To the editor:

Killer-cell immunoglobulin-like receptors (KIRs) play a pivotal role in immunosurveillance and reduction of relapse after hematopoietic stem cell transplantation in acute leukemia.1,2  Outside the setting of hematopoietic stem cell transplantation, it was recently reported by Almalte et al that inherited KIR genes might be associated with susceptibility or resistance to childhood acute lymphoblastic leukemia (ALL).3  They determined 6 activating KIRs (KIR2DS1-5 and KIR3DS1) in a cohort of 145 children with B-cell leukemia (B-ALL) and 30 children with T-cell leukemia (T-ALL) and compared it with a healthy control group of 245 children of French-Canadian ethnicity. Children with more activating KIR genes had a lower risk for ALL.3  A subsequent study by Babor et al analyzed the presence of stimulatory KIRs in a similar cohort of children with B-ALL (n = 185) and T-ALL (n = 33).4  In contrast, they did not find a reduction of stimulatory KIRs in childhood ALL patients, although allele frequencies of stimulatory KIRs between the Canadian and the European study did not differ significantly.4 

Given these observations, we determined KIR genotypes of the 17 known KIR genes of 328 pediatric patients (203 male and 125 female) with ALL (86 B-ALL, 179 common ALL, and 63 T-ALL) treated according to the AIEOP-BFM-ALL 2000 protocol. The majority of patients were of European origin with a frequency being in line with Babor’s work.4  The control group consisted of 339 healthy blood donors with a median age of 25 and self-reported Caucasian ethnicity. We used a DNA-based quantitative real-time polymerase chain reaction–based method according to Vilches et al and Alves et al.5,6 

Analyzing prognostic factors often reveals different and potentially coincidental results in different analyses, often because of the fact that no adjustment for multiple testing was done. Therefore, we carefully accounted for this problem in calculating our sample size and in interpreting our analyses. Power calculation was based on a 2-sample test for proportions using proportions for the 6 KIR genes of main interest given in Almalte et al.3  Adjusting for multiple testing of 6 genes, the level of significance was set to .008 to reach a global significance level of .05 (with a power of .8). Therefore, a minimum of 256 patients and 256 controls had to be included, and the end point of all analyses was the presence of ALL (control vs patient). A possible association between occurrence of KIR genes and age, sex, DNA index, or genetics was not observed (data not shown).

Univariate logistic regression did not reveal any significant difference in frequency distribution of KIR alleles and genotypes in children with ALL compared with healthy controls (Table 1). We also analyzed receptor distributions of the 6 activating receptors among the different leukemic risk categories (low, 35%; intermediate, 46%; and high, 19%). No significant difference in receptor combinations could be found between controls and these 3 subgroups (data not shown). Furthermore, KIR genes were assigned to either KIR haplotype A or B. The distribution of these 2 haplotypes among ALL patients and the healthy reference group was 26.8% vs 30.4% for haplotype A and 73.2% vs 69.6% for haplotype B, respectively. These data are in line with published KIR gene frequencies in a Caucasian population.7  We next determined KIR B-content scores for patients and controls and found similar score distributions between the 2 groups. Furthermore, involvement of the central nervous system was independent of activating KIRs, KIR haplotype, and B-content score. An increasing risk for ALL with an increasing number of activating KIR genes was also excluded (P = .173).

Table 1

Influence of activating KIRs, KIR haplotype, KIR B-content score, and inhibiting KIRs on the risk for the development of ALL

