Treatment of acute promyelocytic leukemia: strategy toward further increase of cure rate

De-repression of CTGF via the miR-17-92 cluster upon differentiation of human glioblastoma spheroid cultures

All-trans retinoic acid is a potent promoter of cellular differentiation processes, which is used in cancer therapy. Glioblastoma spheroid cultures are enriched in tumor-initiating cells, and provide a model to test new treatment options in vitro. We investigated the molecular mechanisms of response to exposure to differentiation-promoting conditions in such cultures. Microarray analyses of five independent cultures showed that after induction of differentiation, inhibitors of transforming growth factor-beta/bone morphogenetic protein, Wnt/beta-catenin and IGF signaling were upregulated, whereas expression of several microRNAs decreased, particularly that of the miR-17-92 cluster. In primary astrocytic gliomas (n=82), expression of several members of miR-17-92 was significantly higher relative to those of normal brain (n=8) and significantly increased with tumor grade progression (P<0.05). A high-level amplification of the miR-17-92 locus was detected in one glioblastoma specimen. Transfection of inhibitors of miR-17-92 induced increased apoptosis and decreased cell proliferation in glioblastoma spheroids. Mir-17-92 inhibition was also associated with increased messenger RNA (mRNA) and/or protein expression of CDKN1A, E2F1, PTEN and CTGF. The CTGF gene was shown to be a target of miR-17-92 in glioblastoma spheroids by luciferase reporter assays. Our results suggest that miR-17-92 and its target CTGF mediate effects of differentiation-promoting treatment on glioblastoma cells through multiple regulatory pathways.

Promyelocytic sarcoma of the spine: a case report and review of the literature

Myeloid sarcoma (MS, previously named granulocytic sarcoma or chloroma) is a rare extramedullary tumour of immature myeloid cells. It can be present before, concurrently with, or after the diagnosis of acute myeloid leukemia. MS is extremely uncommon in acute promyelocytic leukemia (APL). In the case described here, MS was the sole site of APL relapse and the cause of spinal cord compression. The patient presented with neurologic symptoms due to a paravertebral mass of MS after 7 years of complete remission. He was treated with excision of the mass followed by local radiotherapy. Systemic treatment was also given with combined arsenic trioxide and all-trans retinoic acid and the patient was able to achieve a second prolonged clinical and molecular remission.

Arsenic trioxide-mediated antiplatelet activity: pivotal role of the phospholipase C gamma 2-protein kinase C-p38 MAPK cascade

Arsenic trioxide produces high rates of complete clinical remission in patients with relapsed/refractory acute promyelocytic leukemia. Platelet activation is relevant in a variety of acute thrombotic events and coronary heart diseases. Few studies have examined the effects of arsenic trioxide on platelets, and the mechanisms underlying the signaling pathways remain obscure. The aim of this study was to examine systematically the detailed mechanisms of arsenic trioxide in preventing platelet activation. Arsenic trioxide (5 micromol/L) exhibited more potent activity at inhibiting collagen (1 microg/mL)-induced platelet aggregation than other agonists. Arsenic trioxide (15 and 25 micromol/L) inhibited collagen-induced platelet activation accompanied by [Ca(+2)]i mobilization, thromboxane A(2) (TxA(2)) formation, phospholipase C (PLC)gamma 2 phosphorylation, and protein kinase C (PKC) activation. Arsenic trioxide (15 and 25 micromol/L) did not significantly affect cyclic nucleotide-induced vasodilator-stimulated phosphoprotein phosphorylation. Moreover, arsenic trioxide markedly inhibited p38 mitogen-activated protein kinase (MAPK) but not JNK1/2 or ERK2 phosphorylation in washed platelets. Arsenic trioxide also markedly reduced hydroxyl radical (OH(.)) formation in the erythrocyte sedimentation rate (ESR) study. The most important findings of this study suggest that the inhibitory effect of arsenic trioxide possibly involves inhibition of the PLC gamma 2-PKC-p38 MAPK cascade, thereby leading to inhibition of [Ca(+2)]i or free radical formation, and finally the inhibition of platelet aggregation.

Very long-term outcome of acute promyelocytic leukemia after treatment with all-trans retinoic acid and chemotherapy: the European APL Group experience

Acute promyelocytic leukemia (APL) is highly curable with the combination of all-trans retinoic acid (ATRA) and anthracycline-based chemotherapy (CT), but very long-term results of this treatment, when CT should be added to ATRA and the role of maintenance treatment, remain uncertain. In our APL93 trial that included 576 newly diagnosed APL patients, with a median follow-up of 10 years, 10-year survival was 77%. Maintenance treatment significantly reduced 10-year cumulative incidence of relapses, from 43.2% to 33%, 23.4%, and 13.4% with no maintenance, maintenance using intermittent ATRA, continuous 6 mercaptopurine plus methotrexate, and both treatments, respectively (P < .001). Maintenance particularly benefited patients with white blood cell (WBC) count higher than 5 x 10(9)/L (5000/microL). Early addition of CT to ATRA significantly improved 10-year event-free survival (EFS), but without significant effect on overall survival (OS). The 10-year cumulative incidence of deaths in complete response (CR), resulting mainly from myelosuppression, was 5.7%, 15.4%, and 21.7% in patients younger than 55, 55 to 65, and older than 65 years, respectively, supporting the need for less myelosuppressive treatments, particularly for consolidation therapy. This study is registered at http://clinicaltrials.gov as NCT00599937.

