H e m a t o lo g y E d u c a t io n - European Hematology Association

More documents

Recommendations

Info

pathologic induction of miR-28 in MPNs suggest that several mechanisms are operating in patients to reduce levels of TpoR. Negative signaling regulators: LNK, c-CBL, NF1, and SOCS proteins Cytokine signaling involves tight dependency on cytokine binding to cytokine receptor extracellular domains in order to induce activation of JAKs and downstream signaling via STATs, MAP-kinase, PI-3’kinase, and Akt. In the case of acute cytokine signaling, rapid induction of negative regulators, such as Suppressors of Cytokine Signaling (SOCS), Protein Inhibitors of STATs (PIAS), or activation of phosphatases and ubiquitin ligases concur to extinguish signaling. In the presence of mutated JAK2 or of mutated receptors, persistent signaling occurs, and it appears that these mechanisms are overwhelmed and cannot efficiently oppose continuous signaling. A minority of MPN patients harbor LNK mutations, 51 and LNK appears to be play an important role in MPNs, as its level of expression in the absence of mutations correlates with JAK2 V617F allele burden in MPN patients. 52 Coded by a gene on chromosome 12q24.12, SH2-B (SH2B1) together with APS (SH2B2) and LNK (SH2B3) form a family of signaling adaptors that regulate signaling by several cytokine and growth factor receptors, the JAK-STAT pathway, myelopoiesis, and lymphopoiesis. 53,54 Particularly LNK has been shown to down-modulate KIT receptor tyrosine kinase signaling, 55 Tpo, and Epo signaling 56,57 and to decrease JAK2 V617F or TpoR W515L signaling. 58 LNK also restrains the phenotype of JAK2 V617F-induced MPD. All family members share a domain structure represented by an NH2-terminus dimerization domain, and proline rich motifs, a pleckstrin homology domain, and SH2 domain and a C-terminus domain containing a conserved tyrosine residue. 53 LNK binds to JAK2 V617F stronger than to wild type JAK2 both via the SH2 domain and a site in its NH2-terminus. 52 This would indicate that either the conformation of JAK2 V617F is different than that of wild type JAK2, or that constitutive signaling promotes LNK-JAK2 V617F complex formation. Without crystal structures of the full-length and mutated JAK2, it would be very difficult to understand the exact basis for this difference. Interestingly, in patients with MPNs, the levels of LNK expression correlated with the JAK2 V617F allele burden and LNK suppresses signaling by JAK2 V617F. 52 It is tempting to speculate that LNK exerts a negative pressure in signaling by constitutive active JAK-STAT, and that the extent of negative regulation and the mechanisms invoked to select against this pressure might be important for driving the precise phenotype of MPN in patients. Two different LNK mutations were reported in JAK2 V617F-negative patients: one is a truncation and the other a missense mutation (E208Q) in the pleckstrin homology domain. 51 Other LNK mutations have been detected in JAK2 V617F-negative erythrocytosis 60 and leukemic transformation of MPN, with a higher frequency of 13%. 61 London, United Kingdom, June 9-12, 2011 CBL (Casitas B-cell lymphoma) proteins are ubiquitin ligases with major regulatory roles in receptor tyrosine kinase traffic and signaling termination. 62,63 c-CBL was also suggested to contribute to ubiquitinylation of TpoR cytosolic lysines. 64 c-CBL knock-out and double CBL and CBL-b deficient mice exhibit mild and severe MPN phenotypes, respectively. 65 c-CBL mutations have been reported in a low percentage of PMF (6%), 66 and in certain cases, c-CBL mutations are acquired during progression to leukemia. 66,67 A high resolution 250K Single Nucleotide Polymorphism (SNP) array study on 151 MPN patients revealed microdeletions in the region encompassing the tumor suppressor NF1 gene (Neurofibromatosis 1) in two secondary myelofibrosis patients. 