The signal transducer and activator of transcription STAT5b gene is a new partner of retinoic acid receptor alpha in acute promyelocytic-like leukaemia

The oncogenic mechanisms of the Janus kinase-signal transducer and activator of transcription pathway in digestive tract tumors

Digestive tract tumors are heterogeneous and involve the dysregulation of multiple signaling pathways. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway plays a notable role in the oncogenesis of digestive tract tumors. Typically activated by pro-inflammatory cytokines, it regulates important biological processes, such as cell growth, differentiation, apoptosis, immune responses, and inflammation. The aberrant activation of this pathway manifests in different forms, including mutations in JAKs, overexpression of cytokine receptors, and sustained STAT activation, and contributes to promoting the malignant characteristics of cancer cells, including uncontrolled proliferation, resistance to apoptosis, enhanced invasion and metastasis, angiogenesis, acquisition of stem-like properties, and drug resistance. Numerous studies have shown that aberrant activation of the JAK-STAT pathway is closely related to the development and progression of digestive tract tumors, contributing to tumor survival, angiogenesis, changes in the tumor microenvironment, and even immune escape processes. In addition, this signaling pathway also affects the sensitivity of digestive tract tumors to chemotherapy and targeted therapy. Therefore, it is crucial to comprehensively understand the oncogenic mechanisms underlying the JAK-STAT pathway in order to develop effective therapeutic strategies against digestive tract tumors. Currently, several JAK-STAT inhibitors are undergoing clinical and preclinical trials as potential treatments for various human diseases. However, further investigation is required to determine the role of this pathway, as well as the effectiveness and safety of its inhibitors, especially in the context of digestive tract tumors. In this review, we provide an overview of the structure, classic activation, and negative regulation of the JAK-STAT pathway. Furthermore, we discuss the pathogenic mechanisms of JAK-STAT signaling in different digestive tract tumors, with the aim of identifying potential novel therapeutic targets. Video Abstract.

Hematopoietic Stem Cell Transplantation in Acute Promyelocytic Leukemia in the Era of All-Trans Retinoic Acid (ATRA) and Arsenic Trioxide (ATO)

Acute promyelocytic leukemia (APL) currently represents one of the malignant hemopathies with the best therapeutic responses, following the introduction of all-trans retinoic acid (ATRA) and subsequently of arsenic trioxide (ATO) treatment. As a result, a large proportion of patients with APL achieve long-term responses after first-line therapy, so performing a hematopoietic stem cell transplant as consolidation of first complete remission (CR) is no longer necessary. Even in the case of relapses, most patients obtain a new remission as a result of therapy with ATO and ATRA, but an effective consolidation treatment is necessary to maintain it. The experience accumulated from studies published in the last two decades shows the effectiveness of hematopoietic stem cell transplantation (HSCT) in improving the outcome of patients who achieve a new CR. Thus, the expert groups recommend transplantation as consolidation therapy in patients with a second CR, with the indication for autologous HSCT in cases with molecular CR and for allogeneic HSCT in patients with the persistence of minimal residual disease (MRD) or with early relapse. However, there is a variety of controversial aspects related to the role of HSCT in APL, ranging from the fact that outcome data are obtained almost exclusively from retrospective studies and historical analyses to questions related to the type of transplantation, the impact of minimal residual disease, conditioning regimens, or the role of other therapeutic options. All these questions justify the need for controlled prospective studies in the following years.

Therapy-Related Acute Promyelocytic Leukemia: A Case Report and a Review of Literature

Acute promyelocytic leukemia (APL) is a subgroup of acute myeloid leukemia (AML), and while not a common form of cancer, it does make up a modest portion of acute leukemia. The genetic hallmark of APL is the t(15;17)(q24.1;q21.2) promyelocytic leukemia/retinoic acid receptor alpha (PML/RARA) protein. We present the case of a patient who had undergone prior therapy for stage IIIC squamous cell carcinoma of the anorectal region with 5-fluorouracil, mitomycin C, and radiation and developed therapy-related acute promyelocytic leukemia about 18 months later. We also review the clinical features and management of APL while also highlighting that therapy-related APL, although uncommon, can develop from chemoradiation. The specific diagnosis of therapy-related APL is its own distinct diagnosis, but its treatment remains the same as primary APL.

Refractory acute promyelocytic leukemia with PLZF/RARa rearrangement: a case report and literature review

Acute promyelocytic leukemia patients with PLZF-RARa rearrangement have no obvious differentiation-inducing effect on retinoic acid, have a poor response to traditional chemotherapy, and have poor overall prognosis. A case of acute promyelocytic leukemia with PLZF / RARa rearrangement reported in this article was treated with induction chemotherapy with arsenic trioxide combined with a new anthracycline (idarubicin) cytotoxic chemotherapy. The patient achieved complete response in the bone marrow. After the first induction, and achieved molecular remission after the second consolidation chemotherapy. At present, the patient was followed up for 40 months after hematological and cytogenetic remission, and the PLZF / RARa real-time PCR test was continuously negative.

In-depth analysis of the expression and functions of signal transducers and activators of transcription in human ovarian cancer

Background

Signal transducers and activators of transcription (STAT) transcription factors, a family of genes encoding transcription factors, have been linked to the development of numerous types of tumors. However, there is a relative paucity of a comprehensive investigation of the expression and functional analysis of STATs in ovarian cancer (OV).

Method

Gene expression profile interaction analysis (GEPI2A), Metascape, The Cancer Genome Atlas (TCGA), Kaplan-Meier Plotter, Linkedomics, and CancerSEA databases were used for expression analysis and functional enrichment of STATs in ovarian cancer patients. We screened potential predictive genes and evaluated their prognostic value by constructing the minor absolute shrinkage and selection operator (LASSO) Cox proportional risk regression model. We explored STAT5A expression and its effects on cell invasion using ovarian cancer cells and a tissue microarray.

