Zhang H, Chen Z H, Savarese T M
Cancer Center, University of Massachusetts Medical Center, Worcester 01655, USA.
Cancer Genet Cytogenet. 1996 Jan;86(1):22-8. doi: 10.1016/0165-4608(95)00157-3.
In this study, 27 malignant cell lines, including leukemias, gliomas, and lung and bladder carcinomas were screened for homozygous deletions of the putative tumor suppressor gene p16 (MTS1/CDK4I/CDKN2) and other markers within the chromosome 9p21 region; these include the genes for interferon-alpha1 (IFNA1), interferon-beta1 (IFNB1), methylthioadenosine phosphorylase (MTAP), and two microsatellite markers, D9S171 and D9S169. The purpose of this study was to determine the incidence of codeletion of these markers. Screening for homozygous deletions was carried out using direct polymerase chain reaction of genomic DNA, or, in the case of MTAP, a functional enzyme assay. Of these cell lines, 14 (52%) were found to have homozygous deletions of the p16 gene. Two of the 14 p16-negative cell lines (14%) were found to have homozygous deletions within the p16 domain but but no other 9p21 marker. MTAP was codeleted in 12 of the 14 p16-negative cell lines (86%), whereas IFNA1 was codeleted with p16 in eight of these lines (57%); IFNB1 was codeleted in five (36%) of the p16-deleted cell lines. The D9S171 marker, which may lie greater than 3 cM centromeric to p16, is codeleted in three cell lines (21%); the D9S169 marker, which maps even further toward the centromere, was codeleted in only one cell line (7%). Loss of any 9p21 marker, e.g., MTAP or IFNA1, were invariable predictors of the loss of the p16 gene. In addition, loss of IFNA1 always predicted a loss of MTAP (eight of eight cell lines), although loss of MTAP did not always predict a loss of IFNA1 (four of 12 MTAP-deleted cell lines did not have homozygous deletions of IFNA1). Thus loss of nearby genes occurs in a high percentage of cell lines that bear homozygous deletions of the p16 locus. Codeletion of MTAP or IFN in p16-negative malignant cells is of interest, as loss of these genes may influence the biologic behavior of these cells and render them susceptible to certain therapeutic approaches.
在本研究中，对27种恶性细胞系进行了筛查，包括白血病、神经胶质瘤以及肺癌和膀胱癌细胞系，以检测假定的肿瘤抑制基因p16（MTS1/CDK4I/CDKN2）以及9号染色体p21区域内的其他标志物的纯合缺失情况；这些标志物包括α1干扰素（IFNA1）、β1干扰素（IFNB1）、甲硫腺苷磷酸化酶（MTAP）的基因，以及两个微卫星标志物D9S171和D9S169。本研究的目的是确定这些标志物共缺失的发生率。使用基因组DNA的直接聚合酶链反应进行纯合缺失的筛查，对于MTAP，则采用功能性酶分析。在这些细胞系中，发现14种（52%）存在p16基因的纯合缺失。在14种p16阴性细胞系中有2种（14%）在p16区域内存在纯合缺失，但无其他9p21标志物的缺失。在14种p16阴性细胞系中有12种（86%）MTAP与p16共缺失，而在其中8种细胞系（57%）中IFNA1与p16共缺失；在5种（36%）p16缺失的细胞系中IFNB1与p16共缺失。可能位于距p16着丝粒大于3厘摩处的D9S171标志物，在3种细胞系（21%）中与p16共缺失；定位更靠近着丝粒的D9S169标志物，仅在1种细胞系（7%）中与p16共缺失。任何9p21标志物的缺失，如MTAP或IFNA1，都是p16基因缺失的可靠预测指标。此外，IFNA1的缺失总是预示着MTAP的缺失（8个细胞系中的8个），尽管MTAP的缺失并不总是预示着IFNA1的缺失（12个MTAP缺失的细胞系中有4个没有IFNA1的纯合缺失）。因此，在大量携带p16基因座纯合缺失的细胞系中会出现附近基因的共缺失。p16阴性恶性细胞中MTAP或IFN的共缺失值得关注，因为这些基因的缺失可能影响这些细胞的生物学行为，并使其对某些治疗方法敏感。
