Human leukocyte antigen-drb1 polymorphism in childhood acute lymphoblastic leukemia

Transcription

1 MOLECULAR AND CLINICAL ONCOLOGY 3: , 2015 Humn leukocyte ntigen-drb1 polymorphism in childhood cute lymphoblstic leukemi MERVAT M. EL ANSARY 1, LAMIAA A. MOHAMMED 2, TAMER H. HASSAN 3, AHMED BARAKA 2 nd ALSHYMAA A. AHMED 2 1 Deprtment of Clinicl Pthology, Fculty of Medicine, Ciro University, Ciro 11562; Deprtments of 2 Clinicl Pthology nd 3 Peditrics, Fculty of Medicine, Zgzig University, Zgzig 44111, Egypt Received October 9, 2014; Accepted November 6, 2014 DOI: /mco Abstrct. Similr to utoimmune diseses, there re cler ssocitions between resistnce or susceptibility to cncer nd the clssic humn leukocyte ntigen (HLA) profile of n individul. HLA ssocited susceptibility to childhood cute lymphoblstic leukemi (ALL) my provide clues to leukemogenesis in generl nd to the role of other risk fctors. The present study imed to determine the ssocition between the HLA DRB1 genotype nd susceptibility to ALL in children nd to ssess the prognostic vlue of HLA DRB1 lleles in these ptients. This study included 50 ALL ptients who were consecutively dmitted to the Peditric Oncology Unit of Zgzig University Hospitl nd 50 gender mtched helthy volunteers s control group. The ptients were subjected to full clinicl history, thorough clinicl exmintion nd routine lbortory investigtions. Moleculr HLA DRB1 typing for ptients nd controls using the reverse sequence specific oligonucleotide probe technique ws performed. HLA DRB1*04 llele frequency ws significntly higher in femle ptients compred to tht in femle controls (P=0.03) nd in ptients ged <10 yers compred to those ged 10 yers t the time of dignosis (P=0.01). HLA DRB1*11 llele frequency ws significntly higher in high risk compred to stndrd risk ptients (P=0.01) nd in refrctory ptients compred to those who chieved remission (P=0.02). In conclusion, the HLA DRB1*04 llele ppers to be femle specific susceptibility fctor for the cquisition of childhood ALL nd it my ffect the ge of onset of ALL. In ddition, the HLA DRB1*11 llele my be of prognostic significnce in childhood ALL. However, further lrger studies re required to support the conclusions drwn from this study. Correspondence to: Dr Tmer H. Hssn, Deprtment of Peditrics, Zgzig University, Zgzig University Street, Zgzig 44111, Egypt E mil: dr.tmerhssn@yhoo.com Key words: humn leukocyte ntigen DRB1, cute lymphoblstic leukemi, polymorphism, childhood Introduction Acute lymphoblstic leukemi (ALL) is the most common mlignncy dignosed in children, representing one qurter of ll peditric cncers worldwide (1). Over 40 yers since the first ssocitions between prticulr humn leukocyte ntigen (HLA) profiles nd disese susceptibility were described, the identifiction of lrge numbers of HLA ssocited diseses prllels our improved understnding of the genetic complexity of the HLA system nd its extensive polymorphism. These ssocitions involve mlignnt s well s utoimmune diseses, including the well known ssocition between HLA B27 nd nkylosing spondylitis. Over time, severl hundred diseses hve been reported to occur more frequently in individuls with prticulr HLA genotypes (2). These diseses include brod spectrum of immune medited diseses involving ll mjor orgn systems, certin mlignncies, infectious