The key enzyme PYCR1 in proline metabolism: a dual driver of cancer progression and fibrotic remodeling.

Pyrroline-5-Carboxylate Reductase 1 (PYCR1), a member of the PYCR family, is a key enzyme in the proline biosynthesis pathway. Notably, PYCR1 was originally identified via genetic disease research, linking its mutations to the occurrence of cutis laxa. PYCR1 contributes to the pathogenesis of malignancies and fibrotic diseases via mechanisms involving metabolic reprogramming, Extracellular Matrix (ECM) remodelling, and redox homeostasis maintenance. PYCR1 upregulation has been reported in multiple malignancies including Hepatocellular Carcinoma (HCC), Lung Cancer (LC), Breast Cancer (BC), Bladder Cancer (BlC), and Gastric Cancer (GC), where it has been shown to promote cancer proliferation, migration, and therapy resistance, correlating significantly with advanced cancer stages and poor prognosis. On the other hand, in fibrotic disorders, PYCR1-mediated proline metabolism has been linked to the progression of pulmonary, myocardial, and cutaneous fibroses. Notably, although PYCR1-targeted small-molecule inhibitors have demonstrated therapeutic potential in preclinical studies, their clinical translation is yet to be validated.