Proliferation Of Colon Carcinoma Cells Research Articles

Inhibitory effect of selective cyclooxygenase-2 inhibitor NS-398 on proliferation and invasion of human colorectal cancer cells

Objective:To investigate the effect of NS-398,a selective cyclooxygenase-2(COX-2) inhibitor,on the proliferation and invasion of human colon carcinoma cells in vitro,so as to determine the possibility of COX-2 as a new target for treatment of colon carcinoma.Methods: The expression of COX-2 in colorectal cancer cells(CW-2,COLO-320) was detected by RT-PCR and Western blotting.COLO-320 cell proliferation was measured by MTT after treatment with NS-398.Cell invasion ability was measured using migration and invasion chamber systems.Western blotting assay was used to examine the influence of NS-398 on MMP-2 expression.Results: Our results showed that CW-2,COLO-320 cells expressed COX-2 mRNA and protein.NS-398 inhibited the proliferation of COLO-320 cells in a time-and concentration-dependent manner.Invasion test showed that NS-398 inhibited the migration and invasion of COLO-320 cells.Western blotting revealed that NS-398 inhibited the expression of MMP-2 in COLO-320 cells.Conclusion: The selective COX-2 inhibitor NS-398 can inhibit COLO-320 cell proliferation and invasion,indicating COX-2 may serve as a new target for colon carcinoma treatment.

In vitro studies on the inhibition of colon cancer by butyrate and carnitine

Objective Epidemiologic studies support an association between diet and the incidence of colorectal cancer. Butyrate, a short-chain fatty acid present in dietary fiber and dairy products, is a potential anticarcinogenic compound. We previously showed that carnitine can enhance the bioavailability of butyrate in vivo. In the present study, we evaluated the effects of butyrate alone and in combination with carnitine on colon cancer cells in vitro, examining proliferation and apoptosis and the molecular mechanisms by which these nutrients may inhibit colon cancer. Methods Caco-2 cells, a well-established cell model, were incubated with butyrate (2.5–20 mM) with or without carnitine (10 mM) for various incubation periods. Proliferation was measured by incorporation of 3H-thymidine, and apoptosis was detected using flow cytometry, and then confirmed by analyzing the presence of single-strand DNA breaks typical of apoptotic cells. Prostaglandin E 2 production was assayed and Bcl-2 and cyclo-oxygenase-2 expressions were examined by western blotting. Results Butyrate and carnitine inhibited Caco-2 cell proliferation ( P < 0.05) and induced apoptosis ( P < 0.05). Prostaglandin E 2 production was decreased in treated Caco-2 cells. At the molecular level, the expression of proapoptotic Bax and Bak proteins were increased in cells incubated with butyrate and carnitine, whereas expression of antiapoptotic Bcl-x L was decreased. Cyclo-oxygenase-2 expression was decreased in cells incubated with butyrate and carnitine. Conclusions Butyrate and carnitine inhibit human colon carcinoma cell proliferation and induce apoptosis in human colon carcinoma cells. This is accompanied by an appreciable alteration of the Bax-to-Bcl-x L and Bak-to-Bcl-x L ratios in favor of apoptosis. This study provides a scientific rationale to study the effects of carnitine and butyrate in colon cancer in vivo.

Bestrophin 1 promotes epithelial-to-mesenchymal transition of renal collecting duct cells.

Bestrophin 1 (Best1) controls intracellular Ca(2+) concentration, induces Ca(2+)-activated Cl(-) conductance, and increases proliferation of colon carcinoma cells. Here, we show that expression of Best1 in mouse renal collecting duct (CD) cells causes i) an increase in cell proliferation, ii) a loss of amiloride-sensitive Na(+) absorption, iii) induction of Ca(2+)-dependent Cl(-) conductance (CaCC), and iv) epithelial-to-mesenchymal transition. During conditions of high proliferation or when we exposed CD cells to serum or TGF-beta1, we observed upregulation of Best1, increased CaCC, redistribution of the epithelial-to-mesenchymal transition marker beta-catenin, and upregulation of vimentin. In contrast, suppression of Best1 by RNAi inhibited proliferation, reduced CaCC, and downregulated markers of EMT. CaCC and expression of Best1 were independent of the cell cycle but clearly correlated to cell proliferation and cell density. During renal inflammation in LPS-treated mice or after unilateral ureteral obstruction, we observed transient upregulation of Best1. These data indicate that repression of cell proliferation, CaCC, and expression of Best1 occurs during mesenchymal-to-epithelial transition once CD cells polarize and terminally differentiate. These results may suggest a role for Best1 in renal fibrosis and tissue repair.