Results

The expression level of STAT1 was higher, but that of STAT2-6 was lower in cancerous ovarian tissues compared to normal tissues, which were closely associated with the clinicopathological features. Low STAT1, high STAT4, and 6 mRNA levels indicated high overall survival. STAT1, 3, 4, and 5A were collectively constructed as prognostic risk models. STAT3, and 5A, up-regulating in the high-risk group, were regarded as risk genes. In subsequent validation, OV patients with a low level of P-STAT5A but not low STAT5A had a longer survival time (P=0.0042). Besides, a negative correlation was found between the expression of STAT5A and invasion of ovarian cancer cells (R= -0.38, p < 0.01), as well as DNA repair function (R= -0.36, p < 0.01). Furthermore, transient overexpression of STAT5A inhibited wound healing (21.8%, P<0.0001) and cell migration to the lower chamber of the Transwell system (29.3%, P<0.0001), which may be achieved by regulating the expression of MMP2.

Conclusion

It is suggested that STAT1, STAT4, and STAT6 may be potential targets for the proper treatment of ovarian cancer. STAT5A and P-STAT5A, biomarkers identified in ovarian cancer, may offer new perspectives for predicting prognosis and assessing therapeutic effects.

Atypical Rearrangements in APL-Like Acute Myeloid Leukemias: Molecular Characterization and Prognosis

Acute promyelocytic leukemia (APL) accounts for 10–15% of newly diagnosed acute myeloid leukemias (AML) and is typically caused by the fusion of promyelocytic leukemia with retinoic acid receptor α (RARA) gene. The prognosis is excellent, thanks to the all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) combination therapy. A small percentage of APLs (around 2%) is caused by atypical transcripts, most of which involve RARA or other members of retinoic acid receptors (RARB or RARG). The diagnosis of these forms is difficult, and clinical management is still a challenge for the physician due to variable response rates to ATRA and ATO. Herein we review variant APL cases reported in literature, including genetic landscape, incidence of coagulopathy and differentiation syndrome, frequent causes of morbidity and mortality in these patients, sensitivity to ATRA, ATO, and chemotherapy, and outcome. We also focus on non-RAR rearrangements, complex rearrangements (involving more than two chromosomes), and NPM1-mutated AML, an entity that can, in some cases, morphologically mimic APL.

A novel fusion protein TBLR1-RARα acts as an oncogene to induce murine promyelocytic leukemia: identification and treatment strategies

Acute promyelocytic leukemia (APL) is characterized by a specific chromosome translocation involving RARα and its fusion partners. For decades, the advent of all-trans retinoic acid (ATRA) synergized with arsenic trioxide (As₂O₃) has turned most APL from highly fatal to highly curable. TBLR1-RARα (TR) is the tenth fusion gene of APL identified in our previous study, with its oncogenic role in the pathogenesis of APL not wholly unraveled. In this study, we found the expression of TR in mouse hematopoietic progenitors induces blockade of differentiation with enhanced proliferative capacity in vitro. A novel murine transplantable leukemia model was then established by expressing TR fusion gene in lineage-negative bone marrow mononuclear cells. Characteristics of primary TR mice revealed a rapid onset of aggressive leukemia with bleeding diathesis, which recapitulates human APL more accurately than other models. Despite the in vitro sensitivity to ATRA-induced cell differentiation, neither ATRA monotherapy nor combination with As₂O₃ confers survival benefit to TR mice, consistent with poor clinical outcome of APL patients with TR fusion gene. Based on histone deacetylation phenotypes implied by bioinformatic analysis, HDAC inhibitors demonstrated significant survival superiority in the survival of TR mice, yielding insights into clinical efficacy against rare types of APL.

Current views on the genetic landscape and management of variant acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by the accumulation of promyelocytes in bone marrow. More than 95% of patients with this disease belong to typical APL, which express PML-RARA and are sensitive to differentiation induction therapy containing all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), and they exhibit an excellent clinical outcome. Compared to typical APL, variant APL showed quite different aspects, and how to recognize, diagnose, and treat variant APL remained still challenged at present. Herein, we drew the genetic landscape of variant APL according to recent progresses, then discussed how they contributed to generate APL, and further shared our clinical experiences about variant APL treatment. In practice, when APL phenotype was exhibited but PML-RARA and t(15;17) were negative, variant APL needed to be considered, and fusion gene screen as well as RNA-sequencing should be displayed for making the diagnosis as soon as possible. Strikingly, we found that besides of RARA rearrangements, RARB or RARG rearrangements also generated the phenotype of APL. In addition, some MLL rearrangements, NPM1 rearrangements or others could also drove variant APL in absence of RARA/RARB/RARG rearrangements. These results indicated that one great heterogeneity existed in the genetics of variant APL. Among them, only NPM1-RARA, NUMA-RARA, FIP1L1-RARA, IRF2BP2-RARA, and TFG-RARA have been demonstrated to be sensitive to ATRA, so combined chemotherapy rather than differentiation induction therapy was the standard care for variant APL and these patients would benefit from the quick switch between them. If ATRA-sensitive RARA rearrangement was identified, ATRA could be added back for re-induction of differentiation. Through this review, we hoped to provide one integrated view on the genetic landscape of variant APL and helped to remove the barriers for managing this type of disease.

Does acute promyelocytic leukemia patient with the STAT5B/RARa fusion gene respond well to decitabine?: A case report and literature review

RATIONALE

Most acute promyelocytic leukemia (APL) patients respond to all-trans-retinoic acid (ATRA)and have a good prognosis. However, variants APL who carry PLZF/RARа, STAT5B/RARа, and STAT3/RARа are insensitive to ATRA and have poor prognoses. The standard treatment for variants APL is still unclear due to the small sample size.

PATIENT CONCERNS

Here we reported a Chinese male who was admitted to our hospital with the complaint of rib pain, dyspnea, and fever (37.5°C). Blood tests showed leukopenia (1.83 × 10/L), anemia (hemoglobin 73 g/L), and thrombocytopenia (54 × 10/L). Prothrombin time and activated partial thromboplastin time were normal.

