Phase I trial of the mTOR inhibitor everolimus in combination with multi-agent chemotherapy in relapsed childhood acute lymphoblastic leukemia

Obesity and Leukemia: Biological Mechanisms, Perspectives, and Challenges

PURPOSE OF REVIEW

To examine the epidemiological data on obesity and leukemia; evaluate the effect of obesity on leukemia outcomes in childhood acute lymphoblastic leukemia (ALL) survivors; assess the potential mechanisms through which obesity may increase the risk of leukemia; and provide the effects of obesity management on leukemia. Preventive (diet, physical exercise, obesity pharmacotherapy, bariatric surgery) measures, repurposing drugs, candidate therapeutic agents targeting oncogenic pathways of obesity and insulin resistance in leukemia as well as challenges of the COVID-19 pandemic are also discussed.

RECENT FINDINGS

Obesity has been implicated in the development of 13 cancers, such as breast, endometrial, colon, renal, esophageal cancers, and multiple myeloma. Leukemia is estimated to account for approximately 2.5% and 3.1% of all new cancer incidence and mortality, respectively, while it represents the most frequent cancer in children younger than 5 years. Current evidence indicates that obesity may have an impact on the risk of leukemia. Increased birthweight may be associated with the development of childhood leukemia. Obesity is also associated with worse outcomes and increased mortality in leukemic patients. However, there are several limitations and challenges in meta-analyses and epidemiological studies. In addition, weight gain may occur in a substantial number of childhood ALL survivors while the majority of studies have documented an increased risk of relapse and mortality among patients with childhood ALL and obesity. The main pathophysiological pathways linking obesity to leukemia include bone marrow adipose tissue; hormones such as insulin and the insulin-like growth factor system as well as sex hormones; pro-inflammatory cytokines, such as IL-6 and TNF-α; adipocytokines, such as adiponectin, leptin, resistin, and visfatin; dyslipidemia and lipid signaling; chronic low-grade inflammation and oxidative stress; and other emerging mechanisms. Obesity represents a risk factor for leukemia, being among the only known risk factors that could be prevented or modified through weight loss, healthy diet, and physical exercise. Pharmacological interventions, repurposing drugs used for cardiometabolic comorbidities, and bariatric surgery may be recommended for leukemia and obesity-related cancer prevention.

Relapsed/Refractory T- Acute Lymphoblastic Leukemia - Current Options and Future Directions

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. The T-cell subtype (T-ALL) accounts for 10-15% of pediatric ALL cases and has been historically associated with outcomes inferior to those of B-cell ALL (B-ALL). The prognosis of T-ALL has significantly improved with contemporary intensive pediatric regimens. However, most children with relapsed T-ALL have dismal outcomes and fewer therapeutic salvage options than those available for B-ALL. After demonstrating efficacy in relapsed T-ALL, nelarabine is being increasingly incorporated into frontline T-ALL regimens. The development of genomic sequencing has led to the identification of new T-ALL subgroups and potential targeted therapeutic approaches which could improve patients' outcomes and reduce the toxicity associated with current therapy. Immunotherapy and cellular therapy regimens are also under early investigation in T-cell malignancies. This review outlines the clinical and biological characteristics of T-ALL and provides an overview of novel treatment options for refractory and relapsed T-ALL.

The Role of miRNAs in Childhood Acute Lymphoblastic Leukemia Relapse and the Associated Molecular Mechanisms

Acute lymphoblastic leukemia (ALL) is the most common cancer in children worldwide. Although ALL patients' overall survival rates in wealthy countries currently surpass 80%, 15-20% of patients still experience relapse. The underlying mechanisms of relapse are still not fully understood, and little progress has been made in treating refractory or relapsed disease. Disease relapse and treatment failure are common causes of leukemia-related death. In ALL relapse, several gene signatures have been identified, but it is also important to study miRNAs involved in ALL relapse in an effort to avoid relapse and to achieve better survival rates since miRNAs regulate target genes that participate in signaling pathways involved in relapse, such as those related to drug resistance, survival signals, and antiapoptotic mechanisms. Several miRNAs, such as miR-24, miR-27a, miR-99/100, miR-124, miR-1225b, miR-128b, miR-142-3p, miR-155 and miR-335-3p, are valuable biomarkers for prognosis and treatment response in ALL patients. Thus, this review aimed to analyze the primary miRNAs involved in pediatric ALL relapse and explore the underlying molecular mechanisms in an effort to identify miRNAs that may be potential candidates for anti-ALL therapy soon.

A phase 2 and pharmacological study of sapanisertib in patients with relapsed and/or refractory acute lymphoblastic leukemia

BACKGROUND

Despite recent approval of several new agents, relapsed acute lymphoblastic leukemia (ALL) remains challenging to treat. Sapanisertib (MLN0128/TAK-228) is an oral TORC1/2 inhibitor that exhibited preclinical activity against ALL.

METHODS

We conducted a single-arm multi-center Phase II study of sapanisertib monotherapy (3 mg orally daily of the milled formulation for 21 days every 28 days) in patients with ALL through the Experimental Therapeutics Clinical Trials Network (NCI-9775).

RESULTS

Sixteen patients, 15 of whom were previously treated (median 3 prior lines of therapy), were enrolled. Major grade 3-4 non-hematologic toxicities included mucositis (3 patients) and hyperglycemia (2 patients) as well as hepatic failure, seizures, confusion, pneumonitis, and anorexia (1 patient each). Grade >2 hematological toxicity included leukopenia (3), lymphopenia (2), thrombocytopenia, and neutropenia (1). The best response was stable disease in 2 patients (12.5%), while only 3 patients (19%) were able to proceed to Cycle 2. Pharmacokinetic analysis demonstrated drug exposures similar to those observed in solid tumor patients. Immunoblotting in serially collected samples indicated limited impact of treatment on phosphorylation of mTOR pathway substrates such as 4EBP1, S6, and AKT.

CONCLUSION

In summary, single-agent sapanisertib had a good safety profile but limited target inhibition or efficacy in ALL as a single agent. This trial was registered at ClinicalTrials.gov as NCT02484430.

PI3K/Akt/mTOR Signaling Pathway in Blood Malignancies-New Therapeutic Possibilities

Blood malignancies remain a therapeutic challenge despite the development of numerous treatment strategies. The phosphatidylinositol-3 kinase (PI3K)/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway plays a central role in regulating many cellular functions, including cell cycle, proliferation, quiescence, and longevity. Therefore, dysregulation of this pathway is a characteristic feature of carcinogenesis. Increased activation of PI3K/Akt/mTOR signaling enhances proliferation, growth, and resistance to chemo- and immunotherapy in cancer cells. Overactivation of the pathway has been found in various types of cancer, including acute and chronic leukemia. Inhibitors of the PI3K/Akt/mTOR pathway have been used in leukemia treatment since 2014, and some of them have improved treatment outcomes in clinical trials. Recently, new inhibitors of PI3K/Akt/mTOR signaling have been developed and tested both in preclinical and clinical models. In this review, we outline the role of the PI3K/Akt/mTOR signaling pathway in blood malignancies' cells and gather information on the inhibitors of this pathway that might provide a novel therapeutic opportunity against leukemia.