Adipocytokines – mediators of fat tissue linking obesity and cancer

Obesity is a dramatically increasing public health problem worldwide. Traditionally, fat tissue was considered to be solely an energy storage depot. However, recent studies have shown that adipose tissue exerts important endocrine functions, which are predominantly mediated by a network of various soluble factors derived from adipocytes. New evidence has come to light elucidating a modulatory role of this adipocytokines in the regulation of cancer development. For example, adipocytokines such as leptin were shown to have an effect on breast cancer progression. In this study we have investigated the impact of leptin on the proliferation and migration of colon carcinoma cells. Treatment of human SW480 colon carcinoma cells with leptin resulted in a significant increase of the proliferation. In parallel, using our unique 3D cell migration assay and time-lapse video microscopy, leptin strongly stimulated the spontaneous migratory activity from 29% locomoting cells to 52%. This leptin-induced migration resulted in an activation of various transcription factors such as Stat-3 and c-Jun. Accordingly the phosphorylation of Stat-3 was accompanied by an increase of SOCS-3, its negative feedback regulator. Furthermore, using a Stat-3 specific inhibitor inhibited the leptin-induced migration. Understanding the impact of different adipocytokines on tumour migration and the underlying signal transduction mechanisms is mandatory for the future development of cancer therapy.

Effects of specific HDGF siRNA on proliferation of human colon carcinoma cells

Effects of specific HDGF siRNA on proliferation of human colon carcinoma cells

Docosahexaenoic acid suppresses arachidonic acid-induced proliferation of LS-174T human colon carcinoma cells

To investigate the impact of arachidonic acid (AA) and docosahexaenoic acid (DHA) and their combination on colon cancer cell growth. The LS-174T colon cancer cell line was used to study the role of the prostaglandin precursor AA and the omega-3 polyunsaturated fatty acid DHA on cell growth. Cell viability was assessed in XTT assays. For analysis of cell cycle and cell death, flow cytometry and DAPI staining were applied. Expression of cyclooxygenase-2 (COX-2), p21 and bcl-2 in cells incubated with AA or DHA was examined by real-time RT-PCR. Prostaglandin E(2) (PGE(2)) generation in the presence of AA and DHA was measured using a PGE(2)-ELISA. AA increased cell growth, whereas DHA reduced viability of LS 174T cells in a time- and dose-dependent manner. Furthermore, DHA down- regulated mRNA of bcl-2 and up-regulated p21. Interestingly, DHA was able to suppress AA-induced cell proliferation and significantly lowered AA-derived PGE(2) formation. DHA also down-regulated COX-2 expression. In addition to the effect on PGE(2) formation, DHA directly reduced PGE(2)-induced cell proliferation in a dose-dependent manner. These results suggest that DHA can inhibit the pro-proliferative effect of abundant AA or PGE(2).

Activation of Apoptosis by 1-Hydroxy-5,7-Dimethoxy-2-Naphthalene-Carboxaldehyde, a Novel Compound from Aegle marmelos

