Chemopreventive agents modulate the protein expression profile of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone plus benzo[a]pyrene-induced lung tumors in A/J mice

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Identification of proteins differentially expressed in lung tumors versus normal lung tissues in animal models could accelerate the discovery of biomarkers for cancer risk, early detection, prognosis, and chemopreventive/therapeutic response. We used a quantitative proteomics approach, isobaric tags for relative and absolute quantitation (iTRAQ) technology coupled with mass spectrometry, to investigate qualitative and quantitative differences between 4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) plus benzo[a]pyrene (BaP)-induced lung tumors and that of normal lung tissues from A/J mice. The levels of 75 carcinogenesis-related proteins changed - 37 increased and 38 decreased - in tumor tissues compared to normal tissues. Among proteins that showed an increased level are glycolytic enzymes, ribosomal proteins, fatty acid synthase (FAS), L-plastin, cathepsins D and H, cytochrome C, carbonic anhydrase 2, band 3 anion transport protein and prolyl 4-hydroxylase. Proteins with reduced levels in lung tumors versus normal lung tissues included cytochrome P450 enzymes, glutathione S-transferases (GSTs), procollagens, Clara cell 10-kDA protein, histones, receptor advanced glycation end-product (RAGE), and caveolin-1. Dietary administration of a combination of N-acetyl-S-(N-2-phenethylthiocarbamoyl)-L-cysteine (PEITC-NAC) plus myo-inositol (MI) or indole-3-carbinol (I3C) to carcinogen-treated mice modulated the levels of 30 proteins, including six proteins with unaltered levels in tumor tissues versus normal tissues. Of these 30 proteins, the relative abundance of cytochrome C, carbonic anhydrase 2, and band 3 anion transport protein decreased whereas that of histones, GSTs, RAGE, and procollagens I and VI increased. Western analyses of selected proteins confirmed iTRAQ proteomics results and revealed an increased level of hypoxia inducible factor 1α in lung tumor tissues, and cathepsin D and PSPB in serum of tumor-bearing mice. This is the first study on proteins differentially expressed in tumor tissues obtained from a mouse model of lung carcinogenesis and chemoprevention. These proteins may have utility for the development of candidate lung cancer biomarkers and as targets of chemopreventive/chemotherapeutic agents.