The spectrum of activating EGFR mutations from cell-free DNA (cfDNA) in large pancreatic cancer cohort.

2019 ◽  
Vol 37 (4_suppl) ◽  
pp. 237-237
Author(s):  
Kristin Sedgwick Price ◽  
Lesli Ann Kiedrowski ◽  
Fernando I. De Zarraga ◽  
Mike Cusnir ◽  
Richard B. Lanman ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Median Number ◽  
Kinase Domain ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Rapid Progression ◽  
Activating Mutations ◽  
Domain 3 ◽  
Exon 20 ◽  
Egfr Tkis

237 Background: Metastatic pancreatic cancer (mPC) is one of the deadliest cancers with a < 10% 5-year survival rate. Poor prognosis is well established with lack of response to or rapid progression on existing chemotherapy options. Targeted therapies, like EGFR-TKIs, have been shown to increase survival in other solid tumors like NSCLC with certain oncogenic drivers. Although treatment with the EGFR-TKI erlotinib, in combination with gemcitabine, is available for patients (pts) with mPC, the survival benefit is small in unselected patients. A better understanding of the spectrum of EGFR mutations in mPC may lead to improved therapy selection. Methods: We retrospectively reviewed genomic results from 2,938 consecutive mPC pt samples sent for ctDNA NGS analysis between 7/2014 - 9/2018 (Guardant Health, Inc.). All reported EGFR mutations were reviewed and activating mutations were determined based on literature review. Results: 19 EGFR activating mutations were identified in 16 unique pts (0.66% of total mPC pts with alterations detected). 3 mutations were identified in the extracellular domain and 16 mutations in the tyrosine kinase domain (3 in exon 18, 3 in exon 19, 6 in exon 20, 4 in exon 21). Alterations in exon 20 included 5 T790M mutations; two of these were reported at allelic frequencies suggestive of germline origin. Analysis of co-mutations revealed 7 pts with EGFR mutations that appeared subclonal relative to other potential drivers (4 KRAS, 2 ERBB2, 1 GNAS). The median number of alterations per sample was 4 (range 2-170) with the latter pt exhibiting a hypermutator phenotype. Multiple pts had more than one activating EGFR alteration including one who was found to have 4 EGFR sequence alterations (S768I, L861Q, T790M, p.Val769_Asp770insMet) plus EGFR amplification (plasma copy number 66.8). We will collect and report clinical details to characterize the treatment context for these pts. Conclusions: Activating EGFR mutations in mPC are rare but may present an opportunity for targeted therapy in this population. Further exploration is warranted to better understand the oncogenic activity of less common, subclonal, or co-occurring EGFR mutations and their sensitivity to EGFR-TKIs in mPC.

Sensitivity to EGFR inhibitors based on location of EGFR exon 20 insertion mutations within the tyrosine kinase domain of EGFR.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 7523-7523 ◽  
Author(s):  
Daniel Botelho Costa ◽  
Hiroyuki Yasuda ◽  
Natasha J Sng ◽  
Wee-Lee Yeo ◽  
Lorena Lobo de Figueiredo-Pontes ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Cell Line ◽  
Molecular Mechanisms ◽  
Site Directed Mutagenesis ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Exon 20 ◽  
Insertion Mutations ◽  
Egfr Tkis

