Veronique Giroux

Estrogen receptor β deficiency enhances small intestinal tumorigenesis in ApcMin/+ mice

Clinical evidence suggests that estradiol replacement therapy reduces colon cancer risk in ‘post’menopausal women. In colon epithelial cells, the estrogen receptor β (ERβ) is the predominant ER subtype and is thought to mediate the genomic effect of estrogens. The first aim of this study was to investigate the consequence of ERβ deficiency on intestinal tumorigenesis in the ApcMin/+ mouse model. Furthermore, to explore the biological mechanisms by which estrogens may influence the pathogenesis of colorectal cancer, we performed gene expression profiles in colonocytes from ovariectomized wild‐type (WT) vs. ERβ−/− mice, treated with estradiol (E2) or vehicle. Specifically in female, ERβ deficiency was found to be associated with higher adenoma multiplicity in the small intestine, but not in the colon. Furthermore, tumors from ERβ−/−ApcMin/+ female mice were on average significantly larger than those from control ApcMin/+ mice. Higher steady‐state proliferation in epithelial cells of the jejunum and colon from ERβ−/−ApcMin/+ vs. ApcMin/+ female mice was confirmed by BrdU incorporation assay. Interestingly, functional categorization of microarray results revealed the TGFβ signaling pathway to be modulated in colonocytes, especially for the WT + E2 vs. WT + Vehicle and the ERβ−/− + E2 vs. WT + E2 comparisons. Using quantitative PCR analysis, we observed transcripts from ligands of the TGFβ pathway to be upregulated in colonocytes from E2‐treated WT and ERβ−/− mice and downregulated in ERβ‐deficient mice, mostly in an E2‐independent manner. Therefore, our results demonstrate that ERβ deficiency enhances small intestinal tumorigenesis and suggest that modulation of the TGFβ signaling pathway could contribute to the protective role of estrogens on intestinal tumorigenesis.

ERRα metabolic nuclear receptor controls growth of colon cancer cells

The estrogen-related receptor alpha (ERRα) is a nuclear receptor that acts primarily as a regulator of metabolic processes, particularly in tissues subjected to high-energy demand. In addition to its control of energy metabolism and mitochondrial biogenesis, ERRα has recently been associated with cancer progression. Notably, increased expression of ERRα has been shown in several cancerous tissues, including breast, ovary and colon. However, additional studies are required to gain insight into the action of ERRα in cancer biology, particularly in non-endocrine-related cancers. Therefore, using a short hairpin RNA-mediated approach, we investigated whether ERRα is required for the rapid growth of colon cancer cells and to maintain their neoplastic metabolic state. Results show that silencing ERRα significantly impaired colon cancer cell proliferation and colony formation in vitro as well as their in vivo tumorigenic capacity. A pronounced delay in G1-to-S cell cycle phase transition was observed in ERRα-depleted cells in association with reduced cyclin-dependent kinase 2 activity and hyperphosphorylated state of the retinoblastoma protein along with disturbed expression of several cell cycle regulators, including p15 and p27. Interestingly, ERRα-depleted HCT116 cells also displayed significant reduction in expression of a large set of key genes to glycolysis, tricarboxylic acid cycle and lipid synthesis. Furthermore, using (14)C isotope tracer analysis, ERRα depletion in colon cancer cells resulted in reduced glucose incorporation and glucose-mediated lipogenesis in these cells. These findings suggest that ERRα coordinates colon cancer cell proliferation and tumorigenic capacity with energy metabolism. Thus, ERRα could represent a promising therapeutic target in colon cancer.

Chemopreventive effect of ERβ-Selective agonist on intestinal tumorigenesis in ApcMin/+ Mice†

Epidemiological and experimental evidence suggests that estrogen replacement therapy reduces the risk of colon cancer in postmenopausal women. Estrogen receptor beta (ERβ) is thought to be the principal mediator of the estrogen effect in the colon. Recent studies by our team suggested positive regulation of the transforming growth factor (TGF)β pathway by estrogen in mice colonocytes. We therefore wanted to investigate the effects of ERβ agonist treatment on intestinal tumorigenesis in ApcMin/+ mice. Weaned ApcMin/+ mice were injected subcutaneously three times a week for 12 wk with vehicle or ERβ‐selective agonist, diarylpropionitrile (DPN, 5 mg/kg). DPN administration resulted in a significant reduction in small intestinal polyp multiplicity in both ApcMin/+ male and female mice. Furthermore, the mean diameter of small intestinal polyps was lower in DPN‐treated than vehicle‐treated males, along with lower BrdU incorporation indices in jejunal and colon epithelial cells of both sexes. DPN treatment also increased apoptosis in colon epithelium as measured by TUNEL assay and cleaved caspase 3 quantification. The effect of DPN on various components of the TGFβ pathway was also studied in colonocytes. DPN treatment increased expression of TGFβ1 and TGFβ3 transcripts, levels of nuclear and phosphorylated Smad2 as well as p27 cell‐cycle inhibitor, a TGFβ pathway target gene. Our results demonstrate that DPN treatment reduces intestinal tumorigenesis in ApcMin/+ mice. Furthermore, we suggest that positive regulation of the TGFβ pathway by ERβ activation could contribute to the protective role of estrogen in intestinal tumor development.

