Morphology antibody chromosome technique for determining phenotype and genetic status of the same cell

The morphology antibody chromosome (MAC) technique is a combination of methods that permits analysis of both phenotypic and genetic evaluation on a single interphase or mitotic cell as a basis for lineage analysis of neoplastic and normal cells. This unit describes MAC with sequential phenotypic analysis using antibody and an alkaline phosphatase anti-alkaline phosphatase (APAAP) complex and genotypic analysis using in situ hybridization with either enzymatic or fluorescence detection. Alternate methods for phenotypic analysis are also described, which include the use of horseradish peroxidase-conjugated antibodies, fluorochrome-conjugated antibodies, May-Grunwald-Giemsa cytochemical staining, and Sudan black B cytochemical staining. An additional protocol describes G- and C-banding as alternatives to in situ hybridization (ISH) for genotyping MAC specimens. Support protocols describe methods for preparing specimens, cytospin preparations, in situ cultures, paraffin-embedded or cryostat sections, and blood and bone marrow smears. Also described is a procedure for chromosome painting of previously GTG-banded slides. An additional protocol is included for FISH analysis on sorted hematopoietic stem cells and its application in the detection of leukemic stem cells. For overcoming the drawbacks of scarcity and variability from case to case of malignant plasma cells in multiple myeloma FISH analyses, a protocol is included for the enrichment of plasma cells by immunomagnetic beads.

Phosphoprotein profiling predicts response to tyrosine kinase inhibitor therapy in chronic myeloid leukemia patients

Tyrosine kinase inhibitors (TKIs) have dramatically improved treatment outcomes in chronic myeloid leukemia (CML), but a proportion of patients fail to achieve optimal molecular response. By using a phosphoproteomic approach, we aimed to discover aberrant signaling pathways and putative biomarkers in bone marrow samples of suboptimally responding patients, which could be used to guide treatment selection at the diagnosis. The study consisted of 20 chronic-phase CML patients (10 optimal and 10 suboptimal response patients based on 18 months European-Leukemia-Net criteria) and healthy bone marrow cells, and CML cell lines were used as controls. The phosphorylation profile of normal bone marrow cells diverged from CML patients expectedly but, interestingly, CML cell lines (such as K562) also showed marked difference with primary CML cells. Several phosphoproteins were elevated in suboptimal patients compared to optimal response group. Most prominent differences were seen in signal transducers and activators of transcription 5b, phospholipase C γ-1, proline-rich tyrosine kinase 2, Hck, and Paxillin. These phosphoproteins were also increased in three additional nonresponder patients studied, but each of them also had unique phosphorylation patterns, such as highly active HSP27 protein in one patient. In conclusion, suboptimal imatinib response is related to increased phosphorylation of several proteins at diagnosis, which might guide the selection of TKI therapy. Furthermore, the activation of additional BCR-ABL-independent pathways in nonresponder patients (such as the anti-apoptotic HSP27 pathway) may reveal novel therapy targets.

Somatic STAT3 mutations in large granular lymphocytic leukemia

BACKGROUND

T-cell large granular lymphocytic leukemia is a rare lymphoproliferative disorder characterized by the expansion of clonal CD3+CD8+ cytotoxic T lymphocytes (CTLs) and often associated with autoimmune disorders and immune-mediated cytopenias.

METHODS

We used next-generation exome sequencing to identify somatic mutations in CTLs from an index patient with large granular lymphocytic leukemia. Targeted resequencing was performed in a well-characterized cohort of 76 patients with this disorder, characterized by clonal T-cell-receptor rearrangements and increased numbers of large granular lymphocytes.

