In Vivo Reprogramming of hTERT by Trans-splicing Ribozyme to Target Tumor Cells

We have developed and validated a new tumor-targeting gene therapy strategy based upon the targeting and replacement of human telomerase reverse transcriptase (hTERT) RNA, using a trans-splicing ribozyme. By constructing novel adenoviral vectors harboring the hTERT-targeting trans-splicing ribozymes with the downstream reporter gene (Ad-Ribo-LacZ) or suicide gene (Ad-Ribo-HSVtk) driven by the cytomegalovirus (CMV) promoter, we demonstrated that this viral system selectively marks tumor cells expressing hTERT or sensitizes tumor cells to prodrug treatments. We confirmed that Ad-Ribo-LacZ successfully and selectively delivered a ribozyme that performed a highly specific trans-splicing reaction into hTERT-expressing cancer cells, both in vitro and in a peritoneal carcinomatosis nude mouse model. We also determined that the hTERT-specific expression of the suicide gene in the Ad-Ribo-HSVtk, and treatment with the corresponding prodrug, reduced tumor progression with almost the same efficacy as the strong constitutive CMV promoter-driven adenovirus, both in cancer cell lines and in nude mouse HT-29 xenografts. These observations provide the basis for a novel approach to cancer gene therapy, and demonstrate that trans-splicing ribozymes can be employed as targeting anti-cancer agents which recognize cancer-specific transcripts and reprogram them, thereby combating cancerous cells.

Classification of the degradability of 30 pharmaceuticals in water with ozone, UV and H2O2

Experiments were conducted to assess the degradability of 30 PPCPs, selected on the basis of consumption and environmental relevance, by O3 process, UV process and AOPs consisting of UV/ H2O2, O3/UV and O3/H2O2. A batch reactor with volume of 22L of water including the PPCPs was used. For UV process, combination of UV and H2O2 or O3 that can generate OH radicals was capable of degrading the PPCPs faster than UV radiation alone. On the other hand, O3 process and O3-based/UV-based AOPs could remove a variety of the PPCPs effectively, while some PPCPs such as 2-QCA, DEET and cyclophosphamide showed a relatively low degradability compared with the other PPCPs. However, further evaluation on formation of intermediate products resulting from the degradation of the parent PPCPs will be needed because DOC concentration was not decreased with lowered concentrations of the PPCPs.

15-Deoxy-delta 12,14-prostaglandin J2 (15d-PGJ 2) sensitizes human leukemic HL-60 cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis through Akt downregulation

While tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a promising new agent for the treatment of cancer, resistance to TRAIL remains a therapeutic challenge. Identifying agents to use in combination with TRAIL to enhance apoptosis in leukemia cells would increase the potential utility of this agent as a therapy for leukemia. Here, we show that 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2), a natural ligand for peroxisome proliferator-activated receptor gamma (PPARgamma), can sensitize TRAIL-resistant leukemic HL-60 cells to TRAIL-induced apoptosis. The sensitization to TRAIL-induced apoptosis by 15d-PGJ2 was not blocked by a PPARgamma inhibitor (GW9662), suggesting a PPARgamma-independent mechanism. This process was accompanied by activation of caspase-8, caspase-9, and caspase-3 and was concomitant with Bid and PARP cleavage. We observed significant decreases in XIAP, Bcl-2, and c-FLIP after cotreatment with 15d-PGJ2 and TRAIL. We also observed the inhibition of Akt expression and phosphorylation by cotreatment with 15d-PGJ2 and TRAIL. Furthermore, inactivation of Akt by Akt inhibitor IV sensitized human leukemic HL-60 cells to TRAIL, indicating a key role for Akt inhibition in these events. Taken together, these findings indicate that 15d-PGJ2 may augment TRAIL-induced apoptosis in human leukemia cells by down-regulating the expression and phosphorylation of Akt.

o-GlcNAc transferase is activated by CaMKIV-dependent phosphorylation under potassium chloride-induced depolarization in NG-108-15 cells

