CD34+ gene expression profiling of individual children with very severe aplastic anemia indicates a pathogenic role of integrin receptors and the proapoptotic death ligand TRAIL.
BACKGROUND Very severe aplastic anemia is characterized by a hypoplastic bone marrow due to destruction of CD34(+) stem cells by autoreactive T cells. Investigation of the pathomechanism by patient-specific gene expression analysis of the attacked stem cells has previously been impractical because of the scarcity of these cells at diagnosis.


METHODS
Employing unbiased RNA amplification, patient-specific gene expression profiling was carried out for CD34(+) cells from patients newly diagnosed with very severe aplastic anemia (n=13), refractory anemia (n=8) and healthy controls (n=10). These data were compared to profiles of myelodysplastic disease (n=55), including refractory anemia (n=18). To identify possible targets of autoimmune attack, presence of autoreactive antibodies was tested in pre-therapeutic sera of patients with very severe aplastic anemia (n=19).


RESULTS
CD34(+) gene expression profiling distinguished between healthy controls, children with aplastic or refractory anemia and clonal disease. Interferon stimulated genes such as the apoptosis inducing death ligand TRAIL were strongly up-regulated in CD34(+) cells of patients with aplastic anemia, in particular in patients responding to immunosuppressive treatment. In contrast, mRNA expression of integrin GPVI and the integrin complexes GPIa/IIa, GPIIb/IIIa, GPIB/GPIX/GPV was significantly down-regulated and corresponding antibodies were detected in 7 of 11 profiled patients and in 11 of 19 aplastic anemia patients. CONCLUSIONS As a potential diagnostic tool, patient-specific gene expression profiling of CD34(+) stem cells made it possible to make the difficult differential diagnosis of most patients with aplastic and refractory anemia. Profiling indicated a prognostic correlation of TRAIL expression and patient benefit from immunosuppressive therapy. Downregulation of integrin expression and concurrent presence of autoreactive anti-integrin-antibodies suggested a previously unrecognized pathological role of integrins in aplastic anemia.
Department of Pediatric Oncology, Hematology and Clinical Immunology, Center for Child and Adolescent Health, Heinrich Heine University, Moorenstr. 5, 40225 Düsseldorf, Germany.
Ute
U
Fischer
Christian
C
Ruckert
Bernd
B
Hubner
Olaf
O
Eckermann
Vera
V
Binder
Tamam
T
Bakchoul
Friedhelm R
FR
Schuster
Sylvia
S
Merk
Hans-Ulrich
HU
Klein
Monika
M
Führer
Martin
M
Dugas
Arndt
A
Borkhardt
D000293:Adolescent; D000741:Anemia, Aplastic / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D000753:Anemia, Refractory / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D018952:Antigens, CD34 / Q000235:genetics*; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D016023:Integrins / Q000235:genetics*; D008297:Male; D046228:Microarray Analysis; D011379:Prognosis; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics*
D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D007166:Immunosuppressive Agents; D016023:Integrins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human