García-Castellano José M, Villanueva Alberto, Healey John H, Sowers Rebecca, Cordon-Cardo Carlos, Huvos Andrew, Bertino Joseph R, Meyers Paul, Gorlick Richard
Orthopaedic Surgery Service, affiliated with Weil Medical College of Cornell University, New York, NY 10021, USA.
Clin Cancer Res. 2002 Mar;8(3):782-7.
Methylthioadenosine phosphorylase (MTAP) is an enzyme essential in the salvage of cellular adenine and methionine synthesis. The MTAP gene is located in the 9p21 chromosomal region and its loss is frequently associated with deletion of the tumor suppressor genes p15(INK4b) and p16(INK4a). The aim of this study was to investigate the frequency of molecular alterations in MTAP in osteosarcoma.
Samples from patients with high-grade osteosarcoma (n = 96) and three osteosarcoma cell lines (HOS, SaOS-2, and U2OS) were analyzed. Genomic DNA was analyzed for MTAP gene deletions by PCR, RNA expression was measured by semiquantitative reverse transcription-PCR, and the protein levels were measured by immunohistochemistry.
Deletion of at least one MTAP exon was found in 36 of 96 (37.5%) osteosarcoma patient samples and in one of the three cell lines (HOS). In all cases in which an MTAP gene deletion was observed, there was absence of detectable mRNA and protein. Furthermore, in four osteosarcoma patients, an MTAP deletion which was not evident at diagnosis was detected in subsequent tumor samples.
The MTAP gene is commonly deleted in osteosarcoma patient samples, leading to an absence of mRNA and protein expression; these results indicate that inhibitors of de novo purine synthesis or methionine depletion may be effective as treatments for osteosarcoma patients whose tumors fail to express MTAP.
甲硫腺苷磷酸化酶（MTAP）是细胞腺嘌呤挽救和蛋氨酸合成中必不可少的一种酶。MTAP基因位于9p21染色体区域，其缺失常与肿瘤抑制基因p15（INK4b）和p16（INK4a）的缺失相关。本研究的目的是调查骨肉瘤中MTAP分子改变的频率。
分析了来自高级别骨肉瘤患者（n = 96）的样本以及三种骨肉瘤细胞系（HOS、SaOS-2和U2OS）。通过PCR分析基因组DNA中的MTAP基因缺失，通过半定量逆转录PCR测量RNA表达，并通过免疫组织化学测量蛋白质水平。
在96例骨肉瘤患者样本中的36例（37.5%）以及三种细胞系之一（HOS）中发现至少一个MTAP外显子缺失。在所有观察到MTAP基因缺失的病例中，均未检测到mRNA和蛋白质。此外，在四名骨肉瘤患者中，后续肿瘤样本中检测到诊断时不明显的MTAP缺失。
MTAP基因在骨肉瘤患者样本中普遍缺失，导致mRNA和蛋白质表达缺失；这些结果表明，对于肿瘤不表达MTAP的骨肉瘤患者，从头嘌呤合成抑制剂或蛋氨酸消耗可能作为有效的治疗方法。