diseses nd, more recently, dverse rections to prticulr drugs (2). One of the fctors tht my determine whether child develops ALL is how it responds to the cndidte infection. Since immune responses to infection re under the prtil control of HLA genes, n ssocition between n HLA llele nd ALL my provide support for n infectious etiology (3). The biologicl significnce of the ssocition between HLA types nd cute leukemi is emphsized by the fct tht HLA my be involved in disese susceptibility or resistnce. It is importnt to investigte the HLA ssocited susceptibility to childhood ALL, s this my provide clues to leukemogenesis in generl nd to the role of other risk fctors (4). The present study imed to determine the ssocition between the HLA DRB1 genotype nd the susceptibility to ALL in children nd to evlute the prognostic vlue of HLA DRB1 lleles in these ptients. Ptients nd methods Ptients. This study ws performed on 50 ALL ptients who were consecutively dmitted to the Peditric Oncology Unit of Zgzig University Hospitl nd 50 gender mtched helthy volunteers s control group. The ptients were subjected to: i) full clinicl history nd thorough clinicl exmintion; nd ii) routine lbortory

2 426 EL ANSARY et l: HLA DRB1 IN CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIA investigtions, including complete blood count, exmintion of Leishmn stined peripherl blood smer, bone mrrow spirtion with exmintion of Leishmn nd peroxidse stined films nd immunophenotyping by flow cytometry. Moleculr HLA DRB1 typing nd risk clssifiction. The ptients nd controls were subjected to moleculr HLA-DRB1 typing nd the ptients lso underwent risk clssifiction. HLA typing. EDTA nticogulted whole blood smples were collected from ptients nd controls nd processed s follows: i) DNA extrction using the spin column technique (QIAmp DNA Blood Mini kits; Qigen, Hilden, Germny) ws performed ccording to the mnufcturer's guidelines; ii) polymerse chin rection (PCR) mplifiction of the HLA DRB1 gene (exon 2) trget (INNO LiPA HLA DRB1 Amplifiction Plus kit; Fujirebio Europe, Ghent, Belgium) ws performed nd the mplicons were chemiclly dentured to form single strnded DNA. Reverse dot blotting ws performed on nylon membrne (INNO LiPA HLA DRB1 Plus strips, Fujirebio Europe), which contins n rry of immobilized, sequence specific oligonucleotide (SSO) probes. The biotin lbeled mplicons were then bound (hybridized) to these SSO probes, which contin complementry trget sequence nd, thus, were cptured onto the membrne strip; iii) visuliztion of the results ws chieved by incubting with n enzyme conjugte (streptvidin nd lkline phosphtse), which binds to the biotin of the PCR product, followed by the ddition of substrte. The bnds with the cptured PCR product turned blue. Interprettion ws chieved by entering the bnd pttern into computer progrm. Risk clssifiction. The ptients were divided into stndrd nd high risk groups ccording to the Children's Cncer Group (CCG) risk strtifiction (5). Stndrd risk ptients were defined s follows: ge 1 9 yers; initil totl leukocyte count <50,000/mm 3 ; precursor B ALL immunophenotype; nd no centrl nervous system (CNS) mnifesttions or testiculr infiltrtion. High risk ptients exhibited ny of the following t dignosis: ge 10 yers; initil totl leukocyte count 50,000/mm 3 ; T ALL immunophenotype; CNS