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Expression and function of Flt3/flk2 in human tumor cell lines
1Department of Hematology/Oncology, University of Munster, D-48129 Münster, Germany.
Abstract:
The receptor tyrosine kinase Flt3 is expressed on the blasts of a high proportion of AML cases. We were interested in the expression and function of Flt3 on various human tumors. human tumor cell lines were tested for Flt3 expression by northern blot analysis and RT-PCR using head/neck (n=3), breast (n=4), ovarian (n=4), small cell lung (n=2), non-small cell lung (n=2), gastric (n=1), colon (n=3), pancreatic (n=1) and prostate carcinoma (n=1), choriocarcinoma (n=1), glioblastoma (n=5), neuroblastoma (n=1), melanoma (n=3), lymphoma (n=1), Hodgkin's disease (n=2), and leukemic (n=6) cell lines. With no expression on the other cell samples, 3 of 6 leukemic cell lines showed expression of Flt3 mRNA. The cDNA region corresponding to the juxtamembrane domain did not show any mutation as determined by sequence analysis. In all 3 positive cell lines, protein expression was verified by immunoprecipitation followed by immunoblot analysis. Although Flt3 is functional in these cell lines, as judged by ligand-dependent receptor autophosphorylation, it only mediates a proliferative response in 2 of the 3 cell lines. In conclusion, Flt3 is expressed exclusively in hematopoietic malignancies. Although early signalling events are detectable in all Flt3-positive cell lines tested, the expression of Flt3 does not predict a proliferative response of the cell lines. No internal tandem duplication of the juxtamembrane domain can be observed.
Insights
Fms-like tyrosine kinase 3 (Flt3) is exclusively found in hematopoietic malignancies, not other tumors. While Flt3 signaling occurs, it doesn't always lead to proliferation in these cancer cell lines.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Fms-like tyrosine kinase 3 (Flt3) is frequently expressed on acute myeloid leukemia (AML) blasts.
- Investigating Flt3 expression and function across diverse human tumor types is crucial for understanding its role in cancer.
Purpose of the Study:
- To determine the expression profile of Flt3 in various human tumor cell lines.
- To assess the functional consequences of Flt3 expression, including its impact on cell proliferation.
Main Methods:
- Northern blot analysis and RT-PCR were used to detect Flt3 mRNA expression.
- Immunoprecipitation and immunoblot analysis confirmed protein expression.
- Sequence analysis identified mutations in the juxtamembrane domain.
- Ligand-dependent autophosphorylation assays evaluated receptor functionality.
Main Results:
- Flt3 expression was detected exclusively in 3 out of 6 tested leukemic cell lines; no expression was found in non-hematopoietic tumor cell lines.
- Flt3 protein was confirmed in the positive cell lines, and the receptor was functional, showing ligand-dependent autophosphorylation.
- Despite functional Flt3 signaling, only 2 of the 3 positive cell lines exhibited a proliferative response.
- No mutations, specifically internal tandem duplications, were found in the juxtamembrane domain of Flt3.
Conclusions:
- Flt3 expression is restricted to hematopoietic malignancies.
- Flt3 signaling is initiated in all tested positive cell lines, but this does not consistently predict a proliferative outcome.
- The absence of juxtamembrane domain mutations suggests alternative mechanisms regulate Flt3's role in proliferation.