Yang Lin, Hamilton Stanley R, Sood Anil, Kuwai Toshio, Ellis Lee, Sanguino Angela, Lopez-Berestein Gabriel, Boyd Douglas D
Department of Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Cancer Res. 2008 Jun 1;68(11):4321-30. doi: 10.1158/0008-5472.CAN-08-0407.
A relatively new view of colorectal cancer is that its development/progression reflects the contribution of a large set of altered gene products in varying combinations, each providing a "fitness advantage." In searching for novel contributing gene products using Unigene cluster data mining, we found overrepresentation of expressed sequence tags corresponding to a previously uncharacterized gene (ZKSCAN3) in colorectal tumors. ZKSCAN3 was pursued for several reasons: (a) its sequence similarity with bowl required for Drosophila hindgut development; (b) it lies in a chromosomal region (6p22.1) amplified in colorectal cancer; and (c) its coding sequence predicts tandem C(2)H(2) zinc finger domains present in a class of proteins gaining attention for their role in oncogenesis/tumor progression. Reverse transcription-PCR confirmed overexpression in colorectal tumor tissue compared with adjacent nonmalignant mucosa due in part to gene amplification determined by Southern blotting. Further, immunohistochemistry with an antibody generated to the predicted protein sequence revealed higher ZKSCAN3 expression in invasive compared with noninvasive tumors. Intriguingly, the ZKSCAN3 protein was also expressed in tumors wild-type for genes (APC, p53, K-Ras) commonly targeted in colorectal cancer. ZKSCAN3 knockdown in two independent colon cancer cell lines impaired anchorage-independent growth and orthotopic tumor growth, whereas overexpression in a third cell line had the opposite effect and increased 5-fluorouracil resistance. Liposomal delivery of a ZKSCAN3-targeting small interfering RNA reduced tumorigenicity of orthotopic colon cancer. Thus, the hitherto uncharacterized ZKSCAN3 adds to an expanding set of encoded products contributing to the progression of colorectal cancer.
对结直肠癌的一种相对较新的观点认为，其发生/发展反映了大量改变的基因产物以不同组合方式所起的作用，每种组合都提供一种“适应性优势”。在利用基因簇数据挖掘寻找新的相关基因产物时，我们发现结直肠肿瘤中对应于一个先前未被鉴定的基因（ZKSCAN3）的表达序列标签过度表达。对ZKSCAN3进行研究有以下几个原因：（a）它与果蝇后肠发育所需的基因序列相似；（b）它位于结直肠癌中发生扩增的染色体区域（6p22.1）；（c）其编码序列预测存在串联C（2）H（2）锌指结构域，这类蛋白质因其在肿瘤发生/肿瘤进展中的作用而受到关注。逆转录 - PCR证实，与相邻的非恶性黏膜相比，结直肠肿瘤组织中ZKSCAN3过度表达，部分原因是通过Southern印迹法确定的基因扩增。此外，用针对预测蛋白质序列产生的抗体进行免疫组织化学分析显示，与非侵袭性肿瘤相比，侵袭性肿瘤中ZKSCAN3表达更高。有趣的是，ZKSCAN3蛋白在结直肠癌中常见的基因（APC、p53、K - Ras）野生型的肿瘤中也有表达。在两个独立的结肠癌细胞系中敲低ZKSCAN3会损害非锚定依赖性生长和原位肿瘤生长，而在第三个细胞系中过表达则有相反的效果，并增加5 - 氟尿嘧啶耐药性。脂质体递送靶向ZKSCAN3的小干扰RNA可降低原位结肠癌的致瘤性。因此，迄今为止未被鉴定的ZKSCAN3增加了一组不断扩大的对结直肠癌进展有作用的编码产物。
