Citations

Abstract Purpose: SR13668, an orally active AKT pathway inhibitor, has demonstrated cancer chemopreventive potential in preclinical studies. To accelerate the clinical development of this promising agent, we designed and conducted the first-ever phase 0 chemoprevention trial to evaluate and compare the effects of food and formulation on SR13668 bioavailability. Patients and Methods: Healthy adult volunteers were randomly assigned to receive a single 38-mg oral dose of SR13668 in one of five different formulations, with or without food. Based on existing animal data, SR13668 in a PEG400/Labrasol@ oral solution (formulation 1) was defined as the reference formulation. Four self-emulsifying solid dispersion test formulations in capsules were also investigated: Solutol@ HS 15 (formulation 2), Solutol@ HS 15/Vitamin E TGPS (50/50 w/w %) (formulation 3), Vitamin E TGPS (formulation 4), and Myrj 53 (formulation 5). SR163668 bioavailability was compared using a two-stage study design. In stage I, participants were randomized to receive the formulation 1 with or without a high-fat meal after an overnight fast. In Stage II, participants were randomly assigned to receive the test formulations, using the preferred dietary condition identified in stage I. Blood samples were obtained pre- and post-agent administration for pharmacokinetic analyses. Area under the plasma concentration-time curve (AUC) was defined as the primary endpoint. Data were analyzed and compared using established statistical methods for phase 0 trials with a limited sample size. Results: Participants (N=20) were rapidly accrued over a 5-month period. Complete pharmacokinetic data were available for 18 randomized participants. The time to peak plasma concentration and half-life values for SR13668 were 3 hours (range, 2 — 6 hours) and 11.2 ± 3.1 hours, respectively, and were not dependent on the formulation. In stage I, the oral bioavailability of SR13668 in formulation 1 was greater under the fed versus fasting dietary state (p = 0.05, Wilcoxon rank-sum test). Therefore, the fed state was selected as the preferred dietary condition for stage II. In stage II, the bioavailability of SR13668 for each of the test formulations were compared with the bioavailability of formulation 1 in the fed state. While not significantly different from formulation 1, formulation 2 AUC0-24h was significantly different (p = 0.004, ANOVA) from formulation 3, 4, and 5 (AUC0-24h, formulation 1- 222 ± 53 ng/ml·hr; AUC0-24h, formulation 2 — 302 ± 78 ng/ml·hr; AUC-177±39ng/ml·hr; AUC-144±29 0-24h, formulation30-24h, formulation 4 ng/ml·hr; AUC0-24h, formulation 5- 98 ± 21 ng/ml·hr). Formulation 1 AUC0-24h was almost 40% lower than the value achieved with formulation 2, and not significantly different from formulation 3, 4, and 5. Thus, formulation 2 provided the highest bioavailability of SR13668. Conclusions: Using a novel, highly efficient study design, we rapidly identified a lead formulation (Solutol@ HS 15) of SR13668 for further clinical testing. Our findings support application of the phase 0 trial paradigm to accelerate chemoprevention agent development. Supported by NIH grants N01-CN-35000, CA15083-34C3 and UL1 RR024150. Citation Information: Cancer Prev Res 2010;3(12 Suppl):CN02-03.

Abstract Although the importance of RGS-GAIP–interacting protein (GIPC) in the biology of malignant cells is well known, the molecular mechanism of GIPC in the inhibition of tumor progression has not been identified. This study focused on elucidating the molecular role of GIPC in breast cancer progression. By using a human breast tumor specimen, an in vivo mouse model, and breast cancer cell lines, we showed for the first time that GIPC is involved in breast cancer progression through regulation of breast cancer cell proliferation, survival, and invasion. Furthermore, we found that the Akt/Mdm2/p53 axis, insulin-like growth factor-1 receptor, matrix metalloproteinase-9, and Cdc42 were downstream of GIPC signaling in breast cancer cells. Moreover, we showed that wild-type p53 reduced GIPC-induced breast cancer cell survival, whereas mutant p53 inhibited GIPC-induced cell invasion. Finally, we demonstrated that an N-myristoylated GIPC peptide (CR1023, N-myristoyl-PSQSSSEA) capable of blocking the PDZ domain of GIPC successfully inhibited MDA-MB-231 cell proliferation, survival, and further in vivo tumor growth. Taken together, these findings demonstrate the importance of GIPC in breast tumor progression, which has a potentially significant impact on the development of therapies against many common cancers expressing GIPC, including breast and renal cancer. Mol Cancer Res; 8(12); 1591–600. ©2010 AACR.

