Prospective study of 174 de novo acute myelogenous leukemias according to the WHO classification: subtypes, cytogenetic features and FLT3 mutations

Atypical chronic myeloid leukemia with isochromosome (X)(p10): A case report

Atypical chronic myeloid leukemia (aCML) is a rare subtype of myelodysplastic/myeloproliferative neoplasm (MDS/MPN). Although recurrent chromosomal and genetic abnormalities are frequently observed in aCML, none are specific to this type of leukemia. The present study reported a case of aCML associated with i(X)(p10), a rare recurrent chromosomal abnormality of hematological malignancy. A 40-year-old female was referred to the Tokyo Medical and Dental University Hospital (Tokyo, Japan) due to slight leukocytosis and anemia. A bone marrow aspiration revealed 4% blasts and granulocytic hyperplasia with dysplasia. A G-banded cytogenetic analysis of the bone marrow cells revealed 46, X, isochromosome X(iX)(p10) in all metaphases. The percentage of the neutrophil precursors promyelocytes, myelocytes and metamyelocytes in the peripheral blood was >10% throughout the clinical course of the patient, which resulted in a diagnosis of atypical chronic myeloid leukemia. Treatment with hydroxycarbamide was not able to effectively alleviate leukocytosis, and the disease progressed with the appearance of an additional cytogenetic abnormality, t(10;17)(p13;q21). Subsequently, the patient underwent allogeneic stem cell transplantation from a sibling donor, and subsequent cytogenetic analysis revealed a normal karyotype with full donor chimerism. The isodicentric X(idicX)(q13) mutation is a similar abnormality to i(X)(p10) and may result in a loss of the X-inactive specific transcript gene located at Xq13.2, the deletion of which has been previously reported to result in the development of MDS/MPN in mice. In addition, i(X)(p10) was identified as the sole chromosomal abnormality at the diagnosis of aCML in the case of the present study, which is similar to patients from previous studies of other hematological malignancies and supports the hypothesis that i(X)(p10) may have served a primary role in the leukemogenesis of aCML.

FMS-Like Tyrosine Kinase 3 (FLT3) and Nucleophosmin 1 (NPM1) in Iranian Adult Acute Myeloid Leukemia Patients with Normal Karyotypes: Mutation Status and Clinical and Laboratory Characteristics

Objective:

In this study, we evaluated the frequency of FMS-like tyrosine kinase 3 (FLT3-ITD and FLT3-TKD) and nucleophosmin (NPM1) mutations in Iranian patients with cytogenetically normal acute myeloid leukemia (CN-AML). The clinical and laboratory characteristics were compared between wild-type and mutant cases.

Materials and Methods:

Seventy newly diagnosed de novo AML patients were recruited at the time of diagnosis prior to chemotherapy; among them, 54 had CN-AML. For detecting mutations, the FLT3 and NPM1 genes were amplified by the polymerase chain reaction method, followed by direct sequencing.

Results:

Our results showed that the frequencies of FLT3-ITD, FLT3-TKD, and NPM1 mutations in CN-AML patients were 25.9%, 5.9%, and 20.8%, respectively. The most frequent NPM1 mutation type was the type A mutation. The FLT3-ITD mutation was seen more frequently in non-M3 patients compared with M3 patients. No mutation was observed in either the FLT3-TKD or the NPM1 gene in patients in the M3 French-American-British group. There was no significant association between the presence of FLT3-ITD and NPM1 mutations in CN-AML patients (p>0.05). The frequency of FLT3-ITD, FLT3-TKD, and NPM1 mutation was higher in CN-AML patients in comparison with AML patients with cytogenetic aberrations, although the differences were not statistically significant (p>0.05). There were no significant differences in mean white blood cell and platelet counts, serum hemoglobin levels, and bone marrow blast percentages between patients with wild-type and mutant FLT3-ITD and NPM1 genes (p>0.05). No difference was observed in the frequency of FLT3-ITD or NPM1 mutation regarding age or sex (p>0.05).

