Epigenetic changes associated with inflammation in breast cancer patients treated with chemotherapy

Abstract

Inflammation has been associated with fatigue during and after various types of breast cancer treatments. We examined whether prior chemotherapy was associated with DNA methylation patterns that could explain persisting inflammation and/or fatigue in women treated for breast cancer. Prior to breast radiation therapy, DNA was extracted from peripheral blood mononuclear cells (PBMCs) of 61 Stage 0-IIIA breast cancer patients who had received partial mastectomy with or without chemotherapy. DNA methylation was assessed at >485,000 CpG sites across the genome along with fatigue and plasma inflammatory markers previously associated with fatigue. Compared to non-chemotherapy-treated, women who had received chemotherapy exhibited significantly decreased methylation at eight CpG sites (p<1.03×10(-7)) including four in exon 11 of transmembrane protein 49 (TMEM49), which demonstrated the largest decreases in methylation. Lower methylation at each identified CpG site was associated with increased plasma soluble tumor necrosis factor receptor 2 (sTNFR2) and interleukin (IL)-6 and mediated the relationship between chemotherapy and increases in these inflammatory biomarkers adjusting for multiple clinical and treatment characteristics. sTNFR2, but not CpG methylation status, was correlated with fatigue. Six months after breast radiation therapy, DNA methylation, inflammatory biomarkers and fatigue assessments were repeated in a subset of subjects (N=39). Reduced methylation in 4 of the 8 identified CpG sites was still observed in chemotherapy versus non-chemotherapy-treated patients, albeit with some decay indicating the dynamic and potentially reversible nature of the changes. Reduced methylation in these 4 CpG sites also continued to correlate with either increased sTNFR2 or IL-6, but not fatigue. In conclusion, prior chemotherapy treatment was associated with decreased methylation of CpG sites in DNA from PBMCs of breast cancer patients, which correlated with increased inflammatory markers prior to and 6months after radiation therapy. Persisting epigenetic changes secondary to chemotherapy may be one factor that contributes to inflammation and its consequences including cancer-related fatigue in vulnerable breast cancer patients.

Keywords: Breast cancer treatment; Epigenetics; Fatigue; Inflammation.

Conflict of interest statement

Conflicts of interest

None.

Copyright © 2014. Published by Elsevier Inc.

Figures

Fig. 1

Flow diagram of study participants. *Although 61 patients were enrolled at baseline, in order to confirm the observed epigenetic changes, we decided to consent patients for follow-up assessments at 6 months. Once Emory IRB approval for the follow-up was obtained, 39 of the 61 patients were eligible for assessments at this timepoint.

Fig. 2

Manhattan plot depicting the association of all CpG sites with chemotherapy.

Fig. 3

Distribution of methylation proportions in chemotherapy and non-chemotherapy-treated breast cancer patients at baseline and 6 months after radiation treatment.

Fig. 4

Relationship between plasma cytokine concentrations and methylation status of cg12054453 in exon 11 of TMEM49 at baseline (N = 61) and 6 months after radiation (N = 39).

Fig. 5

Relationship between methylation status of cg12054453 in exon 11 of TMEM49 at baseline and 6 months after radiation.