Global Stability Profling of Colorectal Cancer Chemoresistance

Almost half of the patients with advanced colorectal cancer (CRC) are resistant to oxaliplatin based therapy, the first line treatment for CRC. Therefore, predicting and understanding oxaliplatin resistance is important to improve CRC patient survival. Investigated here is the use of proteomic folding stability measurements to differentiate oxaliplatin resistant and sensitive CRCs using patient-derived CRC cell lines and patient-derived xenografts (PDXs). Three protein stability profiling techniques (including the Stability of Proteins from Rates of Oxidation (SPROX), the Thermal Protein Profiling (TPP), and Limited Proteolysis (LiP) approaches) were employed to identify differentially stabilized proteins in 6 patient-derived CRC cell lines with different oxaliplatin sensitivities and 8 CRC PDXs derived from 2 of the patient derived cell lines with different oxaliplatin sensitivity. A total of 23 proteins were found in at least 2 techniques to be differentially stabilized in both the cell line and PDX studies of oxaliplatin resistance. These 23 differentially stabilized proteins included 9 proteins that have been previously connected to cancer chemoresistance. Over-representation analysis (ORA) of all the differentially stabilized proteins identified here, revealed novel pathways related to oxaliplatin resistance. Compared to conventional protein expression level analyses, which were also performed on the cell lines and PDXs, the stability profiling techniques identified novel proteins and pathways and provided new insight on the molecular basis of oxaliplatin resistance. Our results suggest that protein stability profiling techniques are complementary to expression level analyses for identifying biomarkers and understanding molecular mechanisms associated with oxaliplatin chemoresistance in CRC and disease phenotypes in general.