A functional role for KLF6-SV1 in lung adenocarcinoma prognosis and chemotherapy response

Kruppel-like factor 6 (KLF6) is a tumor suppressor gene that is functionally inactivated in human cancer by loss of heterozygosity, somatic mutation, decreased expression, and increased alternative splicing into an oncogenic splice variant, KLF6-SV1. Here we show that increased expression of KLF6-SV1 is associated with decreased survival in patients with lung adenocarcinoma. In addition, KLF6-SV1 is a novel antiapoptotic protein in lung cancer cell lines, and targeted reduction of KLF6-SV1 using siRNA induces apoptosis both alone and in combination with the chemotherapeutic drug cisplatin. Together, these findings highlight a critical role for KLF6-SV1 in lung cancer, and show a potential novel therapeutic strategy for the treatment of lung cancer.     

Roles of KLF6 and KLF6-SV1 in ovarian cancer progression and intraperitoneal dissemination.

PURPOSE: We investigated the role of the KLF6 tumor suppressor gene and its alternatively spliced isoform KLF6-SV1 in epithelial ovarian cancer (EOC). EXPERIMENTAL DESIGN: We first analyzed tumors from 68 females with EOC for KLF6 gene inactivation using fluorescent loss of heterozygosity (LOH) analysis and direct DNA sequencing and then defined changes in KLF6 and KLF6-SV1 expression levels by quantitative real-time PCR. We then directly tested the effect of KLF6 and KLF6-SV1 inhibition in SKOV-3 stable cell lines on cellular invasion and proliferation in culture and tumor growth, i.p. dissemination, ascites production, and angiogenesis in vivo using BALB/c nu/nu mice. All statistical tests were two sided. RESULTS: LOH was present in 59% of samples in a cell type-specific manner, highest in serous (72%) and endometrioid (75%) subtypes, but absent in clear cell tumors. LOH was significantly correlated with tumor stage and grade. In addition, KLF6 expression was decreased in tumors when compared with ovarian surface epithelial cells. In contrast, KLF6-SV1 expression was increased approximately 5-fold and was associated with increased tumor grade regardless of LOH status. Consistent with these findings, KLF6 silencing increased cellular and tumor growth, angiogenesis, and vascular endothelial growth factor expression, i.p. dissemination, and ascites production. Conversely, KLF6-SV1 down-regulation decreased cell proliferation and invasion and completely suppressed in vivo tumor formation. CONCLUSION: Our results show that KLF6 and KLF6-SV1 are associated with key clinical features of EOC and suggest that their therapeutic targeting may alter ovarian cancer growth, progression, and dissemination.     

Increased alternative splicing of the KLF6 tumour suppressor gene correlates with prognosis and tumour grade in patients with pancreatic cancer

The aim of this study was to correlate the status of the KLF6 tumour suppressor gene including loss of heterozygosity (LOH), mutation and alternative splicing in human pancreatic cancer with tumour grade and survival. Whereas neither KLF6 loss nor mutation was identified, expression of the KLF6 alternative splice forms was significantly increased in pancreatic tumour samples and cell lines. These cancers demonstrated marked cytoplasmic KLF6 expression, consistent with over-expression and accumulation of KLF6 splice form(s), which lack a nuclear localisation signal. In addition, KLF6 splicing correlated significantly with tumour stage and survival. In summary, pancreatic cancer displays a novel pattern of KLF6 dysregulation through selectively increased expression of KLF6 splice variants. Therefore, determination of KLF6 mRNA splicing levels may represent a novel biomarker predicting prognosis.     

A small interfering RNA targeting the KLF6 splice variant,KLF6-SV1, as gene therapy for gastric cancer

Background  

Accumulating evidence suggests that the tumor suppressor gene Kruppel-like factor 6 (KLF6) and its dominant-negative splice form KLF6-SV1 play important roles in both the development and progression of cancer. However, the role of KLF6-SV1 in gastric cancer remains largely unknown.     

Analysis of human prostate cancers and cell lines for mutations in the TP53 and KLF6 tumour suppressor genes

A recent report suggests that the KLF6 gene encoding the Krüppel-like factor 6 protein is a frequently mutated, putative tumour suppressor gene in prostate cancer. The aims of the present study were to confirm these initial findings by determining the frequency of exon2 KLF6 mutations in a cohort of European prostate cancer patients, and to investigate whether there was evidence for mutational inactivation of both the KLF6 and TP53 tumour suppressor loci in some tumours. We examined 32 primary prostate tumours and three prostate tumour cell lines for mutations by PCR amplification and direct dideoxy sequencing (KLF6), and by oligonucleotide microarray (p53GeneChip) analysis and dideoxy sequencing (TP53). Whereas TP53 mutations typical of prostate cancer were found at a frequency consistent with the literature, no KLF6 mutations were found in any of the tumour samples nor in the three prostate cancer cell lines.     

鼻咽癌中KLF6基因突变的检测

背景与目的：鼻咽癌（nasopharyngeal carcinoma,NPC)高发于中国南方和东南亚地区,其发病是一个多因素,多步骤的过程,与遗传因素,EB病毒感染和环境因子有关,但分子机理仍不清楚,KLF6基因编码一种广泛表达的核转录因子,在某些前列腺癌肿瘤中发现有高频的等位基因的丢失和基因突变,本研究通过对KLF6基因在NPC肿瘤中的突变检测,探讨KLF6基因与NPC发病的关系。方法：采用PCR-直接测序分析方法。在19例散发性NPC组织细胞和3个NPC细胞系（CNE1,CNE2,SUNE1）中对KLF6编码区和拼接位点进行检测。结果：在3你散发性NPC肿瘤组织DNA中检测到KLF6基因的3个不同位置的错义改变,分别为GAG→TG（Glu75Val),AGG→AGG（Ser136Arg)和AGA→AAA（Arg243Lys),在50个随机正常个体（100条染色体）和3个NPC细胞系中没有发现这3个位点的碱基变异,结论：这3个变异可能是KLF6基因的新的突变位点,在某些NPC发病中可能有作用。     

Cyclin-dependent kinase inhibition by the KLF6 tumor suppressor protein through interaction with cyclin D1

Kruppel-like factor 6 (KLF6) is a tumor suppressor gene inactivated in prostate and colon cancers, as well as in astrocytic gliomas. Here, we establish that KLF6 mediates growth inhibition through an interaction with cyclin D1, leading to reduced phosphorylation of the retinoblastoma protein (Rb) at Ser(795). Furthermore, introduction of KLF6 disrupts cyclin D1-cyclin-dependent kinase (cdk) 4 complexes and forces the redistribution of p21(Cip/Kip) onto cdk2, which promotes G(1) cell cycle arrest. Our data suggest that KLF6 converges with the Rb pathway to inhibit cyclin D1/cdk4 activity, resulting in growth suppression.     

KLF6基因在前列腺癌中突变的研究

目的:研究KLF6基因在前列腺癌中的遗传状况。方法:应用DHPLC技术、LOH和直接测序的方法,检测了320例局限性前列腺癌和28例有远处转移的前列腺癌标本中KLF6基因的突变。结果:采用DH-PLC方法在3组(245例)前列腺癌标本中筛选有异常信号的标本,然后直接测序,未发现KLF6基因的突变;将其中55例标本行LOH分析,发现6例阳性标本,亚克隆后直接测序也未发现有KLF6的突变。在另外75例标本和28例转移性前列腺癌标本中分别发现1例纯合性和杂合性体细胞突变。KLF6基因在前列腺癌中突变率很低。结论:KLF6基因突变在前列腺癌中很少见,对其在前列腺癌中作用有待于进一步的研究。