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Differential regulation of choriocarcinoma gene expression by DNA synthesis inhibitors
J L Arbiser1, Z K Arbiser, J A Majzoub
1Division of Endocrinology, Children's Hospital, Boston, MA 02115.
Abstract:
We have previously shown that methotrexate (MTX) and hydroxyurea (HU) stimulate expression of the human chorionic gonadotropin alpha and placental alkaline phosphatase genes and repress the expression of the c-myc oncogene in BeWo choriocarcinoma cells. In order to determine whether c-myc downregulation played a role in the induction of these placental genes, we treated BeWo choriocarcinoma cells with aphidicolin (APH), and 6-diazo-5-oxo-L-norleucine (DON), and compared the effects of these drugs with that of MTX. All of these drugs downregulate c-myc gene expression. At the doses used, both APH and DON repress c-myc expression to approximately the same extent, as well as inducing morphologic changes in BeWo similar to that of MTX, although neither stimulated hCG alpha expression. Both DON and APH stimulate placental alkaline phosphatase gene expression, but only MTX and DON stimulate cholesterol side chain cleavage enzyme gene expression. This indicates that the downregulation of c-myc gene expression is insufficient to stimulate the expression of all the placental genes stimulated by MTX.
Insights
Downregulating c-myc oncogene expression alone is insufficient to induce all placental genes. Methotrexate (MTX) and other drugs show varied effects on gene expression in BeWo cells.
Area of Science:
- Cell biology
- Molecular oncology
- Gene expression regulation
Background:
- Methotrexate (MTX) and hydroxyurea (HU) previously shown to induce placental genes (hCG alpha, PLAP) and repress c-myc in BeWo cells.
- The role of c-myc downregulation in MTX-induced placental gene expression remains unclear.
Purpose of the Study:
- To investigate if c-myc downregulation is sufficient for inducing placental-specific gene expression.
- To compare the effects of aphidicolin (APH) and 6-diazo-5-oxo-L-norleucine (DON) with MTX on gene expression and cellular morphology in BeWo cells.
Main Methods:
- Treatment of BeWo choriocarcinoma cells with MTX, APH, and DON.
- Analysis of c-myc, hCG alpha, placental alkaline phosphatase (PLAP), and cholesterol side chain cleavage enzyme gene expression.
- Observation of morphological changes in BeWo cells.
Main Results:
- APH and DON, like MTX, downregulated c-myc expression and induced similar morphological changes.
- Neither APH nor DON stimulated hCG alpha expression.
- DON and APH stimulated PLAP expression, while MTX and DON stimulated cholesterol side chain cleavage enzyme expression.
Conclusions:
- c-myc downregulation is necessary but not sufficient for the induction of all placental genes by MTX.
- Different drugs can induce specific placental genes through distinct pathways, independent of c-myc repression.