RESULTS

Mutations in the signal transducer and activator of transcription 3 gene (STAT3) were found in 31 of 77 patients (40%) with large granular lymphocytic leukemia. Among these 31 patients, recurrent mutational hot spots included Y640F in 13 (17%), D661V in 7 (9%), D661Y in 7 (9%), and N647I in 3 (4%). All mutations were located in exon 21, encoding the Src homology 2 (SH2) domain, which mediates the dimerization and activation of STAT protein. The amino acid changes resulted in a more hydrophobic protein surface and were associated with phosphorylation of STAT3 and its localization in the nucleus. In vitro functional studies showed that the Y640F and D661V mutations increased the transcriptional activity of STAT3. In the affected patients, downstream target genes of the STAT3 pathway (IFNGR2, BCL2L1, and JAK2) were up-regulated. Patients with STAT3 mutations presented more often with neutropenia and rheumatoid arthritis than did patients without these mutations.

CONCLUSIONS

The SH2 dimerization and activation domain of STAT3 is frequently mutated in patients with large granular lymphocytic leukemia; these findings suggest that aberrant STAT3 signaling underlies the pathogenesis of this disease. (Funded by the Academy of Finland and others.).

Abstract 895: Quantitative drug sensitivity and resistance testing (DSRT) of primary ex vivo AML blasts highlights mTOR and MEK as potential key molecular driver signals of therapeutic significance

Identification of signaling pathways that are required for the growth and differentiation block of cells from adult acute myeloid leukemia (AML) is urgently required to facilitate development of novel therapies. Here, we describe an approach to functionally determine molecular drivers of AML by quantitative drug sensitivity and resistance testing (DSRT) of AML blast cells in primary culture ex vivo. The selection of drugs covered the entire cancer pharmacopeia and much of the pipeline of drugs under development in the industry: 120 FDA approved small molecular cancer drugs and 120 emerging drugs, investigational compounds and signal transduction inhibitors. All compounds were tested over a 10,000-fold concentration range to generate quantitative and reliable dose-response data. In addition, whole exome and transcriptome sequencing and phophoproteomic profiling were also performed to derive a comprehensive understanding of the molecular AML-related aberrations on an individual basis. Comparison of 17 AML patient samples and 3 healthy bone marrow control samples based on ex vivo drug responses identified several classes of approved and investigational drugs that showed selective anti-AML activities: mTOR inhibitors (e.g. temsirolomus, everolimus, sirolimus), MEK inhibitors (e.g. AS703026, GSK1120212, RDEA119, selumetinib), tyrosine kinase inhibitors (e.g. dasatinib, ponatinib, sunitinib), Bcl-2 inhibitors (navitoclax) and HSP90 inhibitors (e.g. BIIB021, NVP-AUY922, tanespimycin). In particular, the rapamycin class of mTOR inhibitors and allosteric MEK inhibitors stood out as effective and selective inhibitors in 8/17 (47%) and 9/17 (52%) of the patients, respectively. Simultaneous data from other targeted inhibitors made it possible to dissect the critical steps in signaling and therapeutic efficacy. For example, PI3K and Akt inhibitors were not effective in these patients, suggesting that the mTOR dependency is mediated through a PI3K-Akt-independent pathway. Similarly, the dependency of MEK signaling appears to be through a Ras-Raf-independent pathway since Raf inhibitors were not effective. In conclusion, the DSRT platform allows us to derive quantitative data on the ex vivo drug response profiles of AML cells from individual patients. This information could be used as a diagnostic tool to optimize personalized therapies in the future. Our data demonstrate that mTOR and MEK signaling and the associated inhibitors are the most promising leads for improved AML therapeutics. This analysis also demonstrates gaps in our current understanding of the redundancy of key cancer cell signaling pathways and proves the significant value of data from experimental drug response testing ex vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 895. doi:1538-7445.AM2012-895

Abstract 5067: Exome sequencing reveals both DNA sequence and copy number changes in AML: Potential driver changes and mechanisms of drug resistance revealed from serial samples from the same patients

