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Down-regulated c-myb expression inhibits DNA synthesis of T-leukemia cells in most patients
D Venturelli1, M T Mariano, C Szczylik
1Department of Pathology, Temple University, Philadelphia, Pennsylvania.
Abstract:
We have investigated the functional relevance of c-myb expression for DNA synthesis in patients' T-leukemia cells. [3H]Thymidine incorporation assays of 32 patients' leukemia cells exposed in vitro to c-myb sense or antisense oligodeoxynucleotides served to define two groups of patients: a responder group whose leukemia cells showed 2- to 16-fold lower levels of [3H]thymidine incorporation in c-myb antisense-treated cultures than in c-myb sense-treated cultures (20 patients) and a nonresponder group whose cells showed comparable [3H]thymidine incorporation levels in either c-myb sense- or antisense-treated cultures (12 patients). Down-regulation of c-myb mRNA levels in cells exposed to c-myb antisense oligodeoxynucleotides was comparable in both groups of patients, indicating that differential sensitivity to c-myb antisense oligodeoxynucleotides was not due to differential uptake of these oligodeoxynucleotides. DNA polymerase alpha mRNA levels were down-regulated in cells from the responders but were unaffected in the nonresponder group. These results suggest that c-myb is required for DNA synthesis in cells of many but not all T-leukemia patients and that leukemia cells in which DNA synthesis is not inhibited despite down-regulation of c-myb expression may have undergone some genetic change(s) that obviate(s) the requirement for myb protein.
Insights
The c-myb gene is crucial for DNA synthesis in most T-leukemia cells. Some leukemia cells resist c-myb inhibition, suggesting genetic alterations that bypass the need for myb protein.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The c-myb proto-oncogene plays a role in cell proliferation.
- Understanding c-myb's function in T-leukemia is critical for targeted therapies.
Purpose of the Study:
- To investigate the functional importance of c-myb gene expression in T-leukemia cell DNA synthesis.
- To identify patient subgroups based on their T-leukemia cells' response to c-myb inhibition.
Main Methods:
- Utilized [3H]thymidine incorporation assays on T-leukemia cells from 32 patients.
- Applied c-myb sense and antisense oligodeoxynucleotides in vitro.
- Quantified c-myb and DNA polymerase alpha mRNA levels.
Main Results:
- Identified two patient groups: responders (20/32) showing reduced DNA synthesis with c-myb antisense, and non-responders (12/32) showing no significant change.
- c-myb mRNA downregulation was similar in both groups, ruling out differential uptake.
- DNA polymerase alpha mRNA decreased in responders but remained unchanged in non-responders.
Conclusions:
- c-myb expression is essential for DNA synthesis in the majority of T-leukemia cells.
- Non-responder leukemia cells may possess genetic modifications that render them independent of c-myb for DNA replication.