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ORIGINAL ARTICLE
Year : 2018  |  Volume : 14  |  Issue : 9  |  Page : 499-504

Association between Krüppel like factor 6 intervening sequence 1-27 G > A and cancer susceptibility: A meta-analysis


1 Department of Urology Surgery, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China
2 Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China

Date of Web Publication29-Jun-2018

Correspondence Address:
Xinquan Gu
Department of Urology Surgery, China-Japan Union Hospital of Jilin University, Changchun, Jilin
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-1482.174553

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 > Abstract 

Background/Objective: It has been reported that Krüppel like factor 6 intervening sequence (KLF6 IVS) 1-27 G > A might be associated with cancer susceptibility. Here, we conducted a meta-analysis to summarize and clarify this association.
Materials and Methods/Main Results: A systematic search of studies on the association between KLF6 IVS 1-27 G > A, and cancer susceptibility was conducted in databases. Odds ratios and 95% confidence intervals were used to pool the effect size. Seven articles were included in our meta-analysis. Overall and in prostate cancer, population-based subgroup overall and Caucasian subgroup overall, no evidence was found for the association between KLF6 IVS 1-27 G > A polymorphism and cancer susceptibility in any genetic model and the results showed stability in sensitivity analyses.
Conclusions: KLF6 IVS 1-27 G > A may not be associated with cancer susceptibility, especially the susceptibility of unselected prostate cancer. However, there was insufficient data to fully confirm the association between KLF6 IVS 1-27 G > A and familial prostate cancer, sporadic prostate cancer, gastric cancer, and cancers from different ethnicity, and the results should be interpreted with caution.

Keywords: Cancer susceptibility, Krüppel like factor 6, meta-analysis, polymorphism, single nucleotide polymorphism


How to cite this article:
Qin J, Meng F, Chu Z, Gu X. Association between Krüppel like factor 6 intervening sequence 1-27 G > A and cancer susceptibility: A meta-analysis. J Can Res Ther 2018;14, Suppl S2:499-504

How to cite this URL:
Qin J, Meng F, Chu Z, Gu X. Association between Krüppel like factor 6 intervening sequence 1-27 G > A and cancer susceptibility: A meta-analysis. J Can Res Ther [serial online] 2018 [cited 2019 Nov 19];14:499-504. Available from: http://www.cancerjournal.net/text.asp?2018/14/9/499/174553


 > Introduction Top


Krüppel like factor 6 (KLF6) belongs to the family of Krüppel like zinc finger transcription factors, which in humans includes Sp1-like factors (Sp1-8) and KLF-like factors (KLF1-16). All KLF members possess a highly conserved zinc finger DNA-binding domain. However, each distinct member differs in its ability to regulate transcription and KLF6 involve in several cancer pathways by regulating its target genes.[1] As a tumor suppressor gene,[2] KLF6 loss has been shown in multiple cancers. Moreover, some mechanisms of KLF6 loss have been found loss of heterozygosity,[3],[4] somatic mutation,[4] decreased expression from promoter hypermethylation or some other reasons,[5],[6] and dysregulated alternative splicing.[7]

KLF6 intervening sequence (IVS) 1-27 G > A (rs3750861), a frequent single nucleotide polymorphism in intron 1 in position 3023 (−27 upstream to exon 2) of KLF6 gene, abolishes the wild-type SF2/ASF and SRp55 binding sites, generates a functional SRp40 binding site and then increases alternative splicing (SV1, SV2, SV3, and IVS△A variant generated from IVS 1-27 G > A) but not decreases levels of wild-type KLF6. However, these increased KLF6 alternative splicing variants' capacity for p21 up-regulation and cell proliferation decrease is weaker than the wild-type KLF6, which in turn antagonize wild-type KLF6's capacity.[7],[8]

Association between KLF6 IVS 1-27 G > A and cancer susceptibility has been studied in several populations. Sample sizes in these studies are relatively small. Therefore, we decided to perform a meta-analysis to estimate it.


