Wild-Type KRAS Is Required for Panitumumab Efficacy in Patients With Metastatic Colorectal Cancer

PURPOSE

Panitumumab, a fully human antibody against the epidermal growth factor receptor (EGFR), has activity in a subset of patients with metastatic colorectal cancer (mCRC). Although activating mutations in KRAS, a small G-protein downstream of EGFR, correlate with poor response to anti-EGFR antibodies in mCRC, their role as a selection marker has not been established in randomized trials.

PATIENTS AND METHODS

KRAS mutations were detected using polymerase chain reaction on DNA from tumor sections collected in a phase III mCRC trial comparing panitumumab monotherapy to best supportive care (BSC). We tested whether the effect of panitumumab on progression-free survival (PFS) differed by KRAS status.

RESULTS

KRAS status was ascertained in 427 (92%) of 463 patients (208 panitumumab, 219 BSC). KRAS mutations were found in 43% of patients. The treatment effect on PFS in the wild-type (WT) KRAS group (hazard ratio [HR], 0.45; 95% CI: 0.34 to 0.59) was significantly greater (P < .0001) than in the mutant group (HR, 0.99; 95% CI, 0.73 to 1.36). Median PFS in the WT KRAS group was 12.3 weeks for panitumumab and 7.3 weeks for BSC. Response rates to panitumumab were 17% and 0%, for the WT and mutant groups, respectively. WT KRAS patients had longer overall survival (HR, 0.67; 95% CI, 0.55 to 0.82; treatment arms combined). Consistent with longer exposure, more grade III treatment-related toxicities occurred in the WT KRAS group. No significant differences in toxicity were observed between the WT KRAS group and the overall population.

CONCLUSION

Panitumumab monotherapy efficacy in mCRC is confined to patients with WT KRAS tumors. KRAS status should be considered in selecting patients with mCRC as candidates for panitumumab monotherapy.

Limited differential expression of miRNAs and other small RNAs in LPS-stimulated human monocytes

Monocytes are a distinct subset of myeloid cells with diverse functions in early inflammatory immune modulation. While previous studies have surveyed the role of miRNA regulation on different myeloid cell lines and primary cultures, the time-dependent kinetics of inflammatory stimulation on miRNA expression and the relationship between miRNA-to-target RNA expression have not been comprehensively profiled in monocytes. In this study, we use next-generation sequencing and RT-PCR assays to analyze the non-coding small RNA transcriptome of unstimulated and lipopolysaccharide (LPS)-stimulated monocytes at 6 and 24 hours. We identified a miRNA signature consisting of five mature miRNAs (hsa-mir-146a, hsa-mir-155, hsa-mir-9, hsa-mir-147b, and hsa-mir-193a) upregulated by LPS-stimulated monocytes after 6 hours and found that most miRNAs were also upregulated after 24 hours of stimulation. Only one miRNA gene was down-regulated and no other small RNAs were found dysregulated in monocytes after LPS treatment. In addition, novel tRNA-derived fragments were also discovered in monocytes although none showed significant changes upon LPS stimulation. Interrogation of validated miRNA targets by transcriptomic analysis revealed that absolute expression of most miRNA targets implicating in innate immune response decreased over time in LPS-stimulated monocytes although their expression patterns along the treatment were heterogeneous. Our findings reveal a potential role by which selective miRNA upregulation and stable expression of other small RNAs enable monocytes to develop finely tuned cellular responses during acute inflammation.

Note. Pollen Analysis and Antibacterial Activity of Spanish Honeys

Antibacterial activity of twenty-five samples of honey from different botanical origin was evaluated. Staphylococcus aureus ATCC 25923 was used as the resistant microorganism. Pollen analysis revealed different botanical origins: Labiatae, rosemary, eucalyptus, heather and multifloral. The pH and acidity values were in the normal range, except for four samples that showed acidity values over 40 meq/kg, but none exhibited a state of fermentation. We have not found correlation between antibacterial activity and free acidity in the samples. Labiatae and rosemary honeys have exhibited the largest inhibition against Staphylococcus aureus ATCC, conversely to heather honeys, which showed lowest inhibition ability against this microorganism. Our results may indicate the presence of antimicrobial agents in Labiatae and rosemary honeys that have inhibited the growth of Staphylococcus aureus ATCC. Likewise, the free acids of heather honeys have not shown inhibitory activity over this microorganism.

The Candidate Neuroprotective Agent Artemin Induces Autonomic Neural Dysplasia without Preventing Peripheral Nerve Dysfunction

Artemin (ART) signals through the GFR α—3/RET receptor complex to support sympathetic neuron development. Here we show that ART also influences autonomic elements in adrenal medulla and enteric and pelvic ganglia. Transgenic mice over-expressing Art throughout development exhibited systemic autonomic neural lesions including fusion of adrenal medullae with adjacent paraganglia, adrenal medullary dysplasia, and marked enlargement of sympathetic (superior cervical and sympathetic chain ganglia) and parasympathetic (enteric, pelvic) ganglia. Changes began by gestational day 12.5 and formed progressively larger masses during adulthood. Art supplementation in wild type adult mice by administering recombinant protein or an Art-bearing retroviral vector resulted in hyperplasia or neuronal metaplasia at the adrenal corticomedullary junction. Expression data revealed that Gfr α—3 is expressed during development in the adrenal medulla, sensory and autonomic ganglia and their projections, while Art is found in contiguous mesenchymal domains (especially skeleton) and in certain nerves. Intrathecal Art therapy did not reduce hypalgesia in rats following nerve ligation. These data (1) confirm that ART acts as a differentiation factor for autonomic (chiefly sympathoadrenal but also parasympathetic) neurons, (2) suggest a role for ART overexpression in the genesis of pheochromocytomas and paragangliomas, and (3) indicate that ART is not a suitable therapy for peripheral neuropathy.

