cervical cancer is the second major cause of cancer - related mortality in women worldwide and accounts for 250,000 deaths each year ( 1 ) .
it is well established that the infection with high - risk types of human papillomavirus ( hpv ) plays a central role in the pathogenesis of invasive cervical cancer ( 2 ) .
although many women are infected with high - risk types of hpv , only a subset of infected women develops cervical cancer , suggesting that other cofactors including host genetic factors must be present for the development of malignancy .
chronic inflammation has been shown to be an important risk factor for a variety of epithelial cancers ( 3 ) .
cytokines , as the products of host response to inflammation , play an important role in the defense against viral infections . in cervical cancers ,
a number of previous reports suggested that chronic inflammation is associated with the precancerous intraepithelial lesion and cancer of uterine cervix ( 4 - 6 ) .
the interleukin-1 family of cytokines consists of several members including ineterleukin-1 alpha , interleukin-1 beta and interleukin-1 receptor antagonist .
the genes for these cytokines are clustered within a 430-kb segment on human chromosome 2 .
interleukin-1 beta is a pro - inflammatory cytokine mainly produced by blood monocytes and tissue macrophages and has been implicated in mediating both acute and chronic inflammation ( 7 ) .
recently , a common polymorphic allele of the regulatory region of the il1b gene was found to be associated with increased il-1 production ( 8) . also , the polymorphism in il1b was associated with various human cancers ( 8 - 11 ) . since there were several reports supporting the positive association with increased il1b secretion and cervical cancer risk ( 12 , 13 ) , we hypothesized that an individual with a il1b genotype producing more il1b might have an increased risk of cervical cancer .
the c > t polymorphism in il1b -511 site has been correlated with increased intracellular il1b levels in the previous reports ( 14 ) .
here we report results from a hospital based case - control study examining the association of il1b -511 c > t polymorphisms with the risk of cervical cancer .
case subjects were selected from among cervical cancer patients treated between april 1996 and july 2002 at the seoul national university hospital .
a total of 182 patients with confirmed cervical squamous cell carcinoma consented to participate in the study and provided a blood specimen .
age - matched ( 1:2 ) control subjects were comprised of 364 healthy , unrelated , cancer - free subjects recruited from visitors who attended a comprehensive screening clinic at the same institution and agreed to participate in this study .
all case and control subjects were korean , and the institutional review board of seoul national university hospital approved the protocol used in this study .
all genotyping of 182 cases and 364 control samples was performed by polymerase chain reaction - restriction fragment length polymorphism ( pcr - rflp ) . in brief ,
il1b -511 c > t polymorphism was distinguished by pcr - rflp , using the known primer pairs ( forward primers 5'-gcctgaaccctgcataccgt ; reverse primers 5'gccaatagccctccctgtct-3 ' ) and restriction enzyme avai .
amplification was performed in a volume of 25 l , containing 2.5 l of 10pcr buffer ( 100 mm tris - hci , 15 mm mgcl2 , and 500 mm kcl , ph 8.3 ) , 200 nm each dntp ( roche diagnostics korea , seoul , korea ) , 1 m each primer ( bioneer , daejeon , korea ) , 1 u taq dna polymerase ( roche diagnostics korea , or takara shuzo , otsu , japan ) , and 100 ng of genomic dna .
the thermocycling conditions were as follows : 95 for 5 min ; then 35 cycles of 95 for 30 sec , 58 - 60 for 30 sec , and 72 for 1 min ; then 72 for 10 min .
fifteen microliters of the reaction mixture was treated with 5 u of avai ( ne biolabs , beverly , ma , u.s.a . ) at 37 for 12 hr and subsequently analyzed on 3% agarose ( 2% nusieve [ bio - whittaker molecular applications , rockland , me , u.s.a . ] and 1% agarose ) gel .
hardy - weinberg equilibrium analyses were performed to compare observed and expected genotype frequencies using the chi - square test ( d.f.=1 ) .
allele frequency differences between cases and controls were analyzed using the pearson chi - square test .
cervical cancer risk was estimated by odds ratios ( ors ) and 95% confidence intervals ( cis ) using conditional logistic regression model after adjustment for age .
case subjects were selected from among cervical cancer patients treated between april 1996 and july 2002 at the seoul national university hospital .
a total of 182 patients with confirmed cervical squamous cell carcinoma consented to participate in the study and provided a blood specimen .
age - matched ( 1:2 ) control subjects were comprised of 364 healthy , unrelated , cancer - free subjects recruited from visitors who attended a comprehensive screening clinic at the same institution and agreed to participate in this study .
