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Tenascin-C signaling through induction of 14-3-3 tau.

Martin D, Brown-Luedi M, Chiquet-Ehrismann R - J. Cell Biol. (2003)

Bottom Line: We found elevated levels of 14-3-3 tau transcripts and protein in cells grown on tenascin-C.Furthermore, the growth rate on tenascin-C was increased compared with the parental cells.Therefore, we postulate that tenascin-C promotes the growth of tumor cells by causing an increase in the expression of 14-3-3 tau, which in turn has a positive effect on tumor cell adhesion and growth.

View Article: PubMed Central - PubMed

Affiliation: Friedrich Miescher Institute, Novartis Forschungsstiftung, CH-4002 Basel, Switzerland.

ABSTRACT
We searched by a cDNA subtraction screen for differentially expressed transcripts in MCF-7 mammary carcinoma cells grown on tenascin-C versus fibronectin. On tenascin-C, cells had irregular shapes with many processes, whereas on fibronectin they were flat with a cobble stone-like appearance. We found elevated levels of 14-3-3 tau transcripts and protein in cells grown on tenascin-C. To investigate the consequences of an increased level of this phospho-serine/threonine-binding adaptor protein, we transfected MCF-7 cells with a construct encoding full-length 14-3-3 tau protein and selected clones with the highest expression levels. The morphology of these cells on tenascin-C was flat, resembling that of cells on fibronectin. This was reflected by a similar pattern of F-actin staining on either substratum. Furthermore, the growth rate on tenascin-C was increased compared with the parental cells. After transient transfection of HT1080 fibrosarcoma and T98G glioblastoma cells with 14-3-3 tau, only the 14-3-3 tau-expressing cells were able to adhere and survive on tenascin-C, whereas all cells adhered well on fibronectin. Therefore, we postulate that tenascin-C promotes the growth of tumor cells by causing an increase in the expression of 14-3-3 tau, which in turn has a positive effect on tumor cell adhesion and growth.

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DNA replication in cells cultured on fibronectin versus tenascin-C. 3H-thymidine incorporation was measured in MCF-7 cells and clones 2 and 5 cultured in medium with 0.1% FCS on fibronectin-coated versus tenascin-C–coated wells. In MCF-7 cells, DNA replication was reduced by >60% on tenascin-C compared with fibronectin, whereas the difference for clones 2 and 5 was greatly diminished.
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fig5: DNA replication in cells cultured on fibronectin versus tenascin-C. 3H-thymidine incorporation was measured in MCF-7 cells and clones 2 and 5 cultured in medium with 0.1% FCS on fibronectin-coated versus tenascin-C–coated wells. In MCF-7 cells, DNA replication was reduced by >60% on tenascin-C compared with fibronectin, whereas the difference for clones 2 and 5 was greatly diminished.

Mentions: We next tested the effect of the overexpression of 14-3-3 tau on cell growth. We plated equal numbers of cells on fibronectin versus tenascin-C substrates in complete medium and cultured the parental versus the 14-3-3–transfected clones 2 and 5 for 3 d. After 3 d in culture, the MCF-7 cells reached higher densities on fibronectin than on tenascin-C, whereas no distinction could be made for clone 2 or 5, respectively (unpublished data). The lower cell number of the parental MCF-7 cells on a tenascin-C substratum coincided with a reduced level of DNA replication on a tenascin-C substrate in comparison to fibronectin as measured by 3H-thymidine incorporation (Fig. 5). The 3H-thymidine incorporation by the 14-3-3 tau–overexpressing clones 2 and 5 was recovered on tenascin-C and reached values almost as high as on fibronectin (Fig. 5). A possible mechanism is that cell cycle progression is stimulated by an interaction of 14-3-3 with phosphorylated p27Kip1 and by retaining this cell cycle inhibitor in the cytoplasm (Fujita et al., 2002). Alternatively, stimulation of cell growth by 14-3-3 could be indirect by its known inhibitory action on apoptosis (Xing et al., 2000; Masters and Fu, 2001). To test whether cells on tenascin-C were protected from apoptosis by overexpression of 14-3-3 tau, we plated the parental MCF-7 cells and clones 2 and 5 on tenascin-C– and fibronectin-coated wells, respectively, and analyzed the number of apoptotic cells under both conditions. However, not even the parental MCF-7 cells showed increased apoptosis on tenascin-C compared with the cells plated on fibronectin. Reduction of the serum level in the medium to 1% lead to a concomitant increase in apoptotic cells on both substrates. Therefore, the hypothesis that 14-3-3 tau could protect MCF-7 cells from apoptosis cannot be the reason for the observed increase in growth.


