Age-dependent reference intervals in children for the disialoganglioside, GD2, a circulating tumor biomarker for the childhood cancer, neuroblastoma.

BACKGROUND: The disialoganglioside GD2 is a circulating tumor biomarker for the childhood cancer, neuroblastoma. This study establishes reference intervals for GD2 concentration in children within the age range where neuroblastoma commonly occurs. METHODS: Leftover plasma samples taken for routine clinical laboratory tests from children without cancer were collected and assayed for the 18-carbon fatty acid chain length lipoform of GD2 using a validated high-pressure liquid chromatography tandem mass spectrometry method with a lower limit of quantification of 3 nM. Samples were stratified into 5 age cohorts (0-6 months, 6-12 months, 12-36 months, 3-10 years and > 10 years). Non-parametric statistical methods were used to define the upper bound of the reference interval for each age cohort. RESULTS: GD2 was measurable in 90% of samples from children < 10 years of age and GD2 concentration was age-dependent, peaking at 9 months followed by a gradual decline. GD2 was below the lower limit of quantification in 55% of samples in the > 10 years cohort. Upper bounds of reference intervals were 15.5 nM in 0-6 month cohort, 35.1 nM in 6-12 month cohort, 24.9 nM in 12-36 month cohort, 18.4 in 3-10 year cohort and 10.4 nM in > 10 year cohort. CONCLUSIONS: Age-dependent reference intervals were defined for circulating GD2 in children. GD2 concentration was highest in the 6-12 month age cohort, which is below the age of most children with high-risk neuroblastoma. The peak GD2 concentration at 9 months may reflect neurodevelopmental events in the brain.

Overcoming resistance to single-agent therapy for oncogenic BRAF gene fusions via combinatorial targeting of MAPK and PI3K/mTOR signaling pathways.

Pediatric low-grade gliomas (PLGGs) are frequently associated with activating BRAF gene fusions, such as KIAA1549-BRAF, that aberrantly drive the mitogen activated protein kinase (MAPK) pathway. Although RAF inhibitors (RAFi) have been proven effective in BRAF-V600E mutant tumors, we have previously shown how the KIAA1549-BRAF fusion can be paradoxically activated by RAFi. While newer classes of RAFi, such as PLX8394, have now been shown to inhibit MAPK activation by KIAA1549-BRAF, we sought to identify alternative MAPK pathway targeting strategies using clinically relevant MEK inhibitors (MEKi), along with potential escape mechanisms of acquired resistance to single-agent MAPK pathway therapies. We demonstrate effectiveness of multiple MEKi against diverse BRAF-fusions with novel N-terminal partners, with trametinib being the most potent. However, resistance to MEKi or PLX8394 develops via increased RTK expression causing activation of PI3K/mTOR pathway in BRAF-fusion expressing resistant clones. To circumvent acquired resistance, we show potency of combinatorial targeting with trametinib and everolimus, an mTOR inhibitor (mTORi) against multiple BRAF-fusions. While single-agent mTORi and MEKi PLGG clinical trials are underway, our study provides preclinical rationales for using MEKi and mTORi combinatorial therapy to stave off or prevent emergent drug-resistance in BRAF-fusion driven PLGGs.

Second trimester amniotic fluid bisphenol A concentration is associated with decreased birth weight in term infants.

Bisphenol A (BPA) is an endocrine disrupting chemical with ubiquitous environmental exposure. Animal studies have demonstrated that in utero BPA exposure leads to increased adult body weight. Our aim was to characterize human fetal BPA exposure by measuring BPA concentration in second trimester amniotic fluid (AF) samples and to study its relationship with birth weight (BW) in full term infants. To achieve these goals, we developed a total BPA assay utilizing derivatization with pentafluorobenzyl followed by analysis with LC-ECAPCI-MS/MS with a limit of detection of 0.08ng/mL and limit of quantification (LOQ) of 0.25ng/mL. The mean BW of infants with AF BPA 0.40-2.0ng/mL was 241.8g less than infants with AF BPA less than the LOQ after controlling for covariates (p=0.049). No effect was seen outside this range indicating a non-monotonic effect. Our data suggest that low level BPA exposure in utero decreases BW and needs further study.

Serum apolipoprotein A-1 quantification by LC-MS with a SILAC internal standard reveals reduced levels in smokers.

