Stable isotope dimethyl labeling combined with LTQ mass spectrometric detection, a quantitative proteomics technology used in liver cancer research

Abstract

Liver cancer is a common malignant disease, with high incidence and mortality rates. The study on the proteomics of liver cancer has attracted particular attention. The quantitative study method of proteomics depends predominantly on two-dimensional (2D) gel electrophoresis. In the present study we reported a rapid and accurate proteomics quantitative study method of high repeatability that includes the use of stable isotope labeling for the extraction of proteins and peptides via enzymolysis to achieve new type 2D capillary liquid chromatography-mass spectrometry separation using the separation mode of cation-exchange chromatography in conjunction with reversed-phase chromatography. LTQ OrbiTrap mass spectrometry detection was also performed. A total of 188 differential proteins were analyzed, including 122 upregulating [deuterium/hydrogen ratio (D/H) >1.5)] and 66 downregulating proteins (D/H<0.67). These proteins may play an important role in the occurrence, drug resistance, metastasis and recurrence of cancer or other pathological processes. Such a proteomics technology may provide biological data as well as a new methodological basis for liver cancer research.

Keywords: liver cancer; mass spectrum; quantitative proteomics; stable isotope labeling.

Figure 1.

Labeling reaction of stable isotope dimethyl labeling

Figure 2.

Identification of the peptide sequence of protein 14-3-3 ζ/δ.

Figure 3.

Quantitative analysis of protein 14-3-3 ζ/δ.

Figure 4.

Western blot analysis of 14-3-3 protein ζ and δ expression levels. T, liver cancer cell; C, normal liver cell.

Figure 5.

Western blot analysis of TCP1η and TCP1θ protein expression levels. T, liver cancer cell; C, normal liver cell.