Conclusion:

Given the high stability of NPM1 during the disease course, it can be used in combination with FLT3 as well as other known genetic markers to monitor patients, especially for minimal residual disease detection.

A Genome-wide hybrid incompatibility landscape between Caenorhabditis briggsae and C. nigoni

Systematic characterization of ẖybrid incompatibility (HI) between related species remains the key to understanding speciation. The genetic basis of HI has been intensively studied in Drosophila species, but remains largely unknown in other species, including nematodes, which is mainly due to the lack of a sister species with which C. elegans can mate and produce viable progeny. The recent discovery of a C. briggsae sister species, C. nigoni, has opened up the possibility of dissecting the genetic basis of HI in nematode species. However, the paucity of dominant and visible marker prevents the efficient mapping of HI loci between the two species. To elucidate the genetic basis of speciation in nematode species, we first generated 96 chromosomally integrated GFP markers in the C. briggsae genome and mapped them into the defined locations by PCR and Next-Generation Sequencing (NGS). Aided by the marker, we backcrossed the GFP-associated C. briggsae genomic fragments into C. nigoni for at least 15 generations and produced 111 independent introgressions. The introgression fragments cover most of the C. briggsae genome. We finally dissected the patterns of HI by scoring the embryonic lethality, larval arrest, sex ratio and male sterility for each introgression line, through which we identified pervasive HI loci and produced a genome-wide landscape of HI between the two nematode species, the first of its type for any non-Drosophila species. The HI data not only provided insights into the genetic basis of speciation, but also established a framework for the possible cloning of HI loci between the two nematode species. Furthermore, the data on hybrids confirmed Haldane’s rule and suggested the presence of a large X effect in terms of fertility between the two species. Importantly, this work opens a new avenue for studying speciation genetics between nematode species and allows parallel comparison of the HI with that in Drosophila and other species.

Hybrid incompatibility (HI) has been intensively studied among Drosophila species, but remains largely unknown in other species. Model organism is a species of choice for the HI study because these species provide sophisticated molecular and genetic tools for illustrating mechanism underlying a given HI. C. elegans as a model organism contributed little to the field due to the lack of a sister species with which it can mate and produce viable progeny. The recent discovery of a C. briggsae sister species, C. nigoni, has made it possible to study the HI between nematode species. However, the paucity of molecular and genetic tools in both species inhibits their use in such studies. To empower the use of this species pair in HI studies, we first created a collection of fluorescent markers over the C. briggsae genome to facilitate the directional introduction of the marker-associated C. briggsae genomic fragments into the C. nigoni background. We next mapped the marker insertion sites and introduced the markers into C. nigoni by repeated crossings. Finally, we generated a genome-wide HI landscape between the two species by scoring the HI phenotypes of their hybrid progeny. The study not only provides an invaluable resource for the molecular cloning of HI loci between C. briggsae and C. nigoni, but also permits comparative analysis of speciation genetics between nematode and other species.

Isolated trisomy 2 in bone marrows of patients with suspected hematopoietic malignancies

Isolated trisomy 2 in hematopoietic malignancies is rare, having been reported in only eight cases. Of these cases, the majority are older males. The underlying hematologic malignancies range from myelodysplastic syndrome (MDS) to acute myeloid leukemia (AML). The molecular pathogenesis and prognostic significance of isolated trisomy 2 remains unknown. Herein, we report 11 cases of isolated trisomy 2 in hematologic disorders seen in the Mayo Clinic Cytogenetics laboratory from 1996-2012. The majority were older males between the ages of 63-93 years. The underlying bone marrow pathologic diagnoses ranged from no diagnostic features of malignancy to AML. Our data suggest that isolated trisomy 2 could represent an age-related phenomenon since all 11 cases were age 63 and over. It appears that isolated trisomy 2 harbors little prognostic significance and that, instead, the prognostic significance is driven by the underlying pathologic diagnosis. For example, whereas 3 of the cases with AML survived only 7-10 weeks post-bone marrow biopsy, 1 of the cases without diagnostic features of malignancy survived 10 additional years. Therefore, trisomy 2 as a sole abnormality should not be considered as definitive evidence for a myeloid neoplasm in the absence of diagnostic morphologic criteria.

