Downregulation of the Helicase Lymphoid-Specific (HELLS) Gene Impairs Cell Proliferation and Induces Cell Cycle Arrest in Colorectal Cancer Cells.

Aim: Colorectal cancer (CRC) is the fourth most frequently diagnosed cancer worldwide. Despite the decrease in mortality of CRC patients, further investigation of the molecular pathogenesis of CRC could unveil new therapeutic targets and offer better prognosis predictions, which might direct attention to epigenetic regulators.

Methods: Publicly available data from the Gene Expression Omnibus (GEO) database and clinical samples were collected. Bioinformatics methods were used to screen hub genes expressed in CRC. qRT-PCR and Western blotting were used to experimentally determine the expression of one gene of interest, the helicase lymphoid-specific (HELLS) gene, at the RNA and protein levels. Immunohistochemical (IHC) assays were used to correlate the stained HELLS proteins to survival data. Cell proliferation levels were assayed by a CCK-8 kit, a colony formation assay was performed, and flow cytometry was used to quantify the cells at each stage of the cell cycle.

Results: A total of 225 overlapping genes were screened, including 14 hub genes. Analysis through a protein-protein interaction (PPI) network and the Gene Ontology database was performed by using the Cytoscape and DAVID online tools, respectively. HELLS RNA and protein expression levels in tumor tissues were 2.09-fold higher and 1.46-fold higher, respectively, than in the peritumoral tissues (p < 0.001, p<0.001). HELLS expression was significantly associated with the T stage (p=0.0027), M stage (p=0.0119), and TNM clinical stage (p = 0.0312) and a higher pathological grade (p=0.049). Highly expressed HELLS was reversibly associated with overall survival (log-rank p = 0.027). HELLS siRNA impaired cell proliferation and colony generation in vitro. HELLS siRNA induced significant G2+M arrest in HT29 and HCT116 cells compared with the respective negative controls (82.29% vs 25.85% and 35.41% vs 15.26%, respectively).

Conclusion: Our data revealed that HELLS was significantly upregulated in CRC and correlated with clinicopathological parameters. High expression of HELLS indicated poor prognosis for CRC patients. HELLS knockdown led to impaired cell proliferation, colony generation, and G+M cell cycle arrest.