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Novel and known protein tyrosine kinases and their abnormal expression in human melanoma
Abstract:
We have used the polymerase chain reaction and Northern blotting to identify protein tyrosine kinases that may play an important role in the process of melanoma initiation and progression. Degenerate primers from the conserved catalytic domain of tyrosine kinase genes were used to amplify and clone partial cDNA sequences from a human melanoma cell line (DX3-LT5.1) and normal human melanocytes. When the melanoma reaction products were sequenced, 13 distinct clones were found, of which one is novel to date and has provisionally been named MEK (for melanocytic kinase). Of the remaining 12 known kinases, only two, ERB-B2 and IGF1-R, have previously been reported in pigment cells. Reaction products from melanocytes included only eight of these 13 sequences. To test for quantitative differences in tyrosine kinase expression between normal and malignant cells, a panel of eight melanoma lines and normal melanocytes was analyzed by Northern blotting. Two tyrosine kinases (JTK-14/TIE and TYRO-9) were detected in some melanomas but were not found in normal melanocytes, whereas others, including MEK, appeared to be overexpressed in some malignant lines. A minority of kinases showed either no change or a reduction in the level of mRNA. Expression of tyrosine kinases varied independently, and individual lines contained various combinations of these enzymes. Our findings are consistent with an increased overall expression of these putative growth factor receptors during melanoma development.
Insights
Researchers identified novel protein tyrosine kinases, including melanocytic kinase (MEK), involved in melanoma development. Some kinases were overexpressed in melanoma cells, suggesting a role in cancer progression.
Area of Science:
- Molecular Biology
- Oncology
- Biochemistry
Background:
- Protein tyrosine kinases (PTKs) are crucial signaling molecules implicated in cell growth and differentiation.
- Dysregulation of PTKs is frequently observed in various cancers, including melanoma.
Purpose of the Study:
- To identify and characterize novel protein tyrosine kinases involved in melanoma initiation and progression.
- To investigate quantitative differences in PTK expression between normal melanocytes and melanoma cells.
Main Methods:
- Polymerase chain reaction (PCR) was employed to amplify and clone partial cDNA sequences of tyrosine kinase genes.
- Northern blotting was utilized to analyze and compare PTK mRNA expression levels in melanoma cell lines and normal melanocytes.
Main Results:
- Thirteen distinct tyrosine kinase clones were identified from melanoma cells, including a novel kinase provisionally named MEK (melanocytic kinase).
- Two specific tyrosine kinases (JTK-14/TIE and TYRO-9) were detected in melanoma but not in normal melanocytes.
- Several tyrosine kinases, including MEK, showed overexpression in certain melanoma lines, while others exhibited reduced or unchanged expression.
Conclusions:
- The study identifies specific protein tyrosine kinases, including a novel one (MEK), as potentially significant players in melanoma development.
- Aberrant expression patterns of PTKs, including overexpression and unique presence in malignant cells, suggest their involvement in melanoma pathogenesis.
- Findings support the hypothesis of increased expression of growth factor receptors during melanoma development.