Further evidence for a non-random chromosomal abnormality in acute promyelocytic leukemia

Understanding, diagnosing, and treating pancreatic cancer from the perspective of telomeres and telomerase

Telomerase is associated with cellular aging, and its presence limits cellular lifespan. Telomerase by preventing telomere shortening can extend the number of cell divisions for cancer cells. In adult pancreatic cells, telomeres gradually shorten, while in precancerous lesions of cancer, telomeres in cells are usually significantly shortened. At this time, telomerase is still in an inactive state, and it is not until before and after the onset of cancer that telomerase is reactivated, causing cancer cells to proliferate. Methylation of the telomerase reverse transcriptase (TERT) promoter and regulation of telomerase by lactate dehydrogenase B (LDHB) is the mechanism of telomerase reactivation in pancreatic cancer. Understanding the role of telomeres and telomerase in pancreatic cancer will help to diagnose and initiate targeted therapy as early as possible. This article reviews the role of telomeres and telomerase as biomarkers in the development of pancreatic cancer and the progress of research on telomeres and telomerase as targets for therapeutic intervention.

History of Developing Acute Promyelocytic Leukemia Treatment and Role of Promyelocytic Leukemia Bodies

The story of acute promyelocytic leukemia (APL) discovery, physiopathology, and treatment is a unique journey, transforming the most aggressive form of leukemia to the most curable. It followed an empirical route fueled by clinical breakthroughs driving major advances in biochemistry and cell biology, including the discovery of PML nuclear bodies (PML NBs) and their central role in APL physiopathology. Beyond APL, PML NBs have emerged as key players in a wide variety of biological functions, including tumor-suppression and SUMO-initiated protein degradation, underscoring their broad importance. The APL story is an example of how clinical observations led to the incremental development of the first targeted leukemia therapy. The understanding of APL pathogenesis and the basis for cure now opens new insights in the treatment of other diseases, especially other acute myeloid leukemias.

History of Acute Promyelocytic Leukemia

In this article, we discuss the history of acute promyelocytic leukemia (APL) from the pre-therapeutic era, which began after its recognition by Hillestad in 1947 as a nosological entity, to the present day. It is a paradigmatic history that has transformed the “most malignant leukemia form” into the most curable one. The identification of a balanced reciprocal translocation between chromosomes 15 and 17, resulting in fusion between the promyelocytic leukemia gene and the retinoic acid receptor alpha, has been crucial in understanding the mechanisms of leukemogenesis, and responsible for the peculiar response to targeted therapy with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). We review the milestones that marked successive therapeutic advances, beginning with the introduction of the first successful chemotherapy in the early 1970s, followed by a subsequent incorporation of ATRA and ATO in the late 1980s and early 1990s which have revolutionized the treatment of this disease. Over the past two decades, treatment optimization has relied on the combination of ATRA, ATO, and chemotherapy according to risk-adapted approaches, which together with improvements in supportive therapy have paved the way for cure for most patients with APL.

STMN1 is highly expressed and contributes to clonogenicity in acute promyelocytic leukemia cells

Stathmin 1 (STMN1) is a microtubule-destabilizing protein highly expressed in hematological malignancies and involved in proliferation and differentiation. Although a previous study found that the PML-RARα fusion protein, which contributes to the pathophysiology of acute promyelocytic leukemia (APL), positively regulates STMN1 at the transcription and protein activity levels, little is known about the role of STMN1 in APL. In this study, we aimed to investigate the STMN1 expression levels and their associations with laboratory, clinical, and genomic data in APL patients. We also assessed the dynamics of STMN1 expression during myeloid cell differentiation and cell cycle progression, and the cellular effects of STMN1 silencing and pharmacological effects of microtubule-stabilizing drugs on APL cells. We found that STMN1 transcripts were significantly increased in samples from APL patients compared with those of healthy donors (all p < 0.05). However, this had no effect on clinical outcomes. STMN1 expression was associated with proliferation- and metabolism-related gene signatures in APL. Our data confirmed that STMN1 was highly expressed in early hematopoietic progenitors and reduced during cell differentiation, including the ATRA-induced granulocytic differentiation model. STMN1 phosphorylation was predominant in a pool of mitosis-enriched APL cells. In NB4 and NB4-R2 cells, STMN1 knockdown decreased autonomous cell growth (all p < 0.05) but did not impact ATRA-induced apoptosis and differentiation. Finally, treatment with paclitaxel (as a single agent or combined with ATRA) induced microtubule stabilization, resulting in mitotic catastrophe with repercussions for cell viability, even in ATRA-resistant APL cells. This study provides new insights into the STMN1 functions and microtubule dynamics in APL.

Co-occurrence and mutual exclusivity: what cross-cancer mutation patterns can tell us

Cancer is the dysregulated proliferation of cells caused by acquired mutations in key driver genes. The most frequently mutated driver genes promote tumorigenesis in various organisms, cell types, and genetic backgrounds. However, recent cancer genomics studies also point to the existence of context-dependent driver gene functions, where specific mutations occur predominately or even exclusively in certain tumor types or genetic backgrounds. Here, we review examples of co-occurring and mutually exclusive driver gene mutation patterns across cancer genomes and discuss their underlying biology. While co-occurring driver genes typically activate collaborating oncogenic pathways, we identify two distinct biological categories of incompatibilities among the mutually exclusive driver genes depending on whether the mutated drivers trigger the same or divergent tumorigenic pathways. Finally, we discuss possible therapeutic avenues emerging from the study of incompatible driver gene mutations.

