Oops, you're using an old version of your browser so some of the features on this page may not be displaying properly.

MINIMAL Requirements: Google Chrome 24+Mozilla Firefox 20+Internet Explorer 11Opera 15–18Apple Safari 7SeaMonkey 2.15-2.23

Poster display session

4585 - CALR mutations and their link with cellular calcium during megakaryocyte hyperplasia in MPNs


11 Sep 2017


Poster display session


Cancer Biology


Maria Morlan Mairal


Annals of Oncology (2017) 28 (suppl_5): v1-v21. 10.1093/annonc/mdx361


M. Morlan Mairal1, P. Papadopoulos2, J. Hetmanski3, P.T. Caswell3, M. Krstic-Demonacos1, A. Aziz1

Author affiliations

  • 1 Environment And Life Sciences, University of Salford, M5 4WT - Salford/GB
  • 2 Dept Of Hematology, Hospital Clinico San Carlos, 28040 - Madrid/ES
  • 3 Wellcome Trust Centre For Cell-matrix Research, University of Manchester, M13 9PT - Manchester/GB


Abstract 4585


Megakaryocyte hyperplasia is a major characteristic of two myeloproliferative neoplasms (MPNs) known as essential thrombocythemia (ET) and Primary myelofibrosis (PMF). About 35% of ET and PMF patients harbour somatic calreticulin (CALR) mutations. CALR is a calcium (Ca2+) buffering protein within the endoplasmic reticulum (ER). Ca2+ is an important element for megakaryocyte functions; however the impact of CALR mutations in cellular Ca2+ during megakaryocyte hyperplasia remains elusive.


I-TASSER software was used to study the aminoacid charge using the 3D structure of CALR mutant. Marimo cells and overexpressing CALR mutant HEK293T and DAMI cells were used as cellular models. CALR cellular localization was addressed by flow cytometry and confocal microscopy. Basal Ca2+ levels were measured by Fluo-8 staining. Furthermore cells were treated with Fendiline and BTP-2 calcium channel blockers to manipulate cellular Ca2+.


The present study shows that CALR mutations change the aminoacid charge of the Ca2+ binding region of CALR and that mutant CALR is localized outside the ER, within the cytoplasm and the cellular membrane. These results suggest that CALR mutations could be affecting the Ca2+ buffering activity within the ER. Therefore, we further analysed Ca2+ basal levels in CALR mutant cells, and our results showed that CALR mutations show lower cellular Ca2+levels. These results lead us to think that low intracellular Ca2+ levels could be the driving force of megakaryocyte hyperplasia characteristic of ET and PMF. Therefore, we induced low intracellular Ca2+ levels in leukemic blast by using Ca2+ channel blockers and our results showed that treated cells display an increase of the megakaryocyte marker CD41a in the cell surface, suggesting an induction of megakaryopoiesis in these cells.


These findings elucidate that low intracellular Ca2+ caused by CALR mutations could be the driving force of megakaryocyte formation in ET and PMF. This study shows the relevance to understand the role of cellular calcium during megakaryocyte formation and this could unravel the pathogeny of CALR mutant in MPNs.

Clinical trial identification

Legal entity responsible for the study

University of Salford


University of Salford


All authors have declared no conflicts of interest.

This site uses cookies. Some of these cookies are essential, while others help us improve your experience by providing insights into how the site is being used.

For more detailed information on the cookies we use, please check our Privacy Policy.

Customise settings
  • Necessary cookies enable core functionality. The website cannot function properly without these cookies, and you can only disable them by changing your browser preferences.