Wnt/ß-catenin modulating drugs regulate somatostatin receptor expression and internalization of radiolabelled octreotide in neuroendocrine tumor cells.

BACKGROUND: Differentiated neuroendocrine tumors (NETs) express somatostatin receptors (SSTRs), targets for therapy with either unlabeled or radioactively labeled somatostatin analogs (SSA). Associated with worse prognosis, dedifferentiated NET loose SSTR expression, which may be linked to deregulation of Wnt/ß-catenin signaling on an intracellular level. The aim of the present study was to investigate the effect of Wnt/ß-catenin signaling pathway alterations on SSTR expression and its function in NET. METHODS: The NET cell lines BON-1 and QGP-1 were incubated with the Wnt-inhibitors 5-aza-2'-deoxycytidine (5-aza-CdR), Quercetin, or Niclosamide, or the Wnt activator lithium chloride (LiCl). Expression of SSTR1, SSTR2, and SSTR5 was determined by quantitative RT-PCR (qRT-PCR), immunocytomicroscopy and western blot. Changes in the Wnt pathway were analyzed by qRT-PCR of selected target genes and the TaqMan Array Human WNT Pathway. Receptor-associated function was determined by measuring the cellular uptake of [125I-Tyr3] octreotide. RESULTS: The mRNAs of SSTRs 1-5 were expressed in both cell lines. Wnt inhibitors caused downregulation of Wnt target genes, while 5-aza-CdR had the highest inhibitory effect. LiCl lead to an upregulation of Wnt genes, which was more marked in QGP-1 cells. SSTR expression increased in both cell lines upon Wnt inhibition. All three Wnt inhibitors lead to a marked increase in the specific uptake of [125I-Tyr3]octreotide, with 5-aza-CdR showing the greatest effect (increase by more than 50% in BON-1 cells), while a decreased uptake of [125I-Tyr3]octreotide was seen upon activation of Wnt signaling by LiCl. CONCLUSIONS: We demonstrate here that Wnt signaling orchestrates SSTR expression and function in a preclinical NET model. Wnt inhibition increases [125I-Tyr3]octreotide uptake offering an opportunity to enhance the efficacy of SSTR-targeted theranostic approaches.

CXCR4-Directed PET/CT in Patients with Newly Diagnosed Neuroendocrine Carcinomas.

We aimed to elucidate the diagnostic potential of the C-X-C motif chemokine receptor 4 (CXCR4)-directed positron emission tomography (PET) tracer 68Ga-Pentixafor in patients with poorly differentiated neuroendocrine carcinomas (NEC), relative to the established reference standard 18F-FDG PET/computed tomography (CT). In our database, we retrospectively identified 11 treatment-naïve patients with histologically proven NEC, who underwent 18F-FDG and CXCR4-directed PET/CT for staging and therapy planning. The images were analyzed on a per-patient and per-lesion basis and compared to immunohistochemical staining (IHC) of CXCR4 from PET-guided biopsies. 68Ga-Pentixafor visualized tumor lesions in 10/11 subjects, while18F-FDG revealed sites of disease in all 11 patients. Although weak to moderate CXCR4 expression could be corroborated by IHC in 10/11 cases, 18F-FDG PET/CT detected significantly more tumor lesions (102 vs. 42; total lesions, n = 107; p < 0.001). Semi-quantitative analysis revealed markedly higher 18F-FDG uptake as compared to 68Ga-Pentixafor (maximum and mean standardized uptake values (SUV) and tumor-to-background ratios (TBR) of cancerous lesions, SUVmax: 12.8 ± 9.8 vs. 5.2 ± 3.7; SUVmean: 7.4 ± 5.4 vs. 3.1 ± 3.2, p < 0.001; and, TBR 7.2 ± 7.9 vs. 3.4 ± 3.0, p < 0.001). Non-invasive imaging of CXCR4 expression in NEC is inferior to the reference standard 18F-FDG PET/CT.

Wnt/ß-Catenin Signaling Regulates CXCR4 Expression and [68Ga] Pentixafor Internalization in Neuroendocrine Tumor Cells.

