A case of extrahepatic portal vein aneurysm with massive thrombosis: diagnosis with reconstruction images from helical CT scans

Acute promyelocytic leukemia (APL) originate from chromosomal translocations generating two types of fusion proteins both involving the retinoic acid receptor alpha (RAR alpha) and either the gene PML (t(15;17)) or PLZF (t(11;17)). Recent publications cast a new light on the detailed molecular mechanism underlying the oncogenic activity of these fusion proteins which block myeloid terminal differentiation by recruiting histone deacetylases to the promoters of target genes through co-repressor proteins. They also explain the different responses to treatment by all-trans retinoic acid (ATRA) of these two variants which are otherwise clinically indistinguishable.     

Infrequent alterations of the RAR alpha gene in acute myelogenous leukemias, retinoic acid-resistant acute promyelocytic leukemias, myelodysplastic syndromes, and cell lines

Retinoids are important regulators of cell growth and differentiation in vitro and in vivo and they exert their biologic activities by binding to nuclear retinoic acid receptors (RARs; alpha, beta, and gamma) and retinoid X receptors (RXRs; alpha, beta, and gamma). All-trans retinoic acid (RA) induces complete remission in patients with acute promyelocytic leukemia (APL) presumably by binding directly to RAR alpha of APL cells. Leukemic blasts from APL patients initially responsive to RA can become resistant to the agent. HL-60 myeloblasts cultured with RA have developed mutations of the ligand-binding region of RAR alpha and have become resistant to RA. Furthermore, insertion of an RAR alpha with an alteration in the ligand-binding region into normal murine bone marrow cells can result in growth factor-dependent immortalization of the early hematopoietic cells. To determine if alterations of the ligand binding domain of RAR alpha might be involved in several malignant hematologic disorders, the mutational status of this region (exons 7, 8, and 9) was examined in 118 samples that included a variety of cell lines and fresh cells from patients with myelodysplastic syndromes (MDS) and acute myeloid leukemias (AML), including 20 APL patients, 5 of whom were resistant to RA and 1 who was refractory to RA at diagnosis, using polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) analysis and DNA sequencing. In addition, 7 of the 20 APLs were studied for alterations of the other coding exons of the gene (exons 2 through 6). No mutations of RAR alpha were detected. Although the sensitivity of PCR-SSCP analysis is less than 100%, these findings suggest that alterations of RAR alpha gene are rare and therefore other mechanisms must be involved in the onset of resistance to retinoids and in the lack of differentiation in disorders of the myeloid lineage.     

Altered retinoic acid receptors

Structurally and functionally altered retinoic acid receptors have been associated with rare human neoplasms: acute promyelocytic leukemia and hepatocellular carcinoma. Whereas the retinoic acid receptor beta (RARbeta) rearrangement in hepatocellular carcinoma is unique, in acute promyelocytic leukemia (APL), RARalpha fusion to the promyelocytic leukemia (PML) gene by the t(15;17) translocation is a general feature of the disease. APL is an important model in cancer biology because retinoic acid induces complete remissions in this malignancy, providing the first example of differentiation therapy and of an antineoplastic drug directly targeted at the underlying genetic lesion. The molecular basis of PML/RARalpha fusion leukemogenesis is discussed with respect to dominant negative inhibition of nuclear receptor and PML functions.     

Establishment of a retinoic acid-resistant human acute promyelocytic leukaemia (APL) model in human granulocyte-macrophage colony-stimulating factor (hGM-CSF) transgenic severe combined immunodeficiency (SCID) mice

To understand the mechanisms and identify novel approaches to overcoming retinoic acid (RA) resistance in acute promyelocytic leukaemia (APL), we established the first human RA-resistant APL model in severe combined immunodeficiency (SCID) mice. UF-1 cells, an RA-resistant APL cell line established in our laboratory, were transplanted into human granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing SCID (hGMTg SCID) mice and inoculated cells formed subcutaneous tumours in all hGMTg SCID mice, but not in the non-transgenic control SCID mice. Single-cell suspensions (UF-1/GMTg SCID cells) were similar in morphological, immunological, cytogenetic and molecular genetic features to parental UF-1 cells. All-trans RA did not change the morphological features of cells or their expression of CD11b. RA did not alter the growth curve of cells as determined by MTT assay, suggesting that UF-1/GMTg SCID cells are resistant to RA. These results demonstrate that this is the first RA-resistant APL animal model that may be useful for investigating the biology of this myeloid leukaemia in vivo, as well as for evaluating novel therapeutic approaches including patients with RA-resistant APL.     

