Mutational Inactivation of the Nijmegen Breakage Syndrome Gene (NBS1) in Glioblastomas Is Associated With Multiple TP53 Mutations

Abstract

Nijmegen breakage syndrome caused by NBS1 germline mutations is a rare autosomal recessive disease with clinical features that include microcephaly, increased radiosensitivity, and predisposition to cancer. NBS1 plays a key role in DNA double-strand break repair and the maintenance of genomic stability. We screened 87 glioblastomas for NBS1 mutations (all 16 exons). Single-strand conformation polymorphism followed by direct DNA sequencing revealed 12 NBS1 mutations (8 missense and 4 intronic mutations) in 9 (32%) of 28 primary (de novo) glioblastomas carrying 2 or more TP53 mutations. None of the NBS1 mutations has been previously reported as a germline mutation in Nijmegen breakage syndrome patients. NBS1 mutations were not detected in 19 primary glioblastomas with 1 TP53 mutation or in 21 primary glioblastomas without TP53 mutations. Secondary glioblastomas that developed through progression from low-grade or anaplastic astrocytoma had TP53 mutations in 16 (84%) of 19 cases, but none contained mutations of the NBS1 gene. These results suggest that multiple TP53 mutations in glioblastomas are due to deficient repair of DNA double-strand breaks caused by mutational inactivation of the NBS1 gene.

Mutation Inactivation of Nijmegen Breakage Syndrome Gene (NBS1) in Hepatocellular Carcinoma and Intrahepatic Cholangiocarcinoma

“…The main functional domains of Nbs1 comprise the forkhead-associated (FHA) domain (amino acids 24–100), the breast cancer C-terminal (BRCT) domain (amino acids 105–190), the second BRCT domain (amino acids 215–324), and the Mre11-binding domain (amino acids 601–700, binding sites 665–693), as well as ATM phosphorylation sites [13,14]. Both the FHA and BRCT domains are essential for responses to DNA damage, including the formation of ionizing radiation-induced foci, S-phase checkpoint activation and nuclear focus formation after irradiation, and play crucial roles in cell survival after radiotherapy [26].…”

“…Extraction of genomic DNA from paraffin sections and PCR-SSCP analysis for NBS1 were conducted as described previously [13,14,19]. Mutations identified in paraffin sections were verified by sequencing a second product of amplification on both strands and were further validated using paired frozen tissue.…”

“…In addition to lymphoma and leukemia in NBS patients, NBS1 mutations have been found in sporadic cancers, including breast cancer [11], colorectal cancer [12], medulloblastoma [13], primary glioblastomas [14], lymphoid malignancies and acute lymphoblastic leukemia [15]. Moreover, there may be functional interactions between Nbs1 and p53 [16,17], and mutational inactivation of the NBS1 gene in tumors is associated with TP53 mutations [13,14], suggesting a synergistic effect of Nbs1 with p53 in the development of cancer.…”

Nijmegen Breakage Syndrome Protein (NBN) Causes Resistance to Methylating Anticancer Drugs Such as Temozolomide

“…It is noteworthy that an increased frequency of NBN mutations was recently demonstrated in GBM (Watanabe et al, 2009). On the basis of our data, it is pertinent to conclude that NBN mutations in GBM have an impact on the therapeutic response of the patients.…”

“…NBN is frequently mutated in glioblastoma multiforme (WHO grade IV) (Watanabe et al, 2009) and medulloblastomas (Huang et al, 2008). It is overexpressed in uveal melanomas, correlating with metastatic death, and was therefore suggested as a prognostic marker for melanomas (Ehlers and Harbour, 2005).…”