Abstract

Abstract 2900

Poster Board II-876

Ph-negative myeloproliferative neoplasms: polycythemia vera (PV), essential thrombocythemia (ET) and primitive myelofibrosis (PMF) carry an acquired somatic mutation JAK2V617F in 95% (PV), and in 50 to 60% (ET or PMF) of the patients. Mutations of the TET2 gene have been observed with roughly similar frequencies in the three MPN, irrespective of the presence of JAK2V617F. Evolution to myelofibrosis or acute leukemia may occur with time in MPN patients. Although its molecular bases are poorly understood, the evolution is likely due to the acquisition of additional mutations.

To investigate whether cytogenetic abnormalities are distributed differently according to type of transformation and to the JAK2 and TET2 statuses, the Groupe Francophone de Cytogénétique Hématologique has collected 82 patients with transformation of MPN.

There were 66 (80%) acute myeloid leukemia or myelodysplastic syndromes (AML/MDS) and 16 (20%) myelofibroses (MF). Of note pipobroman (Pi) treatment seems to be associated with MF, and hydroxyuera (Hu) with AML/MDS evolution in our series. Statistical analyses of clinical, cytogenetic and molecular data are shown Table 1.

On the cytogenetical point of view, several points are noteworthy.

Some abnormalities were unevenly distributed: there were significantly more -7/del7q and -5/del5q in AML/MDS and tri1q and tri9 in MF. MF and PMF cytogenetic profile looked similar, suggesting a potential link between cytogenetic markers and the phenotype.

Although the derivative chromosome der(1;7), observed in 9 patients, is responsible for a loss of 7q, it seemed different from patients with -7/del7q [excluding der(1;7)]. In the -7/del7q group, AML/MDS patients were more numerous than MF patients and the overall survival was shorter compared with the der(1;7) group (22/22 (100%) vs 6/9 (67%) AML/MDS, p=0.02; median: 4 vs 41 months, p=0.0007 respectively).

Some specific associations could be observed, such as 17p deletions with 5q deletion (12/30, 40% vs 4/48, 8%, p=0.0007) and 20q deletion with der(1;7) (4/9 (44%) vs11/69 (16%), p=0.03).

We detected 24/40 (60%) JAK2V617F and 8/25 (32%) TET2 mutations in transformed MPN, with all possible combinations between the wildtype and mutated forms of both genes. For one post-ET AML patient, JAK2V617F had been observed in a fraction of the granulocytes at the chronic phase. Analysis of blood cDNA obtained at chronic phase showed the same TET2 mutation as observed at acute phase. Because the blast cells were JAK2wt-TET2mut and carried a t(10;16)(q22;q23) affecting the CBFB gene, it is likely that the resulting non-MYH11 CBFB fusion gene transformed a JAK2wt-TET2 mutated progenitor that predominated in the chronic phase.

In conclusion, no specific chromosomal abnormality was associated with TET2 or JAK2 mutations. Chromosomal abnormalities were associated with a type of transformation (AML/MDS or MF), suggesting a specific role in the process. In addition, association between some chromosomal abnormalities suggest a specific oncogenic cooperation.

Table 1.
n=82 AML/MDS n=66  MF n=16  p univariate  p multivariate  
Sex F 39 (59%) 5 (31%) ns ns 
PV/ET/PMF 30/26/10 13/3/0 ns ns 
Age at diagnosis of MPN 54 [20-82] 55.5 [31-69] ns ns 
Chronic Phase (duration, years) 12 [2-34] 14.5 [3-28] ns ns 
Prior treatments (n=73*57* 16 
No treatment (n=6) ns ns 
One treatment (n=40) 33 (58%) 7 (44%) ns ns 
Treatments with Hu (n=57) 48 (73%) 9 (56%) 0.03  
Treatments with Pi (n=41) 26 (46%) 15 (93%) 0.0006 0.05 
Age at transformation 66.5[37-92] 68 [45-80] ns ns 
Abnormal karyotype 62 (94%) 16 (100%) ns ns 
Complex karyotype 45 (68%) 7 (44%) ns ns 
-7/del7q 28 (42%) 3 (18%) 0.07 ns 
-7/del7q[without der(1;7)] 22 (33%) 0.004 0.04 
-5/del5q 28 (42%) 2 (12%) 0.03 ns 
-13/del13q 5 (8%) 3 (19%) ns ns 
-20/del20q 11 (17%) 4 (25%) ns ns 
-17/del17p 15 (23%) 1(6%) ns ns 
+1q 14 (22%) 9 (56%) 0.01 ns 
+9 5 (8%) 4 (25%) 0.04 ns 
+8 11 (17%) 3 (19%) ns ns 
dic 17 (26%) 3 (19%) ns ns 
der(1;7) 6 (9%) 3 (19%) ns ns 
Amplification MLL 0 (0%) ns ns  
JAK2mut 17/31 (55%) 7/9 (78%) ns ns 
TET2mut 6/19 (32%) 2/6 (33%) ns ns 
Median overall survival (months) 48 <0.0001 0.001 
n=82 AML/MDS n=66  MF n=16  p univariate  p multivariate  
Sex F 39 (59%) 5 (31%) ns ns 
PV/ET/PMF 30/26/10 13/3/0 ns ns 
Age at diagnosis of MPN 54 [20-82] 55.5 [31-69] ns ns 
Chronic Phase (duration, years) 12 [2-34] 14.5 [3-28] ns ns 
Prior treatments (n=73*57* 16 
No treatment (n=6) ns ns 
One treatment (n=40) 33 (58%) 7 (44%) ns ns 
Treatments with Hu (n=57) 48 (73%) 9 (56%) 0.03  
Treatments with Pi (n=41) 26 (46%) 15 (93%) 0.0006 0.05 
Age at transformation 66.5[37-92] 68 [45-80] ns ns 
Abnormal karyotype 62 (94%) 16 (100%) ns ns 
Complex karyotype 45 (68%) 7 (44%) ns ns 
-7/del7q 28 (42%) 3 (18%) 0.07 ns 
-7/del7q[without der(1;7)] 22 (33%) 0.004 0.04 
-5/del5q 28 (42%) 2 (12%) 0.03 ns 
-13/del13q 5 (8%) 3 (19%) ns ns 
-20/del20q 11 (17%) 4 (25%) ns ns 
-17/del17p 15 (23%) 1(6%) ns ns 
+1q 14 (22%) 9 (56%) 0.01 ns 
+9 5 (8%) 4 (25%) 0.04 ns 
+8 11 (17%) 3 (19%) ns ns 
dic 17 (26%) 3 (19%) ns ns 
der(1;7) 6 (9%) 3 (19%) ns ns 
Amplification MLL 0 (0%) ns ns  
JAK2mut 17/31 (55%) 7/9 (78%) ns ns 
TET2mut 6/19 (32%) 2/6 (33%) ns ns 
Median overall survival (months) 48 <0.0001 0.001 
*

treatment unknown for 3 patients

Disclosures:

No relevant conflicts of interest to declare.

Author notes

*

Asterisk with author names denotes non-ASH members.