Proteomic profiling of FOLFOX-resistant colorectal cancer cells.

Abstract

e15588 Background: Chemoresistance is a major cause of colorectal cancer (CRC) mortality. Although multidrug regimen has been established as the backbone of CRC chemotherapy for better treatment efficacy, chemoresistance is common among late-stage CRC. Proteomic profiling of both the chemoresistant and wild-type CRC cells may provide hints for the mechanisms of chemoresistance and suggest targets for improving chemotherapy efficacy. Methods: Human CRC cell lines (DLD-1 and HCT-116) were treated with progressively increased dosage of FOLFOX (5-flurouracil (5-FU), folinic acid (LEU) and oxaliplatin (OXA)) to develop chemoresistance as DLD-1-R and HCT-116-R respectively. After confirmation of the successful development of chemoresistance by Cell Counting Kit-8 test (CCK-8), the comparison of cell samples between chemoresistant and wild-type cell lines were conducted by proteomic profiling using quantitative mass spectrometry (MS)-based techniques. MS and MS/ MS peptides spectra were analysed by Progenesis QI for proteomics software compared with Swiss-Prot dataset. Differentially expressed proteins (DEP) are defined as -1 > log2FC > 1, p < 0.05. Gene-list enrichment by Enrichr (https://maayanlab.cloud/Enrichr/) was employed for identifying the hallmark gene sets of the significantly enriched molecular processes and pathways of each group. All experiments were performed with at least 3 replications. Results: The development of FOLFOX-resistance took one year. The highest drug concentrations achieved were 0.5mM 5-FU, 50µM LEU, and 50µM OXA for DLD-1-R, and 5µM 5-FU, 0.5µM LEU, and 0.5µM OXA for HCT-116-R. The chemoresistance was found to be 14.73 (DLD-1-R) and 1.61 (HCT-116-R) times of the wild-type DLD-1 and HCT-116 respectively from CCK-8 tests. A total of 345 DEP with 154 up-regulated and 191 down-regulated proteins were found in DLD-1-R. While a total of 95 DEP with 66 up-regulated and 29 down-regulated proteins were found in HCT-116-R. Gene ontology molecular process (2021) analyses found that cadherin binding were significantly enriched in both DLD-1-R and HCT-116-R (Adjusted p-value < 0.05). KEGG pathway (2021) analysis found that oxidative phosphorylation, regulation of actin cytoskeleton and HIF-1 signalling pathway are among the significantly enriched pathways in DLD-1-R (Adjusted p value < 0.05). There was no significantly enriched pathway found in HCT-116-R in the same analysis. Conclusions: Our study has successfully established CRC cells with chemoresistance to the FOLFOX regimen. Proteomic profiling has found the cadherin binding as the significantly altered molecular process along with several important signalling pathways in chemoresistant CRC cells. These findings could suggest new directions in the development of anti-chemoresistance strategies of CRC.