all case and control subjects were korean , and the institutional review board of seoul national university hospital approved the protocol used in this study .
all genotyping of 182 cases and 364 control samples was performed by polymerase chain reaction - restriction fragment length polymorphism ( pcr - rflp ) . in brief ,
il1b -511 c > t polymorphism was distinguished by pcr - rflp , using the known primer pairs ( forward primers 5'-gcctgaaccctgcataccgt ; reverse primers 5'gccaatagccctccctgtct-3 ' ) and restriction enzyme avai .
amplification was performed in a volume of 25 l , containing 2.5 l of 10pcr buffer ( 100 mm tris - hci , 15 mm mgcl2 , and 500 mm kcl , ph 8.3 ) , 200 nm each dntp ( roche diagnostics korea , seoul , korea ) , 1 m each primer ( bioneer , daejeon , korea ) , 1 u taq dna polymerase ( roche diagnostics korea , or takara shuzo , otsu , japan ) , and 100 ng of genomic dna . the thermocycling conditions were as follows : 95 for 5 min ; then 35 cycles of 95 for 30 sec , 58 - 60 for 30 sec , and 72 for 1 min ; then 72 for 10 min .
fifteen microliters of the reaction mixture was treated with 5 u of avai ( ne biolabs , beverly , ma , u.s.a . ) at 37 for 12 hr and subsequently analyzed on 3% agarose ( 2% nusieve [ bio - whittaker molecular applications , rockland , me , u.s.a . ] and 1% agarose ) gel .
hardy - weinberg equilibrium analyses were performed to compare observed and expected genotype frequencies using the chi - square test ( d.f.=1 ) .
allele frequency differences between cases and controls were analyzed using the pearson chi - square test .
cervical cancer risk was estimated by odds ratios ( ors ) and 95% confidence intervals ( cis ) using conditional logistic regression model after adjustment for age .
in korean population , we observed that the allelic frequencies of the 182 case subjects ( c , 0.42 ; t , 0.58 ) were not significantly different from those of the 364 control subjects ( c , 0.43 ; t , 0.57 ) .
the allelic frequencies of control subjects were not statistically different from those reported for korean populations by other investigators ( 9 ) .
we found that carriers of the t allele had a significantly increased risk of cervical cancer .
the frequency distribution of the different genotypes for the il1b -511 c > t polymorphism is shown in table 1 .
the cc genotype was less frequent among the case subjects than among the control subjects ( 7.7% and 16.8% , respectively ) . with the use of the chi - square test
, we found the significant difference in genotype frequencies between case and control subjects ( p<0.001 ) . using the cc genotype as the reference genotype , we performed logistic regression analysis with adjustment for age variable .
the ct genotype was associated with significantly elevated or of 2.83 ( 95% ci=1.52 to 5.28 , p<0.001 ) .
also , the tt genotype was associated with elevated or of 1.68 ( 95% ci=0.85 to 3.32 , p=0.136 ) .
when we combined ct and tt genotypes together , we found that ct and tt genotypes were associated with or of 2.42 ( 95% ci=1.31 to 4.46 , p<0.005 ) .
here we reported that -511 polymorphism in il1b gene was associated with the risk of cervical cancer .
our findings in this hospital - based case - control study suggest that the carriers of -511 t allele may be at increased risk of developing cervical cancer .
our results support the previous hypothesis that -511 t allele is associated with increased production of il-1 , and that il-1 may play a role as host factors promoting cervical carcinogenesis .
since it is assumed that the host immune system is important in the surveillance of hpv - related cervical neoplasia , cytokines , including il-1 , have been frequently correlated to a risk of cervical cancer .
the level of the il-1 was increased in the cervicovaginal washings of patients with cervical cancer ( 13 ) .
individuals with high and intermediate il-1 secretor phenotypes may be more susceptible to lower grade lesions rather than high grade lesion or cervical carcinoma ( 12 ) . elevated vaginal lavage il-1
these evidences , including the results of this study , suggest that il-1 may be involved in early step of cervical carcinogenesis and that individual difference of il-1 secretion may affect individual susceptibility to cervical cancer progression .
the polymorphism of il1b gene was reported to be associated with various diseases including cancer , but it is most intensively studied in gastric cancer .
el - omar et al . have recently reported that proinflammatory genotypes of the interleukin-1 gene cluster ( il1b -511/-31 and il-1rn*2/*2 ) were associated with increased risk of gastric cancer and its presumptive precursors , gastric atrophy and hypochlorhydria , in white populations from poland and scotland ( 8) .
