Project Summary/Abstract Liver metastasis is a steep obstacle for curative cancer treatment. Several cancers including prostate (PCa), colorectal (CRC) and pancreatic ductal adenocarcinoma (PDAC) commonly metastasize to this site. Data shows that liver metastasis is promoted by endocrine signaling from the primary tumor which can transform the liver microenvironment. Nonetheless, this pre-metastatic to post-metastatic niche transformation can also be influenced by therapy and diet. The ketogenic diet (KD) is a high-fat carb-restrictive diet that mimics fasting by making fatty acids the main source of energy and promoting beta hydroxy butyrate (βHB) synthesis (ketosis). KD has been successfully used to aid patients with neurodegenerative diseases. Additionally, it has been proposed to ameliorate different types of cancer by inducing a reverse-Warburg effect and sensitizing cells to checkpoint inhibitors. However, reports show that βHB enables adaptability to nutritional stress in cancer stem cells and is associated with tumor progression and staging of prostate cancer. Nevertheless, βHB is also a reported tumor suppressor being a known HDAC inhibitor and a signaling molecule through the niacin receptor, GPR109a, in colon and breast cancer cells. Understanding that the liver is the main βHB synthesis organ, in this study we aim to elucidate the effects of a ketogenic metabolism affecting the liver premetastatic niche and its paradoxical roles with PCa and CRC in their distinct metabolic reprogramming.