Abstract
Tumor cells adapt to their high metabolic state by increasing energy production. To this end, current efforts in molecular cancer therapeutics have been focused on signaling pathways that modulate cellular metabolism. However, targeting such signaling pathways is challenging due to heterogeneity of tumors and recurrent oncogenic mutations. A critical need remains to develop antitumor drugs that target tumor specific pathways. Here, we discuss an energy metabolic pathway that is preferentially activated in several cancers as a potential target for molecular cancer therapy.In vitrostudies have revealed that many cancer cells synthesize guanosine triphosphate (GTP), via thede novopurine nucleotide synthesis pathway by upregulating the rate limiting enzyme of this pathway, inosine monophosphate dehydrogenase (IMPDH). Non-proliferating cells use an alternative purine nucleotide synthesis pathway, the salvage pathway, to synthesize GTP. These observations pose IMPDH as a potential target to suppress tumor cell growth. The IMPDH inhibitor, mycophenolate mofetil (MMF), is an FDA-approved immunosuppressive drug. Accumulating evidence shows that, in addition to its immunosuppressive effects, MMF also has antitumor effects via IMPDH inhibitionin vitroandin vivo. Here, we review the literature on IMPDH as related to tumorigenesis and the use of MMF as a potential antitumor drug.
Highlights
Metabolic regulation in tumors is different from resting adult tissues
We review the current literature on the role of the rate-limiting enzyme of the guanosine triphosphate (GTP) nucleotide synthesis pathway, inosine monophosphate dehydrogenase (IMPDH), in various malignancies
We review the body of work that has explored the role of FDA-approved IMPDH inhibitor, mycophenolate mofetil (MMF), as an antitumor drug
Summary
Metabolic regulation in tumors is different from resting adult tissues. Tumor cells increase synthesis of proteins, lipids, and nucleotides to adapt to their rapid proliferation. Phosphatidylinositol 3kinase (PI3K) and mammalian target of rapamycin (mTOR) signaling pathways are established oncogenic drivers in a variety of cancers [1]. These signaling pathways lead to increased glucose uptake and many anabolic processes, such as lipid biosynthesis and protein and nucleotide synthesis [2]. GTP upregulation may reflect the increased need for protein synthesis in tumor cells as opposed to resting, noncancerous cells. The knowledge of these two important aspects of GTP raises the following questions. We review the body of work that has explored the role of FDA-approved IMPDH inhibitor, mycophenolate mofetil (MMF), as an antitumor drug
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