DIAGNOSES

The patient was diagnosed as STAT5b-RARa-positive APL based on the clinical and laboratory findings.

INTERVENTIONS

ATRA was used immediately for induction treatment, then he was treated with ATRA + arsenic trioxide and got the severe cardiac insufficiency. Subsequently, consolidation chemotherapy was added with ATRA + Huangdai tablets + idarubicin and decitabine, cytarabine, aclamycin (DCAG).

OUTCOMES

The patient relapsed soon after his first molecular complete remission (CRm), fortunately, he got a second CRm with DCAG. He has survived for more than 9 months and remains CRm, now he is looking for a suitable donor to prepare for hematopoietic stem cell transplantation (HSCT).

LESSONS

APL patients with STAT5B-RARa is not only resistant to ATRA, but also to conventional combination chemotherapy such as daunorubicin and cytarabine/idarubicin and cytarabine or other regimens. Relapse and extramedullary infiltration is common, HSCT is a effective treatment, and the best time for HSCT is after the first CR. It should be noted that this patient got CRm with DCAG after relapse, so the role of decitabine in APL with STAT5B-RARa needs to be considered.

Emerging Cancer Epigenetic Mechanisms Regulated by All-Trans Retinoic Acid

All-trans retinoic acid (RA), which is the dietary bioactive derivative obtained from animal (retinol) and plant sources (beta-carotene), is a physiological lipid signal of both embryonic and postembryonic development. During pregnancy, either RA deficiency or an excessive RA intake is teratogenic. Too low or too high RA affects not only prenatal, but also postnatal, developmental processes such as myelopoiesis and mammary gland morphogenesis. In this review, we mostly focus on emerging RA-regulated epigenetic mechanisms involving RA receptor alpha (RARA) and Annexin A8 (ANXA8), which is a member of the Annexin family, as well as ANXA8 regulatory microRNAs (miRNAs). The first cancer showing ANXA8 upregulation was reported in acute promyelocytic leukemia (APL), which induces the differentiation arrest of promyelocytes due to defective RA signaling caused by RARA fusion genes as the PML-RARA gene. Over the years, ANXA8 has also been found to be upregulated in other cancers, even in the absence of RARA fusion genes. Mechanistic studies on human mammary cells and mammary glands of mice showed that ANXA8 upregulation is caused by genetic mutations affecting RARA functions. Although not all of the underlying mechanisms of ANXA8 upregulation have been elucidated, the interdependence of RA-RARA and ANXA8 seems to play a relevant role in some normal and tumorigenic settings.

PLZF-RARα, NPM1-RARα, and Other Acute Promyelocytic Leukemia Variants: The PETHEMA Registry Experience and Systematic Literature Review

It has been suggested that 1–2% of acute promyelocytic leukemia (APL) patients present variant rearrangements of retinoic acid receptor alpha (RARα) fusion gene, with the promyelocytic leukaemia zinc finger (PLZF)/RAR_α being the most frequent. Resistance to all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) has been suggested in PLZF/RAR_α and other variant APLs. Herein, we analyze the incidence, characteristics, and outcomes of variant APLs reported to the multinational PETHEMA (Programa para el Tratamiento de Hemopatias Malignas) registry, and we perform a systematic review in order to shed light on strategies to improve management of these extremely rare diseases. Of 2895 patients with genetically confirmed APL in the PETHEMA registry, 11 had variant APL (0.4%) (9 PLZF-RAR_α and 2 NPM1-RAR_α), 9 were men, with median age of 44.6 years (3 months to 76 years), median leucocytes (WBC) 16.8 × 10⁹/L, and frequent coagulopathy. Eight patients were treated with ATRA plus chemotherapy-based regimens, and 3 with chemotherapy-based. As compared to previous reports, complete remission and survival was slightly better in our cohort, with 73% complete remission (CR) and 73% survival despite a high relapse rate (43%). After analyzing our series and performing a comprehensive and critical review of the literature, strong recommendations on appropriate management of variant APL are not possible due to the low number and heterogeneity of patients reported so far.

Classic and Variants APLs, as Viewed from a Therapy Response

Most acute promyelocytic leukemia (APL) are caused by PML-RARA, a translocation-driven fusion oncoprotein discovered three decades ago. Over the years, several other types of rare X-RARA fusions have been described, while recently, oncogenic fusion proteins involving other retinoic acid receptors (RARB or RARG) have been associated to very rare cases of acute promyelocytic leukemia. PML-RARA driven pathogenesis and the molecular basis for therapy response have been the focus of many studies, which have now converged into an integrated physio-pathological model. The latter is well supported by clinical and molecular studies on patients, making APL one of the rare hematological disorder cured by targeted therapies. Here we review recent data on APL-like diseases not driven by the PML-RARA fusion and discuss these in view of current understanding of "classic" APL pathogenesis and therapy response.

Acute Promyelocytic Leukemia: A Constellation of Molecular Events around a Single PML-RARA Fusion Gene

Although acute promyelocytic leukemia (APL) is one of the most characterized forms of acute myeloid leukemia (AML), the molecular mechanisms involved in the development and progression of this disease are still a matter of study. APL is defined by the PML-RARA rearrangement as a consequence of the translocation t(15;17)(q24;q21). However, this abnormality alone is not able to trigger the whole leukemic phenotype and secondary cooperating events might contribute to APL pathogenesis. Additional somatic mutations are known to occur recurrently in several genes, such as FLT3, WT1, NRAS and KRAS, whereas mutations in other common AML genes are rarely detected, resulting in a different molecular profile compared to other AML subtypes. How this mutational spectrum, including point mutations in the PML-RARA fusion gene, could contribute to the 10%–15% of relapsed or resistant APL patients is still unknown. Moreover, due to the uncertain impact of additional mutations on prognosis, the identification of the APL-specific genetic lesion is still the only method recommended in the routine evaluation/screening at diagnosis and for minimal residual disease (MRD) assessment. However, the gene expression profile of genes, such as ID1, BAALC, ERG, and KMT2E, once combined with the molecular events, might improve future prognostic models, allowing us to predict clinical outcomes and to categorize APL patients in different risk subsets, as recently reported. In this review, we will focus on the molecular characterization of APL patients at diagnosis, relapse and resistance, in both children and adults. We will also describe different standardized molecular approaches to study MRD, including those recently developed. Finally, we will discuss how novel molecular findings can improve the management of this disease.