mnifesttions; nd overt testiculr leukemi. Children with mture B ALL were considered to be mong the high risk ptients nd were treted seprtely using the LMB 96 protocol, which is n interntionl protocol conducted by three coopertive groups (Interntionl Society for Peditric Oncology, CCG nd United Kingdom Children's Cncer Study Group) nd (6). Sttisticl nlysis. The dt were checked, entered nd nlyzed using Epi Info 6 sttisticl softwre (Centers for Disese Control nd Prevention, Atlnt, GA, USA). The results re expressed s men ± stndrd devition for quntittive vribles nd s number nd percentge for qulittive vribles. The differences in the frequencies of HLA DRB1 lleles mong the investigted groups were nlyzed using the Chi squre test with Ytes' correction nd the two tiled Fisher's exct test for results 5. Ech llele frequency in the ptients ws compred ginst the sme llele in controls. The odds rtios (ORs) with 95% confidence intervls were clculted. P 0.05 ws considered to indicte sttisticlly significnt differences. Tble I. HLA-DRB1 llele frequencies in ptients nd controls. HLA- Ptient Control lleles (n=50) (n=50) OR (95% CI) P-vlue *01 2 (4.0) 5 (10.0) 0.38 ( ) 0.43 *03 10 (20.0) 10 (20.0) 1 ( ) 0.80 *04 21 (42.0) 12 (24.0) 2.29 ( ) 0.13 *07 13 (26.0) 7 (14.0) 2.16 ( ) 0.21 *08 2 (4.0) 3 (6.0) 0.65 ( ) 0.99 *09 0 (0.0) 3 (6.0) 0 ( ) 0.24 *10 4 (8.0) 4 (8.0) 1 ( ) 1.00 *11 15 (30.0) 14 (28.0) 1.1 ( ) 1.00 *12 0 (0.0) 3 (6.0) 0 ( ) 0.24 *13 14 (28.0) 19 (38.0) 0.63 ( ) 0.39 *14 3 (6.0) 4 ( 8.0) 0.73 ( ) 0.99 *15 6 (12.0) 9 (18.0) 0.62 ( ) 0.57 *16 2 (4.0) 2 (4.0) 1 ( ) 1.00 A totl of 8 ptients nd 5 controls were homozygous. HLA, humn leukocyte ntigen; OR, odds rtio; CI, confidence intervl. Ethics. This study ws conducted in ccordnce with the ethicl stndrds of the Helsinki Declrtion of 1964, s revised in 2000 (7) nd ws pproved by the Institutionl Review Bord of the Fculty of Medicine, Zgzig University. Informed consent ws obtined from ll the study prticipnts. Results Ptient chrcteristics. The men ge of the ptients t dignosis ws 4.9±3.3 yers (rnge, 2 13 yers). The ptients included 32 mles nd 18 femles, with mle:femle rtio of 1.8:1. The most frequent clinicl mnifesttion ws pllor (88%), followed by fever (74%), heptosplenomegly (72%), lymphdenopthy (54%), purpur (40%) nd bone pin (30%). CNS ws involved in only 4% of the ptients. A totl of 72% of the ptients hd totl leukocyte count <50,000/mm 3 nd 28% hd totl leukocyte count 50,000/mm 3. A totl of 88% of the ptients hd precursor B ALL, 10% hd T ALL nd 2% hd mture B ALL. Allele frequency determintion. HLA DRB1*04, *11, *13, *07 nd *03 were the most frequent lleles in the ptients (42, 30, 28, 26 nd 20%, respectively). HLA DRB1*09 nd HLA DRB1*12 lleles were not detected in ny ptients. HLA DRB1*13, *11, *04, *03 nd *15 were the most frequent lleles in the controls (38, 28, 24, 20 nd 18%, respectively). There ws no significnt difference between ptients nd controls s regrds the frequencies of different HLA DRB1 lleles (P>0.05) (Tble I). A totl of 8 ptients were homozygous for HLA DRB1, nmely 6 mles (homozygous HLA DRB1*03, *04, *04, *07, *13 nd *14) nd 2 femles (homozygous HLA DRB1*11 nd *13); in ddition, 5 controls were homozygous for HLA DRB1, nmely 2 mles (HLA DRB1*04 nd *11) nd 3 femles (HLA DRB1*03, *04 nd *04).

