신경섬유종증 제1형의 악성전개에 관여하는TNS3 유전자의 역할 규명

Alternative Title
Roles of TNS3 gene in tumor progression of Neurofibromatosis Type 1
Author(s)
안수용
Alternative Author(s)
Su Yong An
Advisor
정선용
Department
일반대학원 의생명과학과
Publisher
The Graduate School, Ajou University
Publication Year
2018-02
Language
kor
Keyword
신경섬유종증 제1형상염색체 우성질환NF1 유전자돌연변이악성 전개악성말초신경초종양TNS3xenograftsiRNA항암제
Abstract
신경섬유종증 제1형(Neurofibromatosis Type 1; NF1)은 신경섬유종, 밀크 커피색 반점 등을 포함하여 다양한 임상증상이 나타나는 질환으로 상염색체 우성 유전 질환으로 약 3,500명중 1명꼴로 발생한다. 특히, 30~40%의 환자에서 말초신경을 따라 양성종양인 피부신경섬유종과 총상신경섬유종이 발생되고, 환자의 약 10%에서는 악성말초신경초종양(malignant peripheral nerve sheath tumor; MPNST)이 발생되며, 이러한 악성의 MPNST 는 화학요법과 방사능에 낮은 반응을 보이며 환자의 높은 사망률로 이어진다. 본 연구에서는 신경섬유종증 제1형의 정상세포 또는 양성종양세포의 악성화 전개(tumor progression)에 관여하는 핵심유전자(key gene)를 발굴하여, 악성화 관여 기전 규명과 치료 타겟 분자(Therapeutic target molecule)로서의 가능성 검증에 대해 연구하고자 하였다. 3명의 신경섬유종증 제1형 환자의 수술조직으로부터 분리한 정상조직, 양성종양조직, 악성종양조직을 재료로, DNA methylation array와 차세대염기서열장치(NGS) 기반의 whole-genome RNA-sequencing을 실시하여 3명의 환자 악성종양조직에서 공통으로 발현량이 현저하게 증가되어 있는 TNS3 유전자를 발굴하였다. 또한, 악성말초신경초종양 세포주인 sF02.2, sNF96.2, S462의 3종의 세포에서 모두 TNS3 mRNA의 발현량이 크게 증가되어 있었다. 악성말초신경초종양 S462 세포에서 short hairpin RNA(shRNA)를 사용하여 TNS3 유전자의 발현을 억제하였 때, 신경섬유종증 제1형의 악성화에 중요한 역할을 하는 Ras, ERK1/2의 활성화가 억제되었다. 따라서, TNS3 shRNA가 악성말초신경초종양세포의 apoptosis에 미치는 영향에 대해 분석하였다. TNS3 shRNA를 단독처리에서는 악성말초신경초종양 세포의 apoptosis에 큰 영향이 없었으나, 기존에 악성말초신경초종양과 육종(sarcoma) 등의 악성종양에 주로 사용하는 ICE(Ifosfamide, Carboplatin, Etoposide)와 CVM(Cisplatin, Vinblastine, Methotrexate) 항암제와 병용으로 처리하였을 시에는 cell viability 억제와 apoptosis 증가에 뚜렷한 시너지 효과가 나타났다. TNS3 short interfering RNA(siRNA)의 in vivo 유효성 평가를 위해 누드마우스에 S462 세포를 주입하여 신경섬유종증 제1형 악성종양 xenograft 마우스를 제작하였다. 신경섬유종증 제1형 악성종양 xenograft 마우스에 TNS3 siRNA, ICE, CVM 단독 또는 병용 주입시에 3가지 모두에서 종양 부피, 종양 무게, 종양 크기 등이 대조군에 비해 유의하게 적은 항암효과가 나타났으며, TNS3 siRNA+ICE와 TNS3 siRNA+CVM의 병용투여 시에 더 확실한 항암효과가 관찰되었다. 본 연구결과는 신경섬유종증 제1형의 악성화 기전의 규명에 중요한 자료를 제공할 뿐만 아니라, 향후의 TNS3 siRNA와 항암제의 병용 투여를 통한 신경섬유종증 제1형의 치료법 개발에 크게 활용될 수 있을 것으로 기대된다.
Alternative Abstract
Neurofibromatosis type 1 (NF1) is one of the most common inherited autosomal dominant disorders. It is caused by a mutation in the NF1 gene, which encodes neurofibromin, a tumor suppressor with Ras-GAP activity that negatively regulates p21-RAS signaling. More than 95% of NF1 patients have benign dermal neurofibromas, while 30–40% of NF1 patients have benign plexiform neurofibromas (PNs) which can undergo malignant transformation to malignant peripheral nerve sheet tumors (MPNSTs). The malignant tumor progression of PNs to MPNSTs has been observed in approximately 10% of patients with NF1, representing a major cause of mortality in these patients. This study aimed to identify novel genes that are closely involved in tumor progression in NF1, elucidate their roles in tumor progression, and evaluate their potential as the molecular targets for NF1 malignant tumors’ therapeutic treatment. I screened differentially expressed genes between normal or benign and malignant tissues from patients with NF1 using whole-genome methylation array and next-generation sequencer–based whole RNA sequencing. Several candidate genes were identified, and by reviewing these genes, I selected TNS3 for further studies. This was because the expression alterations of the TNS3 gene have been reported in relation to several tumors, but not NF1 tumors, as well as because the hyperexpression of TNS3 was found in malignant tumors from all three NF1 patients tested. I found that the mRNA of TNS3 was highly expressed in MPNST cell lines, namely sNF02.2, sNF96.2, and S462; its gene product, Tensin 3, was also upregulated in S462 cells. However, when TNS3 expression was silenced by knockdown with shRNAs, the GTP-Ras and phosphorylated ERK1/2 levels were significantly reduced. Co-treatment of TNS3 shRNA and ifosfamide, carboplatin, and etoposide (ICE) or cisplatin, vinblastine, and methotrexate (CVM) anticancer drugs significantly increased the caspase-3 cleavage and apoptotic cell death, but it decreased Ras and ERK1/2 activation, indicating that TNS3 shRNA synergistically enhances the apoptosis of S462 MPNST cells. To evaluate the effects of TNS3 shRNA in vivo, I established a xenograft NF1-associated MPNST mouse model by injecting the S462 cells into nude mice. Single and combination treatments of TNS3 siRNA and ICE or CVM anticancer drugs in the MPNST xenograft mice resulted in dramatic decreases in tumor volume, weight, and size, and TNS3 siRNA administration showed synergistic antitumor effects compared with single ICE and CVM treatments. No other phenotypic defects were observed in the mouse groups administered TNS3 siRNA. Collectively, I found a new candidate TNS3 gene that may play a key role in the malignant tumor progression of NF1. Knockdown of the TNS3 gene led to a significant reduction of Ras and ERK1/2 activation, thereby enhancing MPNST cell apoptosis. Combination treatment of TNS3 siRNA with ICE or CVM in an NF1-associated MPNST xenograft mouse model revealed synergistic, strong antitumor effects. This study may affect the understanding of the mechanisms of malignant transformation and lead to an effective application in the therapeutic treatment for NF1.
URI
https://dspace.ajou.ac.kr/handle/2018.oak/19187
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