12th Congress of the European Hematology ... - Haematologica
12th Congress of the European Hematology ... - Haematologica
12th Congress of the European Hematology ... - Haematologica
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0877<br />
PAX5/TEL TRANSDUCED PRE-BI CELLS ARE RESISTANT TO TGF-β1 AND MIGRATE<br />
TOWARDS SDF-α<br />
G.F. Fazio, 1 C. Palmi, 2 V. Andrè, 2 A Biondi, 2 A. Rolink, 3 G. Cazzaniga 2<br />
1 Tettamanti Reserach Center, MONZA, Italy; 2 Tettamanti Research Center,<br />
MONZA, Italy; 3 University <strong>of</strong> Basel, BASEL, Switzerland<br />
Background. PAX5 is a transcription factor essential for B cell development.<br />
Recent data indicate that PAX5 aberrancies are present in approximately<br />
30% <strong>of</strong> pediatric B-cell precursor ALL. We previously cloned <strong>the</strong><br />
PAX5/TEL chimeric gene, originated from <strong>the</strong> translocation t(9;12)<br />
(q11;p13) in an ALL patient. PAX5/TEL is likely to be an aberrant transcription<br />
factor, resulting from joining <strong>the</strong> 5’ region <strong>of</strong> PAX5 to <strong>the</strong> 3’<br />
region <strong>of</strong> <strong>the</strong> TEL/ETV6 (Ets-family DNA binding domain) gene. We have<br />
demonstrated a specific nuclear localization <strong>of</strong> <strong>the</strong> chimeric protein in<br />
NIH3T3 by immun<strong>of</strong>luorescence analysis. Moreover, in IL-3 dependent<br />
murine proB Ba/F3 cells, PAX5/TEL recruits mSin3A corepressor, suggesting<br />
its function as transcriptional suppressor. Aim <strong>of</strong> <strong>the</strong> study was<br />
to investigate <strong>the</strong> functions <strong>of</strong> <strong>the</strong> PAX5/TEL chimeric protein in preBI<br />
cells purified from mice fetal liver. Methods. murine PAX5 -/- (B220 + /C-<br />
KIT + /CD19 – ) and wild type (B220 + /C-KIT + /CD19 + ) preBI cells were transduced<br />
with pMIGR-PAX5/TEL-IRES-GFP retroviral construct. Both PAX5-<br />
/- preBI cells and wild type preBI cells were cultured on OP9 stromal cells<br />
in IMDM +2%FCS and IL-7. Results. PAX5/TEL transduced wild type<br />
preBI cells showed down modulation <strong>of</strong> CD19 and slight increase in c-<br />
KIT level expression, while B220 antigen progressively became negative.<br />
PAX5 -/- preBI cells transduced with PAX5/TEL did not show any difference<br />
with <strong>the</strong> parental cells. Transwell assay showed increased migration<br />
index <strong>of</strong> PAX5/TEL wt preBI cells towards SDF-1α chemokine, indicating<br />
a tendency to migrate into bone marrow. RQ-PCR data indicates that<br />
this could be mediated by modulation <strong>of</strong> CXCR4 receptor levels. Without<br />
IL-7, after 24-48 <strong>of</strong> withdrawal, PAX5/TEL wt preBI cells were still<br />
proliferating, while control cells died; although <strong>the</strong>y did not show a complete<br />
cytokine independence, after 72-96 hours <strong>of</strong> starvation, PAX5/TEL<br />
cells were still alive, showing an advantage in cell survival. PAX5/TEL cells<br />
were resistant to TGF-β1 anti-proliferative and apoptotic effects, continuing<br />
to actively proliferate in presence <strong>of</strong> <strong>the</strong> cytokine, with a three-fold<br />
increased growth rate than control cells. Conclusions. PAX5/TEL showed<br />
a role <strong>of</strong> transcriptional suppressor in wt preBI cells, down regulating<br />
CD19 expression; this, in addition to B220 decrease, indicates that<br />
PAX5/TEL can drive <strong>the</strong> regression <strong>of</strong> preBI cell into a previous B cell differentiation<br />
stage, e.g. proB cells. PAX5/TEL do not replace PAX5 functions<br />
in PAX5 -/- cells; indeed it cannot activate PAX5 target genes as CD19,<br />
important for restoring B cell differentiation potential. Both during <strong>the</strong> culture<br />
without <strong>the</strong> IL-7 and during <strong>the</strong> culture in presence <strong>of</strong> TGF-β1,<br />
PAX5/TEL gives proliferation and survival advantage to cells, by <strong>of</strong>fering<br />
<strong>the</strong>m a chance to resist to apoptotic stimuli, thus potentially predisposing<br />
for fur<strong>the</strong>r events leading cell transformation.<br />
