Antiproliferative activity of interferon alpha and retinoic acid in SiHa carcinoma cells: the role of cell adhesion

SHP-2 phosphatase promotes cervical cancer cell proliferation through inhibiting interferon-β production

AIM

The aim of this study was to explore the effect of Src-homology-2-domain-containing protein, tyrosine phosphatase 2 (SHP-2) on the proliferation of cervical cancer cells.

MATERIAL AND METHODS

A total of 45 patients with cervical cancer (stage I-III), 32 with cervical intraepithelial neoplasia and 20 healthy subjects were consecutively recruited. The levels of SHP-2 and interferon (IFN)-β expression in cervical tissues were characterized by immunohistochemistry and statistically analyzed by logistic regression. Following knockdown of SHP-2 expression by a siRNA or pre-treatment with a specific peptide, the effect of SHP-2 expression in THP-1 cells on the growth and survival of SiHa cells and on IFN-β production was determined by co-culture assays, 3-(4,5)-dimethylthiazol (-z-y 1)-3,5-diphenyltetrazolium bromide, and enzyme immunosorbent assay.

RESULTS

The levels of SHP-2 expression in cervical cancer tissues were significantly higher than that in cervical intraepithelial neoplasia and uterine myoma tissues (P<0.05, respectively), and negatively correlated with the levels of IFN-β expression in these tissues (R=-0.582, P<0.05). Knockdown of SHP-2 expression with SHP-2 siRNA or treatment with the SHP-2-specific blocking peptide in THP-1 cells significantly increased the production of IFN-β (P<0.05, respectively) and inhibited the proliferation of SiHa cells in a co-culture system of THP-1 and SiHa cells (P<0.05, respectively).

CONCLUSIONS

SHP-2 phosphatase promotes cervical cancer cell proliferation through inhibiting IFN-β production.

Effects of pegylated interferon α2b on metastasis of hepatocellular carcinoma

OBJECTIVE

Interferon (IFN) has an anti-tumor activity in hepatocellular carcinoma (HCC) via anti-angiogenesis and induction of apoptosis. We have previously reported anti-metastatic effects of IFN combined chemotherapy on the outcome of HCC patients. The aim of this study was to investigate anti-metastatic effects of IFN.

METHODS

In vitro, pegylated interferon α2b (PEG-IFN-α2b) was administered to mouse MH134 cells (mouse HCC cell line, MH134), and anti-implantation effects were examined by evaluating the inhibition of cell invasion and cell proliferation. Expressions of vascular endothelial growth factor (VEGF) mRNA were also measured. In vivo, PEG-IFN-α2b was subcutaneously administered into MH134 cells and tumor growth was evaluated. In distant metastasis models, PEG-IFN-α2b was subcutaneously administered and MH134 cells were injected into the spleen. The number of liver metastases and microvessel densities (MVD) were counted.

RESULTS

In vitro, the proliferation of MH134 cells was significantly suppressed by PEG-IFN-α2b dose-dependently. MH134 cells added with PEG-IFN-α2b exhibited significantly lower levels of invasion potential. In vivo, tumor size in mice treated with PEG-IFN-α2b significantly suppressed compared with control mice (mean 0.5 versus 5.0 cm, in diameter, P < 0.05) and also decreased number of liver metastases (19.3 versus 6.0, P < 0.05). Moreover, PEG-IFN-α2b significantly suppressed angiogenesis compared with the control.

CONCLUSION

PEG-IFN-α2b in itself had remarkable anti-metastatic effects via inhibition of angiogenesis and cell adhesions.

Inhibitory effects of retinoic acid on invasiveness of human thyroid carcinoma cell lines in vitro

BACKGROUND

The prognosis of patients with metastasized thyroid carcinoma is not optimistic, necessitating the search for new treatment options.

AIM

Beneficial effects of retinoic acid (RA) have been suggested in thyroid cancer differentiation and the present study was performed to investigate the anti-metastatic potential of RA in respect of important determinants of metastatic behavior in thyroid carcinoma, focusing on the role of invasion-associated proteins.

