DNA methylome profiling identifies novel methylated genes in epithelial ovarian cancer patients with platinum resistance.

Aim: Platinum-based chemotherapy is widely used for epithelial ovarian cancer (EOC). As high as 20-25% of EOC patients will not respond to the initial chemotherapy. Accumulated evidences have implied that DNA methylation may serve as a potential bio-marker for chemotherapy-resistant phenotypic screening; however, the pattern underlying primary platinum resistance remains unclear.

Methods: Reduced representation bisulfite sequencing (RRBS) analysis was performed to identify differences in methylation status between primary platinum-resistant patients Progression free survival (PFS) (PFS < 6 months, n = 8) and extreme sensitive patients (PFS ≥ 24 months, n = 8). The Qubit 3.0 Fluorometer was used for the quantification of RRBS library. The RRBS library was sequenced on Illumina HiSeq2500 sequencer as 50 bp paired-end reads.

Results: After screening, 94 valid hyper-/hypo-methylated regions were identified to be located within 94 gene promoter and exon regions (adjusted q ≤ 0.5), which were primarily associated with cell-cell adhesion, B cell activation and lymphocyte activation according to GO analysis. The 19 differentially methylated regions (DMR) located in the promoter region including TRC-GCA11-1, LOC105370912, ANO7P1, DHX4,MSH2, CDCP2, CCNL1, ARHGAP42P2, PRDM13, LOC101928344, USP29, ZIC5,IL1RAPL1, EVX2, ABR, MGRN1, UBALD1, LINC00261, and ISL2 were identified according to the order of P-values from low to high, of which MSH2, LINC00261, MGRN1, ZIC5, EVX2, CCNL1, and DHX40 were presented to play a variety of roles in cancers process based on the previous studies.

Conclusion: DNA methylome profiling based on RRBS assay is an effective method for screening aberrantly methylated genes in primary platinum-resistant patients, which may serve as a potential epigenetic bio-marker for the prediction of primary platinum resistance.