Synthetic cyclopenta[b]indoles exhibit antineoplastic activity by targeting microtubule dynamics in acute myeloid leukemia cells

Acute promyelocytic leukemia (APL) is associated with PML-RARα oncogene, which is treated using all-trans retinoic acid (ATRA)-based chemotherapy. However, chemoresistance is observed in 20-30% of treated patients and represents a clinical challenge, raising the importance of the development of new therapeutic options. In the present study, the effects of three synthetic cyclopenta[b]indoles on the leukemia phenotype were investigated using NB4 (ATRA-sensitive) and NB4-R2 (ATRA-resistant) cells. Among the tested synthetic cyclopenta[b]indoles, compound 2, which contains a heterocyclic nucleus, was the most active, presenting time-dependent cytotoxic activity in the μM range in APL cells, without cytotoxicity for normal leukocytes, and was selected for further characterization. Compound 2 significantly decreased clonogenicity, increased apoptosis, and caused cell cycle arrest at S and G₂/M phases in a drug concentration-dependent manner. Morphological analyses indicated aberrant mitosis and diffuse tubulin staining upon compound 2 exposure, which corroborates cell cycle findings. In the molecular scenario, compound 2 reduced STMN1 expression and activity, and induced PARP1 cleavage and H2AX and CHK2 phosphorylation, and modulated CDKN1A, PMAIP1, GADD45A, and XRCC3 expressions, indicating reduction of cell proliferation, apoptosis, and DNA damage. Moreover, in the in vivo tubulin polymerization assay, NB4 and NB4-R2 cells showed a reduction in the levels of polymerized tubulin upon compound 2 exposure, which indicates tubulin as a target of the drug. Molecular docking supports this hypothesis. Taken together, these data indicated that compound 2 exhibits antileukemic effects through disrupting the microtubule dynamics, identifying a possible novel potential antineoplastic agent for the treatment of ATRA-resistant APL.

Genotypic and Phenotypic Characteristics of Acute Promyelocytic Leukemia Translocation Variants

Acute promyelocytic leukemia (APL) is a special disease entity of acute myeloid leukemia (AML). The clinical use of all-trans retinoic acid (ATRA) has transformed APL into the most curable form of AML. The majority of APL cases are characterized by the fusion gene PML-RARA. Although the PML-RARA fusion gene can be detected in almost all APL cases, translocation variants of APL have been reported. To date, this is the most comprehensive review of these translocations, discussing 15 different variants. Reviewed genes involved in APL variants include: ZBTB16, NPM, NuMA, STAT5b, PRKAR1A, FIP1L1, BCOR, NABP1, TBLR1, GTF2I, IRF2BP2, FNDC3B, ADAMDTS17, STAT3, and TFG. The genotypic and phenotypic features of APL translocations are summarized. All reported studies were either case reports or case series indicating the rarity of these entities and limiting the ability to drive conclusions regarding their characteristics. However, reported variants have shown variable clinical and morphological features, with diverse responsiveness to ATRA.

The Impact of Next-Generation Sequencing on Cancer Genomics: From Discovery to Clinic

The application of next-generation sequencing (NGS) technology to the study of cancer genomes has been transformational. Not only has this technology revealed the genetic and epigenetic underpinnings of disease onset and progression, but also has redefined our clinical diagnosis and treatment paradigms. This rapid translation from discovery to clinical platform has occurred in the context of new pharmaceutical paradigms, enabling the use of NGS for the diagnosis and definition of therapeutic vulnerabilities of cancer. This review explores this transformation and identifies cutting-edge applications of NGS that will result in its additional utility in cancer care.

Challenges and Chances in the Preclinical to Clinical Translation of Anticancer Metallodrugs

Despite being “sentenced to death” for quite some time, anticancer platinum compounds are still the most frequently prescribed cancer therapies in the oncological routine and recent exciting news from late-stage clinical studies on combinations of metallodrugs with immunotherapies suggest that this situation will not change soon. It is perhaps surprising that relatively simple molecules like cisplatin, discovered over 50 years ago, are still widely used clinically, while none of the highly sophisticated metal compounds developed over the last decade, including complexes with targeting ligands and multifunctional (nano)formulations, have managed to obtain clinical approval. In this book chapter, we summarize the current status of ongoing clinical trials for anticancer metal compounds and discuss the reasons for previous failures, as well as new opportunities for the clinical translation of metal complexes.

Sequencing the AML genome, transcriptome, and epigenome

Leukemia is a disease that develops as a result of changes in the genomes of hematopoietic cells, a fact first appreciated by microscopic examination of the bone marrow cell chromosomes of affected patients. These studies revealed that specific subtypes of leukemia diagnoses correlated with specific chromosomal abnormalities, such as the t(15;17) of acute promyelocytic leukemia and the t(9;22) of chronic myeloid leukemia. Over time, our genomic characterization of hematologic malignancies has moved beyond the resolution of the microscope to that of individual nucleotides in the analysis of whole-genome sequencing (WGS) data using state-of-the-art massively parallel sequencing (MPS) instruments and algorithmic analyses of the resulting data. In addition to studying the genomic sequence alterations that occur in patients' genomes, these same instruments can decode the methylation landscape of the leukemia genome and the resulting RNA expression landscape of the leukemia transcriptome. Broad correlative analyses can then integrate these 3 data types to better inform researchers and clinicians about the biology of individual acute myeloid leukemia (AML) cases, facilitating improvements in care and prognosis.

