Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HT29 Cells”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1987

Changes in villin synthesis and subcellular distribution during intestinal differentiation of HT29-18 clones.

Brush border in enterocytes is a cell surface specialization intimately associated with terminal differentiation of these cells. HT29-18, a clone derived from the HT-29 human colonic adenocarcinoma cell line, and HT29-18-C1, a subclone from HT29-18 described in the companion paper (Huet, C., C. Sahuquillo-Merino, E. Coudrier, and D. Louvard, 1987, J. Cell Biol., 105:345-357), undergo terminal differentiation with brush borders in the absence of glucose or upon replacement of glucose by galactose in the medium. Taking advantage of this clone and its subclone which can be manipulated in vitro, we have studied the synthesis and subcellular distribution of villin, one major protein in the microvillus core of the brush border. For this study, a monoclonal antibody against villin (BDID2C3) has been isolated and characterized in detail. In addition an ELISA has been set up to measure villin accurately in total cell extracts. Villin content in differentiated HT29-18 cells is close to that seen in normal human colonic cells but 10 times lower in undifferentiated HT29-18 cells. The rate of villin synthesis is dramatically increased in the course of enterocytic differentiation, while villin is remarkably stable after synthesis. We have recently shown, using a cDNA probe for villin, that this change is controlled either at the transcription level or by RNA stabilization (Pringault, E., M. Arpin, A. Garcia, J. Finidori, and D. Louvard, 1986, EMBO (Eur. Mol. Biol. Organ.) J., 5:3119-3124). As shown by immunofluorescence and immunogold labelings, villin is targeted to the brush border area of differentiated HT29-18 cells but remains diffusely distributed in undifferentiated ones.

Adenocarcinoma↗
PubMed2005

Induction of p21WAF1 expression protects HT29 colon cancer cells from apoptosis induced by cryoinjury.

BACKGROUND: Cryotherapy is a method of in situ destruction of tumors by freeze/thaw mechanisms. Cancer cells located in the peripheral zone of the tumor undergoing cryotherapy can die by apoptosis. We hypothesized that p21WAF1 is involved in the mediation of cryotherapy-induced apoptosis. METHODS: HT29 cells grown on a plate were subjected to -10 degrees C and returned to 37 degrees C for various periods of time. Cells were analyzed by flow cytometry, Western blot, and reverse transcriptase-polymerase chain reaction for determining cell-cycle distribution, p21WAF1 protein expression, and messenger RNA levels, respectively. The p21WAF1 expression in nude mouse tumor xenografts after cryotherapy was examined by immunofluorescence staining. A series of the p21WAF1 promoter cloned into a luciferase reporter vector were transfected into HT29 cells for identifying the response element to cryoinjury. Antisense oligodeoxynucleotide (ODN) was applied to examine the effect of p21WAF1 expression on cryotherapy-induced apoptosis. RESULTS: Both protein and messenger RNA of p21WAF1 were induced by cryoinjury in cultured cells and tumor xenografts. Deletion analysis of the p21WAF1 promoter revealed that a region from -121 to -95 base pairs was responsible for the activation and that this activation was p53 independent. HT29 cells arrested at the G1 phase after cryoinjury. The cryotherapy-induced apoptotic rate in HT29 cells was increased in the presence of antisense p21WAF1 ODN in comparison to the random ODN. CONCLUSIONS: Induction of p21WAF1 increases tumor cell survival and may result in recurrences at treated sites after cryotherapy. Combining antisense ODN targeted against p21WAF1 and cryotherapy may improve clinical outcomes in the treatment of colorectal cancer.

Apoptosis↗
PubMed2005

Epigallocatechin-3-gallate suppresses galactose-alpha1,4-galactose-1beta,4-glucose ceramide expression in TNF-alpha stimulated human intestinal epithelial cells through inhibition of MAPKs and NF-kappaB.

