Effect of TGF-beta on differentiated organoids of the colon carcinoma cell line LIM 1863

Bioengineering functional human sphincteric and non-sphincteric gastrointestinal smooth muscle constructs

Digestion and motility of luminal content through the gastrointestinal (GI) tract are achieved by cooperation between distinct cell types. Much of the 3 dimensional (3D) in vitro modeling used to study the GI physiology and disease focus solely on epithelial cells and not smooth muscle cells (SMCs). SMCs of the gut function either to propel and mix luminal contents (phasic; non-sphincteric) or to act as barriers to prevent the movement of luminal materials (tonic; sphincteric). Motility disorders including pyloric stenosis and chronic intestinal pseudoobstruction (CIPO) affect sphincteric and non-sphincteric SMCs, respectively. Bioengineering offers a useful tool to develop functional GI tissue mimics that possess similar characteristics to native tissue. The objective of this study was to bioengineer 3D human pyloric sphincter and small intestinal (SI) constructs in vitro that recapitulate the contractile phenotypes of sphincteric and non-sphincteric human GI SMCs. Bioengineered 3D human pylorus and circular SI SMC constructs were developed and displayed a contractile phenotype. Constructs composed of human pylorus SMCs displayed tonic SMC characteristics, including generation of basal tone, at higher levels than SI SMC constructs which is similar to what is seen in native tissue. Both constructs contracted in response to potassium chloride (KCl) and acetylcholine (ACh) and relaxed in response to vasoactive intestinal peptide (VIP). These studies provide the first bioengineered human pylorus constructs that maintain a sphincteric phenotype. These bioengineered constructs provide appropriate models to study motility disorders of the gut or replacement tissues for various GI organs.

Regional differences in prostaglandin E₂ metabolism in human colorectal cancer liver metastases

Background

Prostaglandin (PG) E₂ plays a critical role in colorectal cancer (CRC) progression, including epithelial-mesenchymal transition (EMT). Activity of the rate-limiting enzyme for PGE₂ catabolism (15-hydroxyprostaglandin dehydrogenase [15-PGDH]) is dependent on availability of NAD+. We tested the hypothesis that there is intra-tumoral variability in PGE₂ content, as well as in levels and activity of 15-PGDH, in human CRC liver metastases (CRCLM). To understand possible underlying mechanisms, we investigated the relationship between hypoxia, 15-PGDH and PGE₂ in human CRC cells in vitro.

Methods

Tissue from the periphery and centre of 20 human CRCLM was analysed for PGE₂ levels, 15-PGDH and cyclooxygenase (COX)-2 expression, 15-PGDH activity, and NAD+/NADH levels. EMT of LIM1863 human CRC cells was induced by transforming growth factor (TGF) β.

Results

PGE₂ levels were significantly higher in the centre of CRCLM compared with peripheral tissue (P = 0.04). There were increased levels of 15-PGDH protein in the centre of CRCLM associated with reduced 15-PGDH activity and low NAD+/NADH levels. There was no significant heterogeneity in COX-2 protein expression. NAD+ availability controlled 15-PGDH activity in human CRC cells in vitro. Hypoxia induced 15-PGDH expression in human CRC cells and promoted EMT, in a similar manner to PGE₂. Combined 15-PGDH expression and loss of membranous E-cadherin (EMT biomarker) were present in the centre of human CRCLM in vivo.

Conclusions

There is significant intra-tumoral heterogeneity in PGE₂ content, 15-PGDH activity and NAD+ availability in human CRCLM. Tumour micro-environment (including hypoxia)-driven differences in PGE₂ metabolism should be targeted for novel treatment of advanced CRC.

miR-21 and miR-31 converge on TIAM1 to regulate migration and invasion of colon carcinoma cells

