Targeting Poly(ADP)ribose polymerase in BCR/ABL1-positive cells.

BCR/ABL1 causes dysregulated cell proliferation and is responsible for chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph1-ALL). In addition to the deregulatory effects of its kinase activity on cell proliferation, BCR/ABL1 induces genomic instability by downregulating BRCA1. PARP inhibitors (PARPi) effectively induce cell death in BRCA-defective cells. Therefore, PARPi are expected to inhibit growth of CML and Ph1-ALL cells showing downregulated expression of BRCA1. Here, we show that PARPi effectively induced cell death in BCR/ABL1 positive cells and suppressed colony forming activity. Prevention of BCR/ABL1-mediated leukemogenesis by PARP inhibition was tested in two in vivo models: wild-type mice that had undergone hematopoietic cell transplantation with BCR/ABL1-transduced cells, and a genetic model constructed by crossing Parp1 knockout mice with BCR/ABL1 transgenic mice. The results showed that a PARPi, olaparib, attenuates BCR/ABL1-mediated leukemogenesis. One possible mechanism underlying PARPi-dependent inhibition of leukemogenesis is increased interferon signaling via activation of the cGAS/STING pathway. This is compatible with the use of interferon as a first-line therapy for CML. Because tyrosine kinase inhibitor (TKI) monotherapy does not completely eradicate leukemic cells in all patients, combined use of PARPi and a TKI is an attractive option that may eradicate CML stem cells.

Synergistic effect of combined PI3 kinase inhibitor and PARP inhibitor treatment on BCR/ABL1-positive acute lymphoblastic leukemia cells.

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) function by inhibiting base excision repair and inducing synthetic lethality in homologous recombination repair-deficient cells, such as BRCA1/2-mutated cancer cells. The BCR/ABL1 fusion protein causes dysregulated cell proliferation and is responsible for chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL). BCR/ABL1 also induces genomic instability by downregulating BRCA1. We investigated the effect of the PARPi, olaparib, against Ph+ALL cell lines and found that they show variable sensitivity, presumably due to cancer-associated genetic alterations other than BCR/ABL1. To investigate the reasons for the variable responses of Ph+ALL cells to PARPi treatment, we analyzed the transcriptomes of olaparib-sensitive and -resistant Ph+ALL cell lines, which revealed that activation of the phosphatidylinositol 3-kinase (PI3K) pathway was a hallmark of PARPi resistance. Based on these findings, we examined the effects of adding a PI3K inhibitor (PI3Ki) to PARPi treatment to overcome PARPi insensitivity in Ph+ALL cell lines. Combination with PI3Ki increased PARPi cytotoxicity in PARPi-resistant Ph+ALL cell lines. Tyrosine kinase inhibitor (TKI) therapy is the gold standard for Ph+ALL, and, based on our findings, we propose that PARPi combined with TKI and PI3K inhibition could be a novel therapeutic strategy for Ph+ALL.

Hematopoietic Cell Transplantation with Reduced Intensity Conditioning Using Fludarabine/Busulfan or Fludarabine/Melphalan for Primary Immunodeficiency Diseases.

PURPOSE: The purpose of our study was to compare the safety and efficacy of hematopoietic cell transplantation (HCT) using fludarabine (Flu)-based reduced intensity conditioning (RIC) with busulfan (BU) or melphalan (Mel) for primary immunodeficiency diseases (PID). METHODS: We retrospectively analyzed transplant outcome, including engraftment, chimerism, immune reconstitution, and complications in 15 patients with severe combined immunodeficiency (SCID) and 27 patients with non-SCID PID. The patients underwent Flu-based RIC-HCT with BU (FluBU: 7 SCID, 16 non-SCID) or Mel (FluMel: 8 SCID, 11 non-SCID). The targeted low-dose BU with therapeutic drug monitoring was set to 30 mg hour/L for SCID. RESULTS: The 2-year overall survival of all patients was 79.6% and that of patients with SCID in the FluBU and FluMel groups was 100% and 62.5%, respectively. In the FluBU group, all seven patients achieved engraftment, good immune reconstitution, and long-term survival. All five patients receiving umbilical cord blood transplantation achieved complete or high-level mixed chimerism and sufficient specific IgG production. In the FluMel group, six of eight patients achieved complete or high-level mixed chimerism. Viral reactivation or new viral infection occurred in one FluBU group patient and four FluMel group patients. In the non-SCID group, 10 of 11 patients (91%) who received FluMel achieved complete or high-level mixed chimerism but had variable outcomes. Patients with WAS (2/2 patients), NEMO deficiency (2/2 patients), and X-linked hyper IgM syndrome (2/3 patients) who received FluBU achieved complete or high-level mixed chimerism and long-term survival. CONCLUSIONS: RIC-HCT with FluBU is a safe and effective strategy for obtaining high-level donor chimerism, immune reconstitution including B cell function, and long-term survival in patients with SCID. In patients with non-SCID PID, the results varied according to the subtype of the disease. Further prospective studies are required to optimize the conditioning regimen for non-SCID PID.