Integrin α6A splice variant regulates proliferation and the Wnt/β-catenin pathway in human colorectal cancer cells

Summary Integrin α6Aβ4 is up-regulated in colorectal cancers. Knockdown of α6A in adenocarcinoma cell lines revealed a sustained reduction of cell growth both in cellulo and in xenografts as well as a repression of a number of Wnt/β-catenin pathway end points.

Metaplasia: tissue injury adaptation and a precursor to the dysplasia–cancer sequence

Metaplasia is the replacement of one differentiated somatic cell type with another differentiated somatic cell type in the same tissue. Typically, metaplasia is triggered by environmental stimuli, which may act in concert with the deleterious effects of microorganisms and inflammation. The cell of origin for intestinal metaplasia in the oesophagus and stomach and for pancreatic acinar–ductal metaplasia has been posited through genetic mouse models and lineage tracing but has not been identified in other types of metaplasia, such as squamous metaplasia. A hallmark of metaplasia is a change in cellular identity, and this process can be regulated by transcription factors that initiate and/or maintain cellular identity, perhaps in concert with epigenetic reprogramming. Universally, metaplasia is a precursor to low-grade dysplasia, which can culminate in high-grade dysplasia and carcinoma. Improved clinical screening for and surveillance of metaplasia might lead to better prevention or early detection of dysplasia and cancer.

Three-Dimensional Organoids Reveal Therapy Resistance of Esophageal and Oropharyngeal Squamous Cell Carcinoma Cells

Background & Aims Oropharyngeal and esophageal squamous cell carcinomas, especially the latter, are a lethal disease, featuring intratumoral cancer cell heterogeneity and therapy resistance. To facilitate cancer therapy in personalized medicine, three-dimensional (3D) organoids may be useful for functional characterization of cancer cells ex vivo. We investigated the feasibility and the utility of patient-derived 3D organoids of esophageal and oropharyngeal squamous cell carcinomas. Methods We generated 3D organoids from paired biopsies representing tumors and adjacent normal mucosa from therapy-naïve patients and cell lines. We evaluated growth and structures of 3D organoids treated with 5-fluorouracil ex vivo. Results Tumor-derived 3D organoids were grown successfully from 15 out of 21 patients (71.4%) and passaged with recapitulation of the histopathology of the original tumors. Successful formation of tumor-derived 3D organoids was associated significantly with poor response to presurgical neoadjuvant chemotherapy or chemoradiation therapy in informative patients (P = 0.0357, progressive and stable diseases, n = 10 vs. partial response, n = 6). The 3D organoid formation capability and 5-fluorouracil resistance were accounted for by cancer cells with high CD44 expression and autophagy, respectively. Such cancer cells were found to be enriched in patient-derived 3D organoids surviving 5-fluorouracil treatment. Conclusions The single cell-based 3D organoid system may serve as a highly efficient platform to explore cancer therapeutics and therapy resistance mechanisms in conjunction with morphological and functional assays with implications for translation in personalized medicine.

O-010 Novel Regulation of Autophagy and Intestinal Homeostasis Via mRNA Binding Protein IMP1.

