Impact of mutations in FLT3, PTPN11 and RAS genes on the overall survival of pediatric B cell precursor acute lymphoblastic leukemia in Brazil

The RAS-signaling-pathway-mutation-related prognosis in B-cell acute lymphoblastic leukemia: A report from South China children's leukemia group

The next-generation sequencing technologies application discovers novel genetic alterations frequently in pediatric acute lymphoblastic leukemia (ALL). RAS signaling pathway mutations at the time of relapse ALL frequently appear as small subclones at the time of onset, which are considered as the drivers in ALL relapse. Whether subclones alterations in the RAS signaling pathway should be considered for risk group stratification of ALL treatment is not decided yet. In this work, we investigate the RAS signaling pathway mutation spectrum and the related prognosis in pediatric ALL. We employed an NGS panel comprising 220 genes. NGS results were collected from 202 pediatric ALL patients. 155 patients (76.7%) harbored at least one mutation. The incidences of RAS signaling pathway mutations are different significantly between T-ALL and B-ALL. In B-ALL, the RAS pathway is mostly involved, and NRAS (17.6%), KRAS (22.7%), and PTPN11 (7.7%) were the three most frequently mutated genes. Co-occurring mutations of CREBBP and NRAS, FLT3, or PTPN11 (p = 0.002, p = 0.009, and p = 0.003, respectively) were found in this cohort. The 3-year RFS rates for the RAS signaling pathway mutation-positive and negative cases was 76.5 % versus 89.7 % (p = 0.012). Four cases relapsed in the lately 3 years were RAS signaling pathway mutation-positive. RAS signaling pathway mutation is an important biomarker for poorer relapse-free survival in pediatric B-ALL patients despite good early MRD levels.

Characterisation of FLT3 alterations in childhood acute lymphoblastic leukaemia

BACKGROUND

Alterations of FLT3 are among the most common driver events in acute leukaemia with important clinical implications, since it allows patient classification into prognostic groups and the possibility of personalising therapy thanks to the availability of FLT3 inhibitors. Most of the knowledge on FLT3 implications comes from the study of acute myeloid leukaemia and so far, few studies have been performed in other leukaemias.

METHODS

A comprehensive genomic (DNA-seq in 267 patients) and transcriptomic (RNA-seq in 160 patients) analysis of FLT3 in 342 childhood acute lymphoblastic leukaemia (ALL) patients was performed. Mutations were functionally characterised by in vitro experiments.

RESULTS

Point mutations (PM) and internal tandem duplications (ITD) were detected in 4.3% and 2.7% of the patients, respectively. A new activating mutation of the TKD, G846D, conferred oncogenic properties and sorafenib resistance. Moreover, a novel alteration involving the circularisation of read-through transcripts (rt-circRNAs) was observed in 10% of the cases. Patients presenting FLT3 alterations exhibited higher levels of the receptor. In addition, patients with ZNF384- and MLL/KMT2A-rearranged ALL, as well as hyperdiploid subtype, overexpressed FLT3.

DISCUSSION

Our results suggest that specific ALL subgroups may also benefit from a deeper understanding of the biology of FLT3 alterations and their clinical implications.

Association Between MIR3117 and MIR612 Genes Polymorphisms with Childhood Acute Lymphoblastic Leukemia in the Mexican Population

INTRODUCTION

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer in the world, which is associated with a wide spectrum of factors that play an important role in epidemiology, risk stratification, and therapeutic intervention. Several studies have shown the role of microRNAs (miRNAs) in the development of the disease. Genetic variations such as single-nucleotide polymorphisms (SNPs) in miRNAs can alter their function and lead to alter the expression of their target genes.

OBJECTIVE

The aim of this study was to evaluate the association of rs12402181 in MIR3117 and rs12803915 in MIR612 with the risk of childhood preB-ALL in Mexican population.

MATERIAL AND METHODS

DNA from 148 children (<18 years old) diagnosed with preB-ALL and 172 samples from participants in control group were included in the present study. Genotyping of the rs12402181 and rs12803915 polymorphisms was carried out by Real-Time PCR. To estimate the risk factor, the multiple genetic models co-dominant, dominant, and recessive were determined in both polymorphisms.

RESULTS

In dominant genetic model from rs12402181, a high risk of susceptibility to ALL was observed (OR = 2.03, 95% CI = 1.27-3.22, p = 0.003). In the analysis adjusted for gender, a significant increase in the risk of ALL was maintained (OR = 2.03, 95% CI = 1.28-3.24, p = 0.003). The rs12803915 polymorphism was no associated with the risk of susceptibility to preB-ALL in any of the genetic models using in this study.

