Analysis of BCL11A gene Variants in Hematological Malignancies.

The B-cell leukemia 11A gene (BCL11A/Evi9/CTIP1) is essential for normal lymphoid development and genetic association studies have shown its potential regulator effect in blood related phenotypes. BCL11A encodes a Krüppel-like zinc-finger protein and functions as a transcriptional repressor through its interaction with several proteins including BCL6. The corresponding mouse gene is a common site of retroviral integration in myeloid leukemia, and may function as a leukemia oncogene. It is down-regulated during hematopoietic cell differentiation and abnormalities involving this gene have been detected in a variety of B-cell malignancies in humans.

We genotyped SNP rs11886868 in the BCL11A gene, which has been previously associated with HbF production, in patients with hematological malignancies from Sardinia to investigate a possible contribution of this gene in determining genetic susceptibility to onco-hematological diseases.

We screened a total of 325 patients with hematological malignancies for rs11886868 SNP at the BCL11A locus using the TaqMan allelic discrimination assay: 51 B-cell Non Hodgkin's lymphoma (NHL), 27 Hodgkin's disease (HD), 42 Chronic Lymphocytic Leukemia (CLL), 52 Multiple Myeloma, 35 Cutaneous T-cell Lymphomas (CTCL), 11 Acute Lymphoblastic Leukemia (ALL), 19 Myelodysplastic Syndromes (MDS), 31 Acute Non Lymphoblastic Leukemia (ANLL), 36 Philadelphia negative Myeloproliferative Disorders (MPD), 21 Chronic Myelogenous Leukemia. Fifty–four DNAs from healthy individuals were used as population controls. Both patients and controls originated from central Sardinia. The frequencies comparisons between controls and cases were performed using chi-square test and Odds Ratio (OR) analysis with Cornfield 95% confidence intervals (CI).

Allele frequencies for BCL11A rs11886868 were 22% for the “C” allele and 78% for the “T” allele. No statistically significant difference was observed between cases and controls. All genotypes were in Hardy-Weinberg equilibrium for both patients and controls groups. The genotype frequencies were 65% (T/T), 26% (C/T) and 9% (C/C) in controls and 53% (T/T), 40.5% (C/T), and 6.5% (C/C) in hematological malignancies. When compared with the genotype frequencies reported for Caucasian and healthy controls from Sardinia no statistically significant difference was observed (p=0.4). However, the C/T genotype was more frequent in cases than controls (41% vs 26%) conferring an increased risk for hematological malignancies with an estimated OR=1,9 (95%CI 1.08-3.6; p=0.03). In detail, statistically significant differences in genotype distribution were observed in CTCL (p< 0.0001), MPD (p=0.0006), NHL (p=0.008), HD (p=0.002) and ALL patients (p=0.02). The C/C genotype was not observed in CTCL and HD patients, while heterozygousity conferred an increased risk of 4.2 (2.3-7.7; p value <0.0001) and 2.6 (1.6-4.7; p value <0.002), respectively. The C/T genotype was also overrepresented in MPD with an estimated OR of 3.2 (1.7-5.8; p value= 0.0001) and NHL with OR of 2.7 (1.5-4.9; p value <0.001). Stratification for clinical and biological parameters showed that among CLLs, the C/C genotype was present in 4/27 (15%) of the CD38-negative patients and in none of the CD38-positive subgroup. By contrast, the homozygousity for the ancestral “T” allele was not observed in Mantle Cell and Marginal Zone Lymphomas.

We found genetic association of BCL11A gene in several blood disorders with the strongest association for Cutaneous T-cell Lymphomas and Myeloproliferative disorders suggesting a possible role of BCL11A in both lymphoid and myeloid lineages. Specific BCL11A genotypes have been associated with different BCL11A expression levels that influence HbF production. We speculate that BCL11A sequence variants may influence expression of different isoforms that may have effect on cell pathways involved in oncogenetic events as well as in globin gene regulation.

This work was supported by Associazione Italiana contro le Leucemie e Linfomi (AIL)

No relevant conflicts of interest to declare.