New recurrent balanced translocations in acute myeloid leukemia and myelodysplastic syndromes: cancer and leukemia group B 8461

Acquired chromosome abnormalities in patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) are among the most valuable determinants of diagnosis and prognosis. In search of new recurrent balanced translocations, we reviewed the Cancer and Leukemia Group B (CALGB) cytogenetics database containing pretreatment and relapse karyotypes of 4,701 adults with AML and 565 with MDS who were treated on CALGB trials. We identified all cases with balanced structural rearrangements occurring as a sole abnormality or in addition to one other abnormality, excluded abnormalities known to be recurrent, and then reviewed the literature to determine whether any of what we considered unique, previously unknown abnormalities had been reported. As a result, we identified seven new recurrent balanced translocations in AML or MDS: t(7;11)(q22;p15.5), t(10;11)(q23;p15), t(2;12)(p13;p13), t(12;17)(p13;q12), t(2;3)(p21;p21), t(5;21)(q31;q22), and t(8;14)(q24.1;q32.2), and additionally, t(10;12)(p11;q15), a new translocation in AML previously reported in a case of acute lymphoblastic leukemia. Herein, we report hematologic and clinical characteristics and treatment outcomes of patients with these newly recognized recurrent translocations. We also report 52 unique balanced translocations, together with the clinical data of patients harboring them, which to our knowledge have not been previously published. We hope that once the awareness of their existence is increased, some of these translocations may become recognized as novel recurring abnormalities. Identification of additional cases with both the new recurrent and the unique balanced translocations will enable determination of their prognostic significance and help to provide insights into the mechanisms of disease pathogenesis in patients with these rare abnormalities.

Molecular and clinicopathologic characterization of AML with isolated trisomy 4

Acute myeloid leukemia (AML) with isolated trisomy 4 is rare. Associations with KIT mutations on chromosome 4q12 have been documented. The clinicopathologic features and mutational status of KIT, FLT3, NPM1, CEBPA, and RAS were assessed in 13 AML cases with isolated trisomy 4. There were 9 men and 4 women with a median age of 54 years. Median blast count was 84% (range, 24%-93%). Morphologic features varied across five 2008 World Health Organization categories. FLT3 (5/10) and NPM1 (4/10) mutations were observed at a frequency similar to normal-karyotype AML cases. KIT D816V (1/10), RAS (1/11; NRAS), and CEBPA (0/9) mutations were rare or absent. In 11 of 13 cases, complete remission was achieved. In 8 cases, relapse occurred, with median relapse-free survival of 11 months. Median overall survival was 28 months. AML with isolated trisomy 4 is rare and associated with high bone marrow blast counts and an intermediate to poor prognosis. KIT mutations are uncommon.

Y654 of β-catenin is essential for FLT3/ITD-related tyrosine phosphorylation and nuclear localization of β-catenin

β-Catenin plays a dual role as a key effecter in the regulation of adherens junctions as well as a transcriptional co-activator. Tyrosine phosphorylation of β-catenin affects the cell adhesion, migration, and gene transcription in many types of human cancer cells, including acute myeloid leukemia cells with FLT3 internal tandem duplication (FLT3/ITD-AML). Here, we investigated the relationship between three tyrosine residues (Y86, Y142, and Y654) in β-catenin and oncogenic FLT3/ITD kinase. In the experiments using COS-7 cells expressing FLT3/ITD and Wt or mutant β-catenin, FLT3/ITD phosphorylated Y654, and this residue was essential for β-catenin's nuclear localization by FLT3/ITD. Promoter-reporter assays demonstrated that Y654 phosphorylation of β-catenin was closely related to TCF transcriptional activity. In vitro kinase assays, using recombinant FLT3 and biotinylated β-catenin peptide including Y654 showed that FLT3 directly phosphorylated Y654 of β-catenin. These results explain how FLT3/ITD affects the tyrosine phosphorylation, nuclear localization, and transcriptional activity of β-catenin. Targeting Y654 phosphorylation may lead to the development of novel approaches to therapy for FLT3/ITD-AML.