Haploinsufficiency of the Insulin Receptor in the Presence of a Splice-Site Mutation in Ppp2r2a Results in a Novel Digenic Mouse Model of Type 2 Diabetes

Insulin resistance in mice typically does not manifest as diabetes due to multiple compensatory mechanisms. Here, we present a novel digenic model of type 2 diabetes in mice heterozygous for a null allele of the insulin receptor and an N-ethyl-N-nitrosourea-induced alternative splice mutation in the regulatory protein phosphatase 2A (PP2A) subunit PPP2R2A. Inheritance of either allele independently results in insulin resistance but not overt diabetes. Doubly heterozygous mice exhibit progressive hyperglycemia, hyperinsulinemia, and impaired glucose tolerance from 12 weeks of age without significant increase in body weight. Alternative splicing of Ppp2r2a decreased PPP2R2A protein levels. This reduction in PPP2R2A containing PP2A phosphatase holoenzyme was associated with decreased serine/threonine protein kinase AKT protein levels. Ultimately, reduced insulin-stimulated phosphorylated AKT levels were observed, a result that was confirmed in Hepa1-6, C2C12, and differentiated 3T3-L1 cells knocked down using Ppp2r2a small interfering RNAs. Altered AKT signaling and expression of gluconeogenic genes in the fed state contributed to an insulin resistance and hyperglycemia phenotype. This model demonstrates how genetic changes with individually small phenotypic effects interact to cause diabetes and how differences in expression of hypomorphic alleles of PPP2R2A and potentially other regulatory proteins have deleterious effects and may therefore be relevant in determining diabetes risk.

A mutation in Ampd2 is associated with nephrotic syndrome and hypercholesterolemia in mice

Background

Previously, we identified three loci affecting HDL-cholesterol levels in a screen for ENU-induced mutations in mice and discovered two mutated genes. We sought to identify the third mutated gene and further characterize the mouse phenotype.

Methods

We engaged, DNA sequencing, gene expression profiling, western blotting, lipoprotein characterization, metabolomics assessment, histology and electron microscopy in mouse tissues.

Results

We identify the third gene as Ampd2, a liver isoform of AMP Deaminase (Ampd), a central component of energy and purine metabolism pathways. The causative mutation was a guanine-to-thymine transversion resulting in an A341S conversion in Ampd2. Ampd2 homozygous mutant mice exhibit a labile hypercholesterolemia phenotype, peaking around 9 weeks of age (251 mg/dL vs. wildtype control at 138 mg/dL), and was evidenced by marked increases in HDL, VLDL and LDL. In an attempt to determine the molecular connection between Ampd2 dysfunction and hypercholesterolemia, we analyzed hepatic gene expression and found the downregulation of Ldlr, Hmgcs and Insig1 and upregulation of Cyp7A1 genes. Metabolomic analysis confirmed an increase in hepatic AMP levels and a decrease in allantoin levels consistent with Ampd2 deficiency, and increases in campesterol and β-sitosterol. Additionally, nephrotic syndrome was observed in the mutant mice, through proteinuria, kidney histology and effacement and blebbing of podocyte foot processes by electron microscopy.

Conclusion

In summary we describe the discovery of a novel genetic mouse model of combined transient nephrotic syndrome and hypercholesterolemia, resembling the human disorder.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-167) contains supplementary material, which is available to authorized users.

Sclerostin expression is induced by BMPs in human Saos-2 osteosarcoma cells but not via direct effects on the sclerostin gene promoter or ECR5 element

Sclerostin is a secreted inhibitor of Wnt signaling and plays an essential role in the regulation of bone mass. The expression of sclerostin is largely restricted to osteocytes although its mode of transcriptional regulation is not well understood. We observed regulated expression of sclerostin mRNA and protein that was directly correlated with the mineralization response in cultured human Saos-2 osteosarcoma cells and rat primary calvarial cells. Sclerostin mRNA and protein levels were increased following treatment of cells with BMP2, BMP4 and BMP7. Analysis of deletion mutants from the -7.4 kb upstream region of the human sclerostin promoter did not reveal any specific regions that were responsive to BMPs, Wnt3a, PTH, TGFβ1 or Activin A in Saos-2 cells. The downstream ECR5 element did not show enhancer activity in Saos-2 cells and also was not affected when Saos-2 cells were treated with BMPs or PTH. Genome-wide microarray analysis of Saos-2 cells treated with BMP2 showed significant changes in expression of several transcription factors with putative consensus DNA binding sites in the region of the sclerostin promoter. However, whereas most factors tested showed either a range of inhibitory activity (DLX family, MSX2, HEY1, SMAD6/7) or lack of activity on the sclerostin promoter including SMAD9, only MEF2B showed a positive effect on both the promoter and ECR5 element. These results suggest that the dramatic induction of sclerostin gene expression by BMPs in Saos-2 cells occurs indirectly and is associated with late stage differentiation of osteoblasts and the mineralization process.

