Khatib Z A, Matsushime H, Valentine M, Shapiro D N, Sherr C J, Look A T
Department of Experimental Oncology and Hematology/Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.
Cancer Res. 1993 Nov 15;53(22):5535-41.
The 34-kilodalton cyclin-dependent kinase, p34cdk4, is a major catalytic subunit of mammalian D-type cyclins, which act during the G1 phase of the cell cycle to enforce the decision of cells to enter S phase. A murine complementary DNA clone was used to clone the cognate human CDK4 gene, which was localized to human chromosome 12, band q13, by fluorescence in situ hybridization. Because this chromosomal band contains the GLI and MDM2 genes, which are frequently amplified in human sarcomas, we analyzed CDK4 copy number and expression in a panel of sarcoma cell lines. An osteosarcoma cell line, OsACL, manifested a 25-fold increased copy number of CDK4, amplified concordantly with both GLI and MDM2, whereas a rhabdomyosarcoma cell line, SJRH30, was found to have an amplicon that included CDK4 and GLI but not MDM2. CDK4 mRNA and protein were overexpressed in both cell lines, and nucleotide sequencing analysis indicated that the gene had not sustained mutations. These observations provide the first evidence for amplification of a gene encoding a cell division cycle protein kinase, complement recent data indicating that genes encoding D-type cyclins are targets of chromosomal rearrangement and gene amplification in tumor cells, and suggest that CDK4 amplification might contribute to oncogenesis.
34千道尔顿的细胞周期蛋白依赖性激酶p34cdk4是哺乳动物D型细胞周期蛋白的主要催化亚基，在细胞周期的G1期发挥作用，促使细胞决定进入S期。利用小鼠互补DNA克隆来克隆同源的人类CDK4基因，通过荧光原位杂交将其定位到人类12号染色体q13带。由于该染色体带包含GLI和MDM2基因，这些基因在人类肉瘤中经常扩增，我们分析了一组肉瘤细胞系中CDK4的拷贝数和表达情况。骨肉瘤细胞系OsACL显示CDK4拷贝数增加了25倍，与GLI和MDM2一致扩增，而横纹肌肉瘤细胞系SJRH30被发现有一个包含CDK4和GLI但不包含MDM2的扩增子。CDK4 mRNA和蛋白在这两种细胞系中均过度表达，核苷酸测序分析表明该基因未发生突变。这些观察结果为编码细胞分裂周期蛋白激酶的基因扩增提供了首个证据，补充了最近的数据，即编码D型细胞周期蛋白的基因是肿瘤细胞中染色体重排和基因扩增的靶点，并表明CDK4扩增可能有助于肿瘤发生。
