Gastric cancer, version 2.2013: featured updates to the NCCN Guidelines

The NCCN Clinical Practice Guidelines in Oncology for Gastric Cancer provide evidence- and consensus-based recommendations for a multidisciplinary approach for the management of patients with gastric cancer. For patients with resectable locoregional cancer, the guidelines recommend gastrectomy with a D1+ or a modified D2 lymph node dissection (performed by experienced surgeons in high-volume centers). Postoperative chemoradiation is the preferred option after complete gastric resection for patients with T3-T4 tumors and node-positive T1-T2 tumors. Postoperative chemotherapy is included as an option after a modified D2 lymph node dissection for this group of patients. Trastuzumab with chemotherapy is recommended as first-line therapy for patients with HER2-positive advanced or metastatic cancer, confirmed by immunohistochemistry and, if needed, by fluorescence in situ hybridization for IHC 2+.

Endoscopic mucosal resection of Barrett’s esophagus detects high prevalence of subsquamous intestinal metaplasia

AIM: To report the prevalence of Subsquamous intestinal metaplasia (SSIM) in patients undergoing endoscopic mucosal resection (EMR) for staging of Barrett’s esophagus (BE).

METHODS: Thirty-three patients with BE associated neoplasia underwent EMR at our institution between September 2009 and September 2011; 22 of these patients met study inclusion criteria. EMR was targeted at focal abnormalities within the BE segment. EMR was performed in standardized fashion using a cap-assisted band ligation technique, and resection specimens were assessed for the presence of SSIM. Demographic and clinical data were analyzed to determine predictors of SSIM.

RESULTS: SSIM was detected in 59% of patients. SSIM was detected in 73% of patients with short segment (< 3 cm) BE, and in 45% of patients with long-segment (≥ 3 cm) BE (P = NS). There was no association between presence/absence of SSIM and age, gender, or stage of BE-associated neoplasia.

CONCLUSION: EMR detects SSIM in a majority of patients with BE-associated neoplasia. While the long-term clinical significance of SSIM remains uncertain, these results highlight the importance of EMR as an optimal diagnostic tool for staging of BE and detection of SSIM, and should further limit concerns that SSIM is purely a post-ablation phenomenon.

MTG16 contributes to colonic epithelial integrity in experimental colitis

OBJECTIVE

The myeloid translocation genes (MTGs) are transcriptional corepressors with both Mtg8(-/-) and Mtgr1(-/-) mice showing developmental and/or differentiation defects in the intestine. We sought to determine the role of MTG16 in intestinal integrity.

METHODS

Baseline and stress induced colonic phenotypes were examined in Mtg16(-/-) mice. To unmask phenotypes, we treated Mtg16(-/-) mice with dextran sodium sulphate (DSS) or infected them with Citrobacter rodentium and the colons were examined for ulceration and for changes in proliferation, apoptosis and inflammation.

RESULTS

Mtg16(-/-) mice have altered immune subsets, suggesting priming towards Th1 responses. Mtg16(-/-) mice developed increased weight loss, diarrhoea, mortality and histological colitis and there were increased innate (Gr1(+), F4/80(+), CD11c(+) and MHCII(+); CD11c(+)) and Th1 adaptive (CD4) immune cells in Mtg16(-/-) colons after DSS treatment. Additionally, there was increased apoptosis and a compensatory increased proliferation in Mtg16(-/-) colons. Compared with wild-type mice, Mtg16(-/-) mice exhibited increased colonic CD4;IFN-γ cells in vehicle-treated and DSS-treated mice. Adoptive transfer of wild-type marrow into Mtg16(-/-) recipients did not rescue the Mtg16(-/-) injury phenotype. Isolated colonic epithelial cells from DSS-treated Mtg16(-/-) mice exhibited increased KC (Cxcl1) mRNA expression when compared with wild-type mice. Mtg16(-/-) mice infected with C rodentium had more severe colitis and greater bacterial colonisation. Last, MTG16 mRNA levels were reduced in human ulcerative colitis versus normal colon tissues.

CONCLUSIONS

These observations indicate that MTG16 is critical for colonocyte survival and regeneration in response to intestinal injury and provide evidence that this transcriptional corepressor regulates inflammatory recruitment in response to injury.