Biochemical and Hematologic Profiles in B-Cell Acute Lymphoblastic Leukemia Children

B-cell acute lymphoblastic leukemia is the most common type of leukemia found in children. Timely diagnosis, white blood cell count, age of onset, and sex are considered the most important prognostic factors in childhood leukemia. Hematological and biochemical profiles are crucially important to infer the health of leukemia patient pre-chemotherapy and post-chemotherapy treatment. In the current study 200 cases were taken and evaluated for hematological (complete blood count and white blood differential count) and biochemical parameters (renal function tests, liver function tests, serum electrolytes and serum proteins) by comparison with normal reference values. Most of the cases were male under 5 years of age. Hematology parameters including red blood cells, hemoglobin and platelet levels were relatively low whereas white blood cells level was high in cases as compared with normal reference value. Sex-wise and age-wise comparison of biochemical profile showed significant difference among B-cell acute lymphoblastic leukemia cases whereas hematological profile did not show any visible difference.

Children's Oncology Group blueprint for research: Acute lymphoblastic leukemia

Cure rates for acute lymphoblastic leukemia (ALL), the most common childhood cancer have steadily improved over the past five decades. This is due to intensifying systemic therapy, recognizing and treating the central nervous system as a sanctuary site, and implementing modern risk stratification to deliver varying intensities of therapy based on age, presenting white blood count, sentinel somatic genetics, and therapy response. Recently, numerous Children's Oncology Group trials have demonstrated the lack of benefit of intensifying traditional chemotherapy, providing evidence that new approaches are needed to cure the patients for whom cure has been elusive. Distinguishing those who require intensive or novel therapeutic approaches from others who will be cured with minimal therapy is key for future trials. Incorporating new genomic biomarkers and more sensitive measures of minimal/measurable residual disease provide opportunities to achieve these goals.

Proteomics in Childhood Acute Lymphoblastic Leukemia: Challenges and Opportunities

Acute lymphoblastic leukemia (ALL) is the most common cancer in children and one of the success stories in cancer therapeutics. Risk-directed therapy based on clinical, biologic and genetic features has played a significant role in this accomplishment. Despite the observed improvement in survival rates, leukemia remains one of the leading causes of cancer-related deaths. Implementation of next-generation genomic and transcriptomic sequencing tools has illustrated the genomic landscape of ALL. However, the underlying dynamic changes at protein level still remain a challenge. Proteomics is a cutting-edge technology aimed at deciphering the mechanisms, pathways, and the degree to which the proteome impacts leukemia subtypes. Advances in mass spectrometry enable high-throughput collection of global proteomic profiles, representing an opportunity to unveil new biological markers and druggable targets. The purpose of this narrative review article is to provide a comprehensive overview of studies that have utilized applications of proteomics in an attempt to gain insight into the pathogenesis and identification of biomarkers in childhood ALL.

Targeting N-cadherin (CDH2) and the malignant bone marrow microenvironment in acute leukaemia

This review discusses current research on acute paediatric leukaemia, the leukaemic bone marrow (BM) microenvironment and recently discovered therapeutic opportunities to target leukaemia-niche interactions. The tumour microenvironment plays an integral role in conferring treatment resistance to leukaemia cells, this poses as a key clinical challenge that hinders management of this disease. Here we focus on the role of the cell adhesion molecule N-cadherin (CDH2) within the malignant BM microenvironment and associated signalling pathways that may bear promise as therapeutic targets. Additionally, we discuss microenvironment-driven treatment resistance and relapse, and elaborate the role of CDH2-mediated cancer cell protection from chemotherapy. Finally, we review emerging therapeutic approaches that directly target CDH2-mediated adhesive interactions between the BM cells and leukaemia cells.

The pathogenesis and development of targeted drugs in acute T lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is mainly classified into acute T- and B-lymphoblastic leukaemia according to the source of its lymphocytes, thymus and bone. Among them, the incidence of adult T-cell accounts for about 25% of adult acute lymphoblastic leukaemia, but the degree of malignancy is high and the treatment rate and prognosis are poor. At this stage, there are few targeted drugs and the commonly used broad-spectrum chemotherapeutic drugs have poor efficacy and many adverse drug reactions. Understanding and investigating the pathogenesis of T-acute lymphoblastic leukaemia is very important for further developing new targeting drugs and improving existing drugs. Dysregulated signalling pathways are the main aetiological factors of T-acute lymphoblastic leukaemia. They play crucial roles in promoting tumour initiation, progression, drug design and therapy responses. This is primarily because signalling pathways are indispensable for many cellular biological processes, including tumour growth, migration, invasion, metastasis and others. As a result, small molecule inhibitors targeting the major kinase components of the signalling pathway have received a lot of attention and have been developed and evaluated in preclinical models and clinical trials. Already marketed drugs are also being repurposed in combination therapies to further improve efficacy and overcome tumour cell resistance. In this review, we have aimed to examine the latest and most classical signalling pathways in the aetiology of T-acute lymphoblastic leukaemia and shed light on potential targets for novel therapeutic agents to act on.

Targeted Treatment and Immunotherapy in High-risk and Relapsed/ Refractory Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia is the most frequent pediatric malignancy in children, comprising 30% of all pediatric malignancies; adult ALL comprises 5% of all ALL cases, which have a 186.6 per 1 million incidence. In pediatric ALL (pALL), on which this review focuses, approximately 1 in 285 children are diagnosed with cancer before the age of 20, and approximately 1 in 530 young adults between the ages of 20 and 39 years old is a childhood cancer survivor. The survival probability in pALL is now very high, approximately 80-90%. Thus, the most important is to improve supportive care and treatment based on relapse risk, optimally being based on the genetic feature of malignant cells. Improvements made by now are mainly the classifying of subgroups based on genetic characteristics such as aneuploidy or translocation and aligning them with treatment response. Relevant genetic changes in ALL pathogenesis are transcription regulators of lymphoid development (PAX5, IKZF1, EBF1, and LEF1) and/or coactivators (TBL1XR1 and ERG), lymphoid signaling (BTLA, and CD200 TOX), and tumor suppressor genes (CDKN2A, CDKN2B, RB1, and TP53). This review aims to summarize treatment strategies inhibiting tyrosine kinases, influencing different signaling pathways, BCL inhibitors, and anti-CD therapy (anti-cluster differentiation therapy) in pALL. CAR T-cell therapy (chimeric antigen receptors T-cell therapy) is under research and requires further development.

