Eradicating acute myeloid leukemia in a Mll(PTD/wt):Flt3(ITD/wt) murine model: a path to novel therapeutic approaches for human disease.

The coexpression of the MLL partial tandem duplication (PTD) and the FLT3 internal tandem duplication (ITD) mutations associate with a poor outcome in cytogenetically normal acute myeloid leukemia (AML). In mice, a double knock-in (dKI) of Mll(PTD/wt) and Flt3(ITD/wt) mutations induces spontaneous AML with an increase in DNA methyltransferases (Dnmt1, 3a, and 3b) and global DNA methylation index, thereby recapitulating its human AML counterpart. We determined that a regulator of Dnmts, miR-29b, is downregulated in bone marrow of dKI AML mice. Bortezomib exerted a dose-dependent increase in miR-29b expression in AML blasts ex vivo, followed by decreased Dnmts, reduced proliferation, and increased apoptosis. In vivo, bortezomib was not active against dKI AML, yet liposomal-encapsulated bortezomib, as a single agent, reversed downregulation of miR-29b in vivo and induced a long-term (90-day) disease-free remission in 80% of dKI AML mice that exhibited high leukemic burden at the start of therapy, yet showed no signs of relapse at autopsy. Taken together, these data support that liposomal bortezomib, as a single agent, eradicates Mll(PTD/wt):Flt3(ITD/wt) AML in mouse and may represent a powerful and potentially curative approach to high-risk human disease.

Donor treatment with a multipegylated G-CSF maximizes graft-versus-leukemia effects.

Donor treatment with granulocyle-colony stimulating factor (G-CSF) is known to modulate immune function, characterized by the generation of regulatory myelogenous and T cell populations and Th2 differentiation. Recently, these effects have been shown to be enhanced by pegylation of the G-CSF molecule, which also improves graft-versus-leukemia (GVL) via activation of invariant natural killer (iNK) T cells. We have compared G-CSF bound to a single PEG molecule (monopeg-G-CSF) as used clinically to a G-CSF molecule bound to multiple PEG molecules (multipeg-G-CSF) in major histocompatibility complex (MHC) disparate and matched models of graft-versus-host disease (GVHD) and GVL. We demonstrate that multipeg-G-CSF induces greater levels of progenitor cell, myelogenous, and iNKT cell expansion than monopeg-G-CSF, while inducing similar protection from GVHD. Despite this, multipeg-G-CSF enhanced CTL function in vivo and improved iNKT cell-dependent leukemia clearance. Thus, GVL and GVHD can be further separated after allogeneic stem cell transplantation by mobilization with a multiple-pegylated G-CSF molecule.

Liposome-incorporated Grb2 antisense oligodeoxynucleotide increases the survival of mice bearing bcr-abl-positive leukemia xenografts.

We previously demonstrated that liposome-incorporated antisense oligodeoxynucleotide specific for the grb2 mRNA (L-Grb2) inhibited Grb2 protein expression and the proliferation of bcr-abl-positive leukemia cell lines. To determine whether L-Grb2 has the potential of being a therapeutic modality against bcr-abl-positive leukemia, we studied the tissue distribution of L-Grb2 in normal mice before studying its effects in mice bearing bcr-abl-positive leukemia xenografts. L-Grb2 was widely distributed in the body. The highest tissue concentrations of L-Grb2 were found in the spleen and liver, which are the organs where the tumor mass of bcr-abl-positive leukemia is mainly found. At 4 h post-injection, the amount of L-Grb2 detected per g of tissue was 64 microg in spleen and 50 microg in liver. Intravenous injection of bcr-abl-positive 32D mouse leukemia cells into radiated NOD/scid mice caused a lethal leukemia syndrome; we determined whether L-Grb2 could prolong the survival of mice bearing such xenografts. One day after leukemia cell inoculation, mice received twice weekly intravenous injections of L-Grb2. At an injection dose of 15 mg of L-Grb2 per kg of mouse body weight, 80% of mice treated with L-Grb2 survived to 48 days (end of study) whereas 0% of mice treated with the same dose of liposomal control oligonucleotide survived; the mean survival duration of these groups was 44 and 20 days, respectively. Our data indicate that L-Grb2 prolonged the survival of mice bearing bcr-abl-positive leukemia xenografts. L-Grb2 may be used as a novel cancer therapeutic modality.

