HL60 cell line was also grown in the presence of differentiation factors all trans retinoic acid at 10 7 M and 1,25 dihydroxyvitamin at 10 8 M, over a period of 7 or 11 days of culture, respectively. When indicated HL60 cells were also treated with Z Val Ala DL Asp fluoromethylketone 25 uM nothing alone or in combination with ATRA. The human teratocarcinoma cell line, utilized as a positive control of HOXB1 expression, was grown in DMEM medium, 10% FBS supplemented and induced to differentiate by ATRA 10 7 M over a period of 9 days. Cryopreserved cell samples obtained from a group of twelve patients with acute myeloid leukemia were stud ied and subclassified according to the FAB nomenclature and cytogenetic analysis. The original samples contained a range of 20 to 500��106 cells and 80% of blastic infiltration.

Leukocytes were isolated by Ficoll Hypaque density centrifugation. Normal granulocytes, monocytes/macrophages, lymphocytes and erythroblasts were obtained from peripheral blood of healthy donors. CD34 progenitor cells were purified from peripheral blood as reported. Retroviral gene transduction The HOXB1 cDNA encompassing its complete coding sequence was cloned into the retroviral vector LXSN as LB1SN. the LXSN empty vector was always used as an internal control. AML193, U937, NB4 and HL60 cell lines were transduced with the LXSN empty vector and with LB1SN helper free virus containing superna tants. Cells were treated twice for 4 hr with undiluted packaging cell supernatants in presence of 8 ug/ml of polybrene. Infected target cells were grown for 48 hr and then selected with G418.

As the ectopic expression of HOXB1 in AML193, U937 and NB4 cell lines was apparently lost in the first days after selection, the sub sequent functional studies were performed on the sole HL60 cell line. RNA analysis HOXB1 expression was evaluated either by traditional or Real time RT PCR. For the traditional technique rela tive quantifications were done by densitometric analysis after GAPDH samples normalization. When indicated PCR products were verified by southern blotting using an internal probe. Negative samples were confirmed after 40 amplification cycles. Real time RT PCR was performed by the TaqMan technology, using the ABI PRISM 7700 DNA Sequence Detection System as reported. Commercial ready to use primers/probe mixes are listed HOXB1 Hs00157973 m1. early growth re sponse 1 Hs00152928 m1. fatty acid synthase Hs00188012 m1. mouse double minute 2 homolog Hs00234760 m1. programmed cell death 10 Hs00200578 m1. caspase2 Hs00154240 m1. non metastatic Batimastat cells 1 protein Hs00264824 m1. secreted protein acidic and rich in cysteine Hs00234160 m1, Glyceraldehyde 3 phosphate dehydrogenase H s4326317E.