Notably, overexpression of PRODH2, a gene of the proline cycle, has been found to enhance the metabolic fitness and anti-tumour efficacy of CAR-T cells in a mouse model (61) and high expression of Prodh and proline biosynthesis genes was found in clusters of 24-h-activated T cells in a recent single-cell RNA sequencing study (33). The gene discussed is PRODH; the disease is neoplasm.