Cytogenetic analysis of acute myeloid leukemia with t(8;21) from a tertiary care center in India with correlation between clinicopathologic characteristics and molecular analysis

The t(8;21)(q22;q22) is the most common translocation in acute myeloid leukemia (AML). We describe the clinicopathologic and cytogenetic profile of 117 patients with t(8;21) AML. There were 76 males and 88 adults. The median age was 26 years. Most patients (80%) had AML M2. Dysplasia was present in 68% of patients and eosinophilia in 18%. Eight patients had fewer than 20% blasts. Additional chromosomal aberrations were seen in 103 patients (88%) with loss of a sex chromosome (LSC) in 78 patients (66%) and deletion 9q in 21 (18%). The other recurrent abnormalities were trisomies 4, 8 and 15, monosomy 17 and deletion 7q (less than 5% each). Three- or four-way variant t(8;21) were seen in 6% of patients and 3% had tetraploidy. Aberrant expression of CD19 was seen in 54% of patients. FLT3 mutations were seen in 7.5% of patients (3/40) and c-KIT mutations in 6.6% (2/30). None had NPM1 or JAK2 V617F mutations. One patient had a granulocytic sarcoma. Complete remission was achieved in 96% of the 26 newly diagnosed patients after first induction. The median follow-up was 25 months (range 4-68). The overall survival was 69% at 31 months.

Cells expressing FLT3/ITD mutations exhibit elevated repair errors generated through alternative NHEJ pathways: implications for genomic instability and therapy

The internal tandem duplication (ITD) mutations of the FMS-like tyrosine kinase-3 (FLT3) receptor found in acute myeloid leukemia patients are associated with poor prognosis. Although DNA double-strand breaks (DSBs) are mainly repaired by the DNA-PK-dependent nonhomologous end-joining (NHEJ) pathway in normal mammalian cells, an alternative and less well-defined NHEJ pathway, characterized by microhomology at the repair junctions, play a role in the generation of deletions and translocations leading to cancer progression. Here we report that in FLT3/ITD-expressing cell lines and bone marrow mononuclear cells from FLT3/ITD knock-in mice, end-joining of DSBs occurs at microhomologous sequences resulting in a high frequency of DNA deletions. Strikingly, levels of Ku proteins, key components of the main NHEJ pathway, are decreased in FLT3/ITD(+) cell lines and murine FLT3/ITD bone marrow mononuclear cells. Concomitantly, levels of DNA ligase IIIα, a component of ALT NHEJ, are increased in FLT3/ITD-expressing cells. Cells treated with a FLT3 inhibitor demonstrate decreased DNA ligase IIIα and a reduction in DNA deletions, suggesting that FLT3 signaling regulates the pathways by which DSBs are repaired. Thus, therapy to inhibit FLT3/ITD signaling and/or DNA ligase IIIα may lead to repair that reduces repair errors and genomic instability.

[Clinical importance of morphological multilineage dysplasia in acute myeloid leukemia with myelodysplasia related changes]

BACKGROUND

AML with myelodysplasia related changes (AML MRC) is known to show a poor prognosis compared with de novo AML, but controversies exist about the prognostic impact of multilineage dysplasia (MLD) among MRC. We investigated the prognostic impact of MLD in AML MRC.