Treatment of acute promyelocytic leukemia--combined use of all-trans retinoic acid and granulocyte colony-stimulating factor

We evaluated the effect of treatment by all-trans retinoic acid (ATRA) in 9 patients with acute promyelocytic leukemia (APL). Of 6 patients who had circulating leukemic blasts before treatment, 3 initially received ATRA alone but died of respiratory failure due to retinoic acid syndrome (RAS). High dose steroid therapy did not rescue RAS in these patients. Another 3 who were given intensive chemotherapy followed by ATRA and/or granulocyte colony-stimulating factor (G-CSF) achieved complete remission (CR). Of 3 patients without peripheral leukemic blasts before treatment, 1 received intensive chemotherapy followed by G-CSF and reached CR, 1 who had been previously given ATRA did not respond to ATRA, and 1 did not initially respond sufficiently to ATRA alone but responded dramatically to ATRA plus G-CSF. In the treatment of APL, appropriate combination of ATRA, G-CSF and chemotherapy should always be taken into consideration. In addition, RAS have to be carefully avoided when applying ATRA therapy in patients who have circulating leukemic blasts before treatment.     

A PMLRARalpha transgene initiates murine acute promyelocytic leukemia

The malignant cells of acute promyelocytic leukemia (APL) contain a reciprocal chromosomal translocation that fuses the promyelocytic leukemia gene (PML) with the retinoic acid receptor alpha gene (RAR alpha). To test the hypothesis that the chimera PMLRAR alpha plays a role in leukemogenesis, we expressed a PMLRAR alpha cDNA in myeloid cells of transgenic mice. PMLRAR alpha transgenic mice exhibited impaired neutrophil maturation early in life, which progressed at a low frequency over the course of several months to overt APL. Both the preleukemic state and the leukemia could be transplanted to nontransgenic mice, and the transplanted preleukemia could progress to APL. The APL recapitulated features of the human disease, including a response to retinoic acid. Retinoic acid caused the leukemic cells to differentiate in vitro and in vivo, eliciting remissions of both the preleukemic state and APL in mice. Our results demonstrate that PMLRAR alpha impairs neutrophil differentiation and initiates the development of APL. The transgenic mice described here provide an apparently accurate model for human APL that includes clear evidence of tumor progression. The model should be useful for exploring the molecular pathogenesis of APL and the mechanisms of the therapeutic response to retinoic acid, as well as for preclinical studies of therapeutic regimens.     

Polyenylidene thiazolidinedione derivatives with retinoidal activities

Several polyenylidene thiazolidine or 2-thioxo-4-thiazolidinone derivatives were synthesized and their retinoidal activities were examined in terms of the differentiation-inducing ability towards human promyelocytic leukemia HL-60 cells and inhibitory effect on interleukin (IL)-1 alpha-induced IL-6 production in MC3T3-E1 cells. Compounds containing a trimethylcyclohexenyl ring induced HL-60 cell differentiation with weaker activity than retinoic acid (1a) by one or two orders of magnitude. The thiazolidinedione derivatives (2, 5, 7) showed stronger activity than the corresponding 2-thioxo-4-thiazolidinone derivatives (3, 6, 8). The effects of a retinoid antagonist (LE540) and synergists (retinoid X receptor (RXR) agonists, HX600 or HX630) on the activities of thiazolidine derivatives indicate that these compounds elicit their activities through the nuclear retinoic acid receptors (RARs). All the thiazolidines examined also inhibited IL-1 alpha-induced IL-6 production with IC50 values of 10 nM order. The retinoidal activities of the thiazolidines are significant, considering that replacement of the carboxylic acid in retinoid structures with bioisosteric functional groups is generally ineffective, as seen in the structure-activity relationships of retinoidal benzoic acids.     

Efficacy of fluorescence in situ hybridization for detecting PML/RARA gene fusion in treated and untreated acute promyelocytic leukemia