FactorALL patientsControlsOR (95% CI)P
KIR2DS1     
 Yes 112 (34.1%) 127 (37.5%)   
 No 216 (65.9%) 212 (62.5%) 1.154 (0.842-1.585) .372 
KIR2DS2     
 Yes 172 (52.4%) 180 (53.1%)   
 No 156 (47.6%) 159 (46.9%) 1.027 (0.758-1.392) .865 
KIR2DS3     
 Yes 107 (32.6%) 93 (27.4%)   
 No 221 (67.4%) 246 (72.6%) 0.781 (0.560-1.088) .143 
KIR2DS4     
 Yes 310 (94.5%) 318 (93.8%)   
 No 18 (5.5%) 21 (6.2%) 0.879 (0.460-1.681) .698 
KIR2DS5     
 Yes 103 (31.4%) 103 (30.4%)   
 No 225 (68.6%) 236 (69.6%) 0.952 (0.686-1.323) .776 
KIR3DS1     
 Yes 122 (37.2%) 126 (37.2%)   
 No 206 (62.8% 213 (62.8%) 0.999 (0.730-1.368) .993 
KIR haplotype     
 A 88 (26.8%) 103 (30.4%)   
 B 240 (73.2%) 236 (69.6%) 0.8401 (0.600-1.176) .3103 
B-content score     
 0 96 (29.3%) 103 (30.4%)   
 1 128 (39.0%) 134 (39.5%)   
 2 81 (24.7%) 79 (23.3%)  .313 
 3 21 (6.4%) 19 (5.6%)   
 4 2 (0.6%) 4 (1.2%)   
KIR2DL1     
 Yes 313 (95.4%) 333 (98.2%)   
 No 15 (4.6%) 6 (1.8%) 24.139 (1.018-6.941) .046 
KIR2DL2     
 Yes 176 (53.7%) 178 (52.5%)   
 No 152 (46.3%) 161 (47.5%) 0.955 (0.703-1.293) .766 
KIR2DL3     
 Yes 287 (87.5%) 303 (89.4%)   
 No 41 (12.5%) 36 (10.6%) 1.201 (0.746-1.934) .448 
KIR2DL4     
 Yes 328 (100%) 339 (100%)   
 No 0 (0%) 0 (0%) 1.033 (0.02-52.241) .987 
KIR2DL5     
 Yes 183 (55.8%) 176 (51.9%)   
 No 145 (44.2%) 163 (48.1%) 0.856 (0.631-1.160) .316 
KIR3DL1     
 Yes 312 (95.1%) 323 (95.2%)   
 No 16 (4.9%) 16 (4.7%) 0.744 (0.363-1.518) .416 
KIR3DL2     
 Yes 328 (100%) 338 (99.7%)   
 No 0 (0%) 1 (0.3%) 0.344 (0.014-8.463) .512 
KIR3DL3     
 Yes 313 (95.4%) 328 (96.8%)   
 No 15 (4.6%) 11 (3.2%) 1.428 (0.645-3.158) .378 
KIR2DP1     
 Yes 320 (97.6%) 337 (99.4%)   
 No 8 (2.4%) 2 (0.59%) 4.213 (0.888-19.988) .070 
KIR2DP1f1     
 Yes 105 (32.01%) 115 (33.9%)   
 No 223 (67.99%) 224 (66.08%) 1.090 (0.788-1.505) .599 
KIR2DP1f2     
 Yes 305 (93%) 324 (95.5%)   
 No 23 (7%) 15 (4.4%) 1.629 (0.833-3.180) .153 
FactorALL patientsControlsOR (95% CI)P
KIR2DS1     
 Yes 112 (34.1%) 127 (37.5%)   
 No 216 (65.9%) 212 (62.5%) 1.154 (0.842-1.585) .372 
KIR2DS2     
 Yes 172 (52.4%) 180 (53.1%)   
 No 156 (47.6%) 159 (46.9%) 1.027 (0.758-1.392) .865 
KIR2DS3     
 Yes 107 (32.6%) 93 (27.4%)   
 No 221 (67.4%) 246 (72.6%) 0.781 (0.560-1.088) .143 
KIR2DS4     
 Yes 310 (94.5%) 318 (93.8%)   
 No 18 (5.5%) 21 (6.2%) 0.879 (0.460-1.681) .698 
KIR2DS5     
 Yes 103 (31.4%) 103 (30.4%)   
 No 225 (68.6%) 236 (69.6%) 0.952 (0.686-1.323) .776 
KIR3DS1     
 Yes 122 (37.2%) 126 (37.2%)   
 No 206 (62.8% 213 (62.8%) 0.999 (0.730-1.368) .993 
KIR haplotype     
 A 88 (26.8%) 103 (30.4%)   
 B 240 (73.2%) 236 (69.6%) 0.8401 (0.600-1.176) .3103 
B-content score     
 0 96 (29.3%) 103 (30.4%)   
 1 128 (39.0%) 134 (39.5%)   
 2 81 (24.7%) 79 (23.3%)  .313 
 3 21 (6.4%) 19 (5.6%)   
 4 2 (0.6%) 4 (1.2%)   
KIR2DL1     
 Yes 313 (95.4%) 333 (98.2%)   
 No 15 (4.6%) 6 (1.8%) 24.139 (1.018-6.941) .046 
KIR2DL2     
 Yes 176 (53.7%) 178 (52.5%)   
 No 152 (46.3%) 161 (47.5%) 0.955 (0.703-1.293) .766 
KIR2DL3     
 Yes 287 (87.5%) 303 (89.4%)   
 No 41 (12.5%) 36 (10.6%) 1.201 (0.746-1.934) .448 
KIR2DL4     
 Yes 328 (100%) 339 (100%)   
 No 0 (0%) 0 (0%) 1.033 (0.02-52.241) .987 
KIR2DL5     
 Yes 183 (55.8%) 176 (51.9%)   
 No 145 (44.2%) 163 (48.1%) 0.856 (0.631-1.160) .316 
KIR3DL1     
 Yes 312 (95.1%) 323 (95.2%)   
 No 16 (4.9%) 16 (4.7%) 0.744 (0.363-1.518) .416 
KIR3DL2     
 Yes 328 (100%) 338 (99.7%)   
 No 0 (0%) 1 (0.3%) 0.344 (0.014-8.463) .512 
KIR3DL3     
 Yes 313 (95.4%) 328 (96.8%)   
 No 15 (4.6%) 11 (3.2%) 1.428 (0.645-3.158) .378 
KIR2DP1     
 Yes 320 (97.6%) 337 (99.4%)   
 No 8 (2.4%) 2 (0.59%) 4.213 (0.888-19.988) .070 
KIR2DP1f1     
 Yes 105 (32.01%) 115 (33.9%)   
 No 223 (67.99%) 224 (66.08%) 1.090 (0.788-1.505) .599 
KIR2DP1f2     
 Yes 305 (93%) 324 (95.5%)   
 No 23 (7%) 15 (4.4%) 1.629 (0.833-3.180) .153 