Malignant transformation of colonic epithelial cells by a colon-derived long noncoding RNA

Recent progress has been made in the identification of protein-coding genes and miRNAs that are expressed in and alter the behavior of colonic epithelia. However, the role of long non-coding RNAs (lncRNAs) in colonic homeostasis is just beginning to be explored. By gene expression profiling of post-mitotic, differentiated tops and proliferative, progenitor-compartment bottoms of microdissected adult mouse colonic crypts, we identified several lncRNAs more highly expressed in crypt bottoms. One identified lncRNA, designated non-coding Nras functional RNA (ncNRFR), resides within the Nras locus but appears to be independent of the Nras coding transcript. Stable overexpression of ncNRFR in non-transformed, conditionally immortalized mouse colonocytes results in malignant transformation, as determined by growth in soft agar and formation of highly invasive tumors in nude mice. Moreover, ncNRFR appears to inhibit the function of the tumor suppressor let-7. These results suggest precise regulation of ncNRFR is necessary for proper cell growth in the colonic crypt, and its misregulation results in neoplastic transformation.

Proinflammatory cytokines and bile acids upregulate ΔNp73 protein, an inhibitor of p53 and p73 tumor suppressors

Gastroesophageal reflux disease (GERD) is the main etiological factor behind the recent rapid increase in the incidence of esophageal adenocarcinoma. During reflux, esophageal cells are exposed to bile at low pH resulting in cellular damage and inflammation, which are known to facilitate cancer development. In this study, we investigated the regulation of p73 isoform, ΔNp73α, in the reflux condition. Previous studies have reported that ΔNp73 exhibits anti-apoptotic and oncogenic properties through inhibition of p53 and p73 proteins. We found that direct exposure of esophageal cells to bile acids in an acidic environment alters the phosphorylation of ΔNp73, its subcellular localization and increases ΔNp73 protein levels. Upregulation of ΔNp73 was also observed in esophageal tissues collected from patients with GERD and Barrett’s metaplasia, a precancerous lesion in the esophagus associated with gastric reflux. c-Abl, p38 MAPK, and IKK protein kinases were identified to interact in the regulation of ΔNp73. Their inhibition with chemotherapeutic agents and siRNA suppresses ΔNp73. We also found that pro-inflammatory cytokines, IL-1β and TNFα, are potent inducers of ΔNp73α, which further enhance the bile acids/acid effect. Combined, our studies provide evidence that gastroesophageal reflux alters the regulation of oncogenic ΔNp73 isoform that may facilitate tumorigenic transformation of esophageal metaplastic epithelium.

Colorectal cancer gene expression profiling using nanostring nCounter analysis

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Background: A more accurate method of identifying stage 2 and 3 colorectal cancer (CRC) patients at highest risk for recurrence after surgical resection is needed. Gene expression signatures utilizing microarray-derived gene expression data from fresh frozen primary CRCs to predict risk of recurrence have been developed by us and others. Advances in technology platforms for gene expression measurements and their applicability to formalin-fixed, paraffin-embedded (FFPE) specimens offer new opportunity to develop clinically useful diagnostics based on molecular profiles. Methods: 58 patient FFPE samples of all stages stored from 1-12 years were collected from the Vanderbilt GI SPORE Translational Pathology and Imaging Core and annotated with appropriate clinicopathologic data. 414 genes were selected from our 34-gene prognostic classifier and other published CRC gene signatures, as well as gene elements associated with intestinal stem cell biology and epithelial-to-mesenchymal transition (EMT). RNA was extracted from the tumors, and gene expression analysis was completed using the nCounterplatform. Results: Quality of extracted RNA from tumor blocks was similar among the tumors and adequate for analysis. No significant differences were seen in signal strength (p=0.94, Kruskal-Wallis test) or intra-class variation (correlation coefficient = 0.99) across material extracted from new and old blocks. Fold change values for the 70 most highly differentially expressed genes on the nCounter platform correlated well with Affymetrix U133 plus 2 microarray (R2=0.819). Genes associated with EMT clustered according to prognosis, with poorer prognoses seen in patients with high TWIST expression or low E-cadherin and SMAD4 expression. There was a trend toward better survival outcomes with high expression of E-cadherin and SMAD4 (p=0.072, log-rank test). Conclusions: This preliminary study demonstrates the feasibility of this approach to determine gene expression patterns in FFPE tumor tissue samples. Our data suggest that this approach may be applied to identify clinically applicable prognostic gene expression profiles that may be validated in archived patient samples that are well annotated with patient outcome data.

