Evaluation of next-generation sequencing for measurable residual disease monitoring in three major fusion transcript subtypes of B-precursor acute lymphoblastic leukaemia.

The use of next-generation sequencing (NGS) for monitoring measurable residual disease (MRD) in acute lymphoblastic leukaemia (ALL) has been gaining traction. This study aimed to investigate the utility of NGS in MRD monitoring for the three major fusion transcript (FT) subtypes of B-precursor ALL (B-ALL). The MRD results for 104 bone marrow samples from 56 patients were analysed through NGS and real time quantitative reverse transcription PCR (RT-qPCR) for the three major FTs: BCR::ABL1, TCF3::PBX1, and ETV6::RUNX1. To validate the NGS approach, NGS-MRD was initially compared with allele-specific oligonucleotide-qPCR-MRD, and the coefficient of determination was good (R2=0.8158). A subsequent comparison of NGS-MRD with FT-MRD yielded a good coefficient of determination (R2=0.7690), but the coefficient varied by subtype. Specifically, the R2 was excellent for TCF3::PBX1 ALL (R2=0.9157), good for ETV6::RUNX1 ALL (R2=0.8606), and subpar for BCR::ABL1 ALL (R2=0.5763). The overall concordance between the two methods was 83.7%, and an excellent concordance rate of 95.8% was achieved for TCF3::PBX1 ALL. Major discordance, which was defined as a >1 log difference between discordant NGS-MRD and FT-MRD, occurred in 6.7% of the samples, with all but one sample being BCR::ABL1 ALL. Among the four non-transplanted patients with BCR::ABL1-MRD (+)/NGS-MRD (-), three did not relapse after long-term follow-up. Our finding indicates that NGS-MRD has a better prognostic impact than RT-qPCR-MRD in ETV6::RUNX1 and BCR::ABL1 ALL, whereas in TCF3::PBX1 ALL, both methods exhibit comparable efficacy.

Real world outcome of B ALL with t (1; 19) (q23; p13)/TCF3::PBX1 in adolescents and adults treated with intensive regimes.

Significant heterogeneity has been reported in outcome of Acute lymphoblastic leukemia with t(1;19)(q23;p13)/TCF3::PBX1 in adolescents and adults leading to a lack of consensus on precise risk stratification. We evaluated clinical outcome of 17 adult ALL cases (≥15 years) with this genotype treated on intensive regimes.13/17 received COG0232 and 4/17 cases received UK-ALL protocol. All achieved CR (100%) with above treatment. End of induction MRD was evaluated in 14/17 cases of which 11 (78.5%) achieved MRD negativity. Total nine patients relapsed (7 marrows, 2 CNS). Overall survival at 2 years was 53.3%. The 2 year estimated PFS was 42.9%. The 2 years CIR was 54.2%. Adults with this genotype perform poorly despite early favorable response. Incorporation of novel immunotherapies and prompt HSCT should be strongly considered with this genotype. Targeted NGS panels for additional genetic aberrations can further help in risk stratifying and guiding therapy for this genotype.

CircRNAome of Childhood Acute Lymphoblastic Leukemia: Deciphering Subtype-Specific Expression Profiles and Involvement in TCF3::PBX1 ALL.

Childhood B-cell acute lymphoblastic leukemia (B-ALL) is a heterogeneous disease comprising multiple molecular subgroups with subtype-specific expression profiles. Recently, a new type of ncRNA, termed circular RNA (circRNA), has emerged as a promising biomarker in cancer, but little is known about their role in childhood B-ALL. Here, through RNA-seq analysis in 105 childhood B-ALL patients comprising six genetic subtypes and seven B-cell controls from two independent cohorts we demonstrated that circRNAs properly stratified B-ALL subtypes. By differential expression analysis of each subtype vs. controls, 156 overexpressed and 134 underexpressed circRNAs were identified consistently in at least one subtype, most of them with subtype-specific expression. TCF3::PBX1 subtype was the one with the highest number of unique and overexpressed circRNAs, and the circRNA signature could effectively discriminate new patients with TCF3::PBX1 subtype from others. Our results indicated that NUDT21, an RNA-binding protein (RBP) involved in circRNA biogenesis, may contribute to this circRNA enrichment in TCF3::PBX1 ALL. Further functional characterization using the CRISPR-Cas13d system demonstrated that circBARD1, overexpressed in TCF3::PBX1 patients and regulated by NUDT21, might be involved in leukemogenesis through the activation of p38 via hsa-miR-153-5p. Our results suggest that circRNAs could play a role in the pathogenesis of childhood B-ALL.

