ABSTRACT
YM155, which blocks the expression of survivin, a member of the inhibitor of apoptosis (IAP) family, induces cell death in a variety of cancer types, including prostate, bladder, breast, leukemia, and non-small lung cancer. However, the mechanism underlying gastric cancer susceptibility and resistance to YM155 is yet to be specified. Here, we demonstrate that cIAP1 stability dictates resistance to YM155 in human gastric cancer cells. Treatment of human gastric cancer cells with YM155 differentially induced cell death dependent on the stability of cIAP1 as well as survivin. Transfection with cIAP1 expression plasmids decreased cell sensitivity to YM155, whereas knockdown of endogenous cIAP1 using RNA interference enhanced sensitivity to YM155. In addition, double knockdown of survivin and cIAP1 significantly induced cell death in the YM155-resistant cell line, MKN45. We also showed that YM155 induced autoubiquitination and proteasome-dependent degradation of cIAP1. Surprisingly, survivin affected the stability of cIAP1 through binding, contributing to cell sensitivity to YM155. Thus, our findings reveal that YM155 sensitizes human gastric cancer cells to apoptotic cell death by degrading cIAP1, and furthermore, cIAP1 in gastric cancer cells may act as a PD marker for YM155 treatment.
Subject(s)
Antineoplastic Agents/pharmacology , Gastric Mucosa/drug effects , Gene Expression Regulation, Neoplastic , Imidazoles/pharmacology , Inhibitor of Apoptosis Proteins/genetics , Naphthoquinones/pharmacology , Cell Death/drug effects , Cell Line, Tumor , Drug Resistance, Neoplasm/genetics , Gastric Mucosa/metabolism , Gastric Mucosa/pathology , Humans , Inhibitor of Apoptosis Proteins/antagonists & inhibitors , Inhibitor of Apoptosis Proteins/metabolism , Protein Binding , Protein Stability , Proteolysis , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Signal Transduction , Survivin , UbiquitinationABSTRACT
A new class of thermosensitive micellar cyclotriphosphazenes has been synthesized by stepwise nucleophilic substitutions of hexachlorocyclotriphosphazene with a hydrophilic methoxy poly(ethylene glycol) (MPEG) and a hydrophobic oligopeptide selected from tetra- to hexapeptides, and characterized by means of multinuclear ((1)H, (31)P) NMR spectroscopy, elemental analysis, and dynamic light scattering (DLS) method. All the amphiphilic trimers were found to form stable micelles by self-assembly in aqueous solution and to exhibit a lower critical solution temperature in the range of 20-48 degrees C in water depending on the hydrophilic to hydrophobic balance of the side groups. The micelles formed from the trimers bearing MPEG350 and a tetra- or pentapeptide were found to have a mean diameter of 13-14 nm, while, surprisingly, the trimers bearing longer MPEG550 and hexapeptides have shown remarkable contraction of their micelle size to a mean diameter of 7-8 nm, probably due to the strong intermolecular hydrophobic interactions among the hexapeptide groups of the trimers. The local tolerance tests using rabbits have shown excellent biocompatibility of the trimers. Also a promising in vitro releasing profile was obtained for local delivery of human growth hormone (hGH) as a model protein drug.
Subject(s)
Micelles , Nitriles/chemistry , Nitriles/pharmacokinetics , Phosphorus Compounds/chemistry , Phosphorus Compounds/pharmacokinetics , Temperature , Animals , Biological Availability , Drug Carriers/chemistry , Drug Carriers/pharmacokinetics , Humans , Male , Polyethylene Glycols/chemistry , Polyethylene Glycols/pharmacokinetics , RabbitsABSTRACT
Biocompatible and thermosensitive poly(organophosphazenes) with a lower critical solution temperature (LCST) below body temperature have been designed with the aim for the local delivery of peptide and protein drugs. These polymers could be synthesized by introducing short chain tri- or tetraethylene glycol as a hydrophilic group and a dipeptide, GlyGluEt2 as a hydrophobic group into the polyphosphazene backbone. The local tolerance tests using rabbits have shown that our polymers are biocompatible. Using the amphiphilic properties of these polymers, in vitro studies were performed for loading and releasing of a human growth hormone (hGH) as a model drug. The entrapment efficiency (%) of hGH by the polymer decreased as its polymer concentration increased, but exhibited high efficiency of more than 95% even at 20% hGH concentration in the polymer. The entrapped hGH has shown to be controlled releasing for 3-4 days.