Background:IMP1 (Insulin-like growth factor-2 mRNA binding protein 1) is essential for normal gut development and aberrant overexpression promotes colorectal tumors; however, the role of IMP1 in epithelial homeostasis in the adult intestine remains unclear. Our preliminary findings suggest that Imp1 loss may alter autophagy in intestinal epithelium during homeostasis and response to injury. Recent studies have linked aberrations in autophagy to Crohns disease. We therefore sought to determine if Imp1-mediated changes in autophagy may affect response to injury in the intestine epithelium and whether Imp1 expression is altered in Crohns disease patients. Methods:Mice with intestine-epithelial specific Imp1 deletion (VillinCre;Imp1fl/fl) were used to evaluate autophagy flux and response to irradiation or Heligmosomoides polygyrus infection via gene expression analyses, flow cytometry, and IHC/IF. Crypt enteroid assays were utilized to evaluate stem cell growth. Imp1 expression in Crohns disease patients was evaluated via qRT-PCR. Results:Imp1 expression is enriched in the crypt region of the small intestine, and VillinCre;Imp1fl/fl mice exhibit an increase in autophagy flux and enhanced expression of Paneth and stem cell markers in isolated crypts. Following challenge with irradiation or Heligmosomoides polygyrus infection, VillinCre;Imp1fl/fl mice exhibit robust crypt enteroid growth and improved clinical parameters consistent with Imp1 loss being protective in these contexts. Analysis of tissue biopsies from Crohns disease patients reveal a significant upregulation of Imp1 compared to unaffected patients, suggesting the possibility that overexpression of Imp1 may contribute to autophagy-related pathogenesis in Crohns disease. Conclusions:Our data demonstrate in 2 independent models that intestinal epithelial deletion of Imp1 promotes enhanced recovery from injury, possibly due to upregulation of stem cell gene expression and autophagy. Furthermore, our data reveal for the first time that Imp1 expression is increased in tissue from Crohns disease patients. Taken together, our findings may suggest a novel mechanism for IMP1 to promote pathogenesis of Crohns disease via negative regulation of autophagy.

682 The Integrin a6a Splice Variant Regulates the Wnt/β-Catenin Pathway in Colon Cancer Cells

unstable as evidenced by the presence of high level of DNA damage, centrosome amplification, and aneuploidy. AIM: To investigate role and possible mechanisms of Klf4 in preserving genetic stability. METHODS: To determine the ability of Klf4 restoration in correcting the observed genetic instability in MEFS null for Klf4 (Klf4-/-), we overexpressed Klf4 in Klf4-/MEFs and compared the results to wild type (Klf4+/+) and non-transfected Klf4-/MEFs. Cell cycle profiles and proliferation curve was performed to determine growth characteristics. Quantification of chromosome number and immunohistochemical staining of centrosomes were performed to assess chromosome integrity. To determine the role of Klf4 in correcting DNA damage, we overexpressed or not Klf4 in Klf4-/MEFs followed by γ-irradiation or not in parallel with Klf4+/+ and Klf4-/MEFs. Using immunohistochemistry, γH2AX and p53BP1 foci were counted at 0, 1h, 4h and 24h after γ-irradiation. The levels of p53, p21, cyclin E, Cdk2 and γH2AX in Klf4+/+ and Klf4-/MEFs, with and without Klf4 overexpression, were determined by Western blotting. RESULTS: Overexpression of Klf4 in Klf4-/MEFs suppressed cell proliferation compared to untransfected Klf4+/+ and untransfected Klf4-/MEFs. Centrosome staining showed a 10-fold decrease in the percent of cells with ≥3 centrosomes after overexpressing Klf4 in Klf4-/MEFs compared to untransfected Klf4-/MEFs. A higher percentage of Klf4-/MEFs cells were detected with increased and sustained ≥5 γH2AX and p53BP1 foci following γ-irradiation compared to irradiated Klf4+/+ MEFs. Overexpression of Klf4 in Klf4-/MEFs reduced the percentage of cells with ≥5 γH2AX foci to a level similar to that in Klf4+/+ MEFs, while the percent of cells with ≥5 p53BP1 foci were reduced to the same level as irradiated Klf4+/+ but at a faster rate. Karyotype analysis showed that Klf4-transfected Klf4-/MEFs had a 25% decrease in number of cells exhibiting aneuploidy in contrast to untransfected Klf4-/MEFs. Western blot analysis showed that p53, cyclin E, Cdk2 and γH2AX levels were reduced and p21 was elevated following Klf4 overexpression in Klf4-/MEFs. CONCLUSION: Results of this study demonstrate that overexpression of Klf4 in MEFs null for the Klf4 alleles display evidence of improved genetic stability as illustrated by reduced DNA damage, aneuploidy, and centrosome amplification. These results indicate that KLF4 plays a crucial role in preserving genetic stability.

Abstract 30: The integrin α6A splice variant regulates colon cancer cell proliferation and the Wnt/β-catenin pathway

