Characterization of transcriptional mechanism and transcriptional network of oncogenic zinc finger protein ZNF322A

• Main Authors: JayuJen, 任婕羽
• Other Authors: Yi-Ching Wang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/39492294685825198519

博士 === 國立成功大學 === 基礎醫學研究所 === 104 === Background: Lung cancer is the leading cause of cancer death both in female and in male worldwide. Overall survival of lung cancer patients is still poor, although lots of efforts have done trying to cure lung cancer. Therefore, elucidation of the cellular mechanisms in lung tumorigenesis is important to develop early diagnostic and new effective therapeutic targets. In our previous studies, we examined 18 human genomic imbalance hotspots in 40 Asian and 20 Caucasian lung cancer patients using array comparative genomic hybridization. A putative oncogene ZNF322A, which located at chromosome 6p22.1, was found significantly amplified in both Asian and Caucasian lung cancer patients. However, the oncogenic role of ZNF322A overexpression and its underlying mechanism in lung tumorigenesis remain elusive. Results: Here, we show high frequency of ZNF322A protein overexpression in Asian (79%, 97/123) and Caucasian (73%, 54/74) lung cancer patients. Multivariate Cox regression analysis indicated that ZNF322A was an independent risk factor for lung cancer poor outcome, corroborating the Kaplan-Meier results that patients with ZNF322A protein overexpression had significantly poorer overall survival than other patients. Overexpression of ZNF322A promoted cell proliferation and soft agar growth by prolonged cell cycle in S phase in multiple lung cell lines, including the immortalized lung cell BEAS-2B. In addition, ZNF322A overexpression enhanced cell migration and invasion. In contrast, knockdown of ZNF322A diminished cell growth, invasion and metastasis abilities in vitro and in vivo. To characterize the transcriptional mechanism of ZNF322A in lung cancer, we first revealed consensus DNA binding motifs of ZNF322A using CASTing (Cyclic amplification and selection of targets) assay and chromatin-immunoprecipitation-sequencing (ChIP-seq) analysis. We then identified putative transcriptional targets of ZNF322A by integrating ChIP-seq, RNA-seq and proteomic datasets. Many of the ZNF322A transcriptional target genes were involved in cancer-related processes, such as transcription, cell cycle regulation and migration. Mechanistically, we found that ZNF322A formed complex with c-Jun and cooperatively activated alpha-adducin and cyclin D1 but repressed p53 gene transcription by recruiting differential chromatin modifiers, such as histone deacetylase 3, in an AP-1 element dependent manner using luciferase promoter activity assay combined with site-directed mutagenesis and sequential ChIP-PCR assay. Conclusion: Our results provide compelling evidences that overexpression of ZNF322A transcriptionally dysregulates genes in cell growth and motility therefore contributes to lung tumorigenesis and poor prognosis. The unbiased genomic analyses reveal de novo ZNF322A motifs and downstream target genes in lung cancer. Gene ontology analyses of genomic datasets unravel the previously unidentified role of ZNF322A in lung cancer stem cell. Further study will be pursued to elucidate ZNF322A transcriptional mechanism and characterize ZNF322A transcriptional network in lung cancer or lung cancer stem cells.