Novel pharmacological and dietary approaches to target mTOR in B-cell acute lymphoblastic leukemia

High-risk subtypes of B-cell acute lymphoblastic leukemia (B-ALL) are frequently associated with aberrant activation of tyrosine kinases (TKs). These include Ph+ B-ALL driven by BCR-ABL, and Ph-like B-ALL that carries other chromosomal rearrangements and/or gene mutations that activate TK signaling. Currently, the tyrosine kinase inhibitor (TKI) dasatinib is added to chemotherapy as standard of care in Ph+ B-ALL, and TKIs are being tested in clinical trials for Ph-like B-ALL. However, growth factors and nutrients in the leukemia microenvironment can support cell cycle and survival even in cells treated with TKIs targeting the driving oncogene. These stimuli converge on the kinase mTOR, whose elevated activity is associated with poor prognosis. In preclinical models of Ph+ and Ph-like B-ALL, mTOR inhibitors strongly enhance the anti-leukemic efficacy of TKIs. Despite this strong conceptual basis for targeting mTOR in B-ALL, the first two generations of mTOR inhibitors tested clinically (rapalogs and mTOR kinase inhibitors) have not demonstrated a clear therapeutic window. The aim of this review is to introduce new therapeutic strategies to the management of Ph-like B-ALL. We discuss novel approaches to targeting mTOR in B-ALL with potential to overcome the limitations of previous mTOR inhibitor classes. One approach is to apply third-generation bi-steric inhibitors that are selective for mTOR complex-1 (mTORC1) and show preclinical efficacy with intermittent dosing. A distinct, non-pharmacological approach is to use nutrient restriction to target signaling and metabolic dependencies in malignant B-ALL cells. These two new approaches could potentiate TKI efficacy in Ph-like leukemia and improve survival.

SOHO State of the Art Updates and Next Questions | Novel Approaches to Pediatric T-cell ALL and T-Lymphoblastic Lymphoma

While outcomes for children with T-cell acute lymphoblastic leukemia (T-ALL) and T-lymphoblastic lymphoma (T-LL) have improved significantly with contemporary therapy, outcomes for patients with relapsed or refractory (r/r) disease remain dismal. Improved risk stratification and the incorporation of novel therapeutics have the potential to improve outcomes further in T-ALL/T-LL by limiting relapse risk and improving salvage rates for those with r/r disease. In this review we will discuss the challenges and new opportunities for improved risk stratification in T-ALL and T-LL. We will further discuss the recent incorporation of the novel therapeutics nelarabine and bortezomib into front-line therapy for children with T-ALL and T-LL. Finally, we will address new classes of targeted small molecule inhibitors, immunotherapeutics, and chimeric antigen receptor T-cell therapies under investigation in r/r T-ALL and T-LL.

Temsirolimus combined with cyclophosphamide and etoposide for pediatric patients with relapsed/refractory acute lymphoblastic leukemia: a Therapeutic Advances in Childhood Leukemia Consortium trial (TACL 2014-001)

Phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling is commonly dysregulated in acute lymphoblastic leukemia (ALL). The TACL2014-001 phase I trial of the mTOR inhibitor temsirolimus in combination with cyclophosphamide and etoposide was performed in children and adolescents with relapsed/refractory ALL. Temsirolimus was administered intravenously (IV) on days 1 and 8 with cyclophosphamide 440 mg/m2 and etoposide 100 mg/m2 IV daily on days 1-5. The starting dose of temsirolimus was 7.5 mg/m2 (DL1) with escalation to 10 mg/m2 (DL2), 15 mg/m2 (DL3), and 25 mg/m2 (DL4). PI3K/mTOR pathway inhibition was measured by phosphoflow cytometry analysis of peripheral blood specimens from treated patients. Sixteen heavily-pretreated patients were enrolled with 15 evaluable for toxicity. One dose-limiting toxicity of grade 4 pleural and pericardial effusions occurred in a patient treated at DL3. Additional dose-limiting toxicities were not seen in the DL3 expansion or DL4 cohort. Grade 3/4 non-hematologic toxicities occurring in three or more patients included febrile neutropenia, elevated alanine aminotransferase, hypokalemia, mucositis, and tumor lysis syndrome and occurred across all doses. Response and complete were observed at all dose levels with a 47% overall response rate and 27% complete response rate. Pharmacodynamic correlative studies demonstrated dose-dependent inhibition of PI3K/mTOR pathway phosphoproteins in all studied patients. Temsirolimus at doses up to 25 mg/m2 with cyclophosphamide and etoposide had an acceptable safety profile in children with relapsed/refractory ALL. Pharmacodynamic mTOR target inhibition was achieved and appeared to correlate with temsirolimus dose. Future testing of next-generation PI3K/mTOR pathway inhibitors with chemotherapy may be warranted to increase response rates in children with relapsed/refractory ALL.

Genetic and Epigenetic Targeting Therapy for Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia is the most common malignancy in children and is characterized by numerous genetic and epigenetic abnormalities. Epigenetic mechanisms, including DNA methylations and histone modifications, result in the heritable silencing of genes without a change in their coding sequence. Emerging studies are increasing our understanding of the epigenetic role of leukemogenesis and have demonstrated the potential of DNA methylations and histone modifications as a biomarker for lineage and subtypes classification, predicting relapse, and disease progression in acute lymphoblastic leukemia. Epigenetic abnormalities are relatively reversible when treated with some small molecule-based agents compared to genetic alterations. In this review, we conclude the genetic and epigenetic characteristics in ALL and discuss the future role of DNA methylation and histone modifications in predicting relapse, finally focus on the individual and precision therapy targeting epigenetic alterations.

Telomerase (hTERT) Overexpression Reveals a Promising Prognostic Biomarker and Therapeutical Target in Different Clinical Subtypes of Pediatric Acute Lymphoblastic Leukaemia

Acute Lymphoblastic Leukemia (ALL) is a neoplasm of the hematopoietic system defined as a clonal expansion of an abnormal lymphoid precursor cell. It mostly affects children under five years of age and is the most common tumor to afflict pediatric patients. The expression of the human telomerase gene (hTERT) in patients with ALL has been studied as a biomarker and could become a new therapeutic target. We evaluate the role of hTERT gene expression in ALL pediatric patients, through quantitative real-time PCR technique, and the possible correlation between hTERT expression and clinical variables: gender, age, white blood cells (WBC), gene fusions, and immunophenotyping. The analysis between healthy controls and ALL patients (N = 244) was statistically significant (p < 0.001), demonstrating hTERT overexpression in these patients. In comparison with the usual set of clinical variables, the data were not statistically significant (p > 0.05), indicating that hTERT is equally overexpressed among patients regardless of gender, age, gene fusions, and immunophenotyping. Moreover, patients who presented a higher hTERT expression level had a significant (p < 0.0001) lower overall survival rate. In summary, hTERT expression emerges as an important molecular pathway in leukemogenesis regardless patient's clinical variables, thus, the data here presented pointed it as a valuable biomarker in pediatric acute lymphoblastic leukemia and a promising target for new therapeutic and prognostic measures.