Post-translational modification of cellular proteins by beta-o-linked N-acetylglucosamine (o-GlcNAc) moieties plays a significant role in signal transduction by modulating protein stability, protein-protein interactions, transactivation processes, and the enzyme activities of target proteins. Though various classes of proteins are known to be regulated by o-GlcNAc modification (o-GlcNAcylation), the mechanism that regulates o-linked GlcNAc transferase (OGT) activity remains unknown. Here, we report that potassium chloride-induced depolarization provokes the activation of OGT and subsequent o-GlcNAcylation of proteins in neuroblastoma NG-108-15 cells. Moreover, such an induction of protein o-GlcNAcylation was abolished by treating cells with either a voltage-gated calcium channel inhibitor or a calcium/calmodulin-dependent protein kinase (CaMK) inhibitor. In addition, CaMKIV was found to specifically phosphorylate and activate OGT in vivo and in vitro, which implies that CaMKIV is required for depolarization-induced activation of OGT. Furthermore, we found that OGT is involved in depolarization-induced and CaMKIV-dependent activation of activator protein-1 (AP-1) and subsequent tissue inhibitor of metalloproteinase-1 (Timp-1) gene expression. Taken together, our findings suggest that CaMKIV activated OGT, and OGT has an essential role on the process of CaMKIV-dependent AP-1 activation under depolarization in neuronal cells.

Comparison of re-exposure rates of intraoral radiographs between dental students and trained dental assistants in an oral and maxillofacial radiology clinic

OBJECTIVE

To compare the re-exposure rates of dental radiographs taken over a period of 1 year between dental students and trained dental assistants at a university-based oral and maxillofacial radiology clinic.

METHODS

Detailed records of the number and type of intraoral radiographs taken by the students and staff members and the number of re-exposures that were required from July 2003 to July 2004 were used. Statistical analyses were performed on the data.

RESULTS

A chi2 test showed that re-exposure rates of radiographic series between students and staff were statistically different. When comparing the students' re-exposure rates during each of the four quarters of their radiology rotation, one-way analysis of variance test showed that the results were not statistically significant for reduction in the number of re-exposures over the entire year.

CONCLUSIONS

There were significant differences in the re-exposure rates between staff dental assistants and students. Film re-exposure rates for the students during the four quarters were expected to decrease with time. Instead, the consistency of the re-exposure rates of the students during the four quarters demonstrates the need to recognize why the students did not perform better as the year progressed. The percentage of films that needed to be re-exposed by either group (students or the staff dental assistants) was not extremely high.

Repeated intratunical injection of adenovirus expressing transforming growth factor-beta1 in a rat induces penile curvature with tunical fibrotic plaque: a useful model for the study of Peyronie's disease

This study was undertaken to establish a Peyronie's disease model with penile curvature by using recombinant transforming growth factor-beta1 (TGF-beta1) protein or adenovirus (ad-TGF-beta1). Four-month-old male Sprague-Dawley rats were divided into seven groups (n = 18 per group): G1 received a single injection of saline into the tunica albuginea (0.1 mL); G2, repeated injections of ad-LacZ (days 0, 3, and 6; 1 x 10(10) particles/0.1 mL respectively); G3, a single injection of recombinant TGF-beta1 protein (700 ng/0.1 mL); G4, repeated injections of recombinant TGF-beta1 protein (days 0, 3 and 6; 700 ng/0.1 mL respectively); G5, a single injection of low-dose ad-TGF-beta1 (1 x 10(10) particles/0.1 mL); G 6, a single injection of high-dose ad-TGF-beta1 (3 x 10(10) particles/0.1 mL); and G7, repeated injections of low-dose ad-TGF-beta1 (days 0, 3, and 6; 1 x 10(10) particles/0.1 mL respectively). Penile curvature was evaluated 30, 45 and 60 days after treatment, and the penis was then harvested for histological examination. Repeated injection of low-dose ad-TGF-beta1 not only induced fibrous scar in the tunica, which lasted up to 60 days after injection, but also resulted in significant penile curvature by artificial erection test 45 days after treatment. A peculiar histological finding in this group was trapping of inflammatory cells in the tunica, subsequent fibrosis, and formation of cartilage and calcification as well as loss of elastin fibres. This model involving repeated injection of ad-TGF-beta1 may contribute to further investigation of the pathogenesis of Peyronie's disease and the development of new therapeutics targeting this pathway.

