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Modulation of differentiation and proliferation in human colon carcinoma cells by transforming growth factor beta 1
S Chakrabarty1, D Fan, J Varani
1Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030.
Abstract:
We have previously characterized the diversity of cellular responses to transforming growth factor (TGF)-beta 1 from human colon carcinoma cells. We now show that morphological alteration and part of the growth-inhibitory responses elicited by growth factor (GF) are associated with the secondary effect of the induction of synthesis of extracellular matrix (ECM) glycoproteins. Specifically, morphological alteration is associated with the ECM glycoprotein laminin, and growth inhibition is associated with both laminin and fibronectin. Both TGF-beta 1 and TGF-beta 2 down-modulate the expression of nucleolar protein B23 (also known as numatrin or nucleophosmin, a positive regulator of cell proliferation). With one exception, the biological effects of both TGF-beta 1 and TGF-beta 2 on these human colon carcinoma cell lines are identical. Both GFs up-modulate the expression of carcinoembryonic antigen (CEA) and CEA-related gene products. However, some of these products are differentially regulated by TGF-beta 1 and TGF-beta 2. The differences in the profile of the induction of these CEA and CEA-related gene products, in the responsive cells, functionally distinguish TGF-beta 1 from TGF-beta 2. Finally, we identified and characterized some of the cellular proteins, the expression of which is up-modulated by GF. These proteins are epithelium-associated, differentiation-related cytokeratins. Both TGF-beta 1 and TGF-beta 2 up-modulate expression of the acidic and basic subtypes of human keratins in the responsive human colon carcinoma cells. Both the responsive and unresponsive cells, however, possess receptors for GFs.
Insights
Transforming growth factor-beta (TGF-β) 1 and TGF-β 2 influence colon carcinoma cell behavior by altering extracellular matrix glycoprotein synthesis and regulating cell proliferation proteins. These growth factors also modulate carcinoembryonic antigen (CEA) expression and up-regulate cytokeratins.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Human colon carcinoma cells exhibit diverse cellular responses to transforming growth factor-beta 1 (TGF-β 1).
- Understanding the molecular mechanisms underlying these responses is crucial for targeted cancer therapies.
Purpose of the Study:
- To elucidate the specific cellular responses, including morphological alterations and growth inhibition, induced by TGF-β.
- To investigate the differential effects of TGF-β 1 and TGF-β 2 on gene expression, including extracellular matrix glycoproteins, nucleolar proteins, carcinoembryonic antigen (CEA), and cytokeratins in colon carcinoma cells.
Main Methods:
- Analysis of cellular responses such as morphological alteration and growth inhibition.
- Quantification of extracellular matrix (ECM) glycoprotein synthesis, including laminin and fibronectin.
- Assessment of gene expression modulation for nucleolar protein B23, CEA, and cytokeratins using techniques like Western blotting or RT-PCR (implied).
Main Results:
- Morphological alteration and growth inhibition are linked to the induction of ECM glycoproteins laminin and fibronectin.
- Both TGF-β 1 and TGF-β 2 down-regulate nucleolar protein B23 expression, a regulator of cell proliferation.
- TGF-β 1 and TGF-β 2 up-modulate CEA and related gene products, with differential regulation observed for some products, distinguishing the two TGF-β isoforms. Both isoforms also up-regulate cytokeratins.
Conclusions:
- TGF-β isoforms induce distinct and overlapping cellular responses in colon carcinoma, impacting ECM synthesis, cell proliferation regulators, and differentiation markers.
- Differential regulation of CEA-related products by TGF-β 1 and TGF-β 2 provides a functional distinction between these isoforms.
- The presence of growth factor receptors on both responsive and unresponsive cells suggests downstream signaling pathways mediate differential responses.