Effect of slow-releasing all-trans-retinoic acid in bioabsorbable polymer on delayed adjustable strabismus surgery in a rabbit model

PURPOSE

To determine the usefulness of slow-releasing all-trans-retinoic acid (ATRA) in polytetrafluoroethylene (PTFE)/polylactide-co-glycolide (PLGA) for delayed adjustable strabismus surgery.

DESIGN

Animal study.

METHODS

A prospective, masked-observer, controlled study was performed in 25 rabbits. Fifty rabbit eyes were divided randomly into three groups. After a recession of the superior rectus muscle, a PTFE/PLGA laminate containing ATRA, PTFE alone, or balanced salt solution was applied beneath and over the superior rectus muscle in the PTFE/PLGA/all-trans-retinoic acid group (ATRA group), the polytetrafluoroethylene group (PTFE group), and the control group, respectively. Delayed adjustment was performed once on each superior rectus muscle at 3 or 5 weeks after surgery by a masked observer.

RESULTS

In the control group, adjustment was possible in 2 of 5 eyes at 3 weeks after surgery and impossible in any eye at 5 weeks after surgery. In the PTFE and ATRA groups, adjustment was possible in all 10 eyes at 3 and 5 weeks after surgery. On comparing adjustability, a significant difference was observed between the PTFE group and the control group or between the ATRA group and the control group 5 weeks after surgery (P = .0003 and P = .0003, respectively). A significant difference was observed between the ATRA group and the control group in terms of adhesion between superior rectus muscles and sclerae at 5 weeks after surgery (P = .006).

CONCLUSIONS

Slow-releasing ATRA in PTFE/PLGA was found to reduce adhesion and to allow delayed adjustment in most eyes for up to 5 weeks after surgery.

Targeting promyelocytic leukemia protein: a means to regulating PML nuclear bodies

The promyelocytic leukemia protein (PML) is involved in many cellular processes including cell cycle progression, DNA damage response, transcriptional regulation, viral infection, and apoptosis. These cellular activities often rely on the localization of PML to unique subnuclear structures known as PML nuclear bodies (NBs). More than 50 cellular proteins are known to traffic in and out of PML NBs, either transiently or constitutively. In order to understand the dynamics of these NBs, it is important to delineate the regulation of PML itself. PML is subject to extensive regulation at transcriptional, post-transcriptional, and post-translational levels. Many of these modes of regulation depend on the cellular context and the presence of extracellular signals. This review focuses on the current knowledge of regulation of PML under normal cellular conditions as well as the role for regulation of PML in viral infection and cancer.

Incidence of extramedullary disease in patients with acute promyelocytic leukemia: a single-institution experience

Using current treatment regimens, over 90% of patients with acute promyelocytic leukemia will achieve complete remission (CR). However, approximately 30% of these patients will relapse, including a small proportion who will develop extramedullary disease (EMD). In this study, we investigated the incidence of EMD in 263 patients with APL who were treated at our institution from January 1990 to May 2008. With a median follow-up of 31 months (range 2 days-203 months), 8 (3%) patients developed EMD. The most commonly affected site was the central nervous system (n = 7). Before developing EMD, one patient had achieved CR with a chemotherapy-only regimen, six patients had achieved CR with all-trans-retinoic acid (ATRA)-based regimens, and one patient had achieved CR with an ATRA plus arsenic trioxide (ATO)-based regimen. The EMD conferred a poor prognosis; five patients died within 4 months of developing EMD. The molecular status did not predict EMD; four patients had a negative PCR for the PML-RARA transcripts prior to relapse with EMD. In conclusion, the incidence of EMD is low. We were unable to identify any specific factors that could predict the development of EMD.

Successful treatment by all-trans retinoic acid in a patient with acute promyelocytic leukemia complicated by liver cirrhosis and polycystic kidney

Although all-trans retinoic acid (ATRA) is widely used in acute promyelocytic leukemia (APL), there is little data as to whether or not ATRA is useful for patients with liver and renal failure. A 63-year-old APL patient, complicated by Child-Pugh class A liver cirrhosis and chronic renal failure (creatinine 3.2 mg/dL), was successfully treated with 45 mg/m(2)/day of ATRA. With three courses of chemotherapy, complete remission has been maintained for four years in this patient. Serum trough and maximum ATRA concentration, and the area under the curve (AUC) were not elevated. These observations suggest that full-dose ATRA therapy might be safely applicable to such a complicated case with APL.

Differentiation therapy of hepatocellular carcinoma in mice with recombinant adenovirus carrying hepatocyte nuclear factor-4alpha gene

Previous studies have shown that hepatocyte nuclear factor-4alpha (HNF4alpha) is a central regulator of differentiated hepatocyte phenotype and forced expression of HNF4alpha could promote reversion of tumors toward a less invasive phenotype. However, the effect of HNF4alpha on cancer stem cells (CSCs) and the treatment of hepatocellular carcinoma (HCC) with HNF4alpha have not been reported. In this study, an adenovirus-mediated gene delivery system, which could efficiently transfer and express HNF4alpha, was generated to determine its effect on hepatoma cells (Hep3B and HepG2) in vitro and investigate the anti-tumor effect of HNF4alpha in mice. Our results demonstrated that forced re-expression of HNF4alpha induced the differentiation of hepatoma cells into hepatocytes, dramatically decreased "stemness" gene expression and the percentage of CD133(+) and CD90(+) cells, which are considered as cancer stem cells in HCC. Meanwhile, HNF4alpha reduced cell viability through inducing apparent apoptosis in Hep3B, while it induced cell cycle arrest and cellular senescence in HepG2. Moreover, infection of hepatoma cells by HNF4alpha abolished their tumorigenesis in mice. Most interestingly, systemic administration of adenovirus carrying the HNF4alpha gene protected mice from liver metastatic tumor formation, and intratumoral injection of HNF4alpha also displayed significant antitumor effects on transplanted tumor models.

