Pyrroline-5-carboxylate reductase 1 (PYCR1), which catalyzes the last step in proline biosynthesis, was reported to be overexpressed in multiple cancers including PCa, and it had a critical function in promoting tumor progression and cancer cell survival in PCa cells, indicating the essential role of proline in cancer cell growth and survival [48]. Here, PYCR1 is linked to cancer.