Loss of Somatostatin Receptor 2 (SSTR2) expression and rising CXC Chemokine Receptor Type 4 (CXCR4) expression are associated with dedifferentiation in neuroendocrine tumors (NET). In NET, CXCR4 expression is associated with enhanced metastatic and invasive potential and worse prognosis but might be a theragnostic target. Likewise, activation of Wnt/ß-catenin signaling may promote a more aggressive phenotype in NET. We hypothesized an interaction of the Wnt/ß-catenin pathway with CXCR4 expression and function in NET. The NET cell lines BON-1, QGP-1, and MS-18 were exposed to Wnt inhibitors (5-aza-CdR, quercetin, and niclosamide) or the Wnt activator LiCl. The expressions of Wnt pathway genes and of CXCR4 were studied by qRT-PCR, Western blot, and immunohistochemistry. The effects of Wnt modulators on uptake of the CXCR4 ligand [68Ga] Pentixafor were measured. The Wnt activator LiCl induced upregulation of CXCR4 and Wnt target gene expression. Treatment with the Wnt inhibitors had opposite effects. LiCl significantly increased [68Ga] Pentixafor uptake, while treatment with Wnt inhibitors decreased radiopeptide uptake. Wnt pathway modulation influences CXCR4 expression and function in NET cell lines. Wnt modulation might be a tool to enhance the efficacy of CXCR4-directed therapies in NET or to inhibit CXCR4-dependent proliferative signaling. The underlying mechanisms for the interaction of the Wnt pathway with CXCR4 expression and function have yet to be clarified.

Use of Gene Expression Analysis for Discrimination of Primary and Secondary Adenocarcinoma of the Liver.

BACKGROUND: Due to late diagnosis and resistance to chemotherapy, most patients with cholangiocarcinoma have an unfavorable prognosis. Despite the use of immunohistochemistry (IHC) in clinical routine, differentiation between intrahepatic cholangiocarcinoma (ICC) and secondary adenocarcinomas of the liver is frequently not clear, leading to false diagnosis and treatment decisions. METHODS: Oligonucleotide microarrays (Affymetrix Hu133A©) were used for gene expression analysis of ICC (n = 11) and secondary adenocarcinomas (colorectal metastases; n = 6). By two-dimensional cluster analysis a specific gene expression profile of these tumors was established and confirmed by real-time polymerase chain reaction and IHC. RESULTS: A total of 338 genes were significantly dysregulated (gene expression/fc ≥2; dysregulation in ≥60%) in both tumor groups. Using two-dimensional cluster analysis a fast, clear, and reproducible differentiation between ICC and colorectal metastases was possible in all cases. As potential biomarkers for differentiation, twelve genes (ICC: KRT7, DBN1, LCTB, LIF, STK17A, PIGF; metastases: TDGF1, HOXA9, TFF3, MYB, ABP1, BCL11A) were detected and will be used for further investigations. CONCLUSIONS: A specific gene expression profile for discrimination of primary and secondary adenocarcinoma of the liver could be established. In addition, marker genes for both cancers and their potential use as discrimination markers in clinical routine were also described partially for the first time.

Structured Diagnostic Approach and Risk Assessment in Mucous Membrane Pemphigoid with Oesophageal Involvement.

Oesophageal involvement in mucous membrane pemphigoid is considered rare, but it may be underdiagnosed. To assess the incidence of oesophageal involvement in a group of patients with newly diagnosed mucous membrane pemphigoid we retrospectively analysed the medical records of 30 consecutive patients with mucous membrane pemphigoid diagnosed between 2006 and 2016 at the Department of Dermatology, University Hospital Würzburg. Twenty-one patients (70%) reported symptoms indicative of oesophageal mucous membrane pemphigoid. Twelve patients (40%) underwent oesophagogastroduodenoscopy, and oesophageal pathology compatible with mucous membrane pemphigoid was endoscopically found in 9 cases (30%). In all patients indirect and direct immunofluorescence were performed. Patients with and without oesophageal involvement did not differ with regard to the results of indirect immunofluorescence on salt-split human skin and monkey oesophagus. Study results demonstrate the necessity of a standardized diagnostic work-up, including adequate tissue samples for direct immunofluorescence, to prevent underdiagnosis of oesophageal mucous membrane pemphigoid.

Subclassification and Detection of New Markers for the Discrimination of Primary Liver Tumors by Gene Expression Analysis Using Oligonucleotide Arrays.