MATERIALS AND METHODS

Differentiated thyroid carcinoma cell lines FTC- 133 and XTC.UC1, and anaplastic thyroid cancer cell lines C643 and HTH74 were studied. All cell lines were cultured with alltrans- RA (ATRA) or the solvent ethanol. Invasion and adhesion potency in vitro was studied by transwell experiment and short-term adhesion assay. The involvement of invasion-associated proteins, urokinase type plasminogen activator (uPA), uPA receptor (uPAR), matrix metalloproteinase-2 (MMP-2) and E-cadherin, were investigated by semi-quantitative RT-PCR and Western blot.

RESULTS

In vitro invasion assay revealed that ATRA treatment could reduce the invasive potency in all the thyroid cancer cell lines, with the most significant effect in anaplastic cancer cells. Short-term adhesion assay suggested that ATRA increases cancer cell adhesion to extracellular matrix (ECM) in C643, HTH74 and XTC.UC1, probably through a transcriptional and translational regulation of some attachment molecules. RT-PCR andWestern blot both revealed diminished expression of uPAR in all four carcinoma cell lines. In C643 and HTH74 cell lines, the expression of uPA was reduced and the expression of E-cadherin was increased, whereas the MMP-2 expression was not significantly down-regulated in ATRA-treated group. In ATRA-treated FTC-133 and XTC.UC1 cell lines, MMP-2 expression was decreased, but no significant changes in uPA and E-cadherin expression were observed.

CONCLUSIONS

The present study demonstrates the influence of ATRA on both important determinants of metastatic behavior ("de-adhesion" and proteolysis) in thyroid carcinoma cell lines, especially in anaplastic cancer cells. These findings may add to the explanations for beneficial effects of RA in the treatment of metastatic thyroid carcinomas.

Mofarotene-induced inhibition of melanoma cell motility by increasing vinculin-containing focal contacts

Tumour cell motility, which is dependent on the organization of the cytoskeleton, is considered to play an important role in the spread of malignant melanoma. Therefore, retinoids, which are modulators of cytoskeletal organization, may affect the motile activity of melanoma cells. In this study, the effects of the arotinoid mofarotene on single cell motility and vinculin organization of the highly metastatic melanoma cell line K-1735-M2 were determined. Melanoma cells were cultivated in a temperature- and CO2-controlled microincubator, which was located on the microscope stage. Cell movements were evaluated quantitatively from time-lapse video recordings using an IBAS image analysis system. Vinculin distribution was evaluated using confocal laser scanning microscopy and a specially developed computerized image analysing program. In addition, melanoma cell invasion was tested on the embryonic chick heart model. Although 10 microM mofarotene did not reduce the translocative movements of melanoma cells, it significantly inhibited stationary motility, including fast plasma membrane movements and changes in shape. Mofarotene also showed a pronounced effect on the organization of vinculin-containing cell-substratum adhesion plaques. In retinoid-treated cells, the numbers of vinculin plaques per cell, and particularly those in the marginal areas of the cells, were significantly increased compared with untreated controls. Furthermore, the compound reduced the invasiveness of melanoma cells in a three-dimensional tissue culture model. In conclusion, our data demonstrate that mofarotene, an already almost forgotten synthetic retinoid, shows interesting effects on melanoma cells, which may be relevant for a slowdown of tumour spread.

Tissue transglutaminase mediates activation of RhoA and MAP kinase pathways during retinoic acid-induced neuronal differentiation of SH-SY5Y cells

All-trans-retinoic acid (RA) plays a crucial role in survival and differentiation of neurons. For elucidating signaling mechanisms involved in RA-induced neuronal differentiation, we have selected SH-SY5Y cells, which are an established in vitro cell model for studying RA signaling. Here we report that RA-induced neuronal differentiation of SH-SY5Y cells is coupled with increased expression/activation of TGase and in vivo transamidation and activation of RhoA. In addition, RA promotes formation of stress fibers and focal adhesion complexes, and activation of ERK1/2, JNK1, and p38alpha/beta/gamma MAP kinases. Using C-3 exoenzyme (RhoA inhibitor) or monodansylcadaverine (TGase inhibitor), we show that transamidated RhoA regulates cytoskeletal rearrangement and activation of ERK1/2 and p38gamma MAP kinases. Further, by using stable SH-SY5Y cell lines (overexpressing wild-type, C277S mutant, and antisense TGase), we demonstrate that transglutaminase activity is required for activation of RhoA, ERK1/2, JNK1, and p38gamma MAP kinases. Activated MAP kinases differentially regulate RA-induced neurite outgrowth and neuronal marker expression. The results of our studies suggest a novel mechanism of RA signaling, which involves activation of TGase and transamidation of RhoA. RA-induced activation of TGase is proposed to induce multiple signaling pathways that regulate neuronal differentiation.

