MLL-AF9 oncogene expression affects cell growth but not terminal differentiation and is downregulated during monocyte-macrophage maturation in AML-M5 THP-1 cells.

The MLL-AF9 oncogene - one of the most frequent MLL/HRX/ALL-1 rearrangements found in infantile and therapy-related leukaemias - originates from t(9;11)(p22;q23) and is mainly associated with monocytic acute myeloid leukaemia (AML-M5; FAB-classification). Here, we investigated the MLL-AF9 function by means of an antisense phosphorothioate-oligodeoxyribonucleotide (MLL-AF9-PS-ODNas) using the THP-1 AML-M5 cell line carrying t(9;11). Having confirmed that MLL-AF9-PS-ODNas induces strong inhibition of THP-1 cell growth, but only a moderate increase in apoptosis, we found that MLL-AF9-PS-ODNas did not induce morpho-functional terminal differentiation or restore M-CSF-, G-CSF- or GM-CSF-induced differentiation. Moreover, THP-1 cells showed the same phenotype with/without MLL-AF9-PS-ODNas. In THP-1 cells differentiated to mature macrophage-like cells by PMA/TPA or ATRA, MLL-AF9 expression was downregulated. Thus, in the monocytic lineage, MLL-AF9 may be expressed only in early phases and can induce deregulated amplification in both nonmalignant and malignant cells, maintaining the monocytic phenotype without blocking final maturation. Our findings suggest that: (1) as well as directly promoting cell growth, MLL-AF9 may also indirectly determine phenotype; (2) other leukaemogenic mutations associated with MLL-AF9-related leukaemias should be searched for mainly in processes of resistance to apoptosis (where MLL-AF9 may play only a limited role) and differentiation blockage (where MLL-AF9 may play no role).

Targeted inhibition of NMYC by peptide nucleic acid in N-myc amplified human neuroblastoma cells: cell-cycle inhibition with induction of neuronal cell differentiation and apoptosis.

We developed an antisense peptide nucleic acid (PNA) targeted against a unique sequence in the terminus of the 5'-UTR of N-myc, designed for selective inhibition of NMYC in neuroblastoma cells. Fluorescent microscopy showed carrier-free delivery of the PNA to two human neuro-blastoma cell lines: GI-LI-N (N-myc-amplified) and GI-CA-N (N-myc-unamplified). Only in the former, PNA treatment determined 70% cell-viability reduction (at 48 h). In N-myc-amplified GI-LI-N cells, the PNA determined NMYC-translation inhibition (Western blotting), accumulation of cells in G1, induction of differentiation and apoptosis. Selectivity of the PNA was demonstrated by altering three point mutations. These findings should encourage development of a PNA-based tumor-specific agent for neuroblastoma (or other neoplasms) with N-myc overexpression.

Non-radiolabelled PCR consensus primers and automatic sequencing enable rapid identification of tumor-specific V(H) CDR3 in aggressive B-cell malignancies.

Even though the results of current therapy are improved for B-cell acute lymphoblastic leukemia (B-ALL) and Burkitt's lymphoma (BL), prognosis of relapsed mature B-ALL and BL still remain extremely poor. In this study, we investigated the possibility of applying the use of non-radiolabelled PCR consensus primers and automatic sequencing for the rapid identification of the tumor-specific V(H) CDR3 nucleotide sequence, in mature B-ALL and BL. RNA was extracted from four consecutive, unselected samples from BL cases and three consecutive, unselected samples from mature B-ALL cases. The feasibility of the identification of the tumor-specific V(H) CDR3 nucleotide sequence was then assessed by using non-radiolabelled PCR consensus primers with automatic sequencing. The tumor-specific V(H) CDR3 nucleotide sequence was successfully identified for all seven patients (3 mature B-ALL and BL). The time required was substantially lower than that of the other methods previously published, despite the poor quality of some of the samples. The procedure showed rapidity, reliability and reproducibility. The characteristics of the methodology applied widen the possibility of developing anti-idiotypic therapeutic strategies, even in these B-cell malignancies.

Real-time RT-PCR of tyrosine hydroxylase to detect bone marrow involvement in advanced neuroblastoma.

Neuroblastoma (NB) is characterised by the secretion of catecholamines in approximately 95% of patients. Tyrosine hydroxylase is the rate-limiting enzyme in catecholamine biosynthesis pathway. Expression of the tyrosine hydroxylase gene (TH) is regulated in a tissue-specific manner during neonatal development and differentiation, therefore TH mRNA expression is a specific tumour marker for NB. Here we present a real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay using TaqMan technology for detection and quantification of TH mRNA in bone marrow (BM) NB patients. The degree of TH expression was derived from the ratio of the mRNAs of this gene and the reference gene, beta-actin. A ratio greater than 3x10(-2) was considered as positive for TH mRNA presence. Samples were also examined for TH mRNA by first and nested RT-PCR. Seventeen BM samples from 4 patients with disseminated NB (3 stage IV and 1 stage IVs) were evaluated at diagnosis and during treatment. We found a variable degree of TH expression ranging from 0.0344 to 26.3370 in 12/17 positive samples, while no TH mRNA (value lower than 3x10(-2)) was detected in 5/17 samples obtained after consolidation therapy. Our results show a moderate concordance between different qualitative RT-PCR methods and real-time RT-PCR. The real-time RT-PCR results seem to fit better with the natural short-term clinical follow-up of the evaluated patients, with respect to qualitative methods. Real-time TH RT-PCR could therefore be of clinical value for the assessment of a patient's prognosis by monitoring minimal residual disease (MRD).