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Carcinoembryonic antigen, a human tumor marker, cooperates with Myc and Bcl-2 in cellular transformation.

Screaton RA, Penn LZ, Stanners CP - J. Cell Biol. (1997)

Bottom Line: The further expression of CEA has a dominant effect in blocking differentiation, regardless of the presence of the other activated oncogenes, generating cells that enter a reversible quiescent G0-like state in medium promoting differentiation.Transfectants expressing CEA with or without v-myc and bcl-2 allow the emergence of cells with the property of heritable, efficient, anchorage-independent growth in soft agar and the ability to markedly reduce the latency for tumor formation in nude mice.We propose that by prolonging cell survival in the presence of differentiation signals, CEA represents a novel class of dominant differentiation-blocking oncogene.

View Article: PubMed Central - PubMed

Affiliation: McGill Cancer Centre and Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1Y6.

ABSTRACT
Carcinoembryonic antigen (CEA) is a tumor marker that is overexpressed in many human cancers and functions in vitro as a homotypic intercellular adhesion molecule. We have investigated the possibility of synergy between CEA, v-Myc, and Bcl-2 in the transformation of cells with differentiation capacity. We find that v-Myc increases the cell division rate and maximum density of rat L6 myoblasts but also markedly stimulates both apoptosis and surprisingly, differentiation, thus preventing transformation. The superposition of Bcl-2 blocks the apoptotic stimulation of v-Myc and independently promotes further cell division at confluence, but still allows differentiation. The further expression of CEA has a dominant effect in blocking differentiation, regardless of the presence of the other activated oncogenes, generating cells that enter a reversible quiescent G0-like state in medium promoting differentiation. Transfectants expressing CEA with or without v-myc and bcl-2 allow the emergence of cells with the property of heritable, efficient, anchorage-independent growth in soft agar and the ability to markedly reduce the latency for tumor formation in nude mice. We propose that by prolonging cell survival in the presence of differentiation signals, CEA represents a novel class of dominant differentiation-blocking oncogene.

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CEA transfectants of L6 and C2 myoblasts retain division potential in DM. FACS profiles (A) of parental rat L6 cells  (P), CEA transfectant clone (C-1) and CEA total transfectant  population (C), and (C) mouse C2 and CEA transfectant total  population (C2C) labeled with rabbit anti–human CEA antibodies. In all cases, anti-CEA immunoreactivity was detected using  goat anti–rabbit FITC-conjugated antibody, as described in Materials and Methods. (B) L6 and (D) C2 cells expressing CEA retain division potential in DM, as measured by their ability to form  colonies in GM. Cells were seeded in GM on day −3, and the medium was changed to DM on day 0. To calculate percentage viability, colony numbers were normalized to values obtained on  day 2 in GM (day −1 in DM). Fusion indices are shown by dotted  lines.
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Figure 7: CEA transfectants of L6 and C2 myoblasts retain division potential in DM. FACS profiles (A) of parental rat L6 cells (P), CEA transfectant clone (C-1) and CEA total transfectant population (C), and (C) mouse C2 and CEA transfectant total population (C2C) labeled with rabbit anti–human CEA antibodies. In all cases, anti-CEA immunoreactivity was detected using goat anti–rabbit FITC-conjugated antibody, as described in Materials and Methods. (B) L6 and (D) C2 cells expressing CEA retain division potential in DM, as measured by their ability to form colonies in GM. Cells were seeded in GM on day −3, and the medium was changed to DM on day 0. To calculate percentage viability, colony numbers were normalized to values obtained on day 2 in GM (day −1 in DM). Fusion indices are shown by dotted lines.

Mentions: To affect complete transformation of L6 myoblasts by Myc and Bcl-2, a gene product that could block myogenic differentiation was required. We previously reported that CEA could provide a complete block of both morphological and biochemical myogenic differentiation of L6 cells while leaving the cells with proliferative potential (Eidelman et al., 1993). We decided first to characterize the cell biology of CEA-expressing L6 cells, to check for the generality of the phenomenon in another myogenic cell line, and finally to superimpose CEA on MB cells to determine whether this combination of genes would result in full malignant transformation. To this end, L6 rat and C2 mouse myoblasts were transfected with expression vectors containing CEA cDNA (Beauchemin et al., 1987) by calcium phosphate precipitation. Stable transfectant L6 and C2 total cell populations were enriched for cell surface CEA by cytofluorometric sorting after labeling with anti–human CEA antibody. These total transfectant populations (L6C or C, C2C) and individual clones (L6C-1) were analyzed for CEA expression by FACS analysis (Fig. 7, A and C). The levels of cell surface expression of CEA were within the range seen by FACS analysis of purified colonocytes from freshly excised human colon carcinomas (Ilantzis et al., 1997).


