In vitro and in vivo single-agent efficacy of checkpoint kinase inhibition in acute lymphoblastic leukemia

Background: Although progress in children, in adults, ALL still carries a dismal outcome. Here, we explored the in vitro and in vivo activity of PF-00477736 (Pfizer), a potent, selective ATP-competitive small-molecule inhibitor of checkpoint kinase 1 (Chk1) and with lower efficacy of checkpoint kinase 2 (Chk2). Methods: The effectiveness of PF-00477736 as single agent in B-/T-ALL was evaluated in vitro and in vivo studies as a single agent. The efficacy of the compound in terms of cytotoxicity, induction of apoptosis, and changes in gene and protein expression was assessed using different B-/T-ALL cell lines. Finally, the action of PF-00477736 was assessed in vivo using leukemic mouse generated by a single administration of the tumorigenic agent n-ethyl-n-nitrosourea. Results: Chk1 and Chk2 are overexpressed concomitant with the presence of genetic damage as suggested by the nuclear labeling for \u3b3-H2A.X (Ser139) in 68 % of ALL patients. In human B-and T-ALL cell lines, inhibition of Chk1/2 as a single treatment strategy efficiently triggered the Chk1-Cdc25-Cdc2 pathway resulting in a dose-and time-dependent cytotoxicity, induction of apoptosis, and increased DNA damage. Moreover, treatment with PF-00477736 showed efficacy ex vivo in primary leukemic blasts separated from 14 adult ALL patients and in vivo in mice transplanted with T-ALL, arguing in favor of its future clinical evaluation in leukemia. Conclusions: In vitro, ex vivo, and in vivo results support the inhibition of Chk1 as a new therapeutic strategy in acute lymphoblastic leukemia, and they provide a strong rationale for its future clinical investigation

Human cord blood (hCB)-CD34+ humanized mice fail to reject human acute myeloid leukemia cells.

Since their appearance, humanized mice carrying human immune system seemed promising tools to study the crosstalk between cancer and immunity. The NOD-scidIL2Rgammanull (NSG) mice engrafted with human cord blood (hCB)-CD34+ cells have been proposed to be a valuable tool to reproduce human immune system in mouse. However, the lack of solid evidences on the functionality of their human immune components limits their usage in immune-oncology. We report that (hCB)-CD34+ cells lose their ability to propagate and originate bone marrow-derived human immune cells after two serial transplantations in NSG mice. We demonstrate that transplants of bone marrow patient-derived acute myeloid leukemias (hAMLs) grow very similarly in the humanized (hCB)-CD34+ NSG and parental NSG mice. The similar extent of engraftment and development of leukemias in (hCB)-CD34+ NSG and controls suggests a poor human immune response against not compatible hAMLs. Our findings suggest that (hCB)-CD34+ NSG mice are transient and/or incomplete carriers of the human immune system and, therefore, represent a suboptimal tool to study the interaction between tumor and immune cells

Effects of Positively Selected Sequence Variations in Human and Macaca fascicularis β-Defensins 2 on Antimicrobial Activity

The evolution of orthologous genes coding for β-defensin 2 (BD2) in primates has been subject to positive selection during the divergence of the platyrrhines from the catarrhines and of the Cercopithecidae from the Hylobatidae, great apes, and humans. Three peptides have been selected for a functional analysis of the effects of sequence variations on the direct antimicrobial activity: human BD2 (hBD2), Macaca fascicularis BD2 (mfaBD2), and a variant of the human peptide lacking Asp(4), (−D)hBD2, which is characteristic only of the human/great ape peptides. hBD2 and mfaBD2 showed a significant difference in specificity, the former being more active towards Escherichia coli and the later towards Staphylococcus aureus and Candida albicans. Asp(4) in the human peptide appears to be important, as (−D)hBD2 was less structured and had a markedly lower antimicrobial activity. The evolution of β-defensin 2 in primates may thus have been driven, at least in part, by different environmental pressures so as to modulate antimicrobial activity

A study of host defence peptide beta-defensin 3 in primates

We have investigated the molecular evolution of the gene coding for beta-defensin 3 (DEFB103) in 17 primate species including humans. Unlike the DEFB4 genes (coding for beta-defensin 2) [Boniotto, Tossi, Del Pero, Sgubin, Antcheva, Santon and Masters (2003) Genes Immun. 4, 251-257], DEFB103 shows a marked degree of conservation in humans, Great Apes and New and Old World monkeys. Only the Hylobates concolor defensin hcBD3 showed an amino acid variation Arg(17)-->Trp(17) that could have a functional implication, as it disrupts an intramolecular salt bridge with Glu(27), which locally decreases the charge and may favour dimerization in the human congener hBD3. This is thought to involve the formation of an intermolecular salt bridge between Glu(28) and Lys(32) on another monomer [Schibli, Hunter, Aseyev, Starner, Wiencek, McCray, Tack and Vogel (2002) J. Biol. Chem. 277, 8279-8289]. To test the role of dimerization in mediating biological activity, we synthesized hBD3, hcBD3 and an artificial peptide in which the Lys(26)-Glu(27)-Glu(28) stretch was replaced by the equivalent Phe-Thr-Lys stretch from human beta-defensin 1 and we characterized their structure and anti-microbial activity. Although the structuring and dimerization of these peptides were found to differ significantly, this did not appear to affect markedly the anti-microbial potency, the broad spectrum of activity or the insensitivity of the anti-microbial action to the salinity of the medium