Pharmacological Inhibition of Oncogenic STAT3 and STAT5 Signaling in Hematopoietic Cancers

Signal Transducer and Activator of Transcription (STAT) 3 and 5 are important effectors of cellular transformation, and aberrant STAT3 and STAT5 signaling have been demonstrated in hematopoietic cancers. STAT3 and STAT5 are common targets for different tyrosine kinase oncogenes (TKOs). In addition, STAT3 and STAT5 proteins were shown to contain activating mutations in some rare but aggressive leukemias/lymphomas. Both proteins also contribute to drug resistance in hematopoietic malignancies and are now well recognized as major targets in cancer treatment. The development of inhibitors targeting STAT3 and STAT5 has been the subject of intense investigations during the last decade. This review summarizes the current knowledge of oncogenic STAT3 and STAT5 functions in hematopoietic cancers as well as advances in preclinical and clinical development of pharmacological inhibitors.

Acute Promyelocytic Leukemia: Update on the Mechanisms of Leukemogenesis, Resistance and on Innovative Treatment Strategies

This review highlights new findings that have deepened our understanding of the mechanisms of leukemogenesis, therapy and resistance in acute promyelocytic leukemia (APL). Promyelocytic leukemia-retinoic acid receptor α (PML-RARa) sets the cellular landscape of acute promyelocytic leukemia (APL) by repressing the transcription of RARa target genes and disrupting PML-NBs. The RAR receptors control the homeostasis of tissue growth, modeling and regeneration, and PML-NBs are involved in self-renewal of normal and cancer stem cells, DNA damage response, senescence and stress response. The additional somatic mutations in APL mainly involve FLT3, WT1, NRAS, KRAS, ARID1B and ARID1A genes. The treatment outcomes in patients with newly diagnosed APL improved dramatically since the advent of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). ATRA activates the transcription of blocked genes and degrades PML-RARα, while ATO degrades PML-RARa by promoting apoptosis and has a pro-oxidant effect. The resistance to ATRA and ATO may derive from the mutations in the RARa ligand binding domain (LBD) and in the PML-B2 domain of PML-RARa, but such mutations cannot explain the majority of resistances experienced in the clinic, globally accounting for 5-10% of cases. Several studies are ongoing to unravel clonal evolution and resistance, suggesting the therapeutic potential of new retinoid molecules and combinatorial treatments of ATRA or ATO with different drugs acting through alternative mechanisms of action, which may lead to synergistic effects on growth control or the induction of apoptosis in APL cells.

Acute Promyelocytic Leukemia: A History over 60 Years-From the Most Malignant to the most Curable Form of Acute Leukemia

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML) that is cytogenetically characterized by a balanced reciprocal translocation between chromosomes 15 and 17, which results in the fusion of the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARα) genes. Because patients with APL present a tendency for severe bleeding, often resulting in an early fatal course, APL was historically considered to be one of the most fatal forms of acute leukemia. However, therapeutic advances, including anthracycline- and cytarabine-based chemotherapy, have significantly improved the outcomes of APL patients. Due to the further introduction of all-trans retinoic acid (ATRA) and-more recently-the development of arsenic trioxide (ATO)-containing regimens, APL is currently the most curable form of AML in adults. Treatment with these new agents has introduced the concept of cure through targeted therapy. With the advent of revolutionary ATRA-ATO combination therapies, chemotherapy can now be safely omitted from the treatment of low-risk APL patients. In this article, we review the six-decade history of APL, from its initial characterization to the era of chemotherapy-free ATRA-ATO, a model of cancer-targeted therapy.

Characterization of atypical acute promyelocytic leukaemia: Three cases report and literature review

RATIONALE

The vast majority of acute promyelocytic leukemia (APL) is characterized with a specific chromosomal translocation t (15, 17) (q22, q21), which fuses PML-RARα leading to a good response to all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). However, there are few cases of atypical APL, including PLZF-RARα, F1P1L1-RARα, STAT5b-RARα, et al. Neither PLZF-RARα nor STAT5b-RARα are sensitive to ATRA and ATO, and the prognosis is poor.

PATIENT CONCERNS

Here we have 3 cases (PLZF-RARα, n = 2; STAT5b-RARα, n = 1). Case A, A 53-year-old Chinese female had suffered ecchymosis in both legs for 3 days. Case B, A 44 years old male suffered pain from lower limbs and hip. Case C, 52-year-old male patient presented with fever for 3 weeks invalid to antibiotics and gingival bleeding for 1 week.

DIAGNOSES

With RT-PCR and karyotype, Case A is diagnosed with STAT5b-RARα-positive APL.Case B, C are diagnosed with PLZF-RARα-positive APL.

INTERVENTIONS

In case A, ATO, and ATRA were used for induction treatment. In Case B, ATO, and chemotherapy with DA were given in the first induction treatment. In Case C, ATRA, and ATO were used immediately, subsequently, chemotherapy was added with DA, ATRA, and CAG combination treatment, and medium-dose cytarabine with daunorubicin were given regularly.

OUTCOMES

In Case A, the patient refused the following treatment and discharged on day 25. In Case B, the patient got the disseminated intravascular coagulation (DIC).In Case C, the patient has survived for 7 months and remains CR.

LESSONS

Both STAT5b-RARα-positive APL and PLZF-RARα-positive APL appear to be resistant to both ATRA and ATO, so combined chemotherapy and allo-HSCT should be considered. Since the prognosis and long-term outcome are poor, more clinical trials, and researches should be taken.

