Original Article

The calreticulin (CALR) exon 9 mutations are promising targets for cancer immune therapy

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Abstract

The calreticulin (CALR) exon 9 mutations are found in 30% of patients with essential thrombocythemia and primary myelofibrosis. Recently, we reported spontaneous immune responses against the CALR mutations. Here, we describe that CALR-mutant (CALRmut)-specific T cells are able to specifically recognize CALRmut cells. First, we established a T-cell culture specific for a CALRmut epitope. These specific T cells were able to recognize several epitopes in the CALRmut C terminus. Next, we established a CALRmut-specific CD4+ T-cell clone by limiting dilution. These CD4+ T cells recognized autologous CALRmut monocytes and hematopoietic stem cells, and T-cell recognition of target cells was dependent on the presence of CALR. Furthermore, we showed that the CALRmut response was human leukocyte antigen (HLA)-DR restricted. Finally, we demonstrated that the CALRmut-specific CD4+ T cells, despite their phenotype, were cytotoxic to autologous CALRmut cells, and that the cytotoxicity was mediated by degranulation of the T cells. In conclusion, the CALR exon 9 mutations are targets for specific T cells and thus are promising targets for cancer immune therapy such as peptide vaccination in patients harboring CALR exon 9 mutations.

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Acknowledgements

We thank laboratory technician Merete Jonassen for outstanding help in teaching MOH to perform the immune cell assays and Tina Seremet for help with the analysis of T-cell receptors. We also thank the secretaries, nurses and laboratory technicians at University Hospital Zealand for organizing blood draws from patients. This study was supported in part by grant from Danish Cancer Society to HCH (Grant Number R90-A6143-14-S2) and by grants from Region Sjællands Sundhedsvidenskabelige Forskningsfond to MOH (Grant Numbers 12-000095 and 15-000342) in addition to support from Herlev Hospital.

Author information

Affiliations

  1. Department of Hematology, Zealand University Hospital, Roskilde, Denmark

    • M O Holmström
    • , L Kjær
    •  & H C Hasselbalch
  2. Center for Cancer Immune Therapy, Department of Hematology, Copenhagen University Hospital at Herlev, Herlev, Denmark

    • M O Holmström
    • , E Martinenaite
    • , S M Ahmad
    • , Ö Met
    • , C Friese
    • , P thor Straten
    • , I M Svane
    •  & M H Andersen
  3. Department of Oncology, Copenhagen University Hospital at Herlev, Herlev, Denmark

    • Ö Met
    •  & I M Svane
  4. Department of Hematology, Rigshospitalet, Copenhagen, Denmark

    • C H Riley
  5. Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark

    • P thor Straten
    •  & M H Andersen

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Competing interests

The authors declare no conflict of interest. However, it should be noted that Morten Orebo Holmström, Hans Carl Hasselbalch and Mads Hald Andersen have filed a patent regarding the CALR exon 9 mutations as a target for cancer immune therapy. The patent has been transferred to University Hospital Zealand, Zealand Region, and Copenhagen University Hospital at Herlev, Capital Region, according to Danish Law concerning inventions made at public research institutions.

Corresponding author

Correspondence to M H Andersen.

Supplementary information

Supplementary Information accompanies this paper on the Leukemia website (http://www.nature.com/leu)