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Deregulation of the CEACAM expression pattern causes undifferentiated cell growth in human lung adenocarcinoma cells.

Singer BB, Scheffrahn I, Kammerer R, Suttorp N, Ergun S, Slevogt H - PLoS ONE (2010)

Bottom Line: Interestingly, CEACAM1-L, but not CEACAM1-S, negatively regulates proliferation via its ITIM domain, while in proliferating cells no CEACAM expression is detectable.Furthermore, we show for the first time that CEACAM6 acts as an inducer of cellular proliferation in A549 cells, likely by interfering with the contact-inhibiting signal triggered by CEACAM1-4L, leading to undifferentiated anchorage-independent cell growth.Taken together, our data suggest that post-confluent contact inhibition is established and maintained by CEACAM1-4L, but disturbances of CEACAM1 signalling by CEACAM1-4S and other CEACAMs lead to undifferentiated cell growth and malignant transformation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Anatomy, University Hospital Essen, Essen, Germany. BBSinger@gmx.de

ABSTRACT
CEACAM1, CEA/CEACAM5, and CEACAM6 are cell adhesion molecules (CAMs) of the carcinoembryonic antigen (CEA) family that have been shown to be deregulated in lung cancer and in up to 50% of all human cancers. However, little is known about the functional impact of these molecules on undifferentiated cell growth and tumor progression. Here we demonstrate that cell surface expression of CEACAM1 on confluent A549 human lung adenocarcinoma cells plays a critical role in differentiated, contact-inhibited cell growth. Interestingly, CEACAM1-L, but not CEACAM1-S, negatively regulates proliferation via its ITIM domain, while in proliferating cells no CEACAM expression is detectable. Furthermore, we show for the first time that CEACAM6 acts as an inducer of cellular proliferation in A549 cells, likely by interfering with the contact-inhibiting signal triggered by CEACAM1-4L, leading to undifferentiated anchorage-independent cell growth. We also found that A549 cells expressed significant amounts of non-membrane anchored variants of CEACAM5 and CEACAM6, representing a putative source for the increased CEACAM5/6 serum levels frequently found in lung cancer patients. Taken together, our data suggest that post-confluent contact inhibition is established and maintained by CEACAM1-4L, but disturbances of CEACAM1 signalling by CEACAM1-4S and other CEACAMs lead to undifferentiated cell growth and malignant transformation.

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Representative images of different A549 cell clones demonstrating their morphological heterogeneity by phase contrast imaging.Subpopulation A549-NT grown exponentially (a), to tight confluence forming cell-contact inhibited monolayers (b). Tight confluent subpopulation of A549-T (c) piled up on the monolayer revealing the ability to survive and proliferate independently of cell-matrix anchorage, leading to detached spheroidal colonies on top of the monolayer. (d) Spheroidal A549-T colonies seeded into fresh culture vessels attached and grew as monolayers. Bar, 50 µm.
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pone-0008747-g001: Representative images of different A549 cell clones demonstrating their morphological heterogeneity by phase contrast imaging.Subpopulation A549-NT grown exponentially (a), to tight confluence forming cell-contact inhibited monolayers (b). Tight confluent subpopulation of A549-T (c) piled up on the monolayer revealing the ability to survive and proliferate independently of cell-matrix anchorage, leading to detached spheroidal colonies on top of the monolayer. (d) Spheroidal A549-T colonies seeded into fresh culture vessels attached and grew as monolayers. Bar, 50 µm.

Mentions: Phase-contrast microscopy revealed that under standard culture conditions sub-confluent A549-NT and -T occurred as scattered colonies of associated cells (Figure 1A). However, confluent A549-NT cells appeared as cobblestone monolayer, characteristic of epithelial cell growth, consistent of closely associated cells with a typical polygonal, epithelial-like morphology indicating a stringent contact inhibition of cell growth (Figure 1B). In addition, this subpopulation formed tight cell-cell contacts leading to a significant prolongation of the trypsin treatment necessary for harvesting if compared with the time needed to harvest exponential growing A549-NT cells. The A549-T subpopulation also grew as a normal epithelial monolayer. However, in contrast to the A549-NT, some cells piled up on each other showing anchorage independence. These cell aggregates were found mainly at the top of the monolayer together with suspended cells (Figure 1C). Over time, the spheroid aggregates detached, floated unbound on top of the monolayer and formed proliferating colonies containing approximately 4–400 cells. After seeding A549-T spheroids into new culture vessels, most of the cells attached within a few hours (Figure 1D), grew to a confluent monolayer and again generated detached spheroids of growing cells (data not shown). A549-NT cells had a doubling time of approximately 24 hours and A549-T cells of approximately 20 hours as determined by cell cycle determinations (data not shown).