CONCLUSION

The striking suppression effect of HNF4alpha on tumorigenesis and tumor development is attained by inducing the differentiation of hepatoma cells--especially CSCs--into mature hepatocytes, suggesting that differentiation therapy with HNF4alpha may be an effective treatment for HCC patients. Our study also implies that differentiation therapy may present as one of the best strategies for cancer treatment through the induction of cell differentiation by key transcription factors.

Management of acute promyelocytic leukemia: recommendations from an expert panel on behalf of the European LeukemiaNet

The introduction of all-trans retinoic acid (ATRA) and, more recently, arsenic trioxide (ATO) into the therapy of acute promyelocytic leukemia (APL) has revolutionized the management and outcome of this disease. Several treatment strategies using these agents, usually in combination with chemotherapy, but also without or with minimal use of cytotoxic agents, have provided excellent therapeutic results. Cure of APL patients, however, is also dependent on peculiar aspects related to the management and supportive measures that are crucial to counteract life-threatening complications associated with the disease biology and molecularly targeted treatment. The European LeukemiaNet recently appointed an international panel of experts to develop evidence- and expert opinion-based guidelines on the diagnosis and management of APL. Together with providing current indications on genetic diagnosis, modern risk-adapted front-line therapy and salvage treatment, the review contains specific recommendations for the identification and management of most important complications such as the bleeding disorder, APL differentiation syndrome, QT prolongation and other ATRA- and ATO-related toxicities, as well as for molecular assessment of response to treatment. Finally, the approach to special situations is also discussed, including management of APL in children, elderly patients, and pregnant women.

Neuronal differentiation of synovial sarcoma and its therapeutic application

Synovial sarcoma is a rare sarcoma of unknown histologic origin. We previously reported the gene expression profile of synovial sarcoma was closely related to that of malignant peripheral nerve sheath tumors, and the fibroblast growth factor (FGF) signal was one of the main growth signals in synovial sarcoma. Here we further demonstrate the neural origin of synovial sarcoma using primary tumors and cell lines. The expression of neural tissue-related genes was confirmed in synovial sarcoma tumor tissues, but the expression of some genes was absent in synovial sarcoma cell lines. Treatment of synovial sarcoma cell lines with BMP4 or FGF2 enhanced or restored the expression of neural tissue-related genes and induced a neuron-like morphology with positive Tuj-1 expression. Treatment with all-trans-retinoic acid also induced the expression of neural tissue-related genes in association with growth inhibition, which was not observed in other cell lines except a malignant peripheral nerve sheath tumor cell line. A growth-inhibitory effect of all-trans-retinoic acid was also observed for xenografted tumors in athymic mice. The simultaneous treatment with FGF signal inhibitors enhanced the growth-inhibitory effect of all-trans-retinoic acid, suggesting the combination of growth signaling inhibition and differentiation induction could be a potential molecular target for treating synovial sarcoma.

Breast cancer stem cells: implications for therapy of breast cancer

The concept of cancer stem cells responsible for tumour origin, maintenance, and resistance to treatment has gained prominence in the field of breast cancer research. The therapeutic targeting of these cells has the potential to eliminate residual disease and may become an important component of a multimodality treatment. Recent improvements in immunotherapy targeting of tumour-associated antigens have advanced the prospect of targeting breast cancer stem cells, an approach that might lead to more meaningful clinical remissions. Here, we review the role of stem cells in the healthy breast, the role of breast cancer stem cells in disease, and the potential to target these cells.

PML-RARalpha inhibitors (ATRA, tamibaroten, arsenic troxide) for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by generation of the PML-RARalpha fusion gene. PML-RARalpha can homodimerize with another PML-RARalpha, and the hybrid binds the histone-deacetylase recruiting co-repressor complex with higher affinity than the wild-type RARalpha. However, the co-repressor complex is releasable by pharmacological doses of all-trans retinoic acid (ATRA). More than 90% of patients with APL achieve a complete remission (CR) with differentiation therapy consisting of ATRA combined with chemotherapy. A new synthetic retinoid, tamibaroten, showed therapeutic effectiveness in patients with ATRA-resistant APL with increased expression of cellular retinoic acid binding protein (CRABP), and about 60% of patients with relapsed APL achieved a CR. Arsenic trioxide triggers the rapid degradation of PML-RARalpha through the targeting of the PML moieties of the fusion protein and showed a high CR rate in relapsed APL. The combination of ATRA, chemotherapy, and/or new agents improved the long-term survival in patients with APL.

A randomized study with or without intensified maintenance chemotherapy in patients with acute promyelocytic leukemia who have become negative for PML-RARα transcript after consolidation therapy: The Japan Adult Leukemia Study Group (JALSG) APL97 study

To examine the efficacy of intensified maintenance chemotherapy, we conducted a prospective multicenter trial in adult patients with newly diagnosed acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy. Of the 302 registered, 283 patients were assessable and 267 (94%) achieved complete remission. Predicted 6-year overall survival in all assessable patients and disease-free survival in patients who achieved complete remission were 83.9% and 68.5%, respectively. A total of 175 patients negative for PML-RARα at the end of consolidation were randomly assigned to receive either intensified maintenance chemotherapy (n = 89) or observation (n = 86). Predicted 6-year disease-free survival was 79.8% for the observation group and 63.1% for the chemotherapy group, showing no statistically significant difference between the 2 groups (P = .20). Predicted 6-year survival of patients assigned to the observation was 98.8%, which was significantly higher than 86.2% in those allocated to the intensified maintenance (P = .014). These results indicate that the intensified maintenance chemotherapy did not improve disease-free survival, but rather conferred a significantly poorer chance of survival in acute promyelocytic leukemia patients who have become negative for the PML-RARα fusion transcript after 3 courses of intensive consolidation therapy.