Reversal of drug resistance in breast cancer cells by transglutaminase 2 inhibition and nuclear factor-kappaB inactivation

Induction of transglutaminase 2 (TGase 2) by epidermal growth factor (EGF) in human breast cancer cells increases their oncogenic potential and chemoresistance. The role of TGase 2 in the development of these tumor-related phenotypes remains to be elucidated, but it has been shown that expression of a dominant-negative form of TGase 2 reverses EGF-mediated chemoresistance in breast cancer cells. We examined several different breast cancer cell lines, representing both EGF receptor (EGFR)-positive and EGFR-negative breast cancers, and found that doxorubicin-resistant cells had a higher level of TGase 2 compared with doxorubicin-sensitive cells independent of the EGFR expression level. TGase 2 inhibition increased the chemosensitivity of drug-resistant cells, concomitant with a decrease in nuclear factor-kappaB (NF-kappaB) activity. Increasing the level of TGase 2 in drug-sensitive cells by transient transfection reduced the level of inhibitory subunit alpha of NF-kappaB (IkappaBalpha) and increased NF-kappaB activity in these cells. Inhibition of TGase 2 in drug-resistant cells by RNA interference increased the levels of IkappaBalpha, and this correlated with a shift in the accumulation of NF-kappaB from the nucleus to the cytosol. We recently showed that TGase 2 activated NF-kappaB through polymerization and depletion of free IkappaBalpha during inflammation. Therefore, increased expression of TGase 2 and subsequent activation of NF-kappaB may contribute to drug resistance in breast cancer cells independently of EGF signaling.

Transglutaminase 2 Mediates Polymer Formation of I-κBα through C-terminal Glutamine Cluster

Recently we reported that transglutaminase 2 (TGase 2) activates nuclear factor-kappaB (NF-kappaB) independently of I-kappaB kinase (IKK) activation, by inducing cross-linking and protein polymer formation of inhibitor of nuclear factor-kappaBalpha (I-kappaBalpha). TGase 2 catalyzes covalent isopeptide bond formation between the peptide bound-glutamine and the lysine residues. Using matrix-assisted laser desorption ionization time-of-flight mass spectra analysis of I-kappaBalpha polymers cross-linked by TGase 2, as well as synthetic peptides in an in vitro competition assay, we identified a glutamine cluster at the C terminus of I-kappaBalpha (amino acids 266-268) that appeared to play a key role in the formation of I-kappaBalpha polymers. Although there appeared to be no requirement for specific lysine residues, we found a considerably higher preference for the use of lysine residues at positions 21, 22, and 177 in TGase 2-mediated cross-linking of I-kappaBalpha. We demonstrated that synthetic peptides encompassing the glutamine cluster at amino acid positions 266-268 reversed I-kappaBalpha polymerization in vitro. Furthermore, the depletion of free I-kappaBalpha in EcR/TG cells was completely rescued in vivo by transfection of mutant I-kappaBalphas in glutamine sites (Q266G, Q267G, and Q313G) as well as in a lysine site (K177G). These findings provide additional clues into the mechanism by which TGase 2 contributes to the inflammatory process via activation of NF-kappaB.

Smad6 negatively regulates interleukin 1-receptor-Toll-like receptor signaling through direct interaction with the adaptor Pellino-1

Transforming growth factor-beta1 (TGF-beta1) is a potent cytokine with pleiotropic effects, including anti-inflammatory activity. Here we show that the signaling protein Smad6 bound to Pellino-1, an adaptor protein of mammalian interleukin 1 receptor (IL-1R)-associated kinase 1 (IRAK1), and thereby promoted TGF-beta-mediated anti-inflammatory effects. Smad6-Pellino-1 interaction abrogated signaling mediated by a complex of IRAK1, Pellino-1 and adaptor protein TRAF6 that formed after stimulation by IL-1beta treatment. Blockade of IRAK1-Pellino-1-TRAF6 signaling prevented degradation of the inhibitor IkappaBalpha and subsequent nuclear translocation of transcription factor NF-kappaB and thus expression of proinflammatory genes. 'Knockdown' of endogenous Smad6 expression by RNA interference reduced anti-inflammatory activity mediated by TGF-beta1 or the TGF-beta family member BMP-4. Thus Smad6 is a critical mediator of the TGF-beta-BMP pathway that mediates anti-inflammatory activity and negatively regulates IL-1R-Toll-like receptor signals.

