DNA methylation is one of the most important epigenetic mechanism and molecular biological basis in tumor suppressor gene silencing.It is now well recognized that solid malignant tumors can release a significant amount of genomic DNA into systemic circulation,and with more than 90％ of this total circulating cell-free DNA derived from tumor tissue,which can reflect the overall cell heterogeneity of the tumor itself.In breast cancer,the presence of abnormally high DNA concentrations in plasma has been reported,and changes in the levels of these circulating DNA associated with tumor burden and progression have been confirmed repeatedly.Accumulating data strongly suggested that DNA methylation patterns found in circulating cell free DNA were similarly with the primary tumor,and could be a useful biomarker in early diagnosis,prognosis assessment,and recurrence monitoring for breast cancer patients.Here,we summarize the latest advances in this research field.

Objective To conduct a screening survey of glycophorin (GP) variants and observe the content changes of sialic acid (SA) and total sulfhydryl (SH) groups on the erythrocyte membranes among residents in a tertian malaria hyperendemic area of Guizhou Province.Methods GP variants were detected in the erythrocyte hemolysates of 173 local residents at two villages of Libo County by SDS-PAGE on 10% to 15% gradients gel and Western immunoblotting. Their SA and total SH group contents were estimated in erythrocyte membranes by spectrophotometric methods. 114 healthy subjects in Changsha and 49 individuals at a neighbouring village of the above area showing low morbidity of malaria served as normal and endemic controls respectively.Results Three distinct types of GP variants were found among 19 propositi in this hyperendemic area. The incidence of GP variants was 7.9% (8/101) at Yaolu Village whose population was mainly composed of Yao ethnic group;while that of Buyi ethnic group at Maolan Village was higher (15.3%; 11/72).The erythrocyte membrane contents of SA in residents at both villages exhibited a very significant tendency of decline (P<0.01), whereas those of total SH groups increased prominently in residents of Yaolu Village only (P<0.05).Conclusions The frequency of GP variants in this hyperendemic area does not depend upon the severity of malarial prevalence. The evident reduction of SA contents in the residents may be related to the breaking down of the SA residues on membrane GPs by the invasion of Plasmodium vivax.