Reinduction of relapsed acute promyelocytic leukemia with ATRA and low dose antimetabolite-based chemotherapy

While the disease-free survival of acute promyelocytic leukemia (APML) now approaches 75%, some children continue to experience relapses, and questions remain as to the optimal management of these patients. We describe two young children who experienced combined relapses in the bone marrow and extramedullary locations following hematopoietic stem cell transplantation (HSCT). An induction regimen, consisting of all-trans retinoic acid (ATRA), methotrexate, and 6-mercaptopurine (6MP), successfully and safely achieved hematologic remission in one patient and molecular remission in the other. These cases demonstrate that there is a role for ATRA plus differentiating chemotherapy other than arsenic trioxide in the treatment of relapsed APML.

Leukemia: stem cells, maturation arrest, and differentiation therapy

Human myeloid leukemias provide models of maturation arrest and differentiation therapy of cancer. The genetic lesions of leukemia result in a block of differentiation (maturation arrest) that allows myeloid leukemic cells to continue to proliferate and/or prevents the terminal differentiation and apoptosis seen in normal white blood cells. In chronic myeloid leukemia, the bcr-abl (t9/22) translocation produces a fusion product that is an activated tyrosine kinase resulting in constitutive activation cells at the myelocyte level. This activation may be inhibited by imatinib mesylate (Gleevec, STI-571), which blocks the binding of ATP to the activated tyrosine kinase, prevents phosphorylation, and allows the leukemic cells to differentiate and undergo apoptosis. In acute promyelocytic leukemia, fusion of the retinoic acid receptor-alpha with the gene coding for promyelocytic protein, the PML-RAR alpha (t15:17) translocation, produces a fusion product that blocks the activity of the promyelocytic protein, which is required for formation of the granules of promyelocytes and prevents further differentiation. Retinoic acids bind to the retinoic acid receptor (RAR alpha) component of the fusion product, resulting in degradation of the fusion protein by ubiquitinization. This allows normal PML to participate in granule formation and differentiation of the promyelocytes. In one common type of acute myeloid leukemia, which results in maturation arrest at the myeloid precursor level, there is a mutation of FLT3, a transmembrane tyrosine kinase, which results in constitutive activation of the IL-3 receptor. This may be blocked by agents that inhibit farnesyl transferase. In each of these examples, specific inhibition of the genetically altered activation molecules of the leukemic cells allows the leukemic cells to differentiate and die. Because acute myeloid leukemias usually have mutation of more than one gene, combinations of specific inhibitors that act on the effects of different specific genetic lesions promises to result in more effective and permanent treatment.

Extramedullary disease and targeted therapies for hematological malignancies—is the association real?

During the past years targeted therapies have gained a major role in the treatment of cancer patients, including those with hematological malignancies. Extramedullary involvement is a rare manifestation of acute and chronic leukemias and of multiple myeloma. Nevertheless, with the expanding use of targeted treatments there is an impression that the incidence of extramedullary relapses is increasing. We reviewed the reports on this phenomenon in patients treated with all-trans-retinoic acid and arsenic trioxide for acute promyelocytic leukemia, thalidomide and bortezomib for multiple myeloma and imatinib for chronic myeloid leukemia. The pathogenetic mechanisms suggested are: life prolongation by these treatments allowing for disease progression arising from dormant cells; poor penetration of the drugs to sanctuary sites like the central nervous system; the requirement of some of these drugs, especially thalidomide, for the marrow microenvironment to exert their action; and finally, a possible active role for some of the drugs, like all-trans-retinoic acid. Since the use of these targeted therapies is expanding we should be aware of this association.

Extramedullary relapse in acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy

We analyzed the incidence, presenting features, risk factors of extramedullary (EM) relapse occurring in acute promyelocytic leukemia (APL) treated with all-trans retinoic acid (ATRA) and chemotherapy by using a competing-risk method. In total, 740/ 806 (92%) patients included in three multicenter trials (APL91, APL93 trials and PETHEMA 96) achieved CR, of whom 169 (23%) relapsed, including 10 EM relapses. Nine relapses involved the central nervous system (CNS) and one the skin, of which two were isolated EM relapse. In patients with EM disease, median WBC count was 26950/mm3 (7700-162000). The 3-year cumulative incidence of EM disease at first relapse was 5.0%. Univariate analysis identified age <45 years (P=0.05), bcr3 PML-RARalpha isoform (P= 0.0003) and high WBC counts (> or = 10,000/ mm3) (P<0.0001) as risk factors for EM relapse. In multivariate analysis, only high WBC count remained significant (P= 0.001). Patients with EM relapse had a poorer outcome since median survival from EM relapse was 6.7 months as compared to 26.3 months for isolated BM relapse (P=0.04). In conclusion, EM relapse in APL occurs more frequently in patients with increased WBC counts (> or = 10,000/mm3) and carries a poor prognosis. Whether CNS prophylaxis should be systematically performed in patients with WBC > or = 10,000/mm3 at diagnosis remains to be established.

