Contributions
Type: Publication Only
Background
The recent description of CALR mutations occurring in ET and MF greatly contributed to the diagnostic evaluation of ph- Myeloprolyferative Neoplasms (MPN). The CALR gene encodes the endoplasmic reticulum Ca2++-binding chaperone-Calreticulin. Exon 9 CALR somatic insertions and deletions have been reported and the most frequent variants are Type-1, 52-bp deletion (p.L367fs*46), and type-2, 5-bp TTGTC insertion (p.K385fs*47), representing about 80% of the cases. These mutations have also been reported as favorable prognostic factor on ET thrombosis-free patients, particularly the type-1.
Aims
To evaluate CALR, JAK2 and MPL mutations in a group of ET and MF patients and to correlate clinical and analytical data.
Methods
We actualized a retrospective analysis of 115 patients (pts) diagnosed MPN: 88 ET and 27 MF (according to WHO2008 criteria), with a mean follow-up time of 8 years (3 moths-31 years). JAK2V617F mutation was assessed by ASO-PCR and real-time quantitative PCR, mutations in exon 10 MPL and exon 9 CALR by PCR-sequencing in blood or bone marrow samples.
Results
In ET group (39males/49females), 59,1% (52) were JAK2 positive; 20,5% (18) CALR 4,5% (4) MPL and 15,9% (14) were negative for JAK2/CALR/MPL- “triple negative”. The CALR type-1 mutation was detected in 11/18, the type-2 in 6/18 and one patient harbored the p.K375Rfs*49 mutation. Comparing JAK2, CALR and triple negative pts, CALR had a male dominance and higher mean platelet (PLT) counts (p=0.02), JAK2 pts had higher hemoglobin (Hb) levels (p=0.04) and triple negative pts presented at younger age (p=0.002). Analyzing the CALR subgroups, there is a trend to an older age and a higher PLT count in type-2 mutation group and an incremental difference on PLT counts comparing to JAK2 (p<0.001). There were no differences in leukocyte (WBC), serum ferritin and erythropoietin levels. Regarding hematological response to cytoreduction we did not observe differences within CALR pts. Thrombosis occurred in 24/88 ET, 18 previously or at diagnosis; 21/52 JAK2: 2 of splanchnic veins both associated to prothrombotic factors (1 HTZ Factor V Leiden (FVL), 1 HTZ PRT20210G/A/FVL); 3/18 CALR all type-1 and 2 associated to prothrombotic factors FVL (1) and HTZ PRT20210G/A (1). One CALR (type-2) and 4 JAK2 pts progressed to MF, one of them to AML. Eleven patients deceased: 6 JAK2, 3 CALR (type-1) and 2 triple negative
The MF pts (15M/12F) were 55,6% (15) JAK2, 33,3% (9) CALR : 6/9 type-1, 3/9 type-2; 7,4% (2) MPL and 3,7%(1) triple negative. About 70% of JAK2 pts had an allelic burden >50%. We observed a higher WBC count in JAK2 compared to CALR (p=0.04) and no differences in Hb, PLT, serum ferritin and EPO values. Thrombosis occurred in 3 JAK and 1 CALR type-1. There were 3 deaths 2 JAK2 and 1 CALR type-1.
Summary
In this cohort of MPN, 58,2% (67/115) have JAK2V617F mutation, 23,5% (27/115) CALR and 5,2% (6/115) MPL. In 13,1% (15/115) we found no JAK2/MPL/CALR mutation. Exon 9 CALR mutations, the second most prevalent marker in ET pts, are associated to higher PLT counts and lower Hb levels comparing to JAK2. Comparing CALR subgroup, ET pts with type-1 mutations had more thrombotic events, most of them in association to prothrombothic factors while type-2 presented with higher PLT counts and only a type-2 pt progressed to MF. There were no differences in cytoreduction response. The impact of the different type of CALR mutations on natural history of ET and MF pts are not yet completely elucidated. Nevertheless, these mutations constitute a molecular marker of ph- NMP and offer an important tool in the diagnostic pathway ET and MF.