7523 Background: Epidermal growth factor receptor (EGFR) mutations (M) define an important subgroup of non-small-cell lung cancer (NSCLC). Most patients whose tumors harbor exon 19 deletions or L858R EGFR M have responses to reversible ATP-mimetic EGFR tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib. Exon 20 insertion M comprise ~5% of EGFR M, occur at the N-lobe of EGFR after its C-helix (AA M766), and nearly all NSCLCs with EGFR exon 20 insertion M display lack of responses to EGFR TKIs (Yasuda H. Lancet Oncol 2011). Methods: We have 1) compiled genotype-clinical outcomes of EGFR exon 20 insertion M NSCLCs to EGFR TKIs, 2) generated a comprehensive panel of exon 20 EGFR M constructs using site-directed mutagenesis and introduced them into Ba/F3 cells for in vitro analysis, and 3) compared NSCLC cell lines with EGFR M to a novel malignant pleural effusion-derived cell line. Results: The disease control rate of gefitinib or erlotinib was significantly higher in EGFR exon 20 insertion M located within the C-helix (3/3,100%) when compared to M following the C-helix (1/14, 7%; p=0.00059). The NSCLC with EGFR-A763_Y764insFQEA (located within the C-helix of EGFR) achieved a partial response to erlotinib that lasted 18 months. Most other exon 20 insertion M-positive NSCLCs did not respond (p=0.07). Eight representative exon 20 insertion M were studied (including EGFR-A763_Y764insFQEA, Y764_S765insHH, A767_V769dupASV, D770_N771insNPG, H773_V774insH). All, but A763_Y764insFQEA, were resistant to micromolar concentrations (C) of EGFR TKIs. Ba/F3 cells with EGFR-A763_Y764insFQEA underwent apoptosis upon exposure to nanomolar C of erlotinib. A patient-derived cell line with EGFR-A763_Y764insFQEA had phosphorylated EGFR, ERK and AKT inhibited by nanomolar C of erlotinib. Conclusions: Not all EGFR exon 20 insertion mutations are resistant to EGFR TKIs, and in specific EGFR-A763_Y764insFQEA is an EGFR TKI-sensitive M. This finding has clinical implications for the care of the 10,000 cases of EGFR exon 20 insertion M NSCLC diagnosed yearly and points towards the need to define the molecular mechanisms that underlie differential responses to EGFR TKIs.

Expanding the search for significant EGFR mutations in NSCLC outside of the tyrosine kinase domain with next-generation sequencing

2017 ◽  
Vol 34 (7) ◽  
Author(s):  
Matthew K. Stein ◽  
Lindsay Morris ◽  
Jennifer L. Sullivan ◽  
Moon Fenton ◽  
Ari VanderWalde ◽  
...  
Keyword(s):  
Next Generation Sequencing ◽  
Tyrosine Kinase ◽  
Kinase Domain ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Next Generation ◽  
Generation Sequencing

SRC Is a Critical Signaling Mediator in FLT3-ITD Positive AML.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 477-477
Author(s):  
Hannes Leischner ◽  
Rebekka Grundler ◽  
Corinna Albers ◽  
Anna Lena Illert ◽  
Karsten Spiekermann ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Point Mutations ◽  
Kinase Domain ◽  
Sh2 Domain ◽  
Control Group ◽  
Tyrosine Kinase Domain ◽  
Myeloproliferative Disease ◽  
Activating Mutations ◽  
Tandem Duplications

Abstract Abstract 477 Activating mutations of FLT3 are frequent in patients with AML. Two types of mutations are most common: Internal tandem duplications (ITD) of the juxtamembrane domain in approximately 30% of patients and point mutations within the second tyrosine kinase domain (TKD) in about 7% of AML patients. Patients carrying the FLT3-ITD mutation have a significantly worse prognosis whereas FLT3-TKD mutations do not appear to influence the clinical outcome. Studies have shown that mice receiving a transplant of bone marrow expressing FLT3 ITD develop a myeloproliferative disease. In contrast, mice which were transplanted with FLT3 TKD infected bone marrow, suffer from a lymphoid disease. Thus, both FLT3 mutations seem to exert different biological functions. Interestingly, FLT3-ITD but not FLT3-TKD or FLT3-WT leads to a strong activation of the STAT5 signaling pathway. Therefore, STAT5 activation may be responsible for the observed differences in biology. Here we investigated the signalling pathways leading to STAT5 activation downstream of FLT3-ITD. FLT3-ITD does not bind STAT5 directly nor does it activate the classical JAK2 pathway. Instead FLT3-ITD utilizes c-Src to activate STAT5. Co-immunoprecipitations and GST pull downs revealed a strong and exclusive interaction between Src and FLT3 ITD, which is mediated by the Src-SH2 domain. This interaction is absent in FLT3-TKD or FLT3-WT after ligand stimulation. The sequence duplication in FLT3-ITD leads to additional potential Src-SH2 binding sites. We identified tyrosines 589 and 591 of FLT3-ITD to be essential for Src binding and subsequent STAT5 activation. Specific Src inhibitors or Src-siRNA blocked STAT5 activation and growth induced by FLT3-ITD but not FLT3-TKD. FLT3-ITD positive cells with a stable Src knockdown injected into syngenic mice led to a leukemic disease with a significant delayed onset and prolonged survival in comparison to the control group. Finally, a combination of FLT3 and Src inhibitors was tested. This combination was highly efficient in FLT3-ITD positive cells but not in FLT-TKD positive cells. Together these findings show that Src plays an important role in the signalling of FLT3-ITD but not FLT3-TKD. Thus, Src might be an interesting therapeutic target for FLT3-ITD positive AML. Disclosures: No relevant conflicts of interest to declare.

