Association between the polymorphism rs3217927 of CCND2 and the risk of childhood acute lymphoblastic leukemia in a Chinese population

Association of Genetic Variants at the CDKN1B and CCND2 Loci Encoding p27Kip1 and Cyclin D2 Cell Cycle Regulators with Susceptibility and Clinical Course of Chronic Lymphocytic Leukemia

Beyond the essential role of p27Kip1 and cyclin D2 in cell cycle progression, they are also shown to confer an anti-apoptotic function in peripheral blood (PB) lymphocytes. Although the aberrant longevity and expression of p27Kip1 and cyclin D2 in leukemic cells is well documented, the exact mechanisms responsible for this phenomenon have yet to be elucidated. This study was undertaken to determine the associations between polymorphisms in the CDKN1B and CCND2 genes (encoding p27Kip1 and cyclin D2, respectively) and susceptibility to chronic lymphocytic leukemia (CLL), as well as their influence on the expression of both cell cycle regulators in PB leukemic B cells and non-malignant T cells from untreated CLL patients divided according to the genetic determinants studied. Three CDKN1B single-nucleotide polymorphisms (SNPs), rs36228499, rs34330, and rs2066827, and three CCND2 SNPs, rs3217933, rs3217901, and rs3217810, were genotyped using a real-time PCR system. The expression of p27Kip1 and cyclin D2 proteins in both leukemic B cells and non-malignant T cells was determined using flow cytometry. We found that the rs36228499A and rs34330T alleles in CDKN1B and the rs3217810T allele in the CCND2 gene were more frequent in patients and were associated with increased CLL risk. Moreover, we observed that patients possessing the CCND2rs3217901G allele had lower susceptibility to CLL (most pronounced in the AG genotype). We also noticed that the presence of the CDKN1Brs36228499CC, CDKN1Brs34330CC, CDKN1Brs2066827TT, and CCND2rs3217901AG genotypes shortened the time to CLL progression. Statistically significant functional relationships were limited to T cells and assigned to CDKN1B polymorphic variants; carriers of the polymorphisms rs34330CC and rs36228499CC (determining the aggressive course of CLL) expressed a decrease in p27Kip1 and cyclin D2 levels, respectively. We indicate for the first time that genetic variants at the CDKN1B and CCND2 loci may be considered as a potentially low-penetrating risk factor for CLL and determining the clinical outcome.

Cyclin D2 gene variance and expression level in pediatric acute lymphoblastic leukemia

BACKGROUND

Cyclin D2 (CCND2) is a crucial player in cell cycle regulation. CCND2 polymorphisms contribute to cancer predisposition.

OBJECTIVES

To evaluate the association of CCND2 rs3217927 single nucleotide polymorphisms (SNP) and its expression levels with acute lymphoblastic leukemia (ALL) susceptibility in Egyptian children and its potential prognostic role.

METHODS

The 5' nuclease allelic discrimination assay was used to evaluate the frequency of CCND2 rs3217927 SNP in 80 newly diagnosed children with ALL and 80 age- and sex-matched controls. CCND2 relative expression levels were determined by real-time quantitative polymerase chain reaction.

RESULTS

The genotype analysis revealed that the GG genotype and G allele were significantly more prevalent among ALL patients than controls (p ˂ .001). Regression analysis demonstrated that Egyptian children carrying only one G allele had about 31-fold increased risk to develop ALL compared to A allele carriers. CCND2 was overexpressed in ALL patients compared to controls (p < .001). The CCND2 overexpression was associated with the GG genotype and G allele (p < .001). Furthermore, G allele was an independent negative prognostic marker for central nervous system (CNS) involvement (odds ratio [OR] = 4.676; 95% confidence interval [CI]: 1.2-18.6), risk stratification (OR = 38; 95% CI: 7.7-188.2), and chemoresistance (OR = 9.864; 95% CI: 5.6-70.3) in ALL patients.

CONCLUSIONS

G allele of CCND2 rs3217927 SNP might be associated with increased risk for ALL in Egyptian children besides being an independent negative prognostic marker for their risk stratification and therapeutic outcome. CCND2 rs3217927 SNP genotyping might be used to demarcate ALL patients with aggressive disease phenotypes who may be candidate for alternative targeted therapeutic strategies.

Wilms tumor gene single nucleotide polymorphism rs16754 predicts a favorable outcome in children with acute lymphoblastic leukemia

PURPOSE

Wilms tumor gene single nucleotide polymorphism (WT1 SNP) rs16754 has been described as a favorable risk marker in patients with acute myeloid leukemia. Subsequent studies revealed inconsistent results in both adult and pediatric patients. We analyzed its impact on clinical outcome in children with acute lymphoblastic leukemia (ALL) for the first time.