Combined stimulation with interferon alpha and retinoic acid synergistically inhibits proliferation of the glioblastoma cell line GB12

Since malignant glioma displays moderate resistance to conventional therapy, a new treatment modality is needed to improve the outcome of patients with these tumors. In this study, we examined whether combination stimulation with interferon alpha (IFN-alpha) and retinoic acid (RA) affected proliferation of the glioblastoma cell line GB 12 in vitro. Stimulation with IFN-alpha alone inhibited the GB 12 cell proliferation in a dose/time-dependent fashion, as assessed by WST-1 assay and uptake of 3H-thymidine, while RA limited it only slightly. The anti-proliferative action of IFN-alpha against glioblastoma cells was enhanced by the addition of RA. The IFN-alpha/RA combination also induced apoptosis in a substantial portion of the cells, compared with either reagent alone. Bcl-2 family proteins, regulating apoptosis, were altered by these stimuli: Bcl-2 was down-regulated, while Bax-alpha was up-regulated, especially by the combination. These findings suggest that the IFN-alpha/RA combination would synergistically affect glioblastoma cell growth, probably through apoptosis induction as well as a decreased cellular DNA synthesis.

The E-cadherin cell-cell adhesion complex and lung cancer invasion, metastasis, and prognosis

BACKGROUND

Lung cancer is the most common cause of cancer deaths in the western world. Progress in treatment results has been limited, and the prognosis is poor with a 5-year survival less than 15%. Based on new developments in molecular biology, our knowledge about lung carcinogenesis and mechanisms for invasion and metastasis has expanded and may in the future lead to more specific targeted therapies and better prognosis. The E-cadherin-catenin complex is critical for intercellular adhesiveness and maintenance of normal and malignant tissue architecture. Reduced expression of this complex in malignant disease is associated with tumour invasion, metastasis, and unfavorable prognosis.

METHODS

This review is based on search in the Medline database from 1991 to 2001. We have reviewed the relevance of the E-cadherin-catenin adhesion complex in malignancy in general and lung cancer in particular. Furthermore, its role as target for specific therapy is discussed.

RESULTS

Available data indicate that alterations of proteins involved in the E-cadherin-catenin complex are early incidents in cancer development. Reduced or altered expression of one or more of the components in this complex is associated with extended invasive and progressive behavior of cancer cells. Consistently, the E-cadherin-catenin complex appears to be increasingly delicate with regard to cancer prognosis. beta-Catenin, one of the components of the adhesion complex, also plays a significant role in cell signal transduction, gene activation, apoptosis inhibition, and increased cellular proliferation and migration.

CONCLUSION

Inactivation of the E-cadherin-catenin adhesion complex, induced by genetic and epigenetic events, plays a significant role in multistage carcinogenesis, and seems to be associated with dedifferentiation, local invasion, regional metastasis, and reduced survival in lung cancer.

Role of transglutaminase II in retinoic acid-induced activation of RhoA-associated kinase-2

Transamidation is a post-translational modification of proteins mediated by tissue transglutaminase II (TGase), a GTP-binding protein, participating in signal transduction pathways as a non-conventional G-protein. Retinoic acid (RA), which is known to have a role in cell differentiation, is a potent activator of TGASE: The activation of TGase results in increased transamidation of RhoA, which is inhibited by monodansylcadaverine (MDC; an inhibitor of transglutaminase activity) and TGaseM (a TGase mutant lacking transglutaminase activity). Transamidated RhoA functions as a constitutively active G-protein, showing increased binding to its downstream target, RhoA-associated kinase-2 (ROCK-2). Upon binding to RhoA, ROCK-2 becomes autophosphorylated and demonstrates stimulated kinase activity. The RA-stimulated interaction between RhoA and ROCK-2 is blocked by MDC and TGaseM, indicating a role for transglutaminase activity in the interaction. Biochemical effects of TGase activation, coupled with the formation of stress fibers and focal adhesion complexes, are proposed to have a significant role in cell differentiation.

