Acknowledgements
This study was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science, the Takeda Science Foundation, an International Myeloma Foundation Japan Grant, and the Japan Leukemia Research Fund.
Potential conflict of interest
Disclosure forms provided by the authors are available with the full text of this article at http://dx.doi.org/10.3109/10428194.2015.1126589