FusionMap: detecting fusion genes from next-generation sequencing data at base-pair resolution

MOTIVATION

Next generation sequencing technology generates high-throughput data, which allows us to detect fusion genes at both transcript and genomic levels. To detect fusion genes, the current bioinformatics tools heavily rely on paired-end approaches and overlook the importance of reads that span fusion junctions. Thus there is a need to develop an efficient aligner to detect fusion events by accurate mapping of these junction-spanning single reads, particularly when the read gets longer with the improvement in sequencing technology.

RESULTS

We present a novel method, FusionMap, which aligns fusion reads directly to the genome without prior knowledge of potential fusion regions. FusionMap can detect fusion events in both single- and paired-end datasets from either RNA-Seq or gDNA-Seq studies and characterize fusion junctions at base-pair resolution. We showed that FusionMap achieved high sensitivity and specificity in fusion detection on two simulated RNA-Seq datasets, which contained 75 nt paired-end reads. FusionMap achieved substantially higher sensitivity and specificity than the paired-end approach when the inner distance between read pairs was small. Using FusionMap to characterize fusion genes in K562 chronic myeloid leukemia cell line, we further demonstrated its accuracy in fusion detection in both single-end RNA-Seq and gDNA-Seq datasets. These combined results show that FusionMap provides an accurate and systematic solution to detecting fusion events through junction-spanning reads.

AVAILABILITY

FusionMap includes reference indexing, read filtering, fusion alignment and reporting in one package. The software is free for noncommercial use at (http://www.omicsoft.com/fusionmap).

Motesanib inhibits Kit mutations associated with gastrointestinal stromal tumors

Background

Activating mutations in Kit receptor tyrosine kinase or the related platelet-derived growth factor receptor (PDGFR) play an important role in the pathogenesis of gastrointestinal stromal tumors (GIST).

Methods

This study investigated the activity of motesanib, an inhibitor of vascular endothelial growth factor receptors (VEGFR) 1, 2, and 3; PDGFR; and Kit, against primary activating Kit mutants and mutants associated with secondary resistance to imatinib. Single- and double-mutant isoforms of Kit were evaluated for their sensitivity to motesanib or imatinib in autophosphorylation assays and in Ba/F3 cell proliferation assays.

Results

Motesanib inhibited Kit autophosphorylation in CHO cell lines expressing primary activating mutations in exon 9 (AYins503-504, IC₅₀ = 18 nM) and exon 11 (V560 D, IC₅₀ = 5 nM; Δ552-559, IC₅₀ = 1 nM). Motesanib also demonstrated activity against kinase domain mutations conferring imatinib resistance (V560D/V654A, IC₅₀ = 77 nM; V560D/T670I, IC₅₀ = 277 nM; Y823 D, IC₅₀ = 64 nM) but failed to inhibit the imatinib-resistant D816V mutant (IC₅₀ > 3000 nM). Motesanib suppressed the proliferation of Ba/F3 cells expressing Kit mutants with IC₅₀ values in good agreement with those observed in the autophosphorylation assays.

Conclusions

In conclusion, our data suggest that motesanib possesses inhibitory activity against primary Kit mutations and some imatinib-resistant secondary mutations.

A comparability study of 5 commercial KRAS tests

BACKGROUND

Activating mutations in the KRAS gene occur frequently in human tumors, including colorectal carcinomas; most mutations occur in codons 12 and 13. Mutations in KRAS have been associated with poor response to anti-epidermal growth factor receptor antibodies. Therefore, an accurate and readily available analysis of KRAS mutational status is needed. The aim of this study was to evaluate concordance between KRAS assays performed by 6 different laboratories.

METHODS

Forty formalin-fixed paraffin-embedded colorectal cancer tumor samples were obtained. Sample sections were submitted for KRAS mutation analysis to 5 independent commercial laboratories (Agencourt, Gentris, Genzyme, HistoGeneX, and Invitek) and to the Amgen DNA Sequencing Laboratory for direct polymerase chain reaction sequencing. The assay used by Invitek is no longer commercially available and has been replaced by an alternative technique. Results from the commercial services were compared with those from Amgen direct sequencing by kappa statistics.

RESULTS

KRAS mutations were observed in codon 12 and/or 13 in 20 of 40 (50%) samples in Amgen direct sequencing assays. Results from HistoGeneX (kappa = 0.95), Genzyme (kappa = 0.94), and Agencourt (kappa = 0.94) were in almost perfect agreement with these results, and the results from Gentris were in substantial agreement with the results from Amgen (kappa = 0.75). The Invitek allele-specific assay demonstrated slight agreement (kappa = 0.13).

