Proteomic analysis of the murine liver in response to a combined exposure to psychological stress and 7,12-dimethylbenz(a)anthracene.

Polycyclic aromatic hydrocarbons (PAHs) are environmental carcinogens implicated to underlie development of several types of cancers. Cytochrome P450 (CYP) enzymes play key roles in the conversion of PAHs to highly potent carcinogens, namely diol epoxides. 7,12-Dimethylbenz(a)anthracene (DMBA), a PAH, is highly carcinogenic, where in mouse models it is known to be responsible for initiating tumor formation in many organs including mammary tissues, ovaries, and skin. Psychological stress, via release of biochemical mediators, can greatly impact carcinogenesis. The present investigation examined the hypothesis that psychological stress modulates metabolism and carcinogenicity of DMBA through alteration of key drug metabolizing enzyme abundance levels in the liver utilizing mass spectrometry-based proteomics. To test this hypothesis, four groups of mice were treated as follows: nonstressed, stressed, nonstressed/DMBA-exposed, and stressed/DMBA-exposed, where the stressor was a well-accepted model of restraint. Liver proteins were extracted, resolved by one-dimensional gel electrophoresis, digested in-gel with trypsin, and analyzed by liquid chromatography-tandem mass spectrometry. This investigation resulted in the unique identification of 59 isoforms of CYP enzymes. Changes in protein abundances derived from spectral counting indicates that stress alone results in increases in the abundance of proteins responsive to oxidative stress, along with Phase I and II metabolizing enzymes, such as CYP2J5 and UDP glucoronytransferases. The proteomic results further indicate that exposure to DMBA induces increases in the abundance of CYP1A2 and serine protease inhibitors and decreases the abundance of CYP4 V3. Finally, significant changes in the abundance of proteins such as CYP1A2, CYP3A11, and Topoisomerase-2 were found between nonstressed and stressed/DMBA-treated mice. These data support the hypothesis that psychological stress modulates DMBA-induced regulation of drug metabolizing proteins in the liver.

Measuring biological age in mice using differential mass spectrometry.

Aging is an ill-defined process that increases the risk of morbidity and mortality. Aging is also heterogeneous meaning that biological and chronological age can differ. Here, we used unbiased differential mass spectrometry to quantify thousands of proteins in mouse liver and select those that that consistently change in expression as mice age. A panel of 14 proteins from inbred C57BL/6 mice was used to equate chronological and biological age in this reference population, against which other mice could be compared. This "biological age calculator" identified two strains of f1 hybrid mice as biologically younger than inbred mice and progeroid mice as being biologically older. In an independent validation experiment, the calculator identified mice treated with rapamycin, known to extend lifespan of mice, as 18% younger than mice fed a placebo diet. This demonstrates that it is possible to measure subtle changes in biologic age in mammals using a proteomics approach.

Distinct profiles of oxidative stress-related and matrix proteins in adult bone and soft tissue osteosarcoma and desmoid tumors: a proteomics study.

Osteosarcomas rarely occur in older adults. Proteomics has not been reported to date in osteosarcoma occurring in the older adult population. This proteomic investigation was conducted to identify differentially expressed proteins in osteosarcoma occurring in various backgrounds from older adults. Desmoid tumors, known to recur locally but not metastasize, were also analyzed. Protein digests isolated from formalin-fixed, paraffin-embedded tumor tissue specimen representing 14 primary osteosarcomas of soft tissue and bone and 18 desmoid tumors were analyzed by high-resolution liquid chromatography-tandem mass spectrometry for protein identification and relative quantification by spectral counting. Elevated abundance levels of several proteins including heat shock protein 90 (HSP90), elastin microfibril interface-located protein 1, and clusterin were identified in osteosarcoma with slight differences in proteomic profiles. Desmoids had an abundance of collagen II and periostin only. The findings were confirmed by immunohistochemical staining for HSP90 and clusterin in the experimental samples and additionally in 16 posttherapy conventional osteosarcomas in tissue microarrays constructed from heterogeneous sarcomas and benign lesions. All osteosarcomas were positive for HSP90 and clusterin to a variable extent. One case of well-differentiated parosteal osteosarcoma was negative. Thirty of 75 other high-grade sarcomas including cases of chondrosarcoma were positive for HSP90. Low-grade and benign lesions and scars and 18 desmoid tumors had little or no expression of these proteins. HSP90 and clusterin represent candidate markers of aggressiveness in osteosarcoma occurring in older adults and may be indicative of drug resistance.