Levine R A, Forest T, Smith C
Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Vet Pathol. 2002 May;39(3):372-8. doi: 10.1354/vp.39-3-372.
Canine osteosarcoma (OS) cell lines contain mutations that directly or indirectly inactivate the tumor suppressor genes p53 and retinoblastoma. Another important tumor suppressor, PTEN, is mutated in many human cancers. To determine whether inactivation of PTEN plays a role in the pathogenesis of canine OS, we studied its expression in canine OS cell lines and tumors. Four of five canine OS cell lines (CO2, C03, CO5, and CO7) constitutively express high levels of the phosphorylated form of Akt, an indirect indicator of aberrant PTEN expression. PTEN protein is essentially absent from three of these cell lines (CO2, CO5, and CO7), whereas C03 contains a potentially inactivating amino acid substitution in PTEN at codon 340. Genomic hybridization experiments indicate that CO2, CO5, and CO7 contain large deletions within the PTEN gene. Ten of 15 OS tumors exhibit variable or negative PTEN staining. Evaluation of a PTEN-negative staining tumor by Southern blotting indicates that the PTEN gene is deleted in this tumor. These results indicate that PTEN is mutated or downregulated in a high percentage of canine OS cell lines and tumors and likely plays an important role in the pathogenesis of the disease.
犬骨肉瘤（OS）细胞系含有直接或间接使肿瘤抑制基因p53和视网膜母细胞瘤失活的突变。另一个重要的肿瘤抑制基因PTEN在许多人类癌症中发生突变。为了确定PTEN失活是否在犬OS的发病机制中起作用，我们研究了其在犬OS细胞系和肿瘤中的表达。五个犬OS细胞系中的四个（CO2、C03、CO5和CO7）组成性地高水平表达磷酸化形式的Akt，这是PTEN异常表达的间接指标。PTEN蛋白在其中三个细胞系（CO2、CO5和CO7）中基本不存在，而C03在PTEN的第340位密码子处含有一个可能使其失活的氨基酸替换。基因组杂交实验表明，CO2、CO5和CO7在PTEN基因内含有大片段缺失。15个OS肿瘤中有10个表现出PTEN染色可变或阴性。通过Southern印迹法对一个PTEN阴性染色的肿瘤进行评估表明，该肿瘤中的PTEN基因缺失。这些结果表明，PTEN在高比例的犬OS细胞系和肿瘤中发生突变或下调，并且可能在该疾病的发病机制中起重要作用。