CI, confidence interval; OR, odds ratio.

Our results are in sharp contrast to the findings of Almalte et al.3  Diversity of KIR gene expression among different ethnic groups has to be taken into account as an explanation for the discrepancy of results. For instance, an increased KIR A/A genotype was found in Hispanic children with ALL, but not in non-Hispanic children.8  Moreover, the possibility of coincidental results in statistical analyses might have to be excluded.

In summary, we did not find a significant difference in KIR gene expression between pediatric patients with ALL and healthy controls, and our results do not support the hypothesis that the number of activating KIR genes confers susceptibility or resistance to pediatric ALL. Further research is necessary to elucidate genetic factors involved in the development of ALL in children.

Acknowledgments: The authors thank Daniela Koendgen, who performed KIR genotyping of the reference population. This work was supported by grants from the Stiftung für krebskranke Kinder Tübingen e.V, the Stefan-Morsch-Stiftung, the Robert Bosch Stiftung, Stuttgart, and the Deutsche Forschungsgemeinschaft (SFB 685) (R.H.). M.M. was supported by a grant from the Fortüne program Tübingen (2021-0-0) and the Jose Carreras Leukaemia Foundation.

Contribution: L.O., M.M., and R.H. coordinated the study, interpreted results, and wrote the manuscript; M.F. performed KIR genotyping of the ALL cohort; M.M. and S. Michaelis introduced the KIR genotyping assay; S. Müller performed statistical analyses; and E.S., M. Schrappe, G.C., M. Stanulla, and M. Schwab provided samples and clinical data.

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Rupert Handgretinger, Children’s Hospital, University of Tuebingen, Hoppe-Seyler-Strasse 1, 72076 Tuebingen, Germany; e-mail: rupert.handgretinger@med.uni-tuebingen.de.

1
Cooley
 
S
Weisdorf
 
DJ
Guethlein
 
LA
, et al. 
Donor selection for natural killer cell receptor genes leads to superior survival after unrelated transplantation for acute myelogenous leukemia.
Blood
2010
, vol. 
116
 
14
(pg. 
2411
-
2419
)
2
Oevermann
 
L
Michaelis
 
SU
Mezger
 
M
, et al. 
KIR B haplotype donors confer a reduced risk for relapse after haploidentical transplantation in children with ALL.
Blood
2014
, vol. 
124
 
17
(pg. 
2744
-
2747
)
3
Almalte
 
Z
Samarani
 
S
Iannello
 
A
, et al. 
Novel associations between activating killer-cell immunoglobulin-like receptor genes and childhood leukemia.
Blood
2011
, vol. 
118
 
5
(pg. 
1323
-
1328
)
4
Babor
 
F
Manser
 
A
Schönberg
 
K
, et al. 
Lack of association between KIR genes and acute lymphoblastic leukemia in children.
Blood
2012
, vol. 
120
 
13
(pg. 
2770
-
2772
)
5
Vilches
 
C
Castaño
 
J
Gómez-Lozano
 
N
Estefanía
 
E
Facilitation of KIR genotyping by a PCR-SSP method that amplifies short DNA fragments.
Tissue Antigens
2007
, vol. 
70
 
5
(pg. 
415
-
422
)
6
Alves
 
LG
Rajalingam
 
R
Canavez
 
F
A novel real-time PCR method for KIR genotyping.
Tissue Antigens
2009
, vol. 
73
 
2
(pg. 
188
-
191
)
7
Bontadini
 
A
Testi
 
M
Cuccia
 
MC
, et al. 
Distribution of killer cell immunoglobulin-like receptors genes in the Italian Caucasian population.
J Transl Med
2006
, vol. 
4
 pg. 
44
 
8
de Smith
 
AJ
Walsh
 
KM
Ladner
 
MB
, et al. 
The role of KIR genes and their cognate HLA class I ligands in childhood acute lymphoblastic leukemia.
Blood
2014
, vol. 
123
 
16
(pg. 
2497
-
2503
)

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