scholarly journals Loss of PTEN in Pediatric T-Cell Acute Lymphoblastic Leukemia Patients: Proteomic and Molecular Characterization

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2408-2408
Author(s):  
Paola Bonaccorso ◽  
Cristina Bugarin ◽  
Chiara Buracchi ◽  
Grazia Fazio ◽  
Maddalena Paganin ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Protein Extraction ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Strong Association ◽  
Mtor Pathway ◽  
Wild Type ◽  
Pten Protein ◽  
Cell Acute Lymphoblastic Leukemia

Abstract Signaling networks such as the PI3K/Akt/PTEN/mTOR pathway play a role in the modulation of the aggressiveness of T-Cell Acute Lymphoblastic Leukemia (T-ALL), but the significance of an aberrant activation of this pathway is poorly investigated. The master regulator of PI3K-AKT signaling is the lipid phosphatase and tensin homolog (PTEN); decreased or absent PTEN expression or activity could be associated with a constitutive activation of PI3K/Akt/PTEN/mTOR signaling pathway in T-ALLs. We investigated PTEN Exon7 mutations in diagnostic DNA samples from 67 pediatric T-ALL enrolled in AIEOP ALL2000 and R2006 protocols according to methods by Bandapalli et al. (Haematologica, 2012). We also investigated the PI3K/Akt/PTEN/mTOR pathway using Western Blotting (WB) and Flow Cytometry (FC) in parallel. WB analysis was performed using standard RIPA buffer for protein extraction. FC analysis of protein expression was applied as previously described (Gaipa G et al, Leukemia 2008), and protein levels were measured as % of positive cells compared to isotype control. Positivity or negativity by WB was established by presence or absence of a protein band, while for FC a threshold for positivity was set at ≥ 1% of positive cells. PTEN Exon 7 mutations were identified in 11 out of 67 (16.4%) of patients. According to samples availability, PI3K/Akt/PTEN/mTOR pathway was studied in 9 out of 67 patients (3 PTEN Exon 7 mutated and 6 wild type). PTEN protein resulted completely absent in all three PTEN Exon 7 mutated patients, by contrast PTEN was expressed in all 6 PTEN exon 7 wild type patients (mean by FC 46.98% ± 28.58%). This finding was fully confirmed when WB was applied to the same samples. We did not observe any statistically significant differences in p4EBP1 or mTOR levels in Exon 7 mutated patients as compared to wild type. By contrast, PTEN Exon 7 mutated blasts showed lower phospho-S6 levels compared to PTEN Exon7 wild type patients (mean 3.0% of positive cells vs 32.0%, p=ns). In conclusion, our data show a frequency of PTEN Exon 7 mutations of 16.4%, in agreement with the report by Bandapalli et al. (17.3%). Interestingly, we observed a strong association between the PTEN Exon 7 mutation and the total absence of PTEN protein in the pediatric T-ALL patients studied (data not reported so far to our knowledge). Moreover, although the differences are not statistically significant, p-S6 expression resulted consistently lower in mutated patients as compared to wild type patients. If confirmed in a larger cohort of pediatric T-ALLs, our data could open new insights in the significance of PTEN Exon 7 mutation in pediatric T-ALL and its associated functional profile. Disclosures No relevant conflicts of interest to declare.

scholarly journals Phloridzin Docosahexaenoate (PZ-DHA) : A Novel Naturally Derived Drug Active in T-Cell Acute Lymphoblastic Leukemia (T-ALL)

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5197-5197
Author(s):  
Niroshaathevi Arumuggam ◽  
Nicole Melong ◽  
Catherine K.L. Too ◽  
Jason N. Berman ◽  
H.P. Vasantha Rupasinghe
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Xenograft Model ◽  
Jurkat Cells ◽  
Interferon Α ◽  
Omega 3 ◽  
Cell Acute Lymphoblastic Leukemia

