Aberrant expression of krÜppel-like factor 6 protein in colorectal cancers

The role of natural products versus miRNA in renal cell carcinoma: implications for disease mechanisms and diagnostic markers

Natural products are chemical compounds produced by living organisms. They are isolated and purified to determine their function and can potentially be used as therapeutic agents. The ability of some bioactive natural products to modify the course of cancer is fascinating and promising. In the past 50 years, there have been advancements in cancer therapy that have increased survival rates for localized tumors. However, there has been little progress in treating advanced renal cell carcinoma (RCC), which is resistant to radiation and chemotherapy. Oncogenes and tumor suppressors are two roles played by microRNAs (miRNAs). They are involved in important pathogenetic mechanisms like hypoxia and epithelial-mesenchymal transition (EMT); they control apoptosis, cell growth, migration, invasion, angiogenesis, and proliferation through target proteins involved in various signaling pathways. Depending on their expression pattern, miRNAs may identify certain subtypes of RCC or distinguish tumor tissue from healthy renal tissue. As diagnostic biomarkers of RCC, circulating miRNAs show promise. There is a correlation between the expression patterns of several miRNAs and the prognosis and diagnosis of patients with RCC. Potentially high-risk primary tumors may be identified by comparing original tumor tissue with metastases. Variations in miRNA expression between treatment-sensitive and therapy-resistant patients' tissues and serum allow for the estimation of responsiveness to target therapy. Our knowledge of miRNAs' function in RCC etiology has a tremendous uptick. Finding and validating their gene targets could have an immediate effect on creating anticancer treatments based on miRNAs. Several miRNAs have the potential to be used as biomarkers for diagnosis and prognosis. This review provides an in-depth analysis of the current knowledge regarding natural compounds and their modes of action in combating cancer. Also, this study aims to give information about the diagnostic and prognostic value of miRNAs as cancer biomarkers and their involvement in the pathogenesis of RCC.

The role of KLF transcription factor in the regulation of cancer progression

Kruppel-like factors (KLFs) are a family of zinc finger transcription factors that have been found to play an essential role in the development of various human tissues, including epithelial, teeth, and nerves. In addition to regulating normal physiological processes, KLFs have been implicated in promoting the onset of several cancers, such as gastric cancer, lung cancer, breast cancer, liver cancer, and colon cancer. To inhibit cancer progression, various existing medicines have been used to modulate the expression of KLFs, and anti-microRNA treatments have also emerged as a potential strategy for many cancers. Investigating the possibility of targeting KLFs in cancer therapy is urgently needed, as the roles of KLFs in cancer have not received enough attention in recent years. This review summarizes the factors that regulate KLF expression and function at both the transcriptional and posttranscriptional levels, which could aid in understanding the mechanisms of KLFs in cancer progression. We hope that this review will contribute to the development of more effective anti-cancer medicines targeting KLFs in the future.

MUTYH and KLF6 gene expression fluctuations in tumor tissue and tumor margins tissues of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most important cancers in the world, and its prevalence varies depending on the geographical area. Genetically, tumor regeneration in CRC as a multi-step process involves activating mutations in protocogenes and losing the function of tumor suppressor genes as well as DNA repair and recovery genes. Occur in this way, our goal was to investigate the expression of KLF6 genes as a tumor suppressor and MUTYH involved in the DNA repair process in colorectal cancer.

METHODS

This research was conducted during the years 2019-2018 in Razi Hospital, Rasht. The subjects included 30 tumoral and 30 non-tumoral tissues of colorectal cancer and 20 healthy controls. The real-time PCR method was used to investigate the gene expression. For data analysis by SPSS, parametric statistical tests ANOVA and T test and regression analysis were used and p value values less than 0.05 were considered significant.

RESULTS

The expression of KLF6 gene in tumoral tissues showed a significant decrease compared to non-tumoral tissues (P = 0.04). Also, the expression of MUTYH gene in tumor tissue showed a significant decrease compared to non-tumoral (P = 0.02) and this decrease in MUTYH gene expression had a significant relationship with increasing tumor stage (P = 0.01).

CONCLUSION

These findings suggest that decreased expression of KLF6 and MUTYH genes in the study population has a significant relationship with colorectal cancer and can be considered as tumor marker in diagnostic purpose.