We have identified a natural compound that activates apoptosis of epithelial cancer cells through activation of tumor necrosis factor-alpha (TNF-alpha), TNF receptor (TNFR)-associated death domain (TRADD), and caspases. The molecule 1-hydroxy-5,7-dimethoxy-2-naphthalene-carboxaldehyde (HDNC, marmelin) was isolated and characterized from ethyl acetate fraction of extracts of Aegle marmelos. HDNC treatment inhibited the growth of HCT-116 colon cancer tumor xenografts in vivo. Immunostaining for CD31 showed that there was a significant reduction in microvessels in the HDNC-treated animals, coupled with decreased cyclooxygenase-2, interleukin-8, and vascular endothelial growth factor mRNA. Using hexoseaminidase assay, we determined that HDNC inhibits proliferation of HCT-116 colon and HEp-2 alveolar epithelial carcinoma cells. Furthermore, the cancer cells showed increased levels of activated caspase-3 and induced G(1) cell cycle arrest, which was suppressed by caspase-3 inhibitors. HDNC induced TNF-alpha, TNFR1, and TRADD mRNA and protein expression. Moreover, caspase-8 and Bid activation, and cytochrome c release, were observed, suggesting the existence of a cross-talk between death receptor and the mitochondrial pathways. HDNC inhibited AKT and extracellular signal-regulated kinase phosphorylation both in cells in culture and in tumor xenografts. In addition, electrophoretic mobility shift assay and luciferase reporter assays showed that HDNC significantly suppressed TNF-alpha-mediated activation and translocation of nuclear factor-kappaB (NF-kappaB). This was further confirmed by Western blot analysis of nuclear extracts wherein levels of RelA, the p65 component of NF-kappaB, were significantly less in cells treated with HDNC. Together, the data suggest that the novel compound HDNC (marmelin) is a potent anticancer agent that induces apoptosis during G(1) phase of the cell cycle and could be a potential chemotherapeutic candidate.

Effect of the chemokine receptor CXCR7 on proliferation of carcinoma cells in vitro and in vivo

The chemokine CXCL12/SDF-1 and its receptor CXCR4 have been implicated in invasion, survival and proliferation of carcinoma cells. Recently, CXCR7 was identified as a second receptor for CXCL12. We observed that CXCL12 promoted proliferation of CT26 colon and KEP1 mammary carcinoma cells, and this was blocked when CXCR7 was downregulated by ‘intrakines’ or RNAi, but not by CXCR4 inhibitors. The K1R mutant of CXCL12, which acts as a CXCR4 antagonist, also promoted proliferation through CXCR7 and is therefore a selective CXCR7 agonist. The effect of CXCR7 was not due to reduced apoptosis, and CXCR7 mediated chemotaxis of the carcinoma cells towards CXCL12. These results differ from those in a previous report on other carcinoma cells. We conclude that CXCL12 can be a potent growth factor for carcinoma cells by acting on CXCR7. Nevertheless, we observed no effect of complete and stable CXCR7 suppression on the growth of s.c. tumours or lung metastases of KEP1 and CT26 cells. A CXCR7 inhibitor has been reported to reduce growth of other tumours. Our results indicate that this inhibitor may not be applicable to therapy of all carcinomas.

Butyrate metabolism in human colon carcinoma cells: Implications concerning its growth‐inhibitory effect

Butyrate and acetate are bacterial metabolites present in the large intestine lumen. Although butyrate is well known to inhibit the in vitro proliferation of human colon carcinoma cells in a process involving the hyperacetylation of specific nuclear histones, little is known about the possible link between butyrate metabolism and its growth-inhibitory effect. In a previous study (Leschelle et al., 2000, Eur J Biochem 267: 6435-6442), we showed that butyrate accumulates and is metabolized in HT-29 Glc(-/+) cells without increasing oxygen consumption. In the present study, using the same cell line incubated with (14)C-labeled butyrate, we determined that a minor part of (14)C from butyrate was recovered in nuclear histones. Unlike butyrate, acetate exerted no effect on cell growth but was a precursor for overall net histone acetylation. Although butyrate was able to increase the cellular AMP/ADP ratio, it did not affect the ATP cell content or the adenylate charge or the oxidation of endogenous L-glutamine. Butyrate oxidation was found to be markedly sensitive to the presence of other substrates with D-glucose decreasing this oxidation and L-malate stimulating it. Furthermore, in the presence of L-malate, the growth-inhibitory effect of butyrate was significantly weaker than in its absence. From these data, we conclude that the metabolism of butyrate downstream acetyl-CoA synthesis is not involved in the butyrate antiproliferative effect. The suggestion that butyrate metabolism in mitochondria is not used in these cells as a fuel but acts as a regulator of butyrate free concentrations (thus limiting its action upon cellular targets), is discussed.