Combination of c-SRC and FLT3 Inhibitors Has An Additive Inhibitory Effect on FLT3 ITD but Not on FLT3 TKD Positive Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2892-2892 ◽  
Author(s):  
Hannes Leischner ◽  
Rebekka Grundler ◽  
Corinna Albers ◽  
Anna Lena Illert ◽  
Katharina Götze ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Growth Inhibition ◽  
Conflicts Of Interest ◽  
Point Mutations ◽  
Inhibitory Effect ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Myeloproliferative Disease ◽  
Activating Mutations ◽  
Flt3 Inhibitors

Abstract Abstract 2892 Activating mutations of FLT3 are frequent in patients with AML. Two types of mutations are most common: Internal tandem duplications (ITD) of the juxtamembrane domain in approximately 30% of patients and point mutations within the second tyrosine kinase domain (TKD) in about 7% of AML patients. Patients carrying the FLT3-ITD mutation have a significantly worse prognosis whereas FLT3-TKD mutations do not appear to influence the clinical outcome. Studies have shown that mice receiving a transplant of bone marrow expressing FLT3 ITD develop a myeloproliferative disease. In contrast, mice which were transplanted with FLT3 TKD infected bone marrow, suffer from a lymphoid disease. Thus, both FLT3 mutations seem to exert different biological functions. Interestingly, FLT3-ITD but not FLT3-TKD or FLT3-WT leads to a strong activation of the STAT5 signaling pathway. Recently we have shown that c-SRC is the crucial signaling mediator of FLT3 ITD to activate STAT5. Based on these findings we investigated the effect of FLT3 inhibitors (Midostaurin, Sorafenib and Sunitinib) in combination with c-SRC inhibitors (Dasatinib and PD166-326) on FLT3 ITD and FLT3 TKD murine and human cell lines as well as on primary patient material. In FLT3 ITD expressing murine myeloid 32D cells c-SRC inhibitors in combination with FLT3 inhibitors showed clear additive effects on growth inhibition, apoptosis and activation of STAT5. In contrast, c-SRC inhibitors had no additional effects in FLT3 TKD expressing cells. Accordingly, a strong additive effect of c-SRC and FLT3 inhibitors could also be demonstrated in the FLT3 ITD positive human AML cell line MV4-11. Finally FLT3 ITD and FLT3 TKD positive primary human AML cells were investigated. We were able to detect a significant additional growth inhibition of FLT3 ITD positive human cells by combining c-SRC and FLT3 inhibitors. In contrast, no further growth inhibition was observed by c-SRC inhibition in primary AML cells expressing the FLT3 TKD mutation. Together our results confirm c-SRC as a crucial signaling mediator in FLT3-ITD but not FLT3-TKD positive AML. The combination of FLT3 and c-SRC inhibitors warrants further investigation in FLT3 ITD positive AML. Disclosures: No relevant conflicts of interest to declare.

A retrospective analysis of the prevalence of EGFR or KRAS mutations in patients (pts) with crizotinib-naïve and crizotinib-resistant, ALK-positive non-small cell lung cancer (NSCLC).

