PYCR2 and cancer: PYCR2, an enzyme that catalyzes the synthesis of l-proline from Δ1-pyrroline-5-carboxylate (P5C), was reported to promote cancer growth and inhibit apoptosis through multiple approaches, such as regulation of cell cycle and redox homeostasis and promotion of growth signaling pathways (Meng et al., 2017; Escande-Beillard et al., 2020; Li et al., 2021).