Retinoic Acid (RA) treatment induces disease remission of Acute Promyelocytic Leukaemia (APL) patients by triggering terminal differentiation of neoplastic cells. RA-sensitivity in APL is mediated by its oncogenic protein, which results from the recombination of the PML and the RA receptor α (RARα) genes (PML/RARα fusion protein). Ectopic expression of PML/RARα into haemopoietic cell lines results in increased response to RA-induced differentiation. By structure-function analysis of PML/RARα-mediated RA-differentiation, we demonstrated that fusion of PML and RARα sequences and integrity of the PML dimerization domain and of the RARα DNA binding region are required for the effect of PML/RARα on RA-differentiation. Indeed, direct fusion of the PML dimerization domain to the N- or C-terminal extremities of RARα retained full biological activity. All the biologically active PML/RARα mutants formed high molecular weight complexes in vivo . Functional analysis of mutations within the PML dimerization domain revealed that the capacity to form PML/RARα homodimers, but not PML/RARα-PML heterodimers, correlated with the RA-response. These results suggest that targeting of RARα sequences by the PML dimerization domain and formation of nuclear PML/RARα homodimeric complexes are crucial for the ability of PML/RARα to mediate RA-response.

The transforming proteins of acute promyelocytic leukaemias (APL) are fusions of the promyelocytic leukaemia (PML) and the promyelocytic leukaemia zinc-finger (PLZF) proteins with retinoic acid receptor-α (RARα)1,2. These proteins retain the RARα DNA- and retinoic acid (RA)-binding domains, and their ability to block haematopoietic differentiation depends on the RARα DNA-binding domain3,4,5,6. Thus RA-target genes are downstream effectors7,8. However, treatment with RA induces differentiation of leukaemic blast cells and disease remission in PML–RARα APLs, whereas PLZF–RARα APLs are resistant to RA1,2. Transcriptional regulation by RARs involves modifications of chromatin by histone deacetylases, which are recruited to RA-target genes by nuclear co-repressors9,10. Here we show that both PML–RARα and PLZF–RARα fusion proteins recruit the nuclear co-repressor (N-CoR)–histone deacetylase complex through the RARα CoR box. PLZF–RARα contains a second, RA-resistant binding site in the PLZF amino-terminal region. High doses of RA release histone deacetylase activity from PML–RARα, but not from PLZF–RARα. Mutation of the N-CoR binding site abolishes the ability of PML–RARα to block differentiation, whereas inhibition of histone deacetylase activity switches the transcriptional and biological effects of PLZF–RARα from being an inhibitor to an activator of the RA signalling pathway. Therefore, recruitment of histone deacetylase is crucial to the transforming potential of APL fusion proteins, and the different effects of RA on the stability of the PML–RARα and PLZF–RARα co-repressor complexes determines the differential response of APLs to RA.

PML/RARα is the abnormal protein product of the Acute Promyelocytic Leukemia-specific 15;17 translocation. Both the PML and RARα components are required for the PML/RARα biological activities, namely its capacity to block differentiation and to increase survival of haematopoietic precursors. The physiological role of PML and its contribution to the function of the fusion protein are unknown. PML localizes to the cytoplasm and within specific nuclear bodies (NBs). In vitro , overexpression of PML correlates with suppression of cell transformation. The PML aminoterminal portion retained within the PML/RARα protein contains the RING finger, two newly defined cystein/histidine-rich motifs called B-boxes (B1 and B2) and a coiled-coil region. We report here that PML has a growth suppressive activity in all the cell lines tested, regardless of their transformed phenotype, and that the cellular basis for the PML growth suppression is induction of apoptotic cell death. Analysis of various nuclear and cytoplasmic PML isoforms showed that the PML growth suppressive activity correlates with its nuclear localization. Analysis of the localization and growth suppressive activity demonstrated that: (i) the Ring+B1-B2 and coiled-coil regions are both indispensable and sufficient to target PML to the NBs; (ii) individual deletions of the various PML domains have no effect on its growth suppressor activity; (iii) the Ring+B1-B2 region exerts a partial growth suppressor activity but its fusion with the coiled-coil region is sufficient to recapitulate the suppressive function of wild type PML. These results indicate that PML is involved in cell survival regulation and that the PML component of the fusion protein (Ring+B1-B2 and coiled-coil regions) retains intact biological activity, thereby suggesting that the effects of PML/RARα on survival derive from the activation of the incorporated PML sequence.

