Different Dosage of Bortezomib Impacts the Prevention of Acute Graft-Versus-Host Disease.

Abstract 4499

The proteasome inhibitor bortezomib which prevents nuclear factor kappaB (NF-kappaB) activation, blocks T-cell activation, induces T cell and dendritic cells apoptosis, and inhibits dendritic cells mature. Bortezomib has been used successfully in the treatment of graft-versus-host disease (GVHD) and autoimmune diseases in animal models. As recent reports, bortezomib not only could prevent GVHD but also induce severe GVHD which depends on the time of administration. We explored whether the dosage of bortezomib impacts the prevention of aGVHD. For this purpose, different dosage of bortezomib (10ug/kg, 100ug/kg, 800ug/kg) were administrated to recipient C57BL/6 (H2b) mice which were lethally irradiated and given transplants of bone marrow cells and splenocytes from major histocompatibility complex (MHC)-disparate BALB/c (H2d) donors. The median survival time of control group was 31 days (19 to 37), low dosage group (10ug/kg) was 27.5 days (range: 18 to 42), intermediate dosage group(100ug/kg) was 45 days (range: 32 to 67), and high dosage group(800ug/kg) was 33 days (range:22 to 67). The survival time of intermediate dosage group compared with control group and other dosage group increased significantly (P < 0.05). On day +30,all the inter-dose group mice were alive(100%), and the control group, the low-dose group and the high-dose group remained 40%(2/5), 30% (3/10) and 60% (6/10) mice, respectively. On day +60, the inter-dsoe group and the high-dose group remained three and one alive, respectively. Pathologic assessment of skin and liver during aGVHD on day +30 showed less lesions in inter-dose group and high-dose group than low-group and control group. Interestingly, pathology also revealed that significant increases in gastrointestinal lesions occurred following high dose (800ug/kg) bortezomib administration in aGVHD. The results show that intermediate dosage bortezomib could effectively improve the survival time and protect injury from aGVHD. In this study, we detected T cell apoptosis by Annexin-V/PI. The percentages of the apoptosis cells in control group, low-, inter- and high dosage group were 4.00±0.14, 4.65±0.2, 12.13±0.14 and 12.37±0.75, respectively. The result indicated T cell apoptosis induced by bortezomib were more evident in the inter-dose group and high-dose group than low-dose group and control group (P<0.05). Also, the proportion of CD4+CD25+ regulatory T cells were significantly increase in the inter-dose group and high-dose group than other two groups (inter-, high-dose group, and contral group, low- dose group were 30.25±6.32%, 35.25±2.14%, and 21.71±0.52%, 23.15±4.12%, respectively; P<0.05). Otherwise, the level of serum IL-2 decreased and IL-4 increased significantly in intermediate and high dosage group, the low dosage bortezomib didn't affect the leverl of serum IL-2 and IL-4. Intermediate dosage of bortezomib prevents aGVHD without presenting obvious adverse effects. The effect of bortezomib on preventing aGVHD are relevant to T cell apoptosis, regulating IL-2 and IL-4 levels and increasing regulatory T cell level. These results indicated that the prevention effects of proteasome inhibition with bortezomib on aGVHD are critically dependent on the dosage of bortezomib administration. And these results establish the basis for the clinical use of bortezomib in the management of graft-versus-host disease (GVHD).

This work was supported by Science and Technology Planning Project of Guangdong Province (2006B36005003,2007A032100003) and Science and Technology Planning Project of Guangzhou (2006Z2-E4071,2008A1-E4011-4,2008A1-E4011-5).