| 摘要: | Colorectal cancer (CRC) is the second leading cause of cancer-related death in the world. It is still urgent to develop novel therapeutics. Human ribonucleotide reductase (RRM1/RRM2) plays an essential role in converting ribonucleoside diphosphate to 2’-deoxyribonucleoside diphosphate to maintain the homeostasis of nucleotide pools. RRM2 is a prognostic biomarker and predicts poor survival of CRC. Bioinformatics analyses show that RRM2 was overexpressed in CRC and might be an attractive target for treating CRC. Polypharmacology (the ability of a drug to affect more than one molecular target) is considered a basic property of many therapeutic small molecules. Herein, we used a chemical genomics approach to systematically analyze polypharmacology by integrating several analytical tools, including the gene expression signature-based approach, connectivity MAP (CMAP), LINCS (Library of Integrated Cellular Signatures), STITCH (Search Tool for Interactions of Chemicals), and WebGestalt (WEB-based GEne SeT AnaLysis Toolkit). We attempt to search novel RRM2 inhibitors by using a gene expression signature-based approach, connectivity MAP (CMAP). The result predicted GW8510, a cyclin-dependent kinase (CDK) inhibitor, as a potential RRM2 inhibitor. Western blot analysis indicated that GW-8510 inhibited RRM2 expression through promoting its proteasomal degradation. In addition, GW-8510 induced autophagic cell death. In addition, the sensitivities of CRC cells to GW8510 were associated with the levels of RRM2 and endogenous autophagic flux. Our study indicates that GW8510 could be a potential anti-CRC agent through targeting RRM2. We also applied this approach to identify functional disparities between two cytidine nucleoside analogs: azacytidine (AZA) and decitabine (DAC). AZA and DAC are structurally and mechanistically similar DNA-hypomethylating agents. However, their metabolism and destinations in cells are distinct. Due to their differential incorporation into RNA or DNA, functional disparities between AZA and DAC are expected. Indeed, different cytotoxicities of AZA and DAC toward human colorectal cancer cell lines were observed, in which cells were more sensitive to AZA. Based on a polypharmacological analysis, we found that AZA transiently blocked protein synthesis and induced an acute apoptotic response that was antagonized by concurrently induced cytoprotective autophagy. In contrast, DAC caused cell cycle arrest at the G2/M phase associated with p53 induction. Taken together, our studies showed the potential of bioinformatics strategy in predicting polypharmacology and facilitating drug repositioning. |
