In a progestin-resistant Ishikawa cell line, sirtuin 1 (SIRT1) and SREBP-1 at the mRNA and protein levels are upregulated, while progesterone receptor and forkhead transcription factor 1 (FoxO1) are downregulated, suggesting that the SIRT1/FoxO1/SREBP-1 pathway is involved in the progestin resistance of endometrial cancer (123). Here, FOXO1 is linked to endometrial cancer.