Hypoxia-induced BNIP3 reduces proliferation of colon carcinoma cells through downregulation of ERK1/2

Cancer cells require glycolysis for energy; this results in excessive lactate production and secretion. Lactate, the end product of glycolysis, reduces the extracellular pH and contributes to the proliferation, invasiveness, metastasis, and angiogenesis of tumor cells. Our previous results revealed that the over-expressed CD147/basigin plays a critical role in malignant melanoma (MM) invasiveness, metastasis and angiogenesis; CD147 has also been implicated in a specific and strong interaction with monocarboxylate transporters (MCT) 1 and 4 that mediate the transport of lactate. In the present study, we investigated whether CD147/basigin is involved, via its association with MCT1 and 4 to transport lactate, in glycolysis and then contributes to the progression of A375 melanoma cells. A375 cells expressed remarkably higher CD147, MCT1 and 4 and showed increased glycolysis rate compared with normal human melanocytes (NHMC). CD147/basigin co-localized with MCT1 and 4 in the A375 cell membrane. Furthermore, silencing of CD147/basigin in A375 cells by a siRNA clearly abrogated the expression of MCT1 and 4 and their co-localization with CD147/basigin and dramatically decreased the glycolysis rate, extracellular pH, and the production of ATP. Thus, cell proliferation, invasiveness, and VEGF production were significantly decreased by siRNA. These results strongly suggest that highly-expressed CD147 interacts with MCT1 and 4 to promote tumor cell glycolysis, resulting in the progression of MM.

Structurally Distinct Phosphatases CD45 and CD148 Both Regulate B Cell and Macrophage Immunoreceptor Signaling

The receptor-type protein tyrosine phosphatase (RPTP) CD148 is thought to have an inhibitory function in signaling and proliferation in nonhematopoietic cells. However, its role in the immune system has not been thoroughly studied. Our analysis of CD148 loss-of-function mice showed that CD148 has a positive regulatory function in B cells and macrophages, similar to the role of CD45 as a positive regulator of Src family kinases (SFKs). Analysis of CD148 and CD45 doubly deficient B cells and macrophages revealed hyperphosphorylation of the C-terminal inhibitory tyrosine of SFKs accompanied by substantial alterations in B and myeloid lineage development and defective immunoreceptor signaling. Because these findings suggest the C-terminal tyrosine of SFKs is a common substrate for both CD148 and CD45 phosphatases and imply a level of redundancy not previously appreciated, a reassessment of the function of CD45 in the B and myeloid lineages based on prior data from the CD45-deficient mouse is warranted.

Synthesis and Antitumor Activity of Combretastatin D-4

Combretastatin D-4 1 was synthesized using electrochemical dimerization of phenols as the key step. Anodic oxidation of bromochloro-phenol 7 provided the corresponding diaryl ether 8. Manipulation of the two hydroxyl groups differenciated, provided the seco-acid, which on Mitsunobu reaction gave the target molecule. Its biological assay showed new potent inhibitory activity against cellular proliferation of human HT-29 colon carcinoma cells.

Cleaved High Molecular Weight Kininogen (HKa) and Kininostatin (D5) Induce Apoptosis and Inhibit Migration and Invasion of Human Prostate Cancer Cells by Preventing AKT Phosphorylation and Cyclin D1 Synthesis and Disrupting the Interaction of UPAR and EGFR.