Abstract T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignant disease that accounts for about 15% of pediatric and 25% of adult ALL. Although risk stratification has provided more tailored therapy and improved the overall survival of T-ALL patients, clinical challenges such as suboptimal drug responses, morbidity from drug toxicities, and drug resistance still exist. Plant polyphenols have therapeutic efficacy as pharmacological adjuvants to help overcome these challenges. They can be acylated with fatty acids to overcome issues concerning bioavailability, such as poor intestinal absorption and low metabolic stability. Phloridzin (PZ), a flavonoid found in apple peels, was acylated with an omega-3 fatty acid, docosahexaenoic acid (DHA), to generate a novel ester called phloridzin docosahexaenoate (PZ-DHA). The cytotoxic effect of PZ-DHA was studied in the human Jurkat T-ALL cell line. PZ-DHA significantly reduced the viability and cellular ATP levels of treated cells. PZ-DHA was found to selectively induce apoptosis in Jurkat cells, while sparing normal murine T-cells. Apoptosis was further confirmed by demonstrating the ability of PZ-DHA to induce morphological alterations, DNA fragmentation, caspase activation, and the release of intracellular lactate dehydrogenase. PZ-DHA also significantly inhibited cell division in Jurkat cells. Furthermore, interferon-α-induced phosphorylation of the transcription factor, STAT3, was downregulated following PZ-DHA treatment. The in vitro efficacy of PZ-DHA was recapitulated in vivo in an established zebrafish xenograft model, where the proliferation of transplanted Jurkat cells was inhibited when PZ-DHA was added to the embryo water. Overall, these findings provide evidence for PZ-DHA as a novel therapeutic agent with activity in T-ALL. Studies examining the effect of PZ-DHA on patient-derived ALL cells engrafted in zebrafish are currently underway. Disclosures No relevant conflicts of interest to declare.

scholarly journals The Role of Protein Tyrosine Phosphatase PTP4A3 in T-Cell Acute Lymphoblastic Leukemia Progression

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2539-2539
Author(s):  
Min Wei ◽  
Jessica Blackburn
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
T Cell Activation ◽  
Protein Tyrosine Phosphatase ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Tyrosine Phosphatase ◽  
Causative Role ◽  
Protein Tyrosine ◽  
Cell Acute Lymphoblastic Leukemia

The tyrosine protein tyrosine phosphatase PTP4A3 has been extensively reported to play a causative role in numerous cancers, including several types of acute leukemia. We found PTP4A3 to be highly expressed in T-cell Acute Lymphoblastic Leukemia samples, and show that PTP4A3 accelerates T-ALL onset and increases the invasive ability of T-ALL cells in a zebrafish model, and is required for T-ALL engraftment and progression in mouse xenograft. Our in vitro studies showed that PTP43A3 enhances T-ALL migration, in part via modulation of SRC signaling. However, whether SRC is a direct substrate of PTP4A3, and whether the phosphatase activity of PTP4A3 actually plays a role in T-ALL or other types of leukemia progression is unknown and remains a major question in the field. We used a BioID-based proximity labeling approach combined with PTP4A3 substrate trapping mutant pull down assay to capture the PTP4A3 substrates candidates. BioID, a biotin ligase, was fused to PTP4A3 to generate a Biotin-PTP4A3 (BP) fusion protein. The overexpression of BP in T-ALL cell lines led to biotin modification of 288 PTP4A3 proximal proteins, including the potential direct PTP4A3 substrates. PANTHER pathway analysis showed that PTP4A3 interacting proteins are largely clustered in the T-cell activation, PDGF signaling, and angiogenesis. We are in process of validating potential substrates using immunoprecipitation and phosphoenrichement assays. Finally, we are using a novel zebrafish Myc+PTP4A3 induced T-ALL model to assess the function of PTP4A3 in leukemia progression. We have created several PTP4A3 protein mutants, including a phosphatase-dead mutant, a mutant unable to bind magnesium transporter, and a prenylation deficient mutant, and are in process of assessing the effects of these mutants in T-ALL onset and progression in our in vivo model. In total, these studies will allow us to better understand function of PTP4A3 in T-ALL progression, and may provide a strong rationale for the development of PTP4A3 inhibitors for use in leukemia. Disclosures No relevant conflicts of interest to declare.

