Meeting Report: Fifth Annual AACR Frontiers in Cancer Prevention Research

Addressing genetics, risk modeling, molecular targets for chemoprevention, clinical prevention trials, behavioral prevention research, public policy, and more, the Fifth Annual International Conference on Frontiers in Cancer Prevention Research, held in Boston, Massachusetts, in November 2006, added an outstanding new chapter to the landmark AACR Frontiers program for advancing the science and practice of cancer prevention throughout the world.     

Expulsion of the gastrointestinal cestode, Hymenolepis diminuta by tolerant rats: evidence for mediation by a Th2 type immune enhanced goblet cell hyperplasia, increased mucin production and secretion

The processes underlying expulsion of Hymenolepis diminuta in rats are not known. Expression levels of mRNAs of several cytokines revealed a Th2 response that differed between worm infection levels. IL-4 protein levels decreased while IL-13 levels increased in a 50-worm infection by 30 dpi; the converse was seen with a five-worm infection. A negative correlation was found between IL-4 or IL-13 mRNA expression and worm biomass, between IL-13 protein levels and worm number or worm biomass, and between IL-4 protein levels and worm biomass in 50-worm infections. A negative correlation between IL-4 mRNA or protein expression and worm biomass was observed with five-worm infections. A strong correlation between Muc2 mRNA expression and decreased worm number or biomass in a 50-worm infection was observed. Muc2 protein, goblet cell numbers and mucin decreased in a 50-worm infection by 20 days post-infection. These changes were not seen with five-worm infections where worms are not expelled. The data show that rats infected with 50 H. diminuta mount a Th2 response leading to high levels of IL-13, increased goblet cell numbers and increased mucin2 production and release. The mucus traps the worms, which are progressively expelled from the small intestine.     

Conformational comparisons of a series of tachykinin peptide analogs

Previous studies have shown differences in the biological activity and the structure of two naturally occurring tachykinin peptides, substance P (SP, RPKPQQFFGLM-NH2) and ranatachykinin C (RTKC, HNPASFIGLM-NH2). To further understand the basis for these differences, four analogs that selectively incorporate the amino acid differences between SP and RTKC have been synthesized for study. The four peptide analogs studied have the following amino acid sequences: SP2-11, also known as des-Arg SP (PKPQQFFGLM-NH2); Q5A-SP (RPKPAQFFGLM-NH2); Q6S-SP (RPKPQSFFGLM-NH2); and Q5AQ6S-SP (RPKPASFFGLM-NH2). Nuclear magnetic resonance spectroscopy and molecular modeling calculations were performed on SP, RTKC, SP2-11, Q5A-SP, Q6S-SP, and Q5AQ6S-SP to compare their conformational differences and similarities in the presence of the membrane mimetic system sodium dodecyl sulfate. The molecular modeling data of the analogs Q5A-SP and Q6S-SP show residues 1-3 have a random conformation and residues 4-8 have a helical structure, while the C-terminus contains a poly C7 conformation that is similar to SP but different from RTKC. The molecular modeling data of the analogs SP2-11 and Q5AQ6S-SP show a continuous helix conformation for residues 4-11 at the C-terminus, which is different from SP but similar to RTKC. These structural differences are related to the functional differences of binding of the peptides at the SP receptor (NK1).     

Near-haploid acute lymphoblastic leukemia: a unique subgroup with a poor prognosis?

We describe two adolescent girls with acute lymphoblastic leukemia (ALL) whose leukemia cells were near-haploid. Their lymphoblasts stained in a block pattern with periodic acid Schiff and had "common ALL" surface markers confirmed by indirect immunofluorescence. Each patient had two populations of blasts, one near-haploid and one hyperdiploid, which was an exact doubling of the near-haploid karyotype. The first patient had a predominant population of cells with 26 chromosomes and a few with 52, while the second had a predominance of cells with 56 and a minority with 28. Flow cytometric analysis of DNA content initially detected the minor near-haploid population in the second patient, which was confirmed later by cytogenetic review of the marrow sample. In addition to our two patients, only four patients have been reported with near-haploid ALL. Of these six, five were girls, five were adolescents, and five had short survivals (median, 10 mo). All six had disomy of chromosome 21 with or without disomy for chromosomes 10, 14, 18, or X (four patients each). Thus, near-haploid ALL may represent a unique subgroup of ALL with a poor prognosis. To detect these and other possible subgroups, we have included cytogenetic analysis and flow cytometric analysis of DNA content in our initial evaluation of patients with ALL.     

