Inactivation of the tumor suppressor Krüppel-like factor 6 (KLF6) by mutation or decreased expression in hepatocellular carcinomas

Abstract

Background and aim: The Krüppel-like transcription factor KLF6 is a novel tumor-suppressor gene. It was inactivated in human prostate cancer and other tumors tissue, as the result of frequent mutation and loss of heterozygosity (LOH). However, there is no data reporting the levels of KLF6 both mRNA and protein in hepatocellular carcinomas (HCCs). We therefore detected mutations and expression of KLF6 in HCC tissues and further observed the effect of it on cell growth in HCC cell lines. Methods: We analyzed the exon-2 of KLF6 gene by direct DNA sequencing, and detected the expression of KLF6 by RT-PCR and Western blot in 23 HCC tissues and corresponding nontumorous tissues. Loss of growth suppressive effect of the HCC-derived KLF6 mutant was characterized by in vitro growth curves plotted, flow cytometry and Western blotting. Results: KLF6 mutations were found in 2 of 23 HCC tissues and one of mutations was missense. Expression of KLF6 mRNA or protein was down-regulated in 8 (34.7%) or 9 (39.1%) of 23 HCC tissues. Wild-type KLF6 (wtKLF6) inhibited cellular proliferation and prolonged G1-S transition by inducing the expression of p21WAF1 following stable transfection into cultured HepG2 cells, but tumor-derived KLF6 mutant (mKLF6) had no effects. Conclusion: Our findings suggest that KLF6 may be involved in pathogenesis of HCC.

In vivo regulation of p21 by the Kruppel-like factor 6 tumor-suppressor gene in mouse liver and human hepatocellular carcinoma

“…These findings complement our original report describing frequent loss and somatic mutation in primary HCC tumor samples (Kremer-Tal et al, 2004). In a separate study, somatic mutations were identified in 8.7% of patient samples (Pan et al, 2006). In addition, LOH was reported in 6.8% of tumors with no mutation or promoter methylation in a Korean cohort of HCCs (Song et al, 2006).…”

Decreased expression of KLF6 and its significance in gastric carcinoma

“…Generally, the inactivation of a tumor suppressor associated with loss of expression results from genetic or epigenetic alterations, such as mutation, allelic loss or hypermethylation of the promoter region of the genes. Recently, genetic alterations of KLF6 gene have been identified in several human cancers, including hepatocellular carcinoma, prostate cancer, head and neck squamous cell carcinoma, gastric and colon cancer [11,12,[23][24][25]. Interestingly, the KLF6 mRNA was also frequently down-regulated in non-small-cell lung cancer, glioblastoma and colon cancer cell lines [5,6,10,13,26].…”

KLF6 and TP53 mutations are a rare event in prostate cancer: distinguishing between Taq polymerase artifacts and true mutations

“…In contrast with the other studies, they only analyzed exon 2. None of the other studies included methods to [10][11][12][13] (ranging between 0 and 15%) and colorectal carcinoma [14][15][16][17][18] (ranging between 0 and 44%). Similar to prostate cancer, the first studies conducted on these other tumors indicated a high frequency of mutation, but this was not reproduced in subsequent reports.…”

“…9 The reported frequency of KLF6 mutations in different types of human cancer varies in the different published studies. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] In prostate cancer, four studies have analyzed the frequency of KLF6 mutations. 6,[30][31][32] In the first published study, Narla et al 6 showed a very high frequency, 55%, whereas in the following study, Chen et al 30 obtained a lower frequency, around 15%.…”