TGF-β promotes cell migration and invasion, an attribute that is linked to the pro-metastasis function of this cytokine in late stage cancers. The LIM 1863 colon carcinoma organoid undergoes epithelial-mesenchymal transition (EMT) in response to TGF-β. This process is markedly accelerated by TNF-α, and we found that the levels of miR-21 and miR-31 were prominently elevated under the synergistic actions of TGF-β/TNF-α. Consistent with this, overexpression of either miR-21 or miR-31 significantly enhanced the effect of TGF-β alone on LIM 1863 morphological changes. More importantly, transwell assays demonstrated the positive effects of both miR-21 and miR-31 in TGF-β regulation of LIM 1863 motility and invasiveness. Elevated levels of miR-21 and miR-31 also enhanced motility and invasiveness of other colon carcinoma cell lines. We present compelling evidence that TIAM1, a guanidine exchange factor of the Rac GTPase, is a direct target of both miR-21 and miR-31. Indeed in LIM 1863 cells, suppression of TIAM1 is required for miR-21/miR-31 to enhance cell migration and invasion. Therefore, we have uncovered miR-21 and miR-31 as downstream effectors of TGF-β in facilitating invasion and metastasis of colon carcinoma cells.

A human three-dimensional cell line model allows the study of dynamic and reversible epithelial-mesenchymal and mesenchymal-epithelial transition that underpins colorectal carcinogenesis

Developmental morphogenesis relies on cell transitions between epithelial and mesenchymal states. Colorectal cancer (CRC) progression can also be described as 'morphogenesis' as it involves epithelial-mesenchymal transition (EMT), whereby tumour cells become more invasive and metastatic. Subsequently, the disseminated tumour cells must undergo a reverse transition (MET), as the pathology of most primary tumours is re-capitulated by their established metastases. Disseminated tumour cells can remain 'dormant' for many years. Consequently, tumour initiation at the secondary site is the rate-limiting step in metastasis. Metastasis is governed by cell intrinsic and extrinsic (microenvironment) factors, thus much of what we know about metastasis is drawn from in vivo model systems. However, the molecular mechanisms controlling release from 'dormancy' are still largely unknown due to the complexity this presents for the in vivo situation. An in vitro morphogenesis culture system would present a great advantage. To this end, we have established a unique model of CRC morphogenesis, using a variant of the human cell line LIM1863 (LIM1863-Mph). In this model system LIM1863-Mph cells show plasticity between epithelial and mesenchymal states. The transitions are reversible and bear the phenotypic hallmarks of CRC morphogenesis. Importantly, we have demonstrated a pivotal role for FZD7 in these phenotype transitions, implicating Wnt signalling in orchestrating CRC morphogenesis.

Epithelial-Mesenchymal Transition and Colorectal Cancer: Gaining Insights into Tumor Progression Using LIM 1863 Cells

In addition to allowing epithelial cells to escape the structural constraints imposed by tissue architecture and adopt a phenotype more amenable to cell movement, it is now recognized that the epithelial-mesenchymal transition (EMT) may also represent a critical component permitting the progression of carcinomas towards invasive and metastatic disease. However, data supporting the actual occurrence of EMT in specific solid tumors and its relevance to the process of progression of these cancers has been scant. Despite an extensive knowledge of the genetic basis for colorectal cancer, the translation of this information into effective treatments has been limited. Clearly, there is a desperate need for new and improved therapies and since the switch to a metastatic phenotype is critical for outcome, it is of paramount importance to elucidate the biology that underlies the progression of this disease. Thus, the unique LIM 1863 model for studying the EMT of colorectal carcinoma has been used to both substantiate the importance of the transition for this cancer type and to identify molecular events that contribute to disease progression. Importantly, it has emerged that not only does EMT enhance migratory capacity, but also elicits additional selective advantages to colonic tumor cells. Specifically, the acquisition of autocrine growth factor signaling loops, mechanisms to evade apoptosis, and expression of specific integrins allowing invasive cells to interact with interstitial matrices and sustain activation of TGF-beta combine to provide a compelling new biochemical framework for understanding how EMT contributes to tumor evolution.

