To determine how particular cancer cells may prioritize each NAD+ biosynthetic route, an analysis of more than 7,000 tumors and 2,600 matched normal samples, spanning 19 tissue types, was conducted and concluded that tumors arising from normal tissues with increased NAPRT expression typically exhibit amplification of NAPRT, suggesting increased reliance on the Preiss-Handler pathway for NAD+ production. Here, NAPRT is linked to cancer.