Human acute promyelocytic leukemia NB4 cells are sensitive to esculetin through induction of an apoptotic mechanism

Acute promyelocytic leukemia (APL) is a type of cancer, in which immature cells called promyelocytes proliferate abnormally. Human NB4 cell line appears to be a suitable in vitro model to express the characteristics of APL. In this work, we have investigated the effects of esculetin, a coumarin derivative with antioxidant properties, on the viability, the induction of apoptosis and the expression of apoptotic factors in NB4 cells. Cells treated with esculetin at several concentrations (20-500 μM) and for different times (5-24 h) showed a concentration- and time-dependent viability decrease with increased subdiploid DNA production. Esculetin inhibited cell cycle progression and induced DNA fragmentation. Moreover, annexin-V-FITC cytometry assays suggested that increased toxicity is due to both early and late apoptosis. This apoptosis process is be mediated by activation of caspase-3 and caspase-9. Treatments with progressively increasing concentrations (from 100 μM to 500 μM) of esculetin produced a reduction of Bcl2/Bax ratio in NB4 cells at 19 h, without affecting p53 levels. Proapoptotic action of esculetin involves the ERK MAP kinase cascade since increased levels of phosphorylated ERK were observed after those treatments. Increments in the levels of phosphorylated-Akt were also observed. Additionally, esculetin induced the loss of mitochondrial membrane potential with a release of cytochrome c into the cytosol which starts at 6 h of treatment with esculetin and increases up to 24 h. Esculetin induced an increase in superoxide anion at long times of treatment and a reduction of peroxides at short times (1 h) with an observed increase at 2-4 h of treatment. No significant changes in NO production was observed. Esculetin reduced the GSH levels in a time-dependent manner. In summary, the present work shows the cytotoxic action of esculetin as an efficient tool to study apoptosis mechanism induction on NB4 cell line used as a relevant model of APL disease.

RARA fusion genes in acute promyelocytic leukemia: a review

The t(15;17)(q24;q21), generating a PML-RARA fusion gene, is the hallmark of acute promyelocytic leukemia (APL). At present, eight other genes fusing with RARA have been identified. The resulting fusion proteins retain domains of the RARA protein allowing binding to retinoic acid response elements (RARE) and dimerization with the retinoid X receptor protein (RXRA). They participate in protein-protein interactions, associating with RXRA to form hetero-oligomeric complexes that can bind to RARE. They have a dominant-negative effect on wild-type RARA/RXRA transcriptional activity. Moreover, RARA fusion proteins can homodimerize, conferring the ability to regulate an expanded repertoire of genes normally not affected by RARA. RARA fusion proteins behave as potent transcriptional repressors of retinoic acid signalling, inducing a differentiation blockage at the promyelocyte stage which can be overcome with therapeutic doses of ATRA or arsenic trioxide. However, resistance to these two drugs is a major problem, which necessitates development of new therapies.

Apoptosis induced by paclitaxel via Bcl-2, Bax and caspases 3 and 9 activation in NB4 human leukaemia cells is not modulated by ERK inhibition

We have studied the role of pivotal bio-molecules involved in signalling of cytotoxic effects induced by paclitaxel (Ptx) on acute promyelocytic human leukaemia NB4 cells. A time-dependent increase in cell death and DNA cleavage was observed after 30μM Ptx treatment. Cell death induction by Ptx proceeds mainly as programmed cell death as shown by annexin V-FITC, reaching up to 30% of apoptotic cells after 24h. Significant reductions of p53, changes in Bax and Bcl-2 and activation of caspases 3 and 9 were observed as the treatment was applied for long times. Ptx treatments produced NFkB depletion with expression levels abolished at 19h what could be involved in reduction of survival signals. Phosphorylation of intracellular kinases showed that pERK1/2 decreased significantly at 19h of Ptx treatment. When these cells were preincubated for 90min with 20μM PD98059, 2'-amino-3'-methoxyflavone, an inhibitor of ERK phosphorylation, a slight reduction of cell viability was observed in comparison to that produced by Ptx alone. Pretreatment with PD98059 neither activated caspases nor significantly increased the apoptotic effect of Ptx. Taken together, our data reveal that the inhibition of ERK phosphorylation does not seem to be an essential pathway for bursting an increased induction of apoptosis by Ptx. Decrease of p53 and Bcl-2, fragmentation of DNA, increase of Bax and, finally, activation of caspases 3 and 9 in NB4 leukaemia cells make the apoptotic process induced by Ptx irreversible. Application of Ptx in leukaemia cells shows therefore a promising potential with particular effects on different leukaemia cell types.

The origin and evolution of mutations in acute myeloid leukemia

Most mutations in cancer genomes are thought to be acquired after the initiating event, which may cause genomic instability and drive clonal evolution. However, for acute myeloid leukemia (AML), normal karyotypes are common, and genomic instability is unusual. To better understand clonal evolution in AML, we sequenced the genomes of M3-AML samples with a known initiating event (PML-RARA) versus the genomes of normal karyotype M1-AML samples and the exomes of hematopoietic stem/progenitor cells (HSPCs) from healthy people. Collectively, the data suggest that most of the mutations found in AML genomes are actually random events that occurred in HSPCs before they acquired the initiating mutation; the mutational history of that cell is "captured" as the clone expands. In many cases, only one or two additional, cooperating mutations are needed to generate the malignant founding clone. Cells from the founding clone can acquire additional cooperating mutations, yielding subclones that can contribute to disease progression and/or relapse.

Applying next-generation sequencing to pancreatic cancer treatment

Pancreatic cancer is a highly lethal malignancy that presents multiple technical challenges for genomic studies. Next-generation sequencing and its applications have proven successful in the study of other tumour types, unravelling the interplay between DNA and RNA changes that are unique to the tumour. This Review outlines the genomic studies performed to date that have explored the somatic alterations of pancreatic cancer genomes, setting the stage for the introduction of our current technological capabilities. In spite of several challenging aspects posed by pancreatic tumours in particular and clinical sequencing-based diagnostics in general, next-generation sequencing and analysis can now be used in experiments relating to the treatment of patients with this disease. As a means to improve patient outcomes, the application of comprehensive next-generation sequencing and analysis to the genomes of patients with pancreatic cancer to identify therapeutic options is proposed.