Changes in gene expression with increased transglutaminase 2 in a SH-SY5Y cell line

Previously we showed that the overexpression of transglutaminase 2 (TGase 2) resulted in activation of NF-kappaB through polymerization of I-kappaBalpha. To explore the pathway of TGase 2-mediated NF-kappaB activation, a transcriptomic microarray analysis was performed. In a SH-SY5Y cell line transfected with TGase 2, 24 genes were up-regulated at least 1.6-fold and 26 genes were down-regulated, as compared to the wild-type cell line. Detailed analysis resulted in the identification of target genes involved in regulating inflammation, including tribbles homolog 3, peroxiredoxin 4, neuropeptide Y, galanin, and vasoactive intestinal peptide. Our data demonstrate that the increase in TGase 2 in the neuroblastoma causes functional changes in transcriptional regulation, especially in genes associated with inflammation. These changes in gene expression caused by increases in TGase 2 activity may contribute to the pathophysiologic processes of inflammatory diseases.

Comparative study on biologic and immunologic characteristics of the pancreas islet cell between 24 degrees C and 37 degrees C culture in the rat

The aim of this study was to investigate the effect of culture at 24 degrees C on cell viability, cellular function, immunogenicity, and cytokine profiles of rat pancreatic islets. Pancreatic islets were isolated from Lewis rats and cultured at either 24 degrees C or 37 degrees C for 14 days. Islet recovery was counted as islet equivalents; islet viability was examined with fluorescent vital staining. Islet function was measured with a glucose stimulation test. Annexin V, and MHC class I and II expression were measured using flow cytometric assay for apoptosis and immunogenicity, respectively. Lymphocyte cell proliferation was examined with WST-1 proliferation assay. Cytokine profiles were analyzed with quantitative real time RT-PCR. All these parameters were measured on 1, 3, 5, 7 and 14 culture days after islet isolation. Islet recovery was higher in islets cultured at 24 degrees C than 37 degrees C without a change in viability. Insulin secretion after glucose stimulation was more effective in 24 degrees C culture conditions. Decreased apoptotic cell death was demonstrated in 24 degrees C cultured islets. Both MHC class I and II expression on islets and lymphocyte proliferation upon coculture with islets were less prominent in 24 degrees C cultured islets. TNF-alpha expression was lower in islets cultured at 24 degrees C than in islets cultured at 37 degrees C. Both IL-1beta and IL-10 cytokine expressions were similar under both culture conditions. This study demonstrated that cell recovery and function are increased in islets cultured at 24 degrees C than those at 37 degrees C with decreased antigenicity and proinflammatory cytokine expression.

Combined Angiopoietin-1 and vascular endothelial growth factor gene transfer restores cavernous angiogenesis and erectile function in a rat model of hypercholesterolemia

Hypercholesterolemia-related endothelial cell dysfunction and decreased endothelium-derived nitric oxide formation may account for impaired angiogenesis and subsequent erectile dysfunction. Angiopoietin-1 (Ang1) is a critical angiogenic factor for vascular maturation and enhances vascular endothelial growth factor (VEGF)-induced angiogenesis in a complementary manner. We hypothesized that combined adenovirus-delivered human Ang1 (ad-Ang1) and VEGF165 (ad-VEGF165) gene transfer might promote angiogenesis cooperatively in a rat model of hypercholesterolemic erectile dysfunction and result in a recovery of erectile function. Ad-Ang1 and ad-VEGF165 were injected either alone or in combination into the corpus cavernosum of the penis. Combined gene transfer of both ad-Ang1 and ad-VEGF165 significantly increased cavernous angiogenesis, eNOS phosphorylation, and cGMP expression compared with that in the groups treated with either therapy alone. Erectile function, as evaluated by electrical stimulation of the cavernous nerve 2 and 8 weeks after treatment, was completely restored in the combined treatment group, whereas intracavernous injection of either ad-Ang1 or ad-VEGF165 alone elicited partial improvement. The results indicate that combined application of angiogenic factors may enhance cavernous angiogenesis cooperatively by reinforcing the endothelium both structurally and functionally, which results in an additive effect on erectile function in hypercholesterolemic rats.

