長崎 瑛里

TFAP2E is a member of the activator protein-2 transcription factor family and acts as a tumor suppressor in several types of cancer. Downregulation of TFAP2E expression is significantly associated with a shorter overall survival period in patients with oral squamous cell carcinoma (OSCC). To evaluate the molecular mechanisms by which TFAP2E suppresses the development or progression of OSCC, the present study investigated the effects of TFAP2E downregulation on OSCC-derived Ca9-22 and HSC-4 cells. The present study demonstrated that small interfering RNA mediated-knockdown of TFAP2E accelerated the proliferation of these OSCC cell lines compared with that in the control group, as determined by the standard water-soluble tetrazolium salt-8 assay. To analyze the cell cycle progression rate, the cell cycle distribution patterns of TFAP2E-knockdown and control cells cultured in the presence of nocodazole, which prevents the completion of mitosis, were analyzed by fluorescence-activated cell sorting at different time points. When analyzing cellular DNA contents, no major differences in cell cycle profiles were observed; however, the rate of increase in cells positive for histone H3 Serine 28 phosphorylation, a standard molecular marker of early M phase, was significantly higher in TFAP2E-knockdown cells than in the control cells. Collectively, these results suggested that TFAP2E may attenuate the proliferation of OSCC cells by regulating G2/M transition.

PURPOSE: Rhabdoid tumor of the kidney (RTK) is a rare, highly aggressive pediatric renal tumor. No specific biomarkers are available for detection of RTK, and the initial differential diagnosis from other pediatric abdominal tumors, including neuroblastoma (NB), is difficult. Exosomal miRNAs are novel cancer biomarkers that can be detected in biological fluids. We explored candidate RTK-specific exosomal miRNAs as novel biomarkers of RTK. METHODS: Exosomal miRNAs were collected from conditioned media of human RTK-derived cell lines, a human embryonic renal cell line, and human NB-derived cell lines. miRNA sequencing (miRNA-Seq) was performed to detect candidate RTK-specific exosomal miRNAs. The exosomal miRNA expression in conditioned media of tumor cell lines and serum from RTK xenograft-bearing mice was analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). RESULTS: The expression of exosomal miR-214-3p detected by miRNA-Seq was highest in RTK-derived cell lines. Exosomal miR-214-3p expression level determined by qRT-PCR was significantly higher in RTK-derived cell lines than in the human embryonic renal cell line or NB-derived cell lines. Furthermore, the serum exosomal miR-214-3p expression level was significantly higher in RTK xenograft mice than controls. CONCLUSION: Our data indicated that exosomal miR-214-3p has potential as a novel biomarker of RTK.

Neuroblastoma (NB) is a childhood malignancy originating from the sympathetic nervous system, and accounts for approximately 15% of all pediatric cancer-related deaths. As the 5-y survival rate of patients with high-risk NB is <50%, novel therapeutic strategies for NB patients are urgently required. Nonaethylene glycol mono('4-iodo-4-biphenyl)ester (9bw) is a polyethylene glycol derivative, synthesized by modifying a compound originally extracted from filamentous bacteria. Although 9bw shows remarkable inhibition of tumor cell growth, the underlying mechanisms remain unclear. Here, we examined the efficacy of 9bw on human NB-derived cells, and investigated the molecular mechanisms underlying the cytotoxic effects of 9bw on these cells. Our results indicated that 9bw induced cell death in NB cells by decreasing the production of ATP. Metabolome analysis and measurement of oxygen consumption indicated that 9bw markedly suppressed oxidative phosphorylation (OXPHOS). Further analyses indicated that 9bw inhibited the activity of mitochondrial respiratory complex I. Moreover, we showed that 9bw inhibited growth of NB in vivo. Based on the results of the present study, 9bw is a good candidate as a novel agent for treatment of NB.

Although DNA hypermethylation at non-promoter region of the Zygote arrest 1 (ZAR1) gene has been observed in many types of tumor, including neuroblastoma (NB), the role of this gene in tumor development and/or progression is unclear. One reason is that knowledge about the function of ZAR1 protein is limited. Although it has been reported that ZAR1 plays a crucial role in early embryogenesis and may act as a transcriptional repressor for some transcripts, the detailed mechanism is still elusive. In the present study, we analyzed public data of NB patients and found that higher expression levels of ZAR1 were significantly associated with a shorter survival period. Consistent with this result, ZAR1-depleted NB cells showed well-differentiated phenotypes with elongated neurites and upregulated expression of TRKA and RET, which are markers for differentiated NB. Moreover, the expression level of MYCN protein was markedly suppressed in ZAR1-depleted NB cells. MYCN-depleted cells showed similar phenotypes to ZAR1-depleted cells. The present findings indicate that ZAR1 has oncogenic effects in NB by suppressing cell differentiation via regulation of MYCN expression.

Neuroblastoma is a childhood malignancy originating from the sympathetic nervous system and accounts for approximately 15% of all pediatric cancer -related deaths. To newly identify gene(s) implicated in the progression of neuroblastoma, we investigated aberrantly methylated genomic regions in mouse skin tumors. Previously, we reported that TFAP2E, a member of activator protein -2 transcription factor family, is highly methylated within its intron and its expression is strongly suppressed in mouse skin tumors compared with the normal skin. In the present study, we analyzed public data of neuroblastoma patients and found that lower expression levels of TFAP2E are significantly associated with a shorter survival. The data indicate that TFAP2E acts as a tumor suppressor of neuroblastoma. Consistent with this notion, TFAP2E-depleted neuroblastoma NB1 and NB9 cells displayed a substantial resistance to DNA damage arising from adriamycin (ADR), cisplatin (CDDP) and ionizing radiation (IR). Silencing of TFAP2E caused a reduced ADR-induced proteolytic cleavage of caspase-3 and PARP. Of note, compared with the untransfected control cells, ADR-mediated stimulation of CDK inhibitor p21(WAF1) was markedly upregulated in TFAP2E-knocked down cells. Therefore, our present findings strongly suggest that TFAP2E has a pivotal role in the regulation of DNA damage response in NB cells through the induction of p21(WAF1).