BioAnalysis - Pharmaceutical Sciences

Down-regulation of the epithelial cell-cell adhesion molecule E-cadherin is frequently associated with tumor formation and progression. Besides its role in physical cell-cell adhesion, E-cadherin is also thought to be involved in intracellular signaling in normal epithelial cells. In these cells, the Armadillo catenin p120ctn binds to the cytoplasmic domain of E-cadherin and stabilizes the adhesion complexes. On loss of E-cadherin, cytoplasmic p120ctn might accumulate and contribute to tumor malignancy. We used suppression subtractive hybridization to search for genes regulated by E-cadherin expression. We isolated human Nanos1 as a transcript of which levels decrease on E-cadherin reexpression in a human breast cancer cell line. The hNanos1 protein bears a COOH-terminal (CCHC) 2 zinc finger domain and belongs to an evolutionarily conserved protein family sharing functions in germ cell development in both vertebrates and invertebrates. We found an inverse correlation between E-cadherin and hNanos1 expression in various cell lines and under diverse conditions. Conditional expression of hNanos1 in human colorectal DLD1 cancer cells functionally abolished cell-cell adhesion. It induced cytoplasmic translocation of p120ctn, as well as strong migratory and invasive properties. We also found that the NH 2 -terminal domain of hNanos1, which is conserved only among mammals, interacts with p120ctn. hNanos1 counteracted the stimulatory effect of p120ctn on cell protrusion formation. Together, these findings describe a new function for hNanos1 as a downstream effector of E-cadherin loss contributing to tumor progression. Targeting hNanos1 might be a promising strategy in the treatment of E-cadherin-negative tumors in particular.

Down-regulation of the epithelial cell-cell adhesion molecule E-cadherin is frequently associated with tumor formation and progression. Besides its role in physical cell-cell adhesion, E-cadherin is also thought to be involved in intracellular signaling in normal epithelial cells. In these cells, the Armadillo catenin p120ctn binds to the cytoplasmic domain of E-cadherin and stabilizes the adhesion complexes. On loss of E-cadherin, cytoplasmic p120ctn might accumulate and contribute to tumor malignancy. We used suppression subtractive hybridization to search for genes regulated by E-cadherin expression. We isolated human Nanos1 as a transcript of which levels decrease on E-cadherin reexpression in a human breast cancer cell line. The hNanos1 protein bears a COOH-terminal (CCHC) 2 zinc finger domain and belongs to an evolutionarily conserved protein family sharing functions in germ cell development in both vertebrates and invertebrates. We found an inverse correlation between E-cadherin and hNanos1 expression in various cell lines and under diverse conditions. Conditional expression of hNanos1 in human colorectal DLD1 cancer cells functionally abolished cell-cell adhesion. It induced cytoplasmic translocation of p120ctn, as well as strong migratory and invasive properties. We also found that the NH 2 -terminal domain of hNanos1, which is conserved only among mammals, interacts with p120ctn. hNanos1 counteracted the stimulatory effect of p120ctn on cell protrusion formation. Together, these findings describe a new function for hNanos1 as a downstream effector of E-cadherin loss contributing to tumor progression. Targeting hNanos1 might be a promising strategy in the treatment of E-cadherin-negative tumors in particular.

The HIV-1 gene nef is important for progression toward AIDS and cellular depletion of the infected thymus. Expression of the Nef protein alone impairs human thymopoiesis. Here, we performed a structure-function analysis of the Nef protein by comparing the effect on T-cell development of different nef alleles, either wild type or defective for selected functions, expressed by human thymocytes. We show that Nef-mediated impaired thymopoiesis is not due to altered surface marker trafficking, nor dependent on oligomerization of Nef. By contrast, mutations in the myristoylation site and in signaling sites of Nef, ie, sites important for interaction with phosphofurin acidic cluster sorting protein-1 (PACS-1), Src homology domain 3 (SH3) domains, and p21-activated kinase 2 (PAK2), were found to be critical for its effect on T-cell development. These results point to sites in Nef to target therapeutically for restoration of thymopoiesis in HIV infection.

