Guo Z, Wu F, Asplund A, Hu X, Mazurenko N, Kisseljov F, Pontén J, Wilander E
Department of Genetics and Pathology, University Hospital, Uppsala University, Sweden.
Mod Pathol. 2001 Feb;14(2):54-61. doi: 10.1038/modpathol.3880256.
Investigation on intratumoral genetic heterogeneity provides an important insight into the roles of genetic alterations in human carcinogenesis and clues to clonal origin of tumors. Intratumoral heterogeneity of genetic changes of cervical cancer has not been described so far. In this study, we analyzed the intratumoral heterogeneity of chromosome 3p deletions and X-chromosome inactivation patterns in multiple microdissected samples from each individual cervical cancer, attempting to understand the roles of 3p deletions in development of cervical cancer and its clonal origin. Totally, 120 normal and lesional samples from 14 cases of fresh cervicalcancers were analyzed. Frequency and patterns of allelic losses of 3p were assessed by polymerase chain reaction (PCR) amplification of 12 microsatellite markers flanking the frequently deleted regions of 3p, followed by Genescan analysis in an ABI 377 DNA sequencer. Loss of heterozygosity was recorded as heterogeneous pattern (LOH present in parts of samples or LOH involving different alleles among different samples) and homogeneous pattern (LOH involving identical alleles in all samples from the tumor). Allelic loss affecting at least one marker was detected in 8 of 14 cases (57%). Allelic losses, both homogeneous and heterogeneous, were frequently detected at FHIT gene region (D3S1300, 40% and 60%; D3S4103, 27.3% and 54.6%), 3p21.3-21.2 (D3S1478, 27.3% and 45.5%), and 3p24.2-22 (D3S1283, 30% and 50%). Seven of eight LOH-positive tumors exhibited homogeneous allelic loss involving at least one of these three 3p loci. Allelic losses were present in the CIN lesions synchronous with invasive lesions positive for LOH. Our findings suggest essential roles of genes on these 3p loci, particularly the FHIT gene in participating in clonal selection and early development of cervical cancer. Most interestingly, with the combination of LOH analysis and X-chromosome inactivation analysis, we provided the first clear genetic evidence of polyclonal origin of cervical invasive cancer in two of eight cases. This finding strongly suggests the importance of field defect (possible human papilloma virus) in cervical carcinogenesis.
肿瘤内基因异质性的研究为深入了解基因改变在人类致癌过程中的作用以及肿瘤的克隆起源提供了重要线索。目前尚未有关于宫颈癌基因改变的肿瘤内异质性的描述。在本研究中，我们分析了来自每例宫颈癌的多个显微切割样本中3号染色体短臂缺失和X染色体失活模式的肿瘤内异质性，试图了解3号染色体短臂缺失在宫颈癌发生发展及其克隆起源中的作用。总共分析了14例新鲜宫颈癌的120个正常和病变样本。通过对位于3号染色体短臂频繁缺失区域两侧的12个微卫星标记进行聚合酶链反应（PCR）扩增，随后在ABI 377 DNA测序仪上进行基因扫描分析，评估3号染色体短臂等位基因缺失的频率和模式。杂合性缺失被记录为异质性模式（部分样本中存在杂合性缺失或不同样本中涉及不同等位基因的杂合性缺失）和同质性模式（肿瘤所有样本中涉及相同等位基因的杂合性缺失）。在14例中的8例（57%）检测到影响至少一个标记的等位基因缺失。在FHIT基因区域（D3S1300，40%和60%；D3S4103，27.3%和54.6%）、3p21.3 - 21.2（D3S1478，27.3%和45.5%）以及3p24.2 - 22（D3S1283，30%和50%）频繁检测到同质性和异质性的等位基因缺失。8例杂合性缺失阳性肿瘤中有7例表现出涉及这三个3号染色体短臂位点中至少一个的同质性等位基因缺失。在与杂合性缺失阳性浸润性病变同步的CIN病变中也存在等位基因缺失。我们的研究结果表明这些3号染色体短臂位点上的基因，特别是FHIT基因在参与宫颈癌的克隆选择和早期发展中起着重要作用。最有趣的是，结合杂合性缺失分析和X染色体失活分析，我们在8例中的2例中首次提供了宫颈癌浸润癌多克隆起源的确切遗传学证据。这一发现强烈提示了“场缺陷”（可能是人乳头瘤病毒）在宫颈癌发生中的重要性。