Interferon-beta induces S phase slowing via up-regulated expression of PML in squamous carcinoma cells

Type I Interferon (IFN) and all-trans retinoic acid (RA) inhibit cell proliferation of squamous carcinoma cell lines (SCC). Examinations of growth-affected cell populations show that SCC lines ME-180 and SiHa treated with IFN-beta undergo a specific slower progression through the S phase that seems to trigger cellular death. In combination treatment RA potentiates IFN-beta effect in SCC ME-180 but not in SiHa cell line, partially resistant to RA antiproliferative action. RA added as single agent affects cell proliferation differently by inducing a slight G1 accumulation. The IFN-beta-induced S phase lengthening parallels the increased expression of PML, a nuclear phosphoprotein specifically up-regulated at transcriptional level by IFN, whose overexpression induces cell growth inhibition and tumor suppression. We report that PML up-regulation may account for the alteration of cell cycle progression induced by IFN-beta in SCC by infecting cells with PML-PINCO recombinant retrovirus carrying the PML-3 cDNA under the control of the 5' LTR. In fact PML overexpression reproduces the IFN-beta-induced S phase lengthening. These findings provide important insight into the mechanism of tumor suppressing function of PML and could allow PML to be included in the pathways responsible for IFN-induced cell growth suppression.

Adenosine- and 2-chloro-adenosine-induced cytopathic effects on myoblastic cells and myotubes: involvement of different intracellular mechanisms

We recently suggested that, in muscular dystrophies, the excessive accumulation of adenosine as a result of an altered purine metabolism may contribute to progressive functional deterioration and muscle cell death. To verify this hypothesis, we have taken advantage of C2C12 myoblastic cells, which can be differentiated in vitro into multinucleated cells (myotubes). Exposure of both proliferating myoblasts and differentiated myotubes to adenosine or its metabolically-stable analog, 2-chloro-adenosine, resulted in apoptotic cell death and myotube disruption. Cytotoxicity by either nucleoside did not depend upon extracellular adenosine receptors, but, at least in part, by entry into cells via the membrane nitro-benzyl-thio-inosine-sensitive transporter. The adenosine kinase inhibitor, 5-iodotubercidin, prevented 2-chloro-adenosine-induced (but not adenosine-induced) effects, suggesting that an intracellular phosphorylation/activation reaction plays a key role in 2-chloro-adenosine-mediated cytotoxicity. Conversely, adenosine cytotoxicity was aggravated by the addition of homocysteine, suggesting that adenosine effects may be due to the accumulation of S-adenosyl-homocysteine, which blocks intracellular methylation-dependent reactions. Both nucleosides markedly disrupted the myotube structure via an effect on the actin cytoskeleton; however, also for myotubes, there were marked differences in the morphological alterations induced by these two nucleosides. These results show that adenosine and 2-chloro-adenosine induce apoptosis of myogenic cells via completely different metabolic pathways, and are consistent with the hypothesis that adenosine accumulation in dystrophic muscles may represent a novel pathogenetic pathway in muscle diseases.

E-cadherin-catenin cell-cell adhesion complex and human cancer

BACKGROUND

The E-cadherin-catenin complex plays a crucial role in epithelial cell-cell adhesion and in the maintenance of tissue architecture. Perturbation in the expression or function of this complex results in loss of intercellular adhesion, with possible consequent cell transformation and tumour progression. Recently, much progress has been made in understanding the interaction between the different components of this protein complex and how this cell-cell adhesion complex is modulated in cancer cells.

METHODS

This is an update of the role of the E-cadherin-catenin complex in human cancers. It emphasizes new features and the possible role of the complex in clinical practice, discussed in the light of 165 references obtained from the Medline database from 1995 to 1999.

