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An Orthotopic Murine Model of Human Prostate Cancer Metastasis
Published on: September 19, 2013
Introduction of Human Chromosome 13 into Retinoblastoma-Negative Metastatic Human Prostate Cancer Cells Increases
Abstract:
Like many other carcinomas, prostate cancer develops resistance to inhibition by transforming growth factor (TGF)-&be;1 during oncogenesis. One proposed mechanism of TGF-&be;1 action posits action of the retinoblastoma protein (pRb) to suppress c-myc transcription to inhibit cellular proliferation. A metastatic human prostate cancer cell line, DU145, has both nonfunctional pRb and markedly reduced sensitivity to TGF-&be;1 growth inhibition. The defective rb gene in DU145 cells was replaced by a normal rb allele by microcell fusion of chromosome 13. Two subclones, DU145-Cl-I and DU145-Cl-II, were studied in vitro to determine whether the pRb restoration increased sensitivity to the inhibitory effects of TGF-&be;1. By reverse transcriptase-polymerase chain reaction, increased sensitivity to the inhibitory effects of TGF-&BE;1. By reverse transcriptase-polymerase chain reaction, parental DU145 cells had TGF-b receptors of Type I and Type II. Introduction of chromosome 13 reduced the growth rate and prolonged the G1 phase compared with the parental DU145 cell line. Moreover, responsiveness to TGF-&be;1 growth inhibition was restored in a dose-dependent manner. Transcription of c-myc was not altered by TGF-&be;1 growth inhibition. Thus, DU145 cells presumably required the presence of wildtype rb to become growth inhibited that is independent of c-myc transcription. As the entire chromosome 13 was introduced, unknown tumor suppressor genes, not only rb, may be responsible for the restoration of TGF-&be;1 growth inhibition.
Insights
Restoring the retinoblastoma protein (pRb) in prostate cancer cells re-sensitized them to transforming growth factor-beta 1 (TGF-β1) growth inhibition. This effect was independent of c-myc transcription, suggesting other tumor suppressors on chromosome 13 may be involved.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Prostate cancer often develops resistance to TGF-β1 inhibition during oncogenesis.
- The retinoblastoma protein (pRb) is hypothesized to mediate TGF-β1's suppression of c-myc transcription and cellular proliferation.
- DU145 cells, a metastatic prostate cancer line, exhibit nonfunctional pRb and reduced TGF-β1 sensitivity.
Purpose of the Study:
- To investigate if restoring functional pRb in DU145 cells restores sensitivity to TGF-β1 growth inhibition.
- To determine the role of pRb and c-myc in TGF-β1 mediated growth inhibition in prostate cancer.
Main Methods:
- Microcell fusion was used to introduce a normal chromosome 13 (containing the rb gene) into DU145 cells.
- Two subclones, DU145-Cl-I and DU145-Cl-II, were analyzed in vitro.
- Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to assess gene expression and receptor presence.
- Cell growth rates and cell cycle phases (G1) were measured.
Main Results:
- Introduction of chromosome 13 restored TGF-β1 growth inhibition sensitivity in DU145 cells in a dose-dependent manner.
- Restored cells showed reduced growth rates and prolonged G1 phase compared to parental cells.
- TGF-β1 did not alter c-myc transcription in the presence of functional pRb.
- Parental DU145 cells possessed TGF-β receptors of Type I and Type II.
Conclusions:
- Functional pRb is necessary for TGF-β1-mediated growth inhibition in DU145 prostate cancer cells.
- This pRb-dependent growth inhibition is independent of c-myc transcription.
- Other tumor suppressor genes on the introduced chromosome 13 might also contribute to the restored TGF-β1 sensitivity.