68 In one patient, the second allele was also mutated leading to bi-allelic loss of NF1. 68 NF1 is a well established negative regulator of ras signaling, and its inactivation leads to a progressive myeloproliferative disorder in mice. 69 Although not clear at this moment whether NF1 would play a specific role in MPNs, the presence of microdeletions in a substantial number of myelofibrosis patients68 suggests that with highly sensitive genomics techniques, more alterations will be identified in the future. SOCS proteins are negative regulators of JAK-STAT proteins due to their ability to bind to, inhibit, and target for ubiquitinylation JAK proteins. SOCS3 is recruited to certain cytokine receptors, such as EpoR and G-CSFR, via binding of their SH2 domains to phosphorylated receptor tyrosine residues, which triggers ubiquitinylation of receptor (for G-CSFR) lysine residues and lysosomal degradation, with an overall decrease in signaling. 70- 72 73 Signaling by TpoR is down-modulated by SOCS1, while SOCS3 could inhibit Tpo-induced megakaryocte colony growth, but not constitutive megakaryocyte growth in patient megakaryocytes. 74 Hypermethylation of promoter CpG islands and decreased expression of SOCS1 or SOCS3 have been reported in a minority of MPN patients. 75,76 Biochemically, it was shown that SOCS3 can inhibit JAK2 V617F signaling in an inducible 293 cell system. 77 In contrast, in transformed Ba/F3 EpoR JAK2 V617F or JAK2 K539L cells, where levels of expression of JAK2 mutants are higher, SOCS3 was unable to exert inhibitory functions, due to hyperphosphorylation of the SOCS3 SOCS box. 78,79 Whether the escape of cells from SOCS3 inhibition represents a qualitative difference or simply a quantitative issue due to persistent signaling, remains to be determined, but the fact is that the majority of MPN patients exhibit phenotype although SOCS3 is induced, and its phosphorylation can be a biomarker of overactive JAK2. 79 Furthermore, SOCS2 was shown to inhibit JAK2 V617F signaling, and its promoter is hypermethylated in some MPN. 80 Given that SOCS2 enhances degradation of SOCS3, 81 the picture might become more complex. Stem cells in MPNs and the molecular basis of phenotype specificity The key to understanding the pathogenesis of MPNs relies on the study of the mutated and non-mutated HSCs. The reasons for this are: i) HSC is the cell type where mutations like JAK2 V617F appear to be acquired; Hematology Education: the education programme for the annual congress of the European Hematology Association | 2011; 5(1) | 249 |
16 th Congress of the European Hematology Association ii) non-mutated and mutated HSCs coexist in the marrow of PV and ET patients, 82,83 but they are somehow inhibited, allowing clonal dominance of the mutated HSCs, possibly via the action of Tumor Necrosis Factorα (TNF-α); 84,85 iii) in myelofibrosis, almost all HSCs belong to the mutated clone; 83 iv) xenotransplantation experiments with human JAK2 V617F-positive HSCs into immunocompromised mice and human bone marrow transplantation with JAK2 V617F-positive HSCs do not support a proliferative advantage for the mutated HSCs. 83,86 Similarly, in a knock-in JAK2 V617F model, apparently JAK2 V617F places HSCs at a disadvantage for blood reconstitution. 87 One yet unexplored scenario is that the MPN mutations can be acquired in different HSC subsets, 88 and that might influence disease latency and phenotype. For example, the recently described ‘myeloid biased’ subset 89 that increases with age and that is stimulated by TGF-β1 could be specifically targeted by mutations in myelofibrosis, 90 especially since TGF-β1 was already suggested to play a major role in myelofibrosis. 91 Several hypotheses can be invoked to attempt to answer the central question of why one acquired mutation, JAK2 V617F, can induce three different diseases: i) gene dosage determines phenotype, as shown in transgenic mouse models 92 and in certain retroviral transduction models. 