 > Materials and Methods Top


Identification of eligible studies

A systematic search in PubMed, Embase, Ovid MEDLINE (R), Cochrane Library, clinicaltrials.gov, Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), WanFangData (one China database), and CQVIP (one China database) databases were carried out by two independent investigators. The following terms were used: “KLF6 or Krüppel like factor 6 or Krüppel like transcription factor 6 or ZF9 or CPBP” and “cancer or tumor or tumor or carcinoma” and “polymorphism or polymorphisms,” without any limitation applied. The last search update was performed on June 11, 2015. References to related studies and reviews were also manually searched for additional studies.

Inclusion and exclusion criteria

Studies selected in this meta-analysis must meet the following inclusion criteria: (1) Evaluation of the association between KLF6 IVS 1-27 G > A polymorphism and cancer susceptibility; (2) case–control study; (3) studies focusing on tissues of human beings, not cell lines; (4) cancer diagnosed; (5) detailed genotype data could be acquired to calculate the odds ratios (ORs) and 95% confidence intervals (95% CIs); exclusion criteria: (1) Duplication of previous publications; (2) comment, review and editorial; (3) study without detailed genotype data. When there were multiple publications from the same population, only the largest study was included.

Study selection was achieved by two investigators independently, according to the inclusion and exclusion criteria by screening the title, abstract and full-text. Any dispute was solved by discussion.

Data extraction

Two investigators extracted data of the eligible studies independently. In the case of a conflict, an agreement was reached by discussion. If the dissent still existed, the third investigator would be involved to adjudicate the disagreements.

The following contents were collected:First author's surname, year of publication, the characteristics of cases and controls, the source of control groups, country of origin, the detective sample, ethnicity, genotyping method, Hardy–Weinberg equilibrium (HWE), the number of cases, and controls for each genotype, cancer type.

Methodological quality assessment

The qualities of included studies were evaluated independently by two investigators according to Newcastle–Ottawa Scale [9] and the most important factor was “age, gender, and country.” Quality scores range from 0 to 9, and higher scores means a better quality of the study. The disagreement was resolved through discussion.

Statistics analysis

Our meta-analysis was conducted according to the PRISMA checklists.[10] HWE was evaluated for each study by Chi-square test in control groups, and P < 0.05 was considered as a significant departure from HWE. OR and 95% CIs were calculated to evaluate the strength of the association between KLF6 IVS 1-27 G > A polymorphism and cancer susceptibility. Pooled ORs were obtained from a combination of single studies by allelic comparison (A vs. G), dominant model (GA + AA vs. GG), recessive model (AA vs. GG + GA), homozygote comparison (AA vs. GG) and heterozygote comparison (GA vs. GG), respectively. The statistical significant level was determined by Z-test with P < 0.05.

Heterogeneity was evaluated by Q-test and I2 index.[11] When Q-test's P < 0.10 and/or I2 index was more than 50%, the random-effects model (DerSimonian and Laird method) was used; otherwise, the fixed-effects model (Mantel and Haenszel method) was conducted.[12] Sensitivity analyses were performed toward each genetic model to evaluate the effect of each study on combined ORs by sequentially excluding each study in total and in any subgroup including more than two studies. Besides, subgroup analyses were stratified by cancer type (prostate cancer, gastric cancer, lung cancer, and cervical cancer), tumor characteristics (Lauren's classification of gastric cancer, familial or sporadic prostate cancer), control type (population-based [PB] and hospital-based [HB]), and ethnicity (Caucasian, Asian, and Mestizo). Potential publication bias was checked by Begg's funnel [13] plots and Egger's test.[14] An asymmetric plot, the P value of Begg's test (PB) < 0.05, and the P value of Egger's test (PE) < 0.05 was considered a significant publication bias. All statistical analyses were performed with Stata 12.0 software (StataCorp, College Station, Texas, USA). A two-tailed P < 0.05 was considered significant except for specified conditions, where a certain P value was declared.


