Nobuaki Fukushima

Small-molecule Hedgehog inhibitor attenuates the leukemia-initiation potential of acute myeloid leukemia cells.

Aberrant activation of the Hedgehog signaling pathway has been implicated in the maintenance of leukemia stem cell populations in several model systems. PF‐04449913 (PF‐913) is a selective, small‐molecule inhibitor of Smoothened, a membrane protein that regulates the Hedgehog pathway. However, details of the proof‐of‐concept and mechanism of action of PF‐913 following administration to patients with acute myeloid leukemia (AML) are unclear. This study examined the role of the Hedgehog signaling pathway in AML cells, and evaluated the in vitro and in vivo effects of the Smoothened inhibitor PF‐913. In primary AML cells, activation of the Hedgehog signaling pathway was more pronounced in CD34+ cells than CD34− cells. In vitro treatment with PF‐913 induced a decrease in the quiescent cell population accompanied by minimal cell death. In vivo treatment with PF‐913 attenuated the leukemia‐initiation potential of AML cells in a serial transplantation mouse model, while limiting reduction of tumor burden in a primary xenotransplant system. Comprehensive gene set enrichment analysis revealed that PF‐913 modulated self‐renewal signatures and cell cycle progression. Furthermore, PF‐913 sensitized AML cells to cytosine arabinoside, and abrogated resistance to cytosine arabinoside in AML cells cocultured with HS‐5 stromal cells. These findings imply that pharmacologic inhibition of Hedgehog signaling attenuates the leukemia‐initiation potential, and also enhanced AML therapy by sensitizing dormant leukemia stem cells to chemotherapy and overcoming resistance in the bone marrow microenvironment.

Combinations of cytogenetics and international scoring system can predict poor prognosis in multiple myeloma after high-dose chemotherapy and autologous stem cell transplantation

High‐dose chemotherapy followed by autologous stem cell transplantation (ASCT) is a standard therapy for newly diagnosed multiple myeloma. Combinations of recently proposed prognostic factors such as cytogenetics and international scoring system (ISS) may be useful to predict prognosis after ASCT. This study evaluated 60 consecutive patients who underwent ASCT in four institutes. The median age of patients was 57 years old. Cytogenetic analyses of bone marrow at diagnosis detected metaphase abnormalities in 9 of 51 patients and interphase abnormalities in six of 35 patients (17p13 deletion, t(4;14) and t(14;16)). Seventeen patients had ISS stage 3 at diagnosis. Twenty‐five patients who had any of these risk factors were defined as high risk. All patients were conditioned with high‐dose melphalan. With a median follow‐up of 3.4 years, overall survival and event‐free survival at 3 years were significantly worse in high‐risk patients (48% vs. 97%; P = 0.0005 and 16% vs. 37%; P = 0.038, respectively) despite the higher CR plus VGPR rate among high‐risk patients. In addition, survival at 1 year after progression was significantly worse in high‐risk patients despite salvage chemotherapy containing thalidomide (32% vs. 100%, P = 0.0001). Combinations of cytogenetics and ISS could readily predict prognosis. Quality of response is a poor surrogate marker for ultimate outcome. High‐risk patients may need more effective treatment. Am. J. Hematol. 2009.

