Comprehensive Proteomic Analysis of the Effects of Purine Analogs on Human Raji B-Cell Lymphoma

Cladribine (CdA) and fludarabine (FdAMP) are purine analogs that induce apoptosis in chronic lymphocytic leukemia and non-Hodgkin’s lymphoma, but the mechanisms are undefined. The effects of CdA and fludarabine nucleoside (FdA) on the cytosolic, mitochondrial, and nuclear proteomes in human Raji lymphoma cells have been determined using two-dimensional fluorescence difference gel electrophoresis (DIGE) and mass spectrometry. Differentially abundant proteins have provided new insights into CdA- and FdA-induced apoptosis. Treatment with these purine analogs induced changes in proteins involved with intermediary metabolism, cell growth, signal transduction, protein metabolism, and regulation of nucleic acids. Differentially abundant mitochondrial 39S ribosomal protein L50, mTERF domain-containing protein 1, Chitinase-3 like 2 protein, and ubiquinone biosynthesis protein COQ9 have been identified in cells undergoing apoptosis. Up-regulation of several stress-associated proteins found in the endoplasmic reticulum (ER) including GRP78, ERp57, and ORP150 suggests that purine analog-induced apoptosis may result from ER stress and unfolded protein response. While mitochondria-dependent apoptosis has been associated with purine analog cytotoxicity, the likely involvement of the ER stress pathway in CdA- and FdA-induced apoptosis has been shown here for the first time.