mTOR inhibition elicits a dramatic response in PI3K-dependent colon cancers

The phosphatidylinositide-3-kinase (PI3K) signaling pathway is critical for multiple cellular functions including metabolism, proliferation, angiogenesis, and apoptosis, and is the most commonly altered pathway in human cancers. Recently, we developed a novel mouse model of colon cancer in which tumors are initiated by a dominant active PI3K (FC PIK3ca*). The cancers in these mice are moderately differentiated invasive mucinous adenocarcinomas of the proximal colon that develop by 50 days of age. Interestingly, these cancers form without a benign intermediary or aberrant WNT signaling, indicating a non-canonical mechanism of tumorigenesis. Since these tumors are dependent upon the PI3K pathway, we investigated the potential for tumor response by the targeting of this pathway with rapamycin, an mTOR inhibitor. A cohort of FC PIK3ca* mice were treated with rapamycin at a dose of 6 mg/kg/day or placebo for 14 days. FDG dual hybrid PET/CT imaging demonstrated a dramatic tumor response in the rapamycin arm and this was confirmed on necropsy. The tumor tissue remaining after treatment with rapamycin demonstrated increased pERK1/2 or persistent phosphorylated ribosomal protein S6 (pS6), indicating potential resistance mechanisms. This unique model will further our understanding of human disease and facilitate the development of therapeutics through pharmacologic screening and biomarker identification.

Pathology of rodent models of intestinal cancer: progress report and recommendations

In October 2010, a pathology review of rodent models of intestinal neoplasia was held at The Jackson Laboratory. This review complemented 2 other concurrent events: a workshop on methods of modeling colon cancer in rodents and a conference on current issues in murine and human colon cancer. We summarize the results of the pathology review and the committee's recommendations for tumor nomenclature. A virtual high-resolution image slide box of these models has been developed. This report discusses significant recent developments in rodent modeling of intestinal neoplasia, including the role of stem cells in cancer and the creation of models of metastatic intestinal cancer.

53BP1 expression is a modifier of the prognostic value of lymph node ratio and CA 19-9 in pancreatic adenocarcinoma

BACKGROUND

53BP1 binds to the tumor suppressor p53 and has a key role in DNA damage response and repair. Low 53BP1 expression has been associated with decreased survival in breast cancer and has been shown to interact with several prognostic factors in non-small cell lung cancer. The role of 53BP1 in pancreatic ductal adenocarcinoma (PDAC) has yet to be determined. We aimed to investigate whether 53BP1 levels interact with established prognostic factors in PDAC.

METHODS

106 patients for whom there was tissue available at time of surgical resection for PDAC were included. A tissue microarray was constructed using surgical specimens, stained with antibodies to 53BP1, and scored for expression intensity. Univariate and multivariate statistical analyses were performed to investigate the association between 53BP1 and patient survival with known prognostic factors for survival.

RESULTS

The association of 53BP1 with several established prognostic factors was examined, including stage, tumor grade, surgical margin, peripancreatic extension, lymph node ratio (LNR), and CA 19-9. We found that 53BP1 modified the effects of known prognostic variables including LNR and CA 19-9 on survival outcomes. When 53BP1 intensity was low, increased LNR was associated with decreased OS (HR 4.84, 95% CI (2.26, 10.37), p<0.001) and high CA19-9 was associated with decreased OS (HR 1.72, 95% CI (1.18, 2.51), p=0.005). When 53BP1 intensity was high, LNR and CA19-9 were no longer associated with OS (p=0.958 and p=0.606, respectively).

CONCLUSIONS

In this study, 53BP1, a key player in DNA damage response and repair, was found to modify the prognostic value of two established prognostic factors, LNR and CA 19-9, suggesting 53BP1 may alter tumor behavior and ultimately impact how we interpret the value of other prognostic factors.

