Biomedical subjects

Paola Milla

Publications and source records attributed to Paola Milla.

7 recordsLinked to original sources

PubMed2006

Gemcitabine and oxaliplatin in patients with pancreatic adenocarcinoma: clinical and pharmacokinetic data.

OBJECTIVES: This phase 2 study evaluated clinical efficacy, toxicity, and pharmacokinetics of combination gemcitabine (GEM) and oxaliplatin (OXA) in patients with advanced pancreatic adenocarcinoma. METHODS: Of 30 eligible patients, 20 had metastatic disease and 10 had nonmetastatic unresectable locally advanced disease. Gemcitabine 1000 mg/m2 as a 10 mg/m2/min intravenous infusion on day 1 and oxaliplatin 100 mg/m2 as a 2-hour intravenous infusion on day 2 were administered every 2 weeks. Pharmacokinetics were evaluated in 11 patients by administering the 2 drugs in opposing sequences GEM-OXA (GEM day 1, OXA day 2) and OXA-GEM (OXA day 1, GEM day 2). RESULTS: Of 30 patients evaluated, 9 had a partial response, 11 had disease stabilization, and 10 had disease progression. Median progression-free survival and overall survival were 5.5 and 9.5 months, respectively. The 1-year survival was 37% for all patients. This study revealed no significant pharmacokinetic interaction between the 2 drugs in the GEM-OXA or in the OXA-GEM sequence. CONCLUSIONS: The combination of GEM and OXA was well tolerated and showed a promising activity in patients with advanced pancreatic adenocarcinoma; no sequence-dependent pharmacokinetic interaction occurred when comparing the GEM-OXA versus the OXA-GEM sequence, with a 24-hour interval.

Adenocarcinoma↗

PubMed2005

Synthesis and biological activity of new iodoacetamide derivatives on mutants of squalene-hopene cyclase.

New iodoacetamide derivatives, containing a dodecyl or a squalenyl moiety, were synthesized. The effect of these new thiol-reacting molecules was studied on two mutants of Alicyclobacillus acidocaldarius squalene-hopene cyclase constructed especially for this purpose. In the quintuple mutant, all five cysteine residues of the enzyme are substituted with serine; in the sextuple mutant, this quintuple substitution is accompanied by the substitution of aspartate D376, located at the enzyme's active site, with a cysteine. N-Dodecyliodoacetamide had little activity toward either mutant, whereas N-squalenyliodoacetamide showed a stronger effect on the sextuple than on the quintuple mutant, as expected.

Bacillus↗

PubMed2005

Analogs of squalene and oxidosqualene inhibit oxidosqualene cyclase of Trypanosoma cruzi expressed in Saccharomyces cerevisiae.

Recently, a number of inhibitors of the enzyme oxidosqualene cyclase (OSC; EC 5.4.99.7), a key enzyme in sterol biosynthesis, were shown to inhibit in mammalian cells the multiplication of Trypanosoma cruzi, the parasite agent of Chagas' disease. The gene coding for the OSC of T. cruzi has been cloned and expressed in Saccharomyces cerevisiae. The expression in yeast cells could be a safe and easy model for studying the activity and the selectivity of the potential inhibitors of T. cruzi OSC. Using a homogenate of S. cerevisiae cells expressing T. cruzi OSC, we have tested 19 inhibitors: aza, methylidene, vinyl sulfide, and conjugated vinyl sulfide derivatives of oxidosqualene and squalene, selected as representative of different classes of substrate analog inhibitors of OSC. The IC50 values of inhibition (the compound concentration at which the enzyme is inhibited by 50%) are compared with the values obtained using OSC of pig liver and S. cerevisiae. Many inhibitors of pig liver and S. cerevisiae OSC show comparable IC50 for T. cruzi OSC, but some phenylthiovinyl derivatives are 10-100 times more effective on the T. cruzi enzyme than on the pig or S. cerevisiae enzymes. The expression of proteins of pathogenic organisms in yeast seems very promising for preliminary screening of compounds that have potential therapeutic activity.

Animals↗

PubMed2003

Conjugated methyl sulfide and phenyl sulfide derivatives of oxidosqualene as inhibitors of oxidosqualene and squalene-hopene cyclases.

Various (1E,3E)- and (1Z,3E)-conjugated methylthio derivatives of oxidosqualene (OS) and conjugated and non-conjugated phenylthio derivatives of OS were obtained. These compounds, designed as inhibitors of pig liver and Saccharomyces cerevisiae 2,3-oxidosqualene-lanosterol cyclases (OSC) (EC 5.4.99.7) and of Alicyclobacillus acidocaldarius squalene-hopene cyclase (SHC) (EC 5.4.99.-), contain the reactive function adjacent to carbons involved in the formation of the third and the fourth cycle during OS cyclization. All the new compounds are inhibitors of OSC and SHC, with various degrees of selectivity. The conjugated methylthio derivatives behaved as potent inhibitors of S. cerevisiae OSC, whereas most of the phenylthio derivatives were especially active toward SHC.