93 Although very attractive, the model of ET, PV, and PMF being induced by increasing JAK2 V617F kinase activity is not always seen in mouse models, where an erythrocytosis phenotype followed eventually by myelofibrosis is prevalent. 87,92–97 ii) individual SNP variations would favor a specific phenotype, for example, by favoring the interaction of JAK2 V617F with one of the three receptors: EpoR, TpoR, and G-CSFR. 98 iii) the TpoR might be specifically involved in inducing myelofibrosis since TpoR mutants induce rapid and severe MPNs with myelofibrosis in mice 32,35 and since strong megakaryocyte proliferation was reported to trigger myelofibrosis. 91,99–102 iv) depending on which type of HSC (myeloid-biased, lymphoid biased, or balanced) 90 acquires JAK2 V617F, a different phenotype would emerge. v) the recent discovery of mutations in genes, such as TET2 103–105 and several others, which give a clonal advantage to HSCs, makes it possible that acquisition of JAK2 V617F might give a different phenotype depending on pre-existent or subsequent mutations. Other factors must certainly exist that explain the phenotype specificity. Recently, JAK2 V617F-positive individual patient Burst Forming Unit erythroid (BFU-E) colonies maintained in 0.01 U/ml Epo were compared between ET and PV patients with respect to in vitro gene expression profiles. 106 BFU-E colonies derived from ET patients expressed IFNg- induced genes, due to constitutive activation of STAT1. 106 This was not the case for BFU- E colonies from PV patients, although the JAK2 V617F allele burdens were similar. The basis for this signaling difference via STAT1 remains to be identified. Expression of an activated form of STAT1 in normal CD34-positive progenitors induced an ET-like phenotype, whereas down-regulation of STAT1 activity in JAK2 V617F-heterozygous ET progenitors induced PVlike phenotype. 106 These studies demonstrated a key role for STAT1 signaling in preventing erythroid differentiation and favoring megakaryocyte differentiation. 106 Signaling towards leukemic transformation Exactly how chronic phase MPNs transform into acute myeloid leukemia (AML) remains unknown. While only 5–8% of ET and PV transform to AML, a larger proportion of PMF or of secondary MF (~18%) evolves to AML. 107,108 Genetic instability was reported in cells expressing JAK2 V617F, 109 and might contribute to leukemic transformation, although this remains rare in PV patients. The gene coding for the p53 protein, TP53, is not mutated in the chronic phase of MPNs, possibly because cytokine receptor signaling inactivates p53 functionally (Vainchenker et al., 2011 personal communication). In contrast, p53 mutations are acquired in 20% of post-MPN AML patients, 67,110 suggesting that loss of p53 might play an important role in leukemic transformation. Heterozygous mutations of IDH1/2 (isocitrate dehydrogenase 1 and 2) are acquired to an extent of 21.6% in the blast crisis, while during the chronic phase IDH mutations are quite low. 111 The same is true for the deletion of the IKZF gene, coding for the Ikaros transcription factor, 112 and for mutations in the gene (RUNX1) that codes for the AML transcription factor, where mutations were found in 6/16 AML patients evolving from MPNs. 67 Since mutations or deletion of p53, IDH1/2, Ikaros, and AML1 are known to be associated with a substantial fraction of de novo AML, 113–116 it appears that these alterations could be common in AML and post-MPN AML, and might not be directly linked to the constitutive JAK-STAT signaling in MPNs, other than the latter predisposing for genetic instability and selection of a program and promotes blast transformation. Chromatin effects of constitutive JAK-STAT signaling Expression of JAK2 V617F or of mutated TpoR leads to constitutive STAT5 and STAT3 signaling, and also constitutive activation of MAP-kinase Erk1,2, PI-3’-kinase, and Akt. In Drosophila melanogaster, constitutive signaling induced by an overactivated JAK (JAK-D) leads to induction of common, but also to different genes from those normally targeted by D. melanogaster STAT (STAT92E). 