OBJECTIVE: To test the efficacy of fluorescence in situ hybridization (FISH) for detection of fusion of the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARA) genes in patients with treated or untreated acute promyelocytic leukemia (APL). DESIGN: We conducted a retrospective blind study on a series of stored bone marrow specimens from normal subjects and patients with APL. MATERIAL AND METHODS: Conventional cytogenetic and FISH analyses were done on interphase and metaphase cells in specimens from 31 normal subjects and 19 patients with untreated or treated APL. RESULTS: From 25 of the normal specimens, we calculated a normal cutoff of 10% for interphase cells and 0% for metaphase cells. With use of these criteria, the other six specimens from normal subjects showed normal findings, and each of the seven specimens from patients with untreated APL was abnormal by FISH analysis. The specimens from four patients in clinical relapse or with residual APL were abnormal. Of the eight specimens from patients in clinical remission, three were abnormal; two of these patients had a relapse within 8 months, and the other patient had received 1 month of chemotherapy and was entering remission. Of the other five patients in remission, four had normal FISH results and have now been in remission for 2.5 to 10 years. The other patient in remission with normal FISH results had a relapse within 6 months. PML/RARA fusion was detectable in three patients with hypogranular APL and in three with a cytogenetic variant of the t(15;17). CONCLUSION: The results of this study suggest that FISH with PML and RARA probes can be used to diagnose APL and may be useful for monitoring treated patients.     

Trivalent antimonials induce degradation of the PML-RAR oncoprotein and reorganization of the promyelocytic leukemia nuclear bodies in acute promyelocytic leukemia NB4 cells

Acute promyelocytic leukemia (APL) is characterized by a specific t(15;17) chromosomal translocation that fuses the genes encoding the promyelocytic leukemia protein (PML) and the retinoic acid receptor (RAR). The resulting PML-RAR protein induces a block in the differentiation of the myeloid progenitor cells, which can be released by retinoic acid (RA) in vitro and in vivo. The RA-induced differentiation of APL blasts is paralleled by the degradation of the fusion protein and the relocation of wild-type PML from aberrant nuclear structures to its normal localization in nuclear bodies. Recently, arsenic trioxide (As2O3) treatment was proposed as an alternative therapy in APL, because it can induce complete remission in both RA-sensitive and -resistant APL patients. Intriguingly, As2O3 was also shown to induce degradation of the PML-RAR chimera and to reorganize PML nuclear bodies. Here we show that trivalent antimonials also have striking effects on RA-sensitive and RA-resistant APL cells. Treatment of the APL-derived NB4 cells and the RA-resistant subclone NB4R4 with antimony trioxide or potassium antimonyl tartrat triggers the degradation of the fusion protein and the concomitant reorganization of the PML nuclear bodies. In addition, as reported for As2O3, the antimonials provoke apoptosis of NB4 and NB4R4 cells. The mechanism of antimony action is likely to be similar to that of As2O3, notably both substances induce the attachment of the ubiquitin-like SUMO-1 molecule to the PML moiety of PML-RAR. From these data, we propose that, in analogy to As2O3, antimonials might have a beneficial therapeutic effect on APL patients, perhaps with less toxicity than arsenic.     

Cross-talk between retinoic acid and interferons: molecular mechanisms of interaction in acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) and interferons (IFNs) are active anticancer agents. ATRA is capable of inducing complete remission in acute promyelocytic leukemia (APL) patients, whereas IFNalpha is successfully used in the treatment of the stable phase of chronic myeloid leukemia. ATRA and IFNs have shown synergistic interactions in various experimental conditions and represent a potentially useful therapeutic combination in the treatment of various types of leukemias and solid tumors. The molecular basis of these interactions are poorly understood and need to be elucidated. In this review, we summarize a series of recent observations concerning the molecular mechanisms underlying the cross-talk between the intracellular pathways activated by ATRA and IFNs in APL cells. In APL blasts, IFNs regulate the expression of retinoic acid receptors, and ATRA, in turn, modulates the levels and the state of activation of members of the Jak-STAT second messenger pathway. This demonstrates a two-way interaction between ATRA and IFNs, which leads to cross-modulation of genes normally under the control of the retinoid and the cytokine. These data may be relevant in the context of a rational use of the combination between ATRA and IFNs in the clinical management of myeloid leukemias.     

Gq-protein alpha subunit expression and distribution in pregnant rat myometrial tissues

Coagulation patterns of 19 newly-diagnosed acute promyelocytic leukemia (APL) patients with disseminated intravascular coagulation (DIC) at presentation were studied. Seventeen patients had hemorrhagic complications, of which four were fatal. Fatal hemorrhages were related with lower fibrinogen level and lower platelet count. DIC of the APL patients without infection was characterized by low fibrinogen and normal antithrombin III (ATIII) level. Thrombin-ATIII complex level was elevated in all patients examined. Patients with infection had higher fibrinogen levels than those without infection and some patients had reduced ATIII level. Ten remission inductions were tried with multidrug chemotherapy and seven with all-trans retinoic acid (ATRA). Complete remission was achieved in seven of ten inductions with chemotherapy and in all seven inductions with ATRA. Two patients treated with chemotherapy had fatal hemorrhage after starting therapy but none treated with ATRA.