Small molecule inhibition of cAMP response element binding protein in human acute myeloid leukemia cells.

The transcription factor CREB (cAMP Response-Element Binding Protein) is overexpressed in the majority of acute myeloid leukemia (AML) patients, and this is associated with a worse prognosis. Previous work revealed that CREB overexpression augmented AML cell growth, while CREB knockdown disrupted key AML cell functions in vitro. In contrast, CREB knockdown had no effect on long-term hematopoietic stem cell activity in mouse transduction/transplantation assays. Together, these studies position CREB as a promising drug target for AML. To test this concept, a small molecule inhibitor of CREB, XX-650-23, was developed. This molecule blocks a critical interaction between CREB and its required co-activator CBP (CREB Binding Protein), leading to disruption of CREB-driven gene expression. Inhibition of CBP-CREB interaction induced apoptosis and cell-cycle arrest in AML cells, and prolonged survival in vivo in mice injected with human AML cells. XX-650-23 had little toxicity on normal human hematopoietic cells and tissues in mice. To understand the mechanism of XX-650-23, we performed RNA-seq, ChIP-seq and Cytometry Time of Flight with human AML cells. Our results demonstrate that small molecule inhibition of CBP-CREB interaction mostly affects apoptotic, cell-cycle and survival pathways, which may represent a novel approach for AML therapy.

Renal clear-cell carcinoma: an ultrastructural study on the junctional complexes.

Junctional complexes such as tight junctions, adherens junctions, and desmosomes play crucial roles in the structure and function of epithelial cells. These junctions are involved in increasing cell-cell contact and as well serve as signaling centers regulating multiple functions in epithelial cells. Carcinoma cell lines cultured in the laboratory generally lack junctional complexes. However, studies directed towards understanding the distribution of junctional complexes in human cancer tissues are lacking. In this study, we analyzed by electron microscopy the distribution of junctional complexes in patients diagnosed with renal clear-cell carcinoma. We found that both tight junctions and adherens junctions were drastically reduced in patients with cancer compared to normal tissues. Desmosomes were not detected in normal proximal tubules while distinctly present in cancer tissues. These results suggest that analysis of junctional complexes in human tumors should provide valuable information that might have prognostic and diagnostic value.

A model-based approach for assessing in vivo combination therapy interactions.

We present an approach for evaluating the efficacy of combination antitumor agent schedules that accounts for order and timing of drug administration. Our model-based approach compares in vivo tumor volume data over a time course and offers a quantitative definition for additivity of drug effects, relative to which synergism and antagonism are interpreted. We begin by fitting data from individual mice receiving at most one drug to a differential equation tumor growth/drug effect model and combine individual parameter estimates to obtain population statistics. Using two null hypotheses: (i) combination therapy is consistent with additivity or (ii) combination therapy is equivalent to treating with the more effective single agent alone, we compute predicted tumor growth trajectories and their distribution for combination treated animals. We illustrate this approach by comparing entire observed and expected tumor volume trajectories for a data set in which HER-2/neu-overexpressing MCF-7 human breast cancer xenografts are treated with a humanized, anti-HER-2 monoclonal antibody (rhuMAb HER-2), doxorubicin, or one of five proposed combination therapy schedules.

Thrombotic microangiopathy following allogeneic bone marrow transplantation is associated with intensive graft-versus-host disease prophylaxis.

Thrombotic microangiopathy (TM), manifesting clinically as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, is an uncommon complication after bone marrow transplantation (BMT). A retrospective analysis of potential risk factors for TM following allogeneic BMT was performed. Clinical data were analyzed from seven patients diagnosed with severe TM and 409 patients who underwent BMT during the same time period and who survived for at least 100 days afterwards. Six of the seven patients with TM received intensive GVHD prophylaxis consisting of cyclosporine, methotrexate and glucocorticoids, whereas only 66 of the 409 patients without TM received this regimen (P < 0.001, Fisher's exact test). This regimen was administered to patients older than 40 years, or recipients of a mismatched or unrelated allograft. Univariate analysis also revealed an increased risk of TM associated with the use of an unrelated bone marrow donor (P = 0.02), but no significant association with patient age or gender, diagnosis, amount of prior chemotherapy, transplant conditioning regimen or severity of GVHD. A multivariate exact logistic regression analysis revealed that only the type of GVHD prophylaxis had a significant impact on the risk for TM. The combined use of cyclosporine, methotrexate and glucocorticoids as GVHD prophylaxis may predispose to the development of TM following BMT.

Interictal seizure resections show two configurations of endothelial Glut1 glucose transporter in the human blood-brain barrier.