Pioglitazone, a synthetic ligand for PPARγ, induces apoptosis in RB-deficient human colorectal cancer cells

No published data are available about the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and the role of PPARgamma in retinoblastoma protein (RB)-deficient human colorectal cancer (CRC) cells (SNU-C4 and SNU-C2A). Our aim was to investigate whether PPARgamma is expressed in SNU-C4 and SNU-C2A cells and to elucidate possible molecular mechanisms underlying the effect of pioglitazone, a synthetic ligand for PPARgamma, on cell growth in these cell lines. RT-PCR and Western blot analysis showed that both human CRC cell lines expressed PPARgamma mRNA and protein. Pioglitazone inhibited the cell growth of both cell lines through G2/M phase block and apoptosis. In addition, pioglitazone caused a down-regulation of the X chromosome-linked inhibitor of apoptosis (XIAP), Bcl-2, and cyclooxygenase-2 (COX-2) under conditions leading to PPARgamma down-regulation. These results suggest that pioglitazone may have therapeutic relevance or significance in the treatment of human CRC, and the down-regulation of XIAP, Bcl-2, and COX-2 may contribute to pioglitazone-induced apoptosis in these and other RB-deficient cell lines and tumors.

Effects of feeding antibiotic-free creep feed supplemented with oligofructose, probiotics or synbiotics to suckling piglets increases the preweaning weight gain and composition of intestinal microbiota

The objective of this study was to determine whether feeding an antibiotic-free creep feed supplemented with either oligofructose, probiotics or synbiotics to suckling piglets influences growth performance, the gut microflora, gut morphology and hematological traits at weaning. Twenty sows with 10 piglets each were randomly assigned to one of four treatments. The treatments consisted of a control (antibiotic-free) diet, 0.2% oligofructose (OF), 0.3% probiotics or 0.5% synbiotics (mixture of 0.2% OF+0.3% probiotics). Piglets were offered the diet ad libitum from 7 d after birth until one day after weaning (21 d of age). At the day after weaning, blood samples were collected from the jugular vein to determine the immune response. Digesta samples of the ileum and colon were collected to determine the microbial composition. Tissue segments from the duodenum and ileum were collected for morphometric measurements of the small intestine. The average daily weight gain was significantly higher for piglets fed the OF or synbiotics diet compared with the pigs fed the control diet. The hematological traits (the concentration of lymphocytes and neutrophils in whole blood) were not affected by the diet. Piglets fed the OF, probiotics or synbiotics diet had a significantly decreased number of total coliform bacteria in the colon. Feeding OF, probiotics or synbiotics significantly increased the population of bifidobacteria in the ileum compared to the control. In the colon, the probiotics and synbiotics diet significantly increased the number of bifidobacteria compared with the control diet. The results of this experiment showed that supplementation of oligofructose or synbiotics to an antibiotic-free creep feed during the preweaning period affected gut microbial population and performance of piglets.

Specific Regression of Human Cancer Cells by Ribozyme-Mediated Targeted Replacement of Tumor-Specific Transcript

In this study, we describe a novel approach to human cancer therapy that is based upon trans-splicing ribozyme-mediated replacement of cancer-specific RNAs with new transcripts that exert therapeutic activities. We have developed a specific ribozyme that can reprogram human telomerase reverse transcriptase (hTERT) RNA to induce transgene activity selectively in cancer cells that express the RNA. The ribozyme-mediated triggering of the transgene expression was accomplished via a high-fidelity trans-splicing reaction with the targeted residue in the hTERT-expressing cells. The ribozyme also induced cytotoxic activity in various hTERT-expressing cancer cells, hence selectively retarding the growth of those cells. Efficient and specific cell regression was also detected with ganciclovir (GCV) treatment only in hTERT-positive cancer cells, which were established to express stably the specific ribozyme that contains the herpes simplex virus thymidine kinase (HSV-tk) gene. Tissue-specific expression of the ribozyme could further augment the target specificity of the ribozyme. Importantly, we observed efficient regression of tumors with GCV treatment in mice that had been inoculated subcutaneously with hTERT-positive cancer cells that stably expressed the specific ribozyme that contains HSV-tk. These results suggest that the hTERT RNA-targeting trans-splicing ribozyme could be a powerful agent for tumor-targeted specific gene therapy.

