We previously observed that treatment of the endometrial cancer-derived cell line ARK2 with the biguanide antidiabetes drug metformin results in a decrease in H19 levels and an increase in methylation within the promoter region of H19. 5 Whether these changes were mediated by the H19/SAHH axis, however, as previously had reported in normal mouse muscle cells8 was unclear. This evidence concerns the gene AHCY and endometrial cancer.