Tumor metastasis is a major factor in the mortality rate in human prostate cancer. Upregulation and activation of EGFR and/or uPAR in a variety of cancers have been shown to be associated with poor prognosis. HK, a component of the plasma kallikrein-kinin system, can be hydrolyzed by plasma kallikrein to bradykinin and HKa. HKa and D5 both have been demonstrated to have potent anti-angiogenic activity in vitro and in vivo. We previously published that D5 directly inhibits human colon carcinoma cell (HCT-116) proliferation in vitro by blocking the G1/S transition in the cell cycle. We now show that HKa [100 nM] inhibits the migration of human prostate tumor cell (DU145) about 50%. Cyclin D1 can activate p21 and p27 with concomitant cell migration. DU145 cells rapidly increase cyclin D1 synthesis in response to bFGF [1.2 nM]. HKa suppresses cyclin D1 expression as shown by Western blotting as well as cell immunoflourescence. Stimulation by bFGF or VEGF results in clustering of uPAR and EGFR on the surface of DU145 cells. Immunoflourescence shows that the addition of HKa disrupts the co-localization of uPAR and EGFR. HKa or a monoclonal antibody against uPAR decreases the phosphorylation of EGFR at Tyr 1173. The phosphorylation of ERK and AKT, which are downstream effectors of EGFR, is also inhibited by HKa. Kininostatin [300nM] induced apoptosis of human prostate cancer cells challenged with uPA [50 nM] or EGF [6.7 nM]. Matrigel invasion assay reveals that HKa [100 nM] decreases the invading cell number by 90%. These novel data indicate that HKa and kininostatin induce apoptosis and inhibit migration and invasion of human prostate cancer cells, indicating the therapeutic potential of kininostatin in metastasis human prostate cancer.

Sox17 and Sox4 Differentially Regulate β-Catenin/T-Cell Factor Activity and Proliferation of Colon Carcinoma Cells

The canonical Wnt pathway is necessary for gut epithelial cell proliferation, and aberrant activation of this pathway causes intestinal neoplasia. We report a novel mechanism by which the Sox family of transcription factors regulate the canonical Wnt signaling pathway. We found that some Sox proteins antagonize while others enhance beta-catenin/T-cell factor (TCF) activity. Sox17, which is expressed in the normal gut epithelium but exhibits reduced expression in intestinal neoplasia, is antagonistic to Wnt signaling. When overexpressed in SW480 colon carcinoma cells, Sox17 represses beta-catenin/TCF activity in a dose-dependent manner and inhibits proliferation. Sox17 and Sox4 are expressed in mutually exclusive domains in normal and neoplastic gut tissues, and gain- and loss-of-function studies demonstrate that Sox4 enhances beta-catenin/TCF activity and the proliferation of SW480 cells. In addition to binding beta-catenin, both Sox17 and Sox4 physically interact with TCF/lymphoid enhancer factor (LEF) family members via their respective high-mobility-group box domains. Results from gain- and loss-of-function experiments suggest that the interaction of Sox proteins with beta-catenin and TCF/LEF proteins regulates the stability of beta-catenin and TCF/LEF. In particular, Sox17 promotes the degradation of both beta-catenin and TCF proteins via a noncanonical, glycogen synthase kinase 3beta-independent mechanism that can be blocked by proteasome inhibitors. In contrast, Sox4 may function to stabilize beta-catenin protein. These findings indicate that Sox proteins can act as both antagonists and agonists of beta-catenin/TCF activity, and this mechanism may regulate Wnt signaling responses in many developmental and disease contexts.

Downregulation of human colon carcinoma cell (COLO‐205) proliferation through PKG‐MAP kinase mediated signaling cascade by E. coli heat stable enterotoxin (STa), a potent anti‐angiogenic and anti‐metastatic molecule