CONCLUSIONS

This study provides data on the comparability of KRAS mutational analyses. The results suggest that most (but not all) commercial services provide analysis that is accurate and comparable with direct sequencing.

Biochemical characterization of AMG 102: a neutralizing, fully human monoclonal antibody to human and nonhuman primate hepatocyte growth factor

AMG 102 is a fully human monoclonal antibody that selectively targets and neutralizes hepatocyte growth factor/scatter factor (HGF/SF). A detailed biochemical and functional characterization of AMG 102 was done to support its clinical development for the treatment of cancers dependent on signaling through the HGF/SF:c-Met pathway. In competitive equilibrium binding experiments, AMG 102 bound to human and cynomolgus monkey HGF with affinities of approximately 19 pmol/L and 41 pmol/L, respectively. However, AMG 102 did not detect mouse or rabbit HGF on immunoblots. Immunoprecipitation experiments showed that AMG 102 preferentially bound to the mature, active form of HGF, and incubation of AMG 102/HGF complexes with kallikrein protease indicated that AMG 102 had no apparent effect on proteolytic processing of the inactive HGF precursor. AMG 102 inhibited human and cynomolgus monkey HGF-induced c-Met autophosphorylation in PC3 cells with IC(50) values of 0.12 nmol/L and 0.24 nmol/L, respectively. AMG 102 also inhibited cynomolgus monkey HGF-induced migration of human MDA-MB-435 cells but not rat HGF-induced migration of mouse 4T1 cells. Epitope-mapping studies of recombinant HGF molecules comprising human/mouse chimeras and human-to-mouse amino acid substitutions showed that amino acid residues near the NH(2)-terminus of the beta-chain are critical for AMG 102 binding. Bound AMG 102 protected one trypsin protease cleavage site near the NH(2)-terminus of the beta-chain of human HGF, further substantiating the importance of this region for AMG 102 binding. Currently, AMG 102 is in phase II clinical trials in a variety of solid tumor indications. Mol Cancer Ther; 9(2); 400-9.

Phase II study of safety and efficacy of motesanib in patients with progressive or symptomatic, advanced or metastatic medullary thyroid cancer

PURPOSE

This phase II study investigated the efficacy and tolerability of motesanib, an investigational, highly selective inhibitor of vascular endothelial growth factor receptors 1, 2, and 3; platelet-derived growth factor receptor; and Kit in advanced medullary thyroid cancer (MTC).

PATIENTS AND METHODS

Patients with locally advanced or metastatic, progressive or symptomatic MTC received motesanib 125 mg/d orally for up to 48 weeks or until unacceptable toxicity or disease progression. The primary end point was objective response by independent review. Other end points included duration of response, progression-free survival, safety, pharmacokinetics, and changes in tumor markers.

RESULTS

Of 91 enrolled patients who received motesanib, two (2%) achieved objective response (95% CI, 0.3% to 7.7%); their duration of response was 32 weeks (censored) and 21 weeks (disease progressed). Eighty-one percent of patients had stable disease (48% had durable stable disease > or = 24 weeks), 8% had disease progression as best response, and 9% were not evaluated; 76% experienced a decrease from baseline in target lesion measurement. Median progression-free survival was 48 weeks (95% CI, 43 to 56 weeks). Among patients with tumor marker analysis, 69 (83%) of 83 and 63 (75%) of 84 had decreased serum calcitonin and carcinoembryonic antigen during treatment, respectively, compared with baseline. The most common treatment-related adverse events were diarrhea (41%), fatigue (41%), hypothyroidism (29%), hypertension (27%), and anorexia (27%). In pharmacokinetic analyses, motesanib trough concentrations were lower compared with differentiated thyroid cancer patients from the same study.

CONCLUSION

Although the objective response rate was low, a significant proportion of MTC patients (81%) achieved stable disease while receiving motesanib.

An antibody to IP-10 is a potent antagonist of cell migration in vitro and in vivo and does not affect disease in several animal models of inflammation

IP-10 secretion is induced by pro-inflammatory cytokines and mediates the migration of CXCR3+ cells. Its elevation in clinical samples has been associated with multiple inflammatory diseases and its antagonism has been reported to be effective in several animal models of inflammatory disease. We generated a mouse anti-mouse IP-10 monoclonal antibody (mAb; Clone 20A9) that specifically bound murine IP-10 with high affinity and inhibited in vitro IP-10 induced BaF3/mCXCR3 cell migration with an IC(50) of approximately 4 nM. The 20A9 mAb was completely absorbed in vivo and had dose proportional pharmacokinetic exposure with a serum half life of 2.4-6 days. The 20A9 mAb inhibited IP-10 mediated T-cell recruitment to the airways, indicating that it is effective in vivo. However, administration of the 20A9 mAb had no significant effect on disease in mouse models of delayed type hypersensitivity, collagen induced arthritis, cardiac allograft transplantation tolerance, EAE or CD4+ CD45RBHi T-cell transfer-induced IBD. These data suggest that the 20A9 mAb can antagonize IP-10 mediated chemotaxis in vitro and in vivo and that this is insufficient to cause a therapeutic benefit in multiple mouse models of inflammatory disease.