Intestinal epithelial cells (IECs) have been known to produce galactose-alpha1,4-galactose-beta1,4-glucose ceramide (Gb3) that play an important role in the mucosal immune response. The regulation of Gb3 is important to prevent tissue damage causing shiga like toxin. Epigallocatechin-3-gallate (EGCG) has been studied as anti-carcinogenic, anti-oxidant, anti-angiogenic, and anti-viral activities, and anti-diabetic. However, little is known between the expressions of Gb3 on IECs. The aim of this study was to examine the inhibitory effect of EGCG, a major ingredient of green tea, on Gb3 production via mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) in the TNF-alpha stimulated human colon epithelial cells, HT29. To investigate how Gb3 is regulated, ceramide glucosyltransferase (CGT), lactosylceramide synthase (GalT2), and Gb3 synthase (GalT6) were analyzed by RT-PCR in HT 29 cells exposed to TNF-alpha in the presence or absence of EGCG. EGCG dose-dependently manner, inhibits TNF-alpha induced Gb3 expression by blocking in both the MAPKs and NF-kappaB pathways in HT29 cells. TNF-alpha enhanced CGT, GalT2 and GalT6 mRNA levels and EGCG suppressed the level of these enzymes enhanced by TNF-alpha treatment.

Apoptosis↗
PubMed1997

Prevention of fluorodeoxyuridine-induced cytotoxicity and DNA damage in HT29 colon carcinoma cells by conditional expression of wild-type p53 phenotype.

We have examined the effects of conditionally expressing wild-type p53 activity in HT29 cells on DNA damage and cytotoxicity caused by exposure to fluorodeoxyuridine (FdUrd). Expression of wild-type p53 phenotype for 24 hr before FdUrd treatment provided HT29 cells with virtually complete protection from cytotoxicity caused by this drug. In addition, wild-type p53 expression also prevented FdUrd-induced DNA double-strand breaks and, unexpectedly, single-strand breaks in parental (mature) DNA. Temporary expression of wild-type p53 activity in the absence of drug treatment caused some loss of clonogenicity, although the magnitude of this cytotoxic effect was small compared with the level of cell kill obtained by treatment with cytotoxic drugs for similar periods of time, indicating that HT29 cells are not highly sensitive to induction of programmed cell death by wild-type p53. Because these observations conflict with previously suggested models for FdUrd-induced damage to parental DNA, we propose an alternative model to explain how incorporation of uracil into nascent DNA might result in single-strand breaks in the opposite (parental) strand and how these breaks might be converted to the double-strand breaks that produce cell death.

Animals↗
PubMed1992

cAMP-dependent activation of small-conductance Cl- channels in HT29 colon carcinoma cells.

The present study was performed to examine the conductance properties in the colon carcinoma cell line HT29 and the activation of Cl- channels by cAMP. A modified cell-attached nystatin patch-clamp technique was used, allowing for the simultaneous recording of the cell membrane potential (PD) and the conductance properties of the cell-attached membrane. In resting cells, PD was -56 +/- 0.4 mV (n = 294). Changing the respective ion concentrations in the bath indicate that these cells possess a dominating K+ conductance and a smaller Cl- conductance. A significant non-selective cation conductance, which could not be inhibited by amiloride, was only observed in cells examined early after plating. The K+ conductance was reversibly inhibited by 1 - 5 mmol/l Ba2+. Stimulation of the cells by the secretagogues isoproterenol and vasointestinal polypeptide (VIP) depolarized PD and induced a Cl- conductance. Similar results were obtained with compounds increasing cytosolic cAMP: forskolin, 3-isobutyl-1-methylxanthine, cholera toxin and 8-bromoadenosine cyclic 3',5'-monophosphate (8-Br-cAMP). VIP (1 nmol/l, n = 10) and isoproterenol (1 mumol/l, n = 12) depolarized the cells dose-dependently and reversibly by 12 +/- 2 mV and 13 +/- 2 mV. The maximal depolarization was reached after some 20 s. The depolarization was due to increases in the fractional Cl- conductance. Simultaneously the conductance of the cell-attached membrane increased from 155 +/- 31 pS to 253 +/- 40 pS (VIP, n = 4) and from 170 +/- 43 pS to 268 +/- 56 pS (isoproterenol, n = 11), reflecting the gating of Cl- channels in the cell-attached membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed2002

Growth phase-dependent expression of ICAD-L/DFF45 modulates the pattern of apoptosis in human colonic cancer cells.