CONCLUSIONS

Our data indicated that the A allele of the rs12402181 polymorphism may be considered as a genetic biomarker of preB-ALL susceptibility. Likewise, it was identified that the A allele of the rs12402181 polymorphism is an independent risk factor for ALL.

Adult Acute Myeloid Leukemia with the KMT2A-Mixed Lineage Leukemia T10 Fusion: An Analysis of 10 Cases Showed Common Features and Frequent Mutations in the RAS Signaling Pathway

Mixed lineage leukemia (MLL) T10 is a relatively rare partner for the KMT2A lysine (K)-specific methyltransferase 2A gene. The common features and coexisting mutations of acute myeloid leukemia (AML) patients with KMT2A-MLLT10 remain unknown. In this study, 10 adult AML patients with KMT2A-MLLT10 fusions were picked up from 496 AML patients by using RT-polymerase chain reaction (PCR) and/or fluorescence in situ hybridization, and then screened for mutations in the 49 genes panel with next-generation sequencing and PCR, followed by direct Sanger sequencing. Of the 10 unique individuals identified, 6 were male and 4 were female (M:F ratio, 1.5:1) with ages ranging from 19 to 52 years (median 39.5 years). Most (90%, 9/10) patients with KMT2A-MLLT10 were accompanied by additional mutations. Twelve mutated genes were detected, averaging 2.1 mutations per patient (range, 0-4). The most frequently mutated gene was NRAS (n = 5). Clinical and laboratory data pointed to common features: French American British-M5 subtype (n = 7), a high rate of relapse, and biomarkers CD33 (n = 10), CD117 (n = 9), CD13 (n = 8), and CD64 (n = 8). Overall, most patients harbored at least one mutation. A high incidence of mutations affecting the RAS signaling pathway or RAS regulating components was found in 50% (5/10) patients. The overall survival is about 12.0 months. Allogeneic-hematopoietic stem cell transplantation trends to improve survival in selected patients.

HOXA11 plays critical roles in disease progression and response to cytarabine in AML

Lysine methyltransferase 2A (KMT2A, also known as MLL) translocations (MLL-t) are frequently associated with mutations in RAS pathway genes in acute myeloid leukemia (AML). Previous findings with a mouse model showed that cooperation of MLL/AF10 with tyrosine-protein phosphatase non-receptor type 11 (PTPN11)^G503A accelerated leukemia development, but increased cytarabine (Ara-C) sensitivity of leukemia cells. To identify the genes responsible for reduced survival and Ara-C resistance, transcriptomic profiling between six pairs of mouse MLL/AF10(OM-LZ) leukemia cells harboring activating and wild-type KRAS or PTPN11 was compared. A total of 23 differentially expressed genes (DEGs) with >1.5-fold-change between the paired cell lines were identified. The Gene Ontology (GO) terms overrepresented in these 23 DEGs included ‘immune system process’, ‘actin filament binding’, ‘cellular response to interferon-alpha’ and ‘sequence-specific DNA’. Among the four genes (Hoxa11, PR domain zinc finger protein 5, Iroquois-class homeodomain protein IRX-5 and homeobox protein PKNOX2) mapped to the GO term ‘sequence-specific DNA’, HOXA11 upregulation was associated with AML harboring MLL-t and RAS signaling mutations based on a meta-analysis using data deposited in Oncomine™ and analysis of the clinical samples in the present study. Microarray data revealed that only Hoxa11 was upregulated in those cells harboring activating PTPN11. Functional studies of Hoxa11 knockdown or overexpression in MLL/AF10(OM-LZ) cells revealed that Hoxa11 expression levels were associated with survival in vivo and Ara-C sensitivity/apoptosis in vitro. In addition, Hoxa11 regulated the expression of the apoptosis-related genes, NF-κB inhibitor α, transcription factor p65 and transformation-related protein p53. Furthermore, the results of a meta-analysis using Heuser's AML dataset supported the finding that chemotherapy responders have higher expression levels of HOXA11. These results indicated that the expression of HOXA11 increased cell apoptosis and predicted an improved response to Ara-C in AML.

