Method
Search strategy
We searched the Pubmed and Embase exhaustively about what and how
individual factors influence the DNA methylation of genes related to
drug metabolism. Searches used the following title, abstract, keyword
and Medical Subject Headings (MeSH) terms: (1) DNA methylation; (2)
genes related to drug metabolism; (3) influence, related, affect,
factors. Reference lists of identified articles and reviews were also
searched for additional references. The search and filtering process was
done under the supervision of senior researchers.
Selection criteria
The studies were selected for inclusion if they fulfilled the following
criteria: (1) published from 2000 onwards. (2) published in English. (3)
experiments about people, mice or cells. (4) genes were involved in
metabolism. The reason why we choose experiment about people, mice and
cells was that we need findings to be used in clinical treatment. We
excluded the DNA methylation related to diseases because these genes
were often part of disease pathogenesis, hardly involved in metabolism,
and nearly have no influence on drug metabolism. Each reviewer screened
part of the publications independently with the inclusion and exclusion
criteria and inter-reviewer disagreement was discussed and resolved by a
senior author. More details are in Fig.1 about the selection process.
Data extraction
For the papers included, we extracted following information.
- Author.
- Year of publication.
- Research type.
- Methods for detection of methylation.
- Research object.
- Sample size.
- individual affect factor.
- Gene & CpG sites.
- Main result of the methylation.
Information was recorded by two authors independently and any
disagreement were discussed and resolved by a senior author. Complete
records were aggregated in appendix.