Co-treatment With Everolimus, an mTOR-Specific Antagonist, or Downregulation of ELK1 Enhances the Sensitivity of Pancreatic Cancer Cells to Genistein

Genistein is a natural isoflavone with pharmacological or potentially anti-tumor properties. However, the resistance of cancer cells to genistein remains a major obstacle. This study focused on the mechanism implicated in the resistance of pancreatic cancer (PC) cells to genistein and the mechanism of action. First, key molecules and signaling pathways related to genistein resistance in PC cells were explored using bioinformatics tools. DEP domain containing MTOR interacting protein (DEPTOR), a typical inhibitor of the mammalian target of rapamycin (mTOR) signaling, was predicted to be poorly expressed in the genistein-resistant PC cells. Thereafter, genistein-resistant PC cells (Panc-1 and PaCa) were constructed. Altered expression of DEPTOR was introduced in cells, and everolimus (ELM), an mTOR-specific antagonist, was administrated in cells as well to examine their roles in genistein resistance. The cell apoptosis was examined in vitro and in vivo in mouse xenograft tumors. The upstream regulator of DEPTOR was predicted via bioinformatic tools. The bioinformatic analyses showed that the PI3K/AKT/mTOR signaling pathway was activated in the setting of DEPTOR downregulation in genistein-resistant PC cells. DEPTOR overexpression reduced the 50% inhibiting concentration (IC50) of genistein in PC cells and suppressed mTOR phosphorylation, and it increased caspase-3 activity, LDH release and apoptosis in PC cells. ELM treatment enhanced the sensitivity of PC cells to genistein in vitro and it strengthened the tumor-eliminating role of genistein in mice. ETS transcription factor ELK1 (ELK1), a transcription factor that negatively regulated DEPTOR transcription, was suppressed by genistein. Upregulation of ELK1 suppressed DEPTOR transcription and reduced the genistein sensitivity of cells, and it also blocked the genistein-sensitizing roles of ELM in PC cells. In conclusion, this study demonstrated that ELK1 reduces DEPTOR transcription, leading to mTOR phosphorylation and the drug resistance of PC cells.

Therapeutic Targeting of the Leukaemia Microenvironment

In recent decades, the conduct of uniform prospective clinical trials has led to improved remission rates and survival for patients with acute myeloid leukaemia and acute lymphoblastic leukaemia. However, high-risk patients continue to have inferior outcomes, where chemoresistance and relapse are common due to the survival mechanisms utilised by leukaemic cells. One such mechanism is through hijacking of the bone marrow microenvironment, where healthy haematopoietic machinery is transformed or remodelled into a hiding ground or "sanctuary" where leukaemic cells can escape chemotherapy-induced cytotoxicity. The bone marrow microenvironment, which consists of endosteal and vascular niches, can support leukaemogenesis through intercellular "crosstalk" with niche cells, including mesenchymal stem cells, endothelial cells, osteoblasts, and osteoclasts. Here, we summarise the regulatory mechanisms associated with leukaemia-bone marrow niche interaction and provide a comprehensive review of the key therapeutics that target CXCL12/CXCR4, Notch, Wnt/b-catenin, and hypoxia-related signalling pathways within the leukaemic niches and agents involved in remodelling of niche bone and vasculature. From a therapeutic perspective, targeting these cellular interactions is an exciting novel strategy for enhancing treatment efficacy, and further clinical application has significant potential to improve the outcome of patients with leukaemia.

Molecular-based and antibody-based targeted pharmacological approaches in childhood acute lymphoblastic leukemia

Introduction: Despite the significant survival improvement in childhood acutelymphoblastic leukemia (ALL), 15-20% of patients continue to relapse; outcomes following relapse remain suboptimal and have room for further improvement. Advances in genomics have shed new insights on the biology of ALL, led to the discovery of novel genomically defined ALL subtypes, refined prognostic significance and revealed new therapeutic vulnerabilities.Areas covered: In this review, the authors provide an overview of the genomic landscape of childhood ALL and highlight recent advances in molecular-based and antibody-based pharmacological approaches in the treatment of childhood ALL, from emerging preclinical evidence to published results of completed clinical trials.Expert opinion: Molecularly targeted therapies and immunotherapies have expanded the horizons of ALL therapy and represent promising therapeutic avenues for high-risk and relapsed/refractory ALL. These novel therapies are now moving into frontline ALL therapy and may define new treatment paradigms that aim to further improve survival and reduce chemotherapy-related toxicities in the management of pediatric ALL.

Advances in the Diagnosis and Treatment of Pediatric Acute Lymphoblastic Leukemia

The outcomes of pediatric acute lymphoblastic leukemia (ALL) have improved remarkably during the last five decades. Such improvements were made possible by the incorporation of new diagnostic technologies, the effective administration of conventional chemotherapeutic agents, and the provision of better supportive care. With the 5-year survival rates now exceeding 90% in high-income countries, the goal for the next decade is to improve survival further toward 100% and to minimize treatment-related adverse effects. Based on genome-wide analyses, especially RNA-sequencing analyses, ALL can be classified into more than 20 B-lineage subtypes and more than 10 T-lineage subtypes with prognostic and therapeutic implications. Response to treatment is another critical prognostic factor, and detailed analysis of minimal residual disease can detect levels as low as one ALL cell among 1 million total cells. Such detailed analysis can facilitate the rational use of molecular targeted therapy and immunotherapy, which have emerged as new treatment strategies that can replace or reduce the use of conventional chemotherapy.

The New Therapeutic Strategies in Pediatric T-Cell Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia is a genetically heterogeneous cancer that accounts for 10–15% of T-cell acute lymphoblastic leukemia (T-ALL) cases. The T-ALL event-free survival rate (EFS) is 85%. The evaluation of structural and numerical chromosomal changes is important for a comprehensive biological characterization of T-ALL, but there are currently no genetic prognostic markers. Despite chemotherapy regimens, steroids, and allogeneic transplantation, relapse is the main problem in children with T-ALL. Due to the development of high-throughput molecular methods, the ability to define subgroups of T-ALL has significantly improved in the last few years. The profiling of the gene expression of T-ALL has led to the identification of T-ALL subgroups, and it is important in determining prognostic factors and choosing an appropriate treatment. Novel therapies targeting molecular aberrations offer promise in achieving better first remission with the hope of preventing relapse. The employment of precisely targeted therapeutic approaches is expected to improve the cure of the disease and quality of life of patients. These include therapies that inhibit Notch1 activation (bortezomib), JAK inhibitors in ETP-ALL (ruxolitinib), BCL inhibitors (venetoclax), and anti-CD38 therapy (daratumumab). Chimeric antigen receptor T-cell therapy (CAR-T) is under investigation, but it requires further development and trials. Nelarabine-based regimens remain the standard for treating the relapse of T-ALL.

