Growth conditions of F9 embryonal carcinoma cells affect the degree of DNA methylation.

We have investigated differences in C pG methylation between F9 embryonal carcinoma cells in vitro and as tumor cells grown in vivo using Msp I and Hpa II restriction isoschizomers. Southerns were hybridized with two low copy number probes, mouse major beta-globin (f7) and a class I, histocompatibility-2 cDNA clone (pH-2d-4). In each case, the tumor-DNA was hypomethylated while the DNA from F9 cells grown in vitro was moderately methylated. We conclude that growth conditions or cell-cell interactions can greatly affect methylation of C pG sites.