3 MOLECULAR AND CLINICAL ONCOLOGY 3: , Tble II. HLA DRB1 llele frequencies in femle ptients nd femle controls. Femle Femle HLA ptients, controls, lleles (n=18) (n=18) OR (95% CI) P-vlue *01 0 (0.0) 1 (5.6) *03 2 (11.1) 3 (16.7) 0.63 ( ) 0.99 *04 10 (55.6) 3 (16.7) 6.25 ( ) 0.03 *07 6 (33.3) 3 (16.7) 2.5 ( ) 0.44 *08 1 (5.6) 1 (5.6) 1 ( ) 1.00 *09 0 (0.0) 1 (5.6) *10 0 (0.0) 1 (5.6) *11 6 (33.3) 4 (22.2) 1.75 ( ) 0.70 *12 0 (0.0) 2 (11.1) *13 5 (27.8) 7 (38.9) 0.6 ( ) 0.71 *14 0 (0.0) 2 (11.1) *15 3 (16.7) 4 (22.2) 0.7 ( ) 0.99 *16 1 (5.6) 1 (5.6) 1 ( ) 1.00 Sttisticlly significnt. HLA, humn leukocyte ntigen; OR, odds rtio; CI, confidence intervl. Tble III. HLA DRB1 llele frequencies in reltion to ptient ge t dignosis. Ptient ge HLA <10 yrs, 10 yrs, lleles (n=42) (n=8) OR (95% CI) P-vlue *01 2 (4.8) 0 (0.0) *03 6 (14.3) 4 (50) 0.16 ( ) 0.04 *04 21 (50.0) 0 (0.0) *07 10 (23.8) 3 (37.5) 0.52 ( ) 0.66 *08 1 (2.3) 1 (12.5) 0.17 (0 3.05) 1.00 *10 4 (9.5) 0 (0.0) *11 12 (28.6) 3 (37.5) 0.66 ( ) 0.68 *13 12 (28.6) 2 (25) 1.2 ( ) 1.00 *14 3 (7.1) 0 (0.0) *15 5 (11.9) 1 (12.5) 0.94 ( ) 0.65 *16 1 (2.3) 1 (12.5) 0.17 (0 3.05) 1.00 Sttisticlly significnt. HLA, humn leukocyte ntigen; OR, odds rtio; CI, confidence intervl. Tble IV. HLA DRB1 llele frequencies in reltion to risk. There ws no significnt difference between mle ptients nd mle controls s regrds the frequencies of different HLA DRB1 lleles (P>0.05). However, the HLA DRB1*04 llele frequency ws significntly higher mong femle ptients compred to tht mong femle controls (55.6 vs. 16.7%, respectively; P=0.03) (Tble II). Bsed on the CCG risk clssifiction, the ALL ptients were divided regrding their ge t dignosis into two groups, nmely those ged <10 nd those ged 10 yers. The HLA DBR1*04 llele frequency ws significntly higher mong ptients ged <10 yers compred to those ged 10 yers t dignosis (50.0 vs. 0.0%; P=0.01) (Tble III). There ws no significnt difference mong ptients with different immunophenotypes s regrds the frequencies of different HLA DRB1 lleles (P>0.05). The HLA DRB1*11 llele frequency ws significntly higher in high risk compred to stndrd risk ptients (50.0 vs. 14.3%; P=0.01) (Tble IV). Of the 50 included ptients, 10 were referred to other hospitls prior to tretment initition nd 10 succumbed to the disese; 1 ptient with mture B ALL succumbed to cute renl filure prior to tretment initition, 7 ptients died during tretment due to chemotherpy relted toxicity nd infections nd 2 ptients died following disese relpse. Following exclusion of the 10 referred ptients nd the 1 ptient who died prior to tretment initition, the remining 39 ptients were divided into the remission (n=34) nd refrctory (n=5) groups. The HLA DR1*11 llele frequency ws significntly higher mong refrctory ptients compred to those who chieved remission (80.0 vs. 23.5%; P=0.02) (Tble V). Following exclusion of the 10 referred ptients nd the 8 ptients who died during the study due to cuses other Risk HLA Stndrd, High, lleles (n=28) (n=22) OR (95% CI) P-vlue *01 1 (3.6) 1 (4.5) 0.78 ( ) 1.00 *03 5 (17.9) 5 (22.7) 0.74 ( ) 0.73 *04 13 (46.4) 8 (36.4) 1.52 ( ) 0.67 *07 7 (25.0) 6 (27.3) 0.89 ( ) 0.88 *08 1 (3.6) 1 (4.5) 0.78 ( ) 1.00 *10 3 (10.7) 1 (4.5) 2.52 ( ) 0.62 *11 4 (14.3) 11 (50.0) 0.17 ( ) 0.01 *13 10 (35.7) 4 (18.2) 2.5 ( ) 0.29 *14 3 (10.7) 0 (0.0) *15 3 (10.7) 3 (13.6) 0.76 ( ) 1.00 *16 1 (3.6) 1 (4.5) 0.78 ( ) 1.00 Sttisticlly significnt. HLA, humn leukocyte ntigen; OR, odds rtio; CI, confidence intervl. thn relpse, the remining 32 ptients were divided into the relpsed (n=4) nd non relpsed groups (n=28). There ws no significnt difference between the two groups s regrds the frequencies of different HLA DRB1 lleles (P>0.05). Following exclusion of the 10 referred ptients, the remining 40 ptients were divided into the survivors (n=30) nd those who succumbed to the disese (n=10). There ws no significnt difference between the two groups s regrds the frequencies of different HLA DRB1 lleles (P>0.05).