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

Since the comprehensive recommendations for the management of acute promyelocytic leukemia (APL) reported in 2009, several studies have provided important insights, particularly regarding the role of arsenic trioxide (ATO) in frontline therapy. Ten years later, a European LeukemiaNet expert panel has reviewed the recent advances in the management of APL in both frontline and relapse settings in order to develop updated evidence- and expert opinion-based recommendations on the management of this disease. Together with providing current indications on genetic diagnosis, modern risk-adapted frontline therapy, and salvage treatment, the review contains specific recommendations for the identification and management of the most important complications such as the bleeding disorder APL differentiation syndrome, QT prolongation, and other all-trans retinoic acid- and ATO-related toxicities, as well as recommendations for molecular assessment of the response to treatment. Finally, the approach to special situations is also discussed, including management of APL in children, elderly patients, and pregnant women. The most important challenges remaining in APL include early death, which still occurs before and during induction therapy, and optimizing treatment in patients with high-risk disease.

Traffic lights for retinoids in oncology: molecular markers of retinoid resistance and sensitivity and their use in the management of cancer differentiation therapy

For decades, retinoids and their synthetic derivatives have been well established anticancer treatments due to their ability to regulate cell growth and induce cell differentiation and apoptosis. Many studies have reported the promising role of retinoids in attaining better outcomes for adult or pediatric patients suffering from several types of cancer, especially acute myeloid leukemia and neuroblastoma. However, even this promising differentiation therapy has some limitations: retinoid toxicity and intrinsic or acquired resistance have been observed in many patients. Therefore, the identification of molecular markers that predict the therapeutic response to retinoid treatment is undoubtedly important for retinoid use in clinical practice. The purpose of this review is to summarize the current knowledge on candidate markers, including both genetic alterations and protein markers, for retinoid resistance and sensitivity in human malignancies.

Recurrent RARB Translocations in Acute Promyelocytic Leukemia Lacking RARA Translocation

Translocations of retinoic acid receptor-α (RARA), typically PML-RARA, are a genetic hallmark of acute promyelocytic leukemia (APL). However, because a small fraction of APL lack translocations of RARA, we focused here on APL cases without RARA translocation to elucidate the molecular etiology of RARA-negative APL. We performed whole-genome sequencing, PCR, and FISH for five APL cases without RARA translocations. Four of five RARA-negative APL cases had translocations involving retinoic acid receptor-β (RARB) translocations, and TBL1XR1-RARB was identified as an in-frame fusion in three cases; one case had an RARB rearrangement detected by FISH, although the partner gene could not be identified. When transduced in cell lines, TBL1XR1-RARB homodimerized and diminished transcriptional activity for the retinoic acid receptor pathway in a dominant-negative manner. TBL1XR1-RARB enhanced the replating capacity of mouse bone marrow cells and inhibited myeloid maturation of human cord blood cells as PML-RARA did. However, the response of APL with RARB translocation to retinoids was attenuated compared with that of PML-RARA, an observation in line with the clinical resistance of RARB-positive APL to ATRA. Our results demonstrate that the majority of RARA-negative APL have RARB translocations, thereby forming a novel, distinct subgroup of APL. TBL1XR1-RARB as an oncogenic protein exerts effects similar to those of PML-RARA, underpinning the importance of retinoic acid pathway alterations in the pathogenesis of APL.Significance: These findings report a novel and distinct genetic subtype of acute promyelocytic leukemia (APL) by illustrating that the majority of APL without RARA translocations harbor RARB translocations. Cancer Res; 78(16); 4452-8. ©2018 AACR.

Expression of the JAK/STAT Signaling Pathway in Bullous Pemphigoid and Dermatitis Herpetiformis

A family of eleven proteins comprises the Janus kinases (JAK) and signal transducers and activators of transcription (STAT) signaling pathway, which enables transduction of signal from cytokine receptor to the nucleus and activation of transcription of target genes. Irregular functioning of the cascade may contribute to pathogenesis of autoimmune diseases; however, there are no reports concerning autoimmune bullous diseases yet to be published. The aim of this study was to evaluate the expression of proteins constituting the JAK/STAT signaling pathway in skin lesions and perilesional area in dermatitis herpetiformis (DH) and bullous pemphigoid (BP), as well as in the control group. Skin biopsies were collected from 21 DH patients, from 20 BP patients, and from 10 healthy volunteers. The localization and expression of selected STAT and JAK proteins were examined by immunohistochemistry and immunoblotting. We found significantly higher expression of JAK/STAT proteins in skin lesions in patients with BP and DH, in comparison to perilesional skin and the control group, which may be related to proinflammatory cytokine network and induction of inflammatory infiltrate in tissues. Our findings suggest that differences in the JAK and STAT expression may be related to distinct cytokines activating them and mediating neutrophilic and/or eosinophilic infiltrate.

Recent advances in acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APML) is a subtype of leukaemia arising from a distinct reciprocal translocation involving chromosomes 15 and 17, which results in the PML-RARA fusion gene. Over the past three decades, APML has been transformed from a highly fatal disease to a highly curable one. This drastic improvement is because of the introduction of a new treatment strategy with all-trans retinoic acid and, more recently, arsenic trioxide. The revolutionary treatment of APML has also paved the way for a new cancer treatment, which is genetically targeted therapy. In this review, we look into this amazing journey of transformation and provide recent advances in the management of APML.

New variant of acute promyelocytic leukemia with IRF2BP2-RARA fusion

We present an acute promyelocytic leukemia (APL) patient with two subtypes of IRF2BP2–RARA, in which the IRF2BP2 gene showed completely new breakpoints. Bone marrow examination revealed morphologic features indicative of APL. However, promyelocytic leukemia–RARA fusion was not detected. A paired‐end mRNA sequencing followed by RT‐PCR and direct sequencing revealed two types of fusion transcripts between exon 1B of IRF2BP2 and exon 3 of RARA. The patient received all‐trans retinoic acid and conventional chemotherapy, but showed resistance. This is the second report of IRF2BP2 involvement in APL, and we describe various breakpoints for the IRF2BP2–RARA fusion gene.