Genome sequencing and cancer

New technologies for DNA sequencing, coupled with advanced analytical approaches, are now providing unprecedented speed and precision in decoding human genomes. This combination of technology and analysis, when applied to the study of cancer genomes, is revealing specific and novel information about the fundamental genetic mechanisms that underlie cancer's development and progression. This review outlines the history of the past several years of development in this realm, and discusses the current and future applications that will further elucidate cancer's genomic causes.

B30.2/SPRY domain in tripartite motif-containing 22 is essential for the formation of distinct nuclear bodies

Tripartite motif-containing 22 (TRIM22) is an important antiviral protein that forms distinct nuclear bodies (NB) in many cell types. This study aims to identify functional domains/residues for TRIM22's nuclear localization and NB formation. Deletion of the really-interesting-new-gene (RING) domain, which is essential for its antiviral property, abolished TRIM22 NB formation. However, mutation of two critical residues Cys15 and Cys18 to alanine in the RING domain, did not affect NB formation notably. Although the deletion of the putative bipartite nuclear localization signal (NLS) abolished TRIM22 localization and NB formation, the B30.2/SplA and ryanodine receptor (SPRY) domain, and residues 491-494 specifically are also essential for nuclear localization and NB formation.

Sensitivity to sodium arsenite in human melanoma cells depends upon susceptibility to arsenite-induced mitotic arrest

Arsenic induces clinical remission in patients with acute promyelocytic leukemia and has potential for treatment of other cancers. The current study examines factors influencing sensitivity to arsenic using human malignant melanoma cell lines. A375 and SK-Mel-2 cells were sensitive to clinically achievable concentrations of arsenite, whereas SK-Mel-3 and SK-Mel-28 cells required supratherapeutic levels for toxicity. Inhibition of glutathione synthesis, glutathione S-transferase (GST) activity, and multidrug resistance protein (MRP) transporter function attenuated arsenite resistance, consistent with studies suggesting that arsenite is extruded from the cell as a glutathione conjugate by MRP-1. However, MRP-1 was not overexpressed in resistant lines and GST-pi was only slightly elevated. ICP-MS analysis indicated that arsenite-resistant SK-Mel-28 cells did not accumulate less arsenic than arsenite-sensitive A375 cells, suggesting that resistance was not attributable to reduced arsenic accumulation but rather to intrinsic properties of resistant cell lines. The mode of arsenite-induced cell death was apoptosis. Arsenite-induced apoptosis is associated with cell cycle alterations. Cell cycle analysis revealed arsenite-sensitive cells arrested in mitosis whereas arsenite-resistant cells did not, suggesting that induction of mitotic arrest occurs at lower intracellular arsenic concentrations. Higher intracellular arsenic levels induced cell cycle arrest in the S-phase and G(2)-phase in SK-Mel-3 and SK-Mel-28 cells, respectively. The lack of arsenite-induced mitotic arrest in resistant cell lines was associated with a weakened spindle checkpoint resulting from reduced expression of spindle checkpoint protein BUBR1. These data suggest that arsenite has potential for treatment of solid tumors but a functional spindle checkpoint is a prerequisite for a positive response to its clinical application.

Retinoic acid-induced CD38 antigen promotes leukemia cells attachment and interferon-gamma/interleukin-1beta-dependent apoptosis of endothelial cells: implications in the etiology of retinoic acid syndrome

All-trans retinoic acid (RA) treatment of patients with acute promyelocytic leukemia (APL) induces complete remission in more than 90% of the cases. Although RA therapy is well tolerated, about 25% of APL patients develop a potentially fatal condition called retinoic acid syndrome (RAS). Molecular mechanisms underlying the development of RAS pathogenesis, especially those that result in the damage of endothelial cells remain elusive. In the present study, we found that RA treatment induces the expression of interferon-gamma (IFN-gamma) and interleukin-1beta (IL-1beta) in peripheral blast cells from APL patients. IFN-gamma and IL-1beta also exerted synergistic effect in driving human umbilical cord endothelial cells (HUVECs) and human lung microvascular endothelial cells (HLMVECs) into apoptosis. RA also upregulated the expression of CD38, an ectoenzyme responsible for the generation of the calcium messenger cyclic ADP-ribose. Importantly, RA-induced CD38 expression promoted strong attachment of leukemia cells to endothelial cells, and incubation of endothelial cells with either high concentration (100 ng/ml) of IFN-gamma alone or low concentration of IL-1beta and IFN-gamma (10 ng/ml, each) induced strong apoptotic responses as revealed by caspase-8 activation and DNA fragmentation. Our results suggest that these RA-induced events could contribute to the development of RAS pathogenesis in patients with APL.

Distinct effects of different concentrations of sodium selenite on apoptosis, cell cycle, and gene expression profile in acute promyeloytic leukemia-derived NB4 cells

Selenium at a low concentration has a chemopreventive role against cancer, while at a high concentration, it exerts a direct antitumor effect. However, the mechanisms remain elusive. In this article, we discovered that Na(2)SeO(3) at 20 micromol/l concentration could significantly inhibit the proliferation of NB4 cells, affect the cell cycle distribution of cell population, and induce cellular changes characteristic of apoptotic cells, while this same compound at 2 micromol/l concentration had no such effects. The mechanisms underlying these overt differences caused by treatment of different concentrations of selenium were further investigated. cDNA microarray analysis showed that after treatment by 20 micromol/l Na(2)SeO(3), 34 genes were changed in expression, while treatment by 2 micromol/l Na(2)SeO(3) resulted in the changes of 29 genes. Nine genes were regulated in both groups, among which three showed opposite changes caused by 2 and 20 micromol/l Na(2)SeO(3). The majority of regulated genes did not coincide between the two experiment groups. In conclusion, 2 and 20 micromol/l Na(2)SeO(3) could have different effects on NB4 cells, and some genes might be involved in the underlying mechanisms. Our findings could provide basis for further uncovering the molecular mechanisms of the chemopreventive and antitumor effects of selenium and, in turn, for probing the rationality of treating leukemia with selenium.