Imaging dynamic mTORC1 pathway activity in vivo reveals marked shifts that support time-specific inhibitor therapy in AML

Acute myeloid leukemia (AML) is a high remission, high relapse fatal blood cancer. Although mTORC1 is a master regulator of cell proliferation and survival, its inhibitors have not performed well as AML treatments. To uncover the dynamics of mTORC1 activity in vivo, fluorescent probes are developed to track single cell proliferation, apoptosis and mTORC1 activity of AML cells in the bone marrow of live animals and to quantify these activities in the context of microanatomical localization and intra-tumoral heterogeneity. When chemotherapy drugs commonly used clinically are given to mice with AML, apoptosis is rapid, diffuse and not preferentially restricted to anatomic sites. Dynamic measurement of mTORC1 activity indicated a decline in mTORC1 activity with AML progression. However, at the time of maximal chemotherapy response, mTORC1 signaling is high and positively correlated with a leukemia stemness transcriptional profile. Cell barcoding reveals the induction of mTORC1 activity rather than selection of mTORC1 high cells and timed inhibition of mTORC1 improved the killing of AML cells. These data define the real-time dynamics of AML and the mTORC1 pathway in association with AML growth, response to and relapse after chemotherapy. They provide guidance for timed intervention with pathway-specific inhibitors.

The role of mTORC1 in AML has not yet been proven due to the mixed results of its inhibitors in clinical trials. Here the authors show the real-time dynamics of the mTORC1 pathway in association with AML growth and response to chemotherapy with fluorescent markers, providing guidance for timed intervention with pathway-specific inhibitors.

B-ALL Complexity: Is Targeted Therapy Still A Valuable Approach for Pediatric Patients?

Simple Summary

B-ALL is the more frequent childhood malignancy. Even though significant improvements in patients’ survival, some pediatric B-ALL have still poor prognosis and novel strategies are needed. Recently, new genetic abnormalities and altered signaling pathways have been described, defining novel B-ALL subtypes.Innovative targeted therapeutic drugs may potentially show a great impact on the treatment of B-ALL subtypes, offering an important chance to block multiple signaling pathways and potentially improving the clinical management of B-ALL younger patients, especially for the new identified subtypes that lack efficient chemotherapeutic protocols. In this review, we shed light on the up-to-date knowledge of the novel childhood B-ALL subtypes and the altered signaling pathways that could become new druggable targets.

Abstract

B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic malignancy that arises from the clonal expansion of transformed B-cell precursors and predominately affects childhood. Even though significant progresses have been made in the treatment of B-ALL, pediatric patients’ outcome has to be furtherly increased and alternative targeted treatment strategies are required for younger patients. Over the last decade, novel approaches have been used to understand the genomic landscape and the complexity of the molecular biology of pediatric B-ALL, mainly next generation sequencing, offering important insights into new B-ALL subtypes, altered pathways, and therapeutic targets that may lead to improved risk stratification and treatments. Here, we will highlight the up-to-date knowledge of the novel B-ALL subtypes in childhood, with particular emphasis on altered signaling pathways. In addition, we will discuss the targeted therapies that showed promising results for the treatment of the different B-ALL subtypes.

The genomic landscape of pediatric acute lymphoblastic leukemia and precision medicine opportunities

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and constitutes approximately 25 % of cancer diagnoses among children under the age of 15 (Howlader et al., 2013) [1]. Overall, about half of ALL cases occur in children and adolescents and it is the most common acute leukemia until the early 20s, after which acute myeloid leukemia predominates. ALL is the most successful treatment paradigm in pediatric cancer medicine as illustrated by the significant survival rate improvement from ∼10 % in the 1960s to >90 % today (Hunger et al., 2015) [2]. This remarkable success stems from the progressive improvement in the efficacy of risk-adapted multiagent chemotherapy regimens with effective central nervous system (CNS) prophylaxis via well-designed randomized clinical trials conducted by international collaborative consortia, enhanced supportive care measures to decrease treatment-related mortality, in-depth understanding of the genetic basis of ALL, and refinement in treatment response assessment through serial minimal residual disease (MRD) monitoring (Pui et al., 2015) [3]. These advances collectively contribute to a decline in mortality rate of 23.5% for children diagnosed with ALL in the US from 2000 to 2010 (Smith et al., 2014) [4]. Nevertheless, outcomes of older adolescents and young adults with ALL still lag behind those of their younger counterparts despite pediatric-inspired chemotherapy regimens (Stock et al., 2019) [5], relapsed/refractory childhood ALL is associated with poor outcomes (Rheingold et al., 2019) [6], and ALL still represents the leading causes of cancer-related deaths (Smith et al., 2010) [7]. The last two decades have witnessed important genomic discoveries in ALL, enabled by advances in next-generation sequencing (NGS) technologies to characterize the landscape of germline and somatic alterations in ALL, some of which have important diagnostic, prognostic and therapeutic implications. Comprehensive genomic analysis of large cohorts of children and adults with ALL has revised the taxonomy of ALL in the molecular era by identifying novel clonal, subtype-defined chromosomal alterations associated with distinct gene expression signatures, thus reducing the proportion of patients previously labelled as "Others" from 25 % to approximately 5 % (Mullighan et al., 2019) [8]. Insights into the genomics of ALL further provide compelling biologic rationale to expand the scope of precision medicine therapies for childhood ALL. Herein, we summarize a decade of genomic discoveries to highlight three different facets of precision medicine in pediatric ALL: 1) inherited predispositions of ALL; 2) relevant molecularly targeted therapies in genomically-defined ALL subtypes; and 3) treatment response monitoring via pharmacogenomics and novel MRD biomarkers.

Pediatric acute lymphoblastic leukemia

The last decade has witnessed great advances in our understanding of the genetic and biological basis of childhood acute lymphoblastic leukemia (ALL), the development of experimental models to probe mechanisms and evaluate new therapies, and the development of more efficacious treatment stratification. Genomic analyses have revolutionized our understanding of the molecular taxonomy of ALL, and these advances have led the push to implement genome and transcriptome characterization in the clinical management of ALL to facilitate more accurate risk-stratification and, in some cases, targeted therapy. Although mutation- or pathway-directed targeted therapy (e.g., using tyrosine kinase inhibitors to treat Philadelphia chromosome [Ph]-positive and Phlike B-cell-ALL) is currently available for only a minority of children with ALL, many of the newly identified molecular alterations have led to the exploration of approaches targeting deregulated cell pathways. The efficacy of cellular or humoral immunotherapy has been demonstrated with the success of chimeric antigen receptor T-cell therapy and the bispecific engager blinatumomab in treating advanced disease. This review describes key advances in our understanding of the biology of ALL and optimal approaches to risk-stratification and therapy, and it suggests key areas for basic and clinical research.