Human immunodeficiency virus (HIV) Nef is a membrane-associated protein decreasing surface expression of CD4, CD28, and major histocompatibility complex class I on infected cells. We report that Nef strongly down-modulates surface expression of the ␤-chain of the CD8␣␤ receptor by accelerated endocytosis, while CD8 ␣-chain expression is less affected. By mutational analysis of the cytoplasmic tail of the CD8 ␤-chain, an FMK amino acid motif was shown to be critical for Nef-induced endocytosis. Although independent of CD4, endocytosis of the CD8 ␤-chain was abrogated by the same mutations in Nef that affect CD4 down-regulation, suggesting common molecular interactions. The ability to down-regulate the human CD8 ␤-chain was conserved in HIV-1, HIV-2, and simian immunodeficiency virus SIVmac239 Nef and required an intact AP-2 complex. The Nef-mediated internalization of receptors, such as CD4, major histocompatibility complex class I, CD28, and CD8␣␤, may contribute to the subversion of the host immune system and progression towards AIDS.

The HIV-1 gene nef is important for pro- gression toward AIDS and cellular deple- tion of the infected thymus. Expression of the Nef protein alone impairs human thy- mopoiesis. Here, we performed a struc- ture-function analysis of the Nef protein by comparing the effect on T-cell develop- ment of different nef alleles, either wild type or defective for selected functions,

P-cadherin expression in breast carcinomas has been associated with tumors of high histologic grade and lacking estrogen receptor-␣, suggesting a link between these proteins. In the MCF-7/AZ breast cancer cell line, blocking estrogen receptor-␣ signaling with the antiestrogen ICI 182,780 induced an increase of P-cadherin, which coincided with induction of in vitro invasion. Retroviral transduction of MCF-7/AZ cells, as well as HEK 293T cells, showed the proinvasive activity of P-cadherin, which requires the juxtamembrane domain of its cytoplasmic tail. This study establishes a direct link between P-cadherin expression and the lack of estrogen receptor-␣ signaling in breast cancer cells and suggests a role for Pcadherin in invasion, through its interaction with proteins bound to the juxtamembrane domain.

Neoexpression or upregulation of placental cadherin (P-cadherin), a member of the classical cadherin family, has previously been described in several carcinomas, such as colorectal and bladder carcinomas. In this study, we combined two different approaches, immunohistochemistry of tumor samples and in vitro knockdown of P-cadherin, to gain a better insight into the role of P-cadherin in these types of cancer. First, we performed immunohistochemistry for P-and E-cadherins in a series of 52 colorectal adenocarcinomas, including well, moderately and poorly differentiated (WD, MD, and PD) tumors. Decrease or loss of P-cadherin neoexpression was significantly associated with a higher tumor grade and could discriminate WD from MD and/ or PD tumors (p < 0.001). E-cadherin, on the other hand, was strongly expressed at the membrane of most WD (18 of 19) and MD tumors (15 of 19). Downregulation correlated significantly with the PD phenotype (p 0.001). In a second approach, we transiently or stably knocked down P-cadherin in HT-29 colon adenocarcinoma cells. This led to decreased intercellular adhesion and to an increased migratory and long-term invasive phenotype compared with control HT-29 cells, suggesting that P-cadherin acts as a proadhesive and anti-invasive/antimigratory molecule in colon carcinoma cells. Contrasting with these results and illustrating the context-specific function of P-cadherin were our results obtained in RT-112 bladder carcinoma cells. Stable knockdown of P-cadherin in RT-112 cells diminished invasion and migration, and promoted intercellular adhesion.

Background: pABA biosynthesis is a potential target for antifolate drugs. Results: Rubreserine inhibits GAT-ADCS, an enzyme involved in pABA biosynthesis, and decreases the folate content in Arabidopsis and Toxoplasma. Conclusion: Specific inhibition of pABA synthesis induces growth limitation of plants and apicomplexan parasites. Significance: GAT-ADCS is a valuable target in eukaryotes, and rubreserine is a novel scaffold for anti-parasitic drugs.

A UHPLC-MS/MS method was developed and validated for the profiling of 6 folate species in potatoes. The calibration curves cover a wide, linear range (the lower and upper limits of quantitation range between 0.22 -0.24 and 216.07 -242.28 µg/100g fresh weight), allowing sensitive determination in small amounts of potato flesh. With a single exception, the acceptance criteria for intra-and interday-precision and accuracy were met: for all QC's the %RSD and %bias were lower than 15% (or 20% at the lower limit of quantitation).