Limits of [18F]-FLT PET as a biomarker of proliferation in oncology

Background

Non-invasive imaging biomarkers of cellular proliferation hold great promise for quantifying response to personalized medicine in oncology. An emerging approach to assess tumor proliferation utilizes the positron emission tomography (PET) tracer 3’-deoxy-3’[¹⁸F]-fluorothymidine, [¹⁸F]-FLT. Though several studies have associated serial changes in [¹⁸F]-FLT-PET with elements of therapeutic response, the degree to which [¹⁸F]-FLT-PET quantitatively reflects proliferative index has been continuously debated for more that a decade. The goal of this study was to elucidate quantitative relationships between [¹⁸F]-FLT-PET and cellular metrics of proliferation in treatment naïve human cell line xenografts commonly employed in cancer research.

Methods and Findings

[¹⁸F]-FLT-PET was conducted in human cancer xenograft-bearing mice. Quantitative relationships between PET, thymidine kinase 1 (TK1) protein levels and immunostaining for proliferation markers (Ki67, TK1, PCNA) were evaluated using imaging-matched tumor specimens. Overall, we determined that [¹⁸F]-FLT-PET reflects TK1 protein levels, yet the cell cycle specificity of TK1 expression and the extent to which tumors utilize thymidine salvage for DNA synthesis decouple [¹⁸F]-FLT-PET data from standard estimates of proliferative index.

Conclusions

Our findings illustrate that [¹⁸F]-FLT-PET reflects tumor proliferation as a function of thymidine salvage pathway utilization. Unlike more general proliferation markers, such as Ki67, [¹⁸F]-FLT PET reflects proliferative indices to variable and potentially unreliable extents. [¹⁸F]-FLT-PET cannot discriminate moderately proliferative, thymidine salvage-driven tumors from those of high proliferative index that rely primarily upon de novo thymidine synthesis. Accordingly, the magnitude of [¹⁸F]-FLT uptake should not be considered a surrogate of proliferative index. These data rationalize the diversity of [¹⁸F]-FLT-PET correlative results previously reported and suggest future best-practices when [¹⁸F]-FLT-PET is employed in oncology.

Regression of cirrhosis during treatment with tenofovir disoproxil fumarate for chronic hepatitis B: a 5-year open-label follow-up study

BACKGROUND

Whether long-term suppression of replication of hepatitis B virus (HBV) has any beneficial effect on regression of advanced liver fibrosis associated with chronic HBV infection remains unclear. We aimed to assess the effects on fibrosis and cirrhosis of at least 5 years' treatment with tenofovir disoproxil fumarate (DF) in chronic HBV infection.

METHODS

After 48 weeks of randomised double-blind comparison (trials NCT00117676 and NCT00116805) of tenofovir DF with adefovir dipivoxil, participants (positive or negative for HBeAg) were eligible to enter a 7-year study of open-label tenofovir DF treatment, with a pre-specified repeat liver biopsy at week 240. We assessed histological improvement (≥2 point reduction in Knodell necroinflammatory score with no worsening of fibrosis) and regression of fibrosis (≥1 unit decrease by Ishak scoring system).

FINDINGS

Of 641 patients who received randomised treatment, 585 (91%) entered the open-label phase, and 489 (76%) completed 240 weeks. 348 patients (54%) had biopsy results at both baseline and week 240. 304 (87%) of the 348 had histological improvement, and 176 (51%) had regression of fibrosis at week 240 (p<0·0001). Of the 96 (28%) patients with cirrhosis (Ishak score 5 or 6) at baseline, 71 (74%) no longer had cirrhosis (≥1 unit decrease in score), whereas three of 252 patients without cirrhosis at baseline progressed to cirrhosis at year 5 (p<0·0001). Virological breakthrough occurred infrequently and was not due to resistance to tenofovir DF. The safety profile was favourable: 91 (16%) patients had adverse events but only nine patients had serious events related to the study drug.

INTERPRETATION

In patients with chronic HBV infection, up to 5 years of treatment with tenofovir DF was safe and effective. Long-term suppression of HBV can lead to regression of fibrosis and cirrhosis.

FUNDING

Gilead Sciences.