Targeted deletion of Nm23/nucleoside diphosphate kinase A and B reveals their requirement for definitive erythropoiesis in the mouse embryo

The ubiquitously expressed nucleoside diphosphate kinases (Nm23/NDPK/Awd) are a large family of multifunctional enzymes implicated in nucleic acid metabolism and in normal and abnormal development. Here, we describe the generation and characterization of NDPK A- and B-deficient (Nme1(-/-)/Nme2(-/-)) mice in which >95% of the enzyme activity is eliminated. These mice are undersized, die perinatally, and exhibit a spectrum of hematological phenotypes including severe anemia, impaired maturation of erythrocytes, and abnormal hematopoiesis in the liver and bone marrow. Flow cytometric analysis of developing Nme1(-/-)/Nme2(-/-) erythroid cells indicated that the major iron transport receptor molecule TfR1 is attenuated concomitant with a reduction of intracellular iron, suggesting that TfR1 is a downstream target of NDPKs and that reduced iron in Nme1(-/-)/Nme2(-/-) erythroblasts is inhibiting their development. We conclude that Nm23/NDPKs play critical roles in definitive erythroid development. Our novel mouse model also links erythropoiesis and nucleotide metabolism.

Influence of agricultural practices on the contamination of maize by fumonisin mycotoxins

The objective of the present work was to investigate the effect of different agricultural practices on the contamination of maize by fumonisin mycotoxins. Corn samples were collected from 16 maize fields located in Aragón (northeastern Spain) during the 2007 crop year. Corn samples were collected from each field five times at different maturation stages: F1, day 0 (milky corn); F2, day 15; F3, day 30 (yellow corn); F4, day 45; and F5, ripe corn at harvest. The agricultural practices evaluated were type of seed (conventional and transgenic), planting method (dry and wet planting), tillage system (plowing and minimum tillage), type of irrigation (flood and sprinkler), residue management of preceding crop (removal and burial), nitrogen fertilization level (kg N per ha), and harvest date. Mycotoxin analysis was carried out with the ROSA Fumonisin test, which measures both fumonisin B1 and B2 by lateral flow immunoassay. No fumonisins were detected in milky corn (F1 and F2 stages). Only one field had fumonisins in F3 yellow corn (1,037 microg/kg); this field was part of the only farm affected by borer insects. One-third of fields had fumonisins at the F4 stage (363 microg/kg), and 62.5% of the fields were positive for fumonisins at the F5 harvest stage (520 microg/kg). Wet planting and the removal of debris from the previous crop significantly lowered the risk of fumonisin in corn. The use of insect-resistant maize seeds tended to reduce fumonisin levels. However, higher levels of nitrogen fertilizer had a tendency to increase fumonisin levels in corn. Tillage system, type of irrigation, and harvest date had no clear effect on fumonisin levels.

Pancreatic islet expression profiling in diabetes-prone C57BLKS/J mice reveals transcriptional differences contributed by DBA loci, including Plagl1 and Nnt

Background

C57BLKS/J (BLKS) mice are susceptible to islet exhaustion in insulin-resistant states as compared with C57BL6/J (B6) mice, as observed by the presence of the leptin receptor (Lepr) allele, Lepr^db/db. Furthermore, DBA2/J (DBA) mice are also susceptible to β-cell failure and share 25% of their genome with BLKS; thus the DBA genome may contribute to β-cell dysfunction in BLKS mice.

Results

Here we show that BLKS mice exhibit elevated insulin secretion, as evidenced by improved glucose tolerance and increased islet insulin secretion compared with B6 mice, and describe interstrain transcriptional differences in glucose response. Transcriptional differences between BLKS and B6 mice were identified by expression profiling of isolated islets from both strains. Genomic mapping of gene expression differences demonstrated a significant association of expression differences with DBA loci in BLKS mice (P = 4×10^-27).

Conclusion

Two genes, Nicotinamide nucleotide transhydrogenase (Nnt) and Pleiomorphic adenoma gene like 1 (Plagl1), were 4 and 7.2-fold higher respectively in BLKS islets, and may be major contributors to increased insulin secretion by BLKS islets. Contrary to reports for B6 mice, BLKS mice do not harbor a mutant Nnt gene. We detected 16 synonymous polymorphisms and a two-amino acid deletion in the Plagl1 gene in BLKS mice. Several inflammatory glucose-responsive genes are expressed at a higher level in BLKS, suggesting an inflammatory component to BLKS islet dysfunction. This study describes physiological differences between BLKS and B6 mice, and provides evidence for a causative role of the DBA genome in β-cell dysfunction in BLKS mice.