Essential Role for Mir-181a1/b1 In T-Cell Acute Lymphoblastic Leukemia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 470-470
Author(s):  
Ana Rita Fragoso ◽  
Tin Mao ◽  
Song Wang ◽  
Steven Schaffert ◽  
Hyeyoung Min ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Essential Role ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Cancer Development ◽  
Loss Of Function ◽  
Control Of Gene Expression ◽  
Mirna Genes ◽  
Cell Acute Lymphoblastic Leukemia

Abstract Abstract 470 MiRNA-mediated gene regulation represents a fundamental layer of post-transcriptional control of gene expression with diverse functional roles in normal development and tumorigenesis. Whereas some studies have shown that over-expression of miRNA genes may contribute to cancer development and progression, it is yet to be rigorously tested by the loss-of-function genetic approaches whether miRNA genes are required for cancer development and maintenance in mice. Here we show that mir-181a1/b1 coordinates Notch and pre-TCR signals during normal thymocyte differentiation and plays an essential role in development and onset of T-cell acute lymphoblastic leukemia (T-ALL) induced by some Notch mutations. Using gain-of-function and loss-of-function approaches, we demonstrated that mir-181a1/b1 controls Notch and pre-TCR receptor signals during the early stages of T cell development in the thymus by repressing multiple negative regulators of both pathways, including Nrarp, PTPN-22, SHP2, DUSP5, and DUSP6. These results illustrate that a single miRNA can coordinate multiple signaling pathways by modulating the timing and strength of signaling at different stages. Intriguingly, synergistic signaling between Notch and pre-TCR pathways is necessary for the development of T-ALL, and miR-181 family miRNAs are aberrantly expressed in T-ALL patients. These observations raise the possibility that mir-181a1/b1 might contribute to the onset or maintenance of T-ALL by targeting similar pathways in tumor cells as it does in normal thymic progenitor cells. In support of this notion, we found that loss of mir-181a1/b1 significantly delayed the onset and development of T-ALL induced by intracellular domain of Notch1 (ICN1) and caused a 32% increase in the median survival time from 41 days to 54 days in T-ALL mice. Importantly, we noted that loss of mir-181a1/b1 more efficiently repressed the leukemogeneic potential of cells with lower levels of ICN1 expression, suggesting that mir-181a1/b1 may be more effective in inhibiting T-ALL development induced by a Notch mutant with weaker signal strength. Indeed, we demonstrated that loss of mir-181a1b1 essentially blocked T-ALL development induced by the weaker Notch mutant and dramatically decreased mortality from 60% to 10% in these T-ALL mice. Since human Notch mutations identified in T-ALL patients generally have weaker signaling strength and lower oncogenic potential than that of ICN1, our findings indicate that mir-181a1/b1 may play an essential role in development of normal thymic progenitors and Notch-induced T-ALL and may be targeted to treat T-ALL patients harboring Notch mutations. Disclosures: No relevant conflicts of interest to declare.

Transcriptional Repression of the LMO2 Oncogene By Ikaros in T-Cell Acute Lymphoblastic Leukemia

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 439-439
Author(s):  
Yali Ding ◽  
Chunhua Song ◽  
Chandrika S. Gowda ◽  
Malika Kapadia ◽  
Kimberly Payne ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Chromatin Immunoprecipitation ◽  
Transcriptional Repression ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Transcriptional Level ◽  
Knock Down ◽  
Cell Acute Lymphoblastic Leukemia ◽  
Ck2 Inhibitors