BACKGROUND/AIMS: The failure to correctly differentiate between intrahepatic cholangiocarcinoma (CC) and hepatocellular carcinoma (HCC) is a significant clinical problem, particularly in terms of the different treatment goals for both cancers. In this study a specific gene expression profile to discriminate these two subgroups of liver cancer was established and potential diagnostic markers for clinical use were analyzed. METHODS: To evaluate the gene expression profiles of HCC and intrahepatic CC, Oligonucleotide arrays (AffymetrixU133A) were used. Overexpressed genes were checked for their potential use as new markers for discrimination and their expression values were validated by reverse transcription polymerase chain reaction and immunohistochemistry analyses. RESULTS: 695 genes/expressed sequence tags (ESTs) in HCC (245 up-/450 down-regulated) and 552 genes/ESTs in CC (221 up-/331 down-regulated) were significantly dysregulated (p＜0.05, fold change >2, ≥70%). Using a supervised learning method, and one-way analysis of variance a specific 270-gene expression profile that enabled rapid, reproducible differentiation between both tumors and nonmalignant liver tissues was established. A panel of 12 genes (e.g., HSP90ß, ERG1, GPC3, TKT, ACLY, and NME1 for HCC; SPT2, T4S3, CNX43, TTD1, HBD01 for CC) were detected and partly described for the first time as potential discrimination markers. CONCLUSIONS: A specific gene expression profile for discrimination of primary liver cancer was identified and potential marker genes with feasible clinical impact were described.

Imaging of Chemokine Receptor 4 Expression in Neuroendocrine Tumors - a Triple Tracer Comparative Approach.

C-X-C motif chemokine receptor 4 (CXCR4) and somatostatin receptors (SSTR) are overexpressed in gastro-entero-pancreatic neuroendocrine tumors (GEP-NET). In this study, we aimed to elucidate the feasibility of non-invasive CXCR4 positron emission tomography/computed tomography (PET/CT) imaging in GEP-NET patients using [68Ga]Pentixafor in comparison to 68Ga-DOTA-D-Phe-Tyr3-octreotide ([68Ga]DOTATOC) and 18F-fluorodeoxyglucose ([18F]FDG). Twelve patients with histologically proven GEP-NET (3xG1, 4xG2, 5xG3) underwent [68Ga]DOTATOC, [18F]FDG, and [68Ga]Pentixafor PET/CT for staging and planning of the therapeutic management. Scans were analyzed on a patient as well as on a lesion basis and compared to immunohistochemical staining patterns of CXCR4 and somatostatin receptors SSTR2a and SSTR5. [68Ga]Pentixafor visualized tumor lesions in 6/12 subjects, whereas [18F]FDG revealed sites of disease in 10/12 and [68Ga]DOTATOC in 11/12 patients, respectively. Regarding sensitivity, SSTR-directed PET was the superior imaging modality in all G1 and G2 NET. CXCR4-directed PET was negative in all G1 NET. In contrast, 50% of G2 and 80% of G3 patients exhibited [68Ga]Pentixafor-positive tumor lesions. Whereas CXCR4 seems to play only a limited role in detecting well-differentiated NET, increasing receptor expression could be non-invasively observed with increasing tumor grade. Thus, [68Ga]Pentixafor PET/CT might serve as non-invasive read-out for evaluating the possibility of CXCR4-directed endoradiotherapy in advanced dedifferentiated SSTR-negative tumors.

Gene-expression Analysis Identifies Specific Patterns of Dysregulated Molecular Pathways and Genetic Subgroups of Human Hepatocellular Carcinoma.

BACKGROUND: Hepatocellular carcinoma comprises of a group of heterogeneous tumors of different etiologies. The multistep process of liver carcinogenesis involves various genetic and phenotypic alterations. The molecular pathways and driver mutations involved are still under investigation. MATERIALS AND METHODS: DNA micorarray technology was used to identify differentially expressed genes between human hepatocarcinoma and non-tumorous liver tissues to establish a unique specific gene-expression profile independent of the underlying liver disease. The validity of this global gene-expression profile was tested for its robustness against biopsies from other liver entities (cirrhotic and non-cirrhotic liver) by diagnosing HCC in blinded samples. RESULTS: Most of the consistently and strongly overexpressed genes were related to cell-cycle regulation and DNA replication [27 genes, e.g. cyclin B1, karyopherin alpha 2 (KPNA2), cyclin-dependent kinase 2 (CDC2)], G-protein depending signaling [e.g. Rac GTPase activating protein 1 (RACGAP1), Rab GTPase YPT1 homolog (RAB1), and ADP-ribosylation factor-like 2 (ARL2)] and extracellular matrix re-modelling or cytoskeleton structure [22 genes, e.g. serine proteinase inhibitor 1 kazal-type (SPINK1), osteopontin (OPN), secreted protein acidic and rich in cysteine (SPARC), collagen type 1 alpha2 (COL1A2), integrin alpha6 (ITGA6), and metalloproteinase 12 (MMP12)]. Furthermore, significantly differentially expressed genes (e.g. calcium-binding proteins, G-proteins, oncofetal proteins) in relation to tumor differentiation were detected using gene-expression analysis. CONCLUSION: It is suggested that these significantly dysregulated genes are highly specific and potentially utilizable as prognostic markers and may lead to a better understanding of human hepatocarcinogenesis.