A unique mutator phenotype reveals complementary oncogenic lesions leading to acute leukemia

Mice homozygous for a hypomorphic allele of DNA replication factor minichromosome maintenance protein 2 (designated Mcm2cre/cre) develop precursor T cell lymphoblastic leukemia/lymphoma (pre-T LBL) with 4-32 small interstitial deletions per tumor. Mice that express a NUP98-HOXD13 (NHD13) transgene develop multiple types of leukemia, including myeloid and T and B lymphocyte. All Mcm2cre/cre NHD13+ mice develop pre-T LBL, and 26% develop an unrelated, concurrent B cell precursor acute lymphoblastic leukemia (BCP-ALL). Copy number alteration (CNA) analysis demonstrated that pre-T LBLs were characterized by homozygous deletions of Pten and Tcf3 and partial deletions of Notch1 leading to Notch1 activation. In contrast, BCP-ALLs were characterized by recurrent deletions involving Pax5 and Ptpn1 and copy number gain of Abl1 and Nup214 resulting in a Nup214-Abl1 fusion. We present a model in which Mcm2 deficiency leads to replicative stress, DNA double strand breaks (DSBs), and resultant CNAs due to errors in DNA DSB repair. CNAs that involve critical oncogenic pathways are then selected in vivo as malignant lymphoblasts because of a fitness advantage. Some CNAs, such as those involving Abl1 and Notch1, represent attractive targets for therapy.

Involvement of SNPs in miR-3117 and miR-3689d2 in childhood acute lymphoblastic leukemia risk

Acute lymphoblastic leukemia (ALL) is the most common cancer in children. Numerous studies have shown that microRNAs (miRNAs) could play a role in this disease. Nowadays, more than 2500 miRNAs have been described, that regulate more than 50% of genes, including those involved in B-cell maturation, differentiation and proliferation. Genetic variants in miRNAs can alter their own levels or function, affecting their target gene expression, and then, may affect ALL risk. Therefore, the aim of this study was to determine the role of miRNA genetic variants in B-ALL susceptibility. We analyzed all variants in pre-miRNAs (MAF > 1%) in two independent cohorts from Spain and Slovenia and inferred their functional effect by in silico analysis. SNPs rs12402181 in miR-3117 and rs62571442 in miR-3689d2 were associated with ALL risk in both cohorts, possibly through their effect on MAPK signalling pathway. These SNPs could be novel markers for ALL susceptibility.

[Spectrum of somatic mutations and their prognostic significance in adult patients with B cell acute lymphoblastic leukemia]

Objective: To investigate the spectrum of gene mutations in adult patients with B-acute lymphoblastic leukemia (B-ALL), and to analyze the influences of different gene mutations on prognosis. Methods: DNA samples from 113 adult B-ALL patients who administered from June 2009 to September 2015 were collected. Target-specific next generation sequencing (NGS) approach was used to analyze the mutations of 112 genes (focused on the specific mutational hotspots) and all putative mutations were compared against multiple databases to calculate the frequency spectrum. The impact of gene mutation on the patients' overall survival (OS) and recurrence free survival (RFS) was analyzed by the putative mutations through Kaplan-Meier, and Cox regression methods. Results: Of the 113 patients, 103 (92.0%) harbored at least one mutation and 29 (25.6%) harbored more than 3 genes mutation. The five most frequently mutated genes in B-ALL are SF1, FAT1, MPL, PTPN11 and NRAS. Gene mutations are different between Ph+ B-ALL and Ph- B-ALL patients. Ph- B-ALL patients with JAK-STAT signal pathway related gene mutation, such as JAK1/JAK2 mutation showed a poor prognosis compared to the patients without mutation (OS: P=0.011, 0.001; RFS: P=0.014,<0.001). Patients with PTPN11 mutation showed better survival than those without mutation, but the difference was not statistically significant (P value > 0.05). Besides, in Ph+ B-ALL patients whose epigenetic modifications related signaling pathway genes were affected, they had a worse prognosis (OS: P=0.038; RFS: P=0.047). Conclusion: Gene mutations are common in adult ALL patients, a variety of signaling pathways are involved. The frequency and spectrum are varied in different types of B-ALL. JAK family gene mutation usually indicates poor prognosis. The co-occurrence of somatic mutations in adult B-ALL patients indicate the genetic complex and instability of adult B-ALL patients.

Mutational status of NRAS, KRAS, and PTPN11 genes is associated with genetic/cytogenetic features in children with B-precursor acute lymphoblastic leukemia

BACKGROUND

We aimed to investigate the frequencies and the association with genetic/cytogenetic abnormalities as well as prognostic relevance of RAS pathway mutations in Taiwanese children with B-precursor acute lymphoblastic leukemia (ALL), the largest cohort in Asians.

PROCEDURE

Between 1995 and 2012, marrow samples at diagnosis from 535 children were studied for NRAS, KRAS, and PTPN11 mutations. The mutational status of each gene was correlated with the clinico-hematological features, recurrent genetic abnormalities, and outcomes for those treated with TPOG-ALL-2002 protocol (n = 346).