Colon cancer is a major cause of death by cancer in North America. Recently, we found that both subunits of the integrin α6β4 are up-regulated in colon primary tumours. The α6 integrin subunit exists as two distinct splice isoforms, α6A and α6B. It is the α6A isoform that was shown to be associated with the proliferative cell population of the normal human colon and up-regulated in colorectal cancer. The aim of this study was to analyze the role of integrin α6Aβ4 in human colon cancer, more precisely its effect on cell proliferation and its mechanism of regulation. To investigate the function of integrin α6Aβ4 in colon cancer, expression of splice variant α6A was specifically abolished, using shRNA technology, in colon adenocarcinoma cell lines (Caco-2/15, T84, SW480, SW620, DLD-1 and HT29). The function of splice variant α6A of the α6β4 integrin was investigated in vitro and in tumour xenografts. In all colon cancer cell lines tested, knockdown of the integrin α6A subunit resulted in a decrease of up to 90% of the α6A variant without affecting the levels of the α6B variant. Furthermore, no compensatory expression of α6Bβ4 integrin was observed following the abolition of the α6A subunit. In the majority of colon cancer cell lines, the knockdown of α6A resulted in a significant decrease in proliferation as show by BrdU incorporation. Moreover, it was accompanied by reduced activity of the Wnt/β-catenin pathway as measured by a decrease of responsive β-catenin/TCF promoter activity and increased β-catenin phosphorylation at Ser37/Thr41 by GSK3β. Preliminary data confirmed that in these cells, the Wnt/β-catenin pathway can be stimulated by pharmacological inhibition of GSK3β (SB216763), as displayed by a decrease of β-catenin phosphorylation at Ser37/Thr41 and an increase in responsive β-catenin/TCF promoter activity. Analysis of splice variants of the α6 integrin subunit in human colorectal cancer revealed that α6A was increased in 80% of tumours as compared to their matched resection margins and a significant correlation was observed between expression of α6A and c-myc in the tumours. Furthermore, to determine the role of the integrin α6A subunit on colon cancer tumorigenesis in vivo, control and α6A knockdown T84, SW620, HT29 and DLD-1 cells were injected into nude mice. Results showed that abolition of the integrin α6A subunit led to a significant reduction in tumour growth for T84, SW620 and HT29 colon cell lines. Moreover, analysis of tumours showed an increase in β-catenin phosphorylation at Ser37/Thr41 in T84 and HT29. Our results show for the first time that splice variant A of the integrin α6 subunit regulates the Wnt/β-catenin pathway to promote cancer cell growth. Since 80% of colon cancers display an up-regulation of integrin α6A expression, targeting this integrin in colon cancers may offer new therapeutic value. 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 30. doi:1538-7445.AM2012-30

Abstract 2045: Intriguing role of estrogen-related receptor alpha (ERRα) in colorectal cancer

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Besides its well-known function in energetic metabolism, the nuclear receptor Estrogen-Related Receptor Alpha (ERRα) has also been shown to be overexpressed in breast, ovarian, uterine, prostate and colon cancer and to be associated to a poor prognosis in some of these cancer types. Interestingly, an ERRα splice variant mainly expressed in non cancerous tissues has been reported. This variant missing the fifth exon (ERRα Δ5) is still expected to interact with DNA and form dimers but cannot recruit coactivators, therefore being devoid of any transcriptional activity. AIM: Determine the role of ERRα as well as ERRα Δ5 in intestinal tumorigenesis. METHODS: shRNA-mediated silencing of ERRα and overexpression of ERRα Δ5 were performed by lentivirus infection in DLD1 and HCT116 human colon cancer cells. The interaction between both proteins was investigated as well as their respective roles in various tumorigenic processes. RESULTS: Silencing of ERRα by shRNA reduced proliferation of DLD1 and HCT116 cells as measured by growth kinetics and anchorage-independent growth assays in soft agar. We also observed that ERRα knockdown cells grew into smaller tumors when subcutaneously implanted in NUDE mice. Furthermore, FACS-scan analysis revealed that ERRα silencing delays G1 to S phase transition in colon cancer cells. Differential expression of a splice variant of ERRα (ERRα Δ5) in cancer vs normal tissues would support the importance of ERRα role in colorectal carcinogenesis. This is the case at least for colon tumors as cancerous samples display lower amount of ERRα Δ5 and higher amount of ERRα compared to adjacent paired normal tissues, as measured by Western Blot analysis. Interaction between both variants has been characterized by immunoprecipitation assays, confirming the conserved dimerization potential of ERRα Δ5 variant with the full length ERRα. Furthermore, luciferase assays revealed that ERRα Δ5 is transcriptionaly inactive and its expression inhibits the transcriptional activity of ERRα on its target genes, suggesting that this variant acts as a dominant negative for ERRα. Interestingly, the reintroduction of ERRα Δ5 in human colon cancer cells leads to the reduction of cell growth and soft agar colony formation. CONCLUSION: Strong ERRα expression is associated with cancerous tissues and is required for the intense proliferation of colon cancer cells. Interestingly, the poorly active splice variant ERRα Δ5 is lost in cancerous colon tissues and has antiproliferative properties when reintroduced in colon cancer cells. Since this splice variant could interact with ERRα and inhibit its activity, ERRα Δ5 reduction of expression in cancerous tissue could allow ERRα to fully promote colon cancer cell proliferation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2045. doi:10.1158/1538-7445.AM2011-2045