METHODS

A total of 357 patients newly diagnosed as AML at Asan Medical Center from January 2001 to December 2005 were analyzed. They were diagnosed and classified as AML with recurrent genetic abnormalities, AML MRC, and AML not otherwise specified (AML NOS). Prognostic markers including overall survival (OS) and event free survival (EFS) were obtained through retrospective analysis of electronic medical records.

RESULTS

AML MRC patients showed a lower complete remission (CR) rate (44.7% vs. 64.9%, P=0.002) and shorter OS (297 vs. 561 days, P=0.004) and EFS (229 vs. 374 days, P=0.004) than AML NOS patients. Patients with MLD among AML MRC also showed a lower CR rate (37.7%, P=0.001) and shorter OS (351 days, P=0.036) and EFS (242 days, P=0.076) than AML NOS patients. However, among AML MRC patients, there were no differences in OS, EFS and CR between patients with and without MLD.

CONCLUSIONS

AML MRC patients showed a lower CR rate and shorter OS and EFS than AML NOS patients. AML MRC patients with MLD showed similar results and their prognosis was not different from those without MLD. MLD findings among AML MRC could be an independent poor prognostic factor in de novo AML.

A hospital-based case-control study of non-Hodgkin lymphoid neoplasms in Shanghai: analysis of personal characteristics, lifestyle, and environmental risk factors by subtypes of the WHO classification

OBJECTIVES

To investigate potential risk factors (personal characteristics, lifestyle, and environmental factors) of non-Hodgkin lymphoid neoplasms (NHLN), including lymphomas and lymphocytic leukemia, according to the World Health Organization classification.

MATERIALS AND METHODS

The investigation was a hospital-based case-control study consisting of 649 confirmed NHLN cases and 1298 individually gender-age-matched patient controls at 25 hospitals in Shanghai. A 17-page questionnaire was used to obtain information on demographics, medical history, family history, lifestyle risk factors, employment history, residential history, and occupational and non-occupational exposures. Risk estimates were calculated using conditional logistic regression models.

RESULTS

Potential risk factors of NHLN (all subtypes combined) or individual subtypes included low-level education, home or workplace renovation, living on a farm, planting crops, and raising livestock or animals. Some risk factors applied to all or most subtypes (such as lowlevel education, living on a farm, and raising livestock or animals), whereas others did not (such as the use of traditional Chinese medicines, which was associated with a reduced risk). Blood transfusions, hair dyes, or living near high-voltage power lines were not associated with an increased risk.

CONCLUSIONS

The study identified a number of risk factors for NHLN overall and specific subtypes. Some risk factors were subtype-specific. The difference in risk by subtype underscores the etiologic commonality and heterogeneity of NHLN subtypes.

Adult precursor B lymphoblastic leukemia in Shanghai, China: characterization of phenotype, cytogenetics and outcome for 137 consecutive cases

Acute lymphoblastic leukemia (ALL) accounts for 20-30% of adult leukemia in the West. However, detailed studies of B-cell-specific ALL in adult Asian populations are lacking. We diagnosed and characterized 137 consecutive cases of precursor B lymphoblastic leukemia (precursor B-cell ALL) presented to our laboratory in Shanghai using the WHO 2001 classification system. Patient clinical, phenotypic and cytogenetic characteristics were correlated with outcome. In contrast to Western studies, females (71) outnumbered males (66) partly due to an increased prevalence of the CD10- pro B-cell phenotype. Females with a CD10- pro B-cell phenotype exhibited significantly better overall survival than males. The most common cytogenetic abnormality was the Philadelphia chromosome (PH/BCR/ABL) which was found in approximately 37% of the cases. Cases of precursor B cell ALL lacking the PH/BCR/ABL genotype exhibited a pronounced age-dependent, gender prevalence with a modal age in the sixth decade for females compared to the second decade for males. These findings suggest significant geographic heterogeneity in precursor B-cell ALL which may be of both etiological and therapeutic significance.

