Abstract 3076: BVES, a novel adhesion molecule, acts as tumor modifier through modulation of tight-junction-associated signaling

BVES is novel adhesion protein that functions as a modulator of tight junction (TJ) formation with TJs level directly correlating with BVES expression. TJs, in addition to regulating paracellular passage of molecules, can also directly regulate Rho activity and transcriptional activation of cell cycle regulatory genes (ERBB2, PCNA, CDK4, and Cyclin-D1). Hence, alteration in BVES expression also modulates TJ associated signaling. Interestingly, overexpressing a dominant negative BVES induced human corneal epithelial cells to exhibit increased mesenchymal characteristics. Together, these observations led us to hypothesize that increasing BVES expression in carcinoma cells would induce an epithelial-like phenotype. To evaluate the function of BVES in carcinoma, a semi-adherent LIM2405 human colorectal cancer cell line was stably transfected with wild type BVES (WT-LIM2405) or empty vector (V-LIM2405) as control. Multiple stably transfected clonal isolates of LIM2405 overexpressing BVES exhibited increased epithelial features as evidenced by: i) uniform monolayer formation, ii) decreased vimentin and increased cytokeratin, Zo-1, and occludin expression, iii) decreased cellular motility (66% reduction, p<0.001), and iv) decreased colony number in soft-agar assays (53.5%, p<0.01). In addition, WT-LIM2405 cells progressively displayed reduced cellular proliferation, prolonged cell-doubling time (35%), and decreased S-phase and increased G1 fractions. This was more apparent with increasing confluence, suggesting that contact inhibition is restored with BVES expression. To evaluate the affect of BVES on tumor growth in vivo, V-LIM2405 and WT-LIM2405 cells were grown as orthotopic xenografts in athymic mice. WT-LIM2405 tumor growth was significantly attenuated (86%, p<0.001). Intra-tumoral proliferation rates were equivalent, however apoptosis was increased in WT-LIM2405 tumors (TUNEL positive cells/HPF, p=0.04). We next surveyed BVES expression in colorectal carcinoma. 80% of human CRCs samples exhibited at least a 40% reduction in BVES protein by immunoblotting. In addition, immunolocalization studies showed disorganized or absent BVES and ZO-1 staining only in carcinomatous regions. BVES expression is decrease not only in colorectal cancer (p=0.004), but also in breast (p=0.018) and thyroid carcinoma (p=0.20). Global expression analysis of 250 staged CRC samples compared with normal and adenoma colon specimens showed a decrease in BVES expression as early as carcinoma in situ (p<0.05). These findings indicate endogenous BVES expression is decrease in carcinoma and restoration of its’ expression induces an epithelial-like phenotype in colorectal cancer cells, thus implicating BVES as a tumor suppressor. Further investigation to determine the role of BVES in epithelial cancer biology is warranted and may lead to novel insight into targeted therapies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3076.

Diagnostic utility of IgG and IgM immunohistochemistry in autoimmune liver disease

AIM: To assess the role of IgM and IgG immunohistochemistry (IHC) in the evaluation of autoimmune liver conditions - autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC).

METHODS: Forty one biopsies from untreated patients diagnosed with autoimmune liver disease (AIH, n = 20; PBC, n = 13; PSC, n = 8) and fourteen biopsies of patients with chronic hepatitis C were selected. IgM and IgG-positive plasma cells were counted in each sample.

RESULTS: A predominance of IgG-positive plasma cells was seen in AIH (90% of cases), PSC (75% of cases), and chronic hepatitis C (100% of cases), while IgM-positive plasma cells predominated in PBC (92.8% of cases). The IgM /IgG ratio (< 1 or ≥ 1) accurately distinguished PBC from AIH in 90.9% of cases (sensitivity = 92.3%, specificity = 90%), and PBC from either AIH or PSC in 87.8% of cases (sensitivity = 92.3%, specificity = 85.7%).

CONCLUSION: Plasmacytic infiltrates expressing predominantly IgM are characteristic of PBC, while other forms of liver disease analyzed in this study, including AIH, typically show an IgG-predominant plasma cell infiltrate. Our data indicate that IgM and IgG IHC may be a useful tool when PBC is a diagnostic consideration.

