Reprogramming of creatine metabolism in breast cancer metastasis

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Metabolic reprogramming is a hallmark of cancer, enabling cancer cells to rapidly proliferate, invade, and metastasize. Several key enzymes have been identified that modulate cancer metabolism. These include enzymes in glucose, amino acid, nucleic acid, and lipid metabolism, including lactate dehydrogenase A, glutaminase 1, thymidylate synthase, and choline kinase alpha, to name just a few. Ubiquitous mitochondrial creatine kinase 1 (CKMT1) is emerging as a novel key enzyme in creatine metabolism of cancer. Few studies to date have investigated the role of CKMT1 in cancer, and the specific role of CKMT1 in breast cancer migration, invasion and metastasis remains largely unknown. To close this knowledge gap, we seek to investigate reprogramming of creatine metabolism in breast cancer. Our preliminary data show that CKMT1 drives cellular creatine (Cr) and phosphocreatine (PCr) concentrations and activates glycolysis in breast cancer cells. We consistently show in cell lines, mouse models, and patients that creatine metabolite levels along with CKMT1 expression are downregulated in metastatic breast cancer cells and metastatic tumor tissues. Overexpression of CKMT1 in metastatic breast cancer cells reduces migration, invasion, and metastasis, while increasing proliferation and primary tumor growth. Silencing of CKMT1 in nonmetastatic breast cancer cells increases migration and invasion, which occurs through generation of reactive oxygen species (ROS) that upregulate adhesion and degradative factors, epithelial-to-mesenchymal transition (EMT), and signaling pathways. In Aim 1, we will rigorously investigate the cause-and-effect relationships between reprogramming of creatine metabolism, related molecular pathways, and metastasis-driving cancer cell properties. In Aim 2, we will assess if genes/enzymes and related molecular pathways responsible for reprogramming creatine metabolism drive primary tumor growths and metastasis in mouse models of breast cancer. Our preliminary data show that CKMT1 expression was significantly decreased in clinical breast cancer metastases as compared to primary breast tumors. In Aim 3, we will further investigate in unique single-patient tissue microarrays (TMAs) from our rapid autopsy program how creatine metabolic enzyme expression levels and creatine metabolites, as well as related molecular pathways, are affected when breast cancers metastasize in patients. In our three Aims, we will test our overall hypothesis that reprogramming of creatine metabolism participates in driving breast cancer metastasis. Our preliminary findings provide evidence that creatine metabolism, and in particular CKMT1, holds promise as prognostic indicator and potential therapeutic target for metastatic breast cancer. Our proposal will significantly advance our understanding of reprogramming of creatine metabolism in tumor progression and metastasis. We will develop integrated multiplex matrix-assisted laser desorption/ionization imaging and immunohistochemistry approaches to detect creatine enzymes and metabolites in breast cancer specimens for future use in pathology workflows.