Refractory chronic graft-versus-host disease (cGVHD) is a significant complication resulting from allogeneic hematopoietic stem cell transplantation (HSCT). Mesenchymal stromal cells (MSCs) have shown promise for treating refractory cGVHD, but the favorable effects of MSCs therapy in cGVHD are complex and not fully understood. In this prospective clinical study, 20 of 23 cGVHD patients had a complete response or partial response in a 12-month follow-up study. The most marked improvements in cGVHD symptoms were observed in the skin, oral mucosa and liver. Clinical improvement was accompanied by a significantly increased number of interleukin (IL)-10-producing CD5+ B cells. Importantly, CD5+ B cells from cGVHD patients showed increased IL-10 expression after MSCs treatment, which was associated with reduced inflammatory cytokine production by T cells. Mechanistically, MSCs could promote the survival and proliferation of CD5+ regulatory B cells (Bregs), and indoleamine 2, 3-dioxygenase partially participates in the MSC-mediated effects on Breg cells. Thus, CD5+ Breg cells may have an important role in the process of MSC-induced amelioration of refractory cGVHD and may provide new clues to reveal novel mechanisms of action for MSCs.
Tyrosine kinase inhibitor (TKI) resistance and progression to blast crisis (BC), both related to persistent β-catenin activation remain formidable challenges for chronic myeloid leukemia (CML). We observed overexpression of β-catenin in BC-CML stem/progenitor cells, particularly in GMP progenitors, and highest among a novel CD34+CD38+CD123hiTim-3hi subset as determined by CyTOF analysis. Co-culture with mesenchymal stromal cells (MSCs) induced the expression of β-catenin and its target CD44 in CML cells. A novel Wnt/β-catenin signaling modulator, C82, and nilotinib synergistically killed KBM5T315I and TKI-resistant primary BC-CML cells with or without BCR-ABL kinase mutations even under leukemia/MSC co-culture conditions. Silencing of β-catenin by siRNA restored sensitivity of primary BCR-ABLT315I/E255V BC-CML cells to nilotinib. Combining the C82 pro-drug, PRI-724, with nilotinib significantly prolonged the survival of NOD/SCID/IL2Rγnull mice injected with primary BCR-ABLT315I/E255V BC-CML cells. The combined treatment selectively targeted CML progenitors and inhibited CD44, c-Myc, survivin, p-CRKL, and p-STAT5 expression. Additionally, pretreating primary BC-CML cells with C82, or the combination, but not with nilotinib alone, significantly impaired their engraftment potential in NOD/SCID/IL2Rγnull-3/GM/SF mice and significantly prolonged survival. Our data suggest potential benefit of concomitant β-catenin and Bcr-Abl inhibition to prevent or overcome Bcr-Abl kinase-dependent or –independent TKI-resistance in BC-CML.
Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for severe aplastic anemia (SAA) is mainly limited by the high incidence of graft failure and GvHD. Mesenchymal stem cells (MSCs) have been shown to support hematopoiesis in vivo and to display potent immunosuppressive effects to prevent or treat GvHD after HSCT. In a multicenter phase II trial, we developed an approach with co-transplantation of MSCs in patients undergoing haplo-HSCT. Forty-four patients with SAA were included. The conditioning regimen included busulfan, cyclophosphamide and thymoglobulin (ATG). The recipients received cyclosporin A (CsA), mycophenolate mofetil and short-term methotrexate for GvHD prophylaxis. Three out of 44 patients, who died early before hematopoietic engraftment, were not assessed. Evaluable patients (97.6%; 40/41) achieved hematopoietic reconstitution and sustained full donor chimerism. The median time for myeloid engraftment was 12 days (range 8-21 days) and for platelet engraftment was 19 days (range 8-154 days). The incidence was 29.3% for grade II-IV acute GvHD and 14.6% for chronic GvHD. The overall survival was 77.3% with a median 12-month (range 0.9-30.8) follow-up for surviving patients. These data suggest that co-transplantation of MSCs could reduce the risk of graft failure and severe GvHD in haplo-HSCT for SAA.
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