[Clinical Significance of Minimal Residual Disease in Pediatric Patients with TCF3/PBX1+ B-cell Acute Lymphoblastic Leukemia].

OBJECTIVE: To explore the consistency of flow cytometry (FCM) method and polymerase chain reaction (PCR) technique in the detection of minimal residual disease (MRD) at different treatment stages in pediatric patients with TCF3/PBX1+ B-cell acute lymphoblastic leukemia (B-ALL) and the correlations between the detection results and prognosis. METHODS: The clinical data of 64 newly diagnosed pediatric patients with TCF3/PBX1+ B-ALL admitted to the Department of Pediatrics of Peking University People's Hospital from January 2005 to December 2017 were retrospectively analyzed. FCM and PCR methods were used to monitor the MRD level in bone marrow samples from 64 children during the same period of treatment on d33 and d90 respectively, and the detection results were analyzed. RESULTS: There were 37 males and 27 females in the 64 patients, with a median age of 8 years(range 0.8 to 16 years). The complete remission (CR) rate after the first cycle of induction chemotherapy was 98.4% (62/63), with overall CR rate of 100%. 12 patients experienced recurrence, with a median recurrence time of 16.9 (5.3-46.3) months. The median follow-up time of the 64 patients was 77.2 (1.0-184.8) months , and the 5-year overall survival (OS) rate and event-free survival (EFS) rate were 82.8%±4.7% and 75.0%±5.4%, respectively. On d90, the concordance rate of the MRD results from the two methods was 98.4%, and the related kappa value was 0.792 (P < 0.001), which were significantly higher than those on d33. After induction chemotherapy (d33), the 5-year EFS rate of MRD-FCM- group (79.3%±5.3%) was significantly better than that of MRD-FCM+ group (40.0%±21.9%) (P =0.028), there were no significant differences in the 5-year OS rate and EFS rate between MRD-PCR+ group and MRD-PCR- group, and the 5-year EFS rate of MRD-FCM-/PCR- group (85.4%±5.5%) was significantly better than that of MRD-FCM+/PCR+ group (40.0 %±21.9%) (P =0.026). CONCLUSION: In children with TCF3/PBX1+ B-ALL, the MRD results detected by FCM and PCR methods show good consistency, especially in consolidation therapy period (d90). The MRD level at the end of induction therapy (d33) is an important factor affecting the long-term prognosis, especially the MRD results detected by FCM method, which is significantly associated with prognosis.

Prognostic factors of childhood acute lymphoblastic leukemia with TCF3::PBX1 in CCCG-ALL-2015: A multicenter study.