 > Results Top


Characteristics of studies

A total of 173 articles were acquired from databases (PubMed = 34, Embase = 53, Ovid MEDLINE (R) = 22, Cochrane = 1, clinicaltrials.gov = 1, CBM = 2, CNKI = 57, WanFangData = 2, CQVIP = 1). In those 173 articles, 47 were excluded first for duplicate studies and then other 117 articles were excluded for improper title or abstract. Nine left articles were full-text reviewed, and two articles of them were excluded for not case–control studies.[8],[15] Finally, seven articles[7],[16],[17],[18],[19],[20],[21] were included in our meta-analysis. The characteristics of each study were shown in [Table 1]. Different genotyping methods were utilized including sequencing, BsaAI restriction enzyme, pyrosequencing, single strand conformation polymorphism analysis of polymerase chain reaction products (PCR) and PCR – restriction fragment length polymorphism. Blood samples were used for genotyping in all studies except for Marrero-Rodríguez et al.,[21] cases of Cho et al.[18] and Bar-Shira et al.[16] Tissue samples were used in all cases and controls of Marrero-Rodríguez et al.[21] In Cho et al.,[18] normal gastric mucosa specimens were used in all cases, and blood samples were used in all controls. In Bar-Shira et al.,[16] blood samples and tissue samples were used.
Table 1: Characteristics of studies included in the meta-analysis

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All 264 cases in Cho et al.[18] are stomach adenocarcinoma, which consist of 142 intestinal-type (53.8%) and 122 diffuse-type (46.2%) gastric cancers. All 300 cases in Chen et al.[19] are stomach adenocarcinoma, which consist of 84 (28.0%) diffuse-type and 216 (72.0%) intestinal-type gastric cancers. In Spinola et al.,[20] all 338 Italian cases are lung adenocarcinoma and Norwegian cases consist of 135 lung adenocarcinoma, 88 lung squamous cell carcinoma and 42 lung large cell carcinoma. Three histological and colposcopical normal tissues, 20 LGSIL, 16 HGSIL, and 20 carcinomas (16 squamous cell carcinomas and 4 cervical adenocarcinomas) are included in 59 cervical tissue samples of Marrero-Rodríguez et al.[21]

Overall analyses and subgroup analyses

Significantly decreased cancer risk was found in HB subgroup overall in allelic comparison (A vs. G: OR = 0.606, 95% CI = 0.451–0.813, POR= 0.001), dominant model (GA + AA vs. GG: OR = 0.636, 95% CI = 0.458–0.885, POR= 0.007), recessive model (AA vs. GG + GA: OR = 0.414, 95% CI = 0.187–0.916, POR= 0.030), and homozygote comparison (AA vs. GG: OR = 0.418, 95% CI = 0.188–0.925, POR= 0.031). No statistically significant changes of cancer risk was found in other subgroups and overall [Figure 1]. Summary results of each genetic model were listed in [Table 2].
Figure 1: Forest plot with a random effects model for the association between Krüppel like factor 6 intervening sequence 1-27 G > A polymorphism and cancer susceptibility in allelic comparison (A vs. G): Subgroup analyses by cancer type in total. For each study, the estimate of odds ratio and its 95% confidence interval is plotted with a box and a horizontal line. Rhombus: Pooled odds ratio and its 95% confidence interval

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Table 2: Summary of pooled ORs in the meta-analysis

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Sensitivity analyses

Sensitivity analyses were performed in any comparison and any subgroup including more than two studies. When study No. 3 was excluded, statistically different results were obtained in allelic comparison (A vs. G), heterozygote comparison (GA vs. GG) and dominant model (GA + AA vs. GG) of prostate cancer's familial subgroup. When study No. 1.3 was excluded, statistically different results were obtained in allelic comparison (A vs. G), heterozygote comparison (GA vs. GG) and dominant model (GA + AA vs. GG) of prostate cancer's sporadic subgroup. When study No. 6.1 was excluded; the statistically different result was obtained in dominant model (GA + AA vs. GG) of HB subgroup overall [Table 2].