Abstract LIM domain only protein 2 (LMO2) is a regulator of hematopoiesis and an oncogene that is overexpressed in a subset of T-cell acute lymphoblastic leukemia (T-ALL). Overexpression of LMO2 in T-ALL is associated with a poor prognosis. The mechanisms that regulate LMO2 expression in T-ALL are still unknown. Here, we present evidence that expression of LMO2 in T-ALL is regulated at the transcriptional level by Ikaros, a tumor suppressor protein whose deletion is associated with the development T-ALL. Global chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq) studies in primary human acute lymphoblastic leukemia cells and in cell lines demonstrated Ikaros occupancy of the LMO2 promoter. Ikaros binding at the LMO2 promoter was confirmed by quantitative chromatin immunoprecipitation (qChIP) in primary T-ALL and B-ALL cells. The role of Ikaros in the regulation of LMO2 transcription in T-ALL was tested using gain-of-function and loss-of-function experiments. Ikaros knock-down with siRNA resulted in increased transcription of LMO2 in T-ALL. Overexpression of Ikaros in human T-ALL was associated with strongly reduced transcription of LMO2. In mice, T-ALL cells that are derived from Ikaros-knockout mice express high levels of LMO2. Transduction of these cells with Ikaros-containing retrovirus, results in a sharp reduction of LMO2 expression. Since Ikaros function in T-ALL is negatively regulated by the pro-oncogenic Casein Kinase II (CK2), we tested whether CK2 inhibition can enhance Ikaros-mediated transcriptional repression of LMO2. Molecular inhibition of CK2 using shRNA, as well as pharmacological inhibition with a specific CK2 inhibitor, resulted in reduced expression of LMO2 in primary human T-ALL. Inhibition of CK2 was associated with increased Ikaros binding at the LMO2 promoter. Ikaros knock-down restored high expression of LMO2 in T-ALL cells that were treated with CK2 inhibitors. These data show that Ikaros is a major regulator of LMO2 transcription in T-ALL and that CK2 inhibition requires Ikaros activity to repress LMO2 transcription. Increased Ikaros binding was associated with reduced histone H3K9ac and H3K4me3 marks at the LMO2 promoter suggesting that Ikaros regulates LMO2 transcription via chromatin remodeling. In conclusion, these results provide evidence that expression of the LMO2 oncogene is regulated by Ikaros and CK2 in T-ALL. Targeting CK2 with specific inhibitors has been used as a therapeutic strategy in a preclinical model of T-ALL. The presented data reveal a novel mechanism of therapeutic action for CK2 inhibitors - repression of LMO2 expression via Ikaros. These results provide a rationale for the use of CK2 inhibitors in T-ALL with LMO2 overexpression. Disclosures No relevant conflicts of interest to declare.

scholarly journals Identification of a New Targeted Therapy for T-Cell Acute Lymphoblastic Leukemia and Studies on Its Mechanism of Action

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2752-2752
Author(s):  
Kinjal Shah ◽  
Julhash U. Kazi
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Predictive Biomarkers ◽  
Protein Kinase Inhibitors ◽  
Maturation Stage ◽  
Mrna Levels ◽  
Cell Acute Lymphoblastic Leukemia

