PROJECT SUMMARY Proline dehydrogenase (PRODH) and Δ1-pyrroline-5-carboxylate (P5C) reductase (PYCR) form a metabolic relationship known as the “proline cycle”, a novel pathway that impacts cellular growth and death pathways. The proline cycle is central to the metabolic shift that enables tumorigenesis and supports the metastatic cascade of cancer cells. PRODH is upregulated in metastasizing breast cancer cells, and PYCR1 is one of the most consistently upregulated enzymes across multiple cancer cell types. Thus, proline cycle enzymes have been proposed as potential cancer drug targets. A major goal of this project is to gain insight into whether these enzymes have binding sites that can be exploited for small molecule binding and establish target tractability, i.e., the likelihood of identifying modulators that interact effectively with these targets. Initial results are encouraging, as the chemical probes developed in the first phase of this project show activity in cellular and animal models of cancer. These results motivate our proposal to (1) develop new and more potent reversible inhibitors of PRODH and PYCR1, (2) explore the mechanism-based covalent inactivation of PRODH, and (3) define the mechanistic roles of the proline cycle using chemical probes in cancer cells. With these studies we will mechanistically dissect the role of proline metabolism in cancer progression. We expect this knowledge will in the long-term aid the development of new therapeutic strategies against cancer.

The enzymes of the proline cycle are central to the metabolic shift that occurs in cancer cells to enable tumorigenesis and metastasis. This project will develop chemical probes of proline cycle enzymes and use them to discover novel cellular mechanisms of proline metabolism in cancer. The proposed research is a key initial step in establishing the tractability of the proline cycle as a therapeutic target.