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 8083-8083
Author(s):  
Justin F. Gainor ◽  
Anna M. Varghese ◽  
Sai-Hong Ignatius Ou ◽  
Sheheryar Kabraji ◽  
Mark M Awad ◽  
...  
Keyword(s):  
Direct Sequencing ◽  
Acquired Resistance ◽  
Kinase Domain ◽  
Repeat Biopsy ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Kras Mutations ◽  
Anaplastic Lymphoma ◽  
Biopsy Specimens ◽  
Alk Positive

8083 Background: Anaplastic lymphoma kinase (ALK) gene rearrangements define a distinct molecular subset of NSCLC. Recently, several studies have reported that ALK+ pts occasionally harbor concomitant mutations in other oncogenic drivers. Methods: We retrospectively analyzed tumor genotyping data from 1,683 pts with NSCLC seen at 3 U.S. centers from 2009 – 2012 to determine rates of overlapping alterations in EGFR, KRAS and ALK. Mutations in EGFR and KRAS were mainly identified using the SNaPshot multiplexed assay (>95% of cases). ALK FISH was performed in all cases. To determine if this prevalence is impacted by crizotinib, we also updated our earlier analysis (Katayama et al., Sci Transl Med, 2012) of a series of repeat biopsy specimens from 34 crizotinib-resistant, ALK+ pts. Resistant specimens were examined using ALK FISH, SNaPshot, and direct sequencing of the ALK tyrosine kinase domain (TKD). Results: Screening identified 301 (17.8%) EGFR mutations, 465 (27.6%) KRAS mutations, and 75 (4.4%) ALK rearrangements. EGFR mutations and ALK rearrangements were mutually exclusive. 4 pts with KRAS mutations also had abnormal ALK FISH patterns, involving isolated 5’ green probes (3/4 cases) and an isolated 3’ red probe that was unusually small (1/4 cases). Sufficient tissue was available for confirmatory ALK immunohistochemistry (clone 5A4, Novacastra, UK) in 3 of these cases, all of which were negative for ALK expression. Among pts with ALK+ NSCLC and acquired crizotinib resistance, repeat biopsy specimens remained ALK fusion positive in 28/28 (100%) cases. Secondary mutations in the ALK TKD (1151Tins, L1196M, G1202R, S1206Y, and G1269A) were identified in 7/34 (20.6%) cases. L1196M was the most common secondary mutation (3/34, 8.8% cases). ALK gene amplification was present in 3/28 (10.71%) pts. No EGFR or KRAS mutations were identified in 23 crizotinib-resistant, ALK+ pts with sufficient tissue for testing. Conclusions: Functional ALK rearrangements were mutually exclusive with EGFR and KRAS mutations in a large Western patient population. This lack of overlap was also observed in ALK+ pts with acquired resistance to crizotinib.

Expanding the search for significant EGFR mutations in NSCLC outside of the tyrosine kinase domain (TKD) with next-generation sequencing (NGS).

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. e20506-e20506
Author(s):  
Matthew K Stein ◽  
Lindsay Kaye Morris ◽  
Jennifer Sullivan ◽  
Moon Jung Fenton ◽  
Ari M. Vanderwalde ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
In Silico ◽  
Kinase Inhibitors ◽  
Stage Iv ◽  
In Silico Analysis ◽  
Large Cell ◽  
Kinase Domain ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Carboxy Terminal