Abstract B49: Smad4 suppresses Wnt signaling through downregulation of β-catenin

Introduction: Transforming Growth Factorβ (TGFβ) and Wnt signaling pathways modulate differential responses during embryonic development, and later in intestinal epithelial cell differentiation, proliferation and colorectal tumor promotion. β-catenin, the central mediator of canonical Wnt signaling, has been shown to pathologically promote intestinal epithelial cell de-differentiation and induce sustained proliferation in the absence of functional APC. Smad proteins are key developmental proteins involved in TGFβ/Bone Morphogenetic Protein (BMP) signaling involved in epithelial cell growth inhibition. Smad4, in particular, functions as a tumor suppressor and mutation of the Smad4 gene is a frequent and potentially late event in colon cancer. We recently found that expression of wild type Smad4 in Smad4-mutant colon cancer cells results in profound inhibition of β-catenin/TCF-driven transcriptional activation.

Purpose: In the current study, we set out to determine the mechanism of Smad4 inhibition of canonical Wnt signaling.

Experimental Procedures: We examined steady-state levels of β-catenin mRNA and protein in cells and human tissues, followed by analysis of components of β-catenin transcriptional and degradation machinery in the presence and absence of Smad4, and with and without inhibition of GSK3-β, a critical regulator of cytoplasmic β-catenin.

Results: We observed that wild type Smad4 expression resulted in significant repression of Wnt-specific transcriptional activity that could be restored with GSK-3β inhibition and overexpression of wild-type and mutant β-catenin in S W480 cells that have inactivating mutations in both APC and Smad4 genes. Transient overexpression of Smad4 also inhibited β-catenin-dependent transcriptional activity in HEK 293 cells that have wild-type APC and Smad4 genes. β-catenin phosphorylation is intact and unchanged in comparison of controls and Smad4-expressing S W480 cells, but the total level of β-catenin mRNA and protein is decreased in the Smad4-expressing cells. Assessment of human colorectal cancers using tissue microarray analysis revealed an inverse relationship between nuclear Smad4 and tumor cell β-catenin immunostaining. Furthermore, we observed that high Smad4 expression is associated with better disease-free survival and that high β-catenin expression is associated with worse disease-specific survival in analysis of outcomes from 250 patients.

Conclusions: Our data suggest that the tumor suppressor role of Smad4 involves reduction of β-catenin levels with resultant reduction of β-catenin/TCF-mediated transcriptional activity, and this regulatory mechanism has an important impact on clinical outcomes in colorectal cancer.

Citation Information: Cancer Res 2009;69(23 Suppl):B49.

Autoimmune pancreatitis results from loss of TGFbeta signalling in S100A4-positive dendritic cells

BACKGROUND AND AIMS

Autoimmune pancreatitis (AIP) is a poorly understood human disease affecting the exocrine pancreas. The goal of the present study was to elucidate the pathogenic mechanisms underlying pancreatic autoimmunity in a murine disease model.

METHODS

A transgenic mouse with an S100A4/fibroblast-specific protein 1 (FSP1) Cre-mediated conditional knockout of the transforming growth factor beta (TGFbeta) type II receptor, termed Tgfbr2(fspKO), was used to determine the direct role of TGFbeta in S100A4(+) cells. Immunohistochemical studies suggested that Tgfbr2(fspKO) mice develop mouse AIP (mAIP) characterised by interlobular ductal inflammatory infiltrates and pancreatic autoantibody production. Fluorescence-activated cell sorting (FACS)-isolated dendritic cells (DCs) from diseased pancreata were verified to have S100A4-Cre-mediated DNA recombination.

RESULTS

The Tgfbr2(fspKO) mice spontaneously developed mAIP by 6 weeks of age. DCs were confirmed to express S100A4, a previously reported protein expressed by fibroblasts. Adoptive transfer of bone marrow-derived DCs from Tgfbr2(fspKO) mice into 2-week-old syngenic wild-type C57BL/6 mice resulted in reproduction of pancreatitis within 6 weeks. Similar adoptive transfer of wild-type DCs had no effect on pancreas pathology of the host mice. The inability to induce pancreatitis by adoptive transfer of Tgfbr2(fspKO) DCs in adult mice suggested a developmental event in mAIP pathogenesis. Tgfbr2(fspKO) DCs undergo elevated maturation in response to antigen and increased activation of naïve CD4-positive T cells.

CONCLUSION

The development of mAIP in the Tgfbr2(fspKO) mouse model illustrates the role of TGFbeta in maintaining myeloid DC immune tolerance. The loss of immune tolerance in myeloid S100A4(+) DCs can mediate mAIP and may explain some aspects of AIP disease pathogenesis.

