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Increased expression of midkine during the progression of human astrocytomas
K Mishima1, A Asai, K Kadomatsu
1Department of Neurosurgery, Faculty of Medicine, University of Tokyo, Hongo, Japan.
Abstract:
Midkine (MK), a member of a new family of neurotrophic and angiogenic growth factors whose expression is developmentally regulated, is produced in fetal astrocytes. Malignant astrocytomas, one of the most neovascularized tumors, are derived from astrocytes. There has been no investigation of the expression of MK in human astrocytic tumors. To determine if increased levels of MK expression correlate with the progression of human astrocytomas, we examined surgical specimens of astrocytic tumors of various grades using Northern and Western blotting. MK mRNA and protein expression levels were higher in high-grade astrocytomas (anaplastic astrocytomas and glioblastomas) than in low-grade astrocytomas. As shown by in situ hybridization, MK mRNA expression was intense in a majority of glioblastoma cells but was weak in a small number of low-grade astrocytoma cells. These findings suggest that MK expression correlates with the malignant progression of astrocytomas. The aberrant MK expression in high-grade astrocytomas may underlie their rapid growth and well-vascularized features.
Insights
Midkine (MK) expression increases with astrocytoma grade. Aberrant MK levels in high-grade astrocytomas may drive tumor growth and vascularization.
Area of Science:
- Neuroscience
- Oncology
- Molecular Biology
Background:
- Midkine (MK) is a growth factor involved in development, produced by fetal astrocytes.
- Astrocytomas, particularly malignant forms, are highly vascularized tumors originating from astrocytes.
- The role of MK in human astrocytoma progression remains unexplored.
Purpose of the Study:
- To investigate Midkine (MK) expression in human astrocytic tumors.
- To determine if MK levels correlate with astrocytoma grade and malignant progression.
Main Methods:
- Analysis of surgical specimens from astrocytic tumors of varying grades.
- Utilized Northern blotting for mRNA expression analysis.
- Employed Western blotting for protein expression analysis.
- Performed in situ hybridization to localize MK mRNA expression within tumor cells.
Main Results:
- MK mRNA and protein levels were significantly elevated in high-grade astrocytomas (anaplastic astrocytomas, glioblastomas) compared to low-grade astrocytomas.
- In situ hybridization revealed intense MK mRNA expression in most glioblastoma cells, contrasting with weak expression in few low-grade astrocytoma cells.
- Findings indicate a positive correlation between MK expression and astrocytoma malignancy.
Conclusions:
- Midkine (MK) expression correlates with the malignant progression of human astrocytomas.
- Aberrant MK expression in high-grade astrocytomas may contribute to their aggressive phenotypes, including rapid growth and enhanced neovascularization.