Induction of in vitro and in vivo anti-tumor responses by sensitization of mice with liposomes containing a crude butanol extract of leukemia cells and transferred inter-membranously with cell-surface proteins.

Generation of cytotoxic T lymphocytes (CTL) in vitro and tumor-rejection responses by sensitization of semi-syngeneic mice with tumor-antigen-reconstituted liposomes were investigated. Liposomes were prepared from a crude butanol extract (CBE) of BALBRVD leukemia cells and egg phosphatidylcholine (PC): 1,2-dimyristoylamido-1,2-deoxyphosphatidylcholine (DDPC) (3:2) or dimyristoylphosphatidylcholine (DMPC):DDPC (1:4). Inter-membrane protein transfer (IMPT) liposomes were prepared by incubating BALBRVD cells with DMPC:DDPC (1:4) liposomes. Sensitization of male CB6F1 mice with CBE or IMPT liposomes induced a level of cytotoxicity similar to that on sensitization with mitomycin-C(MMC)-treated BALBRVD against BALBRVD target cells after in vitro sensitization with the tumor cells. Sensitization with CBE alone resulted in only marginal cytotoxicity. The cytotoxic effector cells induced by either mode of sensitization were CD8+ T-cells whose recognition was Kd-restricted. No difference in specificity was observed with the different modes of sensitization. Two in vivo immunizations with CBE or with CBE liposomes at a dose of 25 micrograms of protein (equivalent to 2.5 x 10(7) cells) cause moderate inhibition of BALBRVD tumor growth in male CB6F1 mice and immunization with IMPT liposomes at a dose of 1 microgram of protein result in efficient protection.

Antitumor effect of adriamycin entrapped in liposomes conjugated with monoclonal antibody against tumor-associated antigen of bovine leukemia cells.

Monoclonal antibody against tumor-associated antigen (TAA) expressed on bovine leukemia cells was conjugated to liposomes containing adriamycin (ADM), and the specificity and therapeutic effects of the conjugates were examined in vitro and in vivo using a TAA-positive bovine leukemia cell line as the target tumor. In vitro studies with the TAA-positive cell line clearly indicated that the antibody-conjugated liposomes containing ADM exerted selective effects on TAA-positive cells in the inhibition assay of 3H-thymidine incorporation. Three injections of liposomes containing ADM (4 mg/kg) into tumor-bearing nude mice significantly inhibited the tumor growth and the therapeutic effect of the antibody-conjugated liposomes was far greater than that of normal mouse IgG-conjugated liposomes as assessed in terms of tumor size.

Enhanced macrophage and natural killer cell antitumor activity by various molecular weight maleic anhydride divinyl ethers.

A series of Maleic anhydride divinyl ether (MVE) polyanions, synthesized with molecular weight ranging from 12500 to 52600, were found capable of enhancing macrophage tumoricidal activity of MBL-2 leukemia cells. These agents also augmented Natural Killer cell activity against the YAC lymphoma and M109 adenocarcinoma cell lines.

Syngeneic adoptive immunotherapy and chemoimmunotherapy of a Friend leukemia: requirement for T cells.

The aim of the study was to determine which cell mediates adoptive immunotherapy and chemoimmunotherapy of a syngeneic transplantable Friend virus-induced leukemia (FBL-3). An adoptive immunotherapy model was developed in which adult C57BL/6 mice given a lethal dose (10(4)) of FBL-3 on day 0 were saved by treatment on day 1 with C57BL/6 spleen cells or peritoneal exudate cells (PEC) immune to FBL-3. Cells passed through a nylon wool column to remove B cells and macrophages or treated with carbonyl iron to remove phagocytic cells remained effective, whereas cells treated with anti-theta serum and complement were far less effective. For adoptive chemoimmunotherapy, mice inoculated with 10(7) FBL-3 were treated 5 days later with cyclophosphamide (CY) plus immune spleen cells. CY, with or without non-immune cells, prolonged survival but all mice died with leukemia, whereas mice given CY plus immune cells survived tumor-free. As an adjunct to CY, immune cells passed through nylon wool or treated with carbonyl iron remained quite effective whereas cells treated with anti-theta serum and complement were far less effective. Thus, immune thymus-derived lymphocytes were required for the adoptive immunotherapy of an early leukemia or chemoimmunotherapy of a disseminated leukemia.