Correlation of elevated ALCAM shedding with patient outcome in colorectal cancer

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Background: ALCAM (Activated Leukocyte Cell Adhesion Molecule) is a cell-cell adhesion protein that has been highlighted as a putative biomarker for the progression of many cancers, including colorectal cancer (CRC). Current prognosis for CRC patients predominantly rely on pathologic staging classification. Although TNM staging successfully stratifies high-risk patients, there is significant variability in the rate of disease progression within each stage. Previous studies evaluating ALCAM as a biomarker for predicting colorectal cancer patient survival have published conflicting and inconclusive results. The aim of this present study was to investigate the prognostic value of ALCAM shedding, quantified using a dual stain that detects both the extracellular and the intracellular domains in formalin-fixed tissue, in colorectal patients. Methods: A novel dual-immunohistological detection of ALCAM shedding was performed on tissue microarrays constructed from 75 colorectal primary tumors and 9 healthy control specimens. Tissue was assessed by CellProfiler image analysis to obtain quantitative estimates of ALCAM shedding, defined as the detection of the intracellular domain the absence of the extracellular domain of ALCAM. Two tailed p values ≤ 0.05 were considered to be statistically significant. Results: ALCAM shedding was elevated in 33/79 (41.8%) of tissue from CRC patients compared to healthy controls (p=0.0239). Univariate analysis of CRC patients, stages I-IV, revealed a statistical significance correlating high ALCAM shedding with worse overall survival (p=0.0401). Moreover, ALCAM shedding is a predictor of overall survival (p=0.432) and more notably, disease-specific survival in stage II patients (p=0.0098). Conclusions: Detection of ALCAM shedding allows for stratification of patients according to their risk for poor long-term outcome. Considering that ALCAM is altered in a number of malignancies, the clinical correlation of ALCAM shedding to patient outcome is likely to extend beyond CRC to other cancers.

[18F]FLT-PET to predict pharmacodynamic and clinical response to cetuximab therapy in Ménétrier's disease

Molecular imaging biomarkers of proliferation hold great promise for quantifying response to personalized medicine. One such approach utilizes the positron emission tomography (PET) tracer 3'-deoxy-3'[18F]-fluorothymidine ([18F]FLT), an investigational agent whose uptake reflects thymidine salvage-dependent DNA synthesis. The goal of this study was to evaluate [18F]FLT-PET in the setting of Ménétrier's disease (MD), a rare, premalignant hyperproliferative disorder of the stomach treatable with cetuximab therapy. Over 15 months, a patient with confirmed MD underwent cetuximab therapy and was followed with sequential [18F]FLT-PET. For comparison to MD, an [18F]FLT-PET study was conducted in another patient to quantify uptake in a normal stomach. Prior to cetuximab therapy, stomach tissue in MD was easily visualized with [18F]FLT-PET, with pre-treatment uptake levels exceeding normal stomach uptake by approximately fourfold. Diminished [18F]FLT-PET in MD was observed following the initial and subsequent doses of cetuximab and correlated with clinical resolution of the disease. To our knowledge, this study reports the first clinical use of [18F]FLT-PET to assess proliferation in a premalignant disorder. We illustrate that the extent of MD involvement throughout the stomach could be easily visualized using [18F]FLT-PET, and that response to cetuximab could be followed quantitatively and non-invasively in sequential [18F]FLT-PET studies. Thus, [18F]FLT-PET appears to have potential to monitor response to treatment in this and potentially other hyperproliferative disorders.

Precision of multiple reaction monitoring mass spectrometry analysis of formalin-fixed, paraffin-embedded tissue