4 428 EL ANSARY et l: HLA DRB1 IN CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIA Tble V. HLA DRB1 llele frequencies in reltion to induction of remission. Remission Refrctory HLA- group, group, lleles (n=34) (n=5) OR (95% CI) P-vlue *01 1 (2.9) 1 (20.0) 0.12 ( ) 0.24 *03 6 (17.6) 2 (40.0) 0.32 (00 2.3) 0.56 *04 15 (44.1) 0 (0.0) *07 9 (26.4) 1 (20.0) 1.4 ( ) 1.00 *08 1 (2.9) 0 (0.0) *10 3 (8.8) 1 (20.0) 0.38 ( ) 0.99 *11 8 (23.5) 4 (80.0) 0.07 ( ) 0.02 *13 10 (29.4) 1 (20.0) 1.6 ( ) 1.00 *14 2 (5.8) 0 (0.0) *15 6 (17.6) 0 (0.0) Sttisticlly significnt. HLA, humn leukocyte ntigen; OR, odds rtio; CI, confidence intervl. Discussion Genetic nd environmentl fctors ply n interctive role in the development of childhood ALL. Since the demonstrtion of mjor histocomptibility complex effect on mouse leukemi in 1964, n HLA ssocition hs been considered s possible genetic risk fctor (8). In the present study, there ws no significnt difference between ptients nd controls s regrds the frequencies of different HLA DRB1 lleles (P>0.05). In ddition, there ws no significnt difference between mle ptients nd mle controls s regrds the frequencies of different HLA DRB1 lleles (P>0.05). However, the HLA DRB1*04 llele frequency ws significntly higher mong femle ptients compred to femle controls (55.6 vs. 16.7%; P=0.03), indicting tht HLA DRB1*4 is femle specific susceptibility llele for childhood ALL. The puttive role of the HLA clss II DR ntigen in ALL risk ws first suggested in the lte 1970s by de Moerloose et l (9), who demonstrted n ssocition with DR7. Additionl evidence specificlly regrding childhood ALL ws vilble shortly fter the studies conducted by von Fliedner et l, one of which confirmed the DR7 ssocition (10), wheres the other reveled higher shring of DR ntigens mong prents of children with leukemi thn expected (11). By contrst, Dork et l (8) reported tht the frequency of the HLA DRB1*04 llele ws higher (P=0.0005, OR=2.9), wheres the frequency of the HLA DRB1*13 llele ws lower in mle ptients. In 2002, study tht ws performed on n Indin popultion demonstrted tht the HLA DRB1*04 nd HLA DRB1*13 lleles re susceptible nd protective lleles, respectively, in ALL ptients (12). In their study on 106 Irnin ptients with ALL, Yri et l (13) concluded tht HLA DRB1*13, which exhibited decrese mong the ptients, ppered to be protective ginst ALL, wheres HLA DRB1*04, which ws modertely incresed mong the ptients, ws considered susceptibility llele for childhood ALL. A significnt increse in the frequency of the HLA DRB1*04 llele in the overll nd mle ALL ptients ws reported in Turkish study (4). In ddition, significntly lower frequency of the HLA DRB1*13 llele ws observed mong femle ptients compred to femle controls (4). The ssocition between HLA