Somatic mutations of calreticulin in myeloproliferative neoplasms

Thorsten Klampfl, Heinz Gisslinger, Ashot S. Harutyunyan, Harini Nivarthi, Elisa Rumi, Jelena D. Milosevic, Nicole C C Them, Tiina Berg, Bettina Gisslinger, Daniela Pietra, Doris Chen, Gregory I. Vladimer, Klaudia Bagienski, Chiara Milanesi, Ilaria Carola Casetti, Emanuela Sant'Antonio, Virginia Ferretti, Chiara Elena, Fiorella Schischlik, Ciara ClearyMelanie Six, Martin Schalling, Andreas Schon̈egger, Christoph Bock, Luca Malcovati, Cristiana Pascutto, Giulio Superti-Furga, Mario Cazzola, Robert Kralovics

Research output: Contribution to journalArticlepeer-review


BACKGROUND: Approximately 50 to 60% of patients with essential thrombocythemia or primary myelofibrosis carry a mutation in the Janus kinase 2 gene (JAK2), and an additional 5 to 10% have activating mutations in the thrombopoietin receptor gene (MPL). So far, no specific molecular marker has been identified in the remaining 30 to 45% of patients. METHODS: We performed whole-exome sequencing to identify somatically acquired mutations in six patients who had primary myelofibrosis without mutations in JAK2 or MPL. Resequencing of CALR, encoding calreticulin, was then performed in cohorts of patients with myeloid neoplasms. RESULTS: Somatic insertions or deletions in exon 9 of CALR were detected in all patients who underwent whole-exome sequencing. Resequencing in 1107 samples from patients with myeloproliferative neoplasms showed that CALR mutations were absent in polycythemia vera. In essential thrombocythemia and primary myelofibrosis, CALR mutations and JAK2 and MPL mutations were mutually exclusive. Among patients with essential thrombocythemia or primary myelofibrosis with nonmutated JAK2 or MPL, CALR mutations were detected in 67% of those with essential thrombocythemia and 88% of those with primary myelofibrosis. A total of 36 types of insertions or deletions were identified that all cause a frameshift to the same alternative reading frame and generate a novel C-terminal peptide in the mutant calreticulin. Overexpression of the most frequent CALR deletion caused cytokine-independent growth in vitro owing to the activation of signal transducer and activator of transcription 5 (STAT5) by means of an unknown mechanism. Patients with mutated CALR had a lower risk of thrombosis and longer overall survival than patients with mutated JAK2. CONCLUSIONS: Most patients with essential thrombocythemia or primary myelofibrosis that was not associated with a JAK2 or MPL alteration carried a somatic mutation in CALR. The clinical course in these patients was more indolent than that in patients with the JAK2 V617F mutation. (Funded by the MPN Research Foundation and Associazione Italiana per la Ricerca sul Cancro.)

Original languageEnglish
Pages (from-to)2379-2390
Number of pages12
JournalNew England Journal of Medicine
Issue number25
Publication statusPublished - 2013

ASJC Scopus subject areas

  • Medicine(all)


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