e20506 Background: While conventional organization of EGFR mutations in NSCLC includes classic lesions sensitive to tyrosine kinase inhibitors (TKI) and variants localized to TKD in exons 18-21, NGS raises the prospect of identifying clinically relevant variants in extra-TKD regulatory regions. Methods: Patients (pts) with lung cancer who received tumor profiling with NGS from 2013-2015 via Caris were identified. EGFR mutations were arranged based upon their known distribution relative to the TKD. In silico analysis was performed with PolyPhen-2 (Harvard) to predict nsSNPs’ pathogenicity. Results: 259 pts (248 NSCLC, 11 SC) had median age 65 years (26-85); 50% female; 64% white, 34% black; 73% with ≥20 pack-years (py), 12% non-smokers; 53% of samples were metastases. 65% NSCLC were adenocarcinoma (A), 21% squamous (S), 8% large-cell; 87% stage IV, 12% III. 44 EGFR variants were seen in 40 pts (15%; 39 NSCLC, 1 SC). While 32 pts had TKD lesions demonstrable through standard testing, 8 had extra-TKD mutations (8/44), of which 5 were extracellular domain (ECD), 1 juxtamembrane (JM) and 2 carboxy terminal (CT). Aside from pathogenic ECD mutation G598V, 5/7 extra-TKD nsSNPs were predicted-damaging (pnsSNP) with in silico (Table 1). 7/7 extra-TKD nsSNP+ pts smoked (6/7 ≥20 py) and all 6 NSCLC pts were stage IV; 50% A, 17% S; 83% male. The pt with JM R675Q had erlotinib, 150 mg daily, added following progression of stage IV NSCLC on carboplatin and paclitaxel and had a partial response for 4 months. No other pt received EGFR-directed therapy. Conclusions: 2% NSCLC cases in our cohort had EGFR pnsSNPs located outside of the TKD, representing >18% of all EGFR mutations. Extra-TKD variants should be characterized collaboratively to determine TKI sensitivity and additional therapeutic targets. [Table: see text]

Characteristics of EGFR uncommon mutations in Chinese cancer patients.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. e13527-e13527
Author(s):  
Minghui Wang ◽  
Shuben Li ◽  
Hongbiao Wang ◽  
Jianjiang Xie ◽  
Junhang Zhang ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Transmembrane Domain ◽  
Kinase Domain ◽  
Copy Number Variations ◽  
Chinese Patients ◽  
Next Generation Sequencing Data ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Lung Cancers ◽  
Exon 19

e13527 Background: Exon 19 deletions and exon 21 L858R substitutions are the most common mutations of epidermal growth factor receptor (EGFR) in cancers, and the remaining other mutations are called uncommon mutations. Recent studies have shown the clinical relevance of EGFR uncommon mutations with tyrosine kinase inhibitors (TKI) therapies and immunotherapies. Therefore, understanding the distribution and characteristics of EGFR uncommon mutations in cancers would provide evidence for future design of trials and drug development. Methods: Next-generation sequencing data were obtained from 3,026 Chinese tumor samples which have been identified with EGFR mutations. Single nucleotide variations (SNV), short and long insertions/deletions (indel), copy number variations and gene rearrangements were assessed. All tests were carried out in a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory in Shanghai, China. Results: EGFR mutations including 32% L858R substitutions, 28% exon 19 deletions, and 40% uncommon mutations were detected in this cohort. EGFR uncommon mutations were most frequently detected in lung cancers, followed by esophageal and gastric cancers. The uncommon mutations of EGFR including 54% SNVs, 30% amplifications, and 9% rare types of mutations such as rearrangement, long indels and complex mutations were detected. The SNVs in exon 18 to 21 which encode the tyrosine kinase domain of EGFR consisted of 16% EGFR mutations. Among them, the mostly frequently SNV was G719X in exon 18 and had 3% EGFR mutations. Mutations in other function domain of EGFR, including extracellular EGF binding domain (0.8%), transmembrane domain (0.03%) and intracellular autophosphorylation domain (0.7%) were also detected. Conclusions: Our data indicated that EGFR uncommon mutations were widely distributed in a variety of cancer types in Chinese patients, mostly in lung cancers. SNVs in the tyrosine kinase domain were the most frequent uncommon mutations. These data will provide clues for future clinical studies.

Osimertinib in non-small cell lung cancer (NSCLC) with atypical EGFR activating mutations: A retrospective multicenter study.