Clinical implications of advanced molecular cytogenetics in cancer

The field of cytogenetics has already entered the molecular era and a rapid expansion of its contribution is seen in genomic disease management. Among the evolving advanced molecular techniques, with an impeccable balance of high specificity, sensitivity and assay rapidity, fluorescence in situ hybridization has made its home in routine clinical laboratory. Today, its clinical application is vivid in every phase of disease management of a number of malignancies. The rapid growth in the knowledge of specific associations between distinct chromosomal abnormalities and different types of cancers will necessitate simultaneous detection of multiple abnormalities using multicolor/multiplex fluorescence in situ hybridization tests more often in the near future. Also, as the human genome sequence is ascertained, genome-wide screening with microarray technology will gain eminence in the clinical scenario, yield better solutions and bring the concept of personalized medicine in cancer closer to reality than ever before.

Myeloid leukemia with promyelocytic features in transgenic mice expressing hCG-NuMA-RARalpha

Acute promyelocytic leukemia (APL) is characterized by the accumulation of abnormal promyelocytes in the bone marrow (BM), and by the presence of a reciprocal chromosomal translocation involving retinoic acid receptor alpha (RARalpha). To date, five RARalpha partner genes have been identified in APL. NuMA-RARalpha was identified in a pediatric case of APL carrying a translocation t(11;17)(q13;q21). Using a construct containing the NuMA-RARalpha fusion gene driven by the human cathepsin G promoter (hCG-NuMA-RARalpha), two transgenic mouse lines were generated. Transgenic mice were observed to have a genetic myeloproliferation (increased granulopoiesis in BM) at an early age, and rapidly developed a myeloproliferative disease-like myeloid leukemia. This leukemia was morphologically and immunophenotypically indistinguishable from human APL, with a penetrance of 100%. The phenotype of transgenic mice was consistent with a blockade of neutrophil differentiation. NuMA-RARalpha is therefore sufficient for disease development in this APL model.

Advances in the management of acute promyelocytic leukemia and other hematologic malignancies with arsenic trioxide

Acute promyelocytic leukemia (APL), once considered the most devastating subtype of acute myeloid leukemia, is now the most treatable of all subtypes as a result of intensive research into its molecular pathogenesis. This research has led to a rational approach to treatment in which the use of the differentiating agent all-trans-retinoic acid (ATRA) has proven to be effective first-line treatment for inducing complete remission. Arsenic trioxide (ATO) is currently used to treat relapsed disease, further enhancing survival rates in a patient population for which limited salvage options exist. This review discusses the molecular mechanisms responsible for development of APL and the evolution of treatment options over the last three decades, including the major advances using ATRA and ATO in the last 12 years. The mechanism of action of ATO is also described in view of this agent's potential for broader therapeutic application in a variety of hematologic malignancies.

Antigen expression patterns reflecting genotype of acute leukemias

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.

Retinoid therapy of childhood cancer

In vitro studies that showed RA could cause growth arrest and differentiation of myelogenous leukemia and neuroblastoma led to clinical trials of retinoids in APL and neuroblastoma that increased survival for both of those diseases. In the case of APL, ATRA has been the drug of choice, and preclinical and clinical data support direct combinations of ATRA with cytotoxic chemotherapy. For neuroblastoma, a phase I study defined a dose of 13-cis-RA, which was tolerable in patients after myeloablative therapy, and a phase III trial that showed postconsolidation therapy with 13-cis-RA improved EFS for patients with high-risk neuroblastoma. Preclinical studies in neuroblastoma indicate that ATRA or 13-cis-RA can antagonize cytotoxic chemotherapy and radiation, so use of 13-cis-RA in neuroblastoma is limited to maintenance after completion of cytotoxic chemotherapy and radiation. A limitation on the antitumor benefit of ATRA in APL is the marked decrease in drug levels that occurs during therapy as a result of induction of drug metabolism, resulting in a shorter drug half-life and decreased plasma levels. Although early studies sought to overcome the pharmacologic limitations of ATRA therapy in APL, the demonstration that ATO is active against APL in RA-refractory patients has led to a focus on studies employing ATO. Use of 13-cis-RA in neuroblastoma has avoided the decreased plasma levels seen with ATRA. It is likely that recurrent disease seen during or after 13-cis-RA therapy in neuroblastoma is due to tumor cell resistance to retinoid-mediated differentiation induction. Studies in neuroblastoma cell lines resistant to 13-cis-RA and ATRA have shown that they can be sensitive, and in some cases collaterally hypersensitive, to the cytotoxic retinoid fenretinide. Fenretinide induces tumor cell cytotoxicity rather than differentiation, acts independently from RA receptors, and in initial phase I trials has been well tolerated. Clinical trials of fenretinide, alone and in combination with ceramide modulators, are in development.

Clinical experience of arsenic trioxide in relapsed acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) has unique clinical, cytogenetic, and molecular features and is one of the most potentially curable human malignancies. The current standard treatment given to patients with newly diagnosed APL consists of all-trans retinoic acid and anthracycline-based cytotoxic chemotherapy, which is highly effective for remission induction. However, despite the potential for cure with existing treatments, approximately 20%-30% of patients relapse and require salvage therapy. Reports of the safety and efficacy of arsenic trioxide from centers in China led to a pivotal trial of this agent in the United States for patients with relapsed APL. In an initial pilot study, 11 of 12 patients experienced a complete response, and a subsequent multicenter trial confirmed the efficacy and safety of arsenic trioxide for remission induction in this patient population. Additional trials are under way to evaluate the use of this agent alone or as part of a chemotherapy regimen for consolidation and maintenance of patients with APL.