Because of the limited number of included studies, sensitivity analyses could not be performed in gastric cancer (Asian subgroup overall) and its diffuse subgroup and intestinal subgroup, lung cancer, cervical cancer, and Mestizo subgroup overall. In recessive model (AA vs. GG + GA) and homozygote comparison (AA vs. GG) of HB subgroup overall, sensitivity analyses could not be performed either. Because 0 case and 0 control were found with AA genotype in study No. 7 and only two studies were left after No. 7 was excluded.

Other results showed stability in sensitivity analyses.

Publication bias

Begg's funnel plot and Egger's test were used to assess the publication bias. The symmetry of funnel plot, P value of PB and PE were evaluated in every genetic model overall and in prostate cancer subgroup, PB subgroup overall and Caucasian subgroup overall. A funnel plot was roughly symmetrical and neither PB nor PE < 0.05 was found. Hence, no publication bias was identified overall and in prostate cancer subgroup, PB subgroup overall and Caucasian subgroup overall. No Begg's funnel plot or Egger's test were performed for any other subgroup owing to the limited number of included studies.


 > Discussion Top


Overall and in prostate cancer, PB subgroup overall and Caucasian subgroup overall, no evidence was found for the association between KLF6 IVS 1-27 G > A polymorphism and cancer susceptibility in any genetic model and the results showed stability in sensitivity analyses. In prostate cancer's familial subgroup and sporadic subgroup, no association was found in any genetic model, but results in allelic comparison, heterozygote comparison, and dominant model of these two subgroups lacked stability. Meanwhile, significant statistical heterogeneity was identified in these three comparisons but not in other two comparisons, and then we tried hard to find the origin of this heterogeneity but failed. No association was found in gastric cancer (Asian subgroup overall), and its diffuse subgroup and intestinal subgroup either. However sensitivity analyses could not be performed. In HB subgroup overall, we found decreased cancer risk in allelic comparison and no association in heterozygote comparison, and the results showed stability. Decreased cancer risk was also found in the dominant model, recessive model and homozygote comparison in HB subgroup overall, however, the results lacked stability in dominant model, and sensitivity analyses could not be performed in other two. Owing to differences in cancer type and ethnicity of the only three studies included in HB subgroup overall, these results should be interpreted with caution.

Meanwhile, the limitations of this meta-analysis need to be addressed. To date, the numbers of available studies which can be included in this meta-analysis were small. Data for subgroup analyses were scanty. Only four kinds of cancer were included, so that results overall may not be appropriate for all cancers. Related studies published in other languages or unpublished were possibly missed.


 > Conclusions Top


Our results suggested that KLF6 IVS 1-27 G > A may not be associated with cancer susceptibility, especially the susceptibility of unselected prostate cancer. However, there was insufficient data to fully confirm the association between KLF6 IVS 1-27 G > A and familial prostate cancer, sporadic prostate cancer, gastric cancer and cancers from different ethnicity, and the results should be interpreted with caution. Well-designed studies with larger sample size and more subgroups are required to validate the risk identified in the current meta-analysis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
 > References Top

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Bar-Shira A, Matarasso N, Rosner S, Bercovich D, Matzkin H, Orr-Urtreger A. Mutation screening and association study of the candidate prostate cancer susceptibility genes MSR1, PTEN, and KLF6. Prostate 2006;66:1052-60.  Back to cited text no. 16
    
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21.
Marrero-Rodríguez D, Taniguchi-Ponciano K, Jimenez-Vega F, Romero-Morelos P, Mendoza-Rodríguez M, Mantilla A, et al. Krüppel-like factor 5 as potential molecular marker in cervical cancer and the KLF family profile expression. Tumour Biol 2014;35:11399-407.  Back to cited text no. 21
    


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