We compared the reproducibility of multiple reaction monitoring (MRM) mass spectrometry-based peptide quantitation in tryptic digests from formalin-fixed, paraffin-embedded (FFPE) and frozen clear cell renal cell carcinoma tissues. The analyses targeted a candidate set of 114 peptides previously identified in shotgun proteomic analyses, of which 104 were detectable in FFPE and frozen tissue. Although signal intensities for MRM of peptides from FFPE tissue were on average 66% of those in frozen tissue, median coefficients of variation (CV) for measurements in FFPE and frozen tissues were nearly identical (18–20%). Measurements of lysine C-terminal peptides and arginine C-terminal peptides from FFPE tissue were similarly reproducible (19.5% and 18.3% median CV, respectively). We further evaluated the precision of MRM-based quantitation by analysis of peptides from the Her2 receptor in FFPE and frozen tissues from a Her2 overexpressing mouse xenograft model of breast cancer and in human FFPE breast cancer specimens. We obtained equivalent MRM measurements of HER2 receptor levels in FFPE and frozen mouse xenografts derived from HER2-overexpressing BT474 cells and HER2-negative Sum159 cells. MRM analyses of 5 HER2-positive and 5 HER-negative human FFPE breast tumors confirmed the results of immunohistochemical analyses, thus demonstrating the feasibility of HER2 protein quantification in FFPE tissue specimens. The data demonstrate that MRM analyses can be performed with equal precision on FFPE and frozen tissues and that lysine-containing peptides can be selected for quantitative comparisons, despite the greater impact of formalin fixation on lysine residues. The data further illustrate the feasibility of applying MRM to quantify clinically important tissue biomarkers in FFPE specimens.

Mice expressing activated PI3K rapidly develop advanced colon cancer

Aberrations in the phosphoinositide 3-kinase (PI3K) signaling pathway play a key role in the pathogenesis of numerous cancers by altering cellular growth, metabolism, proliferation, and apoptosis. Mutations in the catalytic domain of PI3K that generate a dominantly active kinase are commonly found in human colorectal cancers and have been thought to drive tumor progression but not initiation. However, the effects of constitutively activated PI3K upon the intestinal mucosa have not been previously studied in animal models. Here, we show that the expression of a dominantly active form of the PI3K protein in the mouse intestine results in hyperplasia and advanced neoplasia. Mice expressing constitutively active PI3K in the epithelial cells of the distal small bowel and colon rapidly developed invasive adenocarcinomas in the colon that spread into the mesentery and adjacent organs. The histologic characteristics of these tumors were strikingly similar to invasive mucinous colon cancers in humans. Interestingly, these tumors formed without a benign polypoid intermediary, consistent with the lack of aberrant WNT signaling observed. Together, our findings indicate a noncanonical mechanism of colon tumor initiation that is mediated through activation of PI3K. This unique model has the potential to further our understanding of human disease and facilitate the development of therapeutics through pharmacologic screening and biomarker identification.

Abstract 1334: Overexpression of claudin-1 induces Notch and Wnt signaling to regulate colon carcinogenesis

Under physiological conditions, colonic homeostasis is a carefully balanced interplay between stem cells, their progeny, differentiation and cell fate determination. Dysregulation of this harmony signifies susceptibility to neoplastic growth. Colonic epithelium undergoes continuous proliferation, differentiation, and apoptosis along the crypt (crypt bottom to top). Notch signaling is a key regulator of the absorptive/secretory lineage determination. Dysregulation of notch signaling disrupts the normal colonic differentiation and depletes the goblet cell population while immature colonocyte population increases. Importantly, emerging literature suggests that Notch- signaling helps regulate colon cancer growth and progression in association with Wnt signaling. We have previously demonstrated that claudin-1 expression is highly increased in colon cancer and is causally associated with the tumorigenic and metastatic abilities of colon cancer cells. We also reported an inverse relationship between claudin-1 expression and differentiation in colon cancer cells. Here, we show a significant decrease in the goblet cell population (as determined by PAS and Alcian Blue) and Muc-2 expression accompanied with an increase in Carbonic Anhydrase I (CAI) expression, a commonly used marker for colonocytes in Villin-claudin-1 transgenic (Cl-1TG) mice that overexpress claudin-1 in the intestinal epithelium. Further analysis to detect Ki-67 expression suggested increase in colonic proliferation in Cl-1TG mice vs. WT mice. Taken together, these data suggest a role for claudin-1 in the regulation of colonic epithelial differentiation. To further determine the role of claudin-1 overexpression in cancer progression, we crossed Cl-1TG mice with APCmin mice, most widely used mouse model of colon cancer. Notably, APCmin mice develop few colonic tumors (mean=0.8) and have a life span of ∼22.5-23 weeks. Importantly, we noted a ∼4fold increase in the colonic tumor burden in (mean=3.8 tumors) and decrease in life span in APCmin/Cl-1 mice vs. APCmin mice. Also, tumors in APCmin/Cl-1 mice were larger, exhibited high grade of dysplasia and increased nuclear β-catenin (activated Wnt signaling) compared to tumors from APCmin mice. Our further studies using SW480claudin-1 cells {SW480 cells stably overexpressing claudin-1} and SW620siRNA cells {SW620 cells with stable inhibition of claudin-1 expression} demonstrated activation of Notch and Wnt signaling in SW480 cells (APCmutant) overexpressing claudin-1 while inhibited on inhibition of claudin-1. Taken together, our data supported a novel role of claudin-1 in the regulation of Notch and Wnt-signaling and thus colon carcinogenesis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1334. doi:1538-7445.AM2012-1334