Deregulation of the CEACAM expression pattern causes undifferentiated cell growth in human lung adenocarcinoma cells.

Singer BB, Scheffrahn I, Kammerer R, Suttorp N, Ergun S, Slevogt H - PLoS ONE (2010)

Representative images of different A549 cell clones demonstrating their morphological heterogeneity by phase contrast imaging.Subpopulation A549-NT grown exponentially (a), to tight confluence forming cell-contact inhibited monolayers (b). Tight confluent subpopulation of A549-T (c) piled up on the monolayer revealing the ability to survive and proliferate independently of cell-matrix anchorage, leading to detached spheroidal colonies on top of the monolayer. (d) Spheroidal A549-T colonies seeded into fresh culture vessels attached and grew as monolayers. Bar, 50 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2807459&req=5

pone-0008747-g001: Representative images of different A549 cell clones demonstrating their morphological heterogeneity by phase contrast imaging.Subpopulation A549-NT grown exponentially (a), to tight confluence forming cell-contact inhibited monolayers (b). Tight confluent subpopulation of A549-T (c) piled up on the monolayer revealing the ability to survive and proliferate independently of cell-matrix anchorage, leading to detached spheroidal colonies on top of the monolayer. (d) Spheroidal A549-T colonies seeded into fresh culture vessels attached and grew as monolayers. Bar, 50 µm.
Mentions: Phase-contrast microscopy revealed that under standard culture conditions sub-confluent A549-NT and -T occurred as scattered colonies of associated cells (Figure 1A). However, confluent A549-NT cells appeared as cobblestone monolayer, characteristic of epithelial cell growth, consistent of closely associated cells with a typical polygonal, epithelial-like morphology indicating a stringent contact inhibition of cell growth (Figure 1B). In addition, this subpopulation formed tight cell-cell contacts leading to a significant prolongation of the trypsin treatment necessary for harvesting if compared with the time needed to harvest exponential growing A549-NT cells. The A549-T subpopulation also grew as a normal epithelial monolayer. However, in contrast to the A549-NT, some cells piled up on each other showing anchorage independence. These cell aggregates were found mainly at the top of the monolayer together with suspended cells (Figure 1C). Over time, the spheroid aggregates detached, floated unbound on top of the monolayer and formed proliferating colonies containing approximately 4–400 cells. After seeding A549-T spheroids into new culture vessels, most of the cells attached within a few hours (Figure 1D), grew to a confluent monolayer and again generated detached spheroids of growing cells (data not shown). A549-NT cells had a doubling time of approximately 24 hours and A549-T cells of approximately 20 hours as determined by cell cycle determinations (data not shown).

Bottom Line: Interestingly, CEACAM1-L, but not CEACAM1-S, negatively regulates proliferation via its ITIM domain, while in proliferating cells no CEACAM expression is detectable.Furthermore, we show for the first time that CEACAM6 acts as an inducer of cellular proliferation in A549 cells, likely by interfering with the contact-inhibiting signal triggered by CEACAM1-4L, leading to undifferentiated anchorage-independent cell growth.Taken together, our data suggest that post-confluent contact inhibition is established and maintained by CEACAM1-4L, but disturbances of CEACAM1 signalling by CEACAM1-4S and other CEACAMs lead to undifferentiated cell growth and malignant transformation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Anatomy, University Hospital Essen, Essen, Germany. BBSinger@gmx.de

ABSTRACT
CEACAM1, CEA/CEACAM5, and CEACAM6 are cell adhesion molecules (CAMs) of the carcinoembryonic antigen (CEA) family that have been shown to be deregulated in lung cancer and in up to 50% of all human cancers. However, little is known about the functional impact of these molecules on undifferentiated cell growth and tumor progression. Here we demonstrate that cell surface expression of CEACAM1 on confluent A549 human lung adenocarcinoma cells plays a critical role in differentiated, contact-inhibited cell growth. Interestingly, CEACAM1-L, but not CEACAM1-S, negatively regulates proliferation via its ITIM domain, while in proliferating cells no CEACAM expression is detectable. Furthermore, we show for the first time that CEACAM6 acts as an inducer of cellular proliferation in A549 cells, likely by interfering with the contact-inhibiting signal triggered by CEACAM1-4L, leading to undifferentiated anchorage-independent cell growth. We also found that A549 cells expressed significant amounts of non-membrane anchored variants of CEACAM5 and CEACAM6, representing a putative source for the increased CEACAM5/6 serum levels frequently found in lung cancer patients. Taken together, our data suggest that post-confluent contact inhibition is established and maintained by CEACAM1-4L, but disturbances of CEACAM1 signalling by CEACAM1-4S and other CEACAMs lead to undifferentiated cell growth and malignant transformation.

Show MeSH
Related in: MedlinePlus