Role of Drug Efflux and Uptake Transporters in Atazanavir Intestinal Permeability and Drug-Drug Interactions

Purpose

To investigate the role of membrane-associated drug transporters in regulating the intestinal absorption of the HIV-1 protease inhibitor, atazanavir, and assess the potential contribution of these transporters in clinical interactions of atazanavir with other protease inhibitors and tenofovir disoproxil fumarate (TDF).

Methods

Intestinal permeability of atazanavir was investigated in vitro, using the Caco-2 cell line system grown on Transwell inserts, and in situ, by single-pass perfusion of rat intestinal segments, jejunum and ileum, in the absence or presence of standard transporter inhibitors or antiretroviral drugs.

Results

Atazanavir accumulation by Caco-2 cells was susceptible to inhibition by P-glycoprotein and organic anion transporting polypeptide (OATP) family inhibitors and several antiretroviral drugs (protease inhibitors, TDF). The secretory flux of atazanavir (basolateral-to-apical P_app) was 11.7-fold higher than its absorptive flux. This efflux ratio was reduced to 1.5–1.7 in the presence of P-glycoprotein inhibitors or ritonavir. P-glycoprotein inhibition also resulted in 1.5–2.5-fold increase in atazanavir absorption in situ. Co-administration of TDF, however, reduced atazanavir intestinal permeability by 13–49%, similar to the effect observed clinically.

Conclusions

Drug transporters such as P-glycoprotein and OATPs regulate intestinal permeability of atazanavir and may contribute to its poor oral bioavailability and drug-drug interactions with other protease inhibitors and TDF.     

Strategies for tumor-directed delivery of siRNA

INTRODUCTION: Current treatment of malignant tumors relies predominantly on chemotherapy delivering a single antineoplastic drug or a combination of two or more drugs intravenously. Problems with such treatments can include the killing of healthy cells, adverse side effects and chemoresistance. As cancer basically results from different types of mutation leading to the overexpression or suppression of the signaling cascades responsible for cancer cell survival and proliferation, tailor-made approaches capable of interfering precisely with those pathways are the potential revolutionary tools that could pave the way for highly effective cancer therapy. AREAS COVERED: This review summarizes recent progress in the identification and validation of the target genes for cancer gene therapy using small interfering RNA (siRNA) technology and, more importantly, the delivery strategies that have been designed and implemented for tumor-directed delivery of siRNAs. EXPERT OPINION: Cancer-targeted delivery of a gene in order to produce a particular protein (such as a tumor-suppressor or a nucleic acid sequence that can silence the expression of a specific gene, such as an oncogene or an antiapoptotic gene) is the most promising concept for cancer treatment in the future. siRNA has the ability to recognize and cleave a specific mRNA, thus inhibiting the expression of a particular protein. The success of targeted gene silencing as a potential cancer therapeutic demands the development of more effective delivery devices and the removal of siRNA off-target effects.     

Emergence of multidrug-resistant NDM-1-producing Gram-negative bacteria in Bangladesh