BACKGROUND: Contemporary risk-directed treatment has improved the outcome of patients with acute lymphoblastic leukemia (ALL) and TCF3::PBX1 fusion. In this study, the authors seek to identify prognostic factors that can be used to further improve outcome. METHODS: The authors studied 384 patients with this genotype treated on Chinese Children's Cancer Group ALL-2015 protocol between January 1, 2015 and December 31, 2019. All patients provisionally received intensified chemotherapy in the intermediate-risk arm without prophylactic cranial irradiation; those with high minimal residual disease (MRD) ≥1% at day 46 (end) of remission induction were candidates for hematopoietic cell transplantation. RESULTS: The overall 5-year event-free survival was 84.4% (95% confidence interval [CI], 80.6-88.3) and 5-year overall survival 88.9% (95% CI, 85.5-92.4). Independent factors associated with lower 5-year event-free survival were male sex (80.4%, [95% CI, 74.8-86.4] vs. 88.9%, [95% CI, 84.1-93.9] in female, p = .03) and positive day 46 MRD (≥0.01%) (62.1%, [95% CI, 44.2-87.4] vs. 87.1%, [95% CI, 83.4-90.9] in patients with negative MRD, p < .001). The presence of testicular leukemia at diagnosis (n = 10) was associated with particularly dismal 5-year event-free survival (33.3% [95% CI, 11.6-96.1] vs. 83.0% [95% CI, 77.5-88.9] in the other 192 male patients, p < .001) and was an independent risk factor (hazard ratio [HR], 5.7; [95% CI, 2.2-14.5], p < .001). CONCLUSIONS: These data suggest that the presence of positive MRD after intensive remission induction and testicular leukemia at diagnosis are indicators for new molecular therapeutics or immunotherapy in patients with TCF3::PBX1 ALL.

Extended vincristine and dexamethasone pulse therapy may not be necessary for children with TCF3-PBX1 positive acute lymphoblastic leukaemia.

The effect of prolonged pulse therapy with vincristine and dexamethasone (VD) during maintenance therapy on the outcome of paediatric patients with TCF3-PBX1 positive acute lymphoblastic leukaemia (ALL) remains uncertain. We conducted non-inferiority analysis of 263 newly diagnosed TCF3-PBX1 positive ALL children who were stratified and randomly assigned (1:1) to receive seven additional VD pulses (the control group) or not (the experimental group) in the CCCG-ALL-2015 clinical trial from January 2015 to December 2019 (ChiCTR-IPR-14005706). There was no significant difference in baseline characteristics between the two groups. With a median follow-up of 4.2 years, the 5-year event-free survival (EFS) and 5-year overall survival (OS) in the control group were 90.1% (95% confidence interval [CI] 85.1-95.4) and 94.7% (95% CI, 90.9-98.6) comparable to those in the experimental group 89.2% (95% CI 84.1-94.7) and 95.6% (95% CI 91.8-99.6), respectively. Non-inferiority was established as a one-sided 95% upper confidence bound for the difference in probability of 5-year EFS was 0.003, and that for 5-year OS was 0.01 by as-treated analysis. Thus, omission of pulse therapy with VD beyond one year of treatment did not affect the outcome of children with TCF3-PBX1 positive ALL.

Commonly Assessed Markers in Childhood BCP-ALL Diagnostic Panels and Their Association with Genetic Aberrations and Outcome Prediction.

Immunophenotypic characterization of leukemic cells with the use of flow cytometry (FC) is a fundamental tool in acute lymphoblastic leukemia (ALL) diagnostics. A variety of genetic aberrations underlie specific B-cell precursor ALL (BCP-ALL) subtypes and their identification is of great importance for risk group stratification. These aberrations include: ETV6::RUNX1 fusion gene, Philadelphia chromosome (BCR::ABL1 fusion gene), rearrangements of the KMT2A, TCF3::PBX1 fusion gene and changes in chromosome number (hyperdiploidy and hypodiploidy). Diagnostic panels for BCP-ALL usually include B-cell lineage specific antigens: CD19, CD10, CD20, maturation stage markers: CD34, CD10, CD38, TdT, IgM and other markers useful for possible genetic subtype indication. Some genetic features of leukemic cells (blasts) are associated with expression of certain antigens. This review comprehensively summarizes all known research data on genotype-immunophenotype correlations in BCP-ALL. In some cases, single molecules are predictive of particular genetic subtypes, i.e., NG2 with KMT2A gene rearrangements or CD123 with hyperdiploidy. However, much more information on possible genotype or prognosis can be obtained with wider (≥8-color) panels. In several studies, a quantitative antigen expression scale and advanced statistical analyses were used to further increase the specificity and sensitivity of genotype/immunophenotype correlation detection. Fast detection of possible genotype/immunophenotype correlations makes multicolor flow cytometry an essential tool for initial leukemia diagnostics and stratification.