The inhibitor of caspase-3-activated DNase (ICAD) is a caspase-3 substrate that controls nuclear apoptosis. ICAD has two isoforms: a functional isoform of M(r) 45,000, ICAD-L/DNA fragmentation factor (DFF) 45; and a M(r) 35,000 isoform, ICAD-S/DFF35. ICAD-deficient murine cells display resistance to apoptotic stimuli and absence of typical nuclear changes of apoptosis. Our aim was to: (a) characterize the ICAD expression in several human colonic cancer cell lines compared with human normal colonocytes; and (b) correlate the phenotypic features of apoptosis to the level of ICAD expression. ICAD expression was assessed by immunoblot analysis. Early markers of apoptosis of cultured cells included lactate dehydrogenase retention in dying cells, cytokeratin 18 cleavage, and caspase-3 activation. Nuclear markers of apoptosis were assessed by Hoechst staining of nuclei, electron microscopy, and DNA electrophoresis. Inhibition of caspases was performed using a broad-spectrum caspase inhibitor, z-Val-Ala-Asp-fluoromethyl ketone. ICAD expression was restricted to the functional ICAD-L/DFF45 isoform in colonic cancer cells as well as in human normal colonocytes. In a clonal derivative of HT29 cells (HT29-Cl.16E cells), ICAD expression was found to be down-regulated during the exponential phase of growth, and the cell death triggered by IFN-gamma, anti-Fas antibody plus Adriamycin was characterized by the expression of early markers of apoptosis, whereas the key nuclear features of apoptosis were absent. In contrast, exposure of confluent cells to this treatment led to a typical apoptotic nuclear fragmentation. Both forms of apoptosis, in exponentially growing and confluent cells, were sensitive to the broad spectrum inhibitor of caspases, z-Val-Ala-Asp-fluoromethyl ketone. Our findings support the concept that the expression of ICAD is essential to the execution of full-blown apoptosis in colonic cancer cells. Altogether, our results point to ICAD as a potential target for restoring a normal apoptotic signal transduction pathway in colonic cancer cells.

Apoptosis↗
PubMed1998

Selective cytostatic and cytotoxic effects of glucosinolates hydrolysis products on human colon cancer cells in vitro.

Glucosinolates hydrolysis products are attracting increasing attention since many studies have suggested that they may be involved in the anticarcinogenic property of cruciferous vegetables. In this study, we show that diindolylmethane (DIM) and sulforaphane, produced during the hydrolysis of glucobrassicin and glucoraphanin, respectively, exert a dose-dependent cytotoxicity on human colon adenocarcinoma HT29 cells. Moreover, these products are able to inhibit quiescent cells to re-enter the cell cycle. Interestingly, our results clearly show that low doses of DIM and sulforaphane, although very effective on undifferentiated intestinal HT29 cells, do not affect the viability of the differentiated CaCo2 cells. The reversibility of their effects has also been tested and is discussed.

Antineoplastic Agents↗
PubMed2006

Elevation of radiolabelled thymidine uptake in RIF-1 fibrosarcoma and HT29 colon adenocarcinoma cells after treatment with thymidylate synthase inhibitors.

PURPOSE: We recently showed an increase in tumour uptake of 2-[(11)C]thymidine in patients with gastrointestinal malignancies after thymidylate synthase (TS) inhibition. To understand the phenomenon in more detail, we investigated whether TS inhibition by different TS inhibitors leads to a dose- and time-dependent change in the uptake of radiolabelled thymidine, and whether radiotracer uptake is related to changes in cell viability resulting from treatment. METHODS: RIF-1 and HT29 cells were treated with the TS inhibitors 5-fluorouracil (5-FU) and AG337 (nolatrexed dihydrochloride), as well as cisplatin as control. The cell viability and net accumulation of [(3)H]thymidine after a 1-h pulse was determined at different times after drug treatment. RESULTS: In both cell lines, [(3)H]thymidine uptake increased after a 2-h treatment with 5-FU, in a dose- and time-dependent manner. [(3)H]thymidine uptake decreased at 24 and 48 h post treatment. AG337 also produced a similar effect. In contrast to the TS inhibitors, cisplatin decreased [(3)H]thymidine uptake in RIF-1 and HT29 cells at all time points. Cell viability was compromised only after 24 h. CONCLUSION: Using two types of TS inhibitor, we have shown an increase in [(3)H]thymidine uptake, in a dose-dependent manner, a few hours after TS inhibition when the cell viability was not compromised. This effect was not seen with a non-TS inhibitor. These findings suggest that 2-[(11)C]thymidine positron emission tomography can be used to study TS inhibition in vivo at early time points when cell viability is not compromised and may therefore be helpful in the development of new TS inhibitors and in differentiating between patients with tumours sensitive to TS inhibitors and those unlikely to respond.