How I treat relapsed acute lymphoblastic leukemia in the pediatric population

Relapsed acute lymphoblastic leukemia (ALL) has remained challenging to treat in children, with survival rates lagging well behind those observed at initial diagnosis. Although there have been some improvements in outcomes over the past few decades, only ∼50% of children with first relapse of ALL survive long term, and outcomes are much worse with second or later relapses. Recurrences that occur within 3 years of diagnosis and any T-ALL relapses are particularly difficult to salvage. Until recently, treatment options were limited to intensive cytotoxic chemotherapy with or without site-directed radiotherapy and allogeneic hematopoietic stem cell transplantation (HSCT). In the past decade, several promising immunotherapeutics have been developed, changing the treatment landscape for children with relapsed ALL. Current research in this field is focusing on how to best incorporate immunotherapeutics into salvage regimens and investigate long-term survival and side effects, and when these might replace HSCT. As more knowledge is gained about the biology of relapse through comprehensive genomic profiling, incorporation of molecularly targeted therapies is another area of active investigation. These advances in treatment offer real promise for less toxic and more effective therapy for children with relapsed ALL, and we present several cases highlighting contemporary treatment decision-making.

The rapamycin analog Everolimus reversibly impairs male germ cell differentiation and fertility in the mouse†

Sirolimus, also known as rapamycin, and its closely related rapamycin analog (rapalog) Everolimus inhibit "mammalian target of rapamycin complex 1" (mTORC1), whose activity is required for spermatogenesis. Everolimus is Food and Drug Administration approved for treating human patients to slow growth of aggressive cancers and preventing organ transplant rejection. Here, we test the hypothesis that rapalog inhibition of mTORC1 activity has a negative, but reversible, impact upon spermatogenesis. Juvenile (P20) or adult (P>60) mice received daily injections of sirolimus or Everolimus for 30 days, and tissues were examined at completion of treatment or following a recovery period. Rapalog treatments reduced body and testis weights, testis weight/body weight ratios, cauda epididymal sperm counts, and seminal vesicle weights in animals of both ages. Following rapalog treatment, numbers of differentiating spermatogonia were reduced, with concomitant increases in the ratio of undifferentiated spermatogonia to total number of remaining germ cells. To determine if even low doses of Everolimus can inhibit spermatogenesis, an additional group of adult mice received a dose of Everolimus ∼6-fold lower than a human clinical dose used to treat cancer. In these animals, only testis weights, testis weight/body weight ratios, and tubule diameters were reduced. Return to control values following a recovery period was variable for each of the measured parameters and was duration and dose dependent. Together, these data indicate rapalogs exerted a dose-dependent restriction on overall growth of juvenile and adult mice and negative impact upon spermatogenesis that were largely reversed; following treatment cessation, males from all treatment groups were able to sire offspring.

Increased mTOR activation in idiopathic multicentric Castleman disease

Idiopathic multicentric Castleman disease (iMCD) is a rare and poorly understood hematologic disorder characterized by lymphadenopathy, systemic inflammation, cytopenias, and life-threatening multiorgan dysfunction. Interleukin-6 (IL-6) inhibition effectively treats approximately one-third of patients. Limited options exist for nonresponders, because the etiology, dysregulated cell types, and signaling pathways are unknown. We previously reported 3 anti-IL-6 nonresponders with increased mTOR activation who responded to mTOR inhibition with sirolimus. We investigated mTOR signaling in tissue and serum proteomes from iMCD patients and controls. mTOR activation was increased in the interfollicular space of iMCD lymph nodes (N = 26) compared with control lymph nodes by immunohistochemistry (IHC) for pS6, p4EBP1, and p70S6K, known effectors and readouts of mTORC1 activation. IHC for pS6 also revealed increased mTOR activation in iMCD compared with Hodgkin lymphoma, systemic lupus erythematosus, and reactive lymph nodes, suggesting that the mTOR activation in iMCD is not just a product of lymphoproliferation/inflammatory lymphadenopathy. Further, the degree of mTOR activation in iMCD was comparable to autoimmune lymphoproliferative syndrome, a disease driven by mTOR hyperactivation that responds to sirolimus treatment. Gene set enrichment analysis of serum proteomic data from iMCD patients (n = 88) and controls (n = 42) showed significantly enriched mTORC1 signaling. Finally, functional studies revealed increased baseline mTOR pathway activation in peripheral monocytes and T cells from iMCD remission samples compared with healthy controls. IL-6 stimulation augmented mTOR activation in iMCD patients, which was abrogated with JAK1/2 inhibition. These findings support mTOR activation as a novel therapeutic target for iMCD, which is being investigated through a trial of sirolimus (NCT03933904).

Aurora B kinase as a therapeutic target in acute lymphoblastic leukemia

PURPOSE

Acute lymphoblastic leukemia (ALL) is curable with standardized chemotherapy. However, the development of novel therapies is still required, especially for patients with relapsed or refractory disease. By utilizing an in vitro drug screening system, active molecular targeting agents against ALL were explored in this study.

METHODS

By the in vitro drug sensitivity test, 81 agents with various actions were screened for their cytotoxicity in a panel of 22 ALL cell lines and ALL clinical samples. The drug effect score (DES) was calculated from the dose-response of each drug for comparison among drugs or samples. Normal peripheral blood mononuclear cells were also applied onto the drug screening to provide the reference control values. The drug combination effect was screened based on the Bliss independent model, and validated by the improved isobologram method.

RESULTS

On sensitivity screening in a cell line panel, barasertib-HQPA which is an active metabolite of barasertib, an aurora B kinase inhibitor, alisertib, an aurora A kinase inhibitor, and YM155, a survivin inhibitor, were effective against the broadest range of ALL cells. The DES of barasertib-HQPA was significantly higher in ALL clinical samples compared to the reference value. There were significant correlations in DES between barasertib-HQPA and vincristine or docetaxel. In the drug combination assay, barasertib-HQPA and eribulin showed additive to synergistic effects.

CONCLUSION

Aurora B kinase was identified to be an active therapeutic target in a broad range of ALL cells. Combination therapy of barasertib and a microtubule-targeting drug is of clinical interest.

The Physiopathology of T- Cell Acute Lymphoblastic Leukemia: Focus on Molecular Aspects

T-cell acute lymphoblastic leukemia/lymphoma is an aggressive hematological neoplasm whose classification is still based on immunophenotypic findings. Frontline treatment encompass high intensity combination chemotherapy with good overall survival; however, relapsing/refractory patients have very limited options. In the last years, the understanding of molecular physiopathology of this disease, lead to the identification of a subset of patients with peculiar genetic profile, namely “early T-cell precursors” lymphoblastic leukemia, characterized by dismal outcome and indication to frontline allogeneic bone marrow transplant. In general, the most common mutations occur in the NOTCH1/FBXW7 pathway (60% of adult patients), with a positive prognostic impact. Other pathogenic steps encompass transcriptional deregulation of oncogenes/oncosuppressors, cell cycle deregulation, kinase signaling (including IL7R-JAK-STAT pathway, PI3K/AKT/mTOR pathway, RAS/MAPK signaling pathway, ABL1 signaling pathway), epigenetic deregulation, ribosomal dysfunction, and altered expression of oncogenic miRNAs or long non-coding RNA. The insight in the genomic landscape of the disease paves the way to the use of novel targeted drugs that might improve the outcome, particularly in relapse/refractory patients. In this review, we analyse available literature on T-ALL pathogenesis, focusing on molecular aspects of clinical, prognostic, and therapeutic significance.