An LC-MS/MS method has been developed and validated for the analysis of six monoglutamate folates in rice. Accurate determination of folates in rice seeds required the optimisation of an extraction procedure encompassing homogenisation, heat treatment, tri-enzyme treatment (␣-amylase, protease and deconjugase), centrifugation and ultrafiltration. The resulting extract was loaded onto a Polaris C 18-A column, followed by gradient elution and detection by tandem mass spectrometry. The validated method is sensitive, reproducible, accurate, and linear between 1 and 400 g/100 g rice (dry weight). The limit of detection and limit of quantification in diluted rice matrix ranged between 0.2 and 1.2 g/100 g and between 0.6 and 4 g/100 g, respectively, depending on the compound. Intra-and inter-day precision varied, respectively, from 1.0 to 9.1% RSD, and from 3.4 to 13.5% RSD, except for one compound (19.1% at low concentrations). The accuracy ranged from 96.9 to 115.4%. Matrix effects were compensated for by use of isotopically labelled internal standards. Most folates in rice extracts were stable when kept for 2 weeks at −20 and −80 • C, but degraded after three freeze-thaw cycles or at 4 • C, even when stored protected from light. Our validated method offers a sensitive and versatile approach to determine the level of six different monoglutamate folates in a complex matrix as rice.

Purpose To predict the tramadol in vivo pharmacokinetics in adults by using in vitro metabolism data and an in vitro-in vivo extrapolation (IVIVE)-linked physiologically-based pharmacokinetic (PBPK) modeling and simulation approach (Simcyp®). Methods Tramadol metabolism data was gathered using metabolite formation in human liver microsomes (HLM) and recombinant enzyme systems (rCYP). Hepatic intrinsic clearance (CLint H ) was (i) estimated from HLM corrected for specific CYP450 contributions from a chemical inhibition assay (model 1); (ii) obtained in rCYP and corrected for specific CYP450 contributions by study-specific intersystem extrapolation factor (ISEF) values (model 2); and (iii) scaled back from in vivo observed clearance values (model 3). The modelpredicted clearances of these three models were evaluated against observed clearance values in terms of relative difference of their geometric means, the fold difference of their coefficients of variation, and relative CYP2D6 contribution. Results Model 1 underpredicted, while model 2 overpredicted the total tramadol clearance by −27 and +22%, respectively. The CYP2D6 contribution was underestimated in both models 1 and 2. Also, the variability on the clearance of those models was slightly underpredicted. Additionally, blood-to-plasma ratio and hepatic uptake factor were identified as most influential factors in the prediction of the hepatic clearance using a sensitivity analysis. Conclusion IVIVE-PBPK proved to be a useful tool in combining tramadol's low turnover in vitro metabolism data with systemspecific physiological information to come up with reliable PK predictions in adults.

Purpose To predict the tramadol in vivo pharmacokinetics in adults by using in vitro metabolism data and an in vitro-in vivo extrapolation (IVIVE)-linked physiologically-based pharmacokinetic (PBPK) modeling and simulation approach (Simcyp®). Methods Tramadol metabolism data was gathered using metabolite formation in human liver microsomes (HLM) and recombinant enzyme systems (rCYP). Hepatic intrinsic clearance (CLint H ) was (i) estimated from HLM corrected for specific CYP450 contributions from a chemical inhibition assay (model 1); (ii) obtained in rCYP and corrected for specific CYP450 contributions by study-specific intersystem extrapolation factor (ISEF) values (model 2); and (iii) scaled back from in vivo observed clearance values (model 3). The modelpredicted clearances of these three models were evaluated against observed clearance values in terms of relative difference of their geometric means, the fold difference of their coefficients of variation, and relative CYP2D6 contribution. Results Model 1 underpredicted, while model 2 overpredicted the total tramadol clearance by −27 and +22%, respectively. The CYP2D6 contribution was underestimated in both models 1 and 2. Also, the variability on the clearance of those models was slightly underpredicted. Additionally, blood-to-plasma ratio and hepatic uptake factor were identified as most influential factors in the prediction of the hepatic clearance using a sensitivity analysis. Conclusion IVIVE-PBPK proved to be a useful tool in combining tramadol's low turnover in vitro metabolism data with systemspecific physiological information to come up with reliable PK predictions in adults.