COP1, an E3 ubiquitin ligase, induces cell cycle arrest and apoptosis in a p53-dependent manner in human breast cancer
- 주제(키워드) Breast cancer , ubiquitination , COP1 , p53 , RNA silencing , gene therapy
- 발행기관 아주대학교
- 지도교수 윤태종
- 발행년도 2020
- 학위수여년월 2020. 8
- 학위명 박사
- 학과 및 전공 일반대학원 응용생명공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000030085
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Background and aims: Understanding how the expression of tumor suppressor genes is regulated can provide powerful insights into their therapeutic applications. One crucial regulatory mechanism for p53, a well-known tumor suppressor gene, is through ubiquitin ligases. However, the mechanistic role of constitutive photomorphogenic 1 (COP1), an E3 ubiquitin ligase, remains unclear in human breast cancer (BC). The aim of the present study was to investigate and elucidate the tumor-suppressor role of COP1 in BC. Methods: I performed RNA interference and expression analysis to investigate COP1-mediated regulation of p53 in three BC cell lines (MCF7, ZR-75-R, and MDA-MB-157) and a non-cancerous cell line. Apoptosis and cell cycle arrest were analyzed by flow cytometry. I also assayed caspase-3/7 activity and assessed changes in mitochondrial membrane potential. Results were validated using a subcutaneous BC xenograft model. Results: COP1 expression was three to four times lower in the non-cancerous cell line than the BC cell lines, while p53 was significantly overexpressed in the non-cancerous cells. Further, COP1 expression levels varied across the cell lines. COP1 silencing inhibited BC cell viability, and the effects of COP1 silencing were dependent on p53 status. Western blot analyses revealed that COP1 regulated p53 protein levels, thereby altering the expression of p53 target genes. Moreover, COP1 silencing induced cell cycle arrest in human BC cells expressing wild-type p53. COP1 knockdown was associated with an increase in the percentage of MCF7 and ZR-75-1 cells arrested in the G0/G1 phase, while there was no effect on cell cycle progression in MDA-MB-157 cells. Additionally, COP1 silencing promoted p53 accumulation, leading to cell cycle arrest, mitochondrial membrane depolarization, caspase activation, and p53-dependent cell death. Thus, our results demonstrated that COP1 induces apoptosis in a p53-dependent manner in BC. Conclusion: The results of this study suggest that COP1 could be a novel candidate therapeutic target for BC. Further, COP1 inhibition represents a promising approach to modulate p53 activity.
more목차
I. Introduction 1
II. Materials and Methods 5
A. Cell lines and reagents 5
B. Lentiviral packaging and transduction 6
C. Western blot analysis 8
D. RNA extraction 9
E. Quantitative real-time PCR (qRT-PCR) 9
F. Cell viability and cytotoxicity assays 11
G. Flowcytometric analysis of apoptosis 11
H. Caspase 3/7 assay 12
I. MitoLight apoptosis-detection kit 12
J. Subcutaneous breast cancer xenograft model 13
K. Quantification and statistical analysis 13
III. Results 14
A. Characterization of the mammalian COP1 protein 14
B. Comparison of COP1 knockdown using five different shRNAs 17
C. Expression of p53 and COP1 in BC cell lines 19
D. COP1 silencing inhibits BC cell viability in a p53-dependent manner 23
E. COP1 silencing activates p53 transcription to regulate sub-proteins 25
F. p53 activation by COP1 inhibition induces cell cycle arrest 25
G. COP1 induces apoptosis in a p53-dependent manner 28
H. Effect of shCOP1 expression in an MCF cell-derived xenograft tumor model 32
IV. Discussion 36
V. References 39
초록 (국문요약) 45