Clinical characterization of acute myeloid leukemia with myelodysplasia-related changes as defined by the 2008 WHO classification system

Although some studies have validated the 2001 World Health Organization (WHO) classification of acute myeloid leukemia (AML), including the importance of multilineage dysplasia, others have suggested that multilineage dysplasia correlates with unfavorable cytogenetics but has no independent impact on prognosis. In 2008, the revised WHO classification has expanded this category into “AML with myelodysplasia-related changes” (AML-MRC). We evaluated the clinical, pathologic, cytogenetic, and molecular features of 100 AML patients using the 2008 WHO criteria. Patients underwent genetic screening for NPM1, FLT3-ITD, FLT3-D835, and CEBPA mutations. Compared with patients with AML, not otherwise specified, patients with AML-MRC were significantly older (P = .014), presented with a lower hemoglobin (P = .044), more frequently expressed CD14 (P = .048), and exhibited a decreased frequency of CEBPA mutations (P = .001). Multivariate analysis indicated that patients with AML-MRC had a significantly worse overall survival, progression-free survival, and complete response compared with AML-not otherwise specified (all P < .001). These data support the clinical, morphologic, and cytogenetic criteria for this 2008 WHO AML category.

Targeting FLT3 for the treatment of leukemia

FLT3 is a receptor tyrosine kinase with important roles in hematopoietic stem/progenitor cell survival and proliferation. It is frequently overexpressed in acute leukemias and is frequently mutated in acute myeloid leukemia (AML). FLT3 internal tandem duplication (ITD) mutations in AML portend poor prognosis in both adult and pediatric patients. A number of small molecule tyrosine kinase inhibitors (TKIs) with activity against FLT3 have been discovered. Many of these are still in preclinical development, but several have entered clinical phase I and II trials as monotherapy in patients with relapsed AML. These trials have resulted in frequent but short-lived responses of peripheral blasts and less frequent responses of bone marrow blasts. This led to clinical testing of FLT3 TKIs in combination with conventional chemotherapy. Several combination trials are ongoing or planned in both relapsed and newly diagnosed FLT3-mutant AML patients. Anti-FLT3 antibodies may also prove to be an excellent way of targeting FLT3 in AML and acute lymphocytic leukemia (ALL) by inhibiting signaling and through antibody-dependent cell-mediated cytotoxicity.

Tetrasomy 8 in a patient with acute monoblastic leukemia

Trisomy 8 is one of the most frequent numerical chromosomal abnormalities observed in hematological malignancies, whereas tetrasomy 8 is a clonal aberration seen mainly in myeloid disorders such as acute myelod leukemia (AML) and myelodysplastic syndromes. In contrast to trisomy 8, tetrasomy 8 is a rare chromosomal aberration, in that only 17 reported AML cases with isolated tetrasomy 8 have been documented. Interestingly, the majority of reported cases were associated with monocytic-lineage leukemias. According to recent reports, tetrasomy 8 is regarded as a poor prognostic factor, and most patients having this abnormality relapsed and died within 1 yr. Here, we report a patient with acute monoblastic leukemia having tetrasomy 8 and a very aggressive disease course.

Diagnosis of acute myeloid leukemia according to the WHO classification in the Japan Adult Leukemia Study Group AML-97 protocol

We reviewed and categorized 638 of 809 patients who were registered in the Japan Adult Leukemia Study Group acute myeloid leukemia (AML)-97 protocol using morphological means. Patients with the M3 subtype were excluded from the study group. According to the WHO classification, 171 patients (26.8%) had AML with recurrent genetic abnormalities, 133 (20.8%) had AML with multilineage dysplasia (MLD), 331 (51.9%) had AML not otherwise categorized, and 3 (0.5%) had acute leukemia of ambiguous lineage. The platelet count was higher and the rate of myeloperoxidase (MPO)-positive blasts was lower in AML with MLD than in the other WHO categories. The outcome was significantly better in patients with high (≥50%) than with low (<50%) ratios of MPO-positive blasts (P < 0.01). The 5-year survival rates for patients with favorable, intermediate, and adverse karyotypes were 63.4, 39.1, and 0.0%, respectively, and 35.5% for those with 11q23 abnormalities (P < 0.0001). Overall survival (OS) did not significantly differ between nine patients with t(9;11) and 23 with other 11q23 abnormalities (P = 0.22). Our results confirmed that the cytogenetic profile, MLD phenotype, and MPO-positivity of blasts are associated with survival in patients with AML, and showed that each category had the characteristics of the WHO classification such as incidence, clinical features, and OS.

