Expression profiles of proliferative and antiapoptotic genes in sporadic and colitis‐related mouse colon cancer models

Elevated levels of survivin, telomerase catalytic subunit (TERT), integrin‐linked kinase (ILK), cyclooxygenase 2 (COX‐2), inducible nitric oxide synthase (iNOS) and the regulatory factors c‐MYB and Tcf‐4 are often found in human cancers including colorectal cancer (CRC) and have been implicated in the development and progression of tumorigenesis. The aim of this study was to determine the expression of these genes in mouse models of sporadic and colitis‐associated CRC. To address these issues, we used qRT‐PCR approach to determine changes in gene expression patterns of neoplastic cells (high‐grade dysplasia/intramucosal carcinoma) and surrounding normal epithelial cells in A/J and ICR mouse strains using laser microdissection. Both strains were injected with azoxymethane and ICR mice were also given drinking water that contained 2% dextran sodium sulphate. In both sporadic (A/J mice) and colitis‐associated (ICR mice) models of CRC, the levels of TERT mRNA, COX‐2 mRNA and Tcf‐4 mRNA were higher in neoplastic cells than in surrounding normal epithelial cells. In contrast, survivin mRNA was upregulated only in neoplastic cells from A/J mice and ILK mRNA was upregulated only in neoplastic cells from ICR mice. However, the expression of iNOS mRNA was similar in normal and neoplastic cells in both models and c‐MYB mRNA was actually downregulated in neoplastic cells compared with normal cells in both models. These findings suggest that the genetic background and/or the molecular mechanisms of tumorigenesis associated with genotoxic insults and colonic inflammation influence the gene expression of mTERT, COX‐2, Tcf‐4, c‐MYB, ILK and survivin in colon epithelial neoplasia.     

Survivin-induced Aurora-B kinase activation: A mechanism by which APC mutations contribute to increased mitoses during colon cancer development

APC mutations initiate most colorectal cancers (CRCs), but cellular mechanisms linking this to CRC pathology are unclear. We reported that wild-type APC in the colon down-regulates the anti-apoptotic protein survivin, and APC mutation up-regulates it, explaining why most CRCs display survivin overexpression and apoptosis inhibition. However, it does not explain another hallmark of CRC pathology--increased mitotic figures and cell proliferation. Because survivin activates aurora-B kinase (ABK) in vitro, catalyzing mitosis, we hypothesized that in normal colonic crypts, APC controls ABK activity, while in neoplastic APC-mutant crypts, ABK activity is up-regulated, increasing mitosis. We quantitatively mapped intracryptal distributions of survivin, ABK, and markers of activated downstream signaling and mitosis (INCENP, phospho-histone-H3, phospho-centromere-protein-A). In normal crypts, gradients for these markers, ABK:survivin:INCENP complexes, and ABK activity were highest in the lower crypt (inverse to the APC gradient). In neoplastic crypts that harbor APC mutations, proliferating (Ki-67+) cells and cells expressing survivin, ABK, and phospho-histone-H3 were distributed farther up the crypt. Hence, as cells migrate up neoplastic crypts, transitions between cell phenotypes (eg, from stem to proliferating) appear delayed. In CRC cell lines, increasing wild-type APC, inhibiting TCF-4, or decreasing survivin expression down-regulated ABK activity. Thus, APC mutation-induced up-regulation of the survivin/ABK cascade can explain delayed crypt cell maturation, expansion of proliferative cell populations (including mitotic figures), and promotion of colon tumorigenesis.     

p27 Expression in Inflammatory Bowel Disease-Associated Neoplasia : Further Evidence of a Unique Molecular Pathogenesis

