MYD88 L265P mutation in Waldenstrom macroglobulinemia

Report
JOURNAL READING
20131021
住院總醫師 王智慧 報告
高志平醫師 指導
MYD88 is an adaptor protein through which
most of the Toll-like receptors (TLRs) and
receptors for IL-1 and IL-18 cytokines signal
 coordinates the assembly of a multisubunit
signaling complex, including IL-1 receptorassociated kinase (IRAK) 1 and IRAK4, and also
signals to JAK-STAT 3 signaling and to
activation pathways and transcription factors,
such as the NF-kB.

The genetics and pathogenesis of Waldenstrom
macroglobulinemia (WM), are not fully
understood
 A whole exome–sequencing study of 31 WM
patients suggested a high frequency of MYD88
L265P mutation in WM.
 aim to analyze MYD88 mutation in WM and to
characterize the clinical significance of this
genetic alteration in a cohort of 67 WM patients.

whole-genome sequencing of bone marrow LPL
cells in 30 patients with WM, validate by Sanger
sequencing
 a somatic variant (T→C) in LPL cells was
identified at position 38182641 at 3p22.2
 predicted an amino acid change (L265P) in
MYD88 triggers IRAK-mediated NF-κB
signaling
 27 of 30 (90%)

 Inhibition
of
MYD88 signaling
reduced IκBα , NFκB p65
phosphorylation,
and NF-κB nuclear
staining,
TIRAP: TIR domain
containing adaptor protien
IRAK: IL-1 receptorassociated kinase
TRAF6: TNF receptorassociated factor 6
TAK1: TGF ß-activated
kinase 1
TAB1, TAB2: TAK1 binding
protien
IKK: IκB kinase
Patients
67 patients (42 males, 25 females) diagnosed
with WM
 diagnosis criteria of WM were
 (1) a lymphoplasmacytic bone marrow (BM)
involvement;
 (2) any level of IgM paraprotein;
 (3) exclusion of other low-grade lymphomas
 No familial form of WM was included


5 MM, 9 CLL, 6 hairy cell leukemia, 23 follicular
lymphoma, 10 mantle cell lymphoma, 2 IgM
MGUS, 1 non-IgM lymphoplasmacytic lymphoma,
16 marginal zone lymphoma (MZL).
Methods
DNA sequencing of exon 5 of MYD88
 Single nucleotide polymorphism (SNP) array
analysis

Results
High frequency of MYD88 L265P
mutation in WM
Fifty-three (79%) patients harbor MYD88 L265P
mutation (MYDmut)
 MYD88 was an acquired mutation as no
aberration was identified in the mutational hot
spots of MYD88 in T lymphocytes isolated from
WM patients (n= 4).
 not observed any other mutation on exon 5 of
MYD88 in our cohort

absent in hairy cell leukemia, MM, mantle cell
lymphoma, and CLL
 MZL (1/16; 6%) , follicular lymphoma (1/23, 4%),
IgM-MGUS (1/2) , 1 case of non-IgM LPL.

Gain of chromosome 3 or acquired UPD, a new
mechanisms of alteration of MYD88 locus in
WM
LOH without copy number changes 
uniparental disomy (UPD).
 using SNP array (n =46).
 found UPD at the MYD88 locus in only 1 patient
(2%)  homozygous for L265P mutation in
tumoral cells
 not identified mechanisms of loss of MYD88,

UPD: 單親二體症 (個體一個
染色體對的二套基因僅由父或
母其中一方所提供)
observed a gain on chromosome 3 at the 3p22
locus (including MYD88 gene) in 7 of 59 (12%)
patients, including 2 (5%) patients with MYD88
mutation.
 gain on chromosome 3 more frequently in the
MYDwild group than in the MYDmut group (P
5 .006).
 other cytogenetic aberrations were associated
with the gain of chromosome 3 in 6 of 7 patients.


we identified alteration of the MYD88 locus in
91% of patients with WMgain-of-function
mutation (79%) or Copy number aberration (12%)
MYD88 mutation is related to NF-kB
abnormalities
Recent studies have described genomic deletions
of 2 potent regulators/inhibitors of the NF-kB
pathway in WM, TNFAIP3 (located on 6q23), and
deleted in lymphocytic leukemia 7 (located on
13q14)
 Overall, 63% of WM had at least 1 additional
genetic alteration in the NF-kB pathway in our
cohort, but no significant difference was observed
according to the MYD88 mutation status.