their results contained data that il1b -511 c > t polymorphism was associated with risk of gastric cancer .
while explaining this , they addressed that there were no differences in binding activity between il1b -511 genotypes , indicating that the effect of il1b -511 polymorphism may be mediated by linkage disequilibrium with the tata box polymorphism .
this may be possible explanation of our finding , no genedosage relationship between -511 genotypes .
in consistence with our data , another recent study reported that il1b -511 ct heterozygous genotype was the main risk of intestinal type gastric cancer in korean population ( 9 ) .
since our results is the first report about the association between il1b -511 c > t polymorphism and the risk of cervical cancer , we could not compare our results with other data .
however , there were several previous reports suggesting the possible association between cervical cancer risk and the polymorphism of other cytokines or cytokine receptors , such as tnf - alpha , interleukin 10 , and interleukin 1 receptor antagonist ( 16 - 21 ) .
therefore , it can be speculated that functional variation of inflammatory cytokine may influence on the individual susceptibility of cervical cancer .
degradation of the p53 gene by oncogenic hpv e6 protein is the most well known carcinogenic mechanism in human cervical cancer .
recent findings indicate an increased p53 mutation load or altered p53 protein function in a number of inflammatory diseases ( 22 ) .
it has been shown that , in rats , intratracheal instillation of il-1 caused hydrogen peroxide production in lung tissue , initiated neutrophil influx and stimulated their release of reactive oxygen species ( 23 ) .
therefore , it can be speculated that reactive free radicals produced by inflammatory cells may cause dna damage in epithelial cells .
inflammatory cytokines have also been shown to induce dna damage and inhibit dna repair in vitro ( 24 ) .
in addition , il-1 has been shown to reduce apoptosis by changing the ratio of bcl-2/bax proteins ( 25 ) .
therefore , a higher production of il-1 may lead to increased p53 mutation load , and the increased level of il-1 may play a role not only in hpv - related cervical carcinogenesis but also in hpv - non - related cervical carcinogenesis . the limitations of the present study are as follows .
second , our sample size is so limited that it has not enough statistical power to exclude the existence of gene - dosage relationship .
third , the various epidemiologic risk factors of cervical cancer , such as smoking , alcohol intake , diet , or sexual behavior , were not included for analysis .
fourth , since our study did not include all clustered polymorphic site of il1b and associated genes , the haplotype analysis could not be done .
so , it would be worthwhile to perform further large - scale population - based study including the analysis of various clustered polymorphisms .
it also should be noted that the risk of cancer caused by foreign pathogen such as virus or bacteria was repeatedly reported by numerous study ( 8 , 26 ) .
therefore , it can be speculated that increased il-1 production may be associated with host genetic factor defending from foreign carcinogenic pathogen . in conclusion , in korean population , il1b -511 cc genotype was significantly associated with decreased risk of cervical cancer .
this relationship supports the idea that polymorphism of inflammatory response genes may be host genetic susceptibility to cervical cancer .
il1b polymorphism should be considered as candidate genetic factor in future study elucidating the genetic risk of cervical cancer .
 cervical cancer is almost invariably associated with infection by human papillomavirus . 
 it is believed that the host genetic factors such as inflammation - induced cytokines may play a role in cervical carcinogenesis . 
 the il1b gene , encoding il-1 cytokine , contains several single nucleotide polymorphisms . 
 one of them which is in the positions -511 ( c - t ) related with promoter region has been associated with increased il-1 production and with increased risk of developing a number of inflammatory diseases and gastric carcinoma . 
 we assessed the association between the il1b -511 polymorphism and cervical cancer risk in a hospital - based case - control study among 546 korean women ( 182 cases ; 364 age - matched controls ) . 
 the allele frequencies of the case subjects ( c , 0.42 ; t , 0.58 ) were not significantly different from those of control subjects ( c , 0.43 ; t , 0.57 ) . 
 control subjects were in hardy - weinberg equilibrium . 
 the carriers with -511 c / t or t / t genotypes were at higher risk of cervical cancer with odds ratio of 2.42 ( 95% ci 1.31 - 4.46 , p<0.005 ) . however , there was no difference of cervical cancer risk between c / t heterologous genotypes and t / t homologous genotypes . 
 in conclusion , in korean population , il1b -511 c / c genotypes were significantly associated with a decreased risk of cervical cancer . 