Background: Acute lymphoblastic leukemia (ALL) is the most frequent pediatric malignancy, of which T- cell acute lymphoblastic leukemia (T-ALL) constitutes an aggressive subset. Due to the advent of new therapies, T-ALL now has a 5-year event-free survival (EFS) rate exceeding 85%. However, some patients still relapse and display resistance to therapy. Moreover, adverse side-effects of intensive chemotherapy worsen the duration of treatment. Therefore, we still need to improve our current treatment beyond that of the chemotherapeutic approaches. It has been shown that the maturation stage of T-ALL decides its dependency on Bcl-2/Bcl-xL. The immature early T cell progenitor ALL (ETP-ALL) rely on Bcl-2 for their survival while all the other stages of T-ALL and primary patient samples depend on Bcl-xL. Bcl-2 inhibitors have thus shown to display promising antitumor activity against ETP-ALL, a subgroup with a high risk of relapse, but with a variable response across these patients. Therefore, there is a need for predictive biomarkers and further investigation towards finding a combination of drugs for the treatment of these patients. Methodology & Aim: We screened 10 different T-ALL cell lines with a combination of Bcl-2 inhibitor and a panel of 378 protein kinase inhibitors and identified polo-like kinase inhibitor as a promising candidate. We thus aimed to study the combined effect of Bcl-2 and PLK1 inhibition in a panel of T-ALL cell lines and in a PDX model of chemo-resistant childhood T-ALL. We also investigated the underlying mechanism of drug synergy by various biochemical assays. Results: Cell viability of 14 T-ALL cell lines was determined after being subjected to Bcl-2 inhibitor (ABT-199) and PLK1 inhibitor (BI-6727). All cell lines responded well to BI6727 with an EC50 of less than 70nM. However, they showed differential response to ABT199 with only 3 cell lines being sensitive with an EC50 of less than 40nM. The mRNA levels of Bcl-2, Bcl-xL and PLK 1, 2, 3 and 4 were determined by qRT-PCR. PLK1 was found to be highly expressed in all the cell lines as compared to the rest of the 3 PLK family proteins. ABT-199-sensitive cell lines showed lower Bcl-xL mRNA levels irrespective of their Bcl-2 expression, and displayed synergy with BI-6727. A higher degree of apoptosis was also observed in the combination treatment as compared to a single drug. Immunoblot analysis revealed cleavage of PARP1 and lower levels of c-Myc and MCL1 expression in the presence of both ABT-199 and BI-6727. Conclusions: Upregulation of the anti-apoptotic BCL2 family members is one of the canonical ways for cancer cells to escape apoptosis. In the past years, several highly selective and potent BCL2 inhibitors have been developed and showed promising efficacy in various cancers. We found that the sensitivity of T-ALL cell lines to ABT-199 is largely determined by the lower levels of Bcl-xL expression. Furthermore, ABT-199 displays synergy with the PLK inhibitor. T-ALL cell lines predominantly express PLK1 and thus the combinatorial effect of ABT-199 and BI-6727 is mediated through the pharmacological inhibition of both BCL2 and PLK1. Currently, we are generating iRFP-expressing T-ALL cell lines which will be used to check drug efficacy in vivo. Furthermore, we have collected chemo-resistant PDX cell lines which will be used to verify the cell line data. Besides its role in cell cycle control, we still have very limited knowledge about the function of PLK1 in leukemia. Thus, studying its role in T-ALL cell lines by knocking down PLK1 with CRISPR/Cas9 technology will provide an important insight. Disclosures No relevant conflicts of interest to declare.

scholarly journals Distribution and Clinical Features of NOTCH1 Signaling Activating Alterations in Pediatric T-Cell Acute Lymphoblastic Leukemia (T-ALL)

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 4089-4089
Author(s):  
Shunsuke Kimura ◽  
Masafumi Seki ◽  
Kenichi Yoshida ◽  
Hiroo Ueno ◽  
Yasuhito Nannya ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Childhood Leukemia ◽  
Transmembrane Domain ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Luciferase Reporter ◽  
Internal Deletion ◽  
Notch1 Signaling ◽  
Cell Acute Lymphoblastic Leukemia

