Cleton-Jansen A M, Callen D F, Seshadri R, Goldup S, Mccallum B, Crawford J, Powell J A, Settasatian C, van Beerendonk H, Moerland E W, Smit V T, Harris W H, Millis R, Morgan N V, Barnes D, Mathew C G, Cornelisse C J
Department of Pathology, Leiden University Medical Center, The Netherlands.
Cancer Res. 2001 Feb 1;61(3):1171-7.
Loss of heterozygosity (LOH) at the long arm of chromosome 16 occurs in at least half of all breast tumors and is considered to target one or more tumor suppressor genes. Despite extensive studies by us and by others, a clear consensus of the boundaries of the smallest region of overlap (SRO) could not be identified. To find more solid evidence for SROs, we tested a large series of 712 breast tumors for LOH at 16q using a dense map of polymorphic markers. Strict criteria for LOH and retention were applied, and results that did not meet these criteria were excluded from the analysis. We compared LOH results obtained from samples with different DNA isolation methods, ie., from microdissected tissue versus total tissue blocks. In the latter group, 16% of the cases were excluded because of noninterpretable LOH results. The selection of polymorphic markers is clearly influencing the LOH pattern because a chromosomal region seems more frequently involved in LOH when many markers from this region are used. The LOH detection method, i.e., radioactive versus fluorescence detection, has no marked effect on the results. Increasing the threshold window for retention of heterozygosity resulted in significantly more cases with complex LOH, i.e., several alternating regions of loss and retention, than seen in tumors with a small window for retention. Tumors with complex LOH do not provide evidence for clear-cut SROs that are repeatedly found in other samples. On disregarding these complex cases, we could identify three different SROs, two at band 16q24.3 and one at 16q22.1. In all three tumor series, we found cases with single LOH regions that designated the distal region at 16q24.3 and the region at 16q22.1. Comparing histological data on these tumors did not result in the identification of a particular subtype with LOH at 16q or a specific region involved in LOH. Only the rare mucinous tumors had no 16q LOH at all. Furthermore, a positive estrogen content is prevalent in tumors with 16q LOH, but not in tumors with LOH at 16q24.3 only.
16号染色体长臂杂合性缺失（LOH）出现在至少一半的乳腺肿瘤中，被认为靶向一个或多个肿瘤抑制基因。尽管我们和其他人进行了广泛研究，但仍无法明确确定最小重叠区域（SRO）的边界。为了找到更多关于SRO的确凿证据，我们使用多态性标记的密集图谱对712例乳腺肿瘤进行了16q LOH检测。对LOH和保留情况应用了严格标准，不符合这些标准的结果被排除在分析之外。我们比较了从不同DNA分离方法获得的样本的LOH结果，即从显微切割组织与整个组织块中获得的样本。在后一组中，16%的病例因无法解释的LOH结果而被排除。多态性标记的选择明显影响LOH模式，因为当使用来自该区域的许多标记时，一个染色体区域似乎更频繁地出现LOH。LOH检测方法，即放射性检测与荧光检测，对结果没有显著影响。增加杂合性保留的阈值窗口导致具有复杂LOH（即几个交替的缺失和保留区域）的病例显著多于保留窗口小的肿瘤。具有复杂LOH的肿瘤并未为在其他样本中反复发现的明确SRO提供证据。不考虑这些复杂病例，我们可以识别出三个不同的SRO，两个在16q24.3带，一个在16q22.1。在所有三个肿瘤系列中，我们发现了具有单个LOH区域的病例，这些区域确定了16q24.3的远端区域和位于16q22.1的区域。比较这些肿瘤的组织学数据并未导致识别出具有16q LOH的特定亚型或涉及LOH的特定区域。只有罕见的黏液性肿瘤根本没有16q LOH。此外，雌激素含量阳性在具有16q LOH的肿瘤中普遍存在，但仅在16q24.3发生LOH的肿瘤中不存在。