The impact of 177Lu-octreotide therapy on 99mTc-MAG3 clearance is not predictive for late nephropathy.

Peptide Receptor Radionuclide Therapy (PRRT) for the treatment of neuroendocrine tumors may lead to kidney deterioration. This study aimed to evaluate the suitability of 99mTc-mercaptoacetyltriglycine (99mTc--MAG3) clearance for the early detection of PRRT-induced changes on tubular extraction (TE). TE rate (TER) was measured prior to 128 PRRT cycles (7.6±0.4 GBq 177Lu-octreotate/octreotide each) in 32 patients. TER reduction during PRRT was corrected for age-related decrease and analyzed for the potential to predict loss of glomerular filtration (GF). The GF rate (GFR) as measure for renal function was derived from serum creatinine. The mean TER was 234 ± 53 ml/min/1.73 m² before PRRT (baseline) and 221 ± 45 ml/min/1.73 m² after a median follow-up of 370 days. The age-corrected decrease (mean: -3%, range: -27% to +19%) did not reach significance (p=0.09) but significantly correlated with the baseline TER (Spearman p=-0.62, p<0.001). Patients with low baseline TER showed an improved TER after PRRT, high decreases were only observed in individuals with high baseline TER. Pre-therapeutic TER data were inferior to plasma creatinine-derived GFR estimates in predicting late nephropathy. TER assessed by 99mTc-MAG3-clearance prior to and during PRRT is not suitable as early predictor of renal injury and an increased risk for late nephropathy.

Gene expression analysis for evaluation of potential biomarkers in hepatocellular carcinoma.

BACKGROUND: The poor prognosis of hepatocellular carcinoma (HCC) and the lack of specific screening markers underline the need for new biomarkers for human hepatocarcinogenesis. MATERIALS AND METHODS: We investigated 10 postulated biomarkers for HCC (AFP, GPC3, OPN, IGF1, HGF, SPINK1, KPNA, FUCA1, CgA, HSP90) with microarray gene expression analysis and real-time polymerase chain reaction (RT-PCR) in HCC tissues of different etiologies. RESULTS: Four candidate genes (FUCA1, HGF, IGF1, CgA) showed low median fold changes (fc) of expression compared to corresponding non-malignant liver tissues (fc range=0.2-0.8; maximum 15% of samples). The classic biomarker, alpha-fetoprotein (AFP), was significantly over-expressed (fc=2.4) in 30% of tumors. High tumor AFP expression was associated with significantly elevated serum AFP concentrations (>90% of cases). Five genes (OPN, SPINK1, GPC3, HSP90, KNPA2) showed significantly higher expression than AFP in 64% to 82% of samples (median fc range=2.9-8.3). RT-PCR analyses gave similar results. CONCLUSION: Unlike previous studies, our results did not confirm FUCA1, HGF, IGF1 or CgA as potential markers for HCC. In contrast, OPN, SPINK1, GPC3 and KNPA2 were significantly over-expressed in HCC tissues. These genes may be useful in developing future biomarkers and therapeutic strategies for HCC.

Overexpression of tumor-associated trypsin inhibitor (SPINK1/TATI) in hepatitis C-associated hepatocellular carcinoma: potential implications for viral hepatocarcinogenesis.

