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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 receptor-associated 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 , NF-κB p65 phosphorylation, and NF-κB nuclear staining,

TIRAP: TIR domain containing adaptor protien

IRAK: IL-1 receptor- associated kinase

TRAF6: TNF receptor-associated 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 WMgain-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 expressionaccording to MYD mutation status

Inhibition of MYD88 signaling induced cytotoxicity and inhibited cell growth in cells expressing MYD88 L265P mutation

cytotoxicity

inhibited cell growth

MYD88mut cell line

induced apoptosis

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¨ommacroglobulinemia/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 2256-2257.

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.