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Murine c-myc retroviruses alter the growth requirements of myeloid cell lines
1Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia.
Abstract:
Recombinant retroviruses encoding a murine c-myc gene were utilised to explore the consequences of constitutive c-myc expression for interleukin 3-dependent murine myeloid cell lines. The c-myc virus-infected cells exhibited a diminished requirement for growth factor and serum when grown in soft agar, but no factor-independent cells could be isolated and the cells were not tumorigenic. Thus deregulated expression of a c-myc gene at physiological levels apparently renders myeloid cells more responsive to growth factors but cannot abrogate this requirement or render the cells malignant.
Insights
Constitutive c-myc gene expression in myeloid cells increased growth factor responsiveness but did not lead to factor independence or malignancy. This suggests c-myc enhances growth factor signaling without causing cancer.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Interleukin-3 (IL-3) is crucial for myeloid cell survival and proliferation.
- The c-myc proto-oncogene plays a key role in cell growth and differentiation.
- Understanding c-myc's role in myeloid cells is vital for cancer research.
Purpose of the Study:
- To investigate the effects of constitutive c-myc expression on IL-3-dependent myeloid cell lines.
- To determine if deregulated c-myc can overcome growth factor dependency.
- To assess the potential for c-myc-induced transformation and tumorigenicity.
Main Methods:
- Utilized recombinant retroviruses to introduce a murine c-myc gene.
- Infected IL-3-dependent murine myeloid cell lines with c-myc retroviruses.
- Assessed cell growth characteristics in soft agar and evaluated factor independence and tumorigenicity.
Main Results:
- c-myc virus-infected cells showed a reduced requirement for growth factor and serum in soft agar.
- No completely factor-independent cells were isolated from the cultures.
- The c-myc expressing cells did not form tumors when assessed for tumorigenicity.
Conclusions:
- Constitutive expression of c-myc at physiological levels enhances myeloid cell responsiveness to growth factors.
- Deregulated c-myc alone is insufficient to abrogate growth factor dependency in these cells.
- Physiological levels of deregulated c-myc do not render myeloid cells malignant or tumorigenic.