Molecular Genetic Analysis of Tumor Cells and Developmenet of RNA Interferance Therpy in Neurofibromatosis Type1(NF1)

Neurofibromatosis 1 (NF1) is the most common familial cancer syndrome in humans, with a birth incidence of 1:3500 and a prevalence of 1:4000-.1:5000 in the general population. NF1 is transmitted in an autosomal dominant manner, with about 30-50% of NF1 patients representing de novo germline mutations, implying an extremely high spontaneous mutation rate of the NF1 gene. The two major life-threatening complications of NF1 are hypertension and a significantly higher rate of malignancy, which contribute to a shorter life expectancy than thegeneral population. Malignancies noted at a higher frequency in NF1 patients include malignant neurogenic sarcomas (from malignant transformation of plexiform neurofibromas), astrocytomas, pheochromocytomas, and chronic myeloid leukemias of childhood. NF1 is notable for the existence of a gradual malignant degeneration of normal and/or benign tumor cells. Three pathological phenotypes of fibroblast cells, normal, benign and malignant, are exist within an individual despite they are an identical germ line mutation. The influence of tumor-related genes such as TP53, NK4, and ARF, and the impact of stochastic events have been suggested as causes of this variability. However, there has been no clear evidence to clarify the cell-fate decision factor in NF1. Mutations in the NF1 tumor suppressor underlie the familial tumor predisposition syndrome neurofibromatosis type I. Although its encoded protein, neurofibromin, functions as a Ras-GTPase activating protein, nothing is known about how it is normally regulated or its precise role in controlling Ras signaling pathways. Neurofibromin deficiency typically causes chronic activation of Ras, considered the major contributor to manifestation of NF1. Resistance to radiotherapy and chemotherapy are typical of NF1-associated tumors, but the underlying mechanism is unknown. Members of the Ras superfamily of signaling proteins modulate fundamental cellular processes by cycling between an active GTP-bound conformation and an inactive GDP-bound form. Neurofibromin, the protein product of the NF1 tumor suppressor gene, and p120RasGAP are GTPase-activating proteins for p21 and negatively regulate output by accelerating GTP hydrolysis on Ras. Neurofibromin and p120RasGAP differ markedly outside of their conserved GAP-related domains (GRDs), and it is therefore unknown if the respective GRDs contribute functional specificity. Here, we investigated interrelationships between neurofibromin and p120RasGAP expression, Ras activity, and cell proliferation. Molecular genetic and molecular cell biological studies on the NF1 patient examined this study revealed that no chromosomal aberrations were found in the malignant NF1 primary cells and that a nonsense mutation (Y2264X) in NF1 gene, H-Ras specific activation, and the decreased expression level in the NF1 and Rasa1 genes were responsible for the tumorigenesis and malignant degeneration in this NF1 case. Furthermore, this previously unrecognized Ras and Rasa1 regulatory mechanism may be exploited therapeutically. RNA interference (RNAi) is a newly discovered and popular technology platform among researchers not only in the fields of RNA biology and molecular cell biology. It has created excitement in clinical sciences such as oncology, neurology, endocrinology, infectious diseases and drug discovery. In this study, RNAi for gene silencing of H-Ras has been tried using a episomal plasmid vector, pREP4, and 3 effective RNAi constructs have been identified. A further functional analysis of them may lead to not only a better understanding the mechanisms of tumorigenesis and malignant degeneration of NF1 but also effective application to the therapeutic treatment.

Author dc:creator

• 정, 현정

Contributors dc:contributor

• 김, 현주
• 대학원 의학과
• 200524208

• 신경섬유종증
• 제1형(NF1)
• 유전질환
• neurofibromin
• GAP

Language dc:language

ko

Identifier

http://dcoll.ajou.ac.kr:9080/dcollection/jsp/common/DcLoOrgPer.jsp?sItemId=000000002124
000000002124

OAI identifier oai:identifier

oai:repository.ajou.ac.kr:201003/1654