A phase 1 trial of everolimus and bevacizumab in children with recurrent solid tumors

BACKGROUND

The prognosis for children with recurrent solid tumors generally is poor. Targeting mammalian target of rapamycin (mTOR) and vascular endothelial growth factor A with everolimus and bevacizumab, respectively, synergistically improves progression-free survival and is well tolerated in adults with solid tumors.

METHODS

In the current phase 1 study, a total of 15 children with recurrent or refractory solid tumors were treated with bevacizumab and everolimus to establish the maximum tolerated dose, toxicity, and preliminary antitumor response (ClinicalTrials.gov identifier NCT00756340). The authors also evaluated everolimus-mediated inhibition of the mTOR pathway in the peripheral blood mononuclear cells of treated patients.

RESULTS

Tumors predominantly were soft tissue and/or bone sarcomas (8 cases) and brain tumors (5 cases). The first 2 patients enrolled at dose level 1 (10 mg/kg of bevacizumab and 4 mg/m² of everolimus) experienced dose-limiting toxicities (DLTs). The next 5 patients were enrolled at dose level 0 (8 mg/kg of bevacizumab and 4 mg/m² of everolimus), and DLTs occurred in 2 patients. The authors then modified the protocol to permit expansion of dose 0, and 8 additional patients were added, with no DLTs reported. Of all the patients, stable disease occurred in 4 patients (30.8%; median, 2 courses), and progressive disease occurred in 9 patients (69.2%). Overall survival was 0.59 years (95% CI, 0.24-1.05 years). The mTOR biomarker phospho-4EBP1 Thr/37/46 significantly decreased from baseline to day 27 in peripheral blood mononuclear cells (P = .045). Phospho-AKT levels also decreased from those at baseline.

CONCLUSIONS

The maximum tolerated dose of cotreatment with bevacizumab and everolimus was 8 mg/kg of bevacizumab and 4 mg/m² of everolimus in a 4-week cycle for children with recurrent solid tumors.

Targeting mTOR and Metabolism in Cancer: Lessons and Innovations

Cancer cells support their growth and proliferation by reprogramming their metabolism in order to gain access to nutrients. Despite the heterogeneity in genetic mutations that lead to tumorigenesis, a common alteration in tumors occurs in pathways that upregulate nutrient acquisition. A central signaling pathway that controls metabolic processes is the mTOR pathway. The elucidation of the regulation and functions of mTOR can be traced to the discovery of the natural compound, rapamycin. Studies using rapamycin have unraveled the role of mTOR in the control of cell growth and metabolism. By sensing the intracellular nutrient status, mTOR orchestrates metabolic reprogramming by controlling nutrient uptake and flux through various metabolic pathways. The central role of mTOR in metabolic rewiring makes it a promising target for cancer therapy. Numerous clinical trials are ongoing to evaluate the efficacy of mTOR inhibition for cancer treatment. Rapamycin analogs have been approved to treat specific types of cancer. Since rapamycin does not fully inhibit mTOR activity, new compounds have been engineered to inhibit the catalytic activity of mTOR to more potently block its functions. Despite highly promising pre-clinical studies, early clinical trial results of these second generation mTOR inhibitors revealed increased toxicity and modest antitumor activity. The plasticity of metabolic processes and seemingly enormous capacity of malignant cells to salvage nutrients through various mechanisms make cancer therapy extremely challenging. Therefore, identifying metabolic vulnerabilities in different types of tumors would present opportunities for rational therapeutic strategies. Understanding how the different sources of nutrients are metabolized not just by the growing tumor but also by other cells from the microenvironment, in particular, immune cells, will also facilitate the design of more sophisticated and effective therapeutic regimen. In this review, we discuss the functions of mTOR in cancer metabolism that have been illuminated from pre-clinical studies. We then review key findings from clinical trials that target mTOR and the lessons we have learned from both pre-clinical and clinical studies that could provide insights on innovative therapeutic strategies, including immunotherapy to target mTOR signaling and the metabolic network in cancer.

New biomarkers and therapeutic strategies in acute lymphoblastic leukemias: Recent advances

Acute lymphoblastic leukemia (ALL) represents a heterogeneous group of hematologic malignancies, and it is normally characterized by an aberrant proliferation of immature lymphoid cells. Moreover, dysregulation of multiple signaling pathways that normally regulate cellular transcription, growth, translation, and proliferation is frequently encountered in this malignancy. ALL is the most frequent tumor in childhood, and adult ALL patients still correlate with poor survival. This review focuses on modern therapies in ALL that move beyond standard chemotherapy, with a particular emphasis on immunotherapeutic approaches as new treatment strategies. Bi-specific T-cell Engagers (BiTE) antibodies, the chimeric antigen receptor (CAR)-T cells, or CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats [CRISPR]-associated nuclease 9) represent other new innovative approaches for this disease. Target and tailored therapy could make the difference in previously untreatable cases, i.e., precision and personalized medicine. Clinical trials will help to select the most efficient novel therapies in ALL management and to integrate them with existing treatments to achieve durable cures.

Therapeutic Targeting of Notch Signaling Pathway in Hematological Malignancies

The Notch pathway plays a key role in several processes, including stem-cell self-renewal, proliferation, and cell differentiation. Several studies identified recurrent mutations in hematological malignancies making Notch one of the most desirable targets in leukemia and lymphoma. The Notch signaling mediates resistance to therapy and controls cancer stem cells supporting the development of on-target therapeutic strategies to improve patients’ outcome. In this brief review, we outline the therapeutic potential of targeting Notch pathway in T-cell acute jlymphoblastic leukemia, chronic lymphocytic leukemia, and mantle cell lymphoma.

Integrating microRNA and mRNA expression in rapamycin-treated T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) has a relatively improved remission rate, but the poor outcomes are primarily due to resistance and relapse. Moreover, organs infiltration trends to occur during remission. Rapamycin was applied to treat malignancies for decades. In this investigation, we aimed to explore the molecular mechanisms and pathway changes during the T-ALL therapeutic process. T-ALL cell line Molt-4 cells were treated with rapamycin and performed microarray analysis to identify the deregulated miRNAs and mRNAs (log2 fold change>2 or <-2). To obtain regulatory miRNA/mRNA network, miRNA target prediction softwares and Cytoscape were used to plot and modularize the rapamycin treatment-related network. Surprisingly, the enriched pathways were not involved in mediating either cell death or apoptosis but were responsible for angiogenesis, cell survival, and anti-apoptosis, which is consistent with the Gene Ontology analysis and PPI network based on all deregulated mRNAs, indicating that these elements likely play a role in promoting Molt-4 cell survival or escaping from rapamycin. The expression of 3 miRNAs (miR-149-3p, miR-361-3p, and miR-944) and their putative targets, which play central roles in their module, were validated by qRT-PCR. These results provide novel insight into potentially relevant biological pathways for T-ALL cells escaping from chemotherapy or developing central nervous system infiltration.