Sudden death due to undiagnosed acute promyelocytic leukemia: a case report

Acute promyelocytic leukemia (APL) is associated with severe hemorrhagic coagulopathy induced by the release of procoagulant, plasminogen, and protease from leukemic cells. The case described in this report is of a 15-year-old male who unexpectedly died due to a cerebral hemorrhage caused by underlying APL within 12 h after presentation. This case suggests that underlying APL should be considered as a differential diagnosis when sudden death occurs with a fatal spontaneous hemorrhage, although it is rare.

Tumour stem cell-targeted treatment: elimination or differentiation

A wide range of studies suggest that most cancers are clonal and may represent the progeny of a single cell, a cancer stem cell (CSC) endowed with the capacity to maintain tumour growth. The concept of a cancer stem cell emerged decades ago, and the haematopoietic system is where it has mostly gained ground. More recently, CSC have been described in breast cancer and brain tumours. Growing evidence suggests that pathways regulating normal stem cell self-renewal and differentiation are also present in cancer cells and CSC. Malignant tumours can be viewed as an abnormal organ in which a small population of tumourigenic cancer stem cells have escaped the normal limits of self-renewal giving rise to abnormally differentiated cancer cells that contribute to tumour progression and growth. This new model has important implications for the study and treatment of cancer. Understanding the molecular circuitry which contributes to the maintenance of stem cells may provide an insight into the molecular mechanisms of cancer and thus new approaches for elimination or differentiation therapy. Therapies targeting CSC should focus on pathways such as Wnt, Shh and Notch which are required for the maintenance of cancer stem cells, but also on the ABC transporter family and other specific properties of cancer stem cells.

Practice points, consensus, and controversial issues in the management of patients with newly diagnosed acute promyelocytic leukemia

Recent reviews on acute promyelocytic leukemia (APL) treatment have focused on comparing therapeutic approaches, including all-trans retinoic acid (ATRA) and chemotherapy, and do not address several other aspects of APL management that are relevant to the outcome in individual patients. These aspects include appropriate diagnostic tools and strategies, supportive care, recognition and treatment of life-threatening complications, evaluation of response, and, finally, management of the disease in special conditions such as older patients and pregnant women. In addition to reviewing current consensus and controversies of ATRA and chemotherapy treatment, this article addresses the above issues of APL management with special emphasis on aspects that distinguish APL from other acute myelogenous leukemias.

Cancer Stem Cells and Differentiation Therapy

Cancers arise from stem cells in adult tissues and the cells that make up a cancer reflect the same stem cell --> progeny --> differentiation progression observed in normal tissues. All adult tissues are made up of lineages of cells consisting of tissue stem cells and their progeny (transit-amplifying cells and terminally differentiated cells); the number of new cells produced in normal tissue lineages roughly equals the number of old cells that die. Cancers result from maturation arrest of this process, resulting in continued proliferation of cells and a failure to differentiate and die. The biological behavior, morphological appearance, and clinical course of a cancer depend on the stage of maturation at which the genetic lesion is activated. This review makes a comparison of cancer cells to embryonic stem cells and to adult tis sue stem cells while addressing two basic questions: (1) Where do cancers come from?, and (2) How do cancers grow? The answers to these questions are critical to the development of approaches to the detection, prevention, and treatment of cancer.

Two Patients with All-trans Retinoic Acid-Resistant Acute Promyelocytic Leukemia Treated Successfully with Gemtuzumab Ozogamicin as a Single Agent

Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is the target of gemtuzumab ozogamicin (GO), and a significantly lower level of P-glycoprotein (P-gp). Therefore, GO is predicted to be a successful treatment for APL. In this article, we report on the GO treatment of 2 patients with APL, who had fully relapsed after induction therapy with all-trans retinoic acid (ATRA) following chemotherapy. Both patients had relapsed 3 times and were resistant to reinduction therapy with ATRA. GO (9 mg/m2) was administered on days 1 and 15. After GO treatment, both patients achieved complete hematologic and molecular remission. GO may be another promising agent for the treatment of ATRA-resistant relapsed APL when given as salvage chemotherapy.

Effects of chronic retinoid administration on pituitary function

It has been reported that retinoids may affect hypothalamic-pituitary-thyroid axis, causing central hypothyroidism. In the present study, we evaluated pituitary function in 11 male psoriatic patients at baseline and after 1 and 3 months of treatment with acitretin (all-trans retinoic acid, 35 mg/day). Serum LH, FSH, testosterone, cortisol, GH and IGF-I levels were not affected by the treatment. By contrast, we observed a significant decrease in TSH levels (from 0.92 +/- 0.3 to 0.80 +/- 0.3 mU/I, p < 0.05) at 1 month, that reverted to baseline after 3 months. No change in free T4 (FT4) levels occurred, while free T3 (FT3) levels were reduced at 1 and 3 months (from 6.7 +/- 0.5 to 6.2 +/- 0.3 and 6.1 +/- 0.6 pmol/l; p < 0.05, respectively). Moreover, acitretin treatment induced a significant reduction of PRL levels after 3 months (from 182 +/- 70 to 150 +/- 56 mU/l, p < 0.05). During treatment, no change in TSH and PRL response either to TRH or dopamine infusion was observed. In conclusion, we demonstrated that treatment with low dose of acitretin induced a series of hormonal modifications that, in addition to a mild and transient reduction of TSH levels, included a persistent reduction of FT3, probably due to changes in thyroid hormone metabolism, and a decrease in PRL levels.

