骨肉瘤中cbfa1基因表达与临床因素的相关性研究

Variable expression of the cbfa1 transcription factor gene in osteosarcoma

目的 cbfa1 基因是一种结合在Osteocalcin 启动子上并能调节其在成骨细胞中表达的转录因子, 在成骨细胞的分化和成熟中起着重要的作用。由于cbfa1 基因在成骨细胞分化过程中所起的重要作用, 研究骨肉瘤中cbfa1 的表达有重要的意义。方法 应用Southern blot 法和RT- PCR 技术对43 例骨肉瘤标本和3 株骨肉瘤细胞系(SaOS- 2 、HOS 和U - 2) 中cbfa1 基因的结构和表达进行了研究。结果 在43 例骨肉瘤标本中未发现cbfa1 基因重排、缺失或扩增的现象。43 例骨肉瘤标本中27 例(63 % ) 及3 株骨肉瘤细胞检出cbfa1 的m RNA。但cbfa1 的表达水平,在大多数的骨肉瘤细胞中低于正常淋巴细胞的表达。Osteocalcin (cbfa1 的靶基因) 的表达, 在大多数骨肉瘤标本中与cbfa1 基因的表达是平行的。cbfa1 转录水平和患者生存率之间在统计学上有明显的相关性。结论 肿瘤中有cbfa1 基因表达的患者比缺乏这种基因表达的患者有更长的生存期。cbfa1

Objective Cbfa1, encoding a transcription factor which binds the promoter of the osteocalcin gene and regulating its expression in osteoblasts, has been found to play a central role in the differentiation and maturation of osteoblasts Cbf1 gene belongs to a family of transcription factors involved in oncogenic transformation, and rearrangements of other members It has been associated with specific types of leukemia Because of the significant role of the cbfa1 gene in osteoblast differentiation, study of cbfa1 gene status could be of considerable interest in osteosarcoma Methods A total of 43 specimens of OS encountered from 1990 to 1995 were collected at Memorial Sloan-Kettering Cancer Center from 25 biopies, 12 en bloc resections and 6 metastasectomy operations The patients included 28 males and 15 females, and the mean age was 25 years The primary tumor was studied in 35 cases, and metastatic tumors in 6 local recurrence in 2 The structure and expression of the cbfa1 gene were studied in 43 osteosarcoma samples and three osteosarcoma cell lines (SaOS-2, HOS and U-2) by quantitative Southern blot and RT-PCR techniques Results We found no evidence of cbfa1 gene rearrangement, deletion or amplification in 43 osteosarcoma samples Cbfa1 mRNA was detected in 27 of 43 (63%) osteosarcoma samples and all three osteosarcoma cell lines Cbfa1 transcript levels were variable, and in the majority of osteosarcomas were lower than in normal lymphocytes which are reported to express 20-fold less cbfa1 mRNA than normal osteoblasts Expression of osteocalcin, a target gene of cbfa1, parallels with that of cbfa1 in most osteosarcoma samples A statistical correlation between the cbfa1 transcript and disease free survival was observed Conclusion The patients with cbfa1 expression in tumors had a longer survival period than those patients lacking expression of the gene in tumors Cbfa1 expression may be a marker for the level of osteoblast differentiation in osteosarcoma