It was reported earlier that Escherichia coli heat stable enterotoxin (STa), a major causative agent of secretory diarrhea, can also inhibit the proliferation of colon carcinoma cells with the involvement of cGMP mediated calcium influx. In the present study it is shown that E. coli STa inhibits cell proliferation in the colonic carcinoma cell line COLO-205 by the PKG-ERK44/42 mediated signaling pathway. This enterotoxin negatively regulates cell proliferation by downregulating the activity of ERK44/42(MAPK) and subsequently the activity of a transcription regulatory protein cMyc. The antiproliferative effect of STa was reversed by LY83583, a guanylate cyclase (GC) inhibitor and KT5823, a PKG inhibitor. Thus suggesting the involvement of cGMP dependent protein kinase (PKG) in the downregulation of ERK44/42 and subsequent inactivation of cMyc activity. Moreover, it has been shown that a specific ERK44/42 inhibitor, PD98059, also inhibits cMyc activation and cell proliferation, which further confirms the involvement of ERK44/42 in the activation of cMyc. It is also shown that E. coli STa significantly inhibits the vascular endothelial growth factor (VEGF, a potent angiogenic factor) expression in COLO-205 cells and also downregulates vascular cell adhesion molecule-1 (VCAM-1, a potent metastatic factor) expression on the COLO-205 cell surface. So it is reported for the first time that E. coli STa inhibits the proliferation of the colonic carcinoma cell line COLO-205 by the PKG-ERK44/42 mediated pathway and it may have a role against the development of colon carcinoma.

The tetraspanin CD9 inhibits the proliferation and tumorigenicity of human colon carcinoma cells

The implication of the tetraspanin CD9 in cancer has received much recent attention and an inverse correlation between CD9 expression and the metastatic potential and cancer survival rate has been established for different tumor types. In contrast to the well-established role of CD9 in metastasis, very little is known about the involvement of this tetraspanin in the process of development of primary tumors. In the present study, we present evidence on the implication of CD9 in colon carcinoma tumorigenesis. We report here that ectopic expression of CD9 in colon carcinoma cells results in enhanced integrin-dependent adhesion and inhibition of cell growth. Consistently with these effects, treatment of these cells with anti-CD9-specific antibodies resulted in (i) increased beta1 integrin-mediated cell adhesion through a mechanism involving clustering of integrin molecules rather than altered affinity; (ii) induction of morphological changes characterized by the acquisition of an elongated cell phenotype; (iii) inhibition of cell proliferation with no significant effect on cell survival; (iv) increased expression of membrane TNF-alpha, and finally (v) inhibition of the in vivo tumorigenic capacity in nude mice. In addition, through the use of selective blockers of TNF-alpha, we have demonstrated that this cytokine partly mediates the antiproliferative effects of CD9. These results clearly establish for the first time a role for CD9 in the tumorigenic process.

Domain 5 of kininogen inhibits proliferation of human colon cancer cell line (HCT-116) by interfering with G1/S in the cell cycle.

Domain 5 (D5) of kininogen inhibits endothelial cell adhesion, migration, proliferation and angiogenesis by inducing apoptosis and disrupting a signaling pathway initiated by binding to the urokinase receptor (uPAR). Because tumor cells frequently overexpress uPAR, we hypothesized that D5 can directly inhibit proliferation of colon carcinoma cells. A recombinant fusion protein of D5 and glutathione S-transferase (GST-D5) but not GST at 280 nm inhibited proliferation of human colon carcinoma cells (HCT-116) in vitro by 75-86%. We found that treatment with GST-D5 did not affect the survival pathway, phosphatidylinositol 3-kinase or the apoptotic pathway. In contrast, the G1/S phase transition of the cell cycle was downregulated as evidenced by an increase of cells in G0/G1 and a decrease in cells in S by flow cytometry. We found a decrease in serine phosphorylation of the retinoblastoma protein Rb (p107) after incubation with GST-D5. Less E2F-1 transcription factor and p107 were released and fewer cells overcame the G1/S growth restriction point. Expression levels of cyclins D1, A and E were reduced as measured by densiometric analysis of western blots. Cyclin-dependent protein kinase activities were downregulated and p27, the cyclin-dependent kinase inhibitor, was activated by GST-D5. These findings indicate that D5 of high molecular weight kininogen interferes with the G1 to S phase transition, reducing the proliferation of human colon carcinoma cells.

