Increased CDCA2 Level Was Related to Poor Prognosis in Hepatocellular Carcinoma and Associated With Up-Regulation of Immune Checkpoints.

BACKGROUND

Cell division cycle-associated protein 2 (CDCA2) is a member of cell cycle-related proteins. CDCA2 plays a role in the regulation of protein phosphatase 1(PP1) γ-dependent DNA damage response (DDR) and H3 phosphorylation. CDCA2 promotes the tumorigenesis and development of several types of cancers by promoting the proliferation of tumor cells. However, the relationship between CDCA2 expression and the clinicopathological characteristics of hepatocellular carcinoma (HCC) is unknown.

METHODS

Gene expression information and clinical data were downloaded from The Cancer Genome Atlas (TCGA) database. The expression of CDCA2 and its correlation to clinical characteristics in HCC were analyzed. The expression level of CDCA2 was validated in HCC cell lines. The relationship between CDCA2 expression and the survival of patients with HCC was analyzed by using Kaplan-Meier method. The prognostic value of CDCA2 in HCC was estimated by Cox regression analysis. The expression difference of CDCA2 between HCC and normal tissues and its correlation to survival were verified in independent datasets. Gene set enrichment analysis (GSEA) was used to screen the CDCA2-related signaling pathways.

RESULTS

Cell division cycle-associated protein 2 expression was upregulated in HCC tissues ( < 0.001) and increased CDCA2 was correlated to increased T stage, pathologic stage, histologic grade, and alpha-fetoprotein (AFP) level ( < 0.001). In addition, CDCA2 was overexpressed in HCC cell lines HepG2 and LM3. High CDCA2 expression level was associated with poor overall survival [hazard ratio () = 1.69; 95% , 1.20-1.40, = 0.003], disease specific survival ( = 1.73; 95% , 1.11-2.71, = 0.016), and progress free interval ( = 1.74; 95% , 1.30-2.34, < 0.001). Overexpression of CDCA2 and its correlation to poor survival in HCC were verified in Gene Expression Omnibus (GEO) datasets and Kaplan-Meier plotter database. Increased CDCA2 expression was associated with upregulation of PD-L1 (Spearman's coefficient = 0.207, < 0.001), PD-L2 (Spearman coefficient's = 0.118, < 0.05), and CTLA4 (Spearman's coefficient = 0.355, < 0.001). GSEA showed that homologous recombination pathway, insulin signaling pathway, mitogen-activated protein kinase (MAPK) pathway, mismatch repair pathway, mechanistic target of rapamycin (mTOR) pathway, Notch pathway, T cell receptor pathway, toll like receptor pathway, and WNT pathway were enriched in CDCA2 high expression phenotype.

CONCLUSION

Cell division cycle-associated protein 2 may serve as an independent biomarker for poor prognosis in HCC and increased CDCA2 expression was associated with upregulation of immune checkpoints.