T lymphocytes infiltrating airways during the allergic immune response play a fundamental role in recruiting other specialized cells, such as eosinophils, by secreting interleukin 5 (IL-5), and promoting local and systemic IgE synthesis by producing EL-4. Whether these presumed allergen-specific T cells are of mucosal or systemic origin is still a matter of conjecture.

The field of molecular epidemiology, using modern epidemiological approaches and taking the advantage of the advances in molecular biology can provide new tools for the exploration of etiological determinants, either environmental or hereditary, in the development of hematological neoplasms. It is now possible to identify some host susceptibility characteristics, to measure the effective dose of exposure, and to identify early, pre-clinical biological effects, using sensitive and specific biomarkers. The significant variation in the incidence of hematological neoplasms in different geographical areas, races, and age groups, the high rates of familial aggregation in certain populations, the involvement of protooncogenes and tumor suppressor genes in the development of hematological neoplasms, as well as of many environmental agents such as chemicals, radiation, and viruses, support the important role of molecular epidemiology in the investigation of the development of hematological neoplasms.

INTRODUCTION Philadelphia positive chronic myelogenous leukemia (Ph1+ CML) is a myeloproliferative disorder of clonal origin, due to neoplastic transformation of a pluripotent stem cell, and characterized by excessive proliferation of hemopoietic precursors and expansion of the myeloid cellular mass1. In 90-95% of cases, the disease is associated with a chromosomal abnormality, the Ph1 chromosome, derived from a reciprocal translocation t(9;22) (q34;q11) between chromosomes 9 and 222. The translocation of the proto-oncogene c-abl from its normal location on chromosome 9 to the break-point cluster region (bcr) of chromosome 22 involves the formation of a chimeric gene (abl-bcr), the product of which is a protein with increased tyrosine-kinase activity3,4. It seems likely that the bcr rearrangement plays an important role in the pathogenesis of CML. Characteristically, the disease presents two phases: a “benign” or chronic phase lasting about 3 years, well controlled by chemotherapy, and a terminal blastic phase, refractory to chronic-phase treatments, invariably fatal in 3-6 months and frequently associated with cytogenetic abnormalities additional to the Ph1.Key Words: Interferonschronic myelogenous leukemiaPhiladelphia chromosome

The finger motif is a tandemly repeated DNA-binding domain recently identified in the primary structure of several eukaryotic transcriptional regulatory proteins. It has been proposed that some members of the finger-gene family are implicated in both normal cell proliferation and differentiation. We isolated several human finger genes by means of hybridization with a finger motif-containing DNA probe. One of these finger genes, HF.10, is expressed at low levels in a variety of human tissues and is down-regulated during the in vitro terminal differentiation of human leukemic myeloid cell lines. By in situ hybridization experiments and analysis of interspecific somatic cell hybrids we mapped the HF.10 gene to 3p21–22, a chromosome region frequently involved in karyotypic rearrangements associated with lung and renal cancer.

The cytogenetic follow-up of a case of refractory anemia with excess of blasts (RAEB) that rapidly evolved to acute myeloblastic leukemia (Ml-FAB type) is described. Bone marrow analysis at presentation revealed two chromosomally abnormal clones that shared an interstitial deletion of the long arm of chromosome 5 (5q−) and a terminal deletion of the short arm of chromosome 12 (12p-), but that differed from one another in the localization of a very similar segment of chromosome 17 (i.e. 17q11−12qter) on two clearly distinct karyotypic sites: 2q37 and 17q25. Fourteen percent of the metaphases examined bore the 2q+ marker and 38% the 17q+ marker; the remaining cells had a normal karyotype. A second study carried out 4 months later, at onset of the acute phase, revealed that the clone with normal karyotype had almost completely disappeared and that there had been an inversion in the ratio of the two abnormal cell populations. In the final study, made 1 month before death, the cells with t(2;17) had totally effaced the other clone.