Enabling factor for cancer hallmark acquisition: Small nucleolar RNA host gene 17

The role of long non-coding RNA (lncRNA) in human tumors has gradually received increasing attention in recent years. Particularly, the different functions of lncRNAs in different subcellular localizations have been widely investigated. The upregulation of lncRNA small nucleolar RNA host gene 17 (SNHG17) has been observed in various human tumors. Growing evidence has proved that SNHG17 plays a tumor-promoting role in tumorigenesis and development. This paper describes the molecular mechanisms by which SNHG17 contributes to tumor formation and development. The different functions of SNHG17 in various subcellular localizations are also emphasized: its function in the cytoplasm as a competing endogenous RNA (ceRNA), its action in the nucleus as a transcriptional coactivator, and its function through the polycomb repressive complex 2 (PRC2)-dependent epigenetic modifications that regulate transcriptional processes. Finally, the correlation between SNHG17 and human tumors is summarized. Its potential as a novel prognostic and diagnostic biomarker for cancer is explored especially.

Krüppel-Like Factor 6 Downregulation Is Connected with a Poor Prognosis and Tumor Growth in Non-Small-Cell Lung Cancer

PURPOSE

Research in this article was performed to explore the biological role and clinical significance of Krüppel-like transcription factor 6 (KLF6) in non-small-cell lung cancer (NSCLC).

METHODS

KLF6 expression in NSCLC cell lines was analyzed using reverse transcription PCR and Western blot. The expressed KLF6 protein was examined in 50 surgical NSCLC tissues using immunohistochemistry. Statistical analyses were employed for clinical association examinations. CCK8 assay and Annexin V/PI analysis were used to execute cell proliferation and apoptosis in KLF6-overexpression cell lines and the control groups. Cleaved caspase-3 expression was also detected in KLF6-overexpression cells and NSCLC tissues. KLF6 expression correlation with cleaved caspase-3 was also examined.

RESULTS

It was discovered that downregulation of KLF6 was seen in human NSCLC cell lines. Low KLF6 expression in NSCLC tissues was correlated with poor patient prognosis (P < 0.005); patients with less KLF6 expression possessed a lower cumulative 5-year survival rate. Multivariate analysis showed KLF6 expression as an independent prognostic indicator for NSCLC individuals. Expression levels of KLF6 were associated with NSCLC tumor size (P = 0.041). Overexpression of KLF6 inhibited cell proliferation and stimulated A549 and H322 cell line apoptosis. Cleaved caspase-3 protein had higher expression levels in KLF6-overexpressed cells than in the control group. The KLF6 expression levels were positively related to the cleaved caspase-3 protein expression in NSCLC tissues (r = 0.689, P = 0.001).

CONCLUSIONS

The results indicate that downregulation of KLF6 is a significant NSCLC progression marker. KLF6 prevents cell growth and promotes cell apoptosis, possibly caspase-3 activations.

CircNOL10 Acts as a Sponge of miR-135a/b-5p in Suppressing Colorectal Cancer Progression via Regulating KLF9

Background

Circular RNAs (circRNAs) have been documented as key regulators during progression of malignant human cancer, including colorectal cancer (CRC). However, the underlying molecular mechanisms of circNOL10 in CRC remain unclear.

Methods

The real-time quantitative polymerase chain reaction was used to quantify the expression of circNOL10, miR-135a-5p, miR-135b-5p, and Krüppel-like factor 9 (KLF9). Kaplan–Meier curve was employed to assess the relationship between survival time of CRC patients and expression level of circNOL10. Cell ability of proliferation was measured by Cell Counting Kit8 and colony formation assays. Cell-cycle analysis was performed using flow cytometry assay. In addition, migration and invasion of CRC cell were examined with transwell analysis. The protein expression level was measured with Western blot assay. The interaction relationship of different molecules was analyzed by bioinformatics database and confirmed by dual-luciferase reporter, RNA immunoprecipitation, and RNA pulldown assay. The functional role of circNOL10 in vivo was determined by xenograft experiment.

Results

CircNOL10 was decreased in CRC tissues and cells and was associated with poor outcomes. Gain-of-functional experiment revealed that overexpression of circNOL10 constrained proliferation, cell-cycle progression, migration, and invasion of CRC cells, which was abolished by overexpression of miR-135a-5p or miR-135b-5p. Additionally, miR-135a-5p and miR-135b-5p, targets of circNOL10, regulated KLF9 expression in a negative feedback. Consistently, the results of xenograft experiment suggested that overexpression of circNOL10 inhibited tumor growth in vivo.