Immunogold electron microscopy was used to analyze and quantify the Glut1 glucose transporter in brain tissue from five patients undergoing surgery for treatment of seizures. Samples were prepared from two different regions of each resection: (1) the most actively spiking epileptogenic site, and (2) the least actively spiking region, as indicated by intraoperative EEG monitoring. Two configurations of endothelial cell Glut1 were observed. About one half of the capillary profiles examined displayed abundant Glut1 immunoreactivity on both luminal and abluminal endothelial membranes. In the remainder of the profiles, reduced Glut1 labeling was seen, but adjacent erythrocyte membranes remained highly Glut1 immunoreactive, suggesting that reduced endothelial Glut1 reactivity was not attributable to method artifacts. Immunogold studies using antisera to human glial fibrillary acidic protein and human serum albumin demonstrated increased quantities of these two epitopes in the extravascular regions in which more EEG spiking activity had been demonstrated. These observations were consistent with the hypotheses that capillary integrity was more compromised, and gliosis was quantitatively increased, in the more actively spiking region of the resection. Altered glucose transporter activity in the blood-brain barrier was characterized by a bimodal Glut1 distribution in which the smaller (type B) endothelial cells displayed low Glut1 immunoreactivity, whereas adjacent (and even contiguous) larger (type A) endothelial cells showed 5- to 10-fold greater expression of membrane Glut1 transporter protein. Because this transporter facilitates glucose entry to the brain, small pericapillary volumes of brain tissue may have quite different concentrations of glucose. We hypothesize that in complex partial seizures and other forms of brain insult, an alteration of blood-brain barrier Glut1 glucose transporter activity is indicated by the appearance of these two subpopulations of endothelial cells. In comparison with previous studies of human brain capillaries in hemangioblastoma and brain injury, endothelial Glut1 density was apparently reduced (interictally) in affected temporal lobes of patients with complex partial seizures.

Estimation of the DNA sequence discriminatory ability of hairpin-linked lexitropsins.

Three- and four-ring polyamides containing N-methylimidazole and N-methylpyrrole, and their hairpin-linked derivatives, bind side-by-side in the minor groove of DNA in a sequence-specific manner. The sequences recognized by side-by-side molecules are dependent on the pairings of the polyamide rings to the bases. In this study we report a mathematical model for estimating the free energies of binding for gamma-aminobutyric acid-linked polyamides to 5- and 6-bp DNA sequences. The model parameters are calibrated by a least-squares fit to 35 experimental binding constants. The model performs well in cross-validation experiments and the parameters are consistent with previously proposed empirical rules of polyamide-DNA binding. We apply the model to the design of targeted polyamides, evaluating the ability of the proposed polyamides to bind to a DNA sequence of interest while minimizing binding to the remaining DNA sequences.

Suramin in hormone-refractory metastatic prostate cancer: a drug with limited efficacy.

PURPOSE: To confirm the previously reported high response rates and prolonged survival in hormone-refractory prostate cancer treated with suramin. PATIENTS AND METHODS: Thirty-six eligible patients with hormone-refractory prostate cancer with either measurable disease or bone disease only and a prostate-specific antigen (PSA) level greater than 50 ng/mL were enrolled. Treatment consisted of two 8-week courses of outpatient-based therapy with an interposed rest period. A bayesian adaptive control strategy and a three-compartment pharmacokinetic model that accommodates clearance changes was used to guide individual dosing. A rapid infusion of 1,000 mg/m2 suramin was followed by five daily infusions that targeted 285 micrograms/mL peak plasma levels during the first week. All patients received concomitant hydrocortisone. For the next 7 weeks, patients received one to two doses per week that targeted levels in the 150 to 285 micrograms/mL range and integrated weekly averages of 200 ug/mL. RESULTS: Nine patients (28%) had a partial response to suramin based on a > or = 50% decrease in PSA levels coupled with either relief of bone pain or by a 50% decrease in measurable disease. The median overall survival time for all patients is 31 weeks (95% confidence interval [CI], 23 to 51). Treatment was generally well tolerated, with fatigue being the most common significant toxicity, but fatal idiosyncratic myelosuppression (grade V) was observed in one patient. CONCLUSION: Using this dosing schedule, suramin has limited activity against hormone-refractory metastatic prostate cancer. Recent data suggest that hydrocortisone administered with suramin may be partly responsible for the benefit attributed to the drug. Although a small cohort of patients appeared to benefit, we were unable to confirm the previously reported high rate of activity and durability of remission using this agent.

Unrelated donor bone marrow transplants in children.