Underexpression of LINC00173 in TCF3/PBX1-Positive Cases Is Associated With Poor Prognosis in Children With B-Cell Precursor Acute Lymphoblastic Leukemia.

Background: B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most frequent pediatric cancer worldwide. Despite improvements in treatment regimens, approximately 20% of the cases cannot be cured, highlighting the necessity for identifying new biomarkers to improve the current clinical and molecular risk stratification schemes. We aimed to investigate whether LINC00173 is a biomarker in ALL and to explore its expression level in other human cancer types. Methods: A nested case-control study including Mexican children with BCP-ALL was conducted. LINC00173 expression was evaluated by qRT-PCR using hydrolysis probes. To validate our findings, RNA-seq expression data from BCP-ALL and normal tissues were retrieved from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Genotype-Tissue Expression (GTEx) repositories, respectively. LINC00173 expression was also evaluated in solid tumors by downloading available data from The Cancer Genome Atlas (TCGA). Results: A lower expression of LINC00173 in BCP-ALL cases compared to normal subjects was observed (p < 0.05). ALL patients who carry the TCF3/PBX1 fusion gene displayed lower expression of LINC00173 in contrast to other BCP-ALL molecular subtypes (p < 0.04). LINC00173 underexpression was associated with a high risk to relapse (HR = 1.946, 95% CI = 1.213-3.120) and die (HR = 2.073, 95% CI = 1.211-3.547). Patients with TCF3/PBX1 and underexpression of LINC00173 had the worst prognosis (DFS: HR = 12.24, 95% CI = 5.04-29.71; OS: HR = 11.19, 95% CI = 26-32). TCGA data analysis revealed that underexpression of LINC00173 is also associated with poor clinical outcomes in six new reported tumor types. Conclusion: Our findings suggest that LINC00173 is a biomarker of poor prognosis in BCP-ALL and other types of cancer. We observed an association between the expression of LINC00173 and TCF3/PBX1 and the risk to relapse and die in BCP-ALL, which is worse in TCF3/PBX1-positive cases displaying underexpression of LINC00173. Experimental studies are needed to provide insight into the LINC00173 and TCF3/PBX relationship.

Incidence and Prognostic Impact of TCF3-PBX1 Fusion in Childhood Acute Lymphoblastic Leukemia: A Single Centre Experience.

Molecular abnormalities in leukemic cells are important determinants of risk stratification in Pediatric acute lymphoblastic leukemia (ALL). TCF3-PBX1 fusion is one of the common aberrations in ALL with doubtful prognostic significance. Therefore, aim of our study is to revisit the clinical characteristics and outcome of this abnormality in children with ALL treated at our institute.Demographic, Clinical and treatment related characteristics of 539 newly diagnosed ALL patients from January 2009 and December 2018, < 18 years of age treated on BFM-95 protocol, was abstracted from the medical records. Clinical characteristics and outcome of children with and without TCF3-PBX1 fusion was compared.Incidence of TCF3-PBX1 fusion was observed in 24/539(4.4%) patients with a median age of 4 years (range 1-17). None of the patients in TCF3-PBX1 group had CNS or testicular disease at presentation. Day -8 prednisolone response and morphological remission at the end of induction was similar in both study groups. 5-year overall and event free survival for those with and without fusion was 75%, 70.1% and 79.5%, 69.5% respectively.The incidence of TCF3-PBX1 fusion in the present study was 4.4% and it does not have an independent prognostic significance.

Prognostic heterogeneity of adult B-cell precursor acute lymphoblastic leukaemia patients with t(1;19)(q23;p13)/TCF3-PBX1 treated with measurable residual disease-oriented protocols.

