Daniela de Paula Borges

DNA repair gene expressions are related to bone marrow cellularity in myelodysplastic syndrome

Objective To evaluate the expression of genes related to nuclear excision (ERCC8, XPA and XPC), homologous recombination and non-homologous end-joining (ATM, BRCA1, BRCA2 and LIG4) repair mechanisms, using quantitative PCR methodologies, and it relation with bone marrow cellularity in myelodysplastic syndrome (MDS). Methods and results A total of 51 adult de novo patients with MDS (3 refractory anaemia (RA), 11 refractory anaemia with ringed sideroblasts (RARS), 28 refractory cytopenia with multilineage dysplasia (RCMD), 3 refractory anaemia with excess blasts type I (RAEB-I), 5 refractory anaemia with excess blasts type II (RAEB-II), and 1 chronic myelomonocytic leukaemia (CMML) were evaluated. For karyotype, 16.2% patients were defined as very low prognosis, 59.5% low risk, 8.1% intermediate risk, 5.4% high risk and 10.8% very high risk. For bone marrow cellularity, 17.6%, 17.6% and 64.7% presented as hypocellular, normocellular and hypercellular, respectively. Patients with hypocellular MDS had significantly decreased expression of ATM (p=0.000), BRCA1 (p=0.014), BRCA2 (p=0.003), LIG4 (p=0.004) and ERCC8 (p=0.000) than those with normocellular/hypercellular bone marrow, whereas XPA (p=0.049) and XPC (p=0.000) genes were increased. In patients with hypoplastic MDS, a low expression of ATM (p=0.0268), LIG4 (p=0.0199) and ERCC8 (p=0.0493) was significantly associated with the presence of chromosomal abnormalities. We detected positive correlations between BRCA1 and BRCA2 (r=0.416; p=0.007), ATM and LIG4 (r=0.472; p=0.001), LIG4 and BRCA1 (r=0.333; p=0.026), LIG4 and BRCA2 (r=0.334; p=0.025), ATM and XPA (r=0.377; p=0.008), ATM and XPC (r=0.287; p=0.046), LIG4 and XPC (r=0.371; p=0.007) and XPA and XPC genes (r=0.895; p=0.0000). We also found among all patients evaluated that correlation with LIG4 occurred most often. Conclusions These correlations demonstrate the important intrinsic relations between single and double DNA strand breaks genes in MDS, emphasising that these genes are related to MDS pathogenesis.

Influence of functional polymorphisms in DNA repair genes of myelodysplastic syndrome

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematopoietic stem cell (HSC) malignances characterized by peripheral cytopenias and predisposition to acute myeloid leukemia transformation. Several studies show that the MDS pathogenesis is a complex and heterogeneous process that involves multiple steps through a sequence of genetic lesions in the DNA which lead to functional changes in the cell and the emergence and subsequent evolution of pre-malignant clone. Double strand breaks (DSB) lesions are the most severe type of DNA damage in HSCs, which, if not properly repaired, might contribute to the development of chromosomal abnormalities, which in turn may lead to leukemia development. We assessed the mRNA expression levels of ATM, BRCA1, BRCA2, RAD51, XRCC5, XRCC6 and LIG4 genes in bone marrow samples of 47 MDS patients in order to evaluate the association with functional polymorphisms rs228593, rs4793191, rs9567623, rs1801320, rs3835, rs2267437 and rs1805388, respectively, and try to detect clinical associations. We found that the rs228593, rs2267437 and rs1805388 functional polymorphisms probably alter the level of expression of the ATM, XRCC6 and LIG4 genes, respectively, being important in the maintenance of genomic instability in MDS.

Prognostic importance of Aurora Kinases and mitotic spindle genes transcript levels in Myelodysplastic syndrome

Myelodysplastic syndrome (MDS) are a heterogeneous group of clonal disease characterized by insufficiency of bone marrow, increase of apoptosis and increased risk of acute leukemia progression. Proteins related to the mitotic spindle (AURKA, AURKB, TPX2), to the mitotic checkpoint (MAD2, CDC20) and the regulation of the cell cycle (p21) are directly related to chromosomal stability and tumor development. This study aimed to evaluate the mRNA expression levels of these genes in 101 MDS patients using a real-time PCR methodology. We identified that CDC20 expression are increased in patients with dysmegakaryopoiesis (p=0.024), thrombocytopenia (p=0.000) and high-risk patients (p=0.014, 0.018) MAD2 expression are decreased in patients with 2 or 3 cytopenias (p=0.000) and neutrophil below 800/mm3. TPX2 is also overexpressed in patients presenting dysmegakaryopoiesis (p=0.009). A decrease in AURKA and AURKB expression were observed in patients with altered karyotype (p=0.000), who presented dysplasia in 3 lineages (p=0.000; 0.017) and hemoglobin inferior to 8g/dL (p=0.024). The expression of AURKA, AURKB and MAD2 (p=0.000; 0.001; 0.025) were decreased in patients with hypoplastic MDS, associated with high frequency of chromosomal alterations and high mortality rate. This study reaffirms the importance of aurora kinases and mitotic spindle genes to the pathogenesis and clinical evolution of MDS.

New polymorphisms of Xeroderma Pigmentosum DNA repair genes in myelodysplastic syndrome

The association between Xeroderma Pigmentosum DNA repair genes (XPA rs1800975, XPC rs2228000, XPD rs1799793 and XPF rs1800067) polymorphisms and myelodysplastic syndrome (MDS) have not been reported. To assess the functional role between these polymorphisms and MDS, we evaluated 189 samples stratified in two groups: 95 bone marrow samples from MDS patients and 94 from healthy elderly volunteers used as controls. Genotypes for all polymorphisms were identified in DNA samples in an allelic discrimination experiment by real-time polymerase chain reaction (qPCR). We also studied the mRNA expression of XPA and XPC genes to evaluate if its polymorphisms were functional in 53 RNAm MDS patients by qPCR methodologies. To the rs2228000 polymorphism, the CT and TT polymorphic genotype were associated with increased odds ratio (OR) of more profound cytopenia (hemoglobin and neutrophils count). To the rs1799793 polymorphism, we found that the GG homozygous wild-type genotype was associated with a decreased chance of developing MDS. We observed low expression of XPA in younger patients, in hypoplastic MDS and patients with abnormal karyotype when presented AG or AA polymorphic genotypes. We also found that there was a statistically significant interaction between the presence of micromegakaryocyte on down regulation of XPC regarding the CT heterozygous genotype of the rs1800975 polymorphism. Our results suggest that new functional polymorphisms of Xeroderma Pigmentosum DNA repair genes in MDS are related to its pathogenesis and prognosis.

Role of conventional cytogenetics in sequential karyotype analysis of myelodysplastic syndrome: a patient with der(1;7)(q10;p10)

yelodysplastic syndrome (MDS) constitutes a heterogeneous roup of hematological malignancies characterized by inefective hematopoiesis, presence of cytopenias and high risk f progression to acute myeloid leukemia (AML).1–3 Chroosomal abnormalities can be identified by conventional ytogenetics (G-banding) in up to 50% of MDS patients; this s considered the most important marker of prognosis.3,4 Clonal evolution is defined as an abnormal clone in patient whose karyotype was normal or an additional berration in a patient whose karyotype was abnormal at rst examination.5,6 Different combinations of chromosoal alterations and somatic point mutations contribute to he large clinical–pathological spectrum of MDS.7 Whole-arm