Clinical and biological features of WM
with MYDwild
21% MYDwild.
 MYD88 mutation was not associated with
deletion 6q, gain of 4, deletion 11q, deletion 17p,
or deletion 13q14 in our study
 not observe any difference in terms of survival
according to the MYD88 mutation status

MYDwild expressed CD27
We found that CD27 (positive in 49% of
malignant B cells from WM in our series) was
expressed in a significantly lower proportion in
the MYDmut group than in the MYDwild group,
30% and 92%, (P= .0001).
 CD27, a TNF-family member, is expressed on the
cell surface of memory B cells from which WM is
thought to derive
 a higher frequency of CD5 positive cases (positive
expression in 23% of WM in our series) (P = .043)
in MYDwild group

High expression of IL-6 was observed in WM
independently of MYD mutation status
no significant difference in IL-6 expression
according to MYD mutation status
Inhibition of MYD88 signaling induced
cytotoxicity and inhibited cell growth in cells
expressing MYD88 L265P mutation
cytotoxicity
inhibited cell growth
induced apoptosis
MYD88mut cell line
Discussion
confirmed a high frequency of MYD88 L265P
mutation in this study of 67 patients diagnosed
with WM,
 Treon and colleagues have described MYD88
L265P mutation in 90% of cases in a first series
of 46 patients with WM.
 Few clinical and biological data distinguished
MYDwild from MYDmut subgroups in our series

1. Poulain S, Roumier C, Decambron A, et al. MYD88 L265P mutation in Waldenstrom’s
macroglogulinemia. Blood. 2013;121(22):4504-4511.
2. Treon SP, Xu L, Yang G, et al. MYD88 L265P somatic mutation in Waldenstr¨om’s
macroglobulinemia. N Engl J Med. 2012;367(9):826-833.
3. Gachard N, Parrens M, Soubeyran I, et al. IGHV gene features and MYD88 L265P
mutation separate thethree marginal zone lymphoma entities and Waldenstr¨om
macroglobulinemia/lymphoplasmacytic lymphomas.
Leukemia. 2013;27(1):183-189.
4. Xu L, Hunter ZR, Yang G, et al. MYD88 L265P in Waldenstr¨om macroglobulinemia,
immunoglobulin M monoclonal gammopathy, and other B-cell lymphoproliferative
disorders using conventional and quantitative allele-specific polymerase chain reaction.
Blood. 2013;121(11):2051-2058.
5. Landgren O, Staudt L. MYD88 L265P somatic mutation in IgM
MGUS. N Engl J Med. 2012;367(23): 2255-2256, author reply 22562257.
6. Varettoni M, Arcaini L, Zibellini S, et al. Prevalence and clinical
significance of the MYD88 (L265P) somatic mutation in
Waldenstrom’s macroglobulinemia and related lymphoid neoplasms.
Blood. 2013;121(13): 2522-2528.
7. Jim´enez C, Sebasti´an E, Del Carmen Chill´on M, et al. MYD88
L265P is a marker highly characteristic of, but not restricted to,
Waldenstr¨om’s macroglobulinemia [published online ahead of print
March 22, 2013]. Leukemia.
8. Ansell SM, Secreto FJ, Manske M, et al. MYD88 pathway activation
in lymphoplasmacytic lymphoma drives tumor cell growth and
cytokine expression [abstract]. Blood. 2012;120(21):2699. Abstract
2699.
The high frequency of MYD88mutation in WM
highlights the TLR pathway as a new potential
pathogenic pathway in WM
 Our preliminary observations showed that
blocking of MYD88 signaling using an inhibitor of
MYD88 homodimerization induced cytotoxicity
and apoptosis, and reduced cell proliferation,
through decreased IRAK4 and STAT3
phosphorylation

MYD88 gene might undergo genetic alterations
through other mechanisms, such as UPD, or gain
of chromosome 3.
 additional genetic alterations targeting NF-kB
genes such as deletion of TNFAIP3, a negative
regulator of NF-kB pathway, were observed.


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