Current first- and second-line treatment options in acute promyelocytic leukemia

Outcome of acute promyelocytic leukemia (APL) has remarkably improved during the last 30 years, especially after the identification of PML-RARA oncogene as a key in the pathogenesis of APL and all-trans retinoic acid as therapeutic agent. Arsenic trioxide has been recently demonstrated to be the most effective single antileukemic agent and it has also showed synergistic action when combined with all-trans retinoic acid, decreasing relapse rate especially in low/intermediate-risk settings. Therapeutic advances led to complete remission rates of more than 90%, modifying disease history. In relapse setting, arsenic trioxide-based regimens showed efficacy for the achievement of second molecular complete remission. The most challenging issue in APL management remains the significant early deaths rate, nowadays the principal reason for treatment failure.

PHA-Induced Peripheral Blood Cytogenetics and Molecular Analysis: a Valid Diagnostic and Follow-up Modality for Acute Promyelocytic Leukemia Patients Treated with ATRA and/or Arsenic Tri-oxide

BACKGROUND

Acute promyelocytic leukemia (APML) is characterized by the reciprocal translocation t(15;17) (q22;q12) resulting in the PML-RARα fusion gene. A dual diagnostic and follow up approach was applied including cytogenetic demonstration of the t(15;17) translocation and detection of PML-RARα chimeric transcripts by molecular means.

PURPOSE

Conventional cytogenetics involving bone marrow is beset with high probability of poor metaphase index and was substituted with phytohemagglutinin (PHA)-induced peripheral blood culture based cytogenetic analysis as a diagnostic and follow up modality in APML patients of Kashmir (North India). Both qualitative (RT-PCR) and quantitative (Q-PCR) tests were simultaneously carried out to authenticate the modified cytogenetics.

MATERIALS AND METHODS

Patient samples were subjected to the said techniques to establish their baseline as well as follow-up status.

RESULTS

Initial cytogenetics revealed 30 patients (81%) positive for t(15;17) whereas 7 (19%) had either cryptic translocation or were negative for t(15;17). Two cases had chromosome 16q deletion and no hallmark translocation t(15;17). Q-PCR status for PML-RARα was found to be positive for all patients. All the APML patients were reassessed at the end of consolidation phase and during maintenance phase of chemotherapy where 6 patients had molecular relapse, wherein 4 also demonstrated cytogenetic relapse.

CONCLUSIONS

It was found that PHA-induced peripheral blood cytogenetics along with molecular analysis could prove a reliable modality in the diagnosis and assessment of follow up response of APML patients.

Myeloid neoplasm demonstrating a STAT5B-RARA rearrangement and genetic alterations associated with all-trans retinoic acid resistance identified by a custom next-generation sequencing assay

We describe the case of a patient presenting with several weeks of symptoms related to pancytopenia associated with a maturation arrest at the late promyelocyte/early myelocyte stage of granulocyte differentiation. A diagnosis of acute promyelocytic leukemia was considered, but the morphologic features were atypical for this entity and conventional tests for the presence of a PML-RARA fusion gene were negative. Additional analysis using a custom next-generation sequencing assay revealed a rearrangement producing a STAT5B-RARA fusion gene, which was confirmed by reverse transcription polymerase chain reaction (RT-PCR) and supplementary cytogenetic studies, allowing the diagnosis of a morphologically atypical form of acute promyelocytic leukemia to be made. Analysis of the sequencing data permitted characterization of both chromosomal breakpoints and revealed two additional alterations, a small deletion in RARA exon 9 and a RARA R276W substitution, that have been linked to resistance to all-trans retinoic acid. This case highlights how next-generation sequencing can augment currently standard testing to establish diagnoses in difficult cases, and in doing so help guide selection of therapy.

Molecular Characteristics and Clinical Significance of 12 Fusion Genes in Acute Promyelocytic Leukemia: A Systematic Review

Acute promyelocytic leukemia (APL) is characterized by the generation of the promyelocytic leukemia-retinoic acid (RA) receptor α (PML-RARα) fusion gene. PML-RARα is the central leukemia-initiating event in APL and is directly targeted by all-trans-RA (ATRA) as well as arsenic. In classic APL harboring PML-RARα transcripts, more than 90% of patients can achieve complete remission when treated with ATRA combined with arsenic trioxide chemotherapy. In the last 20 years, more than 10 variant fusion genes have been found and identified in APL patients. These variant APL cases present different clinical phenotypes and treatment outcomes. All variant APL cases show a similar breakpoint within the RARα gene, whereas its partner genes are variable. These fusion proteins have the ability to repress rather than activate retinoic targets. These chimeric proteins also possess different molecular characteristics, thereby resulting in variable sensitivities to ATRA and clinical outcomes. In this review, we comprehensively analyze various rearrangements in variant APL cases that have been reported in the literature as well as the molecular characteristics and functions of the fusion proteins derived from different RARα partner genes and their clinical implications.

Acute Promyelocytic Leukemia: A Review and Discussion of Variant Translocations

The majority of patients with acute promyelocytic leukemia (APL) manifest the t(15;17)(q24.1;q21.2) translocation; however, a minor but significant proportion of patients with APL harbor complex, cryptic, or variant translocations, which typically involve RARA. With the exception of ZBTB16/RARA, these variants have similar morphologic and immunophenotypic features as classic APL. Study of the variant forms of APL not only gives insight into the pathogenesis of APL but also allows us to understand the mechanism of retinoid therapy. It is important to identify these cryptic and variant translocations because certain variants, including ZBTB16/RARA and STAT5B/RARA, are resistant to treatment with all-trans retinoic acid, arsenic trioxide, and anthracyclines.

