Differential proteins in esophageal squamous cell line EC9706/CDDP identified by SILAC quantitative proteomic approach

Multidrug resistance (MDR) is one of the main causes leading to the failure in cancer treatment.  Differential proteins between esophageal squamous cell carcinoma (ESCC) cell line EC9706 and its cis-diamminedichloroplatinum (CDDP)-resistant subline EC9706/CDDP revealed by quantitative analysis may provide deeper insights into the molecular mechanisms of MDR implicated in ESCC.  EC9706/CDDP was generated by exposure of its parental sensitive EC9706 to a step-wise increase of CDDP concentration during EC9706 cultivation.  The stable isotope labeling with amino acids in cell culture (SILAC) was used to label EC9706 and EC9706/CDDP with heavy and light medium, separately.  Mixed peptides derived from EC9706 and EC9706/CDDP were analyzed by high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS/MS) and subsequently subjected to bioinformatics analysis to identify differential proteins between EC9706 and EC9706/CDDP.  Compared to parental EC9706, EC9706/CDDP manifested phenotypes of slow proliferation, cell pleomorphology, atypia and increased resistant-index 3.23.  Seventy-four differential proteins identified in the present study belongs to various families with multiple functions, such as cytoskeleton (20%), energy metabolism (11%), transcription regulation and DNA repair (11%), redox homeostasis (9.5%), protein biosynthesis and mRNA processing (12%), ribosome constituent (8.1%), molecular chaperone (8.1%), immunity/inflammation (5.4%), intracellular transport (5.4%) and nucleosome assembly (2.7%), which indicated that development of MDR is a complicated process involving dysregulation of multiple molecules and pathways.  The data is of great value for in-depth elucidation of molecular mechanisms of the MDR implicated in ESCC and may represent potential molecular targets for future therapeutic development.