Abstract Introduction NOTCH1 and FBXW7 alterations leading to aberrant activation of NOTCH1 signaling, classified into two patterns; ligand-independent activation (LIA) and impaired degradation (ID) of NOTCH1. In general, activation of NOTCH1 axis is a hallmark of T-cell acute lymphoblastic leukemia (T-ALL), though comprehensive studies regarding subclonal mutations inducing NOTCH1 activation are still elusive. In the present study, we explored the clinicopathological relevance of NOTCH1/FBXW7 aberrations considering subclonal alterations. Methods A total of 176 cases with pediatric T-ALL were enrolled in this study. We reanalyzed our previous data of targeted-capture sequencing (n=176) for 158 ALL-related genes/regions and combined with previous expression profiling data based on whole transcriptome sequencing (WTS; n=121). We defined as a subclonal mutation when variant allele frequency was below 0.15 and/or multiple alterations were found within the same pattern of NOTCH1 activation (LIA or ID). All patients were received Berlin-Frankfurt-Münster based chemotherapies with non-minimal residual disease (MRD) based risk stratification, which were mainly offered from the Tokyo Children's Cancer Study Group (TCCSG) and the Japan Association of Childhood Leukemia Study (JACLS). Results In total, we detected aberrations activating NOTCH1 signaling in 81.3% (143/176) of cases including subclonal mutations. Subclonal alterations were observed in 26.7% (n=47). Single nucleotide variations in the heterodimerization domain (HD-SNV) were the most frequent (43.2%; n=76), followed by PEST domain mutations (33.0%; n=58), FBXW7 mutations (26.1%; n=46), non-frameshift indels of NOTCH1 (19.9%; n=35), and in-frame internal duplication known as juxta-membrane expansion (6.3%; n=11). Amplification of NOTCH1 region and 5' NOTCH1 deletion were not detected in our cohort. Both LIA and ID patterns were detected in 43.2% (n=76). Most mutations were mutually exclusive within each LIA and ID pattern. Intriguingly, we detected four (2.3%) internal deletion of NOTCH1 gene (DEL; missing exon 3-27 (DEL3) or 21-27 (DEL21)), three cases (1.7%) of SNV at 3' untranslated region, and two (1.1%) SEC16A-NOTCH1 fusions. These alterations were previously reported to activate NOTCH1 signaling in breast cancer or chronic lymphoblastic leukemia, except for DEL21. We confirmed that DEL21 strongly activates NOTCH1 signaling by luciferase reporter assay (over 100 times compared to wild type NOTCH1). As previously reported in DEL3 and CUTLL cell line, transcripts might initiate at methionine 1737 located within the NOTCH1 transmembrane domain and seem to be sensitive to γ-secretase inhibitors. Analysis of frequency of detected NOTCH1 activating alterations in each previously reported WTS-based cluster (ETP, SPI1, TLX, TAL1-RA, and TAL1-RB) revealed that alterations were frequently detected in TLX (100%; 24/24) and TAL1-RB (95.1%; 39/41), whereas less frequent in TAL1-RA (61.1%; 11/18). In TAL1-RA, all SEC16A-NOTCH1 fusions were observed despite significantly low rate of HD-SNV (11.1%; 2/18). In SPI1 cluster, PEST domain alterations were frequently detected (71.4%; 5/7). Importantly, cases harboring subclonal NOTCH1/FBXW7 alterations showed significantly worse outcome (log-rank P = 0.01), although there was no prognostic difference between cases with and without NOTCH1/FBXW7 mutations. Conclusions We observed NOTCH1 activating alterations in 81.3% of pediatric T-ALL cases and detected rare internal deletion of NOTCH1 gene and NOTCH1 fusions recurrently in T-ALL. Furthermore, the presence of subclonal NOTCH1/FBXW7 mutations might be relevant to unfavorable outcome. Despite several limitations such as non-MRD based treatment, our results might be useful for developing a new anti-NOTCH1 therapeutic strategy for pediatric T-ALL patients. Disclosures No relevant conflicts of interest to declare.

New LMO2 Translocations in T-Cell Acute Lymphoblastic Leukemia, Involving STAG2 at Xq25 and MBNL1 at 3q25: A Positive Change?.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2641-2641
Author(s):  
Suning Chen ◽  
Stefan Nagel ◽  
Bjoern Schneider ◽  
Maren Kaufmann ◽  
Ursula R. Kees ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Cell Line ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
B Cell Lymphoma ◽  
Small Sample ◽  
Upstream Region ◽  
Cell Acute Lymphoblastic Leukemia

