Department of Biological Sciences, University of Naples Federico II, Napoli, Italy.
PLoS One. 2010 Feb 23;5(2):e9343. doi: 10.1371/journal.pone.0009343.
Comprehensive analyses have recently been performed on many human cancer tissues, leading to the identification of a number of mutated genes but providing no information on the variety of mutations present in each of them. This information is of interest to understand the possible origin of gene mutations that cause tumors.
METHODOLOGY/PRINCIPAL FINDINGS: We have analyzed the sequence heterogeneity of the transcripts of the human HPRT and G6PD single copy genes that are not considered tumor markers. Analyses have been performed on different colon cancers and on the nearby histologically normal tissues of two male patients. Several copies of each cDNA, which were produced by cloning the RT-PCR-amplified fragments of the specific mRNA, have been sequenced. Similar analyses have been performed on blood samples of two ostensibly healthy males as reference controls. The sequence heterogeneity of the HPRT and G6PD genes was also determined on DNA from tumor tissues. The employed analytical approach revealed the presence of low-frequency mutations not detectable by other procedures. The results show that genetic heterogeneity is detectable in HPRT and G6PD transcripts in both tumors and nearby healthy tissues of the two studied colon tumors. Similar frequencies of mutations are observed in patient genomic DNA, indicating that mutations have a somatic origin. HPRT transcripts show genetic heterogeneity also in healthy individuals, in agreement with previous results on human T-cells, while G6PD transcript heterogeneity is a characteristic of the patient tissues. Interestingly, data on TP53 show little, if any, heterogeneity in the same tissues.
CONCLUSIONS/SIGNIFICANCE: These findings show that genetic heterogeneity is a peculiarity not only of cancer cells but also of the normal tissue where a tumor arises.
最近对许多人类癌症组织进行了全面分析，确定了一些突变基因，但没有提供关于每个基因中存在的突变多样性的信息。了解导致肿瘤的基因突变的可能起源，这种信息是很有意义的。
方法/主要发现：我们分析了人 HPRT 和 G6PD 单拷贝基因的转录本的序列异质性，这些基因不被认为是肿瘤标志物。对两个男性患者的不同结肠癌和附近组织学正常的组织进行了分析。通过克隆特定 mRNA 的 RT-PCR 扩增片段，产生了每个 cDNA 的多个副本，并对其进行了测序。对两个表面健康的男性的血液样本也进行了类似的分析作为参考对照。还在肿瘤组织的 DNA 上测定了 HPRT 和 G6PD 基因的序列异质性。所采用的分析方法揭示了低频突变的存在，这些突变是其他方法无法检测到的。结果表明，在两个研究的结肠癌肿瘤和附近的健康组织中，HPRT 和 G6PD 转录本都存在遗传异质性。在患者的基因组 DNA 中观察到相似的突变频率，表明突变具有体细胞起源。HPRT 转录本在健康个体中也显示遗传异质性，这与之前关于人类 T 细胞的结果一致，而 G6PD 转录本异质性是患者组织的特征。有趣的是，同一组织中 TP53 的数据显示出很少的异质性，如果有的话。
结论/意义：这些发现表明，遗传异质性不仅是癌细胞的特征，也是肿瘤发生的正常组织的特征。