Adenocarcinoma↗
PubMed2003

Expression of ICAM-1 in colon epithelial cells: an ultrastructural study performed on in vivo and in vitro models.

BACKGROUND: Studies have suggested that in ulcerative colitis (UC), intercellular adhesion molecule-1 (ICAM-1) is involved in migration of leukocytes toward the colonic epithelium. A suitable in vitro model of chronic colonic inflammation does not exist, and the role of the epithelium is based on monolayers of cancer cells. Conflicting results exist on epithelial ICAM-1 expression, and the aim of this study was to compare the expression in various models of colonic epithelium. MATERIALS AND METHODS: Colonic biopsies from four UC patients and four controls were examined by cryoimmuno-electron microscopy using ICAM-1-antibodies. In four other controls, the epithelium was isolated from colonic biopsies, embedded in collagen, and evaluated similarly. Isolated crypts and cultured cancer cells were stimulated with interferon-gamma (IFN-gamma) or tumor necrosis factor-alpha (TNF-alpha). RESULTS: ICAM-1 was not expressed in the biopsies. In contrast, HT29 cells and the collagen-embedded crypts expressed ICAM-1 on the apical membranes proximal to the junctional complexes when stimulated with IFN-gamma or TNF-alpha in a dose-related manner. CONCLUSIONS: ICAM-1 is not expressed on colonic epithelium in vivo. However, both colonocytes and HT29 cells were capable of expressing ICAM-1 on their apical membranes in response to supraphysiologic cytokine concentrations. These observations question the justification of extrapolating observations from colon cancer cell lines to in vivo inflammatory conditions.

Adult↗
PubMed1990

Overexpression of protein kinase C in HT29 colon cancer cells causes growth inhibition and tumor suppression.

By using a retrovirus-derived vector system, we generated derivatives of the human colon cancer cell line HT29 that stably overexpress a full-length cDNA encoding the beta 1 isoform of rat protein kinase C (PKC). Two of these cell lines, PKC6 and PKC7, displayed an 11- to 15-fold increase in PKC activity when compared with the C1 control cell line that carries the vector lacking the PKC cDNA insert. Both of the overexpresser cell lines exhibited striking alterations in morphology when exposed to the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Following exposure to TPA, PKC6 and PKC7 cells displayed increased doubling time, decreased saturation density, and loss of anchorage-independent growth in soft agar; but these effects were not seen with the C1 cells. Also, in contrast to the control cells, the PKC-overproducing cells failed to display evidence of differentiation, as measured by alkaline phosphatase activity, when exposed to sodium butyrate. In addition, the PKC-overexpresser cells displayed decreased tumorigenicity in nude mice, even in the absence of treatment with TPA. These results provide the first direct evidence that PKC can inhibit tumor cell growth. Thus, in some tumors, PKC might act as a growth-suppressor gene.

Animals↗
PubMed2006

Biological activities of malvidin, a red wine anthocyanidin.