Identification of three loci affecting HDL-cholesterol levels in a screen for chemically induced recessive mutations in mice

We conducted a genome-wide screen using the mutagen N-ethyl-N-nitrosourea to identify recessive mutations in genes that lead to altered lipid traits in mice. We screened 7,546 G3 mice that were of mixed C57BL/6J (B6) x C3.SW-H2(b)/SnJ (C3) genomes and identified three pedigrees with differences in plasma HDL-cholesterol. Genome scan analyses mapped three distinct loci to chromosomes 3, 4, and 7. An S1748L missense mutation was identified in ABCA1 in one pedigree with undetectable levels of HDL-cholesterol and resulted in reduced protein levels. This phenotype was completely penetrant, semi-dominant, and cosegregated with high plasma triglycerides. Mice in a second pedigree had very high levels of plasma total cholesterol and HDL-cholesterol (up to 800 mg/dl total cholesterol). Despite a high degree of phenotype lability and reduced penetrance, an I68N missense mutation was identified in the transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha). Finally, a second high HDL-cholesterol pedigree of mice, again with a highly labile phenotype and reduced penetrance, was mapped to a 7 Mb locus on chromosome 3. These results illustrate the use of a hybrid background for simultaneous screening and mapping of mutagenized pedigrees of mice and identification of three novel alleles of HDL-cholesterol phenotypes.

Association of K-ras mutational status and clinical outcomes in patients with metastatic colorectal cancer receiving panitumumab alone

BACKGROUND

Identifying predictive biomarkers is important to optimally treat patients. This analysis evaluated the association of K-ras, BRAF, and PIK3CA gene mutations with tumor resistance to panitumumab alone.

PATIENTS AND METHODS

From 3 phase II panitumumab metastatic colorectal cancer (mCRC) studies, 62 of 533 patient samples were available. Mutations were identified from genomic DNA by sequencing.

RESULTS

Of the 62 samples, 24 (38.7%) harbored a K-ras mutation, and 38 (61.3%) were wild type. In the wild-type K-ras group, 11% of patients had a partial response (PR), 53% had stable disease (SD), and 37% had progressive disease (PD). In the mutant K-ras group, 21% of patients had SD, and 79% of patients had PD; there were no responses. The absence of a K-ras mutation was associated with response to panitumumab (PR vs. SD vs. PD; P = .0028). The hazard ratio for wild-type versus mutant K-ras was 0.4 (95% CI, 0.2-0.7) for progression-free survival and 0.5 (95% CI, 0.3-0.9) for overall survival. Four patients had a V600E BRAF mutation, and 2 patients had a PIK3CA mutation.

CONCLUSION

These data suggest that patients with mCRC with activating K-ras mutations are less likely to respond to panitumumab alone. The small sample size limits us from defining a predictive role of PIK3CA and BRAF mutations for panitumumab treatment.

Motesanib diphosphate in progressive differentiated thyroid cancer

BACKGROUND

The expression of vascular endothelial growth factor (VEGF) is characteristic of differentiated thyroid cancer and is associated with aggressive tumor behavior and a poor clinical outcome. Motesanib diphosphate (AMG 706) is a novel oral inhibitor of VEGF receptors, platelet-derived growth-factor receptor, and KIT.

METHODS

In an open-label, single-group, phase 2 study, we treated 93 patients who had progressive, locally advanced or metastatic, radioiodine-resistant differentiated thyroid cancer with 125 mg of motesanib diphosphate, administered orally once daily. The primary end point was an objective response as assessed by an independent radiographic review. Additional end points included the duration of the response, progression-free survival, safety, and changes in serum thyroglobulin concentration.

RESULTS

Of the 93 patients, 57 (61%) had papillary thyroid carcinoma. The objective response rate was 14%. Stable disease was achieved in 67% of the patients, and stable disease was maintained for 24 weeks or longer in 35%; 8% had progressive disease as the best response. The Kaplan-Meier estimate of the median duration of the response was 32 weeks (the lower limit of the 95% confidence interval [CI] was 24; the upper limit could not be estimated because of an insufficient number of events); the estimate of median progression-free survival was 40 weeks (95% CI, 32 to 50). Among the 75 patients in whom thyroglobulin analysis was performed, 81% had decreased serum thyroglobulin concentrations during treatment, as compared with baseline levels. The most common treatment-related adverse events were diarrhea (in 59% of the patients), hypertension (56%), fatigue (46%), and weight loss (40%).

CONCLUSIONS

Motesanib diphosphate can induce partial responses in patients with advanced or metastatic differentiated thyroid cancer that is progressive. (ClinicalTrials.gov number, NCT00121628.)

Wild-type KRAS is required for panitumumab efficacy in patients with metastatic colorectal cancer

PURPOSE

Panitumumab, a fully human antibody against the epidermal growth factor receptor (EGFR), has activity in a subset of patients with metastatic colorectal cancer (mCRC). Although activating mutations in KRAS, a small G-protein downstream of EGFR, correlate with poor response to anti-EGFR antibodies in mCRC, their role as a selection marker has not been established in randomized trials.

PATIENTS AND METHODS

KRAS mutations were detected using polymerase chain reaction on DNA from tumor sections collected in a phase III mCRC trial comparing panitumumab monotherapy to best supportive care (BSC). We tested whether the effect of panitumumab on progression-free survival (PFS) differed by KRAS status.