Abstract Abstract 2641 Poster Board II-617 Background: In T-cell acute lymphoblastic leukemia (T-ALL) the LMO2 transcription factor locus is juxtaposed with T-cell receptor (TCR) genes by a recurrent chromosome translocation, t(11;14)(p13;q11). Recent molecular cytogenetic data indicate that unlike classical TCR rearrangements, t(11;14) operates synonymously with submicroscopic del(11)(p13p13) by removing a negative upstream LMO2 regulator (Dik et al., Blood 2007;110:388). The combined incidence of both LMO2 rearrangements is ∼10-15% (Van Vlierberghe and Huret, Atlas Genet Cytogenet Oncol Haematol, November 2007). However, aberrant LMO2 expression occurs in nearly half of all T-ALL cases, a discrepancy which may indicate a significant contribution by cryptic chromosome alterations. We attempted the extended characterization of the LMO2 genomic region in T-ALL cell lines to look for such rearrangements. Cells and Methods: We investigated a panel of 26 well characterized and authenticated T-ALL cell lines using parallel fluorescence in situ hybridization (FISH) with a tilepath BAC/fosmid contig and both conventional and quantitative reverse transcriptase (Rq)-PCR. Global gene expression was additionally measured in some cell lines by Affymetrix array profiling. Results: LMO2 rearrangements were detected in 5/26 (19.2%) cell lines including both established rearrangements, t(11;14) and del(11)(p13p13) in one cell line apiece (3.8%). Interestingly, we found two novel LMO2 translocations: t(X;11)(q25;p13) in 2/26 (7.7%), and t(3;11)(q25;p13) in 1/26 (3.8%) cell lines, respectively. Comparing transcription levels in cell lines with and without genomic rearrangements showed that LMO2 expression was significantly higher in T-ALL cell lines carrying LMO2 rearrangements (P<0.001). Rq-PCR revealed that 5 of the top 10 (50%) LMO2 expressing cell lines carry cytogenetic rearrangements at this locus, compared to 0/16 remaining examples. Loss of a recently defined LMO2 negative regulatory element was identified in the del(11)(p13p13) cell line but no other deletions were detected. Two genes STAG2 at Xq25 and MBNL1 at 3q25 were identified as novice LMO2 partners in t(X;11) and t(3;11), respectively. In both genes breakpoints lay at intron 1 close to deeply conserved noncoding regulatory regions. Both t(X;11) cell lines displayed conspicuous silencing of the ubiquitously expressed STAG2 gene highlighting the transcriptional significance of the region displaced. Unlike t(11;14)/del(11)(p13p13) both new rearrangements carry LMO2 breakpoints in the far upstream region (at minus 80–150 Kbp), and appear to result in upregulation of LMO2 by juxtaposition rather than via covert deletion. STAG2 is a component of the chromosomal cohesin complex which acts as a transcriptional coactivator, and which has been recently identified as a potential driver of oncogene transcription in acute myeloid leukemia (Walter et al., Proc Natl Acad Sci U S A. 2009;106:1295). MBNL1 controls RNA splicing and is a rare BCL6 partner gene in B-cell lymphoma, but this is the first report of its involvement in T-ALL. Conclusion: Given their frequency and variety in a small sample, we propose that cryptic chromosome rearrangements targeting LMO2 upregulation may be significantly more frequent than hitherto appreciated in T-ALL. Unlike canonical LMO2 rearrangements, both t(X;11) and t(3;11) would appear to function positively by upregulation of LMO2 via juxtaposition with noncoding driver elements within these novel partner genes. Perspectives: Future work will address the regulatory potential of candidate enhancer sequences embedded within conserved noncoding intronic sequences of MBNL1 and STAG2. Cytogenetically inconspicuous cell lines displaying LMO2 upregulation will be subjected to more detailed scrutiny using high density genomic SNP arrays. Disclosures: No relevant conflicts of interest to declare.

Identification of JAK1 Mutation In 40 Cases of Adult Acute T Lymphoblastic Leukemia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4652-4652
Author(s):  
Aining Sun ◽  
Wenjuan Wang ◽  
Guanghua Chen ◽  
Wu Depei ◽  
Suning Chen ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Lymphoblastic Leukemia ◽  
T Cell ◽  
Mononuclear Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Amino Acid Sequences ◽  
Insertion Mutation ◽  
Newly Diagnosed ◽  
Cell Acute Lymphoblastic Leukemia

Abstract Abstract 4652 Objective This study was purposed to analyze the mutations of JAK1 in bone marrow cells from adult patients with newly-diagnosed T cell acute lymphoblastic leukemia (T-ALL). Methods The entire coding sequence of JAK1 in bone marrow mononuclear cells (MNCs) from 40 adult T cell ALL patients were screened by polymerase chain reaction (PCR) and direct sequencing, then the clinical features of JAK1 mutation positive patients were analyzed. Results JAK1 mutations were identified in 5%(2/40) patients, one is point mutation, the other is insertion mutation, resulting in changes in amino acid sequences, and the two types of mutations are different from those mutations found before. Conclusion The JAK1 mutations were found in about 5% newly-diagnosed T cell acute lymphoblastic leukemia, which was lower than those report abroad. Disclosures: No relevant conflicts of interest to declare.

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