Hematopoietic stem cell transplantation for progressive combined immunodeficiency and lymphoproliferation in patients with activated phosphatidylinositol-3-OH kinase δ syndrome type 1.

BACKGROUND: Activated phosphatidylinositol-3-OH kinase δ syndrome type 1 (APDS1) is a recently described primary immunodeficiency syndrome characterized by recurrent respiratory tract infections, lymphoid hyperplasia, and Herpesviridae infections caused by germline gain-of-function mutations of PIK3CD. Hematopoietic stem cell transplantation (HSCT) can be considered to ameliorate progressive immunodeficiency and associated malignancy, but appropriate indications, methods, and outcomes of HSCT for APDS1 remain undefined. OBJECTIVE: Our objective was to analyze the clinical manifestations, laboratory findings, prognosis, and treatment of APDS1 and explore appropriate indications and methods of HSCT. METHODS: We reviewed retrospectively the medical records of cohorts undergoing HSCT at collaborating facilities. RESULTS: Thirty-year overall survival was 86.1%, but event-free survival was 39.6%. Life-threatening events, such as severe infections or lymphoproliferation, were frequent in childhood and adolescence and were common indications for HSCT. Nine patients underwent HSCT with fludarabine-based reduced-intensity conditioning. Seven patients survived after frequent adverse complications and engraftment failure. Most symptoms improved after HSCT. CONCLUSION: Patients with APDS1 showed variable clinical manifestations. Life-threatening progressive combined immunodeficiency and massive lymphoproliferation were common indications for HSCT. Fludarabine-based reduced-intensity conditioning-HSCT ameliorated clinical symptoms, but transplantation-related complications were frequent, including graft failure.

Hematopoietic cell transplantation for asymptomatic X-linked lymphoproliferative syndrome type 1.

BACKGROUND: X-linked lymphoproliferative disease type 1 (XLP1) is a rare primary immune deficiency, which is caused by SH2D1A gene mutations. XLP1 is commonly associated with Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis, hypogammaglobulinemia, and/or lymphoma. The only curative treatment for XLP1 is allogeneic hematopoietic cell transplantation. However, published data detailing the clinical course of, and indications for, allogeneic hematopoietic cell transplantation in asymptomatic patients with XLP1 is lacking. Although relevant family history could be useful in identifying patients with XLP1 before disease onset, no guidelines have been established on the management of asymptomatic patients with XLP1. Therefore, clinicians and families face dilemmas in balancing between the risk of waiting for the disease onset, and the risk of transplant-related mortality associated with allogeneic hematopoietic cell transplantation, which is often performed at a very young age. We first describe the detailed clinical course of an asymptomatic patient with XLP1 who successfully underwent allogeneic hematopoietic cell transplantation. CASE PRESENTATION: A boy was born at 39 weeks of gestation, weighing 3016 g at birth. He appeared fine, but he underwent genetic testing because his maternal cousin had XLP1. He was found to have a novel c.207_208insC (p.Pro70ProfsX4) mutation in exon 3 of SH2D1A, which was also found in his cousin. There was no HLA-identical donor in his family. Immunoglobulin was administered monthly to prevent EBV infection while searching for an alternative donor. He underwent allogeneic bone marrow transplantation (BMT) from an allele HLA 8/8 fully matched, unrelated donor with a reduced-intensity conditioning (RIC) regimen consisting of fludarabine, melphalan, and low-dose total body irradiation (TBI) at 20 months of age. The patient has been doing well for 2 years post transplantation and maintaining complete donor chimerism without any evidence of chronic graft versus host disease. CONCLUSIONS: We describe a case of an asymptomatic patient with XLP1, who successfully underwent unrelated BMT with RIC regimen consisting of fludarabine, melphalan, and 3 Gy TBI. That was well tolerated and successfully generated complete chimerism in every subpopulation. This case delineates the option of allogeneic hematopoietic cell transplantation even in asymptomatic patients with XLP1.

Hematopoietic cell transplantation for myeloid/NK cell precursor acute leukemia in second remission.

Myeloid/natural killer cell precursor acute leukemia (MNKPL) is a rare leukemia subtype characterized by a high incidence of extramedullary infiltration. No appropriate treatment strategy has so far been developed. Acute myelogenous leukemia-type chemotherapy combined with L-Asparaginase is an effective treatment for MNKPL. Hematopoietic cell transplantation is a second option in refractory cases.