Long-lived Min mice develop advanced intestinal cancers through a genetically conservative pathway

C57BL/6J mice carrying the Min allele of Adenomatous polyposis coli (Apc) develop numerous adenomas along the entire length of the intestine and consequently die at an early age. This short lifespan would prevent the accumulation of somatic genetic mutations or epigenetic alterations necessary for tumor progression. To overcome this limitation, we generated F(1) Apc(Min/+) hybrids by crossing C57BR/cdcJ and SWR/J females to C57BL/6J Apc(Min/+) males. These hybrids developed few intestinal tumors and often lived longer than 1 year. Many of the tumors (24-87%) were invasive adenocarcinomas, in which neoplastic tissue penetrated through the muscle wall into the mesentery. In a few cases (3%), lesions metastasized by extension to regional lymph nodes. The development of these familial cancers does not require chromosomal gains or losses, a high level of microsatellite instability, or the presence of Helicobacter. To test whether genetic instability might accelerate tumor progression, we generated Apc(Min/+) mice homozygous for the hypomorphic allele of the Nijmegen breakage syndrome gene (Nbs1(DeltaB)) and also treated Apc(Min/+) mice with a strong somatic mutagen. These imposed genetic instabilities did not reduce the time required for cancers to form nor increase the percentage of cancers nor drive progression to the point of distant metastasis. In summary, we have found that the Apc(Min/+) mouse model for familial intestinal cancer can develop frequent invasive cancers in the absence of overt genomic instability. Possible factors that promote invasion include age-dependent epigenetic changes, conservative somatic recombination, or direct effects of alleles in the F(1) hybrid genetic background.

High fat diet induced hepatic steatosis establishes a permissive microenvironment for colorectal metastases and promotes primary dysplasia in a murine model

Non-alcoholic fatty liver disease (NAFLD), which includes steatosis and its progression to non-alcoholic steatohepatitis, is a liver disorder of increasing clinical significance. Here we characterize a murine model of high fat diet-induced NAFLD with progression from liver steatosis to histological features compatible with steatohepatitis and more advanced stages of NAFLD in humans, including chronic portal inflammation, pericellular and bridging fibrosis, Mallory body formation, and bile ductular reaction. Chronic changes induced by the prolonged consumption of a high-fat diet alone culminate in the development of primary liver dysplasias. Importantly, we extend these studies to demonstrate that even the early stages of uncomplicated steatosis provide a permissive microenvironment for the growth of colon cancer cells that are metastatic to the liver. High fat diet-induced steatosis, coupled with a splenic injection model of experimental liver metastasis using syngeneic MC38 colon cancer cells, resulted in an increased number of secondary tumor nodules and metastatic burden in steatotic livers. Metastatic nodules were associated with focal peritumoral areas of infiltrating inflammatory cells and associated apoptotic cell populations. These results suggest that the modulation of specific host factors in the steatotic liver contributes to tumor progression in the microenvironment of NAFLD.

Equivalence of protein inventories obtained from formalin-fixed paraffin-embedded and frozen tissue in multidimensional liquid chromatography-tandem mass spectrometry shotgun proteomic analysis

Formalin-fixed paraffin-embedded (FFPE) tissue specimens comprise a potentially valuable resource for retrospective biomarker discovery studies, and recent work indicates the feasibility of using shotgun proteomics to characterize FFPE tissue proteins. A critical question in the field is whether proteomes characterized in FFPE specimens are equivalent to proteomes in corresponding fresh or frozen tissue specimens. Here we compared shotgun proteomic analyses of frozen and FFPE specimens prepared from the same colon adenoma tissues. Following deparaffinization, rehydration, and tryptic digestion under mild conditions, FFPE specimens corresponding to 200 microg of protein yielded approximately 400 confident protein identifications in a one-dimensional reverse phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The major difference between frozen and FFPE proteomes was a decrease in the proportions of lysine C-terminal to arginine C-terminal peptides observed, but these differences had little effect on the proteins identified. No covalent peptide modifications attributable to formaldehyde chemistry were detected by analyses of the MS/MS datasets, which suggests that undetected, cross-linked peptides comprise the major class of modifications in FFPE tissues. Fixation of tissue for up to 2 days in neutral buffered formalin did not adversely impact protein identifications. Analysis of archival colon adenoma FFPE specimens indicated equivalent numbers of MS/MS spectral counts and protein group identifications from specimens stored for 1, 3, 5, and 10 years. Combination of peptide isoelectric focusing-based separation with reverse phase LC-MS/MS identified 2554 protein groups in 600 ng of protein from frozen tissue and 2302 protein groups from FFPE tissue with at least two distinct peptide identifications per protein. Analysis of the combined frozen and FFPE data showed a 92% overlap in the protein groups identified. Comparison of gene ontology categories of identified proteins revealed no bias in protein identification based on subcellular localization. Although the status of posttranslational modifications was not examined in this study, archival samples displayed a modest increase in methionine oxidation, from approximately 17% after one year of storage to approximately 25% after 10 years. These data demonstrate the equivalence of proteome inventories obtained from FFPE and frozen tissue specimens and provide support for retrospective proteomic analysis of FFPE tissues for biomarker discovery.