clss II lleles nd ALL ws investigted in 20 Irnin ptients with leukemi (14). The results reveled significnt increse in the frequency of the HLA DRB1*04 llele in ALL ptients compred to tht in controls. DRB1*15, risk llele for multiple sclerosis, hs lso been implicted in the susceptibility to childhood ALL. At lest two studies hve reported such n ssocition; one ws conducted in Chinese popultion comprising 162 childhood ALL cses nd 1,000 controls (15), wheres the other ws conducted in UK popultion, investigted the effects by gender nd observed n ssocition only in femles, which is consistent with femle specific effect of the llele DRB1*15:01, lso observed in multiple sclerosis (16). The discrepncy between the results of different studies, including our results, my be ttributed to the differences in popultion rce nd geogrphicl distribution. Studies investigting the pthogenic effects of gene should include fctors such s the differences in the frequency distributions of the gene between the ptient nd the control groups (the stronger the effect of gene, the more significnt the differences in frequency distribution) nd erly or lte ge t disese onset in gene crriers (the stronger the effects, the erlier the onset) (17). In our study, the HLA DBR1*04 llele frequency ws significntly higher in ptients ged <10 yers compred to those ged 10 yers t the time of dignosis (50.0 vs. 0.0%; P=0.01). From these results, it ws suggested tht the HLA DRB1 llele my ffect the ge t onset in ALL. To the best of our knowledge, there re no studies in the literture ssociting the HLA DRB1 llele frequencies with the ge t onset in ALL. However, this llele hs been investigted in reltion to other cncers in dults (17,18). The men ge of ptients with colorectl cncer who crry the HLA DQB1*02 llele ws found to be lower compred to tht of subjects without the llele (P<0.05), suggesting tht this llele is ssocited with colorectl cncer susceptibility (17). In nother study, the frequency of HLA lleles in 50 chronic myeloid leukemi ptients in reltion to ge t onset ws investigted; the uthors concluded tht the frequency of the HLA DRB1*07 (P=0.03) nd DQA1*0201 (P=0.03) lleles ws higher mong ptients ged <35 yers (18). Our results demonstrted tht the HLA DRB1*11 llele frequency ws significntly higher mong high risk compred to stndrd risk ptients (50.0 vs. 14.3%; P=0.01) nd in refrctory ptients compred to those who chieved remission (80.0 vs. 23.5%; P=0.02). These results indicted tht the HLA DRB1*11 llele my be predictor for prognosis nd tretment outcome in children with ALL. However, there ws no significnt difference between the relpsed nd non relpsed groups nd between survivors nd those who succumbed to the disese s regrds the frequencies of different HLA DRB1 lleles (P>0.05).