Efficacy of gemtuzumab ozogamicin on ATRA- and arsenic-resistant acute promyelocytic leukemia (APL) cells

Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is a target of gemtuzumab ozogamicin (GO), and a significantly lower level of P-glycoprotein (P-gp). In this study, we examined whether GO was effective on all-trans retinoic acid (ATRA)- or arsenic trioxide (ATO)-resistant APL cells. Cells used were an APL cell line in which P-gp was undetectable (NB4), ATRA-resistant NB4 (NB4/RA), NB4 and NB4/RA that had been transfected with MDR-1 cDNA (NB4/MDR and NB4/RA/MDR, respectively), ATO-resistant NB4 (NB4/As) and blast cells from eight patients with clinically ATRA-resistant APL including two patients with ATRA- and ATO-resistant APL. The efficacy of GO was analyzed by (3)H-thymidine incorporation, the dye exclusion test and cell cycle distribution. GO suppressed the growth of NB4, NB4/RA and NB4/As cells in a dose-dependent manner. GO increased the percentage of hypodiploid cells significantly in NB4, NB4/RA and NB4/As cells, and by a limited degree in NB4/MDR and NB4/RA/MDR cells. Similar results were obtained using blast cells from the patients with APL. GO is effective against ATRA- or ATO-resistant APL cells that do not express P-gp, and the mechanism of resistance to GO is not related to the mechanism of resistance to ATRA or ATO in APL cells. Leukemia (2005) 19, 1306-1311. doi:10.1038/sj.leu.2403807; published online 26 May 2005.

Retinoid/arsenic combination therapy of promyelocytic leukemia: induction of telomerase-dependent cell death

Acute promyelocytic leukemia (APL) is efficiently treated with a cell differentiation inducer, all-trans retinoic acid (ATRA). However, a significant percentage of patients still develop resistance to this treatment. Recently, arsenic trioxide (As2O3), alone or in combination with ATRA, has been identified as an alternative therapy in patients with both ATRA-sensitive and ATRA-resistant APL. Previous investigations restricted the mechanism of this synergism to the modulation and/or degradation of PML-RARalpha oncoprotein through distinct pathways. In this study, using several ATRA maturation-resistant APL cell lines, we demonstrate in vitro that the success of ATRA/As2O3 treatment in APL pathology can be explained, at least in part, by a synergistic effect of these two drugs in triggering downregulation of telomerase efficient enough to cause telomere shortening and subsequent cell death. Such long-term low-dose combinatorial therapy strategies, developed also to avoid acute side effects, reinforce the notion that the antitelomerase strategy, based on a combination of active agents, should now be considered and evaluated not only in APL but also in other malignancies.

Delayed recovery of normal hematopoiesis in arsenic trioxide treatment of acute promyelocytic leukemia: a comparison to all-trans retinoic acid treatment

OBJECTIVE

To examine laboratory data including total blood cell count, leukocyte morphology and coagulation parameters during treatment for acute promyelocytic leukemia (APL) at a single institute, and compare the precise differences between all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) treatment.

PATIENTS AND METHODS

Sixteen patients with APL who were treated with ATRA or As2O3 alone and achieved complete remission (CR) were analyzed. ATRA 45 mg/m2/day was given orally until CR. As2O3 0.15 mg/kg/day was given intravenously until leukemic blasts and promyelocytes were eliminated from the bone marrow.

RESULTS

All 7 patients in the ATRA-treated group were primary cases and all 9 patients in the As2O3-treated group were relapsed cases after the achievement of CR with the ATRA. There was no difference in the data before treatment between these two groups. The duration of leukocytopenia and neutropenia during As2O3 treatment was significantly longer than those of ATRA treatment. The nadir of leukocyte and neutrophil counts was observed later in the As2O3-treated group. Terminal neutrophil differentiation was observed more obviously in the ATRA-treated group. The red blood cell count and hemoglobin concentration decreased significantly at the end of As2O3 treatment and were lower than those of ATRA treatment. Platelets recovered earlier in the ATRA-treated group. Coagulation parameters were not significantly changed between the two groups.

CONCLUSION

In comparison with ATRA treatment, the recovery of several components in the peripheral blood cells was delayed in As2O3 treatment. Therefore we should pay more and longer attention in As2O3 treatment.

Clinical Significance of FLT3 in Leukemia

FLT3 is a class III receptor tyrosine kinase together with KIT, FMS and PDGFR. FLT3 mutations were first reported as internal tandem duplication (FLT3/ITD) of the juxtamembrane domain-coding sequence, and subsequently as a missense mutation of D835 (FLT3/KDM) within a kinase domain. Furthermore, point mutations, deletions, and insertions in the codons surrounding D835 have also been found. FLT3/ITD and FLT3/KDM occur in 15% to 35% and 5% to 10%, respectively, of patients with AML. FLT3 mutations are, therefore, the most frequent genetic alterations so far reported in AML. Several large-scale studies have confirmed that FLT3/ITD is strongly associated with leukocytosis and a poor prognosis. Although the clinical significance of FLT3/KDM is controversial, the meta-analysis suggests its adverse effect on the outcome. FLT3/ITD is far less common in patients with ALL, whereas FLT3/KDM is recurrently found in patients with ALL, especially in those harboring an MLL gene rearrangement or hyperdiploidy. The overexpression of FLT3 transcripts has been demonstrated in a pro-portion of the AML patients without FLT3 mutations, which are associated with a poor prognosis for overall survival. Routine screening of FLT3 mutations is recommended to stratify the patients into distinct risk groups, while the optimal treatment strategy for patients with FLT3 mutations should be further evaluated.

