ALBERT

Description: Even though quartic force fields (QFFs) and highly accurate coupled cluster computations describe the OCHCO + cation at equilibrium as a complex between carbon monoxide and the formyl cation, two notable and typical interstellar and atmospheric molecules, the prediction from the present study is that the equilibrium C ∞ v structure is less relevant to observables than the saddle-point D ∞ h structure. This is the conclusion from diffusion Monte Carlo and vibrational self-consistent field/virtual state configuration interaction calculations utilizing a semi-global potential energy surface. These calculations demonstrate that the proton “rattle” motion ( ν 6 ) has centrosymmetric delocalization of the proton over the D ∞ h barrier lying only 393.6 cm −1 above the double-well OCHCO + C ∞ v minima. As a result, this molecule will likely appear D ∞ h , and the rotational spectrum will be significantly dimmer than the computed equilibrium 2.975 D center-of-mass dipole moment indicates. However, the proton transfer fundamental, determined to be at roughly 300 cm −1 , has a very strong intensity. This prediction as well as those of other fundamentals should provide useful guides for laboratory detection of this cation. Finally, it is shown that the two highest energy QFF-determined modes are actually in good agreement with their vibrational configuration interaction counterparts. These high-level quantum chemical methods provide novel insights into this fascinating and potentially common interstellar molecule.

Description: Acute or chronic leukemias resist apoptosis in vitro when co-cultured with marrow stromal cells, suggesting that the growth/survival of leukemia cells relies in part on interactions with stromal cells in the microenvironment. We have recently demonstrated that consistent and high-level engraftment of human primary leukemia obtained from patients can be achieved in NOD/scid mice by preconditioning with either adherent cord blood or marrow mesenchymal stem cells. High success rate of engraftment (84.9 ± 2.9 % leukemia blasts in mouse marrow) was obtained with many lineages of leukemia including acute T- or B-cell lymphoblastic and myeloid leukemia. In general, leukemia blasts were detectable in peripheral blood of mice by week 4–5, leading to fatal outcome by week 6 (42 ± 4 days). Furthermore, cells from the marrow of these preconditioned mice were found to secrete leukemia-promoting activities, suggesting that the mouse marrow had been altered to favor the proliferation/survival of leukemic cells in vivo. We also showed that the human leukemia cells harvested from mice could be serially transferred to other mice for many generations with ~100 fold increase in the number of leukemic and clonogenic cells in mice, while retaining properties similar to primary leukemia samples obtained from patients. Several lines of evidence in our studies including the appearance of leukemia blasts in marrow and blood, the dissemination to other tissues, and gene expression profiling in microarray analysis confirm that this xenograft model recapitulates key features of human leukemia. Furthermore, weekly i.p. injections of NOD/scid mice with vincristine at 0.5 mg/kg for three weeks, starting at second week after inoculation of patients primary leukemia, resulted in a significant delay in the appearance of human leukemia blasts in blood, doubly the length of mouse survival. In addition, pairs of primary leukemia samples collected at diagnosis and at relapse from the same patients were engrafted into NOD/scid mice. The NOD/scid mice transplanted with either samples developed leukemia in mouse peripheral blood at week 4–5 with similar kinetics after inoculation. However, weekly vincristine treatment x 3 of the mice transplanted with diagnosis leukemia samples, prevented the appearance of leukemia blast cells in the circulating peripheral blood for at least 5 weeks. In contrast, similar treatment of mice engrafted with relapse leukemia samples had 50% leukemia blasts in blood at week 5 and subsequently developed fatal leukemia dissemination at week 7. These findings indicate that this robust high level engraftment model of human primary leukemia may be useful in predicting clinical response to chemotherapy. Evidence has further suggested that these human leukemia in NOD/scid mice may be derived from a small subset of immature stem cells in the samples that give rise to leukemia expansion and phenotypic diversity in these mice. Therefore, we had developed a robust and predictive animal model of human primary leukemia, which is valuable for studying leukemia stem cells and for testing or prioritizing new agents/regimens in vivo.