BACKGROUND: Absolute quantification of protein biomarkers such as serum apolipoprotein A1 by both immunoassays and LC-MS can provide misleading results. RESULTS: Recombinant ApoA-1 internal standard was prepared using stable isotope labeling by amino acids in cell culture with [(13)C6(15)N2]-lysine and [(13)C9(15)N1]-tyrosine in human cells. A stable isotope dilution LC-MS method for serum ApoA-1 was validated and levels analyzed for 50 nonsmokers and 50 smokers. CONCLUSION: The concentration of ApoA-1 in nonsmokers was 169.4 mg/dl with an 18.4% reduction to 138.2 mg/dl in smokers. The validated assay will have clinical utility for assessing effects of smoking cessation and therapeutic or dietary interventions in high-risk populations.

Stable isotope dilution multidimensional liquid chromatography-tandem mass spectrometry for pancreatic cancer serum biomarker discovery.

A novel approach to pancreatic cancer biomarker discovery has been developed, which employs a stable isotope labeled proteome (SILAP) standard coupled with extensive multidimensional separation coupled with tandem mass spectrometry (MS/MS). Secreted proteins from CAPAN-2 human pancreatic cancer derived cells were collected after conducting stable isotope labeling by amino acids in cell culture (SILAC). The resulting SILAP standard contained <0.5% of individual unlabeled proteins. Pooled sera from patients with early stage pancreatic cancer or controls were prepared, and an equal amount of the SILAP standard was added to each sample. Proteins were separated by isoelectric focusing (IEF) prior to two-dimensional liquid chromatography (2D-LC)-MS/MS analysis. A total of 1065 proteins were identified of which 121 proteins were present at 1.5-fold or greater concentrations in the sera of patients with pancreatic cancer. ELISA validation of these findings was successfully performed for two proteins, ICAM-1 and BCAM. Results of these studies have provided proof of principle that a SILAP standard derived from the CAPAN-2 secreted proteome can be used in combination with extensive multidimensional LC-MS/MS for the identification and relative quantitation of potential biomarkers of pancreatic cancer. This technique allows for the detection of low-abundance proteins, and focuses only on biologically relevant proteins derived from pancreatic cancer cells.

Proteomics-based strategy to identify biomarkers and pharmacological targets in leukemias with t(4;11) translocations.

Translocations and other aberrations involving the MLL (mixed lineage leukemia) gene result in aggressive forms of leukemias. Heterogeneity in partner genes, in chromosomal breakpoints, in MLL itself, and in the different partner genes results in heterogeneous fusion transcripts that can be alternatively spliced, which complicates deciphering a unifying mechanism of leukemogenesis. However, recent microarray studies completed with clinical leukemia specimens have uncovered several distinct mRNA signatures within MLL leukemia that differ from other types of leukemia. A global proteomics strategy using MV4-11 and RS4:11 cells in culture was employed to investigate possible protein signatures common to different MLL leukemias and to identify disease biomarkers and protein targets for pharmacological intervention. Initial proteomics screening experiments with two-dimensional differential in-gel electrophoresis revealed heat shock protein 90 alpha (HSP90alpha) as a potential target for pharmacological inhibition and nucleoside diphosphate kinase (nm23) as a biomarker for measuring treatment efficacy. Using a modified stable isotope labeling of amino acids in cell culture (SILAC) approach, coupled with two-dimensional liquid chromatography tandem mass spectrometry (2D-LC-MS/MS), changes in abundance for over 500 proteins were measured. In addition, decreased expression of the novel biomarker nm23 was observed during HSP90 inhibition with 17-allylamino-17-demethoxygeldanamycin (17-AAG) in the MV4-11 cell line. The present study validates the use of a global proteomics strategy to uncover novel biomarkers and pharmacological targets for leukemias with MLL translocations. Additionally, several proteins were found to be expressed in concordance with microarray studies of mRNA expression in specimens from patients showing the value in comparing mRNA transcript and proteomic profiles. This work represents one of the most comprehensive proteomics screens of MLL leukemias that have been conducted to date.

Generation of specific antibodies and their use to characterize sex differences in four rat P450 3A enzymes following vehicle and pregnenolone 16alpha-carbonitrile treatment.