RESULTS

KRAS status was ascertained in 427 (92%) of 463 patients (208 panitumumab, 219 BSC). KRAS mutations were found in 43% of patients. The treatment effect on PFS in the wild-type (WT) KRAS group (hazard ratio [HR], 0.45; 95% CI: 0.34 to 0.59) was significantly greater (P < .0001) than in the mutant group (HR, 0.99; 95% CI, 0.73 to 1.36). Median PFS in the WT KRAS group was 12.3 weeks for panitumumab and 7.3 weeks for BSC. Response rates to panitumumab were 17% and 0%, for the WT and mutant groups, respectively. WT KRAS patients had longer overall survival (HR, 0.67; 95% CI, 0.55 to 0.82; treatment arms combined). Consistent with longer exposure, more grade III treatment-related toxicities occurred in the WT KRAS group. No significant differences in toxicity were observed between the WT KRAS group and the overall population.

CONCLUSION

Panitumumab monotherapy efficacy in mCRC is confined to patients with WT KRAS tumors. KRAS status should be considered in selecting patients with mCRC as candidates for panitumumab monotherapy.

Heterologous expression of the adenosine A1 receptor in transgenic mouse retina

Traditional cell-based systems used to express integral membrane receptors have yet to produce protein samples of sufficient quality for structural study. Herein we report an in vivo method that harnesses the photoreceptor system of the retina to heterologously express G protein-coupled receptors in a biochemically homogeneous and pharmacologically functional conformation. As an example we show that the adenosine A1 receptor, when placed under the influence of the mouse opsin promoter and rhodopsin rod outer segment targeting sequence, localized to the photoreceptor cells of transgenic retina. The resulting receptor protein was uniformly glycosylated and pharmacologically well behaved. By comparison, we demonstrated in a control experiment that opsin, when expressed in the liver, had a complex pattern of glycosylation. Upon solubilization, the retinal adenosine A1 receptor retained binding characteristics similar to its starting material. This expression method may prove generally useful for generating high-quality G protein-coupled receptors for structural studies.

The vanilloid receptor TRPV1 is tonically activated in vivo and involved in body temperature regulation

The vanilloid receptor TRPV1 (transient receptor potential vanilloid 1) is a cation channel that serves as a polymodal detector of pain-producing stimuli such as capsaicin, protons (pH <5.7), and heat. TRPV1 antagonists block pain behaviors in rodent models of inflammatory, neuropathic, and cancer pain, suggesting their utility as analgesics. Here, we report that TRPV1 antagonists representing various chemotypes cause an increase in body temperature (hyperthermia), identifying a potential issue for their clinical development. Peripheral restriction of antagonists did not eliminate hyperthermia, suggesting that the site of action is predominantly outside of the blood-brain barrier. Antagonists that are ineffective against proton activation also caused hyperthermia, indicating that blocking capsaicin and heat activation of TRPV1 is sufficient to produce hyperthermia. All TRPV1 antagonists evaluated here caused hyperthermia, suggesting that TRPV1 is tonically activated in vivo and that TRPV1 antagonism and hyperthermia are not separable. TRPV1 antagonists caused hyperthermia in multiple species (rats, dogs, and monkeys), demonstrating that TRPV1 function in thermoregulation is conserved from rodents to primates. Together, these results indicate that tonic TRPV1 activation regulates body temperature.

High levels of ochratoxin A in licorice and derived products

The ochratoxin A (OTA) content of 30 samples of licorice root and derived products (licorice-confectionery, licorice block, and licorice extract) was analyzed by a standard HPLC-fluorescence technique and confirmed by methyl-ester formation. All analyzed samples of licorice and derived products were found to contain ochratoxin A, and some of them showed extremely high concentrations up to 252.8 ng/g of OTA. Highest levels of ochratoxin A were found in dry licorice root, averaging 63.6 ng/g, while mean contents in fresh licorice root were 9.2 ng/g. Licorice-confectionery (sweets) contained 3.8 ng/g of OTA. Ochratoxin A was also abundant in two licorice derivatives, liquid licorice extract (16.0 ng/g) and solid licorice block (39.5 ng/g). The ochratoxin levels found in licorice and derived products are higher than those reported in the literature for other food commodities. The experiments of OTA transfer into the tea beverages showed that almost 5% of the OTA present in dry licorice root is transferred to the corresponding decoction tea, whereas only 1% of OTA remains in infusion tea. The significance of the levels of ochratoxin A in licorice and its derivatives is discussed in the context of existing data on ochratoxin contamination in foods.

Generation and characterization of monoclonal antibodies to human keratinocyte growth factor receptor

Keratinocyte growth factor receptor (KGFR) and fibroblast growth factor receptor (FGFR) 2c share identical amino acid sequences, except for a 46-amino acid domain in the extracellular region. Monoclonal antibodies (MAbs) specific to KGFR have not been reported nor are commercially available. In this study, we generated murine MAbs specific to KGFR in non-obese diabetic (NOD) mice using a modified Repeated Immunizations at Multiple Sites (RIMMS) technology. Stable cell lines expressing the full-length human KGFR or FGFR2c were produced to facilitate the identification of KGFR-specific MAbs. Following the initial screening of hybridoma clones with a fluorescence-based, confocal cell detection method and ELISA, KGFR-specific MAbs were selected and confirmed by flow cytometry and Western blot analyses. Antagonistic MAbs were identified using a cell-based functional assay. These KGFR MAbs will be important reagents for studying the biological function and tissue distribution of this receptor in normal and pathological conditions.