The prognosis of t(1;19)(q23;p13)/transcription factor 3-pre-B-cell leukaemia homeobox 1 (TCF3-PBX1) in adolescent and adult patients with acute lymphoblastic leukaemia (ALL) treated with measurable residual disease (MRD)-oriented trials remains controversial. In the present study, we analysed the outcome of adolescent and adult patients with t(1;19)(q23;p13) enrolled in paediatric-inspired trials. The patients with TCF3-PBX1 showed similar MRD clearance and did not have different survival compared with other B-cell precursor ALL patients. However, patients with TCF3-PBX1 had a significantly higher cumulative incidence of relapse, especially among patients aged ≥35 years carrying additional cytogenetic alterations. These patients might benefit from additional/intensified therapy (e.g. immunotherapy in first complete remission with or without subsequent haematopoietic stem cell transplantation).

Genetic features of B-cell lymphoblastic lymphoma with TCF3-PBX1.

BACKGROUND: Lymphoblastic lymphoma (LBL) and acute lymphoblastic leukemia (ALL) are categorized as the same entity under precursor lymphoid neoplasms in the World Health Organization classification. However, compared to B-cell ALL, the molecular genetic makeup of B-cell LBL remains to be understood, mainly due to its rarity. We performed whole exome sequencing (WES) on seven patients with TCF3-PBX1-positive B-cell LBL. METHODS: WES was performed using DNA extracted from tumor specimens and paired blood samples at remission for six patients, and tumor-only analysis was performed for one patient whose remission sample was not available. For one patient, a relapsed sample was also analyzed. RESULTS: KMT2D variants and 6q LOH were found as recurrent alterations. Somatic variants of KMT2D were identified in three of the seven patients. Of note, the two patients with heterozygous nonsense variant of KMT2D were at stage III, without bone marrow infiltration. 6q LOH was also identified in two others, out of the seven patients. The common 6q deleted region of the two patients ranged from 6q12 to 6q16.3. Both patients had bone marrow infiltration. Analysis of recurrent case also revealed that the relapsed clone might be derived from a minor clone of the bone marrow at diagnosis. CONCLUSION: In this study, through WES for seven patients with TCF3-PBX1-positive B-LBL, we identified KMT2D mutations and 6q LOH as recurrent alterations. In order to elucidate the relationship between these recurrent alterations and disease specificity or outcomes, further studies comparing with TCF3-PBX1-positive B-ALL are required.

Cytogenetic and Fluorescence in situ Hybridization Profile of Pediatric Acute Lymphoblastic Leukemia in a University Hospital in South India.

OBJECTIVE: The purpose of this study was to evaluate the cytogenetic and fluorescent in situ hybridization (FISH) profile in children with acute lymphoblastic leukemia (ALL), referred to a university hospital in a 5-year 6-month period. SUBJECTS AND METHODS: Cytogenetic analysis of the bone marrow aspirate specimens of 91 patients was performed by standard Giemsa (G)-banding and interphase FISH (iFISH). RESULTS: The frequency of chromosomal abnormalities detected by G-banding was 29.5%, and the frequency of nonrandom abnormalities with independent prognostic significance identified by iFISH was 46.4%. The abnormality with the highest frequency was gain of RUNX1 (n = 18, 21.4%), followed by ETV6/RUNX1 fusion (n = 7, 8.3%), and gain of KMT2A (n = 6, 7.1%). Additionally, rarely reported gains of ETV6, PBX1, and ABL1 were observed at a frequency of 6% (n = 5), and the deletion of ETV6 and TCF3 was seen at a frequency of 3.6% (n = 3) and 2.3% (n = 2), respectively. A 10-year old with intrachromosomal amplification of chromosome 21 was also observed. CONCLUSIONS: This study strengthens and widens the current knowledge of the cytogenetic landscape of pediatric ALL.

Clinical features and prognostic impact of TCF3-PBX1 in childhood acute lymphoblastic leukemia: A single-center retrospective study of 837 patients from China.