2020 ◽  
Vol 38 (15_suppl) ◽  
pp. 9570-9570 ◽  
Author(s):  
Jingran Ji ◽  
Jacqueline V Aredo ◽  
Andrew Piper-Vallillo ◽  
Laura Huppert ◽  
Julia K Rotow ◽  
...  
Keyword(s):  
Retrospective Analysis ◽  
Median Time ◽  
Clinical Benefit ◽  
Kinase Inhibitor ◽  
Resistance Mutation ◽  
Egfr Mutations ◽  
Activating Mutations ◽  
Metastatic Nsclc ◽  
Exon 20 ◽  
Exon 19

9570 Background: Osimertinib (osi) is a 3rd generation EGFR tyrosine kinase inhibitor (TKI) approved for first line (1L) treatment of metastatic NSCLC harboring EGFR Exon 19 del and L858R (representing > 80% of EGFR activating mutations) or in NSCLC with EGFRT790M (the most common resistance mutation to 1st or 2nd generation TKI). However, it has not been well-studied in EGFR-mutant NSCLC harboring less common EGFR activating mutations such as G719X, L861Q, S768I, and exon 20 insertion (ins), among others. Methods: We conducted a multi-institution, retrospective study approved on institutional IRB protocols in a series of patients (pts.) with metastatic NSCLC treated with osi who harbored at least one atypical EGFR mutation, excluding those with concurrent L858R, Exon 19 del, or T790M. Kaplan-Meier analyses were generated with SPSS, v25 (IBM Corp., USA). Response was assessed by RECIST 1.1 in evaluable pts. Time on osi was employed as a surrogate endpoint for clinical benefit in this retrospective analysis. Results: Fifty-one NSCLC pts with uncommon EGFR mutations were identified among six US institutions. Pt characteristics: 72.5% women, median age 65 yo (44-83 yo), 82.3% ECOG PS 0-1, 43.1% never smoker, 100% lung adenocarcinoma, 58.8% Caucasian, 25.5% Asian, 3.9% Black, 2.0% Hispanic, and 9.8% Other. The most frequent mutations were L861Q (35.3%, N = 18), G719X (27.5%, N = 14), and Exon 20 ins (15.7%, N = 8). Osi was used in the 1L setting in 39.2% (N = 20). Median time on osi was 7.1 months (mo.) in the overall cohort (95% CI, 5.4 to 8.8 mo.) and 8.9 mo. (95% CI, 7.0 to 10.8 mo.) in pts receiving 1L osi. Patients harboring G719X (N = 4) and L861Q (N = 10) mutations had a median time on 1L osimertinib of 5.8 mo. and 19.3 mo., respectively. One patient’s tumor had an EGFR exon 19 ins and was on 1L osi with a partial response for 16.8 months. Two patients with Exon 20 ins were on 1L osi for 9.3 mo. and 8 mo., respectively. Conclusions: In this largest known clinically annotated dataset of patients with atypical EGFR-mutations treated with osi, activity was noted, though 1L clinical benefit on osi appears lower in this multicenter US cohort than in E19del or L858R. These results are comparable to the recently published prospective phase II trial ( Cho et al, 2019) conducted in Korea. Patients with L861Q and Exon 19 insertion appeared to benefit the most from osi in this time on treatment retrospective analysis. More detailed analysis of this cohort is planned and further prospective studies are warranted to determine clinical benefit of osi amongst diverse atypical EGFR-mutations.

Activating FLT3 Mutations in CD4+/CD8− Pediatric T-Cell Acute Lymphoblastic Leukemias.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1465-1465
Author(s):  
Pieter Van Vlierberghe ◽  
Jules P.P. Meijerink ◽  
Ronald W. Stam ◽  
Wendy van der Smissen ◽  
Elisabeth R. van Wering ◽  
...  
Keyword(s):  
T Cell ◽  
Tyrosine Kinase ◽  
Point Mutations ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Activating Mutations ◽  
Activated State ◽  
Flt3 Mutations ◽  
Genetic Aberration ◽  
High Level