12 th <strong>Congress</strong> <strong>of</strong> <strong>the</strong> <strong>European</strong> <strong>Hematology</strong> Association<br />
Thrombosis and bleeding disorders<br />
0878<br />
SOLUBLE P-SELECTIN AND THROMBOSIS RISK OF PATIENTS WITH A PERSISTENT LUPUS<br />
ANTICOAGULANT IN A PROSPECTIVE COHORT STUDY<br />
R. Vormittag, 1 S. Panzer, 2 C. Ay, 3 P. Quehenberger, 4 S. Koder, 3<br />
I. Pabinger3 1 MUW, VIENNA; 2 Clinic for Blood Group Serology, MUW, VIENNA; 3 Internal<br />
Medicine I, MUW, VIENNA; 4 KIMCL, MUW, VIENNA, Austria<br />
Background. Increased soluble P-selectin (sP-selectin) was associated<br />
with an about 10-fold increased risk <strong>of</strong> recurrent venous thromboembolism<br />
in a case/control study. No prospective data on <strong>the</strong> thrombosis risk<br />
<strong>of</strong> LA-patients with elevated sP-selectin levels are currently available.<br />
Aims. Therefore, it was <strong>the</strong> aim <strong>of</strong> our study to assess <strong>the</strong> value <strong>of</strong> elevated<br />
sP-selectin levels as a predictive parameter for thromboembolic events<br />
in LA-patients. Methods. Diagnosis <strong>of</strong> LA was made according to established<br />
criteria. sP-selectin was determined by ELISA (Human soluble P-<br />
Selectin Immunoassay, R&D Systems, USA). Elevated sP-selectin was<br />
defined as a value exceeding <strong>the</strong> 95th percentile <strong>of</strong> control group <strong>of</strong> 129<br />
individuals (cut<strong>of</strong>f=55.1 ng/mL). LA-patients were asked to participate in<br />
<strong>the</strong> study at <strong>the</strong> time <strong>of</strong> diagnosis <strong>of</strong> LA or at <strong>the</strong> time <strong>of</strong> <strong>the</strong>ir first presentation<br />
at <strong>the</strong> outpatient ward if <strong>the</strong> diagnosis <strong>of</strong> LA had already been<br />
established. After patients had given <strong>the</strong>ir informed consent <strong>the</strong>ir medical<br />
history was recorded and <strong>the</strong>y were followed prospectively. Study<br />
endpoints were objectively confirmed arterial or venous thromboembolic<br />
events, death or loss <strong>of</strong> follow-up. The study design was approved by<br />
<strong>the</strong> Ethics Comittee <strong>of</strong> <strong>the</strong> Medical University Vienna. Results. Ninety-seven<br />
LA-patients were included (80 women, 17 men; median age 42, range<br />
17-86 years). Sixty-nine LA-patients had a history <strong>of</strong> thrombotic events<br />
(59 women, 10 men) and 52 <strong>of</strong> <strong>the</strong>se (75%) were under oral anticoagulation<br />
at <strong>the</strong> time <strong>of</strong> study inclusion. Twenty-eight LA-patients (21<br />
women, 7 men) did not have a history <strong>of</strong> thrombosis and nobody in this<br />
group was under oral anticoagulation. sP-selectin levels were significantly<br />
higher in LA patients with a history <strong>of</strong> thrombosis (median 44.1 ng/mL,<br />
range 9.8-130.1) than in those without (median 35.5 ng/mL, range 15.6-<br />
74.1, p=0.008). An odds ratio for past thrombosis <strong>of</strong> 6.5 [95% confidence<br />
interval: 1.4-29.8] was calculated for elevated sP-selectin. During followup<br />
(median observation time: 911 days, range: 80-1973) ten thrombotic<br />
events were observed (four deep vein thromboses, one pulmonary<br />
embolism, three strokes and two myocardial infarctions), <strong>of</strong> <strong>the</strong>se were<br />
seven recurrent events in patients with a history <strong>of</strong> thrombosis and three<br />
primary events. Elevated sP-selectin was present in 25 patients (26%). The<br />
cummulative probability <strong>of</strong> thrombosis was 12.2% after one year and<br />
16.8% after five years in patients with elevated sP-selectin, whereas it was<br />
2.8% after one year and 14.5% after five years for LA-patients with sPselectin<br />
below <strong>the</strong> cut<strong>of</strong>f (Figure 1).<br />
Figure 1. Venous and arterial thrombotic events in LA-patients with (continuous<br />
line) and without (discontinued line) elevated sP-selecti levels.<br />
haematologica/<strong>the</strong> hematology journal | 2007; 92(s1) | 327