Conclusion

In summary, our results showed that circNOL10 impeded CRC development by mediating proliferation, cell cycle, migration, and invasion by sponging miR-135a-5p and miR-135b-5p, which provided new understanding for CRC treatment.

Upregulated Long Noncoding RNA LINC01234 Predicts Unfavorable Prognosis for Colorectal Cancer and Negatively Correlates With KLF6 Expression

Background

LINC01234, a long noncoding RNA (lncRNA), is overexpressed in several cancers, including colorectal cancer (CRC). We investigated the role of LINC01234 in CRC development and confirmed its correlation with Krüppel-like factor 6 (KLF6), a tumor suppressor gene that is dysregulated in CRC.

Methods

We tested mRNA levels using quantitative reverse transcription PCR (qRT-PCR). Tissue samples from patients with CRC, inflammatory bowel disease (IBD), hyperplastic polyp, and adenoma were included. Correlations between clinicopathological parameters, overall survival (OS) rate, and LINC01234 were analyzed using Kruskal-Wallis H test. Additionally, cell proliferation, apoptosis, and tumor formation in nude mice were tested to investigate the mechanism of LINC01234. Western blotting was used to determine protein levels.

Results

LINC01234 expression was significantly upregulated in CRC tissues and CRC cell lines than in non-tumor tissues and normal epithelial cells, respectively. LINC01234 was associated with high tumor stage, larger tumor size, and metastasis. Patients with higher LINC01234 expression showed reduced OS. Cell proliferation was inhibited by LINC01234 knockdown, whereas apoptosis was enhanced. Mice injected with SW480 cells with LINC01234 knockdown displayed decreased tumor volume, weight, and Ki-67 levels compared with those injected with control cells. KLF6 was negatively regulated by LINC01234. Overexpression of KLF6 showed effects similar to those observed following LINC01234 knockdown on cell proliferation and apoptosis.

Conclusions

LINC01234 could be a prognostic biomarker in CRC patients. Upregulation of LINC01234 in CRC promotes tumor development through negative regulation of KLF6.

Hypermethylated KLF9 Is An Independent Prognostic Factor For Favorable Outcome In Breast Cancer

Background and objective

Breast cancer (BC) is the most lethal human malignancy and is the leading cause of cancer-associated death in women worldwide. Krüppel-like factor 9 (KLF9) belongs to a family of transcriptional regulators and its role in BC has not been fully investigated.

Method

Data mining was used to analyze BC data from The Cancer Genome Atlas (TCGA) database, which was downloaded using the UCSC Xena browser. The differential expression and methylation level of KLF9 was analyzed in patients with BC and corresponding normal controls enrolled from our hospital. Besides, the correlation of KLF9 methylation and prognosis was explored, and gene set enrichment analysis (GSEA) was conducted to identify the potential signaling pathway of KLF9 involved.

Results

Both TCGA and BC tissues indicated hypermethylation of the KLF9 promoter region in patients with BC compared with normal controls, which might account for the dysregulation of KLF9 in patients with BC. Besides, hypermethylation of KLF9 was detected in patients with estrogen or progesterone receptor-positive and non-triple-negative disease. Further, hypermethylation of KLF9 was demonstrated to be a potential independent biomarker in obtaining favorable outcomes in BC. By GSEA, tumor-associated biological processes and signaling pathway were identified, which indicated that KLF9 might play a vital role in the carcinogenesis of BC.

Conclusion

KFL9 plays an important role in the carcinogenesis of BC through the multiple tumor-associated signaling pathway. The hypermethylation of KLF9 resulted in its reduced expression in BC, while the hypermethylation of KLF9 has potential in the prediction of favorable outcomes in BC.

Epigenetic profiling of MUTYH, KLF6, WNT1 and KLF4 genes in carcinogenesis and tumorigenesis of colorectal cancer