Abstract Activating mutations in the FMS-like tyrosine kinase 3 gene (FLT3) are the most common genetic aberration in acute myeloid leukemia (AML). Internal tandem duplications (ITD) in the juxtamembrane (JM) domain, or point mutations (PM) in the activation loop of the tyrosine kinase domain lead to a constitutive activated state of the FLT3 tyrosine kinase. Recently, FLT3 mutations were identified in a cohort of 69 adult T-ALL patients, showing that this genetic abnormality is not only restricted to myeloid leukemias. To validate the incidence of FLT3 mutations in pediatric T-ALL and investigate its relation to outcome and other clinical and immunophenotypical parameters, we screened 72 diagnostic pediatric T-ALL samples. FLT3/ITD mutations were identified in 2/72 pediatric T-ALLs (2.7%), whereas 0/72 showed point mutations in the kinase domain. Immunophenotypic analysis revealed a similar profile for both FLT3 mutated patient samples, i.e. TdT+, CD2+, CD5+, CD7+, CD4+/CD8−, cytoplasmic CD3+, surface CD3− and CD10−. Although representing early T-cell differentiation stages for both patient samples, these cases seem to have a more advanced immunophenotype compared to the FLT3 mutated adult T-ALL cases, previously described (CD34+, CD4−/CD8−). Both FLT3 mutated patients showed high level LYL1 and LMO2 expression. In addition, both pediatric samples contained a HOX11L2 translocation, which was not present in the FLT3 mutated adult T-ALL cases. The first FLT3 mutated patient suffered a relapse 13 months after initial diagnosis, whereas the other is still in continued complete remission for 61+ months. Interestingly, the relapse material showed no FLT3/ITD mutation, indicating that the FLT3 mutated T-ALL subclone seems to be effectively eradicated by current chemotherapy. These data suggest that the application of FLT3 inhibitors for FLT3-mutated T-ALLs, as recently suggested in literature, may not further improve treatment outcome in pediatric T-ALL.

AML-associated Flt3 kinase domain mutations show signal transduction differences compared with Flt3 ITD mutations

Blood ◽  
2005 ◽  
Vol 106 (1) ◽  
pp. 265-273 ◽  
Author(s):  
Chunaram Choudhary ◽  
Joachim Schwäble ◽  
Christian Brandts ◽  
Lara Tickenbrock ◽  
Bülent Sargin ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Target Genes ◽  
Kinase Inhibitor ◽  
Point Mutations ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Activating Mutations ◽  
Myeloid Progenitor ◽  
Myeloid Progenitor Cells ◽  
Kinase Domain Mutations

Activating mutations of Flt3 are found in approximately one third of patients with acute myeloid leukemia (AML) and are an attractive drug target. Two classes of Flt3 mutations occur: internal tandem duplications (ITDs) in the juxtamembrane and point mutations in the tyrosine kinase domain (TKD). We and others have shown that Flt3-ITD induced aberrant signaling including strong activation of signal transducer and activator of transcription 5 (STAT5) and repression of CCAAT/estradiol-binding protein α (c/EBPα) and Pu.1. Here, we compared the signaling properties of Flt3-ITD versus Flt3-TKD in myeloid progenitor cells. We demonstrate that Flt3-TKD mutations induced autonomous growth of 32D cells in suspension cultures. However, in contrast to Flt3-ITD and similar to wild-type Flt3 (Flt3-WT), Flt3-TKD cannot support colony formation in semisolid media. Also, in contrast to Flt3-ITD, neither Flt3-WT nor Flt3-TKD induced activation or induction of STAT5 target genes. Flt3-TKD also failed to repress c/EBPα and Pu.1. No significant differences were observed in receptor autophosphorylation and the phosphorylation of Erk-1 and -2, Akt, and Shc. Importantly, TKD but not ITD mutations were a log power more sensitive toward the tyrosine kinase inhibitor protein kinase C 412 (PKC412) than Flt3-WT. In conclusion, Flt3-ITD and Flt3-TKD mutations display differences in their signaling properties that could have important implications for their transforming capacity and for the design of mutation-specific therapeutic approaches.

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