Reeves Helen L, Narla Goutham, Ogunbiyi Olagunju, Haq Asif I, Katz Amanda, Benzeno Sharon, Hod Eldad, Harpaz Noam, Goldberg Shlomit, Tal-Kremer Sigal, Eng Francis J, Arthur Michael J P, Martignetti John A, Friedman Scott L
Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY 10029, USA.
Gastroenterology. 2004 Apr;126(4):1090-103. doi: 10.1053/j.gastro.2004.01.005.
BACKGROUND & AIMS: Kruppel-like factor 6 (KLF6) is a ubiquitous zinc finger tumor suppressor that is often mutated in prostate cancer. Our aims were to establish the frequency of KLF6 inactivation in sporadic and inflammatory bowel disease (IBD)-associated colorectal cancers (CRC); to correlate these abnormalities with mutation and/or loss of TP53, APC, and K-RAS; and to characterize the behavior of mutant KLF6 in colon-derived cell lines.
We analyzed DNA isolated from 50 microdissected CRC cases, including 35 sporadic and 15 IBD-associated tumors. Microsatellite analysis and direct sequencing were used to establish the incidence of microsatellite instability, KLF6 and TP53 allelic imbalance, and KLF6, K-RAS, TP53, and APC mutation. Loss of growth suppressive function of the CRC-derived KLF6 mutants was characterized by in vitro thymidine incorporation assays and Western blotting.
KLF6 was inactivated by loss and/or mutation in most sporadic and IBD-related CRCs. The KLF6 locus was deleted in at least 55% of tumors, and mutations were identified in 44%. Rates of KLF6 loss and mutation were similar to those of TP53 and K-RAS in the same samples. KLF6 mutations were present in tumors with either microsatellite or chromosomal instability and were more common, particularly in the IBD-related cancers, in the presence of wild-type APC. Unlike wild-type KLF6, cancer-derived KLF6 mutants neither suppressed growth nor induced p21 following transfection into cultured cells.
Deregulation of KLF6 by a combination of allelic imbalance and mutation may play a role in the development of CRC.
Kruppel样因子6（KLF6）是一种普遍存在的锌指肿瘤抑制因子，在前列腺癌中常发生突变。我们的目的是确定散发性和炎症性肠病（IBD）相关结直肠癌（CRC）中KLF6失活的频率；将这些异常与TP53、APC和K-RAS的突变和/或缺失相关联；并在结肠来源的细胞系中表征突变型KLF6的行为。
我们分析了从50例显微切割的CRC病例中分离的DNA，包括35例散发性肿瘤和15例IBD相关肿瘤。采用微卫星分析和直接测序来确定微卫星不稳定性、KLF6和TP53等位基因失衡以及KLF6、K-RAS、TP53和APC突变的发生率。通过体外胸苷掺入试验和蛋白质印迹法来表征CRC来源的KLF6突变体的生长抑制功能丧失情况。
在大多数散发性和IBD相关的CRC中，KLF6因缺失和/或突变而失活。至少55%的肿瘤中KLF6基因座缺失，44%的肿瘤中检测到突变。在相同样本中，KLF6缺失和突变的发生率与TP53和K-RAS相似。KLF6突变存在于微卫星或染色体不稳定的肿瘤中，并且在野生型APC存在的情况下更常见，尤其是在IBD相关癌症中。与野生型KLF6不同，癌症来源的KLF6突变体转染到培养细胞后既不抑制生长也不诱导p21。
等位基因失衡和突变共同导致的KLF6失调可能在CRC的发生发展中起作用。