Malvidin (mv) has been identified as a potential inhibitor of 3',5'-cyclic adenosine monophosphate (cAMP) phosphodiesterases (PDE). This study was to investigate if, as a possible consequence of intracellular PDE inhibition, the activity of the mitogen-activated protein kinase (MAPK) cascade is affected by mv treatment. At a concentration of 5 microM of mv a significant decrease of phosphorylated ERK1 and ERK2 (ERK, extracellular regulated kinase) in HT29 cells was observed. However, an increase in substance concentration led to a substantial recurrence of the phosphorylated enzymes. Cell cycle analysis underlined that indeed G(1)-relevant targets are only marginally affected by mv. The recurrence of phosphorylated ERK1/2 and the lack of effectiveness on the G(1)-passage up to 100 microM indicated that the inhibition of cAMP-specific PDEs is of minor relevance for the growth-inhibitory properties of mv in HT29 cells. In contrast, the release of cells, synchronised in the G(2)/M-phase of the cell cycle by nocodazole treatment, was effectively blocked in the presence of 1 microM mv. These results suggest that mv interferes with cellular targets relevant for G(2)/M-progression which have not been identified so far.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1992

Inhibition of human immunodeficiency virus infection in human colon epithelial cells by recombinant interferon-gamma.

Pretreatment of human colon epithelial cells HT29 by recombinant gamma interferon (IFN)-gamma was found to protect the cells from infection with various isolates of human immunodeficiency virus (HIV)-1 and HIV-2, as assessed by co-cultivation with human T lymphoblastoid cells and gene amplification by polymerase chain reaction technique. Additionally, IFN-gamma induced a dose-dependent inhibition of HIV-1 and HIV-2 production in chronically infected HT29 cells. In situ hybridization studies demonstrated that IFN-treated cells were still able to synthesize viral messenger ribonucleic acid. However, the expression of the p24 product of the gag gene was markedly decreased after IFN treatment as demonstrated by radio-immunoprecipitation assay. Taken together, these data suggested that the cytokine acted at the post-translational level by inhibiting the processing of structural viral proteins. It is concluded from this study that IFN-gamma has a potent anti-HIV effect on epithelial gastrointestinal cells.

Cells, Cultured↗
PubMed1999

Cytoskeletal effects induced by pet, the serine protease enterotoxin of enteroaggregative Escherichia coli.

We have previously described enteroaggregative Escherichia coli (EAEC) strains that induce cytotoxic effects on T84 cells, ligated rat ileal loops, and human intestine in culture. Such strains secrete a 104-kDa protein termed Pet (for plasmid-encoded toxin). We have also shown previously that the Pet toxin induces rises in short-circuit current and decreases the electrical resistance in rat jejunum mounted in an Ussing chamber. The nucleotide sequence of the pet gene revealed that Pet is a member of the autotransporter class of secreted proteins. Here we show that a concentrated supernatant of E. coli HB101 harboring the minimal pet clone pCEFN1 induces temperature-, time- and dose-dependent cytopathic effects on HEp-2 cells and HT29 C1 cells in culture. The effects were characterized by release of the cellular focal contacts from the glass substratum, followed by complete rounding of the cells and detachment from the glass. Staining of the Pet-treated cells with Live/Dead viability stain revealed that >90% of rounded cells were viable. Pet-intoxicated HEp-2 and HT29 cells stained with fluorescein-labeled phalloidin revealed contraction of the cytoskeleton and loss of actin stress fibers. However, the effects of Pet were not inhibited by cytoskeleton-altering drugs, including colchicine, taxol, cytochalasin D, and phallicidin. The Pet protein induced proteolysis in zymogram gels, and preincubation with the serine protease inhibitor phenylmethylsulfonyl fluoride resulted in complete abrogation of Pet cytopathic effects. We introduced a mutation in a predicted catalytic serine residue and found that the mutant (Pet S260I) was deficient in protease activity and did not produce cytopathic effects, cytoskeletal damage, or enterotoxic effects in Ussing chambers. These data suggest that Pet is a cytoskeleton-altering toxin and that its protease activity is involved in each of the observed phenotypes.

Animals↗
PubMed1992

Effect of O6-benzylguanine on the sensitivity of human tumor xenografts to 1,3-bis(2-chloroethyl)-1-nitrosourea and on DNA interstrand cross-link formation.