BACKGROUND: The molecular pathomechanisms leading to hepatitis C virus (HCV)-induced hepatocarcinogenesis remain unclear. This study investigated the molecular pathways and key genes underlying HCV-positive hepatocellular carcinoma (HCC) using gene expression profiling. METHODS: Oligonucleotide arrays (Affymetrix HU133A) were used to determine and compare the tissue-specific gene expression profiles in 39 cases of HCV-positive or -negative HCC and non-malignant liver tissue. The expression values of the most overexpressed genes were validated by real-time polymerase chain reaction (RT-PCR). RESULTS: 837 genes or expressed sequence tags (ESTs) were significantly differently expressed in HCV-positive HCC versus healthy tissue: 414 were upregulated and 423 were downregulated (p < 0.05; > 2-fold change in ≥ 70% of the samples). A specific gene expression profile for HCV-positive HCC was obtained using 2-dimensional cluster analysis and was confirmed using supervised neuronal network modeling. The most consistently overexpressed gene coded for serine protease inhibitor Kazal-type 1 (SPINK1)/tumor-associated trypsin inhibitor (TATI) (median fold change, 19.7; significantly overexpressed in 90% of the samples). SPINK1/TATI was coregulated with matrix metalloproteinases (MMPs) and their natural inhibitors (tissue inhibitors of metalloproteinases (TIMPs)). CONCLUSIONS: Gene expression profiling identified specific dysregulated molecular pathways and SPINK1/TATI as the most overexpressed gene in HCV-positive HCC. These data highlight the importance of SPINK1/TATI as a tumor marker for HCV-induced HCC and may lead to a better understanding of HCV-induced hepatocarcinogenesis.

Complete pathological remission of locally advanced, unresectable pancreatic cancer (LAPC) after intensified neoadjuvant chemotherapy.

BACKGROUND: Unresectable locally advanced pancreatic cancer (LAPC) has an extremely poor prognosis. Results of neoadjuvant (radio-)chemotherapy approaches aiming at achieving resectability are currently not satisfactory. CASE REPORT: We report the case of a 67-year-old woman with histologically confirmed pancreas carcinoma that was not resectable on first surgical exploration who achieved a well-documented complete pathological remission (pCR). The carcinoma became resectable after consecutive neoadjuvant treatment with nanoparticle albumin-bound (nab)-paclitaxel/gemcitabine and FOLFIRINOX chemotherapy regimens. CONCLUSION: This is the first reported LAPC case in which neoadjuvant chemotherapy alone has been shown to lead to demonstrated pCR. CA19-9 levels, but not imaging criteria, were useful for response prediction and timing of the Whipple's procedure. The findings in this case suggest possible conceptual changes in the treatment approach for LAPC, and indicate that the new effective chemotherapy regimens should be integrated into clinical trials for LAPC.

Improvement of neurocognitive function in responders to an antiviral therapy for chronic hepatitis C.

UNLABELLED: Earlier studies have suggested neurocognitive impairment in patients with chronic hepatitis C virus (HCV) infection even before liver cirrhosis has developed. Since these deficits might be reversible after successful antiviral therapy, we analyzed the long-term course of neurocognitive parameters in HCV patients with and without successful virus elimination by an interferon-based antiviral treatment. In a multicenter study including 168 HCV patients receiving antiviral therapy (peginterferon alpha-2b and ribavirin) we performed a long-term follow-up of neurocognitive performance before and after treatment. Neurocognitive function was psychometrically assessed using the computer-aided TAP (Test Battery of Attentional Performance). When tested at least 12 months after termination of antiviral treatment, patients with sustained virologic response (SVR) had improved significantly as compared to their pretreatment performance in three of five TAP subtasks (vigilance, P < 0.001; shared attention: optical task, P < 0.001; working memory, P < 0.001). Patients who failed to eradicate the virus, however, showed no significant long-term changes in neurocognitive performance in all five subtasks assessed (0.194 < P < 0.804). In the posttreatment evaluation, neurocognitive function was significantly better in responders to the antiviral therapy as compared to nonresponders. CONCLUSION: Successful eradication of HCV leads to a significant improvement of relevant aspects of attentional and neurocognitive performance, indicating that the neurocognitive impairment caused by chronic HCV infection is potentially reversible. This therefore suggests an added therapeutic benefit of antiviral treatment in HCV infection. Improvement of neurocognitive function may be an additional treatment indication in patients with HCV. (HEPATOLOGY 2013;58:497-504).

LOH and copy neutral LOH (cnLOH) act as alternative mechanism in sporadic colorectal cancers with chromosomal and microsatellite instability.