Description: The deficiency of methylthioadenosine phosphorylase (MTAP) in T-cell acute lymphoblastic leukemia (T-ALL) and other cancers, while constitutively expressed in normal cells, allows for selective therapy using L-alanosine, an inhibitor of de novo AMP synthesis. We demonstrate that MTAP- T-ALL cells obtained at relapse are as sensitive to L-alanosine toxicity as diagnosis samples. The therapeutic index of L-alanosine can be increased by the use of a MTAP substrate, which protects MTAP+ normal cells. Since MTAP substrates MTA and 5′deoxyadenosine are prone to toxicities associated with adenosine, we synthesized and evaluated a potentially nontoxic MTAP substrate, 9-β-D-erythrofuranosyladenine (EFA). The cytotoxicity of EFA to hematopoietic progenitors erythroid burst-forming units (BFU-Es) and granulocyte-macrophage colony-forming units (CFU-GMs) was at least 26- to 41-fold less than that of MTA. In addition, EFA selectively rescued MTAP+ MOLT-4 cells from L-alanosine toxicity at 25 μM with negligible toxicity even at 100 μM. As for MTA, significant, albeit incomplete, rescue was achieved at 12.5 μM, but higher concentrations were toxic. EFA at 20 μM or less rescued primary MTAP+ T-ALL cells and normal lymphocytes from L-alanosine toxicity. Collectively, these data indicate that EFA is an effective agent for salvaging MTAP+ cells from L-alanosine toxicity and is superior to MTA due to lower cytotoxicity.

Description: Childhood T-cell acute lymphoblastic leukemia (T-ALL) is one of the most common childhood cancers. It is reported that preconditioning sublethally irradiated immunodeficient NOD/SCID (nonobese diabetic/X-linked severe combined immunodeficient) mice with human cord blood mononuclear cells facilitates the engraftment, expansion, and dissemination in these mice of primary T-ALL cells obtained from patients at the time of diagnosis. Cells recovered from mouse bone marrow or spleen resembled the original leukemia cells from patients with respect to surface lineage markers and T-cell receptor Vβ gene rearrangements. Moreover, the pattern of leukemia dissemination in mouse tissues, resulting in universally fatal leukemia, is reminiscent of the human clinical disease. In addition, the fidelity of the model to the human disease is documented with regard to the presence of morphologically identifiable human leukemia cells in mouse bone marrow and blood and the maintenance of leukemia-initiating capacity within the leukemia-engrafted mouse. Therefore, several lines of independent approaches are used to suggest that the engrafted cells are of human leukemia origin and are not derived from cord blood. The in vivo model described here should enable the study of the growth properties of primary T-ALL cells obtained from patients and should prove useful in evaluating the potential efficacy of therapeutic strategies directed toward T-ALL.

Description: The novel prodrug of butyric acid, pivaloyloxymethyl butyrate (AN-9), a histone deacetylase inhibitor, shows great promise as an effective and relatively nontoxic anticancer agent for solid malignancies. However, little is known about its effects on hematopoietic malignancies. In this study, we show that 21 primary samples of acute leukemia were sensitive to the antiproliferative effects of AN-9, with a 50% inhibitory concentration (IC50) of 45.8 ± 4.1 μM. In colony-forming assays, primary T-cell acute lymphoblastic leukemia (T-ALL) cells were 3-fold more sensitive to AN-9 than the normal hematopoietic progenitors, erythroid burst-forming units and granulocyte/monocyte colony-forming units. AN-9 induced apoptosis in the T-ALL cell line CEM. A common problem with cancer is chemoresistance, which is often typical of relapsed cancers. Remarkably, a T-ALL sample at diagnosis and an acute myeloid leukemia sample at relapse that were resistant to doxorubicin in vitro were sensitive to AN-9, with an IC50 of 50 μM for both samples. More strikingly, samples from 2 infants with t(4;11) ALL obtained at diagnosis and relapse each were the most sensitive to AN-9, with IC50values of 25 μM and 17 μM, respectively. Furthermore, a doxorubicin-resistant clone of HL60, HL60/ADR, obtained by the transfection of the MDR-1 gene, was equally sensitive to AN-9 cytotoxicity as the parental cells. AN-9 induced the expression of p21 in an infant leukemia sample with 11q23 rearrangement, but not in T- or B-precursor ALL. Collectively, our results suggest that AN-9 is a selective agent for hematopoietic malignancies that can circumvent the mechanisms of chemoresistance limiting most conventional chemotherapy.