Abstract 1341: Mice expressing activated PI3K develop advanced colon cancer

Background: Mutations in PIK3CA are a common feature of human cancers and multiple new PI3K inhibitors are in clinical development. These mutations are present in 20-30% of colorectal cancers in humans; however, the effects of such mutations on the intestinal mucosa have not been previously studied in animal models. Here we demonstrate that the expression of a dominant active form of the PI3K protein in the mouse intestine results not only in hyperplasia but also advanced neoplasia. Methods: Mice carrying a transgene in which the fatty acid binding protein promoter is fused to Cre recombinase (FC) were crossed to mice carrying a transgene encoding a chimeric protein with the iSH2 domain of the p85 subunit fused to the N-terminus of p110 (PIK3ca*). Progeny carrying both transgenes (FC PIK3ca*) express this constitutively active form of p110 in epithelial cells of the distal small bowel and colon. Results: Invasive mucinous adenocarcinomas develop in the proximal colon by only 50 days of age. These tumors are very aggressive, spreading into the mesentery and adjacent organs, and their histological characteristics are strikingly similar to those of invasive colon cancers in humans. Neoplastic cells exhibit a high rate of cell proliferation as seen by increased Ki67 immunohistochemical staining and phosphorylation of AKT, pS6, and p4E-BP1 by western blot demonstrating downstream signaling of PI3K. Interestingly, these cells did not exhibit perturbations in ERK and WNT signaling. Consistent with the lack of aberrant WNT signaling, no benign polypoid intermediaries were identified. Together, the results indicate that tumors in this model form via a non-canonical mechanism. A cohort of FC PIK3ca* mice were imaged by FDG dual hybrid PET/CT colonography and mice with similar sized tumors were divided into control and experimental arms. The experimental arm was treated with rapamycin (6mg/kg/day) for 14 days. Both groups were re-imaged 14 days later. The full results of the rapamycin treatment will be presented. Conclusion: This unique model of advanced colonic invasive adenocarcinomas has the potential to further our understanding of human disease and facilitate the development of therapeutics, especially inhibitors targeting downstream of PI3K.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1341. doi:1538-7445.AM2012-1341

Variable expression of somatostatin receptor type 2 in metastatic midgut carcinoid

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Background: Somatostatin receptor type 2 (SSTR2) is frequently highly expressed in carcinoid tumors of the midgut. The presence of the receptor is the basis of imaging and therapeutics. Because of the high dependence of clinical care on SSTR2, we evaluated the immunohistochemical staining of specimens and correlated with clinical parameters.

Methods: A tissue microarray (TMA) of 1 mm cores from paraffin embedded specimens of surgically resected midgut carcinoid were created with primary, lymph node, and liver metastatic lesions. These sections were stained by immunohistochemistry with anti-SSTR2 antibody, and scored on staining intensity. Sections were evaluated by membrane (0-none, 1 – weak, 2 – partial, 3- complete) and cytoplasmic (strong vs. weak) staining.

Results: Thirty-five patient samples were included in the TMA. There were a total of 62 cores embedded: 21 primary lesions, 26 lymph node metastases, and 15 liver metastases. The total disease burden was captured in 17 patients, and specimens from all three sites were captured in 6 patients. Of the thirty-five patients, 6 had consistently weak SSTR2 staining (17% either 0 or 1). One of these cases had an intermediate grade tumor with Ki67 >20%. Of the patients where more than one location was captured, 19/21 (90%) had consistent SSTR2 staining at all sites. Most cases had strong staining in the membrane (69%) while a minority had strong cytoplasmic staining (31%). Of the patients with weak SSTR2 membrane staining, 2 still had positive octreoscans. Clinically, most patients had good outcomes and 94% are still alive. Eight cases had carcinoid carcinomatosis (23%). Of the six with weak membrane staining, three had carcinomatosis (50%), while only 5/30 (17%) with strong membrane staining had carcinomatosis.

