Low molecular weight proteomic information distinguishes metastatic from benign pheochromocytoma.

Metastatic lesions occur in up to 36% of patients with pheochromocytoma. Currently there is no way to reliably detect or predict which patients are at risk for metastatic pheochromocytoma. Thus, the discovery of biomarkers that could distinguish patients with benign disease from those with metastatic disease would be of great clinical value. Using surface-enhanced laser desorption ionization protein chips combined with high-resolution mass spectrometry, we tested the hypothesis that pheochromocytoma pathologic states can be reflected as biomarker information within the low molecular weight (LMW) region of the serum proteome. LMW protein profiles were generated from the serum of 67 pheochromocytoma patients from four institutions and analyzed by two different bioinformatics approaches employing pattern recognition algorithms to determine if the LMW component of the circulatory proteome contains potentially useful discriminatory information. Both approaches were able to identify combinations of LMW molecules which could distinguish all metastatic from all benign pheochromocytomas in a separate blinded validation set. In conclusion, for this study set low molecular mass biomarker information correlated with pheochromocytoma pathologic state using blinded validation. If confirmed in larger validation studies, efforts to identify the underlying diagnostic molecules by sequencing would be warranted. In the future, measurement of these biomarkers could be potentially used to improve the ability to identify patients with metastatic disease.

High-resolution serum proteomic features for ovarian cancer detection.

Serum proteomic pattern diagnostics is an emerging paradigm employing low-resolution mass spectrometry (MS) to generate a set of biomarker classifiers. In the present study, we utilized a well-controlled ovarian cancer serum study set to compare the sensitivity and specificity of serum proteomic diagnostic patterns acquired using a high-resolution versus a low-resolution MS platform. In blinded testing sets, the high-resolution mass spectral data contained multiple diagnostic signatures that were superior to the low-resolution spectra in terms of sensitivity and specificity (P<0.00001) throughout the range of modeling conditions. Four mass spectral feature set patterns acquired from data obtained exclusively with the high-resolution mass spectrometer were 100% specific and sensitive in their diagnosis of serum samples as being acquired from either unaffected patients or those suffering from ovarian cancer. Important to the future of proteomic pattern diagnostics is the ability to recognize inferior spectra statistically, so that those resulting from a specific process error are recognized prior to their potentially incorrect (and damaging) diagnosis. To meet this need, we have developed a series of quality-assurance and in-process control procedures to (a) globally evaluate sources of sample variability, (b) identify outlying mass spectra, and (c) develop quality-control release specifications. From these quality-assurance and control (QA/QC) specifications, we identified 32 mass spectra out of the total 248 that showed statistically significant differences from the norm. Hence, 216 of the initial 248 high-resolution mass spectra were determined to be of high quality and were remodeled by pattern-recognition analysis. Again, we obtained four mass spectral feature set patterns that also exhibited 100% sensitivity and specificity in blinded validation tests (68/68 cancer: including 18/18 stage I, and 43/43 healthy). We conclude that (a) the use of high-resolution MS yields superior classification patterns as compared with those obtained with lower resolution instrumentation; (b) although the process error that we discovered did not have a deleterious impact on the present results obtained from proteomic pattern analysis, the major source of spectral variability emanated from mass spectral acquisition, and not bias at the clinical collection site; (c) this variability can be reduced and monitored through the use of QA/QC statistical procedures; (d) multiple and distinct proteomic patterns, comprising low molecular weight biomarkers, detected by high-resolution MS achieve accuracies surpassing individual biomarkers, warranting validation in a large clinical study.

Mutagenicity of halogenated ether anesthetics.

An in vitro microbial assay system employing two histidine-dependent strains of Salmonella typhimurium, TA1535 and TA100, was used to test the mutagenicities of enflurane, methoxyflurane, isoflurane and fluroxene. Enflurane, isoflurane and fluroxene in concentrations ranging from 0.01 to 30 per cent and methoxyflurane in concentrations ranging from 0.01 to 7 per cent were incubated with bacteria in the presence or absence of homogenates of liver prepared from rats pretreated with the enzyme inducer, Aroclor 1254. Enflurane, methoxyflurane, isoflurane, and urines from patients anesthetized with these agents were not mutagenic. Fluroxene, however, was highly mutagenic, and therefore poses a possible hazard for operating room personnel and patients.

Thermoregulatory defect in rats during anesthesia.

Male rats of the Fischer 344, Sprague-Dawley, Brattleboro, and Wistar strains, balb/C mice, and Hartley guinea pigs were divided into 2 treatment groups. One group drank tap water while the other group drank water containing 1 mg/ml of phenobarbital. Animals were exposed to sevoflurane, enflurane, methoxyflurane, isoflurane, or halothane in a closed chamber. In some of the experiments, soda lime was included and in other the chamber was heated to 39 degrees C with a water blanket. Eighty-six percent (43/50) of Fischer 344 rats treated with phenobarbital and esposed to either sevoflurane or enflurane, in the presence of either soda lime or exogenous heat, died within a few hours after exposure. Fischer 344 rats and rats of other strains drinking phenobarbital water and exposed to methoxyflurane were affected, but to a lesser degree. Rats drinking ordinary tap water and phenobarbital-treated rats not exposed to either soda lime or exogenous heat were unaffected. Guinea pigs and mice also were unaffected. We postulate that the toxic response represents a species-specific thermoregulatory defect, precipitated by heat and occurring in rats treated with phenobarbital in combination with sevoflurane, endlurane, or methoxyflurane.