Tumor suppressive ZBTB4 inhibits cell growth by regulating cell cycle progression and apoptosis in Ewing sarcoma

Increasing studies identify that zinc finger and BTB domain containing 4 (ZBTB4) functions as a tumor suppressor in human cancer. Underexpression of ZBTB4 is correlated with poor survival of breast cancer patients. However, the expression of ZBTB4 and its possible function remain unknown in Ewing sarcoma (ES). To clarify these issues, we investigated the expression difference between ES and normal tissues based on Gene Expression Omnibus (GEO) data from R2: Genomics Analysis and Visualization Platform (http://r2.amc.nl). GEO data (GSE68776) indicated that the expression of ZBTB4 in ES tissues was prominently lower compare to normal tissues. Our data further confirmed the underexpression of ZBTB4 in ES tissues. GEO data (GSE63157 and GSE17679) demonstrated that ZBTB4 underexpression predicted a obvious shorter overall survival and event-free survival of ES patients. Interestingly, the expression of ZBTB4 was inversely correlated with proliferation makers Ki-67 and proliferating cell nuclear antigen (PCNA) in ES tissues. In vitro, ZBTB4 overexpression inhibited cell proliferation, and induced cell cycle arrest at G1 phase and apoptosis in SK-ES-1 and RD-ES cells. Moreover, ZBTB4 restoration suppressed the tumor growth of ES in mice. An inversely correlation between ZBTB4 and Survivin expression was observed in ES tissues. ZBTB4 overexpression reduced Survivin abundance in ES cells. Notably, Survivin restoration reversed the regulatory effect of ZBTB4 on ES cell proliferation, cell cycle progression and apoptosis. To conclude, our data indicated that ZBTB4 exhibited a tumor suppressive role in ES possibly by reducing Survivin expression. ZBTB4/Survivin axis might serve as a therapeutic target for ES.