Key Points• Auto-HSCT in CR1 provides long-term remission in BPDCN patients.• RIC allo-HSCT and MAC allo-HSCT results are comparable.We sought to clarify the role of high-dose chemotherapy followed by autologous hematopoietic stem cell transplantation (auto-HSCT) and allogeneic hematopoietic stem cell transplantation (allo-HSCT) to treat blastic plasmacytoid dendritic cell neoplasm (BPDCN). We retrospectively identified 25 BPDCN patients (allo-HSCT, n 5 14; auto-HSCT, n 5 11) from registry data of the Japan Society for Hematopoietic Cell Transplantation and analyzed clinicopathologic data and clinical outcomes after transplantation. The median age at HSCT was 58 years (range, 17-67 years). All 11 patients who underwent auto-HSCT were in the first complete remission (CR1). With a median follow-up of 53.5 months, the overall survival rates at 4 years for patients who underwent auto-HSCT and allo-HSCT were 82% and 53% (P 5 .11), respectively, and progression-free survival rates were 73% and 48% (P 5 .14), respectively. Auto-HSCT for BPDCN in CR1 appears to provide promising results and deserves further evaluation in the setting of prospective trials. (Blood. 2015;125(23):3559-3562)

Valproic acid (VPA), a histone deacetylase inhibitor, upregulates NKG2D ligands (NKG2DLs) on some monocytic and lymphoid leukemic cells. However, its effect on myeloid leukemia cells and synergistic agents that can augment the effect of VPA remains unknown. Of the various myeloid cell lines examined, OUN-1, a chronic myelogenous leukemia cell line, showed the most prominent upregulation of MICA ⁄ B and ULBP2 in response to VPA. The NKG2DL upregulation was observed only in leukemic cells without apoptosis and the effect was abrogated by pretreatment of cells with caffeine, an inhibitor of ATM ⁄ ATR. Several activators of ATM ⁄ ATR were screened for their effect on NKG2DL expression, but only hydroxyurea (HU) efficiently upregulated both MICA ⁄ B and ULPB2 expression on the cell line. VPA and HU synergistically upregulated the NKG2DLs on OUN-1 cells as well as primary leukemic cells from some patients with acute myeloid leukemia. (1-3) Several lines of evidence indicate that the expression level of NKG2D ligand (NKG2DL) on leukemia cells affects the sensitivity of the leukemic cells to killing by NK cells.(4-11) Various agents have been evaluated for their inducibility of NKG2DLs on leukemic cells, to augment the NK cell-mediated antileukemia effect. (4,8,9,(12)(13)(14) Valproic acid (VPA), a histone deacetylase inhibitor, is a potent inducer of NKG2DLs such as MICA ⁄ B and ULBPs on malignant cells. (9,12,14) VPA augments the expression of MICA and ULBP2 on several monocytic and lymphoid leukemia cell lines and primary acute myeloid leukemia (AML) cells in vitro and in vivo.(9,12) However, the mechanisms for the upregulation of NKG2DL on AML cells by VPA has not been studied extensively due to the lack of myeloid leukemia cell lines that display an upregulation of NKG2DLs in response to VPA. Clarifying the mechanisms associated with upregulation could identify other reagents that synergize with VPA to augment the expression of NKG2DL by myeloid leukemia cells and thereby enhance the susceptibility of leukemic cells to NK cells.

To determine how immunosuppressant agents used for graft-versus-host disease (GVHD) prophylaxis affect natural killer (NK) cells, we examined the effects of cyclosporine (CSP), tacrolimus (TAC), mycophenolic acid (MPA, an active form of mycophenolate mofetil), and methotrexate (MTX) on the proliferation and cytotoxicity of NK cells. The proliferation of NK cells from healthy individuals in the presence of interleukin (IL)-2 and IL-15 was suppressed to 51% ± 16% of that of the controls with CSP, to 31% ± 19% with TAC, to 14% ± 6% with MPA, and to 87% ± 18% with MTX. Both CSP and TAC increased the proportion of CD16(-)CD56(bright) cells, a NK cell subset capable of secreting high amount of cytokines, and also enhanced NKp30 expression, whereas MPA markedly decreased the proportion of CD16(-)CD56(bright) cells and reduced the expression of all activating NK cell receptors, including NKG2D, NKp30, NKp44, and NKp46. MPA also reduced the cytotoxicity against K562 cells from 61% ± 15% to 17% ± 7% and that against Daudi cells from 44% ± 4% to 4% ± 4%, whereas the other 3 drugs did not diminish these cytotoxicities. The inhibition of NK cell proliferation and cytotoxicity against leukemic cell lines by MPA was partially abolished by the inclusion of guanosine in the culture. Similar to the effect of MPA on T cells, MPA inhibited the down-regulation of p27 on NK cells induced by the incubation of NK cells in the presence of IL-2. These results suggest that MPA is a potent inhibitor of NK cells, and that its inclusion in the GVHD prophylaxis regimen might diminish the graft-versus-leukemia effect of NK cells.

BackgroundMost patients with multiple myeloma (MM) are considered to be incurable, and relapse owing to minimal residual disease (MRD) is the main cause of death among these patients. Therefore, new technologies to assess deeper response are required.Patients and methodsWe retrospectively analyzed 125 patients with MM who underwent high-dose melphalan plus autologous stem-cell transplantation (ASCT) to detect MRD in autograft/bone marrow (BM) cells using a next-generation sequencing (NGS)-based method and allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR).ResultsNGS-based method was applicable to 90% and this method had at least one to two logs greater sensitivity compared to ASO-PCR. MRD negative by NGS [MRDNGS(−)] (defined as <10−6) in post-ASCT BM cases (n = 26) showed a significantly better progression-free survival (PFS) (96% at 4 years, P < 0.001) and overall survival (OS) (100% at 4 years, P =0.04) than MRDNGS(+) in post-ASCT BM cases (n = 25). When restricting the analysis to the 39 complete response cases, patients who were MRDNGS(−) (n = 24) showed a significantly better PFS than those that were MRDNGS(+) (n = 15) (P =0.02). Moreover, MRDNGS(−) in post-ASCT BM cases (n = 12) showed significantly a better PFS than MRDNGS(+) cases (n = 7) where MRD was not detected by ASO-PCR (P = 0.001). Patients whose autografts were negative by NGS-based MRD assessment (<10−7) (n = 19) had 92% PFS and 100% OS at 4 years post-ASCT. Conversely, the NGS-based MRD positive patients who received post-ASCT treatment using novel agents (n = 49) had a significantly better PFS (P = 0.001) and tended to have a better OS (P= 0.214) than those that were untreated (n = 33).ConclusionsLow level MRD detected by NGS-based platform but not ASO-PCR has significant prognostic value when assessing either the autograft product or BM cells post-ASCT.