Frizzled-7 dictates three-dimensional organization of colorectal cancer cell carcinoids

Progression of colorectal cancer (CRC) involves spatial and temporal occurrences of epithelial-mesenchymal transition (EMT), whereby tumour cells acquire a more invasive and metastatic phenotype. Subsequently, the disseminated mesenchymal tumour cells must undergo a reverse transition (mesenchymal-epithelial transition, MET) at the site of metastases, as most metastases recapitulate the pathology of their corresponding primary tumours. Importantly, initiation of tumour growth at the secondary site is the rate-limiting step in metastasis. However, investigation of this dynamic reversible EMT and MET that underpins CRC morphogenesis has been hindered by a lack of suitable in vitro models. To this end, we have established a unique in vitro model of CRC morphogenesis, which we term LIM1863-Mph (morphogenetic). LIM1863-Mph cells spontaneously undergo cyclic transitions between two-dimensional monolayer (migratory, mesenchymal) and three-dimensional sphere (carcinoid, epithelial) states. Using RNAi, we demonstrate that FZD7 is necessary for MET of the monolayer cells as loss of FZD7 results in the persistence of a mesenchymal state (increased SNAI2/decreased E-cadherin). Moreover, FZD7 is also required for migration of the LIM1863-Mph monolayer cells. During development, FZD7 orchestrates either migratory or epithelialization events depending on the context. Our findings strongly implicate similar functional diversity for FZD7 during CRC morphogenesis.

Characterization of colonic polyps by two-dimensional gel electrophoresis

To identify proteins that may specifically characterize colonic polyps we have investigated the abundance of numerous proteins in epithelial cells from 15 normal colon specimens and 13 colonic polyps, using two-dimensional gel analysis to detect possible differences in expression. Silver-stained digitized images of the gels were analyzed with Melanie II 2.1 software. We consistently detected more than 700 protein spots on each gel, and found that the intensity of 59 of them was significantly altered in polyp specimens (Wilcoxon test assuming P< or =0.05). Immunostaining, microsequencing and mass spectrometry (matrix-assisted laser desorption/ionization - time of flight; MALDI-TOF) techniques were used to identify these proteins and selected others that did not show differential regulation. The expression of numatrin (nucleophosphine/B23), hsp 70, and hsp60 was increased in polyps; levels of fatty acid binding protein (L-FABP), 14-3-3 sigma, citokeratin 20, cytochrome c oxidase polypeptide Va, Rho GDP-dissociation inhibitor (Rho GDI), and beta- and gamma-actins were decreased. Although the levels of expression of a given protein often varied among polyp specimens, it generally held true that the direction of variation (up or down) remained constant across the panel. We concluded that proteins showing constant differential regulation across all or most of the polyp specimens represent the most characteristic regulatory pathways in colon polyps, while more sporadic variations reflect characteristics of individual polyps.

Engagement of variant CD44 confers resistance to anti-integrin antibody-mediated apoptosis in a colon carcinoma cell line

The LIM 1863 colon carcinoma cell line grows as structured organoids around a central lumen, and we have previously demonstrated that the three-dimensional arrangement protects the individual cells from apoptosis induced by an anti-alpha v integrin antibody, 23C6 (Bates et al., 1994). Here we show that the intercellular forces which drive spheroid formation can be overcome by exposure of the cells to a collagen substrate, or more specifically through ligation of the CD44 receptor by a monoclonal antibody. Binding to immobilized anti-CD44 antibody induced a monolayer morphology which is accompanied by fibronectin production and secretion, and expression of the integrin alpha v beta 6. Significantly, the cells of the monolayer acquired resistance to 23C6 antibody-mediated apoptosis over time and this property was sustained even after removal from the monolayer. We provide data to show that this resistance is not dependent on monolayer morphology, constant engagement of the CD44 receptor, loss of the 23C6 antigen, or elevation of Bcl-2 or Bcl-XL protein. The CD44 expressed by LIM 1863 is shown to be the metastatic variant of the molecule therefore these results provide a possible explanation for the selective advantages conferred by expression of this variant for metastasizing colon cancer cells. Overall, the findings of this study support a model for the development of malignancy through the production of specific survival and growth signals as a direct consequence of a signaling event induced by stimulation of an epithelial variant of CD44.