The Experience on Multiparametric Molecular Diagnostic Approach of Pediatric Acute Lymphoblastic Leukemia (ALL) in Greece.

Abstract

The rate of success in the treatment of pediatric acute lymphoblastic leukemia (ALL) has been increased steadily during the last decades. The five years' event free survival rate is nearly 80% for children with ALL. Attempts to boost cure rates further with the use of hematopoietic stem cell transplantation have improved for some but not all, subtypes of ALL. The best hope for continued progress lies in a better understanding of the pathogenesis, the basis of resistance to chemotherapy, and finally better organized clinical trials. The present study has been based on organizing and exploring new clinical correlations among clinical data obtained from molecular genetic profile, in vitro chemosensitivity and genetic polymorphisms of detoxifying enzymes. During the last 3 years 43 newly diagnosed ALL patients, 27 boys and 16 girls, aged 23 months to 14 years old were included in this study. Bone marrow and/or peripheral blood samples were studied for karyotyping aberrations. The presence of the specific translocations t(12;21), t(9;22), t(4;11) and t(1;19) was investigated using RT-PCR and FISH. Furthermore, FISH was also used for the detection 9p deletions and MLL rearrangements. Immunophenotype of blasts and DNA index were studied by flow cytometry. In vitro chemosensitivity studies were performed by the MTT assay (ELISA).The GSTT1 genetic polymorphism (null genotype) was detected by multiplex PCR and NQ1 genetic polymorphism was detected by PCR -RFLPs. A cytogenetic/molecular result was achieved in 39/43 patients. Structural or numerical aberrations were detected in 7/39 patients. 9/39 patients were positive for the TEL/AML1 (23%) and 3/39 for the BCR/ABL fusion genes. One patient showed only one MLL allele, no patient had MLL rearrangement and 5/19 patients presented 9p deletion. A null GSTT1 genotype was observed in 5/43children (11,62%) and 14/43 patients were heterozygotes for NQ1(32,5%). 8/36 patients presented in vitro chemoresistance and 8/43 patients had DNA index >1 (18,6%).In our series of patients the frequency of t(12;21) does not seem to differ significantly from the literature data. The patients who showed chemoresistance had also unfavorable prognostic markers according to cytogenetic/molecular diagnostic data or clinical characteristics. The number of the patients is low to correlate detoxifying enzymes to toxicity or response during treatment. The multiparametric diagnostic approaches in pediatric ALL seem to be of great importance in diagnosis and tailored therapy leading to high rates of cure. Our center's effort is the optimal characterization of the pediatric ALL profile in Greece by the use of multiparametric diagnostic methods targeting a better outcome.