A study had compared the whole genome methylation levels of tumor cells in brain metastases of nude mice with those of subcutaneous tumor models of melanoma, lung cancer, stomach cancer, and other cell lines; the methylation levels of a series of transcription factors such as transcription factor 4, purine rich element binding protein B, one cut homeobox 2, estrogen related receptor gamma, nuclear factor IB, and myocyte enhancer factor 2C were found to differ significantly in the brain metastases model. The gene discussed is ESRRG; the disease is neoplasm.