We have previously shown that O6-benzylguanine can be used to deplete cells of the DNA repair protein O6-alkylguanine-DNA alkyltransferase and to enhance the sensitivity of human glioma (SF767) and colon tumor (HT29) cells to the cytotoxic effects of alkylnitrosoureas. In the present study, the combination of O6-benzylguanine and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) was evaluated in vitro to determine the number of DNA interstrand cross-links formed and in vivo to compare the therapeutic index with that of BCNU alone. The number of DNA interstrand cross-links, as measured by alkaline elution, was increased in HT29 cells treated with 10 microM O6-benzylguanine for 2 h prior to BCNU exposure compared to cells treated with BCNU only. The number of single strand breaks was not increased by prior exposure to O6-benzylguanine. To evaluate the therapeutic index, HT29 and SF767 cells were grown as xenografts in nude mice and the tumor growth rate after treatment with BCNU alone was compared with the rate after treatment with O6-benzylguanine and BCNU. Treatment was administered i.p. when tumors reached 100-200 mm3. For animals bearing HT29 xenografts that were treated with 60 mg/kg O6-benzylguanine 1 h prior to 20 mg/kg BCNU, the average time for tumor volume to increase by 200% was 25 days, compared to 10 days for animals treated with 20 mg/kg BCNU alone. For animals bearing SF767 xenografts, the tumor growth of controls was not significantly different from that of animals treated with O6-benzylguanine alone or BCNU alone up to the maximally tolerated dose (50 mg/kg). For these 3 groups, the average time for tumors to reach 300 mm3 was 9-12 days. However, when animals were treated with 80 mg/kg O6-benzylguanine 1 h prior to receiving 20 mg/kg BCNU tumor size did not increase for at least 21 days. Our studies demonstrate that the therapeutic index of BCNU can be increased when given in combination with O6-benzylguanine.

Animals↗
PubMed2006

Uranyl nitrilotriacetate, a stabilized salt of uranium, is genotoxic in nontransformed human colon cells and in the human colon adenoma cell line LT97.

Previous uranium mining in the "Wismut" region in Germany enhanced environmental distribution of heavy metals and radionuclides. Carryover effects may now lead to contamination of locally produced foods. Compounds of "Wismut" origin are probably genotoxic via their irradiating components (radon) or by interacting directly with cellular macromolecules. To assess possible hazards, we investigated the genotoxic effects of uranyl nitrilotriacetate (U-NTA) in human colon tumor cells (HT29 clone 19A), adenoma cells (LT97), and nontransformed primary colon cells. These are target cells of oral exposure to environmentally contaminated foods and represent different cellular stages during colorectal carcinogenesis. Colon cells were incubated with U-NTA. Cell survival, cytotoxicity, cellular glutathione (GSH) levels, genotoxicity, and DNA repair capacity (comet assay), as well as gene- and chromosome-specific damage combination of comet assay and fluorescence in situ hybridization [FISH], 24-color FISH) were determined. U-NTA inhibited growth of HT29 clone 19A cells (75-2000 microM, 72 h) and increased GSH (125-2000 microM, 24 h). U-NTA was genotoxic (1000 microM, 30 min) but did not inhibit the repair of DNA damage caused by hydrogen peroxide (H(2)O(2)), 4-hydroxynonenal, and 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]-pyridine. U-NTA was also genotoxic in LT97 cells and primary colon cells, where it additionally increased migration of TP53 into the comet tail. In LT97 cells, 0.5-2mM U-NTA increased chromosomal aberrations in chromosomes 5, 12, and 17, which harbor the tumor-related genes APC, KRAS, and TP53. It may be concluded that uranium compounds could increase alimentary genotoxic exposure in humans if they reach the food chain in sufficient amounts.

Adenoma↗
PubMed2004

Functional form of Caveolin-1 is necessary for the assembly of alpha-hemolysin.

The assembly of alpha-HL was shown to rapidly progress upon its interaction with Caveolin-1. Treatment of A431 cells with alpha-HL has resulted in clustering of Caveolin-1 at cell-cell contacts. Consistent with this observation, alpha-HL mutants devoid of assembly property have not induced the clustering of Caveolin-1. While cholesterol depletion of A431 cells completely arrests the assembly of alpha-HL, chelation of membrane cholesterol results in its retarded assembly. Interestingly, HT29 cells, with low Caveolin-1 levels, are resistant to alpha-HL attack. Clustering of Caveolin-1, as seen in case of A431 cells, was readily observed in case of HT29 cells transfected with Caveolin-1 construct, thus overexpressing the full length Caveolin-1, upon alpha-HL treatment. A model was constructed to visualize the interactions between alpha-HL and Caveolin-1 which suggests that facile penetration of alpha-HL's beta-barrel might occur through protein-protein interactions with the surrounding 7 alpha-helices of Caveolin-1.