Despite significant advances in characterizing the molecular genetics of AML, the clonal evolution of leukemic cells and the dynamic impact of genomic changes on the development of the disease and progression to drug resistance are not well understood. Here, we applied next-generation sequencing to quantify aberrant tumor subclones carrying specific mutant alleles of key cancer genes and developed a method to extract quantitative high-resolution copy number changes across the genome using exome sequencing data from matching cancer and normal DNA. Serial bone marrow (BM) samples collected from diagnosis to relapse to post-treatment drug resistance in a patient-centric manner made it possible to trace the clonal evolution of AML and to identify variants potentially involved in drug resistance. Exome sequencing from AML blast cells and normal skin biopsies was performed as part of the Finnish Hematology Registry and Biobanking (FHRB) effort. Consecutive paired samples from different patients revealed unique genetic patterns of clonal evolution and cancer progression in each patient. In a pre-resistant sample of one AML M5 patient, we identified four closely spaced insertions in the Wilm's Tumor (WT1) suppressor gene, none of which appear on the same sequence reads. This suggests the presence of multiple distinct leukemic subclones even before treatment resistance and underscores the strong selective advantage conferred by WT1 mutations. After relapse, one of the subclones was lost, and another one significantly increased suggesting that the relapse arose from the expansion of a pre-existing resistant subclone. In this patient, recurrent clones otherwise featured similar copy number changes and the same fusion genes as the primary diagnostic sample. In another AML patient developing recurrence an opposite pattern was observed: The relapsed, drug-resistant cells displayed an enormous increase of small microdeletions compared to the diagnostic, pre-treatment sample, while almost all sequence-level alterations in potential cancer genes were the same between the two samples. This suggests that a distinct type of DNA repair deficiency may have contributed to the drug resistant clone in this patient. Conclusions: Exome sequencing from paired samples of AML cells before and after relapse makes it possible to trace the clonal evolution of the disease and study the impact of therapy both at the level of sequence alterations of key cancer genes and simultaneously at the level of copy number changes inferred from exome sequence data. This analysis has highlighted multiple genomic patterns by which resistance may evolve in vivo during cancer treatment. Refined bioinformatic analysis and interpretation of exome-seq data provides a rich resource to identify genetic biomarkers of drug response and minimal residual disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5067. doi:1538-7445.AM2012-5067

Abstract 3188: Development of a cancer pharmacopeia-wide ex-vivo drug sensitivity and resistance testing (DSRT) platform for AML: Towards individually optimized therapy and improved understanding of drug resistance patterns

In order to discover unexpected anti-cancer efficacies of approved and emerging drugs, we established a diagnostic ex vivo drug sensitivity and resistance testing (DSRT) platform covering the entire cancer pharmacopeia as well as emerging anti-cancer compounds. Here, the platform was applied to analyze bone marrow (BM) mononuclear cells from 17 adult acute myeloid leukemia (AML) patients, 3 healthy donors as well as 7 AML cell lines. The DSRT panel covered FDA-approved small molecule oncology drugs (n=120), as well as emerging, investigational and pre-clinical oncology compounds (n=120), such as kinase (e.g. RTKs, checkpoint and mitotic kinases, Raf, MEK, JAKs, mTOR, PI3K), and non-kinase inhibitors (e.g. HSP, Bcl, activin, HDAC, PARP, Hh). To generate dose-response curves, each of the drugs was applied over a 10,000-fold concentration range. In addition, the samples underwent deep molecular profiling including exome- and transcriptome sequencing, as well as phosphoproteomic analysis. DSRT provided consistent and reliable data from ex vivo samples with a high correlation between data from individual healthy BM samples (r=0.93). Bioinformatic processing of the data from AML resulted in several key observations. First, overall drug response profiles of AML blast cells were distinctly different from healthy BM controls suggesting several potential leukemia-selective effects, such as multi-kinase (dasatinib), MEK, and mTOR inhibitors. Second, the overall drug responses from AML cell lines and the patient ex vivo samples showed differences, suggesting that ex vivo testing may reveal cancer-selective effects not previously seen in established cancer cell line panels. Third, the response data from patient samples clustered many drugs consistently into the expected functional classes (such as topoisomerase II inhibitors, MEK inhibitors and rapalogs), whereas other drug classes were more dispersed (such as FLT3 inhibitors with quizartinib clustering away from all other tyrosine kinase inhibitors), suggesting secondary targets playing a key role in drug efficacy. Fourth, analysis of serial samples from patients developing clinical resistance to targeted agents showed striking agreement between the ex-vivo DSRT profiles and clinical responses. In conclusion, comprehensive DSRT platform generated powerful novel insights on AML drug response and may enable individual optimization of therapies, particularly for recurrent leukemias. DSRT will also serve as a powerful hypothesis-generator for clinical trials, particularly for emerging drugs. The ability to correlate ex vivo response profiles for hundreds of drugs in clinical samples with deep molecular profiling data will yield exciting new translational and pharmacogenomic opportunities for cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3188. doi:1538-7445.AM2012-3188