The main objective of this study was to investigate the prevalence of bla (NDM-1) in Gram-negative bacteria in Bangladesh. In October 2010 at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) laboratories, 1,816 consecutive clinical samples were tested for imipenem-resistant Gram-negative organisms. Imipenem-resistant isolates were tested for the bla (NDM-1) gene. Among 403 isolates, 14 (3.5?%) were positive for bla (NDM-1), and the predominant species were Klebsiella pneumoniae, Acinetobacter baumannii, and Escherichia coli. All bla (NDM-1)-positive isolates were resistant to multiple antibiotics. Among β-lactamase genes, bla (CTX-M-1-group) was detected in ten isolates (eight bla (CTX-M-15)), bla (OXA-1-group) in six, bla (TEM) in nine, bla (SHV) in seven, and bla (VIM) and bla (CMY) in two isolates each. The 16S rRNA methylase gene, armA, was detected in five?K. pneumoniae isolates and in one E. coli isolate. rmtB and rmtC were detected in a Citrobacter freundii and two?K. pneumoniae isolates, respectively. qnr genes were detected in two?K. pneumoniae isolates (one qnrB and one qnrS) and in an E. coli isolate (qnrA). Transferable plasmids (60-100?MDa) carrying bla (NDM-1) were detected in 7 of the 11 plasmid-containing isolates. Pulsed-field gel electrophoresis (PFGE) analysis grouped K. pneumoniae isolates into three clusters, while E. coli isolates differed significantly from each other. This study reports that approximately 3.5?% of Gram-negative clinical isolates in Bangladesh are NDM-1-producing.     

New advances in the pathophysiology of intestinal ion transport and barrier function in diarrhea and the impact on therapy

Diarrhea remains a continuous threat to human health worldwide. Scaling up the best practices for diarrhea prevention requires improved therapies. Diarrhea results from dysregulation of normal intestinal ion transport functions. Host-microbe contact is a key determinant of this response. Underlying mechanisms in the disease state are regulated by intracellular signals that modulate the activity of individual transport proteins responsible for ion transport and barrier function. Similarly, virulence factors of pathogens and their complex interaction with the host has shed light on the mechanism of enteric infection. Great advances in our understanding of the pathophysiologic mechanisms of epithelial transport, and host-microbe interaction have been made in recent years. Application of these new advances may represent strategies to decrease pathogen attachment, enhance intestinal cation absorption, decrease anion secretion and repair barrier function. This review highlights the new advances and better understanding in the pathophysiology of diarrheal diseases and their impact on therapy.     

In utero arsenic exposure is associated with impaired thymic function in newborns possibly via oxidative stress and apoptosis

Prenatal arsenic exposure is associated with increased infant morbidity and reduced thymus size, indicating arsenic-related developmental immunotoxicity. We aimed to evaluate effects of prenatal arsenic exposure on thymic function at birth and related mechanisms of action. In a Bangladeshi cohort, arsenic was measured in urine (U-As, gestational week (GW) 8 and 30) and blood (B-As, GW14) in 130 women. Child thymic index was measured by sonography at birth and thymic function by signal-joint T-cell receptor-rearrangement excision circles (sjTRECs) in cord blood mononuclear cells (CBMC). In a subsample (n = 44), sjTRECs content in isolated CD4(+) and CD8(+) T cells, expression of oxidative-stress defense and apoptosis-related genes in CBMC, arsenic concentrations (urine, placenta, and cord blood), and oxidative stress markers in placenta and cord blood were measured. In multivariable-adjusted regression, ln U-As (GW8) was inversely associated with ln sjTRECs in CBMC (B = -0.25; 95% confidence interval [CI] -0.48 to -0.01). Using multivariable-adjusted spline regression, ln U-As (GW30) and ln B-As (GW14) were inversely associated with ln sjTRECs in CBMC (B = -0.53; 95% CI -0.93 to -0.13 and B = -1.27; 95% CI -1.89 to -0.66, respectively) below spline knots at U-As 150 μg/l and B-As 6 μg/kg. Similar inverse associations were observed in separated CD4(+) and CD8(+) T cells. Arsenic was positively associated with 8-hydroxy-2'-deoxyguanosine in cord blood (B = 0.097; 95% CI 0.05 to 0.13), which was inversely associated with sjTRECs in CD4(+) and CD8(+) T cells. In conclusion, prenatal arsenic exposure was associated with reduced thymic function, possibly via induction of oxidative stress and apoptosis, suggesting subsequent immunosuppression in childhood.