Cell Division Cycle 7 (CDC7) is a serine/threonine kinase that plays a critical role in the initiation of DNA replication. In complex with its regulatory subunit DBF4, CDC7 phosphorylates components of the MCM2–7 helicase, enabling replication origin firing and S-phase entry. Tight regulation of CDC7 activity is essential for genome stability, as dysregulated origin firing can lead to replication stress and DNA damage. CDC7 is frequently overexpressed in multiple cancer types and is associated with increased proliferation, replication stress, and poor clinical prognosis. Tumor cells often exhibit heightened dependence on CDC7 activity to sustain oncogene-driven replication programs, making CDC7 an attractive therapeutic target.