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Abundance of Flt3 and its ligand in astrocytic tumors
1Department of Neuropathology, Otto-von-Guericke University, Magdeburg.
Background:
Molecular targeted therapies for astrocytic tumors are the subject of growing research interest, due to the limited response of these tumors, especially glioblastoma multiforme, to conventional chemotherapeutic regimens. Several of these approaches exploit the inhibition of receptor tyrosine kinases. To date, it has not been elucidated if fms-like tyrosine kinase-3 (Flt3) and its natural ligand (Flt3L) are expressed in astrocytic tumors, although some of the clinically intended small-molecule receptor tyrosine kinase inhibitors affect Flt3, while others do not. More importantly, the recent proof of principle for successful stimulation of the immune system against gliomas in preclinical models via local Flt3L application requires elucidation of this receptor tyrosine kinase pathway in these tumors in more detail. This therapy is based on recruitment of Flt3-positive dendritic cells, but may be corroborated by activity of this signaling pathway in glioma cells.
Methods:
Receptor and ligand expression was analyzed by real-time polymerase chain reaction in 31 astrocytic tumors (six diffuse and 11 anaplastic astrocytomas, 14 glioblastomas) derived from patients of both genders and in glioblastoma cell lines. The two most common activating mutations of the Flt3 gene, ie, internal tandem duplication and D835 point mutation, were assessed by specific polymerase chain reaction.
Results:
A relatively high abundance of Flt3L mRNA (4%-6% of the reference, b2 microglobulin) could be demonstrated in all tumor samples. Flt3 expression could generally be demonstrated by 40 specific polymerase chain reaction cycles and gel electrophoresis in 87% of the tumors, including all grades, although the small quantities of the receptor did not allow reliable quantification. Expression of both mRNAs was verified in the cell lines, excluding a derivation solely from contaminating lymphocytes or macrophages. No activating mutations were found.
Conclusion:
Our results warrant further analysis of endogenous Flt3 signaling in these tumors prior to application of immunotherapy in human patients.
Insights
Fms-like tyrosine kinase-3 (Flt3) and its ligand are present in astrocytic tumors, suggesting potential for targeted therapies. Further research is needed before applying Flt3-based immunotherapy in human patients.
Area of Science:
- Neuro-oncology
- Molecular biology
- Immunotherapy
Background:
- Astrocytic tumors, particularly glioblastoma, show limited response to conventional therapies.
- Molecular targeted therapies, including receptor tyrosine kinase inhibitors, are under investigation.
- The role of fms-like tyrosine kinase-3 (Flt3) and its ligand (Flt3L) in astrocytic tumors is not fully understood.
Purpose of the Study:
- To investigate the expression of Flt3 and Flt3L in astrocytic tumors.
- To determine if Flt3 signaling pathways are active in these tumors.
- To assess the potential of Flt3-targeted therapies and immunotherapies for astrocytic tumors.
Main Methods:
- Real-time polymerase chain reaction (PCR) was used to analyze Flt3 and Flt3L mRNA expression in 31 astrocytic tumor samples and glioblastoma cell lines.
- Specific PCR was employed to detect common activating mutations in the Flt3 gene.
- Expression levels were quantified relative to a reference gene (b2 microglobulin).
Main Results:
- Flt3L mRNA was highly abundant in all tested astrocytic tumor samples.
- Flt3 receptor mRNA was detected in 87% of the tumors across all grades.
- Expression of both Flt3 and Flt3L was confirmed in glioblastoma cell lines, ruling out lymphocyte or macrophage contamination.
- No activating mutations in the Flt3 gene were identified.
Conclusions:
- Endogenous Flt3 signaling is present in astrocytic tumors.
- These findings support further investigation into Flt3's role in gliomas.
- The results provide a basis for future immunotherapy strategies targeting Flt3 in human patients.