5-aminosalicylic acid in combination with nimesulide inhibits proliferation of colon carcinoma cells in vitro

To investigate the effects of 5-aminosalicylic acid (5-ASA) in combination with nimesulide on the proliferation of HT-29 colon carcinoma cells and its potential mechanisms. Inhibitory effects of drugs (5-ASA, nimesulide and their combination) on HT-29 colon carcinoma cells were investigated by thiazolyl blue tetrazolium bromide (MTT) assay. Cellular apoptosis and proliferation were detected by TUNEL assay and immunocytochemical staining, respectively. Pretreatment with 5-ASA or nimesulide at the concentration of 10-1000 micromol/L inhibited proliferation of HT-29 colon carcinoma cells in a dose-dependent manner in vitro (t=5.122, P<0.05; t=3.086, P<0.05, respectively). The inhibition rate of HT-29 colon carcinoma cell proliferation was also increased when pretreated with 5-ASA (100 micromol/L) or nimesulide (100 micromol/L) for 12-96 h, which showed an obvious time-effect relationship (t=6.149, P<0.05; t=4.159, P<0.05, respectively). At the concentration of 10-500 micromol/L, the apoptotic rate of HT-29 colon carcinoma cells significantly increased (t=18.156, P<0.001; t=19.983, P<0.001, respectively), while expression of proliferating cell nuclear antigen (PCNA) was remarkably decreased (t=6.828, P<0.05; t=14.024, P<0.05, respectively). 5-ASA in combination with nimesulide suppressed the proliferation of HT-29 colon carcinoma cells more than either of these agents in a dose-dependent and time-dependent manner (t=5.448, P<0.05; t=4.428, P<0.05, respectively). 5-ASA and nimesulide may inhibit the proliferation of HT-29 colon carcinoma cells and coadministration of these agents may have additional chemopreventive potential.

DEP-1 protein tyrosine phosphatase inhibits proliferation and migration of colon carcinoma cells and is upregulated by protective nutrients

The transmembrane protein-tyrosine phosphatase (PTP) DEP-1 (density-enhanced phosphatase) is a candidate tumor suppressor in the colon epithelium. We have explored the function of DEP-1 in colon epithelial cells by inducible re-expression in a DEP-1-deficient human colon cancer cell line. Density-enhanced phosphatase-1 re-expression led to profound inhibition of cell proliferation and cell migration, and was associated with cytoskeletal rearrangements. These effects were dependent on the PTP activity of DEP-1 as they were not observed with cells expressing the catalytically inactive DEP-1 C1239S variant. shRNA-mediated suppression of DEP-1 in a colon epithelial cell line with high endogenous DEP-1 levels enhanced proliferation, further supporting the antiproliferative function of DEP-1. Nutrients, which are considered to be chemoprotective with respect to colon cancer development, including butyrate, green tea and apple polyphenols, had the capacity to elevate transcription of endogenous DEP-1 mRNA and expression of DEP-1 protein. Upregulation of DEP-1 expression, and in turn inhibition of cell growth and migration may present a previously unrecognized mechanism of chemoprevention by nutrients.

Guanylyl Cyclase C Regulates the Intestinal Crypt‐Villus Axis

Guanylyl cyclase C (GCC), the receptor for diarrheagenic bacterial heat-stable enterotoxins (STs) and the endogenous ligands guanylin and uroguanylin, is specifically expressed in apical membranes of intestinal epithelial cells where it regulates fluid and electrolyte secretion. However, a novel paradigm is emerging in which GCC signaling regulates the proliferation of human colon carcinoma cells. Here, the role of GCC in regulating enterocyte dynamics along the crypt-villus axis was examined. GCC target-inactivated (GCC−/−) mice exhibit elongated crypts from the duodenum to the colon, populated by more rapidly cycling progenitor cells. Further, enterocytes exhibited increased rates of migration and apoptosis, but decreased differentiation, along the crypt-villus axis of GCC−/− mice. Moreover, activation of GCC reduced proliferation of cells in human normal colonic mucosa obtained from patients and inhibited cell cycle progression of NCM460 human colonic crypt cells. Indeed, GCC delayed G1/S cell cycle transition which was mediated by cGMP-dependent protein kinase. These data demonstrate that GCC contributes to the homeostatic transition from proliferation to differentiation along the intestinal crypt-villus axis. Since expression of the endogenous ligands is frequently lost during colorectal carcinogenesis, GCC may represent a novel intestinal tumor suppressor.