Colorectal cancer (CRC) is distinguished by epigenetic elements like DNA methylation, histone modification, histone acetylation and RNA remodeling which is related with genomic instability and tumor initiation. Correspondingly, as a main epigenetic regulation, DNA methylation has an impressive ability in order to be used in CRC targeted therapy. Meaningly, DNA methylation is identified as one of most important epigenetic regulators in gene expression and is considered as a notable potential driver in tumorigenesis and carcinogenesis through gene-silencing of tumor suppressors genes. Abnormal methylation situation, even in the level of promoter regions, does not essentially change the gene expression levels, particularly if the gene was become silenced, leaving the mechanisms of methylation without any response. According to the methylation situation which has a strong eagerness to be highly altered on CpG islands in carcinogenesis and tumorigenesis, considering its epigenetic fluctuations in finding new biomarkers is of great importance. Modifications in DNA methylation pattern and also enrichment of methylated histone signs in the promoter regions of some certain genes like MUTYH, KLF4/6 and WNT1 in different signaling pathways could be a notable key contributors to the upregulation of tumor initiation in CRC. These epigenetic alterations could be employed as a practical diagnostic biomarkers for colorectal cancer. In this review, we will be discuss these fluctuations of MUTYH, KLF4/6 and WNT1 genes in CRC.

MicroRNA‑18b acts as an oncogene in gastric cancer by directly targeting Kruppel‑like factor 6

Gastric cancer (GC) is the fourth most frequently occurring cancer and the second most common cause of cancer‑associated mortality worldwide. An increasing number of studies have reported that microRNAs (miRNAs/miRs) contribute to the regulation of GC development and progression. Therefore, investigation of the miRNAs involved in the development of GC may result in identification of an effective therapeutic target for patients with this malignancy. miR‑18b has been reported to be aberrantly expressed in several types of human cancer. However, the expression pattern, biological role and specific functional mechanism of miR‑18b in GC remains to be elucidated. In the present study, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis revealed that miR‑18b was significantly upregulated in GC tissues and cell lines compared with normal gastric tissues and the human gastric epithelial immortalized cell line GES‑1, respectively. High miR‑18b expression was significantly associated with lymph node metastasis, invasive depth and the Tumor Node Metastasis stage of patients with GC. Additionally, functional assays indicated that the inhibition of miR‑18b attenuated cell proliferation and invasion in GC. Furthermore, Kruppel‑like factor (KLF)‑6 was identified as a direct target gene of miR‑18b in GC, from the results of bioinformatics analysis, a luciferase reporter assay, RT‑qPCR and western blot analysis. An inverse association was observed between miR‑18b and KLF6 mRNA levels in GC tissues. KLF6 knockdown partially abrogated the effects of miR‑18b inhibition on GC cell proliferation and invasion. Therefore, miR‑18b/KLF6 targeted therapy may provide a promising treatment for patients with GC.

Screening key long non-coding RNAs in early-stage colon adenocarcinoma by RNA-sequencing

AIM

We aim to identify the key long noncoding RNAs (lncRNAs) in early-stage colon adenocarcinoma (COAD).

PATIENTS & METHODS

Compared with colonic intraepithelial neoplasia, differentially expressed lncRNAs (DElncRNAs) in early-stage COAD were obtained by RNA-sequencing. Our previous work has obtained the differentially expressed mRNAs and miRNAs (DEmRNAs and DEmiRNAs) in early-stage COAD. DEmiRNA-DElncRNA-DEmRNA interaction analysis and functional annotation were performed. Validation of expression and receiver-operating characteristic analyses were performed based on The Cancer Genome Atlas.

RESULTS

Seventy-nine significantly DElncRNAs in early-stage COAD were obtained. MiR-153-3p-TUG1-DAPK1/ARNT2/KLK3/PLD1/SMAD2 and miR-153-3p-SNHG17-COL11A1/IGFBP3/KLF6 interactions were associated with early-stage COAD. Five DElncRNAs (ELFN1-AS1, LINC01234, SNHG17, UCA1 and LOC101929549) involved in early-stage COAD with potential diagnostic value.

CONCLUSION

LncRNAs involve in early-stage COAD by interaction with COAD-regulated genes and miRNAs.

Characterization of the prostate cancer susceptibility gene KLF6 in human and mouse prostate cancers

BACKGROUND

Krüppel-like factor (KLF) 6 is a candidate tumor suppressor gene in prostate cancer, but the mechanisms contributing to its loss of expression are poorly understood. We characterized KLF6 expression and DNA methylation status during prostate tumorigenesis in humans and mice.

METHODS

KLF6 expression was assessed in matched human non-malignant (NM) and tumor prostate tissues (n = 22) by quantitative real-time PCR (qPCR) and in three independent human prostate cancer cohorts bioinformatically. QPCR for KLF6 expression and methylation-sensitive PCR (MSP) were performed in human prostate LNCaP cancer cells after 5-aza-2'-deoxycytidine treatment. Klf6 protein levels and DNA promoter methylation were assessed in TRansgenic Adenocarcinoma of Mouse Prostate (TRAMP) tumors by immunohistochemistry and MSP, respectively.

