Proteomic identification of differentially-expressed proteins in esophageal cancer in three ethnic groups in Xinjiang.

The Objective is to identify candidate biomarkers for Squamous cell carcinoma (ESCC) in three ethnics in Xinjiang as well as reveal molecular mechanism. Proteins from 15 pairs of ESCC and matching adjacent normal esophageal tissues (five pairs in each ethnic of Kazakh, Uygur and Han) were separated by 2-DE and differentially proteins were identified by matrix-assisted laser desorption/ionization time-of-flight MS. After identified by Mascot database, some of interesting proteins were confirmed in the other 175 pairs of ESCC by immuno histochemistry. Comparison of patterns revealed 20 proteins significantly changed, of which 12 protein with concordantly increased, such as ACTB protein, COMT protein, Syntaxin binding protein Pyruvate Kinase (PKM2), Cathepsin D, Chromosome 1 open reading frame 8, Heat shock protein 27, Cdc42, Proteosome, LLDBP, Immunoglobulin, TNF receptor associated factor 7; and eight protein spots with concordantly decreased intensity in ESCC, such as Adenylate kinase 1, General transcription factor II H, Smooth muscle protein, Trangelin, Early endosome antigen 1, Annexin A2, Fibrin beta, Tropomyosin. There were a significant difference in protein overexpression of PKM2 (74.9%) and Cathepsin D (85.1%) in ESCC compared to adjacent tissues (P < 0.05) by immunohistochemistry. Further, overexpression of Cathepsin D was obvious difference in Hazakh ESCC (94.7%) than that in Uygur (78.6%) (P < 0.05). Interestingly, the overexpression of Cathepsin D was reversely associated with ESCC differentiation (P < 0.05). Twenty proteins differentially-expressed between ESCC and normal tissues were identified. Cathepsin D and PKM2 were for the first time observed to be dysregulated in Kazakh's ESCC. Moreover, Cathepsin D may play a complicated role both in carcinogenesis and cell-differentiation of ESCC.