Molecular Cytogenetics of Solid Tumors

在过去的一年中，癌细胞的分子细胞遗传学和分子生物学取得了重大进展。在前列腺癌细胞系中确定13个POTE（在前列腺、卵巢、睾丸和胎盘中表达）旁系同源基因的分布，以观察基因激活是否依赖于基因重排。在具有许多染色体异常的细胞系中缺乏POTE重排表明不同的机制负责POTE激活。将染色体16 q24上含有细胞衰老基因（SEN 16）的85 kb细菌人工染色体克隆转移到乳腺癌细胞中，导致生长停滞和细胞衰老特征的细胞改变。编码淋巴特异性AT-钩转录因子的人AKNA基因定位于人染色体9 q32脆性位点FRA 9 E。脆性部位的损伤和基因重组与肿瘤的发生有关。在甲状腺癌小鼠模型中鉴定了涉及与人类甲状腺癌有关的几个基因的复发性染色体变化，从而为人类甲状腺癌提供了新的见解。一个复发易位t（5; 19）也被确定在一个癌细胞系来自自发性小鼠乳腺肿瘤。这种易位有助于Fgf 8基因的激活和乳腺细胞中雄激素依赖性的获得。DLC-1（在肝癌中缺失）在我们的实验室中被克隆，并显示在肝癌、乳腺癌、肺癌、卵巢癌、鼻咽癌、食管癌和宫颈癌中作为肿瘤抑制基因发挥作用。我们的新数据表明，DLC-1在乳腺癌中也是一种转移抑制基因，由于启动子超甲基化和组蛋白脱乙酰化，DLC-1在大量前列腺癌患者中下调和沉默。这些结果表明，DLC-1可能在预防乳腺癌转移（癌症死亡的主要原因）方面具有临床应用，其异常甲基化可能为前列腺癌的早期检测提供有用的生物标志物。在小鼠中靶向破坏DLC-1基因导致妊娠中期的胚胎死亡，表明该Rho GAP基因对哺乳动物的胚胎发育至关重要。DLC家族的另外两个成员，DLC-2和DLC-3，最近被确定，它们与DLC-1大约50%相同。使用癌症分析阵列，我们检测到肺癌、肾癌、子宫癌、卵巢癌和乳腺癌中DLC-1表达的下调，以及肺癌、卵巢癌、肾癌、子宫癌、胃癌、结肠癌和直肠癌中DLC-2表达的下调。此外，在前列腺肿瘤中发现这两种基因的表达降低，从而强调了该基因家族在各种人类癌症中的广泛参与。我们以前发现，小鼠Gtf 2 ird 1基因在一系列c-myc转基因小鼠中被破坏。Gtf 2 ird 1是发育障碍Williams-Beuren综合征（WBS）中半合子缺失基因之一的小鼠同源物。对Gtf 2 ird 1缺失转基因小鼠的详细分析表明，它们表现出与WBS患者相似的头骨和颌骨异常，这表明Gtf 2 ird 1可能在人类和小鼠的颅面发育中发挥作用。对丙型肝炎病毒（HCV）在B淋巴细胞中的感染有了新的认识。在一项合作研究中，已经证明HCV核心显著抑制B淋巴细胞凋亡，并显著下调表达HCV核心的B细胞中的MHC II类分子，而免疫球蛋白基因的表达没有显著改变。与此同时，白血病和B淋巴瘤相关的基因一致上调HCV核心。

In the past year significant progress has been made molecular cytogenetics and molecular biology of cancer cells. The distribution of 13 POTE (expressed in prostate, ovary, testis and placenta) paralogous genes was determined in prostate carcinoma cell lines, to see whether gene activation is dependent on gene rearrangements. Lack of POTE rearrangements in a cell line with many chromosomal abnormalities indicated a different mechanism was responsible for POTE activation. The transfer an 85-kb bacterial artificial chromosome clone, containing a cell senescence gene (SEN16) on chromosome 16q24, into breast cancer cells resulted in growth arrest and the cellular alterations characteristic of cell senescence. The human AKNA gene that encodes a lymphoid-specific AT-hook transcription factor was mapped to human chromosome 9q32 at fragile site FRA9E. Damage and gene recombination at fragile sites are associated with the development of neoplasia. Recurrent chromosome changes involving several genes that are implicated in human thyroid cancer were identified in a mouse model for thyroid cancer thus providing new insights in human thyroid cancer. A recurrent translocation t (5; 19) was also identified in a carcinoma cell line derived from a spontaneous mouse mammary tumor. This translocation is instrumental to the activation of Fgf8 gene and acquisition of androgen dependency in mammary cells. DLC-1 (deleted in liver cancer) was cloned in our laboratory and shown to function as a tumor suppressor gene in liver, breast, lung, ovarian, nasopharyngeal, esophageal, and cervical cancer. Our new data demonstrated that DLC-1 also functions as a metastasis suppressor gene in breast cancer and is down regulated and silenced in large number prostate cancer patients due to promoter hypermethylation and histone deacetylation. These results suggest that DLC-1 may have clinical applications in prevention of breast cancer metastasis, the major cause of cancer death, and its aberrant methylation may provide a useful biomarker for early detection of prostate cancer. Targeted disruption of the DLC-1 gene in mice resulted in to embryonic lethality at mid-gestation, showing that this Rho GAP gene is essential for embryonic development in mammals. Two additional members of the DLC family have recently been identified, DLC-2 and DLC-3, that are approximately 50% identical to DLC-1. Using a cancer-profiling array, we detected down regulation of DLC-1 expression in lung, renal, uterine, ovarian, and breast cancers and down-regulation of DLC-2 expression in lung, ovarian, renal, uterine, gastric, colon and rectal tumors. In addition, decreased expression of both genes was found in prostate tumors, thus underlining the wide involvement of this family of genes in various human cancers. We had previously found that the mouse Gtf2ird1 gene was disrupted in a line of c-myc transgenic mice. Gtf2ird1 is the mouse homolog of one of the genes hemizygously deleted in the developmental disorder Williams-Beuren syndrome (WBS). Detailed analysis of the Gtf2ird1-null transgenic mice showed that they exhibited abnormalities of the skull and jaws similar to those of WBS patients, indicating that Gtf2ird1 may have a role in craniofacial development in humans and mice. New insights into hepatitis C virus (HCV) infection in B-lymphocytes were obtained. In a collaborative study it has been demonstrated that HCV core significantly inhibited B-lymphocyte apoptosis and dramatically down-regulated MHC class II molecules in B cells expressing HCV core while the expression of immunoglobulin genes was not significantly altered. Meanwhile, genes associated with leukemia and B-lymphoma were consistently up regulated by HCV core.