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A retrovirus encoding the v-fps protein-tyrosine kinase induces factor-independent growth and tumorigenicity in
K A Meckling-Gill1, S P Yee, J W Schrader
1Division of Molecular and Developmental Biology, Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada.
Abstract:
There is increasing evidence that protein-tyrosine kinases play pivotal roles in the response to growth-factor signals. The cytoplasmic tyrosine kinase c-fps/fes, due to its restricted expression in hematopoietic tissue, is likely to participate in hematopoietic growth-factor signalling. We have introduced a retrovirus containing an activated fps gene (encoding P130gag-fps) into the growth factor-dependent myeloid cell line FDC-P1. Clonal cell lines were derived by selection for a marker gene coding for G418 resistance in the absence or presence of the hematopoietic growth factor IL-3. G418 resistant clones expressed P130gag-fps and its associated protein-tyrosine kinase activity and displayed either a factor-independent or IL-3 hypersensitive phenotype and were tumorigenic in syngeneic recipients. Thus, introduction of the activated v-fps gene was able to circumvent the requirement for exogenous growth factors by FDC-P1 cells. Bioassay of conditioned medium from the various clones did not detect hematopoietic growth factor activity and PCR analysis for IL-3 transcripts were negative, suggesting that growth-factor independence was achieved by a mechanism other than autocrine production of a growth factor. We suggest that P130gag-fps is acting to directly stimulate a hematopoietic growth-factor signalling pathway, perhaps one that normally involves the endogenous c-fps/fes protein-tyrosine kinase of FDC-P1 cells.
Insights
Introducing an activated fps gene into myeloid cells bypasses the need for external growth factors. This suggests the P130gag-fps protein directly stimulates cell signaling pathways, impacting hematopoietic growth.
Area of Science:
- Molecular Biology
- Cell Signaling
- Oncology
Background:
- Protein-tyrosine kinases are crucial for growth factor signal transduction.
- The c-fps/fes tyrosine kinase is implicated in hematopoietic growth factor signaling due to its expression in myeloid tissues.
Purpose of the Study:
- To investigate the role of an activated fps gene in myeloid cell growth.
- To determine if introducing an activated fps gene can confer growth factor independence to myeloid cell lines.
Main Methods:
- Retroviral introduction of an activated fps gene (encoding P130gag-fps) into FDC-P1 myeloid cells.
- Selection of G418 resistant clones in the presence or absence of IL-3.
- Analysis of P130gag-fps expression, tyrosine kinase activity, and growth factor dependence.
Main Results:
- Transduced FDC-P1 cells expressing P130gag-fps exhibited factor-independent or IL-3 hypersensitive growth.
- These clones were tumorigenic in vivo.
- Absence of autocrine growth factor production was confirmed by bioassay and PCR.
Conclusions:
- The activated v-fps gene circumvents the need for exogenous growth factors in FDC-P1 cells.
- P130gag-fps likely directly stimulates hematopoietic growth factor signaling pathways.
- This provides insight into the mechanism of growth factor signaling in hematopoietic cells.