A New Xenograft Model for Studying Multiple Myeloma and Drug Response

Abstract 4073

While new treatment options are available, multiple myeloma (MM) still remains an incurable malignancy of plasma cells with a grim prognosis. Practical in vivo models to study human MM may enable a better understanding of the biology of the disease, and better optimization of therapeutic strategies. The best current xenograft model, the immune-deficient NOD/SCID mice, recapitulates MM in vivo, however, the price is very costly and maintenance complex, with >1 month required to establish engraftment. Our goal was to develop a user friendly rapid alternative xenograft system for the preclinical assessment of MM growth and therapy. We recently described this new in-vivo system for studying human leukemia in the pre-immune turkey embryo ^1,2. These embryos are inexpensive, require no maintenance, and are easily manipulated experimentally. Described here are the first attempts at application of this novel system to study MM and test therapies. Cell lines ARH-77 and CAG line and fresh patient cells (5 × 10⁶/embryo) were injected IV into turkey egg chorioallantoic membrane veins on embryonic day E11. Engraftment of human cells in hematopoietic organs, bone marrow (BM) and liver was detected 7 days later (E18) by RTPCR, immunohistochemistry and flow cytometry and by circulating free light chain (6-25 mg/L) in the peripheral blood of 100% of the injected cell lines and 50% of patients myelomas. Treatment with Velcade (Bortezomib) or Revlimid IV on E13 (48 hours after MM cell injection), at drug levels that were precalibrated to be non-toxic to the developing embryonic BM, dramatically reduced engraftment, demonstrating the utility of this new model for testing drug activity in vivo. ARH-77 cells, detected by flow cytometry of the embryonic BM cells with anti-human CD19, CD38 and CD138, were inhibited from 8.5% engraftment to 0.72% after a single Velcade treatment, with an 18 fold decrease compared to untreated embryos in the ratio of human to avian cells in BM tissue. determined by Q-RT-PCR analysis of human alpha satellite and avian GAPDH DNA normalized per cell. Very similar results were obtained with Revlimid. The results presented suggest that with further work the turkey embryo model may provide an affordable, rapid and practical xenograft system in vivo for studying the biology of MM, for affordably testing MM therapies, as well for developing a new method for individualized patient screening for response or resistance to particular therapeutic agents.

1. Taizi M, Deutsch VR, Leitner A, Ohana A, Goldstein RS. A novel and rapid in vivo system for testing therapeutics on human leukemias. Exp Hematol. 2006;34:1698-1708.

2. Grinberg I, Reis A, Ohana A, et al. Engraftment of human blood malignancies to the turkey embryo: a robust new in vivo model. Leuk Res. 2009;33:1417-1426.