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Up-regulation of transforming growth factor (TGF)-beta receptors by TGF-beta1 in COLO-357 cells
Abstract:
In the present study we investigated the actions of transforming growth factor (TGF)-beta1 on gene induction and cyclin-dependent kinase inhibitors in relation to TGF-beta receptor modulation in COLO-357 pancreatic cancer cells. TGF-beta1 inhibited the growth of COLO-357 cells in a time- and dose-dependent manner and caused a rapid but transient increase in plasminogen activator inhibitor-I and insulin-like growth factor binding protein-3 mRNA levels. TGF-beta1 caused a delayed but sustained increase in the protein levels of the cyclin-dependent kinase inhibitors p15(Ink4B), p21(Cip1), and p27(Kip1) and a sustained increase in type I and II TGF-beta receptors (TbetaRI and TbetaRII) mRNA and protein levels. The protein synthesis inhibitor cycloheximide (10 microg/ml) completely blocked the TGF-beta1-mediated increase in TbetaRI and TbetaRII expression. Furthermore, a nuclear runoff transcription assay revealed that the increase in receptor mRNA levels was due to newly transcribed RNA. There was a significant increase in TbetaRI and TbetaRII mRNA levels in confluent cells in comparison to subconfluent (
Insights
Transforming growth factor-beta1 (TGF-beta1) inhibits pancreatic cancer cell growth by up-regulating TGF-beta receptors. This process involves transcriptional mechanisms, enhancing TGF-beta1
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Signaling
Background:
- Transforming growth factor-beta1 (TGF-beta1) plays a critical role in cell growth and differentiation.
- Dysregulation of TGF-beta signaling is implicated in various cancers, including pancreatic cancer.
- Understanding TGF-beta1's actions on pancreatic cancer cells is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the effects of TGF-beta1 on gene induction and cyclin-dependent kinase inhibitors in COLO-357 pancreatic cancer cells.
- To examine the relationship between TGF-beta1 actions and TGF-beta receptor modulation.
- To elucidate the mechanisms underlying TGF-beta1-mediated cellular responses.
Main Methods:
- Time- and dose-dependent treatment of COLO-357 cells with TGF-beta1.
- Analysis of mRNA and protein levels of specific genes and proteins, including plasminogen activator inhibitor-I, insulin-like growth factor binding protein-3, and cyclin-dependent kinase inhibitors (p15Ink4B, p21Cip1, p27Kip1).
- Assessment of TGF-beta receptor (TbetaRI, TbetaRII) expression using Northern blot, sequencing, and nuclear runoff transcription assays.
- Inhibition studies using cycloheximide to block protein synthesis.
Main Results:
- TGF-beta1 inhibited COLO-357 cell growth in a time- and dose-dependent manner.
- TGF-beta1 induced rapid, transient increases in PAI-I and IGFBP-3 mRNA levels.
- TGF-beta1 caused a delayed, sustained increase in p15Ink4B, p21Cip1, and p27Kip1 protein levels.
- TGF-beta1 treatment led to a sustained increase in TbetaRI and TbetaRII mRNA and protein levels via transcriptional regulation.
- Increased receptor expression was observed in confluent and serum-starved cells.
- COLO-357 cells possess a normal SMAD4 gene.
Conclusions:
- TGF-beta1 modulates multiple cellular functions in COLO-357 pancreatic cancer cells.
- TGF-beta1 up-regulates its own receptor expression through a transcriptional mechanism.
- This receptor up-regulation potentially maximizes TGF-beta1-dependent antiproliferative responses in pancreatic cancer cells.