Project description:Oxaliplatin resistance was induced in 2 colorectal cancer cell lines (LoVo-92, wt-p53 and LoVo-Li, functionally inactive p53) and one ovarian cancer cell line (A2780, wt-p53). Resistance was induced by weekly exposure to oxaliplatin for 4 hrs or 72 hrs with increasing concentrations for a period of 7 months Genomic DNA of oxaliplatin and cisplatin resistant colorectal cancer and ovarian cancer cell lines as well as the parental cell lines were labeled and subsequently hybridized against pooled reference DNA of healthy volunteers of the opposite gender using across array hybridization. Extracted raw-data were normalised and smoothend using the R-script NOWAVE resulting in normalised log2 ratio profiles of resistant cell line versus parental cell line and parental cell line versus reference DNA.
Project description:Oxaliplatin resistance was induced in 2 colorectal cancer cell lines (LoVo-92, wt-p53 and LoVo-Li, functionally inactive p53) and one ovarian cancer cell line (A2780, wt-p53). Resistance was induced by weekly exposure to oxaliplatin for 4 hrs or 72 hrs with increasing concentrations for a period of 7 months.
Project description:Oxaliplatin resistance was induced in 2 colorectal cancer cell lines (LoVo-92, wt-p53 and LoVo-Li, functionally inactive p53) and one ovarian cancer cell line (A2780, wt-p53). Resistance was induced by weekly exposure to oxaliplatin for 4 hrs or 72 hrs with increasing concentrations for a period of 7 months
Project description:Purpose: Irinotecan (SN38) and oxaliplatin are chemotherapeutic agents used in the treatment of colorectal cancer. However, the frequent development of resistance to these drugs represents a considerable challenge in the clinic. Alus as retrotransposons comprise 11% of the human genome. Genomic toxicity induced by carcinogens or drugs can reactivate Alus by altering DNA methylation. Whether or not reactivation of Alus occurs in SN38 and oxaliplatin resistance remains unknown. Methods: We applied reduced representation bisulfite sequencing (RRBS) to investigate the DNA methylome in SN38- or oxaliplatin-resistant colorectal cancer cell line models. Moreover, we extended the RRBS analysis to tumor tissue from 14 patients with colorectal cancer who either did or did not benefit from capecitabine + oxaliplatin treatment. For the clinical samples, we applied a concept of DNA methylation entropy to estimate the diversity of DNA methylation states of the identified resistance phenotype-associated methylation loci observed in the cell line models. Results: We identified different loci being characteristic for the different resistant cell lines. Interestingly, 53% of the identified loci were Alu sequences -- especially the Alu Y subfamily. Furthermore, we identified an enrichment of Alu Y sequences that likely results from increased integration of new copies of Alu Y sequence in the drug-resistant cell lines. In the clinical samples, SOX1 and other SOX gene family members were shown to display variable DNA methylation states in their gene regions. The Alu Y sequences showed remarkable variation in DNA methylation states across the clinical samples. Our findings imply a crucial role of Alu Y in colorectal cancer drug resistance. Our study underscores the complexity of colorectal cancer aggravated by mobility of Alu elements and stresses the importance of personalized strategies, using a systematic and dynamic view, for effective cancer therapy. Investigation of the representive methylome of well-established SN38 and Oxaliplatin resistant cell line models and 14 clinical colorectal metastatic samples that have developed resistance to XELOX to review the epigenetic mechnism of the drug resistance.
Project description: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.