117 Constitutive JAK signaling was found to disrupt heterochromatin gene silencing by derepressing genes not normally targeted by STATs. 117 On the other hand, nonphosphorylated STAT92E was shown to play a role in establishing the heterochromatin state, in association with heterochromatin protein 1 (HP1). 118 Whether this holds true for the mammalian system is not known, but several lines of evidence point towards a link between constitutive JAK-STAT signaling and global regulation of chromatin. First, JAK2 was shown to directly phosphorylate tyrosine 41 of histone H3, and by this to inhibit binding of the chromoshadow domain of HP1 alpha to histone H3. 119 These data uncovered a novel function for JAK2 in directly regulating heterochromatin, 119 although such regulation might also occur indirectly via activated | 250 | Hematology Education: the education programme for the annual congress of the European Hematology Association | 2011; 5(1)
Page 1 and 2:
H e m a t o l o g y E d u c a t i o
Page 3 and 4:
Copyright Information ©2011 by Eur
Page 5 and 6:
Editorial Board Education Book Edit
Page 7 and 8:
Acute lymphoblastic leukemia 1-8 Th
Page 10 and 11:
S. Schnell P. Van Vlierberghe A. Fe
Page 12 and 13:
lineage cells, and in differentiati
Page 14 and 15:
FLT3 mutations The FMS-like tyrosin
Page 16 and 17:
44. Bar-Eli M, Ahuja H, Foti A, Cli
Page 18 and 19:
J.M. Rowe 1,2 C. Ganzel 1 1 Shaare
Page 20 and 21:
treated on the MRC UKALL XII/ECOG29
Page 22 and 23:
asparaginase (PEG), where the Esche
Page 24 and 25:
or higher. It is, however, importan
Page 26 and 27:
25. Bruggemann M, Schrauder A, Raff
Page 28 and 29:
lymphoblastic leukemia: prospective
Page 30 and 31:
such as high white blood cell count
Page 32 and 33:
doxorubicine, there was a trend tow
Page 34 and 35:
of the aging process with respect t
Page 36 and 37:
K.L. Rice 1 M. Buzzai 2 J. Altman 1
Page 38 and 39:
ing FLT3-ITD, wild-type NPM1, or bo
Page 40 and 41:
ciated with gene activation, via th
Page 42 and 43:
leukemia with inv(16) and t(8;21):
Page 44 and 45:
99. Parsons DW, Jones S, Zhang X, e
Page 46 and 47:
abnormalities, some of which are al
Page 48 and 49:
file. 27,31 Thus, the double gene-m
Page 50 and 51:
karyotype represents a distinct gen
Page 52 and 53:
Table 1. Meta-analysis of 23 random
Page 54 and 55:
A recent study by the Center for In
Page 56 and 57:
Patients with HLA-matched related o
Page 58 and 59:
After allogeneic HSCT, an autologou
Page 60 and 61:
A. Bacigalupo Ospedale San Martino,
Page 62 and 63:
Table 2. The effect of HLA mismatch
Page 64 and 65:
References 1. Petersdorf EW, Malkki
Page 66 and 67:
neutrophil and platelet recovery an
Page 68 and 69:
Figure 2. One Year-Overall Survival
Page 70 and 71:
infused on day 21. No serious adver
Page 72 and 73:
W, et al. Effect of graft source on
Page 74 and 75:
TRM was higher for patients who rec
Page 76 and 77:
following a myeloablative preparati
Page 78 and 79:
effect. Surprisingly, none of the p
Page 80 and 81:
nancies. Bone Marrow Transplant. 20
Page 82 and 83:
J.G. Gilles Center for Molecular an
Page 84 and 85:
14C12 was humanized by grafting VH
Page 86 and 87:
Table 1. VWD Classification. VWD Su
Page 88 and 89:
Figure 1. Missense mutations found
Page 90 and 91:
associated with an increased bleedi
Page 92 and 93:
49. Brown SA, Eldridge A, Collins P
Page 94 and 95:
leed. These issues are especially i
Page 96 and 97:
estored function. 43,44 A phase I t
Page 98 and 99:
years’ experience of prophylactic
Page 100 and 101:
J.A. Burger Department of Leukemia,
Page 102 and 103:
chemotaxis, migration across vascul
Page 104 and 105:
Regulatory T cells (T reg), identif
Page 106 and 107:
16. Burger JA, Ghia P, Rosenwald A,
Page 108 and 109:
TE, Nowakowski GS, et al. CD49d exp