Isochromosome (X)(p10) in hematologic disorders: FISH study of 14 new cases show three types of centromere signal patterns

Though X chromosome anomalies are uncommon in hematologic malignancies, isodicentric X chromosomes, idic(X)(q13), with break and fusion points at Xq13 are well known among older females with de novo myelodysplasia. In contrast, only 17 patients with X isochromosomes involving break and fusion points at the centromere i(X)(p10) have been published, to our knowledge. We present 14 new patients with i(X)(p10) identified by G-banding and further characterized by fluorescence in situ hybridization (FISH) using probes for the X p-arm, X alpha-satellite DNA (DXZ1), and the XIST gene (Xq13). These anomalies each had an X p-arm probe signal on either side of a single centromeric FISH signal, thus they are monocentric isochromosomes. On the basis of FISH, the following three centromeric patterns were identified: (1) centromere signal same size as normal X, (2) centromere signal larger than normal X, and (3) centromere signal smaller than normal X. These centromere patterns may be related to the mechanism of i(X)(p10) formation. In 9 (64%) of 14 patients, the i(X)(p10) was the sole anomaly, attesting to its pathogenic potential. Our series, when collated with information on previously reported cases of i(X)(p10), show that this anomaly is associated with females with a median age 74 years, though patients from 3.75 to 49 years, including a 17-year-old in the present cohort, have been described. i(X)(p10) is observed in a wide range of hematologic malignancies, including myeloid and lymphoid disorders, as well as a patient with therapy-related AML in the present series. i(X)(p10) has been reported in occasional males, indicating that this anomaly can arise from active X chromosomes. It is not known whether i(X)(p10) arises randomly from the active or inactive X chromosome in female patients.

PKC 412 small-molecule tyrosine kinase inhibitor

BACKGROUND

PKC412 is a kinase inhibitor that blocks protein kinase C (PKC), vascular endothelial growth factor receptors, platelet-derived growth factor receptor FLT3, and other class III receptor tyrosine kinases. The enthusiasm for this compound is based on its inhibitory effect even in the case of FLT3 mutations. The aim of this study was to analyze the role of FLT3 in pancreatic cancer and to study the biological activity of combined inhibition of neovascularization and mitogenesis in this disease.

METHODS

FLT3 expression was analyzed in 18 pancreatic cancer specimens by real-time quantitative polymerase chain reaction (RTQ-PCR) and immunohistochemistry. Sixteen pancreatic cancer cell lines were screened for ITD and D835 point mutations of the FLT3 gene. MTT assays and anchorage-independent growth assays were used to study cell growth. Flow cytometry was used for cell cycle analysis and apoptosis quantification. In vivo AsPC-1 and HPAF-II cells were used for orthotopic tumor modeling. Immunohistochemistry was used to quantify tumor angiogenesis.

RESULTS

FLT3 expression is down-regulated in pancreatic cancer. Activating FLT3 mutations (ITD, D835) were not detectable in any of the pancreatic cancer cell lines. Cell growth was significantly inhibited as cell-cycle progression was reduced and programmed cell death increased. In vivo PKC412 therapy resulted in a significant inhibition of orthotopic tumor growth with abrogation of tumor angiogenesis.

CONCLUSIONS

These data highlight that PKC412 may be a new compound in target therapy of inoperable pancreatic cancer patients and suggest a potential role for the combined use of broad spectrum kinase inhibitors in the management of these patients.