Tumor-specific metabolic rewiring, intended to confer a survival advantage over non-transformed cells, often offers an opportunity to target cancers. Here, we identify deregulated expression of purine biosynthetic enzymes as a metabolic hallmark in human hepatocellular carcinomas (HCC), with the extent of enzyme upregulation a predictor of clinical outcome. We demonstrate in HCC cell lines, patient-derived xenograft (PDX) organoids and mouse models that inhibition of purine biosynthesis abrogated cancer cell proliferation and tumor growth. Mechanistically, a PI3K-E2F1 axis coordinated purine biosynthetic enzyme expression. Clinically approved inhibitors against PI3K and the purine biosynthetic rate-limiting enzyme IMPDH synergistically reduced the tumor burden in a PDX mouse model. Collectively, our results support targeting purine metabolic reprogramming as a precision therapeutic strategy for HCC patients. Overall design: RNA-seq of sh-control, sh-IMPDH1 and sh-IMPDH2 in Huh7 cell line. Each condition has three biological replicates