The cyclin-dependent kinase inhibitor p27 is a negative regulator of the transition from G1 to S phase of the cell cycle, protects against inflammatory injury and promotes epithelial differentiation. Because p27 protein has been shown to be abnormally expressed both in dysplasia associated with Barrett's esophagus and in sporadic colorectal adenomas, we used immunohistochemistry to evaluate p27 expression in inflammatory bowel disease (IBD)-associated dysplasia and carcinomas. Normal, inflamed, and transitional mucosa, sporadic adenomas, and sporadic colonic carcinomas were studied as controls. In normal colonic epithelium p27 expression was restricted to the superficial, terminally differentiated cells. In colitic and inflamed diverticular mucosa p27 was expressed in the base of the crypts in 86 and 70% of cases, respectively. Similarly, in transitional mucosa adjacent to sporadic carcinomas p27 was expressed in the base of the crypts in all cases. Strong p27 expression extended more frequently from the base of the crypts to superficial cells in IBD-associated dysplasia than in sporadic adenomas (P < 0.007). Twenty of 20 (100%) IBD-associated carcinomas showed low p27 expression (<50% nuclei positive) compared to 6 of 20 (30%) stage-matched sporadic colorectal carcinomas (P < 0.001). We conclude (i) aberrant p27 protein expression in inflamed and IBD-associated nondysplastic mucosa is indistinguishable from that found in transitional mucosa adjacent to sporadic carcinomas; (ii) p27 is overexpressed in dysplastic lesions, perhaps as an attempt to counterbalance proliferative stimuli; and (iii) IBD-associated colorectal carcinomas have significantly lower p27 expression, commonly associated with poor prognosis, than stage-matched sporadic colorectal carcinomas. These findings further substantiate the existence of divergent molecular pathogenetic pathways between these types of carcinomas and suggest an intrinsically more aggressive behavior of IBD-associated colon carcinomas compared to sporadic ones.     

Loss of miR‐101 expression promotes Wnt/β‐catenin signalling pathway activation and malignancy in colon cancer cells

Colorectal cancer (CRC) is the second leading cause of cancer‐related mortality in Western countries. Although the aberrant expression of several microRNAs (oncomiRs) is associated with CRC progression, the molecular mechanisms of this phenomenon are still under investigation. Here we show that miR‐101 expression is differentially impaired in CRC specimens, depending on tumour grade. miR‐101 re‐expression suppresses cell growth in 3D, hypoxic survival and invasive potential in CRC cells showing low levels of miR‐101. Additionally, we provide molecular evidence of a bidirectional regulatory mechanism between miR‐101 expression and important CRC pro‐malignant features, such as inflammation, activation of the Wnt/β‐catenin signalling pathway and epithelial–mesenchymal transition (EMT). We then propose that up‐regulated miR‐101 may function as a tumour suppressor in CRC and that its pharmacological restoration might hamper the aggressive behaviour of CRC in vivo. MiR‐101 expression may also represent a cancer biomarker for CRC diagnosis and prognosis. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

APC mutation and the crypt cycle in murine and human intestine.

Dysplastic colon adenomas are thought to arise from growth of clones of APC -/- colonic epithelial cells. Isolated clusters of dysplastic crypts are often observed in patients with familial adenomatous polyposis. These patients have genotype APC +/-, and the clusters of dysplastic crypts (called microadenoma or aberrant crypt foci) are thought to represent an early stage in the expansion of a mutant clone of APC -/- cells. It is thought that the growth of these clusters of mutant crypts results from crypt replication through a process similar to what occurs in the normal crypt cycle. We measured the relative replication rate of mutant crypts by analyzing the size of clusters of mutant crypts in APC +/- individuals and found that mutant APC -/- crypts replicate more rapidly than do normal APC +/- (i.e., nonneoplastic) crypts. In contrast, the replication rate of mutant crypts in Apc +/- mice is not significantly different from that of normal crypts, thus supporting previous findings that aberrant crypt foci do not contribute significantly to the colon adenoma population in adult Apc +/- mice. Intriguingly, we found an effect of Apc heterozygosity on the frequency of branching crypts in young mice.     