OBJECTIVES: Conflicting data have been published regarding the prognostic impact of the t(1;19)/TCF3-PBX1 translocation in childhood ALL. The objective of this study was to explore the correlation between the TCF3-PBX1 fusion gene and clinical outcome in Chinese children with newly diagnosed ALL. METHODS: In order to address this issue in our setting, we summarized and analyzed the data of 837 Chinese children with ALL diagnosed between 2010 and 2017. All the patients were treated with the National Protocol of Childhood Leukemia in China (NPCLC)-ALL-2008 protocol. Clinical characteristics and prognosis of pediatric ALL patients with or without TCF3-PBX1 rearrangement were analyzed and compared retrospectively. RESULTS: The TCF3-PBX1 fusion gene was identified in 48 (5.7%) of 837 children with ALL. Our results showed that TCF3-PBX1 positive patients had higher pretreatment white blood cell counts, higher PB blasts percentages and worse risk classification at diagnosis. No statistically significant differences in CR rates, response to prednisone and relapse rates were found between TCF3-PBX1-positive and -negative patients. The 5-year predicted EFS, RFS, and OS of the TCF3-PBX1 positive group compared with the control group were 86.2%±5.3% vs 85.4%±1.3% (P=0.657), 88.2%±5.1% vs 92.2%±1.0% (P=0.458) and 90.4%±4.6% vs 89.0%±1.1% (P=0.561), respectively. No differences were observed regarding clinical outcome between these two groups. When compared with standard risk, intermediate risk and high risk group patients, the long-term survival of TCF3/PBX1 positive group was approximately similar to that of the intermediate risk group under the same protocol in our single center. CONCLUSION: In contrast to previous studies, childhood ALL patients with TCF3-PBX1 transcripts do not appear to show a better outcome than their negative counterparts. TCF3/PBX1 positive was a definitive intermediate risk factor with our NPCLC-ALL-2008 protocol.

CRLF2 and IKZF1 abnormalities in Mexican children with acute lymphoblastic leukemia and recurrent gene fusions: exploring surrogate markers of signaling pathways.

The gene fusions BCR-ABL1, TCF3-PBX1, and ETV6-RUNX1 are recurrent in B-cell acute lymphoblastic leukemia (B-ALL) and are found with low frequency in coexistence with CRLF2 (cytokine receptor-like factor 2) rearrangements and overexpression. There is limited information regarding the CRLF2 abnormalities and dominant-negative IKZF1 isoforms associated with surrogate markers of Jak2, ABL, and Ras signaling pathways. To assess this, we evaluated 24 Mexican children with B-ALL positive for recurrent gene fusions at diagnosis. We found CRLF2 rearrangements and/or overexpression, dominant-negative IKZF1 isoforms, and surrogate phosphorylated markers of signaling pathways coexisting with recurrent gene fusions. All the BCR-ABL1 patients expressed CRLF2 and were positive for pCrkl (ABL); most of them were also positive for pStat5 (Jak2/Stat5) and negative for pErk (Ras). TCF3-PBX1 patients with CRLF2 abnormalities were positive for pStat5, most of them were also positive for pCrkl, and two patients were also positive for pErk. One patient with ETV6-RUNX1 and intracellular CRLF2 protein expressed pCrkl. In some cases, the activated signaling pathways were reverted in vitro by specific inhibitors. We further analyzed a TCF3-PBX1 patient at relapse, identifying a clone with the recurrent gene fusion, P2RY8-CRLF2, rearrangement, and phosphorylation of the three surrogate markers that we studied. These results agree with the previous reports regarding resistance to treatment observed in patients with recurrent gene fusions and coexisting CRLF2 gene abnormalities. A marker phosphorylation signature was identified in BCR-ABL1 and TCF3-PBX1 patients. To obtain useful information for the assessment of treatment in B-ALL patients with recurrent gene fusions, we suggest that they should be evaluated at diagnosis for CRLF2 gene abnormalities and dominant-negative IKZF1 isoforms, in addition to the analyses of activation and inhibition of signaling pathways.