Apoptosis of mink lung epithelial cells by co-treatment of low-dose staurosporine and transforming growth factor-beta1 depends on the enhanced TGF-beta signaling and requires the decreased phosphorylation of PKB/Akt

We demonstrate how co-treatment of low-dose staurosporine (STS) and TGF-beta1, which alone have little effect on cell death, markedly induces apoptosis in Mv1Lu mink lung epithelial cells, but not in its clonal variant R1B cells lacking functional TGF-beta signaling. This process was associated with mitochondria-dependent apoptosis and the enhanced TGF-beta/Smad signaling in Mv1Lu cells. When R1B cells were infected with adenovirus carrying wild-type ALK5, a functional TGF-beta type I receptor gene, the apoptotic cell death was significantly restored in these cells following co-treatment of low-dose STS and TGF-beta1. Treatment of Mv1Lu cells with both low-dose STS and TGF-beta1 decreased the activity of phospho-Akt, which is involved in cell survival signal. In addition, pre-treatments of PI3 kinase inhibitors, LY294002 and wortmannin, further increased the apoptosis of MvlLu cells induced by co-treatment of low-dose STS and TGF-beta1. And overexpression of constitutively active Akt (myr-Akt) using adenoviral expression system inhibited the apoptotic cell death of Mv1Lu cells by about 50% upon co-treatment of low-dose STS and TGF-beta1. These results suggest that co-treatment of low-dose STS and TGF-beta1 induces apoptosis of mink lung epithelial cells by enhancing TGF-beta signaling and in part suppressing cytoprotective signaling.

Increased Expression of Metallothionein Is Associated with Irinotecan Resistance in Gastric Cancer

To gain insight into clinically relevant mechanisms of irinotecan resistance, we undertook oligonucleotide microarray analyses on paired malignant effusion samples obtained from eight gastric cancer patients treated with weekly irinotecan. Pretreatment and posttreatment (48 h) effusion samples were obtained for each patient, and the change in expression profile was compared between clinical responders and nonresponders. When differences in the expression of genes were examined using SAM (Significance Analysis of Microarrays) software, five isoforms of the metallothionein family were identified to have significantly higher signal log ratios in five nonresponders, compared with three responders. Compared with control cells, metallothionein 1X (MT1X)-transfected AGS cells showed a 1.4-fold higher irinotecan IC(50) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and tended to form more colonies. These findings collectively suggest that irinotecan-induced up-regulation of metallothionein might be associated with irinotecan resistance in patients with gastric cancer, although it remains to be confirmed in a larger data set.

NHERF2 specifically interacts with LPA2 receptor and defines the specificity and efficiency of receptor-mediated phospholipase C-beta3 activation

Lysophosphatidic acid (LPA) activates a family of cognate G protein-coupled receptors and is involved in various pathophysiological processes. However, it is not clearly understood how these LPA receptors are specifically coupled to their downstream signaling molecules. This study found that LPA(2), but not the other LPA receptor isoforms, specifically interacts with Na(+)/H(+) exchanger regulatory factor2 (NHERF2). In addition, the interaction between them requires the C-terminal PDZ domain-binding motif of LPA(2) and the second PDZ domain of NHERF2. Moreover, the stable expression of NHERF2 potentiated LPA-induced phospholipase C-beta (PLC-beta) activation, which was markedly attenuated by either a mutation in the PDZ-binding motif of LPA(2) or by the gene silencing of NHERF2. Using its second PDZ domain, NHERF2 was found to indirectly link LPA(2) to PLC-beta3 to form a complex, and the other PLC-beta isozymes were not included in the protein complex. Consistently, LPA(2)-mediated PLC-beta activation was specifically inhibited by the gene silencing of PLC-beta3. In addition, NHERF2 increases LPA-induced ERK activation, which is followed by cyclooxygenase-2 induction via a PLC-dependent pathway. Overall, the results suggest that a ternary complex composed of LPA(2), NHERF2, and PLC-beta3 may play a key role in the LPA(2)-mediated PLC-beta signaling pathway.

DNA microarray analysis of the correlation between gene expression patterns and acquired resistance to 5-FU/cisplatin in gastric cancer

The mechanisms of intrinsic and/or acquired anti-cancer drug resistance have been described in in vitro resistance models, but the clinical relevance has remained undefined. We undertook a prospective study to identify correlations between gene expression and clinical resistance to 5-FU/cisplatin. We compared expression profiles from gastric cancer endoscopic biopsy specimens obtained at a chemosensitive state (partial remission after 5-FU/cisplatin) with those obtained at a refractory state (disease progression), using Affymetrix oligonucleotide microarray technology (U133A). Using 119 discriminating probes and a cross-validation approach, we were able to correctly identify the chemo-responsiveness of 7 pairs of training samples and 1 independent test pair. These exploratory data demonstrate that the gene expression profiles differ between chemosensitive and refractory state gastric cancer biopsy samples.