Giaretti W, Monaco R, Pujic N, Rapallo A, Nigro S, Geido E
Laboratory of Biophysics and Cytometry, National Institute for Cancer Research (IST), Genoa, Italy.
Am J Pathol. 1996 Jul;149(1):237-45.
Detailed information about intratumor K-ras2 mutations in colorectal adenocarcinomas and a possible association with DNA content heterogeneity is still lacking. DNA diploid and aneuploid subclones, detected among multiple histologically selected primary sectors (57 superficial and 40 deep) and 9 lymph node metastases, were flow cytometrically sorted and separately submitted to codons 12-13 K-ras2 mutation spectrum analysis. DNA aneuploidy was absent among 20 near and 20 distant mucosa sites and present in 7/9 lymph node metastases and in 17/19 primary tumors (90%). Primary intratumor DNA multiclonality was approximately 50%. Degree of DNA aneuploidy (DNA Index) distribution was nonrandom and showed peaks at approximate mean DNA Index values 1.2, 1.5, and 1.8. K-ras2 mutations were detected in 0/20 mucosa cases, in 2/9 lymph node metastases, and in 9/19 adenocarcinomas (47%). No more than one mutation type per tumor was detected. Intratumor distribution of K-ras2 mutations was homogeneous in 6 and heterogeneous in 3 cases. Homogeneous distribution was associated with DNA near-diploid aneuploidy. K-ras2 mutations were strongly associated with DNA Index in the near-diploid region (83%) and almost absent (5%) among DNA near-triploid subclones (P = 0.0001). K-ras2 mutation intratumor heterogeneity indicates that sampling of the tumor may be a critical step and suggests that K-ras2 activation may be a late event in a subgroup of tumors. Our data also suggest the existence of an early process of the colorectal carcinogenesis that favors both K-ras2 mutations and DNA near-diploid aneuploidy. Onset of DNA near-triploid subclones appears, instead, to be independent from K-ras2 activation.
关于结直肠癌肿瘤内K-ras2突变的详细信息以及与DNA含量异质性的可能关联仍然缺乏。在多个经组织学选择的原发部位（57个浅表部位和40个深部部位）以及9个淋巴结转移灶中检测到的DNA二倍体和非整倍体亚克隆，通过流式细胞术进行分选，并分别进行密码子12 - 13的K-ras2突变谱分析。在20个近端和20个远端黏膜部位未发现DNA非整倍体，而在7/9个淋巴结转移灶和17/19个原发性肿瘤（90%）中存在。原发性肿瘤内DNA多克隆性约为50%。DNA非整倍体程度（DNA指数）分布并非随机，在大约平均DNA指数值1.2、1.5和1.8处出现峰值。在0/20个黏膜病例、2/9个淋巴结转移灶和9/19个腺癌（47%）中检测到K-ras2突变。每个肿瘤检测到的突变类型不超过一种。K-ras2突变在肿瘤内的分布在6例中是均匀的，在3例中是异质的。均匀分布与DNA近二倍体非整倍体相关。K-ras2突变在近二倍体区域与DNA指数密切相关（83%），而在DNA近三倍体亚克隆中几乎不存在（5%）（P = 0.0001）。K-ras2突变的肿瘤内异质性表明肿瘤取样可能是关键步骤，并提示K-ras2激活可能是一部分肿瘤中的晚期事件。我们的数据还表明结直肠癌发生过程中存在一个早期过程，该过程有利于K-ras2突变和DNA近二倍体非整倍体。相反，DNA近三倍体亚克隆的出现似乎独立于K-ras2激活。