Amino Acid Motifs↗
PubMed2002

Homocamptothecin-daunorubicin association overcomes multidrug-resistance in breast cancer MCF7 cells.

The multidrug-resistance (MDR) status of a novel camptothecin analogue, homocamptothecin (hCPT), was investigated in human colon adenocarcinoma HT29 cells, myelogenous leukemia K562 cells and breast carcinoma MCF7 cells. The cytotoxicity of hCPT was not sensitive to the MDR status in K562 cell lines. However, its cytotoxicity was altered by MRP1, but not Pgp, in naturally MRP1-expressing HT29 cells, and etoposide- and doxorubicin-resistant MCF7/VP and MCF7/DOX cells, respectively. These cells were sensitized to hCPT in presence of MK571, probenecid but not verapamil. These results led to consider hCPT as a substrate for MRP1 and a potential modulator of MRP1 activity. The relationship between the cytotoxic effect of anthracyclines and their nuclear localization had been previously demonstrated. We show that MRPI mediated the daunorubicin (DNR) efflux in MCF7/VP and MCF7/DOX cells. The combination of sub-toxic doses of hCPT with DNR resulted in the potentiation of DNR activity, well-correlated with an increase in its nuclear accumulation in MCF7/VP cells. Simultaneous pattern was shown to provide higher cytotoxic response than sequential one. In agreement, hCPT increased also the DNR nuclear accumulation in low MRP1-expressing MCF7/DOX cells. However, the enhancement of cytotoxicity in the DNR-hCPT combination was poorly correlated with the nuclear concentration of DNR in MCF7/DOX cells. In addition to the increase in DNR accumulation, the potentiation of DNR activity by hCPT in MCF7/DOX cells implied a synergistic mechanism between both drugs. These data suggest that the present topoisomerase I/II inhibitors combination may be of clinical interest to overcome MDR phenotype in DNR-treated breast cancer patients.

Adenocarcinoma↗
PubMed2000

Stimulation of colorectal cancer cell line growth by ET-1 and its inhibition by ET(A) antagonists.

BACKGROUND: The vasoactive peptide endothelin 1 (ET-1) acts via two receptors, endothelin receptors A (ET(A)) and B (ET(B)). ET-1 is overexpressed by human cancers in vivo and in vitro and may be mitogenic for cancer cells. METHOD: To elucidate if ET-1 is a growth regulator the following were investigated in human colorectal cancer cell lines (LIM1215 and HT29): ET-1 production by ELISA; ET receptor expression using radioligand autoradiographic techniques; and responsiveness to ET-1, and to ET(A) and ET(B) antagonism by growth measurements. RESULTS: ET-1 was produced by LIM1215 and HT29 cells (21.3 and 41.7 fmol/ml/10(6) cells (24 hours); 22.6 and 71.7 fmol/ml/10(6) cells (48 hours), respectively). ET(A) and ET(B) receptors were expressed by both cell lines. Addition of ET-1 resulted in a dose dependent increase in cell numbers which was significant at 10(-8)-10(-9) M for LIM1215, with the greatest increase at 10(-8) M (32.7% and 28.4% increase above controls at 48 hours and 72 hours; p<0.05) and at 10(-8)-10(-9) M for HT29, with the greatest increase at 10(-9) M (13.4% and 15.7% increase above controls at 48 hours and 72 hours; p<0.05). ET(A) antagonists BQ123 and BQ610, but not the ET(B) antagonist BQ788, inhibited ET-1 induced proliferation of both LIM1215 and HT29 (p<0.05). CONCLUSION: ET-1 can stimulate the proliferation of colorectal cancer cell lines via the ET(A), but not the ET(B), receptor.

Cell Division↗