Targeting mTOR in Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is an aggressive hematologic disorder and constitutes approximately 25% of cancer diagnoses among children and teenagers. Pediatric patients have a favourable prognosis, with 5-years overall survival rates near 90%, while adult ALL still correlates with poorer survival. However, during the past few decades, the therapeutic outcome of adult ALL was significantly ameliorated, mainly due to intensive pediatric-based protocols of chemotherapy. Mammalian (or mechanistic) target of rapamycin (mTOR) is a conserved serine/threonine kinase belonging to the phosphatidylinositol 3-kinase (PI3K)-related kinase family (PIKK) and resides in two distinct signalling complexes named mTORC1, involved in mRNA translation and protein synthesis and mTORC2 that controls cell survival and migration. Moreover, both complexes are remarkably involved in metabolism regulation. Growing evidence reports that mTOR dysregulation is related to metastatic potential, cell proliferation and angiogenesis and given that PI3K/Akt/mTOR network activation is often associated with poor prognosis and chemoresistance in ALL, there is a constant need to discover novel inhibitors for ALL treatment. Here, the current knowledge of mTOR signalling and the development of anti-mTOR compounds are documented, reporting the most relevant results from both preclinical and clinical studies in ALL that have contributed significantly into their efficacy or failure.

Dysregulation of miR-335-3p, targeted by NEAT1 and MALAT1 long non-coding RNAs, is associated with poor prognosis in childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most prevalent cancer among children, and multidrug efflux mediated by overexpression of ABC transporters is the major impediment to successful chemotherapy in this malignancy. The goal of this study is to identify the non-coding RNAs (ncRNAs) which may affect the expression levels of ABCA3; the previously identified prognostic biomarker for multidrug resistance (MDR) in childhood ALL (cALL). Bone marrow samples from 64 cALLs, including 46 de novo and 18 relapsed patients, in addition to 30 non-cancer controls were collected, and ncRNAs were nominated using in silico studies. Quantitative RT-PCR showed low expression profiles of miR-335-3p in cALLs compared with the control group (P = 0.018). Inverse correlation was determined between the miR-335-3p and ABCA3 mRNA expression profiles in cALL patients (r = 0.5019, P = 0.002). Moreover, it was shown that the expression levels of miR-335-3p was downregulated in the drug-resistant samples (MDR group) compared with the drug-sensitive patients (mrd- group), (P = 0.0005, AUC = 0.801). On the other hand, negative correlations were identified between the expression levels of miR-335-3p and the selected LncRNAs, NEAT1 and MALAT1, in the MDR group compared with the mrd- patients (P = 0.009), suggesting a sponge effect for these LncRNAs. The current study showed a potential regulatory role for miR-335-3p in ABCA3 expression targeted by NEAT1 and MALAT1 long non-coding RNAs. This negative impact may possibly contribute to the development of chemoresistance in childhood ALL, and provide an exceptional insight to new therapeutic approaches.

Molecular Approaches to Treating Pediatric Leukemias

Over the past decades, striking progress has been made in the treatment of pediatric leukemia, approaching 90% overall survival in children with acute lymphoblastic leukemia (ALL) and 75% in children with acute myeloid leukemia (AML). This has mainly been achieved through multiagent chemotherapy including CNS prophylaxis and risk-adapted therapy within collaborative clinical trials. However, prognosis in children with refractory or relapsed leukemia remains poor and has not significantly improved despite great efforts. Hence, more effective and less toxic therapies are urgently needed. Our understanding of disease biology, molecular drivers, drug resistance and, thus, the possibility to identify children at high-risk for treatment failure has significantly improved in recent years. Moreover, several new drugs targeting key molecular pathways involved in leukemia development, cell growth, and proliferation have been developed and approved. These striking achievements are linked to the great hope to further improve survival in children with refractory and relapsed leukemia. This review gives an overview on current molecularly targeted therapies in children with leukemia, including kinase, and proteasome inhibitors, epigenetic and enzyme targeting, as well as apoptosis regulators among others.

Therapeutic Targeting of mTOR in T-Cell Acute Lymphoblastic Leukemia: An Update

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive blood malignancy that arises from the clonal expansion of transformed T-cell precursors. Although T-ALL prognosis has significantly improved due to the development of intensive chemotherapeutic protocols, primary drug-resistant and relapsed patients still display a dismal outcome. In addition, lifelong irreversible late effects from conventional therapy are a growing problem for leukemia survivors. Therefore, novel targeted therapies are required to improve the prognosis of high-risk patients. The mechanistic target of rapamycin (mTOR) is the kinase subunit of two structurally and functionally distinct multiprotein complexes, which are referred to as mTOR complex 1 (mTORC1) and mTORC2. These two complexes regulate a variety of physiological cellular processes including protein, lipid, and nucleotide synthesis, as well as autophagy in response to external cues. However, mTOR activity is frequently deregulated in cancer, where it plays a key oncogenetic role driving tumor cell proliferation, survival, metabolic transformation, and metastatic potential. Promising preclinical studies using mTOR inhibitors have demonstrated efficacy in many human cancer types, including T-ALL. Here, we highlight our current knowledge of mTOR signaling and inhibitors in T-ALL, with an emphasis on emerging evidence of the superior efficacy of combinations consisting of mTOR inhibitors and either traditional or targeted therapeutics.

A phase 1 trial of temsirolimus and intensive re-induction chemotherapy for 2nd or greater relapse of acute lymphoblastic leukaemia: a Children's Oncology Group study (ADVL1114)

The phosphatidylinositol 3-kinase (PI3K)/mammalian (or mechanistic) target of rapamycin (mTOR) signalling pathway is commonly dysregulated in acute lymphoblastic leukaemia (ALL). A phase 1 trial of the mTOR inhibitor temsirolimus in combination with UKALL R3 re-induction chemotherapy was conducted in children and adolescents with second or greater relapse of ALL. The initial temsirolimus dose level (DL1) was 10 mg/m² weekly × 3 doses. Subsequent patient cohorts received temsirolimus 7·5 mg/m² weekly × 3 doses (DL0) or, secondary to toxicity, 7·5 mg/m² weekly × 2 doses (DL-1). Sixteen patients were enrolled, 15 were evaluable for toxicity. Dose-limiting toxicity (DLT) occurred at all three dose levels and included hypertriglyceridaemia, mucositis, ulceration, hypertension with reversible posterior leucoencephalopathy, elevated gamma-glutamyltransferase or alkaline phosphatase and sepsis. The addition of temsirolimus to UKALL R3 re-induction therapy resulted in excessive toxicity and was not tolerable in children with relapsed ALL. However, this regimen induced remission in seven of fifteen patients. Three patients had minimal residual disease levels <0·01%. Inhibition of PI3K signalling was detected in patients treated at all dose levels of temsirolimus, but inhibition at an early time point did not appear to correlate with clinical responses at the end of re-induction therapy.