[Current therapy of chronic myeloid leukemia]

Chronic myeloid leukemia (CML) originates from a hematopoietic stem cell carrying the Philadelphia (Ph) chromosome and oncogenic BCR-ABL1 fusion gene. The first tyrosine-kinase inhibitor (TKI) imatinib was introduced to clinical practice 10 years ago, and it radically improved the outcome of CML patients. The rare patients that are imatinib resistant or intolerant can be treated with second generation TKIs such as dasatinib or nilotinib. As second generation TKIs appear to be more effective than imatinib and well tolerated, they may become standard first-line treatment for CML. The major future aim in CML is curative drug therapy.

Expansion of highly differentiated CD8+ T-cells or NK-cells in patients treated with dasatinib is associated with cytomegalovirus reactivation

The tyrosine kinase inhibitor dasatinib exerts immunosuppressive effects on T-cells and NK-cells in vitro. However, in some dasatinib-treated leukemia patients, clonal lymphocytosis with large granular lymphocyte (LGL) morphology develops, and this is associated with enhanced therapeutic responses. To elucidate the mechanistic basis for this paradoxical observation, we conducted detailed phenotypic and functional analyses of T-cell and NK-cell populations from 25 dasatinib-treated leukemia patients. All tested patients with LGL expansions (15/16) were cytomegalovirus (CMV) immunoglobulin (IgG) seropositive with high frequencies of CMV-specific CD8(+) T-cells; 5/16 LGL patients also experienced symptomatic CMV reactivation during dasatinib therapy. Expanded T-cell and NK-cell populations exhibited late differentiated (CD27(-)CD57(+)) phenotypes; this was associated with a predisposition to apoptosis within the T-cell compartment and impaired NK-cell cytotoxicity. Only 3/9 non-LGL patients were CMV IgG seropositive. Dasatinib inhibited in vitro lymphocyte functions, similarly in LGL patients and controls. Notably, distinct CD8(high) and CD8(low) T-cell subsets were observed in LGL patients; this phenotypic dichotomy was also apparent in CMV-specific CD8(+) T-cell populations, and exhibited features consistent with antigen-driven activation. In addition, plasma levels of IP-10, IL-6, monokine induced by interferon-γ and interleukin-2R were significantly increased in LGL patients. These data provide evidence that dasatinib-associated LGL expansion is linked to CMV reactivation and suggest a potential mechanism for this phenomenon.

Chronic myeloid leukemia patients in prolonged remission following interferon-α monotherapy have distinct cytokine and oligoclonal lymphocyte profile