Role of inherited defects of MYH in the development of sporadic colorectal cancer

Biallelic germ-line variants of the 8-hydroxyguanine repair gene MYH have been associated with multiple colorectal adenomas that display somatic G:C-->T:A transversions in APC. However, the effect of single germ-line variants has not been widely studied. To examine the relationship between monoallelic MYH variants and susceptibility to sporadic colorectal cancer (CRC), 92 cases of sporadic CRC, 19 cases of familial CRC not meeting the Bethesda guidelines, 17 cases with multiple adenomas, and 53 normal blood donors were screened for 8 potentially pathogenic germ-line MYH variants. Loss of heterozygosity (LOH) at 1p adjacent to the MYH locus, microsatellite instability (MSI) status, and somatic mutations in KRAS2 and APC were analyzed in sporadic cancers. Neither homozygote nor compound heterozygote MYH variants were observed in the germ-line of any subjects with sporadic CRC. There was no difference in the incidence of monoallelic variants between this group (20 of 92, 22%) and cancer-free controls (14 of 53, 26%). However, the presence of monoallelic germ-line MYH variants was negatively associated with an MSI-high (MSI-H) tumor phenotype, with an incidence of only 1 of 23 (4%) MSI-H CRCs as contrasted with 19 of 69 (28%) non-MSI-H (P=0.02). Further, 4 of 5 tumors with 1p LOH contained monoallelic MYH variants compared with 15 of 53 without 1p LOH (P=0.04) and the normal population (P=0.03). The presence of G:C-->T:A transversions in KRAS2 or APC was significantly more common in single MYH variant tumors (9 of 12) than in MYH wild-type tumors (11 of 33; P=0.02). These results suggest that single germ-line variants of MYH may influence genetic pathways in CRC.     

Tensin4 (TNS4) is upregulated by Wnt signalling in adenomas in multiple intestinal neoplasia (Min) mice

Apc^Min/+ mice are regarded as a standard animal model of colorectal cancer (CRC). Tensin4 (TNS4 or Cten) is a putative oncogene conferring features of stemness and promoting motility. Our objective was to assess TNS4 expression in intestinal adenomas and determine whether TNS4 is upregulated by Wnt signalling. Apc^Min/+ mice (n = 11) were sacrificed at approximately 120 days old at the onset of anaemia signs. Small intestines were harvested, and Swiss roll preparations were tested for TNS4 expression by immunohistochemistry (IHC). Individual polyps were also separately collected (n = 14) and tested for TNS4 mRNA expression and Kras mutation. The relationship between Wnt signalling and TNS4 expression was tested by Western blotting in the human CRC cell line HCT116 after inhibition of β‐catenin activity with MSAB or its increase by transfection with a Flag β‐catenin expression vector. Overall, 135/148 (91.2%) of the total intestinal polyps were positive for TNS4 expression by IHC, whilst adjacent normal areas were negative. RT‐qPCR analysis showed approximately 5‐fold upregulation of TNS4 mRNA in the polyps compared to adjacent normal tissue and no Kras mutations were detected. In HCT116, β‐catenin inhibition resulted in reduced TNS4 expression, and conversely, β‐catenin overexpression resulted in increased TNS4 expression. In conclusion, this is the first report linking aberrant Wnt signalling to upregulation of TNS4 both during initiation of intestinal adenomas in mice and in in vitro models. The exact contribution of TNS4 to adenoma development remains to be investigated, but the Apc^Min/+ mouse represents a good model to study this.     

Fibromatosis of the breast and mutations involving the APC/beta-catenin pathway

Fibromatoses of the breast are nonmetastasizing tumors, but can be infiltrative and locally recurrent. Breast fibromatoses are rare, and their specific genetic alterations have not been elucidated. However, their occasional occurrence in patients with familial adenomatous polyposis (FAP) and their morphologic identification with other deep fibromatoses (desmoid tumors) suggest that alterations of the APC/beta-catenin pathway might be involved in the pathogenesis of sporadic and FAP-associated breast fibromatoses. We analyzed somatic beta-catenin and APC gene mutations in 33 breast fibromatoses (32 sporadic and 1 FAP-associated) using immunohistochemistry for beta-catenin, 5q allelic loss assays, and direct DNA sequencing for exon 3 of the beta-catenin gene and the mutation cluster region of the APC gene. Nuclear accumulation of beta-catenin was present in the stromal tumor cells in most (82%) cases but not in normal stroma or mammary epithelial cells. Somatic alterations of the APC/beta-catenin pathway were detected in 79% of breast fibromatoses, including activating beta-catenin gene mutations in 15 cases and somatic APC alterations (mutation or 5q allelic loss or both) in 11. These findings indicate that alterations of the APC/beta-catenin pathway with resultant nuclear translocation of beta-catenin are important in the pathogenesis of both sporadic and FAP-associated breast fibromatosis. The spectrum of beta-catenin and APC alterations is similar to that described for desmoid tumors of the abdomen, paraspinal region, and extremities.     