Tricks of the trade for the appropriate management of newly diagnosed acute promyelocytic leukemia

Most reviews on the state-of-the-art treatment in acute promyelocytic leukemia (APL) have focused mainly on the comparison of therapeutic approaches, including all-trans retinoic acid (ATRA) and chemotherapy. However, outcome of individual patients also depends on appropriate knowledge of several aspects related to APL management that are less appreciated and/or are underestimated in the literature. These aspects include appropriate diagnostic strategy, use of supportive care, early recognition and treatment of life-threatening complications typically associated with APL and its specific treatment, tools and timing for adequate evaluation of response, and, finally, management of the disease in special conditions such as older patients and pregnant women. Besides reviewing current consensus and controversies on the use of ATRA and chemotherapy in the distinct treatment phases (eg, induction, consolidation, maintenance), this article addresses the aforementioned issues on APL management (“tricks of the trade”) with special emphasis on several peculiar aspects that distinguish APL from other acute myeloid leukemias.

Use of arsenic trioxide in haematological malignancies: insight into the clinical development of a novel agent

BACKGROUND

Arsenic trioxide delivers high rates of complete clinical remission in patients with relapsed/refractory acute promyelocytic leukaemia (APL), and is associated with high rates of molecular remission as indicated by PCR negativity for the PML-RARalpha gene.

OBJECTIVE

Mitochondria are considered to be the primary intracellular target of arsenic trioxide, and preclinical and mechanistic studies suggest that this agent may have broad applicability in haematological and other malignancies. Investigations of this agent are ongoing in a range of haematological malignancies, and studies in newly diagnosed APL, acute myeloid leukaemia (AML), myelodysplastic syndromes (MDS), multiple myeloma (MM) and chronic myelogenous leukaemia (CML) are reviewed here using published articles and presentations at international congresses to June 2004. Medline was used to source published preclinical and clinical data, and abstract databases and publications from relevant major international haematology/oncology congresses were searched to source updates of preclinical and clinical trial data.

FINDINGS

Accumulating data indicate that arsenic trioxide may be a useful addition to the therapeutic regimens that have been so successful in treating newly diagnosed APL, and investigations are ongoing to incorporate this agent into the first-line APL treatment paradigm. Preliminary data from clinical studies indicate that arsenic trioxide has clinical activity as a single agent in MDS and MM, and combination therapies are being investigated. In MM, the combination regimens under study incorporate ascorbic acid, which can enhance the efficacy of arsenic trioxide by reducing intracellular glutathione concentrations. In CML, arsenic trioxide is being investigated in combination with imatinib mesylate in patients who have failed initial imatinib treatment. In AML, although results with single-agent arsenic trioxide were not encouraging, treatment using arsenic trioxide in combination with ascorbic acid is a proposed strategy in elderly patients not able to withstand intensive chemotherapy.

CONCLUSION

This versatile agent has a predictable and manageable safety profile and avoids many of the severe toxicities associated with conventional chemotherapies. Ongoing clinical studies will help to define the role of arsenic trioxide in the treatment of haematological malignancies.

Stem cell origin of cancer and differentiation therapy

Our forefathers in pathology, on observing cancer tissue under the microscope in the mid-19th century, noticed the similarity between embryonic tissue and cancer, and suggested that tumors arise from embryo-like cells [Recherches dur le Traitement du Cancer, etc. Paris. (1829); Editoral Archiv fuer pathologische Anatomie und Physiologie und fuer klinische Medizin 8 (1855) 23]. The concept that adult tissues contain embryonic remnants that generally lie dormant, but that could be activated to become cancer was later formalized by Cohnheim [Path. Anat. Physiol. Klin. Med. 40 (1867) 1-79; Virchows Arch. 65 (1875) 64] and Durante [Arch. Memori ed Osservazioni di Chirugia Practica 11 (1874) 217-226], as the "embryonal rest" theory of cancer. An updated version of the embryonal rest theory of cancer is that cancers arise from tissue stem cells in adults. Analysis of the cellular origin of carcinomas of different organs indicates that there is, in each instance, a determined stem cell required for normal tissue renewal that is the most likely cell of origin of carcinomas [Lab. Investig. 70 (1994) 6-22]. In the present review, the nature of normal stem cells (embryonal, germinal and somatic) is presented and their relationships to cancer are further expanded. Cell signaling pathways shared by embryonic cells and cancer cells suggest a possible link between embryonic cells and cancer cells. Wilm's tumors (nephroblastomas) and neuroblastomas are presented as possible tumors of embryonic rests in children. Teratocarcinoma is used as the classic example of the totipotent cancer stem cell which can be influenced by its environment to differentiate into a mature adult cell. The observation that "promotion" of an epidermal cancer may be accomplished months or even years after the initial exposure to carcinogen ("initiation"), implies that the original carcinogenic event occurs in a long-lived epithelial stem cell population. The cellular events during hepatocarcinogenesis illustrate that cancers may arise from cells at various stages of differentiation in the hepatocyte lineage. Examples of genetic mutations in epithelial and hematopoietic cancers show how specific alterations in gene expression may be manifested as maturation arrest of a cell lineage at a specific stage of differentiation. Understanding the signals that control normal development may eventually lead us to insights in treating cancer by inducing its differentiation (differentiation therapy). Retinoid acid (RA) induced differentiation therapy has acquired a therapeutic niche in treatment of acute promyelocytic leukemia and the ability of RA to prevent cancer is currently under examination.