Epratuzumab, a humanized monoclonal antibody targeting CD22: characterization of in vitro properties

PURPOSE

Epratuzumab is a novel humanized antihuman CD22 IgG1 antibody that has recently shown promising clinical activity, both as a single agent and in combination with rituximab, in patients with non-Hodgkin's lymphomas (NHL). In an attempt to better understand the mode of action of epratuzumab, the antibody was tested in vitro in a variety of cell-based assays similar to those used to evaluate the biological activity of other therapeutic monoclonal antibodies, including rituximab. In this report, we present epratuzumab activities as they relate to binding, signaling, and internalization of the receptor CD22.

METHODS

Chinese hamster ovary-expressed CD22 extracellular domain was used to measure epratuzumab affinity on Biacore. CD22 receptor density and internalization rate were measured indirectly using a monovalently labeled, noncompeting (with epratuzumab) anti-CD22 antibody on Burkitt lymphoma cell lines, primary B cells derived from fresh tonsils, and B cells separated from peripheral blood samples obtained from patients with chronic lymphocytic leukemia or healthy volunteers. Epratuzumab-induced CD22 phosphorylation was measured by immunoprecipitation/Western blot and compared with that induced by anti-IgM stimulation.

RESULTS

Epratuzumab binds to CD22-extracellular domain, with an affinity of K(D) = 0.7 nM. Binding of epratuzumab to B cell lines, or primary B cells from healthy individuals and patients with NHL, results in rapid internalization of the CD22/antibody complex. Internalization appears to be faster at early time points in cell lines than in primary B cells and NHL patient-derived B cells, but the maximum internalization reached is comparable for all B cell populations after several hours of treatment and appears to reach saturation at antibody concentrations of 1-5 micro g/ml. Finally, epratuzumab binding results in modest but significant CD22 phosphorylation.

CONCLUSIONS

Epratuzumab represents an excellent anti-CD22 ligating agent, highly efficacious in inducing CD22 internalization, and can induce phosphorylation. Although we cannot unequivocally demonstrate here that epratuzumab-induced internalization and signaling of CD22 directly contribute to its therapeutic efficacy, these properties are the fundamental characteristics of the target CD22 and its interaction with epratuzumab. Similar results were observed when epratuzumab was tested in vitro on Burkitt B cell lines as well as on primary normal B cells and neoplastic B cells separated from fresh peripheral blood samples from patients with chronic lymphocytic leukemia.

The dual specificity JKAP specifically activates the c-Jun N-terminal kinase pathway

The involvement of dual specificity phosphatases (DSPs) in the mitogen-activated protein kinase (MAPK) signaling has been mostly limited to the inactivation of MAPKs by the direct dephosphorylation of the TXY motif within their activation loop. We report the cloning and characterization of a murine DSP, called JNK pathway-associated phosphatase (JKAP), which lacks the regulatory region present in most other MAP kinase phosphatases (MKPs) and is preferentially expressed in murine Lin(-)Sca-1(+) stem cells. Overexpression of JKAP in human embryonic kidney 293T cells specifically activated c-Jun N-terminal kinase (JNK) but not p38 and extracellular signal-regulated kinase 2. Overexpression of a mutant JKAP, JKAP-C88S, blocked tumor necrosis factor-alpha-induced JNK activation. Targeted gene disruption in murine embryonic stem cells abolished JNK activation by tumor necrosis factor-alpha and transforming growth factor-beta, but not by ultraviolet-C irradiation, indicating that JKAP is necessary for optimal JNK activation. JKAP associated with JNK and MKK7, but not SEK1, in vivo. However, JKAP did not interact with JNK in vitro, suggesting that JKAP exerts its effect on JNK in an indirect manner. Taken together, these studies identify a positive regulator for the JNK pathway and suggest a novel role for DSP in mitogen-activated protein kinase regulation.

A novel Notch ligand, Dll4, induces T-cell leukemia/lymphoma when overexpressed in mice by retroviral-mediated gene transfer

Notch receptors mediate cell-fate decisions through interaction with specific ligands during development. The biological role of a novel Notch ligand, Dll4, in mice was explored by reconstituting lethally irradiated mice with bone marrow (BM) cells transduced with Dll4 retroviral vector. White blood cell and lymphocyte counts in Dll4-overexpressing mice were reduced at the early stage of reconstitution but increased significantly at approximately 10 weeks after BM transplantation. BM, spleen, lymph nodes, and peripheral blood of Dll4-overexpressing mice contained predominantly CD4(+)CD8(+) T cells and virtually lacked B cells. The Dll4-overexpressing mice eventually developed a lethal phenotype that was characterized by the progression of a T-cell lymphoproliferative disease (restricted to BM and lymphoid tissues) to transplantable monoclonal T-cell leukemia/lymphoma scattered to multiple organs. Results suggest that the interaction of Dll4 with Notch1 may provide key signals for T-cell development.