RESULTS

The frequencies of NRAS, KRAS, and PTPN11 mutations were 10.8% (57/530), 10.2% (54/530), and 3.0% (16/526), respectively. NRAS mutations were associated with a higher frequency of hyperdiploidy (P = 0.01) and lower frequency of ETV6-RUNX1 (P < 0.01), whereas KRAS mutations were associated with younger age (P < 0.01), a higher frequency of KMT2A rearranged (P < 0.01) but no significant difference if infants with ALL were excluded, and inferior event-free survival (66.6% vs. 80.5%, P = 0.04). None of patients with TCF3-PBX1 had KRAS mutation (P = 0.02).

CONCLUSIONS

Our study showed that the frequency of KRAS mutations in Taiwan was significantly higher than that reported in Caucasians. The occurrence of RAS pathway mutations was associated with recurrent genetic/cytogenetic abnormalities in pediatric B-precursor ALL.

The role of RAS mutations in MLL-rearranged leukaemia: A path to intervention?

Childhood acute lymphoblastic leukaemia (ALL) with MLL rearrangement (MLL-r) is an aggressive disease still associated with a high mortality rate. Recent investigations have identified co-operating mutations in the RAS pathway and although the functional consequences of these mutations are not yet fully understood, aberrant regulation of RAS pathway signalling at both transcriptional and protein levels is observed. Studies investigating the efficacy of specific inhibitors of this pathway, e.g. MEK-inhibitors, have also achieved encouraging results. In this context, this mini-review summarizes the available data surrounding MLL-r infant ALL with RAS mutation in relation to other well-known features of this intriguing disease.

Cooperation of MLL/AF10(OM-LZ) with PTPN11 activating mutation induced monocytic leukemia with a shorter latency in a mouse bone marrow transplantation model

PTPN11 mutation, a RAS signaling pathway mutation, is associated with MLL translocations in acute leukemia. A girl with MLL/AF10 AML was found to carry PTPN11^G503A . To study the impact of PTPN11^G503A cooperating with MLL/AF10 on leukemogenesis, we established a retroviral transduction/transplantation mouse model. Compared to the MLL/AF10(OM-LZ) leukemia cells harboring PTPN11^wt , the cells harboring PTPN11^G503A were hypersensitive to GM-CSF and IL3, and more resistant to death upon treatment with daunorubicin but sensitive to cytarabine. The cells harboring PTPN11^G503A autonomously differentiated into macrophages (1.8%) in the medium containing IL3. Further studies showed that the cells had an elevated (∼2.9-fold) Csf1 transcription level and secreted more (∼4.5-fold) M-CSF to the medium which can stimulate monocyte/macrophage differentiation of BM cells. Mice transplanted with the cells harboring PTPN11^G503A had a higher concentration of M-CSF in plasma. When mixed with the MLL/AF10(OM-LZ) leukemia cells harboring PTPN11^wt , the cells harboring PTPN11^G503A had an increased competitive engraftment and clonal expansion in the BM and spleen of recipient mice, although no competitive growth advantage was observed in the in vitro co-culturing assays. The mice transplanted with the MLL/AF10(OM-LZ) cells harboring PTPN11^wt developed myelomonocytic leukemia, while those transplanted with the cells harboring PTPN11^G503A -induced monocytic leukemia in a shorter latency. Our results demonstrated that addition of PTPN11^G503A to MLL/AF10 affected cell proliferation, chemo-resistance, differentiation, in vivo BM recruitment/clonal expansion and accelerated disease progression.

Proteomics-based discovery of biomarkers for paediatric acute lymphoblastic leukaemia: challenges and opportunities

There are important breakthroughs in the treatment of paediatric acute lymphoblastic leukaemia (ALL) since 1950, by which the prognosis of the child majority suffered from ALL has been improved. However, there are urgent needs to have disease-specific biomarkers to monitor the therapeutic efficacy and predict the patient prognosis. The present study overviewed proteomics-based research on paediatric ALL to discuss important advances to combat cancer cells and search novel and real protein biomarkers of resistance or sensitivity to drugs which target the signalling networks. We highlighted the importance and significance of a proper phospho-quantitative design and strategy for paediatric ALL between relapse and remission, when human body fluids from cerebrospinal, peripheral blood, or bone-marrow were applied. The present article also assessed the schedule for the analysis of body fluids from patients at different states, importance of proteomics-based tools to discover ALL-specific and sensitive biomarkers, to stimulate paediatric ALL research via proteomics to ‘build’ the reference map of the signalling networks from leukemic cells at relapse, and to monitor significant clinical therapies for ALL-relapse.