Translocation t(1;19)(q23;p13) in adult acute lymphoblastic leukemia - a distinct subtype with favorable prognosis.

The recurring translocation t(1;19) (q23;p13) with TCF3-PBX1 rearrangements are uncommon in adult acute lymphoblastic leukemia (ALL), and their prognostic impact remains to be described in the era of modern chemotherapies. We investigated 427 adult patients with newly diagnosed pre-B ALL, 16 (4%) had t(1;19)(q23;p13) at diagnosis. All 16 patients achieved complete remission after induction with intensive chemotherapy, and with a median of 7-year follow-up, 2 relapsed. The 5-year cumulative incidence of relapse and overall survival rates were 14% and 82%, respectively. Our analysis showed that adult patients with t(1;19)(q23;p13) positive ALL had favorable prognosis with intensive chemotherapy regimens.

Long-Term Results of the Risk-Stratified Treatment of TCF3-PBX1-Positive Pediatric Acute Lymphoblastic Leukemia in China.

BACKGROUND: Acute lymphoblastic leukemia (ALL) with t(1;19)/TCF3-PBX1 is a common genotype, and its prognosis has significantly improved owing to risk stratification and intensive treatment. This study aimed to determine the outcomes and prognostic factors of patients with TCF3-PBX1 treated with the modified Berlin-Frankfurt-Münster protocol. PATIENTS AND METHODS: Between 2005 and 2017, a total of 1051 pediatric patients with ALL were enrolled. TCF3-PBX1 was detected by reverse-transcriptase PCR and/or cytogenetic analysis. Clinical characteristics and treatment outcomes were analyzed and compared in patients with TCF3-PBX1 and with other B-precursor ALL (B-ALL). RESULTS: TCF3-PBX1 was detected in 64 patients with ALL (6.1%), and all were of B-cell lineage. These patients were more likely to express the pre-B-ALL immunophenotype (P < .001), be in the National Cancer Institute high-risk group (P = .030), and exhibit more rapid disease clearance during induction therapy (P < .001) compared to patients with other B-ALL. However, the outcomes of this genotype were not better than those of other patients with intermediate risk. At a median (range) follow-up of 60.6 (0.8-184.5) months, the estimated 5-year overall survival was 85.2 ± 4.6% versus 88.2 ± 1.8% (P = .500) and 5-year event-free survival was 76.8 ± 5.5% versus 83.0 ± 2.0% (P = .210) for patients with TCF3-PBX1 and those with other B-ALL. After adjusting for other risk factors, reemergent minimal residual disease (MRD) was the most significant poor prognostic indicator for patients with TCF3-PBX1. CONCLUSION: The overall outcome of patients with TCF3-PBX1 was intermediate at our institution. Sequential MRD measurement is important for this genotype. Thus, more efforts should be made to eradicate reemergent MRD to improve prognosis.

Identificación de alteraciones moleculares en pacientes Venezolanos con diagnóstico de leucemia linfoblástica aguda / Identification of molecular alterations in Venezuelan patients with acute lymphoblastic leukemia diagnosis

