity for germ-line mutations in the DNA mismatch repair gene MSH2 predisposes humans to cancer. Here we use a highly sensitive reporter to describe a spontaneous mutator phenotype in diploid yeast cells containing a deletion of only one MSH2 allele. We also identify five MSH2 missense mutations that have dominant mutator effects in heterozygous cells when expressed at normal levels from the natural MSH2 promoter. For example, a 230-fold mutator effect is observed in an MSH2/msh2 diploid strain in which Gly693, which is invariant in MutS homologs and involved in ATP hydrolysis, is changed to alanine. DNA binding data suggest that mismatch repair is suppressed by binding of a mutant Msh2-Msh6 heterodimer to a mismatch with subsequent inability to dissociate from the mismatch in the presence of ATP. A dominant mutator effect also is observed in yeast when Gly693 is changed to serine. An early onset colorectal tumor is heterozygous for the analogous Gly --> Ser mutation in hMSH2, and a second hMSH2 mutation was not found, suggesting that this missense mutation may predispose to cancer via a dominant mutator effect. The mutator effects of the deletion mutant and the Gly --> Ala missense mutant in yeast MSH2 are enhanced by heterozygosity for a missense mutation in DNA polymerase delta that reduces its proofreading activity but is not a mutator in the heterozygous state. The synergistic effects of heterozygosity for mutations in two different genes that act in series to correct replication errors may be relevant to cancer predisposition.

The 3'-->5' exonucleases of DNA polymerases delta and epsilon and the 5'-->3' exonuclease Exo1 have major roles in postreplication mutation avoidance in Saccharomyces cerevisiae

Replication fidelity is controlled by DNA polymerase proofreading and postreplication mismatch repair. We have genetically characterized the roles of the 5'-->3' Exo1 and the 3'-->5' DNA polymerase exonucleases in mismatch repair in the yeast Saccharomyces cerevisiae by using various genetic backgrounds and highly sensitive mutation detection systems that are based on long and short homonucleotide runs. Genetic interactions were examined among DNA polymerase epsilon (pol2-4) and delta (pol3-01) mutants defective in 3'-->5' proofreading exonuclease, mutants defective in the 5'-->3' exonuclease Exo1, and mismatch repair mutants (msh2, msh3, or msh6). These three exonucleases play an important role in mutation avoidance. Surprisingly, the mutation rate in an exo1 pol3-01 mutant was comparable to that in an msh2 pol3-01 mutant, suggesting that they participate directly in postreplication mismatch repair as well as in other DNA metabolic processes.