Gastrointestinal stem cells and cancer

Cancer is believed to be a disease involving stem cells. The digestive tract has a very high cancer prevalence partly owing to rapid epithelial cell turnover and exposure to dietary toxins. Work on the hereditary cancer syndromes including familial adenomatous polyposis (FAP) has led to significant advances, including the adenoma-carcinoma sequence. The initial mutation involved in this stepwise progression is in the "gatekeeper" tumor suppressor gene adenomatous polyposis coli (APC). In FAP somatic, second hits in this gene are nonrandom events, selected for by the position of the germ-line mutation. Extensive work in both the mouse and human has shown that crypts are clonal units and mutated stem cells may develop a selective advantage, eventually forming a clonal crypt population by a process called "niche succession." Aberrant crypt foci are then formed by the longitudinal division of crypts into two daughter units--crypt fission. The early growth of adenomas is contentious with two main theories, the "top-down" and "bottom-up" hypotheses, attempting to explain the spread of dysplastic tissue in the bowel. Initial X chromosome inactivation studies suggested that colorectal tumors were monoclonal; however, work on a rare XO/XY human patient with FAP and chimeric Min mice showed that 76% of adenomas were polyclonal. A reduction in tumor multiplicity in the chimeric mouse model has been achieved by the introduction of a homozygous tumor resistance allele. This model has been used to suggest that short-range interaction between adjacent initiated crypts, not random polyp collision, is responsible for tumor polyclonality.     

Ets2 regulates colonic stem cells and sensitivity to tumorigenesis

Ets2 has both tumor repressive and supportive functions for different types of cancer. We have investigated the role of Ets2 within intestinal epithelial cells in postnatal mouse colon development and tumorigenesis. Conditional inactivation of Ets2 within intestinal epithelial cells results in over representation of Ets2-deficient colon crypts within young and adult animals. This preferential representation is associated with an increased number of proliferative cells within the stem cell region and an increased rate of crypt fission in young mice that result in larger patches of Ets2-deficient crypts. These effects are consistent with a selective advantage of Ets2-deficient intestinal stem cells in colonizing colonic crypts and driving crypt fission. Ets2-deficient colon crypts have an increased mucosal thickness, an increased number of goblet cells, and an increased density. Mice with Ets2-deficient intestinal cells develop more colon tumors in response to treatment with azoxymethane and dextran sulfate sodium. The selective population of colon crypts, the altered differentiation state and increased sensitivity to carcinogen-induced tumors all indicate that Ets2 deficiency alters colon stem cell number or behavior. Ets2-dependent, epithelial cell-autonomous repression of intestinal tumors may contribute to protection from colon cancer of persons with increased dosage of chromosome 21.     

Comprehensive genetic and functional characterization of IPH‐926: a novel CDH1‐null tumour cell line from human lobular breast cancer

