Primary tumors gradually accumulate genetic alterations and are influenced by their microenvironment until they acquire the ability to metastasize to distant organs. Typical of this process, colorectal cancer (CRC) progresses through an adenoma-to-carcinoma sequence that eventually leads to metastasis, preferentially (~70% patients) to the liver. At this phase, the disease becomes challenging to treat and eventually develops resistance to most forms of combination therapy, making CRC metastasis a leading cause of cancer-related deaths. Patients with inoperable liver metastasis respond poorly to chemotherapeutic intervention and have a median survival of 6 to 9 months. Liver lesions have also been shown to seed tertiary tumors in the lungs of patients. Current chemotherapy for advanced CRC does not target liver metastases specifically. This is partly based on observations that CRC metastases are not consistently associated with any specific genetic mutations and they generally resemble cells in the primary tumor. However, emerging evidence suggests that nongenetic alterations, such as epigenetic and metabolic reprogramming, may promote cancer metastasis, including CRC. Targeting such mechanisms may provide a way to enhance therapeutics against metastasis.
In this study, pair-wise analysis of 90 matched samples (normal colon, primary CRC, liver metastasis) from 30 Stage IV CRC patients and an in vivo CRC metastasis model via cecum transplantation suggests that CRC liver metastases alter activity levels of certain metabolic pathways. LC-MS based metabolomics systematically mapped the altered metabolic pathways in CRC liver metastasis. In particular, via hypoxia-responsive GATA6 and fructose-responsive ChREBP, liver metastases upregulate ALDOB, an enzyme involved in fructose metabolism, given that 70% of fructose is metabolized in the liver. Intrahepatic implantation indicates that the liver environment causes CRC cells to upregulate ALDOB. Metabolomics and 13C-labeled fructose tracing studies indicate that ALDOB promotes fructose metabolism to fuel glycolysis, gluconeogenesis and the pentose phosphate pathway. Fructose also triggered downstream signaling to enhance lipid synthesis. ALDOB silencing or dietary fructose restriction suppresses growth of CRC liver metastases, but not primary tumors or lung metastases, highlighting the importance of tumor environment. Our findings suggest that metastatic cells can take advantage of abundant metabolites in their new microenvironment, and manipulation of involved pathways impacts the course of metastatic growth.
Citation Format: Xiling Shen. Targeting fructose-induced metabolic reprogramming in liver metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5479.