Carcinoembryonic antigen, a human tumor marker, cooperates with Myc and Bcl-2 in cellular transformation.

Screaton RA, Penn LZ, Stanners CP - J. Cell Biol. (1997)

CEA transfectants of L6 and C2 myoblasts retain division potential in DM. FACS profiles (A) of parental rat L6 cells  (P), CEA transfectant clone (C-1) and CEA total transfectant  population (C), and (C) mouse C2 and CEA transfectant total  population (C2C) labeled with rabbit anti–human CEA antibodies. In all cases, anti-CEA immunoreactivity was detected using  goat anti–rabbit FITC-conjugated antibody, as described in Materials and Methods. (B) L6 and (D) C2 cells expressing CEA retain division potential in DM, as measured by their ability to form  colonies in GM. Cells were seeded in GM on day −3, and the medium was changed to DM on day 0. To calculate percentage viability, colony numbers were normalized to values obtained on  day 2 in GM (day −1 in DM). Fusion indices are shown by dotted  lines.
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Related In: Results  -  Collection

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Figure 7: CEA transfectants of L6 and C2 myoblasts retain division potential in DM. FACS profiles (A) of parental rat L6 cells (P), CEA transfectant clone (C-1) and CEA total transfectant population (C), and (C) mouse C2 and CEA transfectant total population (C2C) labeled with rabbit anti–human CEA antibodies. In all cases, anti-CEA immunoreactivity was detected using goat anti–rabbit FITC-conjugated antibody, as described in Materials and Methods. (B) L6 and (D) C2 cells expressing CEA retain division potential in DM, as measured by their ability to form colonies in GM. Cells were seeded in GM on day −3, and the medium was changed to DM on day 0. To calculate percentage viability, colony numbers were normalized to values obtained on day 2 in GM (day −1 in DM). Fusion indices are shown by dotted lines.
Mentions: To affect complete transformation of L6 myoblasts by Myc and Bcl-2, a gene product that could block myogenic differentiation was required. We previously reported that CEA could provide a complete block of both morphological and biochemical myogenic differentiation of L6 cells while leaving the cells with proliferative potential (Eidelman et al., 1993). We decided first to characterize the cell biology of CEA-expressing L6 cells, to check for the generality of the phenomenon in another myogenic cell line, and finally to superimpose CEA on MB cells to determine whether this combination of genes would result in full malignant transformation. To this end, L6 rat and C2 mouse myoblasts were transfected with expression vectors containing CEA cDNA (Beauchemin et al., 1987) by calcium phosphate precipitation. Stable transfectant L6 and C2 total cell populations were enriched for cell surface CEA by cytofluorometric sorting after labeling with anti–human CEA antibody. These total transfectant populations (L6C or C, C2C) and individual clones (L6C-1) were analyzed for CEA expression by FACS analysis (Fig. 7, A and C). The levels of cell surface expression of CEA were within the range seen by FACS analysis of purified colonocytes from freshly excised human colon carcinomas (Ilantzis et al., 1997).

Bottom Line: The further expression of CEA has a dominant effect in blocking differentiation, regardless of the presence of the other activated oncogenes, generating cells that enter a reversible quiescent G0-like state in medium promoting differentiation.Transfectants expressing CEA with or without v-myc and bcl-2 allow the emergence of cells with the property of heritable, efficient, anchorage-independent growth in soft agar and the ability to markedly reduce the latency for tumor formation in nude mice.We propose that by prolonging cell survival in the presence of differentiation signals, CEA represents a novel class of dominant differentiation-blocking oncogene.

View Article: PubMed Central - PubMed

Affiliation: McGill Cancer Centre and Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1Y6.

ABSTRACT
Carcinoembryonic antigen (CEA) is a tumor marker that is overexpressed in many human cancers and functions in vitro as a homotypic intercellular adhesion molecule. We have investigated the possibility of synergy between CEA, v-Myc, and Bcl-2 in the transformation of cells with differentiation capacity. We find that v-Myc increases the cell division rate and maximum density of rat L6 myoblasts but also markedly stimulates both apoptosis and surprisingly, differentiation, thus preventing transformation. The superposition of Bcl-2 blocks the apoptotic stimulation of v-Myc and independently promotes further cell division at confluence, but still allows differentiation. The further expression of CEA has a dominant effect in blocking differentiation, regardless of the presence of the other activated oncogenes, generating cells that enter a reversible quiescent G0-like state in medium promoting differentiation. Transfectants expressing CEA with or without v-myc and bcl-2 allow the emergence of cells with the property of heritable, efficient, anchorage-independent growth in soft agar and the ability to markedly reduce the latency for tumor formation in nude mice. We propose that by prolonging cell survival in the presence of differentiation signals, CEA represents a novel class of dominant differentiation-blocking oncogene.

Show MeSH
Related in: MedlinePlus