5 MOLECULAR AND CLINICAL ONCOLOGY 3: , The significnce of the HLA lleles s prognostic indictors in childhood leukemi hs been investigted in limited number of studies. Csper et l (19) reported n incresed incidence of relpse ssocited with HLA DR5, with higher rte of disese free remission ssocited with DR7; however, Tkeuchi et l (20) nd Luten et l (21) did not identify n ssocition with outcome in childhood leukemi. In conclusion, the HLA DRB1*04 llele ppers to be femle specific susceptibility fctor for the development of childhood ALL nd it my ffect the ge t onset for ALL. In ddition, the HLA DRB1*11 llele my be of prognostic vlue in childhood ALL. However, further lrger studies re required to support our findings. References 1. Riber JM nd Oriol A: Acute lymphoblstic leukemi in dolescents nd young dults. Hemtol Oncol Clin North Am 23: , Howell WM: HLA nd disese: guilt by ssocition. Int J Immunogenet 41: 1 12, Derden SP, Tylor GM, Gokhle DA, et l: Moleculr nlysis of HLA DQB1 lleles in childhood common cute lymphoblstic leukemi. Br J Cncer 73: , Ozdilli K, Oguz FS, Ank S, Kekik C, Crin M nd Gedikoglu G: The frequency of HLA clss I nd II lleles in Turkish childhood cute leukemi ptients. J Int Med Res 38: , Pui CH, Crroll WL, Meshinchi S nd Arceci RJ: Biology, risk strtifiction, nd therpy of peditric cute leukemis: n updte. J Clin Oncol 29: , Ciro MS, Gerrrd M nd Ptte C: A new protocol for tretment of mture B cell lymphom/leukemi (BCLL): FAB LMB 96, SFOP LMB 96/CCG 5961/UKCCSG NHL 9600 interntionl coopertive study. Med Peditr Oncol 29: 357A, Christie B: Doctors revise declrtion of Helsinki. BMJ 321: 913, Dork MT, Lwson T, Mchull HK, Drke C, Mills KI nd Burnett AK: Unrvelling n HLA DR ssocition in childhood cute lymphoblstic leukemi. Blood 94: , de Moerloose P, Chrdonnens X, Vsslli P nd Jennet M: HL A D ntigens from B lymphocytes nd susceptibility to certin diseses. Schweiz Med Wochenschr 107: 1461, 1977 (In French). 10. von Fliedner VE, Sultn Khn Z nd Jennet M: HLA DRw ntigens ssocited with cute leukemi. Tissue Antigens 16: , von Fliedner VE, Meric H, Jennet M, et l: Evidence for HLA linked susceptibility fctors in childhood leukemi. Hum Immunol 8: , Jini R, Kur G nd Mehr NK: Heterogeneity of HLA DRB1*04 nd its ssocited hplotypes in the North Indin popultion. Hum Immunol 63: 24 29, Yri F, Sobhni M, Sbghi F, Zmn Vziri M, Bgheri N nd Tlebin A: Frequencies of HLA DRB1 in Irnin norml popultion nd in ptients with cute lymphoblstic leukemi. Arch Med Res 39: , Atsh beik SM, Akbri MT, Syd A, et l: The ssocition of HLA DRB1 gene polymorphisms with cute lymphoblstic leukemi (ALL) in Irnin ptients. J Biol Tody's World 2: , Wng XJ, Ai XF, Sun HY, et l: Reltion of HLA DRB1*15 with pthogensis in 162 childhood cses of cute lymphoblstic leukemi. Chin Assoc Pthophysiol 17: , 2009 (In Chinese). 16. Morrison BA, Ucisik Akky E, Flores H, Alez C, Gorodezky C nd Dork MT: Multiple sclerosis risk mrkers in HLA DRA, HLA C, nd IFNG genes re ssocited with sex specific childhood leukemi risk. Autoimmunity 43: , Tong F, Yu W nd Liu H: Efficient ssocition nlysis between colorectl cncer nd llelic polymorphisms of HLA DQB1 by comprison of ge of onset. Oncol Lett 3: , Amirzrgr AA, Khosrvi F, Dint SS, et l: Assocition of HLA clss II llele nd hplotype frequencies with chronic myelogenous leukemi nd ge t onset of the disese. Pthol Oncol Res 13: 47 51, Csper JT, Mrrri M, Piskowski V, Luer SJ nd Duquesnoy RJ: Assocition between HLA D region ntigens nd disese free survivl in childhood non T, non B cute lymphocytic leukemi. Blood 60: , Tkeuchi S, Tkeuchi N, Tsukski K, et l: Genetic polymorphisms in the tumor necrosis fctor locus in childhood cute lymphoblstic leukemi. Br J Hemtol 119: , Luten M, Mtthis T, Stnull M, Beger C, Welte K nd Schrppe M: Assocition of initil response to prednisone tretment in childhood cute lymphoblstic leukemi nd polymorphisms within the tumor necrosis fctor nd interleukin 10 genes. Leukemi 16: , 2002.