Conclusions: While the majority of small bowel carcinoids and their metastatic lesions have strong SSTR2 staining, not all do. However, even in cases with low amounts of SSTR2 on the membrane, the tumors can still be detected on octreoscan, demonstrating the effect of receptor turnover. The loss of SSTR2 may be associated with more advanced disease, but is not completely predictive.

Location-specific epigenetic regulation of the metallothionein 3 gene in esophageal adenocarcinomas

Background

Metallothionein 3 (MT3) maintains intracellular metal homeostasis and protects against reactive oxygen species (ROS)-induced DNA damage. In this study, we investigated the epigenetic alterations and gene expression of the MT3 gene in esophageal adenocarcinomas (EACs).

Methods and Results

Using quantitative bisulfite pyrosequencing, we detected unique DNA methylation profiles in the MT3 promoter region. The CpG nucleotides from −372 to −306 from the transcription start site (TSS) were highly methylated in tumor (n = 64) and normal samples (n = 51), whereas CpG nucleotides closest to the TSS (−4 and +3) remained unmethylated in all normal and most tumor samples. Conversely, CpG nucleotides in two regions (from −139 to −49 and +296 to +344) were significantly hypermethylated in EACs as compared to normal samples [FDR<0.001, −log10(FDR)>3.0]. The DNA methylation levels from −127 to −8 CpG sites showed the strongest correlation with MT3 gene expression (r = −0.4, P<0.0001). Moreover, the DNA hypermethylation from −127 to −8 CpG sites significantly correlated with advanced tumor stages and lymph node metastasis (P = 0.005 and P = 0.0313, respectively). The ChIP analysis demonstrated a more repressive histone modification (H3K9me2) and less active histone modifications (H3K4me2, H3K9ace) in OE33 cells than in FLO-1 cells; concordant with the presence of higher DNA methylation levels and silencing of MT3 expression in OE33 as compared to FLO-1 cells. Treatment of OE33 cells with 5-Aza-deoxycitidine restored MT3 expression with demethylation of its promoter region and reversal of the histone modifications towards active histone marks.

Conclusion

In summary, EACs are characterized by frequent epigenetic silencing of MT3. The choice of specific regions in the CpG island is a critical step in determining the functional role and prognostic value of DNA methylation in cancer cells.

Dilated intercellular space in chronic laryngitis and gastro-oesophageal reflux disease: at baseline and post-lansoprazole therapy

BACKGROUND

Dilation of intercellular spaces is reported to be an early morphological marker in gastro-oesophageal reflux. It remains unknown if this marker is useful in diagnosing reflux-related chronic laryngitis.

AIM

To determine histopathology and electron microscopic changes in oesophageal and laryngeal epithelium in chronic laryngitis.

METHODS

In this prospective blinded study, we enrolled 53 participants: 15 controls, 20 patients with GERD and 18 patients with chronic laryngitis. The latter two groups were subsequently treated with lansoprazole 30 mg bid for 12-weeks. Baseline and postacid suppressive therapy biopsies were obtained from distal oesophagus and laryngeal postcricoid areas. Biopsy specimens were evaluated for histopathology and dilated intercellular space changes.

RESULTS

There was no significant increase in oesophageal or laryngeal epithelium intercellular spaces among GERD or laryngitis patients compared with controls at baseline or postacid suppressive therapy. Only patients with GERD had significantly (P = 0.03) higher proportion of moderate-to-severe oesophageal spongiosis and basal cell hyperplasia, which normalized postacid suppressive therapy.

CONCLUSIONS

There was no increase in the width of intercellular spaces in the oesophagus or larynx in GERD or chronic laryngitis at baseline or postacid suppressive therapy. Our findings question the uniform presence of dilated intercellular space in patients with GERD.