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H-RYK, an unusual receptor kinase: isolation and analysis of expression in ovarian cancer
1ICRF Molecular Oncology Laboratories, John Radcliffe Hospital, Headington, Oxford, United Kingdom.
Background:
Protein tyrosine kinases play an important role in cellular metabolism as key components of signal transduction pathways. They are involved in cellular growth, differentiation, and development. Receptor tyrosine kinases (EGF receptor and c-erbB2) have been shown to be important in the pathogenesis of cancer. In ovarian cancer, overexpression of c-erbB2, a type I receptor, has been correlated with an adverse effect on survival of patients.
Material And Methods:
An unusual receptor tyrosine kinase, H-RYK, has been isolated from a complimentary DNA library of SKOV-3, an epithelial ovarian cancer cell line, using a polymerase chain reaction-mediated approach.
Results:
The primary structure of the predicted amino acid sequence of the protein shows a novel NH2-terminal region. The catalytic region shows homology to other tyrosine kinases, the closest homology being with v-sea (39%). A significant alteration in the catalytic domain is that the highly conserved "DFG" triplet in subdomain VII is altered to "DNA." The gene was mapped to chromosome 3q22. A single transcript of 3.0 kb is expressed in heart, brain, lung, placenta, liver, muscle, kidney, and pancreas by Northern analysis with maximal expression in skeletal muscle. In situ hybridization analysis on human tissues demonstrated localization of message in the epithelial and stromal compartment of tissues such as brain, lung, colon, kidney, and breast. There was minimal to absent expression of H-RYK on surface epithelium of ovaries. In benign (3) and borderline tumors of the ovary (5), there was expression in the stromal compartment. However, in malignant tumors (24) there was increased expression predominantly confined to the epithelium. Polyclonal antisera raised against synthetic peptides recognize a 100-kD protein in ovarian cancer cells and other cell lines. In contrast to other receptor tyrosine kinases, the receptor did not phosphorylate in an in vitro kinase assay.
Conclusions:
The expression of this unusual receptor tyrosine kinase in epithelial ovarian cancer suggests that it may be involved in tumor progression, which needs further investigation.
Insights
A novel receptor tyrosine kinase, H-RYK, was identified in ovarian cancer cells. Its altered catalytic domain and increased epithelial expression in malignant tumors suggest a role in ovarian cancer progression.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- Protein tyrosine kinases are crucial for cellular signaling, growth, and development.
- Receptor tyrosine kinases like EGF receptor and c-erbB2 are implicated in cancer pathogenesis.
- Overexpression of c-erbB2 in ovarian cancer correlates with poor patient survival.
Purpose of the Study:
- To isolate and characterize a novel receptor tyrosine kinase (H-RYK) from an epithelial ovarian cancer cell line.
- To investigate the expression pattern and potential role of H-RYK in ovarian cancer.
Main Methods:
- Polymerase chain reaction (PCR) was used to isolate H-RYK from SKOV-3 cells.
- Northern analysis and in situ hybridization were performed to determine gene expression and localization.
- Polyclonal antisera were generated to detect the H-RYK protein.
Main Results:
- H-RYK possesses a novel NH2-terminal region and a catalytic domain with a unique "DNA" alteration instead of the conserved "DFG" triplet.
- The H-RYK gene is located on chromosome 3q22 and expresses a 3.0 kb transcript in various human tissues, with maximal expression in skeletal muscle.
- While H-RYK shows minimal expression on normal ovarian surface epithelium, it is upregulated in the stromal compartment of benign and borderline tumors and predominantly in the epithelium of malignant ovarian tumors.
- A 100-kD protein recognized by specific antisera was detected in ovarian cancer cells, but H-RYK did not exhibit in vitro kinase activity.
Conclusions:
- The unusual structure and altered expression pattern of H-RYK in ovarian cancer suggest its potential involvement in tumor progression.
- Further research is warranted to elucidate the precise role of this novel receptor tyrosine kinase in ovarian tumorigenesis.