Infiltrating lobular breast cancer (ILBC) is a clinically and biologically distinct tumour entity defined by a characteristic linear cord invasion pattern and inactivation of the CDH1 tumour suppressor gene encoding for E‐cadherin. ILBCs also lack β‐catenin expression and show aberrant cytoplasmic localization of the E‐cadherin binding protein p120‐catenin. The lack of a well‐characterized ILBC cell line has hampered the functional characterization of ILBC cells in vitro. We report the establishment of a permanent ILBC cell line, named IPH‐926, which was derived from a patient with metastatic ILBC. The DNA fingerprint of IPH‐926 verified genetic identity with the patient and had no match among the human cell line collections of several international biological resource banks. IPH‐926 expressed various epithelial cell markers but lacked expression of E‐cadherin due to a previously unreported, homozygous CDH1 241ins4 frameshift mutation. Detection of the same CDH1 241ins4 mutation in archival tumour tissue of the corresponding primary ILBC proved the clonal origin of IPH‐926 from this particular tumour. IPH‐926 also lacked β‐catenin expression and showed aberrant cytoplasmic localization of p120‐catenin. Array‐CGH analysis of IPH‐926 revealed a profile of genomic imbalances that included many distinct alterations previously observed in primary ILBCs. Spectral karyotyping of IPH‐926 showed a hyperdiploid chromosome complement and numerous clonal, structural aberrations. IPH‐926 cells were anti‐cancer drug‐resistant, clonogenic in soft agar, and tumourigenic in SCID mice. In xenograft tumours, IPH‐926 cells recapitulated the linear cord invasion pattern that defines ILBCs. In summary, IPH‐926 significantly extends the biological spectrum of the established breast cancer cell lines and will facilitate functional analyses of genuine human ILBC cells in vitro and in vivo. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Wnt/β‐Catenin Signaling Pathway Upregulates c‐Myc Expression to Promote Cell Proliferation of P19 Teratocarcinoma Cells

Aberrant activation of the Wnt/β‐catenin signaling pathway is a common event in human tumor progression. Wnt signaling has also been implicated in maintaining a variety of adult and embryonic stem cells by imposing a restraint to differentiation. To understand the function and mechanism of Wnt/β‐catenin signaling on the pathogenesis of teratocarcinoma, we used the mouse teratocarcinoma P19 cell line as a model in vitro. Gsk3β specific inhibitor (SB216763) was used to activate Wnt/β‐catenin signaling. All trans‐retinoic acid (RA) was used to induce P19 cell differentiation. At different culture times, gene expression was examined by immunofluorescence staining, quantitative real‐time PCR, and Western‐blotting; BrdU incorporation assays were performed to measure P19 cell proliferation. Small interference RNA technology was used to downregulate c‐myc expression. The results showed that SB216763 induced the nuclear translocation of β‐catenin, upregulated the expression of c‐myc and pluripotency related genes, oct4, sox2 and nanog, and blocked cell differentiation induced by all trans‐RA. The proliferation of P19 cells was significantly enhanced by SB216763, as well as c‐myc overexpression. C‐myc downregulation inhibited P19 cell proliferation caused by activation of Wnt/β‐catenin signaling and induced P19 cell differentiation. In conclusion, activation of the Wnt/β‐catenin pathway could promote the proliferation and inhibit the differentiation of mouse teratocarcinoma cells by upregulation of c‐myc expression. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.     

TUSC3 promotes colorectal cancer progression and epithelial–mesenchymal transition (EMT) through WNT/β‐catenin and MAPK signalling

Colorectal cancer (CRC) is one of the most common malignancies and is the second leading cause of cancer death in humans. Tumour suppressor candidate 3 (TUSC3) plays an important role in embryogenesis and metabolism. Deletion of TUSC3 often causes non‐syndromic mental retardation. Even though TUSC3 deregulation is frequently observed in epithelial cancers, the function of TUSC3 in CRC has remained unknown. In this study, we observed greater expression of TUSC3 at the mRNA and protein level in clinical colorectal tumour samples compared with paired normal tissues. Gain‐ and loss‐of‐function analyses were performed to evaluate the functional significance of TUSC3 in CRC initiation and progression. Immunoblotting, immunofluorescence, and co‐immunoprecipitation analyses were used to identify potential pathways with which TUSC3 might be involved. Overexpression of TUSC3 in CRC cells induced epithelial–mesenchymal transition (EMT) in CRC cells, accompanied by down‐regulation of the epithelial marker, E‐cadherin, and up‐regulation of the mesenchymal marker, vimentin. Increased proliferation, migration, and invasion, as well as accelerated xenograft tumour growth, were observed in TUSC3‐overexpressing CRC cells, while opposite effects were achieved in TUSC3‐silenced cells. In conclusion, our study demonstrated the oncogenic role of TUSC3 in CRC and showed that TUSC3 may be responsible for alternations in the proliferation ability, aggressiveness, and invasive/metastatic potential of CRC through regulating the MAPK, PI3K/Akt, and Wnt/β‐catenin signalling pathways. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.