RESULTS

KLF6 splice variants expression was increased (P = 0.0015) in human prostate tumors compared to NM tissues. Overall, KLF6 was decreased in metastatic compared to primary prostate cancers and reduced expression in primary tumors was associated with a shorter time to relapse (P = 0.0028). Treatment with the demethylating agent 5-aza-2'-deoxycytidine resulted in up-regulation of KLF6 expression (two-fold; P = 0.002) and a decrease in DNA methylation of the KLF6 promoter in LNCaP cells. Klf6 protein levels significantly decreased with progression in the TRAMP model of prostate cancer (P < 0.05), but there was no difference in Klf6 promoter methylation.

CONCLUSION

KLF6 expression was decreased in both clinical prostate cancer and the TRAMP model with disease progression, but this could not be explained by DNA methylation of the KLF6 promoter.

SP1 regulates the transcription of BMPR1A

BACKGROUND

BMPR1A is a cell surface receptor in the bone morphogenetic protein (BMP) pathway. Mutations in BMPR1A predispose to juvenile polyposis (JP). Sp1 and related proteins are widely expressed regulators of gene transcription, including members of the BMP pathway. We set out to identify important transcription factor binding sites (TFBS) in the recently identified BMPR1A promoter and to assess for the role of Sp1 and associated proteins in its regulation.

MATERIALS AND METHODS

The BMPR1A promoter was cloned into a luciferase reporter vector. Deletion fragments of this promoter insert were then constructed, of varying lengths and opposing directions, and were used to transfect HEK-293 and CRL-1459 cells. In silico analysis was performed to screen for relevant TFBS. Site-directed mutagenesis (SDM) was then employed to individually disrupt these TFBS in the wild-type (WT) vector. SDM constructs were then assessed for activity.

RESULTS

Light activity from the deletion constructs ranged between 3% and 129% of the WT promoter. ModelInspector identified eight potential binding sites for Sp1- and Sp1-associated proteins that mapped to areas of marked loss or gain of activity from the deletion constructs. SDM of these TFBS led to a drop in activity in five mutants, which included 3 Sp1 sites, an ETSF site, and NFκB site.

CONCLUSIONS

By combining in silico analysis and experimental data, Sp1 was found to be a candidate factor that likely plays a role in the transcriptional regulation of BMPR1A. This study potentially provides further insight toward the molecular basis of JP, and suggests that Sp1 plays a role in BMP signaling.

Expression and Function of Kruppel Like-Factors (KLF) in Carcinogenesis

Krüppel-like factor (KLF) family members share a three C2H2 zinc finger DNA binding domain, and are involved in cell proliferation and differentiation control in normal as in pathological situations. Studies over the past several years support a significant role for this family of transcription factors in carcinogenesis. KLFs can both activate and repress genes that participate in cell-cycle regulation. Among them, many up-regulated genes are inhibitors of proliferation, whereas genes that promote cell proliferation are repressed. However, several studies do present KLFs as positive regulator of cell proliferation. KLFs can be deregulated in multiple cancers either by loss of heterozygosity (LOH), somatic mutation or transcriptional silencing by promoter hypermethylation. Accordingly, KLF expression was shown to mediate growth inhibition when ectopically expressed in multiple cancer-derived cell lines through the inhibition of a number of key oncogenic signaling pathways, and to revert the tumorogenic phenotype in vivo. Taken together, these observations suggest that KLFs act as tumor suppressor. However, in some occasion, KLFs could act as tumor promoters, depending on “cellular context”. Thus, this review will discuss the roles and the functions of KLF family members in carcinogenesis, with a special focus on cancers from epithelial origin.

Mammalian Krüppel-like factors in health and diseases

The Krüppel-like factor (KLF) family of transcription factors regulates diverse biological processes that include proliferation, differentiation, growth, development, survival, and responses to external stress. Seventeen mammalian KLFs have been identified, and numerous studies have been published that describe their basic biology and contribution to human diseases. KLF proteins have received much attention because of their involvement in the development and homeostasis of numerous organ systems. KLFs are critical regulators of physiological systems that include the cardiovascular, digestive, respiratory, hematological, and immune systems and are involved in disorders such as obesity, cardiovascular disease, cancer, and inflammatory conditions. Furthermore, KLFs play an important role in reprogramming somatic cells into induced pluripotent stem (iPS) cells and maintaining the pluripotent state of embryonic stem cells. As research on KLF proteins progresses, additional KLF functions and associations with disease are likely to be discovered. Here, we review the current knowledge of KLF proteins and describe common attributes of their biochemical and physiological functions and their pathophysiological roles.