METHODS

WT1 SNP rs16754 of 158 children with ALL treated according to ALL Berlin-Frankfurt-Münster treatment trials from 1990 to 2009 and 43 hematopoietic stem cell donors was analyzed by allelic discrimination. WT1 SNP status was correlated with disease characteristics and clinical outcome comparing SNP (WT1(GG/AG)) and wildtype (WT1(AA)).

RESULTS

At least one minor allele was found in 23.4 % of patients and 34.9 % of donors (P = 0.07). Distribution of patient and disease characteristics was similar between WT1(GG/AG) and WT1(AA). In multivariate analyses, WT1 SNP was an independent good prognostic marker for cumulative incidence of relapse (CIR WT1(AA) vs. WT1(GG/AG) HR = 3.384, P = 0.021) and event-free survival (EFS; event risk WT1(AA) vs. WT1(GG/AG) HR = 2.503, P = 0.036). Univariate subanalyses of patients who underwent an allogeneic hematopoietic stem cell transplantation revealed more significant differences in CIR (P = 0.017), EFS (P = 0.012), and overall survival (OS; P = 0.017). Donor's WT1 SNP status did not affect outcome. We found no correlation between WT1 SNP and WT1 expression level at diagnosis (P = 0.634).

CONCLUSION

WT1 SNP rs16754 predicts improved CIR and EFS. Outcome differences were more prominent in transplanted children. Our findings identify WT1 SNP rs16754 as a favorable risk marker in pediatric ALL which is independent from known risk factors.

Transcription factor and miRNA co-regulatory network reveals shared and specific regulators in the development of B cell and T cell

The maturation process of lymphocyte was related to many blood diseases, such as lymphoma and lymphoid leukemia. Many TFs and miRNAs were separately studied in the development of B and T cells. In this study, we aim to discover the TF and miRNA co-regulation and identify key regulators in the B and T cells maturation. We obtained the candidate genes, miRNAs and TFs for each stage of their maturation, then constructed the TF-miRNA-gene feed-forward loops (FFLs) for each stage by our previous methods. Statistical test for FFLs indicated their enrichment and significance. TF-miRNA co-regulatory networks for each stage were constructed by combining their FFLs. Hub analysis revealed the key regulators in each stage, for example, MYC, STAT5A, PAX5 and miR-17 ~ 92 in the transition of pro-B cells into pre-B cells. We also identified a few common regulators and modules in two stages of B cell maturation (e.g. miR-146a/NFKB1/BCL11A) and two stages of T cell maturation (e.g. miR-20/CCND2/SORL1), as well as some shared regulators in the early stages of both B and T cell development. Our network will help to increase understanding of mature process of B and T cell, as well as the related blood diseases.

Identification of CD34+ and CD34- leukemia-initiating cells in MLL-rearranged human acute lymphoblastic leukemia

Translocation of the mixed-lineage leukemia (MLL) gene with AF4, AF9, or ENL results in acute leukemia with both lymphoid and myeloid involvement. We characterized leukemia-initiating cells (LICs) in primary infant MLL-rearranged leukemia using a xenotransplantation model. In MLL-AF4 patients, CD34(+)CD38(+)CD19(+) and CD34(-)CD19(+) cells initiated leukemia, and in MLL-AF9 patients, CD34(-)CD19(+) cells were LICs. In MLL-ENL patients, either CD34(+) or CD34(-) cells were LICs, depending on the pattern of CD34 expression. In contrast, in patients with these MLL translocations, CD34(+)CD38(-)CD19(-)CD33(-) cells were enriched for normal hematopoietic stem cells (HSCs) with in vivo long-term multilineage hematopoietic repopulation capacity. Although LICs developed leukemic cells with clonal immunoglobulin heavy-chain (IGH) rearrangement in vivo, CD34(+)CD38(-)CD19(-)CD33(-) cells repopulated recipient bone marrow and spleen with B cells, showing broad polyclonal IGH rearrangement and recipient thymus with CD4(+) single positive (SP), CD8(+) SP, and CD4(+)CD8(+) double-positive (DP) T cells. Global gene expression profiling revealed that CD9, CD32, and CD24 were over-represented in MLL-AF4, MLL-AF9, and MLL-ENL LICs compared with normal HSCs. In patient samples, these molecules were expressed in CD34(+)CD38(+) and CD34(-) LICs but not in CD34(+)CD38(-)CD19(-)CD33(-) HSCs. Identification of LICs and LIC-specific molecules in primary human MLL-rearranged acute lymphoblastic leukemia may lead to improved therapeutic strategies for MLL-rearranged leukemia.