Interactions of herpes simplex virus type 1 with ND10 and recruitment of PML to replication compartments

Many of the events required for productive herpes simplex virus type 1 (HSV-1) infection occur within globular nuclear domains called replication compartments, whose formation appears to depend on interactions with cellular nuclear domains 10 (ND10). We have previously demonstrated that the formation of HSV-1 replication compartments involves progression through several stages, including the disruption of intact ND10 (stage I to stage II) and the formation of PML-associated prereplicative sites (stage III) and replication compartments (stage IV) (J. Burkham, D. M. Coen, and S. K. Weller, J. Virol. 72:10100-10107, 1998). In this paper, we show that some, but not all, PML isoforms are recruited to stage III foci and replication compartments. Genetic experiments showed that the recruitment of PML isoforms to stage III prereplicative sites and replication compartments requires the localization of the HSV-1 polymerase protein (UL30) to these foci but does not require polymerase catalytic activity. We also examined the stages of viral infection under conditions affecting ND10 integrity. Treatment with factors that increase the stability of ND10, arsenic trioxide and the proteasome inhibitor MG132, inhibited viral disruption of ND10, formation of replication compartments, and production of progeny virus. These results strengthen the previously described correlation between ND10 disruption and productive viral infection.

Molecular genetics in acute leukemia

Improved techniques in identifying the chromosome changes and the affected genes that are involved in acute leukemias have led to improved treatments for these diseases. Identification of consistent chromosomal changes has allowed us to target the location of particular genes and has enabled us to focus our treatments more specifically to certain subtypes of leukemia. Translocations, in particular, are common cytogenetic abnormalities in human leukemia, and the prevalence of certain types of translocations varies with age. Cancers, lymphomas and leukemias are now known to be genetic diseases and it is recognized that genotype-specific therapies should be used that take into account the genetic alterations of the particular leukemia.

Advances in cancer cytogenetics

As the end of the millenium approaches, recognition of the milestones achieved in the field of cancer cytogenetics is mandatory. With regard to cancer cytogenetics, the turning century can be divided in three main era: the pre-banding period that has posed important hypothesis and technical premises, the fruitful banding era that led to the discovery of the critical chromosomal rearrangements and cloning of cancer genes and the more recent revolutionizing era of molecular cytogenetics where technological advances permit a global visualization and high-level resolution of chromosomal alterations. J. Cell. Biochem. Suppls. 32/33:173-182, 1999.

Glucocorticoids induce apoptosis in acute myeloid leukemia cell lines with A t(8;21) chromosome translocation

The t(8;21) chromosome translocation frequently occurs in the AML, acute myeloid leukemia, M2 sub-type. This translocation juxtaposes the AML1 gene on chromosome 21 with the MTG8(ETO) gene on chromosome 8, resulting in the expression of the AML1-MTG8(ETO) fusion transcript. The fusion product is thought to play a critical role in the abnormal proliferation and differentiation of myeloid leukemia cells. We investigated the effects of various differentiation inducers of myeloid leukemia cells on the growth and differentiation of Kasumi-1 and SKNO-1 cells, AML cell lines with t(8;21). These cells resisted differentiation into mature granulocytes and macrophages in response to various inducers of myelomonocytic differentiation, such as dimethyl sulfoxide, retinoic acid, butyrate, 12-O-tetradecanoylphorbol-13-acetate (TPA) and 1alpha,25-dihydroxyvitamin D3. On the other hand, dexamethasone can induce apoptosis in these cells at low concentrations, whereas other myelomonocytic leukemia cell lines tested were resistant to glucocorticoid-induced apoptosis. The levels of glucocorticoid receptor gene expression were high in Kasumi-1 and SKNO-1 cells. Expression of the AML1-MTG8(ETO), bcl-2, and c-myc genes was unchanged following exposure to dexamethasone. Glucocorticoids might induce the apoptosis of some types of AML cells, just like that of some lymphoid leukemia cells.

More detailed characterization of some of the HL60 karyotypic features by fluorescence in situ hybridization

We performed a focused chromosome analysis on the HL60 cell line by multicolor fluorescence in situ hybridization (FISH), using probes for the unequivocal identification of specific chromosome regions and subregions. The purpose of this karyotypic re-evaluation was to confirm and to characterize in more detail chromosome rearrangements already identified by means of classic cytogenetic approaches and recurrently detected from the initial establishment of the cell line. The observations reported may help reassess the potential of the HL60 cell line in understanding the molecular events underlying the non-random karyotype alterations associated with acute myeloid leukemias (AML).

Myeloperoxidase gene expression in normal granulopoiesis and acute leukemias

Myeloperoxidase (MPO) is an abundant heme protein found in granulocytes and monocytes, which plays an important role in host defense against infection. MPO enzyme activity as determined by light microscopic cytochemistry has long been an important marker used in the diagnosis of acute leukemias and other hematopoietic disorders. Recently, MPO expression has been studied at the electron microscopic level, and monoclonal antibodies (mAbs) against MPO protein have been developed. Furthermore, techniques and probes for analysing MPO expression at the RNA level are now available. This has made possible more extensive studies of MPO expression in a wide range of neoplastic and preneoplastic blood disorders. This review will discuss the fundamental biology of MPO as well as recent developments in our understanding of MPO expression in leukemic cells and cell lines of various lineages.

