CircSCAF8 promotes growth and metastasis of prostate cancer through the circSCAF8-miR-140-3p/miR-335-LIF pathway.

Circular RNAs (circRNAs) have been increasingly linked to cancer progression. However, the detailed biological functions of circRNAs in prostate cancer (PCa) remain unclear. Using high-throughput circRNA sequencing, we previously identified 18 urine extracellular vesicle circRNAs that were increased in patients with PCa compared with those with benign prostatic hyperplasia. Spearman correlation analysis of the expression levels of the 18 circRNAs between the tumor tissue and matched urine extracellular vesicles in 30 PCa patients showed that circSCAF8 had the highest R2 (R2 = 0.635, P < 0.001). The Cox proportional hazards regression model was used to estimate the effect of circSCAF8 on progression-free survival. The in vitro and in vivo functional experiments were implemented to investigate the effects of circSCAF8 on the phenotype of PCa. We found that the knockdown of circSCAF8 in PCa cells suppressed the proliferation, migration, and invasion ability, while overexpression of circSCAF8 had the opposite effects. Similar results were observed in vivo. In a cohort of 85 patients who had undergone radical prostatectomy, circSCAF8 expression in PCa tissues was a powerful predictor of progression-free survival (HR = 2.14, P = 0.022). Mechanistically, circSCAF8 can function by binding to both miR-140-3p and miR-335 to regulate LIF expression and activate the LIF-STAT3 pathway that leads to the growth and metastasis of PCa. Collectively, our findings demonstrate that circSCAF8 contributes to PCa progression through the circSCAF8-miR-140-3p/miR-335-LIF pathway.

ECRG4 acts as a tumor suppressor gene frequently hypermethylated in human breast cancer.

Human breast cancer is a malignant form of tumor with a relatively high mortality rate. Although esophageal cancer-related gene 4 (ECRG4) is thought to be a possible potent tumor suppressor gene that acts to suppress breast cancer, its precise role in this disease is not understood. Herein, we assess the correlation between ECRG4 expression and DNA methylation, probing the potential epigenetic regulation of ECRG4 in breast cancer. We analyzed ECRG4 promoter methylation via methylation-specific PCR (MSPCR), bisulfite sequencing, and a promoter reporter assay in human breast cancer cell lines and samples. Gene expression was assessed by quantitative real-time PCR (qPCR), while protein levels were assessed by Western blotting. CCK8 assays were used to quantify cell growth; Esophageal cancer-related gene 4 wound healing assays were used to assess cellular migration, while flow cytometry was used to assess apoptosis and cell cycle progression. Apoptosome formation was validated via CO-IP and Western blotting. We found that human breast cancer samples exhibited increased methylation of the ECRG4 promoter and decreased ECRG4 expression. Remarkably, the down-regulation of ECRG4 was highly associated with promoter methylation, and its expression could be re-activated via 5-aza-2'-deoxycytidine treatment to induce demethylation. ECRG4 overexpression impaired breast cancer cell proliferation and migration, and led to G0/G1 cell cycle phase arrest. Moreover, ECRG4 induced the formation of the Cytc/Apaf-1/caspase-9 apoptosome and promoted breast cancer cell apoptosis. ECRG4 is silenced in human breast cancer cells and cell lines, likely owing to promoter hypermethylation. ECRG4 may act as a tumor suppressor, inhibiting proliferation and migration, inducing G0/G1 phase arrest and apoptosis via the mitochondrial apoptotic pathway.