Before the era of tyrosine kinase inhibitors (TKIs), interferon-alpha (IFN-α) was the treatment of choice in chronic myeloid leukemia (CML). Curiously, some IFN-α treated patients were able to discontinue therapy without disease progression. The aim of this project was to study the immunomodulatory effects of IFN-α in CML patients in prolonged remission and isolate biological markers predicting response. Due to rarity of patients on IFN-α monotherapy, a relatively small cohort of patients still on treatment (IFN-ON, n = 10, median therapy duration 11.8 years) or had discontinued IFN-α therapy but remained in remission for >2 years (IFN-OFF, n = 9) were studied. The lymphocyte immunophenotype was analyzed with a comprehensive flow cytometry panel and plasma cytokine levels were measured with multiplex bead-based assay. In addition, the clonality status of different lymphocyte subpopulations was analyzed by TCR γ/δ rearrangement assay. Median NK-cell absolute number and proportion from lymphocytes in blood was higher in IFN-OFF patients as compared to IFN-ON patients or controls (0.42, 0.19, 0.21×10⁹/L; 26%, 12%, 11%, respectively, p<0.001). The proportion of CD8+ T-cells was significantly increased in both patient groups and a larger proportion of T-cells expressed CD45RO. Most (95%) patients had significant numbers of oligoclonal lymphocytes characterized by T-cell receptor γ/δ rearrangements. Strikingly, in the majority of patients (79%) a distinct clonal Vγ9 gene rearrangement was observed residing in γδ⁺ T-cell population. Similar unique clonality pattern was not observed in TKI treated CML patients. Plasma eotaxin and MCP-1 cytokines were significantly increased in IFN-OFF patients. Despite the limited number of patients, our data indicates that IFN-α treated CML patients in remission have increased numbers of NK-cells and clonal γδ⁺ T-cells and a unique plasma cytokine profile. These factors may relate to anti-leukemic effects of IFN-α in this specific group of patients and account for prolonged therapy responses even after drug discontinuation.

Suboptimal responses in chronic myeloid leukemia: milestones and mechanisms

Patients with chronic myeloid leukemia who fail to achieve timely treatment responses have a worse prognosis. Although many patients respond well to first-line treatment with imatinib, a significant proportion relapse or experience an inadequate response. Since effective alternative Bcr-Abl inhibitors are available (i.e., dasatinib or nilotinib), several regional groups have proposed milestones for imatinib failure or suboptimal response based on the achievement of specified levels of response within a defined treatment duration. A suboptimal response indicates that, although patients may continue to receive a benefit from continuing imatinib treatment at the assigned dose, long-term outcome may be better with an alternative strategy. The underlying mechanisms behind suboptimal responses are multifactorial and may differ from those causing relapse.

A molecular and functional analysis of large granular lymphocyte expansions in patients with chronic myelogenous leukemia treated with tyrosine kinase inhibitors

Tyrosine kinase inhibitor (TKI) therapy has become the standard treatment for chronic myelogenous leukemia (CML). Off-target kinase inhibition has been implicated in the appearance of unique adverse effects, such as colitis and pleural effusions. In addition, some patients present oligoclonal expansions of large granular lymphocytes (LGLs). We sought to further investigate this phenomenon in 64 patients treated with five different TKIs. Clonal expansions of cytotoxic T lymphocytes (CTLs) were identified in all TKI-treated patient groups, but only in dasatinib-treated patients were these expansions characterized as LGLs. Survival factors known to be important in LGL leukemia (interleukin-15 [IL-15] transpresentation, plasma platelet-derived growth factor [PDGF]-BB levels, nuclear factor-κB [NF-κB] and T-bet activation) were found to be associated with TKI-induced LGL expansions. Interestingly, patients with LGL expansions had increased cytotoxicity against non-transformed endothelial cells, which may play a role in observed autoimmune-like side effects. Our results indicate that patients with CML treated with TKIs can develop T cell expansions, which can in certain cases be related to some adverse effects.

Immunoprofiling of patients with chronic myeloid leukemia at diagnosis and during tyrosine kinase inhibitor therapy

Tyrosine kinase inhibitors (TKIs) are the current standard treatment in chronic myeloid leukemia (CML). In addition to the BCR-ABL target oncoprotein, they also inhibit off-target kinases (e.g. c-KIT, TEC, SRC), some of which have physiological functions in immune responses. In vitro studies have implied immunosuppressive effects of TKI treatment. As comprehensive in vivo data are missing, we aimed at analyzing the detailed immunoprofile of patients with CML at diagnosis and during therapy. We collected 88 peripheral blood (PB) and 73 bone marrow (BM) samples from 54 patients with CML at diagnosis, during imatinib and dasatinib therapies. Leukocytes and lymphocyte subclasses were analyzed with an extensive flow cytometry panel including markers for activation, differentiation and memory status. At diagnosis, a lower proportion of B cells and dendritic cells and an increased amount of NKT-like cells were detected in the BM. During imatinib therapy, all these changes normalized and the immunoprofile resembled healthy controls. However, dasatinib patients were clearly divided into two distinct groups: one similar to healthy controls and the other showing immunoactivation characterized by significant elevations of CD8+, NK- and NKT-like cells in PB. T cells of the latter group strongly expressed CD57+, HLA-DR and CD45RO and had low CD62L antigen levels characteristic of late memory cytotoxic lymphocytes. Our results indicate that while both TKIs show immunosuppressive effects in vitro, they have a significant and differential effect on the numbers and proportions of immune effector cells in vivo. In particular, in a distinct subgroup of dasatinib-treated patients, immune reactivity is markedly enhanced warranting careful follow-up.

