A proteomic analysis of Bcl-2 regulation of cell cycle arrest: insight into the mechanisms.

B cell lymphoma 2 (Bcl-2) is an important antiapoptotic gene that plays a dual role in the maintenance of the dynamic balance between the survival and death of cancer cells. In our previous study, Bcl-2 was shown to delay the G0/G1 to S phase entry by regulating the mitochondrial metabolic pathways to produce lower levels of adenosine triphosphate (ATP) and reactive oxygen species (ROS). However, the detailed molecular mechanisms or pathways by which Bcl-2 regulates the cell cycle remain unknown. Here, we compared the effects of Bcl-2 overexpression with an empty vector control in the NIH3T3 cell line synchronized by serum starvation, and evaluated the effects using proteomic analysis. The effect of Bcl-2 on cell cycle regulation was detected by monitoring Bcl-2 and p27 expression. The result of subsequent proteomic analysis of Bcl-2 overexpressing cells identified 169 upregulated and 120 downregulated proteins with a 1.5-fold change. These differentially expressed proteins were enriched in a number of signaling pathways predominantly involving the ribosome and oxidative phosphorylation, according to the data of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. These results indicated that Bcl-2 potentially acts at the translation level to influence proteins or enzymes of the respiratory chain or in the ribosome, and thereby regulates the cell cycle. Additionally, differentially expressed proteins involved in oxidative phosphorylation were determined to account for most of the effects of Bcl-2 on the cell cycle mediated by the mitochondrial pathway investigated in our previous study. These results can provide assistance for additional in-depth studies on the regulation of the cell cycle by Bcl-2. The results of the proteomic analysis determined the mechanism of Bcl-2-dependent delay of the cell cycle progression. In summary, the results of this study provide a novel mechanistic basis for identifying the key proteins or pathways for designing and developing precisely targeted cancer drugs.