The leukemic oncoprotein NPM1-RARA inhibits TP53 activity

The variant acute promyelocytic leukemia (APL) translocation t(5;17)(q35;q21) fuses the N-terminus of nucleophosmin (NPM1) to the retinoic acid receptor alpha (RARA). We found that ectopic NPM1-RARA expression decreased TP53 protein levels in target cells. NPM1-RARA impaired TP53-dependent transcription. Cells expressing NPM1-RARA were more resistant to apoptotic stimuli. This work identifies the TP53 tumor suppressor as a novel target through which NPM1-RARA impacts leukemogenesis, and confirms the importance of impairment of TP53 in establishment of the APL phenotype.

Synergistic targeted therapy for acute promyelocytic leukaemia: a model of translational research in human cancer

Acute promyelocytic leukaemia (APL), the M3 subtype of acute myeloid leukaemia, was once a lethal disease, yet nowadays the majority of patients with APL can be successfully cured by molecularly targeted therapy. This dramatic improvement in the survival rate is an example of the advantage of modern medicine. APL is characterized by a balanced reciprocal chromosomal translocation fusing the promyelocytic leukaemia (PML) gene on chromosome 15 with the retinoic acid receptor α (RARα) gene on chromosome 17. It has been found that all-trans-retinoic acid (ATRA) or arsenic trioxide (ATO) alone exerts therapeutic effect on APL patients with the PML-RARα fusion gene, and the combination of both drugs can act synergistically to further enhance the cure rate of the patients. Here, we provide an insight into the pathogenesis of APL and the mechanisms underlying the respective roles of ATRA and ATO. In addition, treatments that lead to more effective differentiation and apoptosis of APL cells, including leukaemia-initiating cells, and more thorough eradication of the disease will be discussed. Moreover, as a model of translational research, the development of a cure for APL has followed a bidirectional approach of 'bench to bedside' and 'bedside to bench', which can serve as a valuable example for the diagnosis and treatment of other malignancies.

Molecular Monitoring as a Path to Cure Acute Promyelocytic Leukemia

Acute promyelocytic leukemia (APL) is a molecularly well-defined disease, characterized by a specific chromosomal translocation; the improvement in biologic and clinical knowledge and subsequent introduction of molecularly targeted therapies have transformed the management of APL, with survival rates now exceeding 80%. Minimal residual disease (MRD) assessment in APL is the most important tool for its treatment; the prognostic role of the molecular detection of promyelocytic leukemia retinoic acid receptor α (PML-RARα) transcript after consolidation therapy in the early identification of the following hematologic relapse is now well established and guides preemptive therapy. First experiences performed with a qualitative polymerase chain reaction (PCR) approach were replaced with more accurate real-time quantitative PCR (RQ-PCR), which guarantees a numeric quantification of MRD. The identification of arsenic trioxide (ATO) as a valid therapy not only in relapsed patients but also as an alternative to standard therapy alone or in association with all-trans-retinoic acid enlarges the setting of validation of MRD evaluation in APL patients, considering a possible different clearance of PML-RARα with innovative therapy different from the standard ones. MRD monitoring demonstrated its validity also in the setting of relapsed patients with interesting results in the autologous and allogeneic stem cell transplantation setting or with the use of other biological agents. The aim of this review is to report and discuss the actual state of the art of MRD in APL.

NPM-RAR binding to TRADD selectively inhibits caspase activation, while allowing activation of NFκB and JNK

The t(5;17) variant of acute promeylocytic leukemia (APL) expresses a fusion of nucleophosmin (NPM) with the retinoic acid receptor alpha (RARA). We have previously shown that NPM-RAR is a binding partner of the tumor necrosis factor (TNF) receptor type-I-associated DEATH domain protein, TRADD. Binding of TNF to its receptor, TNF-R, induces recruitment of TRADD, and subsequent recruitment of a cascade of proteins that ultimate activate caspase 3, nuclear factor κB (NFκB) and c-Jun N-terminal kinase (JNK). We have previously shown that NPM-RAR interaction with TRADD blocks TNF activation of caspase 3, caspase 8, poly(ADP-ribose) polymerase (PARP) cleavage and, ultimately, apoptosis. We now report that NPM-RAR expression is permissive for TNF activation of NFκB and JNK. We propose that inhibition of TNF activation of apoptosis, while preserving TNF activation of NFκB and JNK pathways that stimulate cell growth and survival, represents a novel mechanism through which NPM-RAR contributes to development of the leukemic phenotype.

Restoration of CCAAT enhancer binding protein α P42 induces myeloid differentiation and overcomes all-trans retinoic acid resistance in human acute promyelocytic leukemia NB4-R1 cells

All-trans retinoic acid (ATRA) is one of the first line agents in differentiation therapy for acute promyelocytic leukemia (APL). However, drug resistance is a major problem influencing the efficacy of ATRA. Identification of mechanisms of ATRA resistance are urgenly needed. In the present study, we found that expression of C/EBPα, an important transcription factor for myeloid differentiation, was significantly suppressed in ATRA resistant APL cell line NB4-R1 compared with ATRA sensitive NB4 cells. Moreover, two forms of C/EBPα were unequally suppressed in NB4-R1 cells. Suppression of the full-length form P42 was more pronounced than the truncated form P30. Inhibition of PI3K/Akt/mTOR pathway was also observed in NB4-R1 cells. Moreover, C/EBPα expression was reduced by PI3K inhibitor LY294002 and mTOR inhibitor RAD001 in NB4 cells, suggesting that inactivation of the PI3K/Akt/mTOR pathway was responsible for C/EBPα suppression in APL cells. We restored C/EBPα P42 and P30 by lentivirus vectors in NB4-R1 cells, respectively, and found C/EBPα P42, but not P30, could increase CD11b, CD14, G-CSFR and GM-CSFR expression, which indicated the occurrence of myeloid differentiation. Further upregulating of CD11b expression and differential morphological changes were found in NB4-R1 cells with restored C/EBPα P42 after ATRA treatment. However, CD11b expression and differential morphological changes could not be induced by ATRA in NB4-R1 cells infected with P30 expressing or control vector. Thus, we inferred that ATRA sensitivity of NB4-R1 cells was enhanced by restoration of C/EBPα P42. In addition, we used histone deacetylase inhibitor trichostatin (TSA) to restore C/EBPα expression in NB4-R1 cells. Similar enhancement of myeloid differentiation and cell growth arrest were detected. Together, the present study demonstrated that suppression of C/EBPα P42 induced by PI3K/Akt/mTOR inhibition impaired the differentiation and ATRA sensitivity of APL cells. Restoring C/EBPα P42 is an attractive approach for differentiation therapy in ATRA resistant APL.