Only a small proportion of children who might benefit from bone marrow transplant (BMT) have an HLA-identical sibling. To provide this potentially curative therapy to patients without a matched related donor, marrow transplants using less well matched related donors or unrelated donors (identified through computerized donor registries) have been performed. We report the outcome of 24 consecutive unrelated donor BMT's performed on children. Eligible diagnosis included acute leukemia (AL) (n = 15), chronic myelogenous leukemia (CML) (n = 4), myelodysplastic syndrome (MDS) (n = 3), and severe aplastic anemia (SAA) (n = 2). All donor/recipient pairs were sero-matched at 5 or 6 of the 6 HLA A, B, and DR antigens. Several different preparative regimens were used, but fractionated total body irradiation (TBI) was used in 20 patients. All recipients received graft-versus-host-disease (GVHD) prophylaxis with cyclosporine-A (CSA), four with short course methotrexate (MTX), 14 in combination with short course MTX and methylprednisolone (MPS), and five in combination with a mouse monoclonal antibody to CD5, coupled to the A-chain of ricin (Xomazyme-65). One patient received CSA and MPS alone after a T-cell depleted marrow transplant. Twenty of 23 evaluable recipients engrafted (87%). Two patients with CML never engrafted and had autologous marrow recovery, one patient with SAA died at 128 days without evidence of engraftment, and there was one early death at day + 9. Fourteen of 20 patients (70%) with stable donor-derived hematopoiesis developed significant acute GVHD > or = grade II). Eleven of 15 engrafted patients who survived > 100 days after BMT developed chronic GVHD (73%).(ABSTRACT TRUNCATED AT 250 WORDS)

N-ras mutations are associated with poor prognosis and increased risk of leukemia in myelodysplastic syndrome.

To evaluate the clinical significance of N-ras mutations in the myelodysplastic syndrome (MDS) archival bone marrow samples from 252 patients were studied for the presence of N-ras exon I mutations using polymerase chain reaction amplification and differential oligonucleotide hybridization. Subsequently, clinical information about these patients was obtained and analyzed. Of 220 evaluable patients, 20 (9%) had point mutation of N-ras involving codon 12. Individuals with N-ras mutation had a significantly shorter survival period than those who were N-ras negative (P = .02). An increased risk of acute myelogenous leukemia (AML) was also found in patients with N-ras mutations (P = .005). N-ras mutations were not associated with any French-American-British (FAB) subtype, with the presence of increased myeloblasts, or with chromosomal aberrations in the bone marrow. However, the presence of increased bone marrow blasts was strongly associated with poor survival rate and risk of AML (P < .001 for each). After stratifying for the percentage of blasts, N-ras mutations remained significantly associated with shorter survival period (P = .04) and increased risk of AML (P = .02). Bone marrow cytogenetic abnormalities, particularly when multiple abnormalities were present, were significantly associated with a poor prognosis (P < .001). In conclusion, N-ras mutation, although relatively infrequent in MDS, is associated with short survival period and increased probability of developing AML.

Pharmacologic effects in vivo in brain by vector-mediated peptide drug delivery.

Pharmacologic effects in brain caused by systemic administration of neuropeptides are prevented by poor transport of the peptide through the brain vascular endothelium, which comprises the blood-brain barrier in vivo. In the present study, successful application of a chimeric peptide approach to enhance drug delivery through the blood-brain barrier for the purpose of achieving a central nervous system pharmacologic effect is described. The chimeric peptide was formed by linkage of a potent vasoactive intestinal peptide (VIP) analogue, which had been monobiotinylated, to a drug transport vector. The vector consisted of a covalent conjugate of avidin and the OX26 monoclonal antibody to the transferrin receptor. Owing to the high concentration of transferrin receptors on brain capillary endothelia, OX26 targets brain and undergoes receptor-mediated transcytosis through the blood-brain barrier. Systemic infusion of low doses (12 micrograms/kg) of the VIP chimeric peptide in rats resulted in an in vivo central nervous system pharmacologic effect: a 65% increase in cerebral blood flow. Biotinylated VIP analogue without the brain transport vector was ineffective.

Hemolysis of transfused group O red blood cells in minor ABO-incompatible unrelated-donor bone marrow transplants in patients receiving cyclosporine without posttransplant methotrexate.