Page 110 and 111:
andomized trial demonstrating impro
Page 112 and 113:
Conclusions Chemoimmunotherapy has
Page 114 and 115:
with multiple comorbidities (≥ 2)
Page 116 and 117:
ment was finished in all 100 patien
Page 118 and 119:
Table 2. Treatment recommendation f
Page 120 and 121:
34. Ferrajoli A. The combination of
Page 122 and 123:
to be the source of additional gene
Page 124 and 125:
potential to prevent LSCs from acce
Page 126 and 127:
ABL1 confirms that eradication of d
Page 128 and 129:
65. Fiskus W, Pranpat M, Balasis M,
Page 130 and 131:
alive after 10 years. 11 Hence, CCy
Page 132 and 133:
each arm). A minimal change in myel
Page 134 and 135:
Any discussion about the definition
Page 136 and 137:
H. Kantarjian J. Cortes Leukemia De
Page 138 and 139:
59%; the CCyR rate was 44%. Among p
Page 140 and 141:
ern era of BCR-ABL1 tyrosine kinase
Page 142 and 143:
the hematopoietic system, 10 nor in
Page 144 and 145:
over the period of 6 weeks, demonst
Page 146 and 147:
Data on clonal changes in the blood
Page 148 and 149:
2006 Feb 1;107(3):924-30. 41. Liang
Page 150 and 151:
demonstrated that changes in osteob
Page 152 and 153:
“Mafia” transgenic mice in whic
Page 154 and 155:
68. Coetzee T, Fujita N, Dupree J,
Page 156 and 157:
ization. In WASP deficiency, lympho
Page 158 and 159:
Currently the epistatic relationshi
Page 160 and 161:
R. Küppers Institute of Cell Biolo
Page 162 and 163:
Figure 1. TNFAIP3 mutation in HL ce
Page 164 and 165:
Figure 2. HRS cells and their precu
Page 166 and 167:
Hansmann ML, et al. Detection of cl
Page 168 and 169:
fying patients for whom different a
Page 170 and 171:
prognosis HL, whilst those with res
Page 172 and 173:
12. Noordijk EM, Carde P, Dupouy N,
Page 174 and 175:
A. Sureda Consultant in Haematology
Page 176 and 177:
Figure 1. Long-term outcome of pati
Page 178 and 179:
from a MRD and 18 from MUDs. All pa
Page 180 and 181:
Parker PM, Stein AS, et al. High-do
Page 182 and 183:
R. Stasi Department of Haematology,
Page 184 and 185:
common variants in the regulatory r
Page 186 and 187:
against the TPO receptor (cMpl). 61
Page 188 and 189:
W.B. Mitchell A.A. Miller J.B. Buss
Page 190 and 191:
platelet counts and/or bleeding. Th
Page 192 and 193:
Mpl. Cell. 1994;77(7):1117-24. 6. d
Page 194 and 195:
ity and mortality associated with t
Page 196 and 197:
to azathioprine, and is particularl
Page 198 and 199:
stemming from antibodies against PE
Page 200 and 201:
L. Pasqualucci Institute for Cancer
Page 202 and 203:
cation of molecularly distinct subg
Page 204 and 205:
of cases) 46 and amplifications of
Page 206 and 207:
gene alterations in B cell lymphoma
Page 208 and 209: W. Wilson National Cancer Institute
Page 210 and 211: clear distinction among the lymphom
Page 212 and 213: Treatment strategies in germinal ce
Page 214 and 215: in ABC DLBCL (Hernandez et al., 201
Page 216 and 217: DLBCL that mostly occurs in young p
Page 218 and 219: phoma. J Clin Oncol. 2005;23:5347-5
Page 220 and 221: Table 1. Diffuse Large B cell Lymph
Page 222 and 223: sion/relapse are similar to those i
Page 224 and 225: intensive therapy with curative int
Page 226 and 227: A. Karsan Genome Sciences Centre an
Page 228 and 229: Balanced translocations In contrast
Page 230 and 231: some arm 5q have also been implicat
Page 232 and 233: (H3K27) methyltransferase, and is a
Page 234 and 235: 38. Starczynowski DT, Morin R, McPh
Page 236 and 237: G. Garcia-Manero Department of Leuk
Page 238 and 239: trial evaluating different doses an
Page 240 and 241: acid. 62 The second was a large mul
Page 242 and 243: Borthakur G, et al. Cause of death
Page 244 and 245: P. Krishnamurthy 1 G.J. Mufti 1,2 1
Page 246 and 247: etween 1995 and 2005. 11 Five hundr
Page 248 and 249: London, United Kingdom, June 9-12,
Page 250 and 251: attainment of FDC post DLI. Interes
Page 252 and 253: myelodysplastic syndromes is associ
Page 254 and 255: ubiquitous chaperone that promotes