Gene dysregulations driven by somatic copy number aberrations-biological and clinical implications in colon tumors: a paper from the 2009 William Beaumont Hospital Symposium on Molecular Pathology

The majority of colorectal cancer (CRC) cases have chromosomal instability, in which the tumor genome is characterized by gross chromosomal aberrations such as gains in 20q, 13q, 8q, and 7, and losses in 4, 8p, 18q, and 17p. These somatic copy number changes (gains, losses, and somatic uniparental disomies) are crucial to CRC progression as they drive genes toward cancer-promoting (oncogenic or tumor suppressive) states. Numerous studies have shown that the loss of 18q or 8p is associated with poorer clinical outcome in CRCs. Either chromosomal arm may contain a tumor suppressor gene (or genes), whose deactivation by copy loss (loss of wild-type allele, decreased expression) can be crucial to the later stages of cancer progression. Our own integrated genomic analysis (single nucleotide polymorphism array, expression array) of more than 200 CRC tumor and normal samples indicates that the overall down-regulation of genes within the 8p or 18q arm is associated with lower survival rate. Among the often down-regulated, poor prognosis-associated 8p genes is MTUS1, whose gene product (a mitotic spindle-associated protein) was recently demonstrated to have a tumor suppressive property. Within 18q is ATP5A1, which codes for the catalytic a component of mitochondrial H(+)-ATP synthase. Like SMAD4 (also in 18q), the decreased expression of ATP5A1 appears to be a marker of unfavorable clinical outcome in CRCs.

Gene expression in colorectal neoplasia: modifications induced by tissue ischaemic time and tissue handling protocol

AIMS

The heterogeneity within individual distinct cancer types in terms of behaviour, response to therapy and prognosis is well recognized. A major goal of translational research projects has therefore been to define clinically significant subgroups of individual tumour types by analysis of mRNA as well as protein expression. An essential premise of such investigations is that expression of these key molecules is a true reflection of conditions present within the neoplastic cells in vivo. The aim was to investigate the effect of methods of tissue handling and storage on expression of mRNA.

METHODS AND RESULTS

mRNA expression in 60 biopsy samples obtained from 10 patients with colorectal tumours was examined. The mRNA expression profile and the level of expression of specific mRNA species were significantly affected by the procedures used for collection and storage of tissue samples. Significant variation in the level of expression (both increased and decreased) of transcripts was detectable after 15 min, and by 120 min there was a fourfold increase in the number of genes with a more than twofold change in the level of expression.

CONCLUSIONS

Reliable interpretation of results of gene expression at the mRNA level requires standardized protocols for tissue procurement.

Krüppel-like factor 12 plays a significant role in poorly differentiated gastric cancer progression

Gastric cancer is the second common malignant neoplasia in Japan, and its poorly differentiated form is a deadly disease. To identify novel candidate oncogenes contributing to its genesis, we examined copy-number alterations in 50 primary poorly differentiated gastric cancers using an array-based comparative genomic hybridization (array-CGH). Many genetic changes were identified, including a novel amplification of the 13q22 locus. Several genes are located in this locus, and selective knockdown of one for the Krüppel-like factor 12 (KLF12) induced significant growth-arrest in the HGC27 gastric cancer cell line. Microarray analysis also demonstrated that genes associated with cell proliferation were mostly changed by KLF12 knockdown. To explore the oncogenic function of KLF12, we introduced a full length of human KLF12 cDNA into NIH3T3 and AZ-521 cell lines and found that overexpression significantly enhanced their invasive potential. In clinical samples, KLF12 mRNA in cancer tissue was increased in 11 of 28 cases (39%) when compared with normal gastric epithelium. Clinicopathological analysis further demonstrated a significant correlation between KLF12mRNA levels and tumor size (p = 0.038). These data suggest that the KLF12 gene plays an important role in poorly differentiated gastric cancer progression and is a potential target of therapeutic measures.

