2-Methoxyestradiol Treatment Prevents Graft-Versus-Host Disease While Preserving Graft-Versus-Leukemia Effect in Mice

GVHD is mediated by donor T lymphocytes against recipient antigen presenting cells (APCs) and tissues. 2-Methoxyestradiol (2ME2, Panzem) is an endogenous metabolite that at pharmacologic doses exerts antimitotic and anti-angiogenic properties. 2ME2 has been well-tolerated and safe in phase I/II clinical trials targeting various tumor types. The plasma levels of 2ME2 may increase up to 1,000-fold during pregnancy and correlate temporally with the remission of rheumatoid arthritis (RA) and multiple sclerosis symptoms. 2ME2 has also been shown to exhibit disease-modifying activity in autoimmune models of RA. The activity of 2ME2 in these autoimmune disease models suggests it may have potential efficacy for GVHD. Using the C57BL/6 into BALB/c GVHD mouse model, we found 80% of 2ME2-treated recipients survived in comparison to 20% of PBS control mice (P=0.004). Whereas control recipients had severe GVHD in the skin, intestine, liver, and lung, 2ME2-treated mice exhibited only mild changes in these organs, reflected in their significantly lower GVHD scores. On day 7 post-transplant, there was a significantly lower number of donor-derived CD4+ and CD8+ subset in the peripheral lymph node and Peyer’s patches of 2ME2-treated mice compared to that of PBS control recipients. The percentage of IFNγ+ subset of donor-derived CD4+ T cells was reduced in the spleen (26.5% vs 31.2%) of 2ME2-treated mice compared to the control recipients. The same trend was observed for IL-2+ subset of donor-derived CD4+ cells (26.5% vs 31.2%). However, the percentage of donor-derived IL-17+CD4+ cells in the spleen of 2ME2-treatment mice did not decrease in comparison of control recipients. The reduction of IFN-γ and IL-2 was also observed in the serum collected 7 days post-transplant. The results demonstrated that 2ME2 treatment inhibits Th1 polarization and reduces IL-2 production in GVHD mice. To investigate whether GVL activity was maintained in the presence of 2ME2 treatment, we used P815 leukemia cell line transduced with a lentivirus vector coding for firefly luciferase (FLuc) for bioluminescence imaging (BLI). Serial BLI images showed the rapid tumor growth in mice received P815 and bone marrow cells alone (P815+BM) with PBS or 2ME2 treatment. Images and photon flux showed P815 leukemic engraftment with significantly reduced signal and leukemia infiltration in mice received P815, bone marrow and splenocytes (P815+BM+SP) with or without 2ME2 treatment. The overall survival of P815-bearing mice was prolonged in the mice received P815+BM+SP compared to mice received P815+BM alone. The data demonstrated 2ME2 treatment appears to preserve the GVL activity against P815 in mouse model. Our studies have established the disease-modifying activity of 2ME2 in mouse GVHD model, and thus raise the possibility for using this drug as a potential new therapeutic intervention for prevention or treatment of acute GVHD.