E2F1 and neoplasm: Importantly, we demonstrate that high E2F1 expression is mechanistically linked to increased tumor stemness, a relationship validated not only in clinical cohorts (Figs. 3S-U and 4A, S2K, S2N) but also functionally supported by our in vivo nude mouse tumor formation assays, where tumors driven by E2F1 exhibited enhanced tumorigenicity, mirroring the stemness phenotype observed in patients.