BACKGROUND AND AIMS: Tumor suppressor genes are often located in frequently deleted chromosomal regions of colorectal cancers (CRCs). In contrast to microsatellite stable (MSS) tumors, only few loss of heterozygosity (LOH) studies were performed in microsatellite instable (MSI) tumors, because MSI carcinomas are generally considered to be chromosomally stable and classical LOH studies are not feasible due to MSI. The single nucleotide polymorphism (SNP) array technique enables LOH studies also in MSI CRC. The aim of our study was to analyse tissue from MSI and MSS CRC for the existence of (frequently) deleted chromosomal regions and tumor suppressor genes located therein. METHODS AND RESULTS: We analyzed tissues from 32 sporadic CRCs and their corresponding normal mucosa (16 MSS and 16 MSI tumors) by means of 50K SNP array analysis. MSS tumors displayed chromosomal instability that resulted in multiple deleted (LOH) and amplified regions and led to the identification of MTUS1 (8p22) as a candidate tumor suppressor gene in this region. Although the MSI tumors were chromosomally stable, we found several copy neutral LOHs (cnLOH) in the MSI tumors; these appear to be instrumental in the inactivation of the tumor suppressor gene hMLH1 and a gene located in chromosomal region 6pter-p22. DISCUSSION: Our results suggest that in addition to classical LOH, cnLOH is an important mutational event in relation to the carcinogenesis of MSS and MSI tumors, causing the inactivation of a tumor suppressor gene without copy number alteration of the respective region; this is crucial for the development of MSI tumors and for some chromosomal regions in MSS tumors.

Platelet serotonin (5-HT) levels in interferon-treated patients with hepatitis C and its possible association with interferon-induced depression.

BACKGROUND & AIMS: Interferon-associated depression is a frequent side effect of antiviral therapy for chronic hepatitis C. The aim of the present study was to investigate the correlation between platelet serotonin (5-hydroxytryptamine, 5-HT) concentrations and IFN-induced depression. METHODS: The study represents a secondary analysis of a previously published trial on the efficacy of SSRI medication in HCV patients on IFN therapy. Ninety-three patients were longitudinally assessed for depression and platelet serotonin. Evaluation time points were: prior to IFN therapy, at weeks 4, 12, and 24 of IFN treatment, and 4 weeks after antiviral treatment. Depression was assessed using the Hospital Anxiety and Depression Scale (HADS). Platelet serotonin concentrations were measured by ELISA. RESULTS: Platelet serotonin concentrations were significantly decreased during interferon therapy (p=0.001) in 74 of the 93 patients (79.6%). Clinically relevant depression occurred in 33.3% of patients - however, IFN-induced depression was not significantly linked to either baseline 5-HT concentrations or kinetics. In the subgroup of patients with IFN-induced depression who received the selective serotonin reuptake inhibitor (SSRI) citalopram (20 mg daily, n=17), serotonin levels declined further during anti-depressant medication, becoming statistically significant within the first 2 weeks (p<0.001) of SSRI treatment. CONCLUSIONS: We demonstrate a significant impact of IFN and SSRI intake on platelet serotonin levels, suggesting a biochemical analogy between 5-HT metabolism in blood platelets and the CNS. Platelet 5-HT levels might serve as a surrogate marker for patient adherence to antiviral and anti-depressant medication. For the prediction of IFN-induced depression, however, platelet 5-HT measurements are not suitable.

Differential effects of PPARgamma activation by the oral antidiabetic agent pioglitazone in Barrett's carcinoma in vitro and in vivo.

BACKGROUND AND PURPOSE: The nuclear hormone receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a key transcription factor regulating genes involved in adipogenesis, glucose homeostasis and cell differentiation. Moreover, PPARgamma has been demonstrated to control proliferation and apoptosis in various cancer cells. We investigated the biological effects of PPARgamma activation by the oral antidiabetic agent pioglitazone in Barrett's adenocarcinoma cells in vitro and in vivo. RESULTS: PPARgamma mRNA and protein were overexpressed in endoscopic biopsies of Barrett's epithelium and the human Barrett's adenocarcinoma cancer cell line OE33 as compared to normal esophagus and stomach and the esophageal squamous epithelium cancer cell line Kyse-180. PPARgamma activation by pioglitazone in OE33 cells in vitro led to reduced cell growth by induction of apoptosis. Effects of systemic PPARgamma activation by the thiazolidinedione pioglitazone on tumor cell proliferation and apoptosis were then assessed in vivo in nude mice bearing transplantable Barrett's adenocarcinomas derived from OE33 cells. Unexpectedly, enhanced growth of OE33 derived transplantable adenocarcinomas was observed in Balb/c nu/nu mice upon systemic pioglitazone treatment due to increased cell proliferation. CONCLUSION: These results indicate that PPARgamma is involved in the molecular pathogenesis of Barrett's adenocarcinoma formation and growth. However, activation of PPARgamma exerts differential effects on growth of Barrett's adenocarcinoma cells in vitro and in vivo emphasizing the importance of additional cell context specific factors and systemic metabolic status for the modulation of PPARgamma action in vivo.