Hemolysis most commonly occurs following bone marrow transplant when there is "minor" ABO blood group incompatibility between donor and recipient. The hemolysis has been attributed to destruction of the patient's incompatible erythrocytes by donor-derived anti-A and/or anti-B antibody produced from "passenger" immunocompetent donor lymphocytes. Extraordinary transfusion requirements of group O erythrocytes in a series of patients receiving unrelated minor ABO-incompatible marrow grafts led us to investigate whether this mechanism could account for the extent of hemolysis observed. In seven consecutive minor ABO-incompatible unrelated-donor bone marrow transplant recipients receiving cyclosporine without posttransplant methotrexate, we observed excessive hemolysis. For cases in this index group, a strongly reactive donor-derived ABO blood group antibody was identified coincident with development of hemolysis. Transfusion requirements in the first three patients (26 U of group O erythrocytes each) greatly exceeded the recipient's volume of incompatible erythrocytes, indicating that lysis of transfused group O erythrocytes was also occurring. Pretransplant erythrocyte exchange transfusion with group O erythrocytes performed in the four subsequent patients decreased the severity of hemolysis, but did not prevent it. Among minor ABO-incompatible marrow graft recipients, an analysis of variance demonstrated effects on transfusion requirements due to donor-recipient relationship being unrelated (P less than .002) and the use of posttransplant methotrexate (P = .0001), and there was interaction between these two factors (P less than .001). Bone marrow transplants from unrelated donors resulted in an exaggerated immune response to ABO blood group antigens, which was associated with hemolysis of transfused group O erythrocytes, as well as the patient's ABO-incompatible erythrocytes. This serious complication may be prevented by posttransplant immunosuppression with methotrexate.

Persistence of insulin resistance in polycystic ovarian disease after inhibition of ovarian steroid secretion.

Six nonobese women with polycystic ovarian disease (PCOD) showed significant hyperinsulinemia, compared with controls after oral glucose (P less than 0.05). As an indicator of insulin sensitivity, in vitro proliferation of erythrocyte progenitor cells of PCOD subjects exposed to physiologic concentrations of insulin was significantly blunted (P less than 0.001). Monocyte insulin receptor binding was not impaired in the PCOD subjects. Three of the PCOD patients were treated with a long-acting gonadotropin-releasing hormone agonist for 6 months, which resulted in marked suppression of ovarian androgen secretion but no demonstrable changes in in vivo or in vitro indicators of insulin resistance. Thus insulin resistance in PCOD subjects appears to be unrelated to ovarian hyperandrogenism (or acanthosis or obesity). Although certain tissues are insulin-resistant in PCOD patients, the ovary may remain sensitive and overproduce androgens in response to high circulating insulin levels.

Tracer kinetic model of blood-brain barrier transport of plasma protein-bound ligands. Empiric testing of the free hormone hypothesis.

Previous studies have shown that the fraction of hormone or drug that is plasma protein bound is readily available for transport through the brain endothelial wall, i.e., the blood-brain barrier (BBB). To test whether these observations are reconcilable with the free-hormone hypothesis, a tracer-kinetic model is used in the present investigations to analyze in vivo initial extraction data on BBB transport of protein-bound steroid hormones (dihydrotestosterone, testosterone, estradiol, and corticosterone), thyroid hormones (triiodothyronine), and lipophilic amine drugs (propranolol). The plasma proteins used are bovine albumin and human orosomucoid. Transport data was fit to a modification of the Kety-Renkin-Crone equation of capillary physiology; the modified equation incorporates the principles of both capillary physiology and plasma protein-ligand mass action binding relationships. In most cases, the experimental data is best fit to the model equation when the apparent in vivo dissociation constant, KDa, of the ligand protein binding reaction increases to values that are 5- to 50-fold greater than the in vitro dissociation constant, KD. This result indicates that the rate of ligand dissociation from the plasma protein is accelerated in the capillary bed relative to the in vitro situation. It is hypothesized that the major factor leading to the rapid transport in vivo of protein-bound ligands into tissues such as brain is an endothelial-induced decrease in the affinity of the plasma protein for the ligand. Under these conditions, the amount of plasma ligand available for tissue clearance in vivo parallels the protein-bound fraction, not the free hormone.

Test of models for replication of simian virus 40 DNA following ultraviolet irradiation.

When mammalian cells are irradiated with ultraviolet light, semiconservative DNA replication is inhibited and the length of newly synthesized daughter strands is reduced. We have used the simian virus 40 (SV40) viral system to examine the molecular mechanism by which this inhibition of DNA replication occurs immediately following ultraviolet irradiation. We tested two models for DNA replication-inhibition by using a procedure first developed by Danna, K. J., and D. Nathans (1972, Proc. Natl. Acad. Sci. USA, 69:3097-3100) in which the distribution of 3H-label in segments of newly completed SV40 form-I molecules is measured after short pulse labeling with 3H-thymidine. Our experimental results were compared with those predicted by mathematical models that describe two possible molecular mechanisms of replication inhibition. Our data are best fit by a "blockage" model in which any pyrimidine dimer encountered by the replication fork prevents complete replication of the SV40 genome. An alternative model called "slowdown" in which DNA damage causes a generalized slowdown of replication fork movement on all genomes has more adjustable parameters but does not fit the data as well as the blockage model.