Cytogenetics in acute myeloid leukaemia

A wealth of literature spanning 20 years describing cytogenetic abnormalities in acute myeloid leukaemia (AML) already exists. It ranges from single case reports of unusual abnormalities to large multicentre studies of hundreds of cases. A landmark publication was the Fourth International Workshop on Chromosomes in Acute Leukaemia which established a base line for diagnosis, prognosis and frequency of chromosome abnormalities in AML. Two large sources of information are a book, 'The Chromosomes in Human Cancer and Leukemia' and a catalogue of chromosome abnormalities, which aims to list all chromosome abnormalities described in the scientific and medical literature from 1973, when the widespread use of banding techniques, enabled the precise definition of the chromosome breakpoints. In this review the common cytogenetic abnormalities seen in AML with reference to associations with the French-American-British (FAB) classification, their possible prognostic significance and their associated molecular biology are summarized.

Clinical aspects of acute myeloid leukemias of the FAB types M3 and M4Eo. The AML Cooperative Group

Acute promyelocytic leukemia (AML FAB M3, APL) and acute myelomonocytic leukemia with abnormal eosinophils (AML M4Eo) are considered distinct entities with characteristic clinical, morphological, cytogenetic, and prognostic features. Promyelocytic leukemia is characterized by abnormal promyelocytes replacing normal hematopoiesis associated with a translocation between the long arms of chromosomes 15 and 17 t (15; 17), severe coagulopathy, and responsiveness to all-trans retinoic acid (tretinoin). Characteristic features of AML M4Eo are a myelomonocytic marrow infiltration, eosinophils with abnormal immature granules positive for chloroacetate esterase, an inversion or translocation of chromosome 16, and an increased risk of meningeal relapses. Prognosis of both types of AML has been reported to be better than prognosis of the other entities combined. Since most of the published data were collected from heterogeneous patient populations treated with various chemotherapeutic regimens, we have analyzed treatment outcome of AML M3 and M4Eo in the AMLCG-85 study for patients younger than 60 years. For the total population of 594 patients of this study, CR rate was 68.89%, early death rate 11.60%, and no or partial remission was achieved in 19.51% of the cases. Of 40 patients with AML M3 or M3 v complete remission was attained in 62.5%. Nine patients died within 42 days after the start of antileukemic therapy (22.5%). Of these nine, four died because of infection, five because of bleeding. Relapse-free survival rate was 59% after 3 years, significantly better than the respective curve of the other FAB types combined (35% after 3 years). In AML M4Eo, 91.7% of the 24 patients reached complete remission. The early death rate was 8.3%. No case of nonresponse was seen. Relapse-free survival rate was 49% after 3 years compared with 35% for the other types combined.

Molecular analysis of the t(15;17) translocation in acute promyelocytic leukaemia

APL (FAB M3) is a unique type of myeloid leukaemia characterized by specific clinical, morphological, cytogenetic and molecular features. An early and accurate diagnosis is necessary to initiate therapy and treat the life-threatening coagulopathy caused by release of procoagulants from the abundant promyelocytic granules. Cytogenetically the disease is characterized by a reciprocal translocation between the long arms of chromosomes 15 and 17, t(15;17)(q21;q22), which is seen in almost every patient with APL but in no other form of malignancy. The presence of this translocation, often as the only karyotypic change, suggests that potentially leukaemogenic sequences are located at the breakpoints and are activated by rearrangement. The recent cloning of the breakpoints by three groups has demonstrated that the retinoic acid receptor alpha gene (RARA) on chromosome 17 is fused to a previously undescribed transcription factor gene, PML, on chromosome 15. The DNA-binding motifs of both the RARA and PML proteins, together with the ligand-binding domain of RARA, are combined in a single fusion protein which may dysregulate either retinoic acid or PML-sensitive pathways. Identification of these dysregulated target genes has become the next molecular goal for research on APL. Intriguingly, some APLs not only express the PML-RARA fusion protein but also the reciprocal RARA-PML fusion protein, although the contribution of this product is unclear. The PML-RARA chimaeric protein is presumably the target during the striking differentiation therapy achieved with all-trans retinoic acid. This therapy induces the malignant promyelocytes to mature and die, rather than continue proliferating. Moreover, it represents the first direct connection between a genetic defect and clinical treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosomal translocation t(15;17) in human acute promyelocytic leukemia fuses RAR alpha with a novel putative transcription factor, PML

A unique mRNA produced in leukemic cells from a t(15;17) acute promyelocytic leukemia (APL) patient encodes a fusion protein between the retinoic acid receptor alpha (RAR alpha) and a myeloid gene product called PML. PML contains a cysteine-rich region present in a new family of apparent DNA-binding proteins that includes a regulator of the interleukin-2 receptor gene (Rpt-1) and the recombination-activating gene product (RAG-1). Accordingly, PML may represent a novel transcription factor or recombinase. The aberrant PML-RAR fusion product, while typically retinoic acid responsive, displays both cell type- and promoter-specific differences from the wild-type RAR alpha. Because patients with APL can be induced into remission with high dose RA therapy, we propose that the nonliganded PML-RAR protein is a new class of dominant negative oncogene product. Treatment with RA would not only relieve this inhibition, but the activated PML-RAR protein may actually promote myelocyte differentiation.

Chromosomal localization of the human myeloperoxidase gene by in situ hybridization using oligonucleotide probes

Oligonucleotide probes have been used to map the myeloperoxidase (MPO) gene locus to chromosome bands 17q21-22. This is in agreement with results reported using conventional cDNA probes. No evidence for the existence of a second MPO gene locus was obtained. Six synthetic 72-base oligonucleotides, corresponding to different exon regions of the MPO gene, were tritium-labeled and used as in situ hybridization probes. Synthetic oligonucleotide probes offer a useful alternative to conventional DNA probes for gene mapping.