Animals↗

PubMed2002

Thiol-modifying inhibitors for understanding squalene cyclase function.

The function of squalene-hopene cyclase from Alicyclobacillus acidocaldarius was studied by labelling critical cysteine residues of the enzyme, either native or inserted by site-directed mutagenesis, with different thiol-reacting molecules. The access of the substrate to the active centre cavity through a nonpolar channel that contains a narrow constriction harbouring a cysteine residue (C435) was probed by labelling experiments on both a C435S mutant, lacking C435 of the channel constriction, and a C25S/C50S/C455S/C537S mutant, bearing C435 as the only cysteine residue. Labelling experiments with tritiated 3-carboxy-4-nitrophenyl-dithio-1,1',2-trisnorsqualene (CNDT-squalene) showed that the cysteine residue at the channel constriction was covalently modified by the squalene-like inhibitor. Time-dependent inactivation of the C25S/C50S/C455S/C537S mutant by a number of squalene analogues and other agents with thiol-modifying activity suggested that modifying C435 caused the obstruction of the channel constriction thus blocking access of the substrate to the active site. The tryptic fragment comprising C435 of the quadruple mutant labelled with the most effective inhibitor had the expected altered molecular mass, as determined by LC-ESI-MS measurements. The arrangement of the substrate in the active site cavity was studied by using thiol reagents as probes in labelling experiments with the double mutant D376C/C435S in which D376, supposedly the substrate-protonating residue, was substituted by cysteine. The inhibitory effect was evaluated in terms of the reduced ability to cyclize oxidosqualene, as the mutant is unable to catalyse the reaction of squalene to hopene. Among the inhibitors tested, the substrate analogue squalene-maleimide proved to be a very effective time-dependent inhibitor.

Amino Acid Substitution↗

PubMed2001

Yeast oxidosqualene cyclase (Erg7p) is a major component of lipid particles.

Oxidosqualene cyclase of the yeast encoded by the ERG7 gene converts oxidosqualene to lanosterol, the first cyclic component of sterol biosynthesis. In a previous study (Athenstaedt, K., Zweytick, D., Jandrositz, A, Kohlwein, S. D., and Daum, G. (1999) J. Bacteriol. 181, 6441-6448), Erg7p was identified as a component of yeast lipid particles. Here, we present evidence that Erg7p is almost exclusively associated with this compartment as shown by analysis of enzymatic activity, Western blot analysis, and in vivo localization of Erg7p-GFP. Occurrence of oxidosqualene cyclase in other organelles including the endoplasmic reticulum is negligible. In an erg7 deletion strain or in wild-type cells treated with an inhibitor of oxidosqualene cyclase, the substrate of Erg7p, oxidosqualene, accumulated mostly in lipid particles. Storage in lipid particles of this intermediate produced in excess may provide a possibility to exclude this membrane-perturbing component from other organelles. Thus, our data provide evidence that lipid particles are not only a depot for neutral lipids, but also participate in coordinate sterol metabolism and trafficking and serve as a storage site for compounds that may negatively affect membrane integrity.

Binding Sites↗

PubMedDate not supplied

Pegylated liposomal doxorubicin and vinorelbine in recurrent ovarian carcinoma: a pharmacokinetic study on alternate administration sequences.

BACKGROUND: This multicenter pharmacokinetic study evaluated the pharmacokinetics and toxicity of the combination of pegylated liposomal doxorubicin (PLD) and vinorelbine (VNR) in patients with recurrent ovarian cancer, when administered in opposing sequences. PATIENTS AND METHODS: Eighteen heavily pre-treated ovarian cancer patients received treatment with PLD 30 mg/m2 and VNR 30 mg/m2 every 3 weeks for 6 cycles, 9 being given the PLD-VNR sequence vs. 9 the VNR-PLD sequence. RESULTS: The VNR AUCtot and plasma levels were considerably higher with the PLD-VNR sequence and VNR clearance, clearly related to Kel, was about half that occurring with VNR-PLD. Toxicity was generally mild and reversible. In both arms, a sound correlation was found between VNR AUCtot and absolute neutrophil count decrease. A possible correlation between hematological toxicity and the 2 opposing administration sequences was also shown. CONCLUSION: The higher VNR AUCtot and plasma levels during the elimination phase with the PLD-VNR sequence may be related to a P-gp membrane glycoprotein inhibition by PLD vescicles which, in turn, may influence the plasma level of the associated VNR. PLD-VNR, producing a higher plasma level and very mild toxicity, may be considered the preferred sequence.

Adolescent↗