Fabrizia Urbinati*
Research Fellow, Hematology/Oncology, Childrens Hospital Los Angeles, Mail Stop 54, 4650 Sunset Boulevard, Los Angeles, CA 90027, USA. Tel: +1 323 669 2525; Fax: +1 323 913 3087; E-mail: furbinati@chla.usc.edu

Catherine Madigan*
Clinical Fellow, Hematology/Oncology, Childrens Hospital Los Angeles, Mail Stop 54, 4650 Sunset Boulevard, Los Angeles, CA 90027, USA. Tel: +1 323 669 2525; Fax: +1 323 913 3087; E-mail: cmadigan@chla.usc.edu 

Punam Malik (corresponding author)
Associate Professor of Pediatrics and Pathology, Keck School of Medicine, University of Southern California; Attending Physician, Hematology-Oncology, Childrens Hospital Los Angeles, Mail Stop 54, 4650 Sunset Boulevard, Los Angeles, CA 90027, USA. Tel: +1 323 669 5438; Fax: +1 323 913 3087; E-mail: pmalik@chla.usc.edu

*These authors contributed equally to this work.