Intraflagellar transport (IFT) machinery mediates the bidirectional movement of cargos that are required for the assembly and maintenance of cilia. However, little is known about how IFT is regulated in vivo. In this study, we show that the small guanosine triphosphatase (GTPase) adenosine diphosphate ribosylation factor–like protein 13 (ARL-13) encoded by the Caenorhabditis elegans homologue of the human Joubert syndrome causal gene ARL13B, localizes exclusively to the doublet segment of the cilium. arl-13 mutants have shortened cilia with various ultrastructural deformities and a disrupted association between IFT subcomplexes A and B. Intriguingly, depletion of ARL-3, another ciliary small GTPase, partially suppresses ciliogenesis defects in arl-13 mutants by indirectly restoring binding between IFT subcomplexes A and B. Rescue of arl-13 mutants by ARL-3 depletion is mediated by an HDAC6 deacetylase-dependent pathway. Thus, we propose that two conserved small GTPases, ARL-13 and ARL-3, coordinate to regulate IFT and that perturbing this balance results in cilia deformation.

Abstract The low efficiency of reprogramming and genomic integration of virus vectors obscure the potential application of induced pluripotent stem (iPS) cells; therefore, identification of chemicals and cooperative factors that may improve the generation of iPS cells will be of great value. Moreover, the cellular mechanisms that limit the reprogramming efficiency need to be investigated. Through screening a chemical library, we found that two chemicals reported to upregulate E-cadherin considerably increase the reprogramming efficiency. Further study of the process indicated that E-cadherin is upregulated during reprogramming and the established iPS cells possess E-cadherin-mediated cell–cell contact, morphologically indistinguishable from embryonic stem (ES) cells. Our experiments also demonstrate that overexpression of E-cadherin significantly enhances reprogramming efficiency, whereas knockdown of endogenous E-cadherin reduces the efficiency. Consistently, abrogation of cell–cell contact by the inhibitory peptide or the neutralizing antibody against the extracellular domain of E-cadherin compromises iPS cell generation. Further mechanistic study reveals that adhesive binding activity of E-cadherin is required. Our results highlight the critical role of E-cadherin-mediated cell–cell contact in reprogramming and suggest new routes for more efficient iPS cell generation.

Background Hepatitis B virus (HBV) genotype B and C seem not to affect the therapeutic response to lamivudine (3TC). Whether a given genotype has an earlier emergence of 3TC resistance remains unclear. We thus conducted this study to elucidate the association of HBV genotype with the emergence of 3TC-resistant strains in Taiwanese patients. Methods Forty chronic hepatitis B patients who developed resistance after 3TC therapy were retrospectively enrolled. HBV genotype, serum alanine aminotransferase (ALT) and HBV DNA levels were determined at baseline. The presence of 3TC-resistant mutations was confirmed by direct sequencing whenever biochemical breakthrough developed. Results The distribution of HBV genotype B and C in 40 patients receiving 3TC therapy were 60% and 40%, respectively. The mean interval to detect 3TC- resistant strain was 19.6 ±1.7 months. By using multivariate analysis, HBV genotype B and higher pre-treatment HBV DNA level were independently associated with earlier detection of 3TC-resistant strains. In addition, genotype B was significantly associated with development of 3TC resistance within the first 12 months of 3TC therapy compared with genotype C (odds ratio 8.27; P=0.004). Conclusions Compared with HBV genotype C, genotype B appears to have an earlier biochemical resistance to 3TC than genotype C. Therefore, more frequent monitoring of viral load or genotypical resistance might be needed for patients with HBV genotype B infection receiving 3TC therapy, especially during the first year.

We thank you for calling our attention to the comments made by Professor Biersack on our paper (Huang et al, 1987) concerning the diagnostic significance of liver and spleen scans in systemic mast-cell disease (SMCD).