Page 256 and 257: was thought that they are linked to
Page 260 and 261: STATs. Second, levels of HP1 alpha
Page 262 and 263: 72. Irandoust MI, Aarts LH, Roovers
Page 264 and 265: A.M. Vannucchi Section of Hematolog
Page 266 and 267: 2,559 patients with a diagnosis of
Page 268 and 269: tant use of aspirin should be caref
Page 270 and 271: sions at this regard. Based on thes
Page 272 and 273: in bcr-abl-negative myeloproliferat
Page 274 and 275: Table 1. Prognostic scoring systems
Page 276 and 277: Figure 1. Current inhibitors of JAK
Page 278 and 279: Table 4. A risk-based approach to d
Page 280 and 281: the flexibility to be adjusted as t
Page 282 and 283: A. Vacca 1 D. Ribatti 2 1 Departmen
Page 284 and 285: neovessel building together with MM
Page 286 and 287: Mevastatin, a specific inhibitor of
Page 288 and 289: egression of tumor vessels, and app
Page 290 and 291: diagnosis does not require genetic
Page 292 and 293: Genetics prognostic tools should be
Page 294 and 295: sone induction improves outcome of
Page 296 and 297: Table 1. Conventional chemotherapy
Page 298 and 299: Novel agents given as consolidation
Page 300 and 301: dence of peripheral neuropathy, gas
Page 302 and 303: 31. Barlogie B, Tricot G, Anaissie
Page 304 and 305: Table 1. Major differences between
Page 306 and 307: first line therapy have shown survi
Page 308 and 309:
transplantation, 7,91 and generally
Page 310 and 311:
methylation characterizes juvenile
Page 312 and 313:
Table 1. Clinical signs of possible
Page 314 and 315:
Table 4. Distribution of CSF involv
Page 316 and 317:
ently results in a less than 5% cum
Page 318 and 319:
90. German-Austrian-Swiss ALL-BFM S
Page 320 and 321:
U. Nowak-Göttl 1 R. Junker 1 A. Kr
Page 322 and 323:
Based on the data obtained from the
Page 324 and 325:
59. Male C, Chait P, Ginsberg JS, e
Page 326 and 327:
Table 1. Characteristic features of
Page 328 and 329:
Table 2. Mutational spectrum of CDA
Page 330 and 331:
megarakaryoblastic leukemia (AMKL)
Page 332 and 333:
R.E. Ware Professor and Vice-Chairm
Page 334 and 335:
protein, cytokines, and soluble adh
Page 336 and 337:
example, improving blood viscosity
Page 338 and 339:
92(9):1266-7. 36. Bensinger TA, Gil
Page 340 and 341:
London, United Kingdom, June 9-12,
Page 342 and 343:
port have also been used. 5 Combina
Page 344 and 345:
Wingard JR, Young J-AH, Boeckh MJ.
Page 346 and 347:
K. Rezvani 1 J. Barrett 2 1 Haemato
Page 348 and 349:
include the childhood infectious il
Page 350 and 351:
Summary Patients undergoing hematop
Page 352 and 353:
Table 1. Key issues. In a retrospec
Page 354 and 355:
invasive method to assess iron over
Page 356 and 357:
stitution but even with optimal sub
Page 358 and 359:
T.M. Hackeng Department of Biochemi
Page 360 and 361:
and inhibits FVIIa, and that the se
Page 362 and 363:
Figure 4. Regulation of coagulation
Page 364 and 365:
T. Baglin Department of Haematology
Page 366 and 367:
Figure 1. Illustration of alternati
Page 368 and 369:
compared with 3.5% in patients with
Page 370 and 371:
49. Hron G, Kollars M, Binder BR, E
Page 372 and 373:
Women receiving vitamin K antagonis
Page 374 and 375:
molecular weight heparin as prophyl
Page 376 and 377:
eral morbidity and mortality. 17-21
Page 378 and 379:
the HOD construct. Furthermore, the
Page 380 and 381:
Goals of future murine studies incl
Page 382 and 383:
F. Noizat-Pirenne C. Tournamille Et
Page 384 and 385:
phenotype. 26 In 2010, we investiga
Page 386 and 387:
ody has been involved in DHTR. 37 T
Page 388 and 389:
antigen. Cases can be encountered d
Page 390 and 391:
S.R. Sloan Harvard Medical School &
Page 392 and 393:
We also analyzed patient databases
Page 394 and 395:
Index of authors Altman J. 27 Bacig
Page 396 and 397:
Cornelissen J. Affiliations to disc
Page 398 and 399:
GlaxoSmithKline (Research Support;
show all

H e m a t o lo g y E d u c a t io n - European Hematology Association

Create successful ePaper yourself

Delete template?

Save as template?