Downregulation of Krüppel-like factor 9 in human colorectal cancer

Mammalian Sp and Krüppel-like factors (KLF), a family of zinc finger-containing transcription factors, are involved in growth control, proliferation, apoptosis and angiogenesis of a wide variety of tissues and cells. Several KLF have been linked to various types of human cancers, but the relationship between Krüppel-like factor 9 (KLF9) and colorectal cancer has not been explored. The purpose of the present study was to investigate KLF9 expression in human colorectal cancer tissue. KLF9 mRNA was detected on quantitative real-time reverse transcriptase-polymerase chain reaction (Q-PCR). Of the 50 cancerous tissues examined, 86% (43/50) expressed lower levels of KLF9 mRNA than individually matched normal mucosa (P < 0.0001). On western blot, reduced or absent expression of KLF9 protein was observed in 65% (13/20) of the samples (P < 0.01). A total of 81% (35/43) of normal samples had expression of KLF9 protein, whereas its protein was detected in only 9% (4/43) of tumor tissues (P < 0.001) on tissue microarray. These results indicate that KLF9 may be involved in the carcinogenesis of human colorectal cancer.

The Pathobiology of Krüppel-like Factors in Colorectal Cancer

The Krüppel-like factor (KLF) proteins are zinc finger-containing transcription factors that exert important functions in regulating diverse biologic processes such as growth, proliferation, differentiation, development, inflammation, and apoptosis. Many KLFs have also been shown to play significant roles in tumorigenesis of various organs and tissues. Three in particular-KLF4, KLF5, and KLF6-are often dysregulated in tumors of the gastrointestinal tract, including colorectal cancer. This article reviews the functions of these three KLFs in normal gastrointestinal biology and their pathobiologic roles in colorectal cancer.

Caffeine regulates alternative splicing in a subset of cancer-associated genes: a role for SC35

Alternative splicing of pre-mRNA contributes significantly to human proteomic complexity, playing a key role in development, gene expression and, when aberrant, human disease onset. Many of the factors involved in alternative splicing have been identified, but little is known about their regulation. Here we report that caffeine regulates alternative splicing of a subset of cancer-associated genes, including the tumor suppressor KLF6. This regulation is at the level of splice site selection, occurs rapidly and reversibly, and is concentration dependent. We have recapitulated caffeine-induced alternative splicing of KLF6 using a cell-based minigene assay and identified a "caffeine response element" within the KLF6 intronic sequence. Significantly, a chimeric minigene splicing assay demonstrated that this caffeine response element is functional in a heterologous context; similar elements exist within close proximity to caffeine-regulated exons of other genes in the subset. Furthermore, the SR splicing factor, SC35, was shown to be required for induction of the alternatively spliced KLF6 transcript. Importantly, SC35 is markedly induced by caffeine, and overexpression of SC35 is sufficient to mimic the effect of caffeine on KLF6 alternative splicing. Taken together, our data implicate SC35 as a key player in caffeine-mediated splicing regulation. This novel effect of caffeine provides a valuable tool for dissecting the regulation of alternative splicing of a large gene subset and may have implications with respect to splice variants associated with disease states.

Genome-wide single nucleotide polymorphism analysis of lung cancer risk detects the KLF6 gene

A genome-wide association analysis using the Affymetrix 100K SNP array was carried out in a case-control study of lung cancer. Allele frequencies were estimated initially in DNA pools. Significant differences in allele frequency detected in the SNP array analysis were first tested in the same DNA pools by pyrosequencing and then by individual genotyping. DNA pooling analysis identified rs10508266 SNP, located approximately 12.5kb from the 5'-end of the KLF6 gene, as a marker showing significant association with lung cancer risk. Since the SNP was in significant linkage disequilibrium with the KLF6 gene region, we analyzed an Italian population of 338 lung adenocarcinoma cases and 335 controls for the possible role of the reported functional rs3750861 SNP, located 15.6kb from the rs10508266 SNP. The rs3750861 affects expression of KLF6 splicing variants in prostate cancer and we found that its rare allele is associated with reduced lung cancer risk (odds ratio, 0.5; 95% CI, 0.3-0.8). A Norwegian replication series of 265 non small cell lung cancer cases, and 356 controls, however, did not confirm the association. In light of the reported functional involvement of the KLF6 gene in lung cancer and in other cancer types and to the functional nature of the rs3750861 SNP, our results suggest a potential involvement of KLF6 polymorphisms in lung cancer risk, although additional studies in large series are needed to confirm our findings and to elucidate the mechanism by which the KLF6 SNPs influence lung cancer risk.