Session topic: Publication Only
Type: Publication Only
Background
The recent description of CALR mutations occurring in ET and MF greatly contributed to the diagnostic evaluation of ph- Myeloprolyferative Neoplasms (MPN). The CALR gene encodes the endoplasmic reticulum Ca2++-binding chaperone-Calreticulin. Exon 9 CALR somatic insertions and deletions have been reported and the most frequent variants are Type-1, 52-bp deletion (p.L367fs*46), and type-2, 5-bp TTGTC insertion (p.K385fs*47), representing about 80% of the cases. These mutations have also been reported as favorable prognostic factor on ET thrombosis-free patients, particularly the type-1.
Aims
To evaluate CALR, JAK2 and MPL mutations in a group of ET and MF patients and to correlate clinical and analytical data.
Methods
We actualized a retrospective analysis of 115 patients (pts) diagnosed MPN: 88 ET and 27 MF (according to WHO2008 criteria), with a mean follow-up time of 8 years (3 moths-31 years). JAK2V617F mutation was assessed by ASO-PCR and real-time quantitative PCR, mutations in exon 10 MPL and exon 9 CALR by PCR-sequencing in blood or bone marrow samples.
Results
In ET group (39males/49females), 59,1% (52) were JAK2 positive; 20,5% (18) CALR 4,5% (4) MPL and 15,9% (14) were negative for JAK2/CALR/MPL- “triple negative”. The CALR type-1 mutation was detected in 11/18, the type-2 in 6/18 and one patient harbored the p.K375Rfs*49 mutation. Comparing JAK2, CALR and triple negative pts, CALR had a male dominance and higher mean platelet (PLT) counts (p=0.02), JAK2 pts had higher hemoglobin (Hb) levels (p=0.04) and triple negative pts presented at younger age (p=0.002). Analyzing the CALR subgroups, there is a trend to an older age and a higher PLT count in type-2 mutation group and an incremental difference on PLT counts comparing to JAK2 (p<0.001). There were no differences in leukocyte (WBC), serum ferritin and erythropoietin levels. Regarding hematological response to cytoreduction we did not observe differences within CALR pts. Thrombosis occurred in 24/88 ET, 18 previously or at diagnosis; 21/52 JAK2: 2 of splanchnic veins both associated to prothrombotic factors (1 HTZ Factor V Leiden (FVL), 1 HTZ PRT20210G/A/FVL); 3/18 CALR all type-1 and 2 associated to prothrombotic factors FVL (1) and HTZ PRT20210G/A (1). One CALR (type-2) and 4 JAK2 pts progressed to MF, one of them to AML. Eleven patients deceased: 6 JAK2, 3 CALR (type-1) and 2 triple negative
The MF pts (15M/12F) were 55,6% (15) JAK2, 33,3% (9) CALR : 6/9 type-1, 3/9 type-2; 7,4% (2) MPL and 3,7%(1) triple negative. About 70% of JAK2 pts had an allelic burden >50%. We observed a higher WBC count in JAK2 compared to CALR (p=0.04) and no differences in Hb, PLT, serum ferritin and EPO values. Thrombosis occurred in 3 JAK and 1 CALR type-1. There were 3 deaths 2 JAK2 and 1 CALR type-1.
Summary
In this cohort of MPN, 58,2% (67/115) have JAK2V617F mutation, 23,5% (27/115) CALR and 5,2% (6/115) MPL. In 13,1% (15/115) we found no JAK2/MPL/CALR mutation. Exon 9 CALR mutations, the second most prevalent marker in ET pts, are associated to higher PLT counts and lower Hb levels comparing to JAK2. Comparing CALR subgroup, ET pts with type-1 mutations had more thrombotic events, most of them in association to prothrombothic factors while type-2 presented with higher PLT counts and only a type-2 pt progressed to MF. There were no differences in cytoreduction response. The impact of the different type of CALR mutations on natural history of ET and MF pts are not yet completely elucidated. Nevertheless, these mutations constitute a molecular marker of ph- NMP and offer an important tool in the diagnostic pathway ET and MF.
Session topic: Publication Only