Tenofovir disoproxil fumarate versus adefovir dipivoxil for chronic hepatitis B

BACKGROUND

Tenofovir disoproxil fumarate (DF) is a nucleotide analogue and a potent inhibitor of human immunodeficiency virus type 1 reverse transcriptase and hepatitis B virus (HBV) polymerase.

METHODS

In two double-blind, phase 3 studies, we randomly assigned patients with hepatitis B e antigen (HBeAg)-negative or HBeAg-positive chronic HBV infection to receive tenofovir DF or adefovir dipivoxil (ratio, 2:1) once daily for 48 weeks. The primary efficacy end point was a plasma HBV DNA level of less than 400 copies per milliliter (69 IU per milliliter) and histologic improvement (i.e., a reduction in the Knodell necroinflammation score of 2 or more points without worsening fibrosis) at week 48. Secondary end points included viral suppression (i.e., an HBV DNA level of <400 copies per milliliter), histologic improvement, serologic response, normalization of alanine aminotransferase levels, and development of resistance mutations.

RESULTS

At week 48, in both studies, a significantly higher proportion of patients receiving tenofovir DF than of those receiving adefovir dipivoxil had reached the primary end point (P<0.001). Viral suppression occurred in more HBeAg-negative patients receiving tenofovir DF than patients receiving adefovir dipivoxil (93% vs. 63%, P<0.001) and in more HBeAg-positive patients receiving tenofovir DF than patients receiving adefovir dipivoxil (76% vs. 13%, P<0.001). Significantly more HBeAg-positive patients treated with tenofovir DF than those treated with adefovir dipivoxil had normalized alanine aminotransferase levels (68% vs. 54%, P=0.03) and loss of hepatitis B surface antigen (3% vs. 0%, P=0.02). At week 48, amino acid substitutions within HBV DNA polymerase associated with phenotypic resistance to tenofovir DF or other drugs to treat HBV infection had not developed in any of the patients. Tenofovir DF produced a similar HBV DNA response in patients who had previously received lamivudine and in those who had not. The safety profile was similar for the two treatments in both studies.

CONCLUSIONS

Among patients with chronic HBV infection, tenofovir DF at a daily dose of 300 mg had superior antiviral efficacy with a similar safety profile as compared with adefovir dipivoxil at a daily dose of 10 mg through week 48. (ClinicalTrials.gov numbers, NCT00116805 and NCT00117676.)

Organic anion transporting polypeptide 1B3 (OATP1B3) is overexpressed in colorectal tumors and is a predictor of clinical outcome

BACKGROUND AND AIMS

OATP1B3 is an organic anion transporting polypeptide (OATP) that functions as a multispecific transporter in the normal liver. We examined the expression and clinical significance of OATP1B3 in colon cancers in tissue microarrays.

METHODS

Immunohistochemistry was used to assess OATP1B3 protein expression in paraffinized colon tumor tissue microarrays. OATP1B3 immunostaining was evaluated by location and intensity. Relationships between OATP1B3 expression, known prognostic variables and clinical outcomes were examined.

RESULTS

278 colon tumor samples of all stages were evaluated for OATP1B3 expression. OATP1B3 immunostaining was detectable in the majority (56%) of the tumor samples. Higher OATP1B3 expression was seen in lower stage tumors (p = 0.003) and lower grade (p = 0.004) tumors, but was not predictive of 5-year survival or tumor recurrence as an independent variable. Within individual tumor grades, OATP1B3 expression was associated with improved 5-year survival, but not recurrence in patients with poorly differentiated tumors.

CONCLUSION

OATP1B3 expression was seen in the majority of colon tumors and may be a marker of lower grade and lower stage tumors and may predict for improved outcome in certain tumors.