Abstract 1884: Treatment with Hedgehog inhibitor PF-913 attenuates leukemia-initiation potential in acute myeloid leukemia cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Aberrant activation of the Hedgehog (Hh) signaling pathway is involved in a variety of cancers, and required for maintenance of the leukemic stem cell (LSC) populations in several experimental systems. Cumulative evidence suggests that dormant self-renewing LSC contribute to acute myeloid leukemia (AML) propagation and relapse by evading conventional chemotherapies that target cycling cells. PF-04449913 (PF-913) is a novel oral small molecule inhibitor that selectively binds and targets Smoothened (SMO), a membrane protein regulating the Hh pathway. Treatment with PF-913 has shown promising results regarding safety, tolerability, and early signs of efficacy in patients with hematologic malignancies including AML. However, the detailed mechanisms and biomarkers remain to be elucidated in AML therapy. Using the co-culturing system with HS-5 stromal cells, the colony assay system, and the immunodeficient NOD/SCID/IL2rγnull (NOG) mouse model serially xenotransplanted with primary AML cells, we examined the effects of PF-913 on LSC population and AML propagation. In primary AML cells, the Hh signaling pathway was activated more in CD34-positive cells than CD34-negative cells. Ex vivo-treatment with PF-913 inhibited proliferation and induced minimal cell death in leukemia cell lines and primary AML cells. However, in vivo-treatment with PF-913 attenuated leukemia-initiation potential in AML cells through the serial transplantation system (0% human-CD45+ cells in bone marrow cells derived from the 2nd recipient mice), while limiting reduction of tumor burden in the primary leukemia system. Also in the colony-assay system using primary AML cells, treatment with PF-913 reduced serially colony formation. In leukemia cell lines and primary AML cells, treatment with PF-913 decreased the quiescent (Hoechst-33342low/Pyronin-Ylow) cell population as well as down-regulated mRNA encoding downstream effector GLIs and GLI-targeting molecules in the canonical Hh pathway. In the in vivo-NOG mouse system, comprehensive Gene Set Enrichment Analysis (GSEA) revealed that PF-913 treatment modulated cell cycle regulation and self-renewal signaling in primary AML cells. Moreover, combined treatment with PF-913 abrogated resistance to Ara-C in AML cell lines co-cultured with HS-5 stromal cells and sensitized AML cells to Ara-C in the cutaneous tumor system. Our findings imply that selective Hh inhibitor, PF-913 treatment can attenuate the leukemia-initiation potential in AML cells by modulation of cell cycle regulation and self-renewal signaling, and can also improve AML therapy through sensitizing dormant LSC to chemotherapy and overcoming the resistance in the bone marrow microenvironment. Citation Format: Yosuke Minami, Nobuaki Fukushima, Anil Sadarangani, Hironobu Minami, Catriona Jamieson, Tomoki Naoe. Treatment with Hedgehog inhibitor PF-913 attenuates leukemia-initiation potential in acute myeloid leukemia cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1884. doi:10.1158/1538-7445.AM2014-1884

Acute Megakaryoblastic Leukemia Developing as Donor Cell Leukemia after Umbilical Cord Blood Transplantation

A 64-year-old man with acute myeloid leukemia underwent umbilical cord blood transplantation (UCBT). After 11 months of complete remission (CR) following UCBT, the bone marrow showed 7.5% myeloblasts. CR was obtained after a single course of azacitidine monotherapy, but the myeloblasts gradually increased in the blood. We made a diagnosis of acute megakaryoblastic leukemia derived from donor cell with a fluorescence in situ hybridization (FISH) analysis of the sex chromosomes and an immunophenotypic analysis. Azacitidine was administered again and produced a therapeutic effect of stable disease. This case suggests that azacitidine may be a useful therapy for patients with acute megakaryoblastic leukemia in situations in which intensive chemotherapy and transplantation are not indicated.

Promising Outcome of Umbilical Cord Blood Transplantation in Patients with Multiple Comorbidities

The hematopoietic cell transplantation-specific comorbidity index (HCT-CI) has been recently proposed to predict the probability of nonrelapse mortality (NRM) and overall survival (OS) in allogeneic hematopoietic stem cell transplantation (HSCT). However, the usefulness of the HCT-CI in single-unit umbilical cord blood transplantation (UCBT) remains unclear. We investigated the impact of the HCT-CI on the clinical outcomes of allogeneic HSCT in a single-center retrospective study including 53 recipients of UCBT (UCBT group) and 90 recipients of other HSCT (non-UCBT group). In the non-UCBT group 2-year OS rates for HCT-CI score < 3 and ≥3 were 67% (n = 74; 95% confidence interval [CI], 54% to 78%) and 26% (n = 16; 95% CI, 7% to 51%), respectively (P = .001). In the UCBT group these rates were 66% (n = 39; 95% CI, 48% to 79%) and 69% (n = 14; 95% CI, 36% to 87%), respectively (P = .73). In the non-UCBT group 1-year NRM rates for HCT-CI score < 3 and ≥3 were 14% (95% CI, 6.4% to 22%) and 37% (95% CI, 14% to 61%), respectively (P = .02). In the UCBT group these rates were 6.1% (95% CI, 3.4% to 24%) and 7.7% (95% CI, .4% to 29%), respectively (P = .78). Using multivariate analysis we showed that HCT-CI score ≥ 3 was significantly associated with lower OS (hazard ratio, 3.06; 95% CI, 1.47 to 6.38; P = .003) and higher NRM (hazard ratio, 2.87; 95% CI, 1.18 to 6.96; P = .02) for the non-UCBT group. UCBT showed good OS with low incidence of NRM, even in patients with high HCT-CI scores. Altogether, we propose single-unit UCB to be a promising stem cell source for improving survival in patients with multiple comorbidities.