Increased Gene Expression Involved in Angiogenesis, Metabolism and Cell Proliferation in Acute Myeloid Leukemia and myelodysplastic Syndromes Correlates with Adverse Clinical and Biological Features

Factors such as hypoxia, angiogenesis and increased cell proliferation have been described to the pathogenesis of myeloid neoplasms. In the current study we have analyzed the expression of different genes involved in such pathways and its correlation with clinical and biological parameters in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML).

A total of 83 bone marrow (BM) samples were analysed including: Lower-risk MDS (LR-MDS; defined as IPSS low/Int-1; n=37), higher-risk MDS (HR-MDS; IPSS Int-2/high risk; n=13) and AML (blasts >20%; n=33). All samples were collected at the time of diagnosis. Bone marrow samples from healthy controls were used as control group (n=11). Baseline characteristics are shown in table 1.

Total RNA from BM was treated with DNase, and cDNA was synthesized using a cDNA Sinthesis kit. Gene expression was quantified by qRT-PCR in triplicate using §-actin gene as control. Relative gene expression was determined by 2 (ΔΔCt) method. Cells populations of blasts (CD45+,CD34+,CD117+) were sorted with MoFlo Cell Sorting and separated by positive selection. No differences in gene expression were noticed by sorting as compared to total RNA from whole BM samples. Genes analysed were: vascular endothelial growth factor (VEGF) for angiogenesis, cMYC, macrophage migration inhibitory factor (MIF) and glycogen synthase (GYS) for metabolism and cell-proliferation. Clinical and biological parameters evaluated were: peripheral counts, BM blast percentage, karyotype (good, int and poor by IPSS in MDS and favourable, Int-I, Int-II and adverse by the European Leukemia Net Prognostic System in AML), transfusion dependency, response to intensive chemotherapy (IC) and survival. Statistical significance was determined by t-test, Wilcoxon test and Kaplan Meier with SPSS software (v.16). P values <0.05 were considered significant.

Two groups were considered: group 1, including 20 pts (14 AML, 1 LR-MDS, 5 HR-MDS) displaying over-expression (above p90) in one out of the 4 genes analyzed and group 2, including 63 pts (19 AML, 36 LR-MDS, 8 HR-MDS) with mRNA levels below p90 in all genes. According to WHO, a higher proportion of higher-risk MDS and AML was observed in group 1, p<0,001.

Differences in mRNA levels for each gene and disease are shown in table 2. Patients in group 1 showed higher BM infiltration (p=0,001), lower hemoglobin level (cut-off: 10 g/dL; p=0,003) and higher transfusion dependency as compared to pts in group 2 in univariate analysis. Considering pts receiving IC (n=26; AML=23, HR-MDS=3), resistance occurred in 42.9% vs 31% (p=0,415) of pts included in the group 1 vs group 2, respectively. Interestingly, among AML pts, a trend towards a higher incidence of adverse karyotype was observed in group 1 (88 % vs 44%, p=0,282). Overall, survival was significantly lower among pts in group 1 (47m vs 10m; p=0.008).

No differences in gene expression were noticed by sorting blasts as compared to total RNA from whole BM samples.

Increased expression of VEGF, cMYC, MIF and/or GYS is related to adverse clinical features and a shorter survival in MDS and AML patients, which may establish a link between gen profile involved in hypoxia, angiogenesis and increased cell proliferation and metabolism and clinical parameters in MDS and AML.

No relevant conflicts of interest to declare.