Abstract
AbstractBackgroundDNA methylation alterations within theVMP1/MIR21gene region, a potential epigenetic biomarker of systemic inflammation, have been demonstrated in mononuclear blood cells from early breast cancer (BC) patients after chemotherapy. Whether these changes are present in granulocytes, persist in the years after treatment, and affectVMP1orMIR21gene expression, remains unknown.AimWe aimed to investigate whether adjuvant chemotherapy alters the DNA methylation and gene expression ofVMP1/MIR21in granulocytes from postmenopausal BC patients and, if so, whether these treatment-induced changes are reversible in the first two years after completed chemotherapy.MethodsWhole blood samples were obtained from 30 postmenopausal BC patients before chemotherapy and every six months for two years, and from 10 healthy age- and BMI-matched controls. DNA and RNA was extracted from isolated granulocytes, and DNA methylation of four CpG sites located in the gene body ofVMP1, which is situated in the promoter region ofMIR21, was assessed through bisulfite pyrosequencing. qPCR was used for assessment ofVMP1andMIR21expression.ResultsVMP1/MIR21was significantly demethylated in granulocytes from BC patients shortly after completed chemotherapy compared to before (10 percentage points decrease,p<0.0001). Six months thereafter, DNA methylation values were significantly increased (6 percentage points, p = 0.002), and they were further increased to pre-chemotherapy levels 12, 18 and 24 months post chemotherapy. Chemotherapy did not cause significant changes in the expression ofVMP1orMIR21.ConclusionThe unique follow-up samples in this study demonstrated that chemotherapy induced a transient reduction in DNA methylation of theVMP1/MIR21region in granulocytes from postmenopausal BC patients. Although transient, chemotherapy-induced epigenetic changes in blood cells may contribute to the increased risk of inflammatory-related comorbidities in BC survivors.
Publisher
Cold Spring Harbor Laboratory