Self-renewal and solid tumor stem cells

Solid tumors arise in organs that contain stem cell populations. The tumors in these tissues consist of heterogeneous populations of cancer cells that differ markedly in their ability to proliferate and form new tumors. In both breast cancers and central nervous system tumors, cancer cells differ in their ability to form tumors. While the majority of the cancer cells have a limited ability to divide, a population of cancer stem cells that has the exclusive ability to extensively proliferate and form new tumors can be identified based on marker expression. Growing evidence suggests that pathways that regulate the self-renewal of normal stem cells are deregulated in cancer stem cells resulting in the continuous expansion of self-renewing cancer cells and tumor formation. This suggests that agents that target the defective self-renewal pathways in cancer cells might lead to improved outcomes in the treatment of these diseases.

Activation of the p70 S6 kinase by all-trans-retinoic acid in acute promyelocytic leukemia cells

Although the mechanisms by which all-trans-retinoic acid (RA) regulates gene transcription are well understood, very little is known on the signaling events regulating RA-dependent initiation of mRNA translation. We examined whether the mammalian target of rapamycin (mTOR)/p70 S6 kinase pathway is activated by RA. RA treatment of sensitive cell lines resulted in phosphorylation/activation of mTOR and downstream induction of p70 S6 kinase activity. Such phosphorylation/activation of p70 S6 kinase was inducible in primary acute promyelocytic leukemia (APL) blasts and RA-sensitive NB-4 cells, but was defective in an NB-4 variant cell line (NB-4.007/6) that is resistant to the biologic effects of RA. The RA-dependent activation of p70 S6 kinase was also phosphatidylinositol 3' kinase (PI3'K)-dependent, and resulted in downstream phosphorylation of the S6 ribosomal protein on Ser235/236 and Ser240/244, events important for initiation of translation for mRNAs with oligopyrimidine tracts in their 5' untranslated region. RA treatment of leukemia cells also resulted in an mTOR-mediated phosphorylation of the 4E-BP1 repressor of mRNA translation, to induce its deactivation and dissociation from the eukaryotic initiation factor-4E (eIF-4E) complex. Altogether, these findings provide evidence for the existence of a novel RA-activated cellular pathway that regulates cap-dependent translation, and strongly suggest that this cascade plays a role in the induction of retinoid responses in APL cells.

Cyclooxygenase-1, but not -2, is upregulated in NB4 leukemic cells and human primary promyelocytic blasts during differentiation

Cyclooxygenase (COX)-1 or -2 and specific prostaglandin (PG) synthases catalyze the formation of various PGs. We investigated the expression and activity of COX-1 and -2 during granulocyte-oriented maturation induced by all-trans-retinoic acid (ATRA) of NB4 cells, originated from a human acute promyelocytic leukemia (APL), and in blasts from APL patients. The expression of COX isoenzymes or prostaglandin synthases was also investigated in circulating granulocytes and human bone marrow. COX-1 was expressed and enzymatically active in NB4 cells and primary blasts. COX-1 mRNA and protein were induced by ATRA. COX-1 protein increased approximately 2-3.5-fold by culture day 3 in NB4 cells and primary blasts, while basal COX-2 expression was very low and unaffected by ATRA. COX-1-dependent PGE(2) biosynthesis increased during differentiation approx. 5-fold. Indomethacin and the selective COX-1 inhibitor SC-560, but not selective COX-2 inhibition, impaired NB4 differentiation, reducing NADPH-oxidase activity, CD11b and CD11c expression. The immunohistochemistry of granulocytes and myeloid precursors in the bone marrow showed a large prevalence of COX-1 as compared to COX-2. In conclusion, COX-1 is induced during ATRA-dependent maturation and appears to contribute to myeloid differentiation both in vitro and ex vivo, and COX-1 activity may potentiate the differentiation of human APL.Leukemia (2004) 18, 1373-1379. doi:10.1038/sj.leu.2403407 Published online 10 June 2004

Acute promyelocytic leukemia: where does it stem from?

A fundamental issue in cancer biology is the identification of the target cell in which the causative molecular lesion arises. Acute myeloid leukemia (AML) is thought to reflect the transformation of a primitive stem cell compartment. The resultant 'cancer stem cells' comprise only a minor portion of the leukemic clone but give rise through differentiation to more committed progenitors as well as differentiated blasts that constitute the bulk of the tumor. The maintenance of the leukemic clone is dependent on the self-renewal capacity of the cancer stem cell compartment, which is revealed by its ability to re-initiate leukemia in a transplant setting. The cellular basis of acute promyelocytic leukemia (APL) is however less clear. APL has traditionally been considered to be the most differentiated form of AML and to arise from a committed myeloid progenitor. Here we review apparently conflicting evidence pertaining to the cellular origins of APL and propose that this leukemia may originate in more than one cellular compartment. This view could account for many apparent inconsistencies in the literature to date. An understanding of the nature of the target cell involved in transformation of APL has important implications for biological mechanism and for clinical treatment.

Targeted therapies in myeloid leukemia

Targeted therapies for hematological malignancies have come of age since the advent of all trans retinoic acid (ATRA) for treating APL and STI571/Imatinib Mesylate/Gleevec for CML. There are good molecular targets for other malignancies and several new drugs are in clinical trials. In this review, we will concentrate on individual abnormalities that exist in the myelodysplastic syndromes (MDS) and myeloid leukemias that are targets for small molecule therapies (summarised in Fig. 1). We will cover fusion proteins that are produced as a result of translocations, including BCR-ABL, the FLT3 tyrosine kinase receptor and RAS. Progression of diseases such as MDS to secondary AML occur as a result of changes in the balance between cell proliferation and apoptosis and we will review targets in both these areas, including reversal of epigenetic silencing of genes such as p15(INK4B).