<scp>FAM49B</scp> drives colorectal cancer progression by stabilizing c‐Myc through <scp>NEK9</scp> phosphorylation

Colorectal cancer (CRC) ranks as the third most prevalent cancer globally and is the second leading cause of cancer mortality. FAM49B, a member of the FAM49 gene family, is a recently identified, evolutionarily conserved gene. Emerging studies indicate that FAM49B plays a role in various cancers, though its specific mechanism in CRC remains largely unexplored. In this study, we observed that FAM49B was abnormally expressed in CRC tissues and cell lines, with elevated expression correlating with poor patient prognosis. FAM49B knockdown markedly suppressed CRC cell proliferation by arresting the cell cycle and reducing cell migration and invasion. Single-cell RNA-seq (ScRNA-seq) analysis revealed that high FAM49B expression in malignant epithelial cell clusters was strongly linked to c-Myc oncogene activation. Further, FAM49B knockdown significantly reduced c-Myc expression by enhancing its K48 ubiquitination. We identified NEK9 as a direct interacting partner of FAM49B, with FAM49B knockdown inhibiting NEK9-Thr210 phosphorylation. Similarly, high NEK9 expression was linked to unfavorable prognosis in CRC. In FAM49B-overexpressing CRC cells, NEK9 knockdown significantly suppressed c-Myc expression, c-Myc-ser62 phosphorylation, and reduced cell proliferation, migration, and invasion. Thus, directly targeting the FAM49B/NEK9/c-Myc pathway presents a promising therapeutic approach for c-Myc positive CRC patients.