ABSTRACTPasteurella (Mannheimia) haemolyticaleukotoxin (Lkt) causes cell type- and species-specific effects in ruminant leukocytes. Recent studies indicate thatP. haemolyticaLkt binds to bovine CD18, the common subunit of all β2 integrins. We designed experiments with the following objectives: to identify which member of the β2 integrins is a receptor for Lkt; to determine whether Lkt binding to the receptor is target cell (bovine leukocytes) specific; to define the relationships between Lkt binding to the receptor, calcium elevation, and cytolysis; and to determine whether a correlation exists between Lkt receptor expression and the magnitude of target cell cytolysis. We compared Lkt-induced cytolysis in neutrophils from control calves and from calves with bovine leukocyte adhesion deficiency (BLAD), because neutrophils from BLAD-homozygous calves exhibit reduced β2 integrin expression. The results demonstrate for the first time that Lkt binds to bovine CD11a and CD18 (lymphocyte function-associated antigen 1 [LFA-1]). The binding was abolished by anti-CD11a or anti-CD18 monoclonal antibody (MAb). Lkt-induced calcium elevation in bovine alveolar macrophages (BAMs) was inhibited by anti-CD11a or anti-CD18 MAb (65 to 94% and 37 to 98%, respectively, at 5 and 50 Lkt units per ml;P< 0.05). Lkt-induced cytolysis in neutrophils and BAMs was also inhibited by anti-CD11a or anti-CD18 MAb in a concentration-dependent manner. Lkt bound to porcine LFA-1 but did not induce calcium elevation or cytolysis. In neutrophils from BLAD calves, Lkt-induced cytolysis was decreased by 44% compared to that of neutrophils from control calves (P< 0.05). These results indicate that LFA-1 is a Lkt receptor, Lkt binding to LFA-1 is not target cell specific, Lkt binding to bovine LFA-1 correlates with calcium elevation and cytolysis, and bovine LFA-1 expression correlates with the magnitude of Lkt-induced target cell cytolysis.

Abstract Expression of neuropilin-1 (NRP-1) has been shown in many cancer cells, but its molecular effect on tumorigenesis is largely unknown. In this report, we show that in aggressive types of renal cell carcinoma (RCC), NRP-1 is expressed at a high level. We show that after knockdown of NRP-1 by short hairpin RNA, RCC cells express significantly lower levels of MDM-2 and p63 proteins but higher levels of p53, and exhibit reduced migration and invasion. When implanted in mice, RCC cells with a reduced NRP-1 level have a statistically significant smaller tumor-forming ability than control cells. Also, NRP-1 knockdown RCC cells exhibit a more differentiated phenotype, as evidenced by the expression of epithelial-specific and kidney-specific cadherins, and the inhibition of sonic hedgehog expression participated in this effect. Inhibition of sonic hedgehog expression can be reversed by ΔNp63α overexpression. Our study reveals that NRP-1 helps maintain an undifferentiated phenotype in cancer cells. [Cancer Res 2008;68(21):8667–72]

AbstractIn vertebrates, molecular mechanisms dictate angioblasts' migration and subsequent differentiation into arteries and veins. In this study, we used a microarray screen to identify a novel member of the sucrose nonfermenting related kinase (snrk-1) family of serine/threonine kinases expressed specifically in the embryonic zebrafish vasculature and investigated its function in vivo. Using gain- and loss-of-function studies in vivo, we show that Snrk-1 plays an essential role in the migration, maintenance, and differentiation of angioblasts. The kinase function of Snrk-1 is critical for migration and maintenance, but not for the differentiation of angioblasts. In vitro, snrk-1 knockdown endothelial cells show only defects in migration. The snrk-1 gene acts downstream or parallel to notch and upstream of gridlock during artery-vein specification, and the human gene compensates for zebrafish snrk-1 knockdown, suggesting evolutionary conservation of function.

The neuropilin (Nrp)1 receptor is essential for both nervous and vascular system development. Nrp1 is unusually versatile, because it transmits both chemoattractive and repulsive signals in response to vascular endothelial growth factor (VEGF)-A and class 3 semaphorins, respectively. Both Nrp1 and VEGF receptor 2 undergo ligand-dependent endocytosis. We sought to establish the endocytic pathway of Nrp1 and to determine whether uptake is required for its signaling. Whereas Nrp1 underwent clathrin-dependent endocytosis in response to VEGFA 165 treatment, semaphorin 3C (sema3C) induced lipid raft–dependent endocytosis. The myosin VI PDZ (postsynaptic density 95, Disk large, Zona occludens-1) adaptor protein synectin was essential for Nrp1 trafficking. Sema3C failed to inhibit migration of synectin −/− endothelial cells, mirroring the lower migratory response of these cells to VEGFA 165 . These results show that the endocytic pathway of Nrp1 is determined by its ligand and that the trafficking of Nrp1 is essential for its signaling.