ODC1 and neoplasm: Using shRNA lentiviral particles targeting ODC1, the gene that encodes ornithine decarboxylase (ODC) — the rate-limiting irreversible enzyme of the main polyamine biosynthesis pathway — we knocked down ODC1 in SB28 tumor cells (Figure 5A), which resulted in decreased SPD production (Figure 5B) and no significant changes in intrinsic tumor cell growth (Figure 5C).