The purpose of this study was to identify isozyme-specific antibodies and use them to determine the expression levels of four P450 3A enzymes in the livers of vehicle- and pregnenolone 16alpha-carbonitrile (PCN)-treated rats of both sexes, since previous work on mRNA levels has shown considerable sexual dimorphism. Using Western blot analysis with four isozyme-specific antibodies, we show that P450 3A1, 3A2, and 3A9 were expressed in vehicle-treated adult female rats at very low levels whereas P450 3A18 was not detected. PCN treatment of females strongly induced the expression of P450 3A1 in the livers with protein product increases of 214-, 3-, and 5-fold for P450 3A1, 3A2, and 3A9, respectively, and P450 3A18 was induced to 3.7 pmol/mg protein. In contrast, all four P450 3As were detected in livers of vehicle-treated males, in the order of 3A2 >> 3A18 > 3A9 approximately = 3A1. The protein product increases induced by PCN treatment of male rats were 92-, 3-, 6-, and 16-fold for P450 3A1, 3A2, 3A9, and 3A18, respectively.

Identification of epitopes on cytochrome P450 3A4/5 recognized by monoclonal antibodies.

In this study we describe the mapping of epitopes on CYP3A4/5 recognized by a panel of monoclonal antibodies (MAbs). CYP3A4 and CYP3A5 cDNAs were cloned in GST expression vectors and the fusion proteins were subjected to Western blot. Eight MAbs reacted with the full-length GST-3A4 fusion protein as well as baculovirus cDNA-expressed CYP3A4, while six of these reacted with baculovirus cDNA-expressed CYP3A5. Five (MAb 347, 351, 352, 354, and 357) out of 8 MAbs were inhibitory in a metabolic assay using quinine as substrate. MAbs 352, 354, and 357 brought about a moderate inhibition of quinine metabolism (60-70%) while MAb 347 inhibited quinine 3- hydroxylation in human liver microsomes (n=6) by more than 70%. MAb 347 was a potent inhibitor of baculovirus-expressed CYP3A5-catalyzed metabolism of quinine (95%) at

Stimulatory effect of cigarette smoking on the 15 alpha-hydroxylation of estradiol by human term placenta.

OBJECTIVE: Our objective was to characterize the oxidative metabolism of estradiol by human term placenta and its modulation by cigarette smoking. METHODS: Placental microsomes were prepared from term placentas obtained from 13 cigarette smokers (20 to 30 cigarettes per day until the time of delivery) and 13 control subjects who were nonsmokers. Estrogen metabolism was studied by incubation of 250 nmol/L [(3)H]estradiol with placental microsomes and NADPH, and the estrogen metabolites were determined by HPLC and gas chromatography-mass spectrometry. RESULTS: 2-Hydroxyestradiol was the major hydroxyestrogen detected, followed by 6alpha-hydroxyestradiol. Small amounts of several other hydroxyestrogen metabolites (4-hydroxyestradiol, 6beta-hydroxyestradiol, 7alpha-hydroxyestradiol, and 16alpha-hydroxyestradiol) were also detected. Large amounts of estrone plus small amounts of 2-hydroxyestrone and unidentified nonpolar metabolites were formed. Cigarette smoking stimulated the placental hydroxylation of benzo[a ]pyrene by about 16-fold. Cigarette smoking had little or no effect on the overall rate of placental estradiol metabolism or on the formation of estrone, 2-hydroxyestradiol, 2-hydroxyestrone, or 16alpha-hydroxyestradiol. However, placental formation of 4-hydroxyestradiol and 7alpha-hydroxyestradiol was increased 38% (P =.08) and 150% (P =.05), respectively, in cigarette smokers. The formation of 6alpha-hydroxyestradiol was decreased 33% (P =.04). Metabolic formation of 15alpha-hydroxyestradiol was observed during incubations of estradiol with placental microsomes from 11 of the 13 cigarette smokers, but this metabolite was not detected during incubations with placental microsomes from any of the 13 nonsmokers. Analysis of data from all 26 placentas showed that the 15alpha-hydroxylation of estradiol was highly correlated with benzo[a ]pyrene hydroxylation (r = 0.93; P <.001). CONCLUSIONS: Many hydroxylated estradiol metabolites were formed by placental microsomes from cigarette smokers and nonsmokers. 15alpha-Hydroxylation of estradiol was markedly stimulated in the placentas of cigarette smokers.