Abstract

Bone marrow microvascular organisation has been shown to play an important role in Acute Myeloid Leukemia (AML). VEGF has four main isoforms produced by alternative splicing: VEGF121, VEGF165, VEGF189 and VEGF206. The VEGF121 protein which lacks the basic amino acids responsible for heparin binding, is the more soluble and potent isoform. The present work aimed at quantitatively measure the shortest transcript for soluble VEGF121 isoform by quantitative RT-PCR in peripheral blood mononuclear cells (PBMC) from AML patients and to evaluate its value as a prognostic marker for response to therapy and survival. We conducted a single institution prospective study in 67 consecutive AML patients at diagnosis. VEGF121 transcript levels in AML PBMC were significantly higher than in normal controls (25.9 copies/1000 copies of β2 microglobulin (β2m) compared to 1.9 copies in normal participants, p<0.001). No relation was found between VEGF121 level and sex, age, white blood cells counts or the dose intensity of aracytine during induction treatment. Both univariate and multivariate analysis of overall survival showed that high levels of VEGF121 transcripts (VEGF121 in AML patients > 5 copies of VEGF121/1000 copies of β2m; 25th centile, this cut-point were designed after systematic searches) were significantly related with a worse prognosis (p<0.0001 for univariate analysis and OR=11.6 [2.76–48.6, p=0.008 for multivariate analysis). Neither sex (p=0.08) nor age (p=0.90) nor WBC (p=0.96) nor caryotype (p=0.29), nor AraC dose intensity (p=0.29) were related with a bad prognosis in this group of patients. Analysing disease free survival, only high levels of VEGF121 transcripts were significantly related to a worse prognosis (p<0.0001, using univariate analysis). Of note, 94% of the patients who relapsed had an initial high level of VEGF121 transcripts. Our findings support the use of this test as a predictive and prognostic tool, helping the clinician to identify patients who should benefit for alternative therapeutic strategies. This test has advantages over ELISA or RIA monitoring cellular or plasma VEGF protein, since it is more specific of this isoform, independant of the number of circulating cells, of binding to α2 macroglobulin and of contaminating sources of VEGF such as platelets which sequester this cytokine. Monitoring of antiangiogenic treatment through QRT-PCR of VEGF121 could therefore be useful in these patients.

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