RESULTS

More evidence is now appearing to suggest that disturbance in protein-protein interaction in the E-cadherin-catenin adhesion complex is one of the main events in the early and late steps of cancer development. An inverse correlation is found between expression of the E-cadherin-catenin complex and the invasive behaviour of tumour cells. Therefore, E-cadherin-catenin may become a significant prognostic marker for tumour behaviour. Besides its role in establishing tight cell-cell adhesion, beta- catenin plays a major role in cell signalling and promotion of neoplastic growth. This suggests its dual role as a tumour suppressor and as an oncogene in human cancers.

CONCLUSION

Recent developments show that the E-cadherin-catenin complex is more than a 'sticky molecular complex'. Further studies may yield greater insight into the early molecular interactions critical to the initiation and progression of tumours. This should aid the development of novel strategies for both prevention and treatment of cancer.

Up-regulation of E-cadherin and I-catenin in human hepatocellular carcinoma cell lines by sodium butyrate and interferon-alpha

Human E-cadherin is a homophilic cell adhesion molecule and its expression is well preserved in normal human hepatocytes; a decrease in its expression has been observed in poorly differentiated hepatocellular carcinoma cells. We examined the alteration of E-cadherin and catenin expressions caused by differentiation inducers in human hepatocellular carcinoma cells. Hepatocellular carcinoma cell lines, HCC-T and HCC-M, were cultured with all-trans retinoic acid (ATRA), dexamethasone (DEX), sodium butyrate, and interferon-alpha. E-cadherin expression was only up-regulated by butyrate and interferon-alpha (IFN-alpha) in both cell lines, studied by means of fluorescence immunostaining and flow cytometry. The localization of E-cadherin staining was shown at their cell membrane. According to the increase in E-cadherin expression, beta-catenin expression appeared at the cell membrane of both cell lines when treated with butyrate and IFN-alpha. Such an appearance was not observed when cells were treated with ATRA and DEX. Western blotting showed that alpha- and y-catenin expression was not changed, while only the expression of beta-catenin increased. Beta-catenin oncogenic activation as a result of amino acid substitutions or interstitial deletions within or including parts of exon 3, which has been demonstrated recently, was not detected in these cell lines by direct deoxyribonucleic acid sequencing. These results suggest that the expression and interaction between E-cadherin and wild-type beta-catenin are potentially modulated by butyrate and IFN-alpha, and that these two agents are potent inhibitors of hepatocellular carcinoma cell invasion and metastasis.

Adenosine A3 Receptors and Viability of Astrocytes

We investigated the role of the A3 adenosine receptor in cells of the astroglial lineage (both rat primary astrocytes and human astrocytoma ADF cells) by means of the selective A3 agonists N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) and CI-IB-MECA, and by utilizing the selective A3 receptor antagonist MRS1191. Exposure of ADF cells to μM concentrations of either agonist resulted in reduction of cell number, likely due to cell death. In both rat astrocytes and human astrocytoma cells, at concentrations 2-3 orders of magnitude lower (which were not associated with cytotoxicity), these same agonists induced a marked reorganization of the cytoskeleton, with appearance of stress fibers and numerous cell protrusions. Functionally, these morphological changes were associated with cell protection, as demonstrated by a significant reduction of spontaneous apoptosis in A3 agonist-treated cells. To confirm a role for the A3 receptor in this effect, MRS1191 completely counteracted CI-IB-MECA-induced reduction of spontaneous apoptosis. In ADF cells, A3 agonists also induced changes in the intracellular distribution of the anti-apoptotic protein Bcl-XL, which became localized in cell protrusions. Also, this effect was specifically antagonized by MRS1191. These dual actions of A3 agonists in vitro may have important in vivo implications. For example, a robust and acute activation of the A3 receptor following massive adenosine release during ischemia may contribute to brain cell death; conversely, a subthreshold activation of this receptor prior to ischemia may trigger protective mechanisms (i.e., induction of stress fibers and of a Bcl-XL-dependent reorganization of cytoskeleton) making the brain more resistant to subsequent insults ("ischemic tolerance").