La Leucemia Linfoblástica Aguda (LLA) es la neoplasia más frecuente en edad pediátrica. En los últimos años, entre el 15 y 20% de los pacientes fracasan en el tratamiento. Conocimientos en citogenética y biología molecular repercuten de manera importante en la determinación del pronóstico y del esquema de tratamiento adecuado. En Venezuela existe un conocimiento limitado en cuanto a la genética molecular de esta alteración onco-hematológica. El objetivo del trabajo fue evaluar las alteraciones genéticas más frecuentes en pacientes venezolanos con diagnóstico clínico de leucemia linfoblástica aguda. Se realizó un estudio transversal, descriptivo y prospectivo de 2006 a 2014, en el que se evaluaron las translocaciones ETV6/RUNX1, MLL/AF4, TCF3/PBX1, BCR/ABL1, así como las mutaciones en los genes PAX5 y FLT3 mediante el uso de diferentes tipos de PCR. Ciento treinta pacientes con diagnóstico clínico de leucemia linfocítica aguda fueron incluidos en el estudio. Se identificaron alteraciones moleculares en 56 pacientes (43,1%), en los que observamos la presencia de una o varias alteraciones en conjunción en un mismo paciente. Las alteraciones identificadas fueron t(12;21) (11,5%), t(4;11) (8,5%), t(1;19) (10%), t(9;22) (20,8%), ITD-FLT3 (14,8%), mutación P80S (4,2%) y S77del (4,2%) en el gen PAX5. La prevalencia de BCR/ ABL, es una de las más altas que ha sido descrita hasta ahora en casos de LLA donde la mayor parte de la población está conformada por pacientes pediátricos. Estos resultados representan el primer estudio molecular de la LLA en Venezuela, sentando las bases para el diagnóstico y seguimiento de la enfermedad en su población.

Acute Lymphoblastic Leukemia (ALL) is the most common neoplasm in pediatric age. In recent years, between 15 and 20% of patients failed in their treatments. Knowledge on cytogenetics and molecular biology has an important impact on the determination of the prognosis and the appropriate treatment scheme. In Venezuela there is limited knowledge regarding the molecular genetics of this onco-hematological alteration. The aim of this work was to evaluate the most frequent genetic alterations in Venezuelan patients with a clinical diagnosis of acute lymphoblastic leukemia. A cross-sectional, descriptive and prospective study was carried out from 2006 to 2014, in which the translocations ETV6/RUNX1, MLL/AF4, TCF3/PBX1, BCR/ABL1, as well as mutations in the PAX5 and FLT3 genes were evaluated through the use of different types of PCR. One hundred and thirty patients with a clinical diagnosis of acute lymphocytic leukemia were included in the study. Molecular alterations were identified in 56 patients (43.1%), in which we observed the presence of one or several alterations in conjunction in the same patient. The alterations identified were t(12; 21) (11.5%), t(4; 11) (8.5%), t(1; 19) (10%), t(9; 22) (20.8%), ITD-FLT3 (14.8%), P80S mutation (4.2%) and S77del (4.2%) in the PAX5 gene. The prevalence of BCR/ABL is one of the highest described so far in cases of ALL where most of the population is made up of pediatric patients. These results represent the first molecular study of ALL in Venezuela, laying the foundations for the diagnosis and monitoring of the disease in its population.

A novel PAX5 rearrangement in TCF3-PBX1 acute lymphoblastic leukemia: a case report.

BACKGROUND: Chromosome translocations are a hallmark of B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Additional genomic aberrations are also crucial in both BCP-ALL leukemogenesis and treatment management. Herein, we report the phenotypic and molecular cytogenetic characterization of an extremely rare case of BCP-ALL harboring two concomitant leukemia-associated chromosome translocations: t(1;19)(q23;q13.3) and t(9;17)(p13;q11.2). Of note, we described a new rearrangement between exon 6 of PAX5 and a 17q11.2 region, where intron 3 of SPECC1 is located. This rearrangement seems to disrupt PAX5 similarly to a PAX5 deletion. Furthermore, a distinct karyotype between diagnosis and relapse samples was observed, disclosing a complex clonal evolution during leukemia progression. CASE PRESENTATION: A 16-year-old boy was admitted febrile with abdominal and joint pain. At clinical investigation, he presented with anemia, splenomegaly, low white blood cell count and 92% lymphoblast. He was diagnosed with pre-B ALL and treated according to high risk GBTLI-ALL2009. Twelve months after complete remission, he developed a relapse in consequence of a high central nervous system and bone marrow infiltration, and unfortunately died. CONCLUSIONS: To our knowledge, this is the first report of a rearrangement between PAX5 and SPECC1. The presence of TCF3-PBX1 and PAX5-rearrangement at diagnosis and relapse indicates that both might have participated in the malignant transformation disease maintenance and dismal outcome.