Cloning and characterization of the t(15;17) translocation breakpoint region in acute promyelocytic leukemia

A reciprocal chromosomal translocation, t(15;17)(q22;q11.2-12), is characteristic of acute promyelocytic leukemia (APL) of French-American-British (FAB) subtype M3, and is not associated with any other human malignancy. The non-random pattern of the APL translocations suggests that specific genes on chromosomes 15 and 17 are somehow altered or deregulated as a consequence of the rearrangement. Translocation breakpoints in APL patients provide physical landmarks that suggest an approach to isolating the APL gene(s). Genetic and physical maps constructed for the APL breakpoint region on chromosome 17 have indicated that two fully-linked DNA markers, defining loci for THRA1 and D17S80, map to opposite sides of an APL breakpoint yet reside on a common 350-kb Clal fragment. Cosmid-walking experiments to clone this APL breakpoint have revealed a 38-kilobase deletion on chromosome 17. Studies in additional APL patients have shown that the breakpoint region on chromosome 17 spans at least 80 kilobases.

Chromosomal damage induced by human adenovirus type 12 requires expression of the E1B 55-kilodalton viral protein

Infection of human embryonic kidney cells with adenovirus type 12 results in the induction of damage at specific (17q21-22, 1p36, 1q21, and 1q42-43) and random sites in the cellular chromosomes. A previous study by Durnam et al. (D. M. Durnam, P. P. Smith, J. C. Menninger, and J. K. McDougall, Cancer Cells 4:349-354, 1986) indicated that the expression of viral early region 1 (E1) is sufficient for the induction of damage at band 17q21-22. In the present report we used an adenovirus type 12-adenovirus type 5 recombinant with E1A hybrid sequences as well as viruses with mutations in the adenovirus type 12 E1B genes to map adenovirus type 12 E1 functions involved in the induction of genetic damage. Our results show that the expression of the E1A proteins is not sufficient for this effect. On the other hand, mutations within the E1B 55-kilodalton protein but not the E1B 19-kilodalton protein affect the ability of the virus to induce both specific and random chromosomal damage.

Cytogenetic abnormalities in cancer: with special emphasis on tumor heterogeneity

There is a considerable amount of cytogenetic data available to support the statements that (1) cancer is a genetic disease; (2) most cancers are monoclonal in origin; (3) tumor cells are more genetically unstable than normal cells; (4) the genetic instability may be inherited, acquired, or both during the lifespan of the individual tumor; (5) tumor metastasis is a nonrandom, controlled process, and clonal in origin; (6) malignant tumors are genetically heterogeneous and contain multiple subpopulations that may differ in their biological properties; (7) some tumors might be difficult to treat successfully because of their resistant nature; and (8) tumor cells may acquire resistance because of gene amplification. For these reasons it is extremely important to study the biology of malignant tumor cells in order to determine their effective treatments and control this dreadful disease.

Overexpression of the MPO gene occurring in a case of APL without unusual genotypic characteristics

Northern blot analysis of four typical cases of acute promyelocytic leukemia showed that one of the cell population examined was characterized by a very high level of expression of the myeloperoxidase (MPO) gene. Western blot analysis confirms that the protein content of the cells corresponded to the levels of the MPO mRNA. Southern blot studies of the DNA of this cell population ruled out the presence of any genome amplification or rearrangement. Chromosome hybridization studies in situ confirmed that the MPO gene was translocated on the long arm of chromosome 15. The observation that a typical genomic pattern may or may not be associated with the MPO overexpression leads us to believe that so far it is impossible to reach any conclusion about the significance of the translocation in the genesis of MPO overexpression.

Trisomy of chromosome 9q: specific chromosome change associated with tumorigenicity during the process of X-ray-induced neoplastic transformation in golden hamster embryo cells

We have reported that trisomy of chromosome 7 is commonly observed in anchorage-independent clones isolated from X-irradiated golden hamster embryo cells. All 10 clones derived from different irradiated populations showed tumorigenicity when 1 x 10(7) cells were injected s.c. into nude mice (BALB/c, nu/nu). From karyotypic analysis, we found that 8 of 10 cells showed trisomy of chromosome 9. One cell line had a translocation between chromosomes 9q and 19q and trisomy of chromosome 7. The other cell line contained trisomy of chromosome 9 and a translocation between chromosomes 7q and 8q. Using Southern blot analysis, we observed no amplification of v-myc, v-Ha-ras, v-Ki-ras or N-ras-related oncogenes. Furthermore, we could not detect either an increase in expression of v-myc- and v-Ha-ras-related genes or the activation of any oncogene, by the NIH 3T3 transfection assay. Our results suggest that trisomy of chromosome 7 is insufficient for the expression of tumorigenicity and that increased dosage of chromosome 9q may play an important role in the malignant progression of X-ray-induced neoplastic transformation.

Molecular cloning and chromosomal assignment of a human perforin (PFP) gene

Human perforin cDNA was isolated and the complete nucleotide sequence of the gene determined. The deduced amino acid sequence of human perforin showed 68.4% similarity to that of mouse perforin. RNA blot analysis of the human perforin gene revealed that the gene product is expressed preferentially in killer-type cells among cell lines tested, and in large granular lymphocytes among the peripheral blood mononuclear cells. In situ hybridization analysis with a human perforin cDNA probe revealed that the human perforin (PFP) gene is located on chromosome 17q11-21.

A new variant translocation 11;17 in a patient with acute promyelocytic leukemia together with t(7;12)

Bone marrow cells from the majority of patients with acute promyelocytic leukemia (APL) are characterized by t(15;17)(q22;q11-12). At least 12 variant translocations have both also reported, and in each case, either abnormal chromosome 15 or del(17q) or both were involved in complex rearrangements. We report a patient with APL showing two translocations without apparent involvement of chromosome 15 and without del(17q). The karyotype was 46,XY,t(7;12)(p15;p13),t(11;17)(q13;q12). Rearrangement involving t(11;17) is probably associated with APL, while t(7;12) appears to be therapy related.