Background: Consolidative allogeneic hematopoietic stem cell transplantation is a controversial option for patients with relapsed/refractory acute lymphoblastic leukemia after chimeric antigen receptor T cell (CAR-T) therapy. We performed a multicenter retrospective study to assess whether patients can benefit from haploidentical hematopoietic stem cell transplantation after CAR-T therapy.Methods: A total of 122 patients after CAR-T therapy were enrolled, including 67 patients without subsequent transplantation (non-transplant group) and 55 patients with subsequent haploidentical hematopoietic stem cell transplantation (transplant group). Long-term outcome was assessed, as was its association with baseline patient characteristics. Results: Compared with the non-transplant group, transplantation recipients had a higher 2-year overall survival (OS; 77.0% versus 36.4%; P < 0.001) and leukemia-free survival (LFS; 65.6% versus 32.8%; P < 0.001). Multivariate analysis showed that minimal residual disease (MRD) positivity at transplantation is an independent factor associated with poor LFS (P = 0.005), OS (P = 0.035), and high cumulative incidence rate of relapse (P = 0.045). Pretransplant MRD-negative recipients (MRD− group) had a lower cumulative incidence of relapse (17.3%) than those

Relapses of CD19-expressing leukemia in patients who achieved initial remission after CART cell treatment have been reported to correlate with poor CART cells persistence. Sustained tonic signaling or strong activation drives CART cell differentiation and exhaustion, which limit the therapeutic efficacy and persistence of CART cells. Here, we identified dasatinib as the optimal candidate to prevent or reverse both CD28/CART and 4-1BB/CART cell differentiation and exhaustion during ex vivo expansion, which profoundly enhanced the therapeutic efficacy and in vivo persistence. Moreover, strong activation-induced CART cells differentiation, exhaustion and apoptosis driven by CD3/CD28 stimulation or antigen exposure were dramatically prevented or reversed by dasatinib treatment. Mechanistically, dasatinib markedly reduced the phosphorylation of Src and Lck, and downregulated the expression of genes involved in CAR signaling pathways, which resulted in the optimization of cell differentiation, exhaustion and apoptosis-related gene expression. Our study proposes a promising pharmacological approach for optimizing CART cells manufacture, and provides an experimental basis for reinvigorating CART cells in clinical application.

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are pivotal components of the leukemic microenvironment. BM-MSCs have been previously reported to promote the proliferation of leukemic cells. To further understand the molecular mechanisms of BM-MSC-induced proliferation of leukemic cells, the present study co-cultured acute lymphoblastic leukemia (ALL) Reh cells with BM-MSCs. The current study used methods including shRNA, flow cytometry, MTT, reverse transcription-quantitative polymerase chain reaction, ELISA and western blotting. The data of the present study demonstrated that BM‑MSCs promote the proliferation of Reh cells and the NR2F2 mRNA and protein levels were elevated in BM‑MSCs following co‑culture. Additionally, it was demonstrated that shRNA knockdown of NR2F2 inhibited BM‑MSC‑induced proliferation of Reh cells. Furthermore, following downregulation of NR2F2, vascular endothelial growth factor A (VEGFA) secretion by BM‑MSCs was reduced. The present study demonstrated that NR2F2 mediates BM‑MSC‑induced proliferation of Reh cells, partially via regulation of VEGFA. Disrupting microenvironmental support by targeting NR2F2 may be a potential therapeutic strategy for ALL.

Recent developments and re-emergence of interferon α (IFN-α) have renewed interest in the therapy for patients with chronic myeloid leukemia (CML). Related molecular mechanism may be the direct effect of IFN-α on CML stem cells. Human mesenchymal stromal cells (hMSCs) are important to protect CML stem cells, and IFN-α was described as a potential inhibitor of hMSCs. However, the exact mechanism remains obscure. PML as a known tumor suppressor locates downstream of the IFN-α pathway, and little is known about the PML gene regulation in hMSCs. The aim of this study was to investigate the effects of IFN-α on hMSCs and defined the role of PML involved in this process. Our results suggested that hMSCs incurred senescence upon IFN-α stimulation, while PML levels were observed significant increased. The recombinant lentiviral vector, which encodes shRNA against PML or full-length PML cDNA, was constructed. By knocking-down and overexpressing PML, we found that PML was indispensable to IFN-α mediated hMSC senescence. The molecular mechanism underlying this process may be an increased co-localization of PML and p53 induced by IFN-α. Our data demonstrated that IFN-α can induce cellular senescence of hMSCs and PML plays a key role in this process. These findings provided novel insight into the effect of IFN-α on hMSCs.

Mesenchymal stem cells are characterized with self-renewal capacity and pluripotency. NR2F2 is a nuclear receptor that has been detected in the mesenchymal compartment of developing organs. However, whether NR2F2 plays a role in the stemness maintenance of mesenchymal stem cells has not been explored yet. In this study, we investigated the function of NR2F2 in bone marrow-derived mesenchymal stem cells via shRNA-mediated knock-down of NR2F2. The suppression of NR2F2 impaired the colony-forming efficacy of mesenchymal stem cells. The inhibition of colony-forming capacity may be attributed to the acceleration of senescence through upregulation of P21 and P16. The downregulation of NR2F2 also suppressed both osteogenic and adipogenic differentiation processes. In conclusion, NR2F2 plays an important role in the stemness maintenance of bone marrow-derived mesenchymal stem cells.