A comprehensive analysis of the Cullin family reveals that CUL5 and CUL7 promote colorectal cancer progression and serve as prognostic markers

Colorectal cancer (CRC) remains a major cause of cancer-related mortality worldwide. Although Cullin family genes (CUL1, CUL2, CUL3, CUL4A, CUL4B, CUL5, CUL7, and CUL9) have been implicated in tumorigenesis, their roles in CRC are not fully defined. This study integrated in silico analysis with in vitro validation to characterize the expression and functional relevance of these genes in CRC. Transcriptomic profiling of TCGA datasets revealed significant up-regulation of CUL1, CUL2, CUL4A, CUL4B, CUL5, CUL7, and CUL9 in tumor tissues, with higher expression correlating with advanced stage and poorer survival, particularly for CUL5 and CUL7. Immunohistochemistry confirmed elevated protein levels, while genomic analysis showed that CUL9, CUL1, and CUL7 exhibited the highest mutation frequencies, though without significant survival impact. Single-cell and subtype analyses demonstrated distinct Cullin gene expression patterns across tumor-associated cell populations and immune or molecular subtypes. Functional enrichment indicated involvement in ubiquitin-mediated proteolysis and cancer-related pathways. Experimental knockdown of CUL5 and CUL7 in CRC cell lines significantly reduced proliferation and colony formation. ChIP-qPCR demonstrated increased H3K27ac enrichment at the CUL5 and CUL7 promoters in CRC cells, indicating epigenetic activation. Cycloheximide (CHX) chase assays further showed that silencing CUL5 or CUL7 accelerated the degradation of CREB1 and Cyclin D1, suggesting a role in substrate stabilization. Overall, our findings highlight the widespread up-regulation and functional significance of Cullin genes in CRC, with CUL5 and CUL7 emerging as key contributors to tumor progression and potential biomarkers or therapeutic targets.