Poor cytokine-induced phosphorylation in chronic myeloid leukemia patients at diagnosis is effectively reversed by tyrosine kinase inhibitor therapy

OBJECTIVE

In chronic myeloid leukemia (CML), uncontrolled tyrosine kinase activity of the BCR-ABL1 oncoprotein results in aberrant signaling pathways and increased cell proliferation. Acquired immune tolerance to leukemic antigens further enables tumor cell expansion. Tyrosine kinase inhibitor (TKI) therapy interferes with the immunoregulatory system by targeting off-target kinases both in malignant and nonmalignant cells. The aim of this study was to analyze the immune cell function by phosphoprotein profiling in CML patients.

MATERIALS AND METHODS

Blood samples from diagnostic phase and TKI-treated patients were analyzed by multicolor phosphoprotein flow cytometry enabling measurements at the single-cell level. Both unstimulated baseline activation status and cytokine-induced responses were evaluated.

RESULTS

In diagnostic-phase and imatinib-treated patients, the baseline phosphoprotein activation status was similar to healthy controls. In dasatinib-treated patients, basal phosphoprotein levels were slightly decreased; in particular, the signal transduction and activator of transcription protein 3 pathway was affected in both myeloid and lymphoid cells. The activation responses to various cytokines, granulocyte-macrophage colony-stimulating factor in particular were significantly suppressed in untreated CML patients. During imatinib and dasatinib therapy, the aberrantly suppressed phosphorylation responses were normalized.

CONCLUSIONS

Cytokine responses are hampered in untreated CML patients, which may have an effect on various immunological processes in vivo. Interestingly, during TKI treatment, phosphorylation responses were normal, suggesting that TKI treatment does not alter the reactivity of healthy immune effector cells. However, dasatinib treatment was associated with diminished basal activation of the immunosuppressive signal transduction and activator of transcription protein 3 signaling pathway, which could have clinical significance in reversing the lymphocyte anergy against tumor cells.

Impact of tyrosine kinase inhibitors on patient outcomes in Philadelphia chromosome-positive acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is a heterogeneous disease that is often associated with several chromosomal and molecular abnormalities. Patients who have the Philadelphia (Ph) chromosome and associated BCR-ABL1 oncogene have a particularly poor prognosis. Currently, allogeneic haematopoietic stem cell transplantation (allo-HSCT) is the only known curative treatment for Ph+ ALL and facilitating allo-HSCT in eligible patients is a key treatment goal. However, many patients relapse after allo-HSCT, particularly those with measurable residual disease prior to transplantation, and a significant percentage of patients are ineligible for allo-HSCT, particularly older patients. Hence, many patients require additional/alternative therapies to prolong survival. Studies are ongoing to determine the most effective first-line drug regimens for patients who subsequently undergo allo-HSCT and ineligible patients. Tyrosine kinase inhibitors targeted to Bcr-Abl are important novel therapies for Ph+ ALL. Although imatinib administered in combination with chemotherapy is established as the current first-line strategy, relapse is common, even among allo-HSCT recipients. Emerging data indicate that more potent multi-targeted kinase inhibitors (including dasatinib, nilotinib, and bosutinib) have promising efficacy in the first- or second-line setting. Here, the evidence base for existing drug treatments for Ph+ ALL is discussed and emerging therapeutic strategies are explored.