Tenascin-C signaling through induction of 14-3-3 tau.

Martin D, Brown-Luedi M, Chiquet-Ehrismann R - J. Cell Biol. (2003)

DNA replication in cells cultured on fibronectin versus tenascin-C. 3H-thymidine incorporation was measured in MCF-7 cells and clones 2 and 5 cultured in medium with 0.1% FCS on fibronectin-coated versus tenascin-C–coated wells. In MCF-7 cells, DNA replication was reduced by >60% on tenascin-C compared with fibronectin, whereas the difference for clones 2 and 5 was greatly diminished.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172641&req=5

fig5: DNA replication in cells cultured on fibronectin versus tenascin-C. 3H-thymidine incorporation was measured in MCF-7 cells and clones 2 and 5 cultured in medium with 0.1% FCS on fibronectin-coated versus tenascin-C–coated wells. In MCF-7 cells, DNA replication was reduced by >60% on tenascin-C compared with fibronectin, whereas the difference for clones 2 and 5 was greatly diminished.
Mentions: We next tested the effect of the overexpression of 14-3-3 tau on cell growth. We plated equal numbers of cells on fibronectin versus tenascin-C substrates in complete medium and cultured the parental versus the 14-3-3–transfected clones 2 and 5 for 3 d. After 3 d in culture, the MCF-7 cells reached higher densities on fibronectin than on tenascin-C, whereas no distinction could be made for clone 2 or 5, respectively (unpublished data). The lower cell number of the parental MCF-7 cells on a tenascin-C substratum coincided with a reduced level of DNA replication on a tenascin-C substrate in comparison to fibronectin as measured by 3H-thymidine incorporation (Fig. 5). The 3H-thymidine incorporation by the 14-3-3 tau–overexpressing clones 2 and 5 was recovered on tenascin-C and reached values almost as high as on fibronectin (Fig. 5). A possible mechanism is that cell cycle progression is stimulated by an interaction of 14-3-3 with phosphorylated p27Kip1 and by retaining this cell cycle inhibitor in the cytoplasm (Fujita et al., 2002). Alternatively, stimulation of cell growth by 14-3-3 could be indirect by its known inhibitory action on apoptosis (Xing et al., 2000; Masters and Fu, 2001). To test whether cells on tenascin-C were protected from apoptosis by overexpression of 14-3-3 tau, we plated the parental MCF-7 cells and clones 2 and 5 on tenascin-C– and fibronectin-coated wells, respectively, and analyzed the number of apoptotic cells under both conditions. However, not even the parental MCF-7 cells showed increased apoptosis on tenascin-C compared with the cells plated on fibronectin. Reduction of the serum level in the medium to 1% lead to a concomitant increase in apoptotic cells on both substrates. Therefore, the hypothesis that 14-3-3 tau could protect MCF-7 cells from apoptosis cannot be the reason for the observed increase in growth.

Bottom Line: We found elevated levels of 14-3-3 tau transcripts and protein in cells grown on tenascin-C.Furthermore, the growth rate on tenascin-C was increased compared with the parental cells.Therefore, we postulate that tenascin-C promotes the growth of tumor cells by causing an increase in the expression of 14-3-3 tau, which in turn has a positive effect on tumor cell adhesion and growth.

View Article: PubMed Central - PubMed

Affiliation: Friedrich Miescher Institute, Novartis Forschungsstiftung, CH-4002 Basel, Switzerland.

ABSTRACT
We searched by a cDNA subtraction screen for differentially expressed transcripts in MCF-7 mammary carcinoma cells grown on tenascin-C versus fibronectin. On tenascin-C, cells had irregular shapes with many processes, whereas on fibronectin they were flat with a cobble stone-like appearance. We found elevated levels of 14-3-3 tau transcripts and protein in cells grown on tenascin-C. To investigate the consequences of an increased level of this phospho-serine/threonine-binding adaptor protein, we transfected MCF-7 cells with a construct encoding full-length 14-3-3 tau protein and selected clones with the highest expression levels. The morphology of these cells on tenascin-C was flat, resembling that of cells on fibronectin. This was reflected by a similar pattern of F-actin staining on either substratum. Furthermore, the growth rate on tenascin-C was increased compared with the parental cells. After transient transfection of HT1080 fibrosarcoma and T98G glioblastoma cells with 14-3-3 tau, only the 14-3-3 tau-expressing cells were able to adhere and survive on tenascin-C, whereas all cells adhered well on fibronectin. Therefore, we postulate that tenascin-C promotes the growth of tumor cells by causing an increase in the expression of 14-3-3 tau, which in turn has a positive effect on tumor cell adhesion and growth.

Show MeSH
Related in: MedlinePlus