title: Confluence-induced alterations in CpG island methylation in cultured normal human fibroblasts.
abstract: Growth constraint of bacterial and human cells has been shown to trigger genetic mutation. We questioned whether growth constraint might also trigger epigenetic mutation in the form of CpG island methylation. Logarithmically growing normal human fibro-blasts (NHF) displayed little (0-15%) CpG methylation in select regions of three CpG islands [estrogen receptor (ER), E-cadherin (ECAD) and O (6)-methylguanine-DNA methyltransferase (MGMT)] examined. NHF grown to and left at confluence for 2-21 days showed little (<10%) CpG methylation in the ER and ECAD CpG islands. These confluent, growth-arrested cells, however, displayed extensive ( approximately 50%) methylation of the MGMT CpG island. CpG methylation in the MGMT CpG island was not associated with cellular senescence. The methylation was, however, heritable, but not permanent, as the level of CpG methylation in the MGMT CpG island of cells 4 population doublings following replating after confluence were no different from those in confluent cultures, but returned to levels noted in logarithmically growing cells by 10 population doublings following replating. These results suggest that growth constraint can trigger transient epigenetic change even in normal non-senescent human cells.
authors.affiliation: Department of Neurological Surgery and the UCSF Cancer Center, Room N261, 2340 Sutter Street, University of California-San Francisco, San Francisco, CA 94115-0128, USA. rpieper@cc.ucsf.edu
authors.forename: R O
authors.initials: RO
authors.lastname: Pieper
authors.forename: K A
authors.initials: KA
authors.lastname: Lester
authors.forename: C P
authors.initials: CP
authors.lastname: Fanton
mesh_terms: D015820:Cadherins / Q000235:genetics; D002452:Cell Count; D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D002461:Cell Line, Transformed; D016922:Cellular Senescence / Q000235:genetics; D018899:CpG Islands / Q000235:genetics*; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D019175:DNA Methylation; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011960:Receptors, Estrogen / Q000235:genetics; D013539:Simian virus 40; D013447:Sulfites; D013997:Time Factors
chemical_list: D015820:Cadherins; D011960:Receptors, Estrogen; D013447:Sulfites; D004247:DNA; D019853:O(6)-Methylguanine-DNA Methyltransferase; C009279:sodium bisulfite