JAK2V617F mutation and spontaneous megakaryocytic or erythroid colony formation in patients with essential thrombocythaemia (ET) or polycythaemia vera (PV)

The in vitro cultures of erythroid (BFU-E) and megakaryocytic (CFU-Meg) progenitors have been useful diagnostic tools in myeloproliferative disorders (MPD). However, after the discovery of the JAK2V617F mutation, their diagnostic role has been uncertain. In this single-centre retrospective study we analyzed JAK2V617F mutation in 58 ET and 42 PV patients diagnosed according to WHO criteria and compared the results with those of colony forming assays with special emphasis on CFU-Meg growth. 91% of PV and 57% of ET patients had JAK2V617F mutation and they all showed spontaneous BFU-E growth. However, endogenous BFU-E formation was also seen in nine JAK2V617F mutation negative patients displaying also a normal JAK2 exon 12 allele. Endogeneous CFU-Meg colony formation was found in 59% of PV and 53% of the ET patients. A subgroup of ET patients (n=7) displayed sole spontaneous CFU-Meg growth without spontaneous BFU-E growth. They all were JAK2 mutation negative, but one of them had MPL mutation. In conclusion, in vitro cultures of haematopoietic progenitors are sensitive diagnostic tools in the present group of 100 MPD patients revealing also JAK2 mutation negative ET and PV patients displaying sole spontaneous CFU-Meg or BFU-E growth.

VEGFR-3 and CD133 identify a population of CD34+ lymphatic/vascular endothelial precursor cells

Human CD133 (AC133)(+)CD34(+) stem and progenitor cells derived from fetal liver and from bone marrow and blood incorporate a functional population of circulating endothelial precursor cells. Vascular endothelial growth factor receptor 3 (VEGFR-3) regulates cardiovascular development and physiological and pathological lymphangiogenesis and angiogenesis. However, the origin of VEGFR-3(+) endothelial cells (ECs) and the mechanisms by which these cells contribute to postnatal physiological processes are not known, and the possible existence of VEGFR-3(+) lymphatic or vascular EC progenitors has not been studied. Using monoclonal antibodies to the extracellular domain of VEGFR-3, we show that 11% +/- 1% of CD34(+) cells isolated from human fetal liver, 1.9% +/- 0.8% CD34(+) cells from human cord blood, and 0.2% +/- 0.1% of CD34(+) cells from healthy adult blood donors are positive for VEGFR-3. CD34(+)VEGFR-3(+) cells from fetal liver coexpress the stem/precursor cell marker CD133 (AC133). Because mature ECs do not express CD133, coexpression of VEGFR-3 and CD133 on CD34(+) cells identifies a unique population of stem and progenitor cells. Incubation of isolated CD34(+)VEGFR-3(+) cells in EC growth medium resulted in a strong proliferation (40-fold in 2 weeks) of nonadherent VEGFR-3(+) cells. Plating of these cells resulted in the formation of adherent VEGFR-3(+)Ac-LDL(+) (Ac-LDL = acetylated low-density lipoprotein) EC monolayers expressing various vascular and lymphatic endothelial-specific surface markers, including CD34, VE-cadherin, CD51/61, CD105, LYVE-1, and podoplanin. These data demonstrate that human CD34(+)CD133(+) cells expressing VEGFR-3 constitute a phenotypically and functionally distinct population of endothelial stem and precursor cells that may play a role in postnatal lymphangiogenesis and/or angiogenesis.

Isolated lymphatic endothelial cells transduce growth, survival and migratory signals via the VEGF-C/D receptor VEGFR-3

Vascular endothelial growth factor receptor-3 (VEGFR-3/Flt4) binds two known members of the VEGF ligand family, VEGF-C and VEGF-D, and has a critical function in the remodelling of the primary capillary vasculature of midgestation embryos. Later during development, VEGFR-3 regulates the growth and maintenance of the lymphatic vessels. In the present study, we have isolated and cultured stable lineages of blood vascular and lymphatic endothelial cells from human primary microvascular endothelium by using antibodies against the extracellular domain of VEGFR-3. We show that VEGFR-3 stimulation alone protects the lymphatic endothelial cells from serum deprivation-induced apoptosis and induces their growth and migration. At least some of these signals are transduced via a protein kinase C-dependent activation of the p42/p44 MAPK signalling cascade and via a wortmannin-sensitive induction of Akt phosphorylation. These results define the critical role of VEGF-C/VEGFR-3 signalling in the growth and survival of lymphatic endothelial cells. The culture of isolated lymphatic endothelial cells should now allow further studies of the molecular properties of these cells.