Chronic myelocytic leukemia (CML) is a well-known myeloproliferative disorder, with typical clinical and hematological features, which develops into a lethal blastic crisis within an average of 4 years. In the last few years much has been learned about the cell responsible for the leukemic deviation, chromosomal abnormalities both in chronic phase and in blastic transformation, biochemical and cytochemical behavior of leukemic cells, and the immunology of the disease. On the contrary, polychemotherapy has brought but little progress in CML treatment. However, thorough research on prognostic factors at the onset of the disorder allows a more rational approach to the treatment, and in the near future interesting progress in bone marrow transplantation is to be expected. Also, monoclonal antibody techniques will reveal further knowledge on the origin and differentiation of leukemic cells and the relationship between the chronic phase and the blastic deviation.

Fifteen Hodgkin's disease patients (8 male, 7 female) aged 19–72 years, who had been in complete unmaintained remission for 1 year or more when the study was initiated, were given 50 mg thymostimulin (TS) IM daily for 60 consecutive days. When compared with 26–30 age- and sex-matched controls, as a group the patients' circulating ENR+, OKT 3 + , and OKT 4 + cells were depressed (0.001≤P≤ .06), whereas their OKT 8 + cell population was not. Low (>1 SD or >2 SD below mean in controls) or borderline (mean value of two subsequent tests >1 SD below mean in controls) values of ENR+, OKT 3 + , and OKT 4 + cells were seen in nine (group I) of the 15 patients tested, while the remaining six patients (group II) had normal T-cell proportions. Following TS treatment, the proportions of ENR+, OKT 3 + , and OKT 4 + cells increased to normal in all group I patients. The T-cell levels, however, decreased to pretreatment values 60–70 days after completion of TS therapy. TS had no effect on the group II patients whose T-cell percentages had initially been normal. Spontaneous cell-mediated cytotoxicity (SCMC) was assessed in 11 patients, and irrespective of the baseline values, there was a significant enhancement (P<0.005) by day 15 of TS administration, which was maintained during treatment. SCMC, however, returned to pretreatment levels 60–70 days after TS was discontinued. The delayed skin test reactivity to DNCB was significantly depressed in all cases. Although TS restored the T-cell proportions, it failed to reverse DNCB reactivity from negative to positive in any of the patients tested. TS can thus restore defective T-cell frequencies and can enhance cytolytic functions that are potentially important in host immunosurveillance, but it apparently failed to improve the skin reactivity to neoantigen.

Chronic myelocytic leukemia (CML) is a well-known myeloproliferative disorder, with typical clinical and hematological features, which develops into a lethal blastic crisis within an average of 4 years. In the last few years much has been learned about the cell responsible for the leukemic deviation, chromosomal abnormalities both in chronic phase and in blastic transformation, biochemical and cytochemical behavior of leukemic cells, and the immunology of the disease. On the contrary, polychemotherapy has brought but little progress in CML treatment. However, thorough research on prognostic factors at the onset of the disorder allows a more rational approach to the treatment, and in the near future interesting progress in bone marrow transplantation is to be expected. Also, monoclonal antibody techniques will reveal further knowledge on the origin and differentiation of leukemic cells and the relationship between the chronic phase and the blastic deviation.

Cord blood samples from healthy full-term newborns were tested with antimature and antiimmature lymphoid-cell monoclonal antibodies, as well as more traditional markers, in order to identify the phenotype of circulating precursor cells. The results demonstrated that human cord blood contains a lower number of OKT3+, E-rosetting mature T cells than adult blood, very high levels of OKT10+ cells, and few OKT9+, OKT8+OKT3−, and OKT4+OKT3− cells. Although the finding of OKT9+ and OKT10+ cord circulating cells could be indicative of cell activation, double marker studies in newborn blood pointed to phenotypically immature lymphoid subsets at different stages of maturation, according to Reinherz's hypothesis. In addition, the absence of nuclear Tdt-positive and hot-rosetting cells, together with the fact that most of these are OKT3+, OKT10+, OKT4+, or OKT8+ cells, suggests that the surface phenotype of newborn lymphocytes is similar to that of mature thymocytes.

Die Verfasser beschreiben eine Methode für die unvollständige Reinigung der Cyclohydrolase aus menschlichen leukämischen Leukocyten. Die Methode besteht in zwei Fraktionierungen mit (NH4)2SO4 und erlaubt eine zweimalige Reinigung des Enzyms. Eine Ausbeute von 77% wurde erhalten. Einige Eigenschaften des unvollständig gereinigten Enzyms wurden beschrieben.