Clinical significance and prospective mechanism of increased CDKN2A expression in small cell lung cancer

BACKGROUND

Although it has been shown that cyclin dependent kinase inhibitor 2A (CDKN2A) plays a significant role in a number of malignancies, its clinicopathological value and function in small cell lung cancer (SCLC) is unclear and warrants additional research.

METHODS

The clinical significance of CDKN2A expression in SCLC was examined by multiple methods, including comprehensive integration of mRNA level by high throughput data, Kaplan-Meier survival analysis for prognostic value, and validation of its protein expression using in-house immunohistochemistry.

RESULTS

The expression of CDKN2A mRNA in 357 cases of SCLC was evidently higher than that in the control group (n = 525) combing the data from 20 research centers worldwide. The standardized mean difference (SMD) was 3.07, and the area under the curve (AUC) of summary receiver operating characteristic curve (sROC) was 0.97 for the overexpression of CDKN2A. ACC, COAD, KICH, KIRC, PCPG, PRAD, UCEC, UVM patients with higher CDKN2A expression had considerably worse overall survival rates than those with lower CDKN2A expression with the hazard ratio (HR) > 1.

CONCLUSION

CDKN2A upregulation extensively enhances the carcinogenesis and progression of SCLC.

Cyclin-Dependent Kinase Inhibitor 2A is a Key Regulator of Cell Cycle Arrest and Senescence in Endothelial Colony-Forming Cells in Moyamoya Disease

OBJECTIVE

Endothelial colony-forming cells (ECFCs) have been reported to play an important role in the pathogenesis of moyamoya disease (MMD). We have previously observed stagnant growth in MMD ECFCs with functional impairment of tubule formation. We aimed to verify the key regulators and related signaling pathways involved in the functional defects of MMD ECFCs.

METHODS

ECFCs were cultured from peripheral blood mononuclear cells of healthy volunteers (normal) and MMD patients. Low-density lipoproteins uptake, flow cytometry, high content screening, senescence-associated β-galactosidase, immunofluorescence, cell cycle, tubule formation, microarray, real-time quantitative polymerase chain reaction, small interfering RNA transfection, and western blot analyses were performed.

RESULTS

The acquisition of cells that can be cultured for a long time with the characteristics of late ECFCs was significantly lower in the MMD patients than the normal. Importantly, the MMD ECFCs showed decreased cellular proliferation with G1 cell cycle arrest and cellular senescence compared to the normal ECFCs. A pathway enrichment analysis demonstrated that the cell cycle pathway was the major enriched pathway, which is consistent with the results of the functional analysis of ECFCs. Among the genes associated with the cell cycle, cyclin-dependent kinase inhibitor 2A (CDKN2A) showed the highest expression in MMD ECFCs. Knockdown of CDKN2A in MMD ECFCs enhanced proliferation by reducing G1 cell cycle arrest and inhibiting senescence through the regulation of CDK4 and phospho retinoblastoma protein.

CONCLUSION

Our study suggests that CDKN2A plays an important role in the growth retardation of MMD ECFCs by inducing cell cycle arrest and senescence.