Intercellular adhesion molecule-1 in extravasation of normal mononuclear and leukaemia cells

Interaction of intercellular adhesion molecules (ICAMs) with their receptors has a key role in normal leucocyte adhesion and migration, whereas in leukaemia this has not been well established. In this study, we have evaluated the roles of different adhesion molecules in normal and leukaemia cell extravasation in a novel organotypic model for vessel wall and measured plasma ICAM-1 and -2 levels in acute leukaemia patients at diagnosis and during chemotherapy. We found that both normal mononuclear cells and blast cells from acute leukaemia patients, as well as retinoic acid-treated promyelocytic leukaemia cells, rapidly extravasated through endothelial cell layers into the underlying collagen matrix. ICAM-1 antibody prevented the extravasation, while antibodies to other adhesion molecules showed little (CD18, ICAM-2) or no inhibition (CD11a and ICAM-3). Soluble ICAM-1 (sICAM-1) protein had no effect. We also observed increased plasma sICAM-1 and -2 levels in leukaemia patients and found that they correlated only weakly with the white blood cell count. No correlation was found between sICAM-1 or -2 levels and the response to therapy. Although elevated sICAM-2 levels decreased rapidly during chemotherapy, sICAM-1 levels did not. Because sICAM-1 protein had no effect on leukaemia cell extravasation in vitro, it is probable that the increased plasma sICAM-1 levels in leukaemia patients may not play a role in leukaemia cell infiltration. However, as we showed that ICAM-1 mediated leukaemia cell extravasation on the cell surface, it is possible that cellular ICAM-1 has an important role in disease progression.

Soluble urokinase receptor levels correlate with number of circulating tumor cells in acute myeloid leukemia and decrease rapidly during chemotherapy

The importance of plasminogen activation, mediated by urokinase (uPA) and its receptor (uPAR), is well established in many physiologica and pathological processes, such as in cell migration and tumor-cell invasion. Recently, additional functions have been described for uPA and uPAR, particularly in cell adhesion and chemotaxis. The amounts of uPA and uPAR in various tumor types and in the plasma/serum samples of cancer patients have been shown to correlate with survival prognosis, indicating the relevance of these molecules in malignancy. We previously showed that in acute myeloid leukemia, a high level of plasma soluble uPAR (suPAR) at diagnosis correlates with poor response to chemotherapy. However, in this case, as in other cancers, the origin of suPAR is unknown. Therefore, we have now analyzed uPAR in cells, plasma, and urine of patients with acute leukemia (n = 35) at 0, 5, 14, 28, and 56 days after start of chemotherapy. In response to cytotoxic treatment, suPAR levels decreased rapidly, and the decreasing plasma suPAR (p-suPAR levels correlated highly with decreasing numbers of circulating tumor cells, suggesting that the elevated p-suPAR was produced by circulating tumor cells. Moreover, the p-suPAR level appeared to correlate with the amount of uPAR in tumor cell lysates at diagnosis. Our results also show for the first time that in lysates of circulating tumor cells, studied by immunoprecipitation and immunoblotting, uPAR was partly in fragmented form, whereas only full-length uPAR was found in normal leukocytes. We also detected fragmented suPAR in peripheral blood plasma, in urine, and especially in the plasma compartment of bone-marrow aspirates of acute myeloid leukemia patients, in a pattern differing considerably from that found in healthy individuals. Because proteolytic cleavage of uPAR induces a potent chemotactic response in vitro, it is possible that these fragments may play a role in the pathophysiology of acute leukemia.