Identification of a novel fusion gene, IRF2BP2-RARA, in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by the fusion of retinoic acid receptor alpha (RARA) with promyelocytic leukemia (PML) or, rarely, other gene partners. This report presents a patient with APL with a novel fusion between RARA and the interferon regulatory factor 2 binding protein 2 (IRF2BP2) genes. A bone marrow examination in a 19-year-old woman who presented with ecchymoses and epistaxis showed morphologic and immunophenotypic features consistent with APL. PML oncogenic domain antibody was positive. Results of fluorescence in situ hybridization, conventional cytogenetics, reverse transcription-polymerase chain reaction (RT-PCR), and oligonucleotide microarray for PML-RARA and common APL variant translocations were negative. Next-generation RNA-sequencing analysis followed by RT-PCR and direct sequencing revealed distinct breakpoints within IRF2BP2 exon 2 and RARA intron 2. The patient received all-trans retinoic acid, arsenic, and gemtuzumab ozogamicin, and achieved complete remission. However, the disease relapsed 10 months later, 2 months after consolidation therapy. This is the first report showing involvement of IRF2BP2 in APL, and it expands the list of novel RARA partners identified in APL.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

[Acute promyelocytic leukaemia with translocations of t(15;17)(q22;q21) and rob(13;21): a case report and literatures review]

OBJECTIVE

To report an acute promyelocytic leukaemia (APL) case with translocation of rob (13;21) t(15;17) (q22;q21) and review its clinical and laboratory characteristics.

METHODS

Based on routine karyotype analysis and bone marrow morphology, we further used double color double fluorescent in situ hybridization (DCDF-FISH) and reverse transcriptase PCR (RT-PCR) to examine the patient's abnormities on cytogenetic and molecular biology, and reveal the clinical characteristics of this rare translocation also from the related literatures.

RESULTS

The clinical manifestation and bone marrow morphology examination of this patient were in accordance with pathologic feature of APL. On first visit, immunophenotyping analysis showed positive myeloid markers. Through R-banding, the patient's karyotype was confirmed as 45, XX, rob(13;21) t(15;17) (q22;q21) [6]/45, XX, rob(13;21) [14]. FISH results showed that 68.9% cells were typical t(15;17) pattern. The positive rates of fusion gene of PML-RARα detected by RT-PCR was 25.8%. Patient was treated by induction and consolidation therapy, the karyotype was 45, XX, rob(13;21 )[20] after complete remission. The positive rate of fusion gene of PML-RARα by FISH and its level were 2.5% and 0.003% respectively.

CONCLUSION

APL with rob (13;21) t(15;17) (q22;q21) was very rare, which was accorded with clinical and laboratory characteristics of APL. The value of chromosome abnormality as a prognostic marker in APL needs to be further observed..

Extrinsic apoptosis is impeded by direct binding of the APL fusion protein NPM-RAR to TRADD

A subset of acute promyelocytic leukemia (APL) cases has been characterized by the t(5;17)(q35;q21) translocation variant, which fuses nucleophosmin (NPM) to retinoic acid receptor α (RARA). The resultant NPM-RAR fusion protein blocks myeloid differentiation and leads to a leukemic phenotype similar to that caused by the t(15;17)(q22;q21) PML-RAR fusion. The contribution of the N-terminal 117 amino acids of NPM contained within NPM-RAR has not been well studied. As a molecular chaperone, NPM interacts with a variety of proteins implicated in leukemogenesis. Therefore, a proteomic analysis was conducted to identify novel NPM-RAR-associated proteins. TNF receptor type I-associated DEATH domain protein (TRADD) was identified as a relevant binding partner for NPM-RAR. This interaction was validated by coprecipitation and colocalization analysis. Biologic assessment found that NPM-RAR expression impaired TNF-induced signaling through TRADD, blunting TNF-mediated activation of caspase-3 (CASP3) and caspase-8 (CASP8), to ultimately block apoptosis.

IMPLICATIONS

This study identifies a novel mechanism through which NPM-RAR affects leukemogenesis.

The acute promyelocytic leukaemia success story: curing leukaemia through targeted therapies

The recent finding that almost all patients with acute promyelocytic leukaemia (APL) may be cured using a combination of retinoic acid (RA) and arsenic trioxide (As(2)O(3)) (N Engl J Med, 369, 2013 and 111) highlights the progress made in our understanding of APL pathogenesis and therapeutic approaches over the past 25 years. The study of APL has revealed many important lessons related to transcriptional control, nuclear organization, epigenetics and the role of proteolysis in biological control. Even more important has been the clinical demonstration that molecularly targeted therapy can eradicate disease.

STAT5-mediated self-renewal of normal hematopoietic and leukemic stem cells

The level of transcription factor activity critically regulates cell fate decisions such as hematopoietic stem cell self-renewal and differentiation. The balance between hematopoietic stem cell self-renewal and differentiation needs to be tightly controlled, as a shift toward differentiation might exhaust the stem cell pool, while a shift toward self-renewal might mark the onset of leukemic transformation. A number of transcription factors have been proposed to be critically involved in governing stem cell fate and lineage commitment, such as Hox transcription factors, c-Myc, Notch1, β-catenin, C/ebpα, Pu.1 and STAT5. It is therefore no surprise that dysregulation of these transcription factors can also contribute to the development of leukemias. This review will discuss the role of STAT5 in both normal and leukemic hematopoietic stem cells as well as mechanisms by which STAT5 might contribute to the development of human leukemias.