The Two-Way Role of Jagged1 in Cancer: A Focus on CRC

Highlights: What are the main findings? Jagged1 is cleaved, releasing an intracellular domain (Jag1-ICD). Jag1-ICD acquires oncogenic properties in CRC. What are the implications of the main findings? Jagged1 is a novel oncogenic driver that contributes to the multistep genetic model underlying the adenoma-to-carcinoma sequence in CRC. Understanding the two-way role of Jagged1 could lead to new strategies for addressing drug resistance in CRC. Colorectal cancer (CRC) remains one of the most prevalent and lethal malignancies. Accumulating genetic evidence supports a multistep model of tumor progression, in which early APC loss leads to chromosomal instability and adenoma formation, followed by activating mutations in KRAS that synergize with β-catenin signaling to promote tumor growth and invasion. Among the downstream effectors of these pathways, the Notch ligand Jagged1 has emerged as a critical mediator of CRC progression and chemoresistance. Jagged1 is not only a transcriptional target of the Wnt/β-catenin axis but also undergoes proteolytic cleavage via the KRAS/ERK/ADAM17 signaling cascade, generating a nuclear Jagged1 intracellular domain (Jag1-ICD) that drives reverse signaling. This dual functionality, activating canonical Notch signaling and initiating reverse nuclear signaling, positions Jagged1 as a key oncogenic driver in CRC. In this review, we first summarize the role of Jagged1 as an integral part of canonical Notch signaling. We then focus on the non-canonical Jagged1 reverse signaling function in cancer, with a particular emphasis on CRC. We underscore the dual role of Jagged1 in tumor biology and propose that it functions as a novel oncogene within the adenoma-to-carcinoma sequence, supporting CRC development and drug resistance via non-canonical mechanisms.