Plasma proteomics of lung cancer by a linkage of multi-dimensional liquid chromatography and two-dimensional difference gel electrophoresis.

To investigate aberrant plasma proteins in lung cancer, we compared the proteomic profiles of serum from five lung cancer patients and from four healthy volunteers. Immuno-affinity chromatography was used to deplete highly abundant plasma proteins, and the resulting plasma samples were separated into eight fractions by anion-exchange chromatography. Quantitative protein profiles of the fractionated samples were generated by two-dimensional difference gel electrophoresis, in which the experimental samples and the internal control samples were labeled with different dyes and co-separated by two-dimensional polyacrylamide gel electrophoresis. This approach succeeded in resolving 3890 protein spots. For 364 of the protein spots, the expression level in lung cancer was more than twofold different from that in the healthy volunteers. These differences were statistically significant (Student's t-test, p-value less than 0.05). Mass spectrometric protein identification revealed that the 364 protein spots corresponded to 58 gene products, including the classical plasma proteins and the tissue-leakage proteins catalase, clusterin, ficolin, gelsolin, lumican, tetranectin, triosephosphate isomerase and vitronectin. The combination of multi-dimensional liquid chromatography and two-dimensional difference gel electrophoresis provides a valuable tool for serum proteomics in lung cancer.