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Reduced malignancy of ras-transformed NIH 3T3 cells expressing antisense osteopontin RNA
E I Behrend1, A M Craig, S M Wilson
1London Regional Cancer Centre, University of Western Ontario, Canada.
Abstract:
Osteopontin (OPN) is a secreted, calcium-binding phosphoprotein that frequently has been associated with the transformed phenotype. To clarify the function of OPN in tumor cells, we designed experiments to: (a) express antisense OPN RNA in murine PAP2 cells (metastatic, ras-transformed NIH 3T3 cells) and (b) examine the effects of antisense OPN expression on the tumorigenic and metastatic properties of the cells. PAP2 cells were transfected with pNMH-asOPN, an inducible, mammalian expression vector that can generate antisense OPN RNA complementary to the OPN mRNA. Two clones have been identified that expressed antisense OPN RNA in vitro. While reduced OPN protein secretion was not detected when the cells were grown in vitro, the in vivo expression of antisense OPN RNA was associated with reduced tumorigenicity. Tumors that did arise, with greatly extended lag time, had lost expression of antisense OPN RNA in vivo, suggesting that antisense OPN RNA expression was associated with reduced tumorigenicity of these cells.
Insights
Osteopontin (OPN) is linked to cancer. Inhibiting OPN RNA in tumor cells reduced their ability to form tumors, indicating OPN
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- Osteopontin (OPN) is a secreted phosphoprotein associated with cancer.
- Its role in tumor cell transformation and metastasis requires further investigation.
Purpose of the Study:
- To investigate the function of OPN in tumor cells.
- To examine the effects of antisense OPN RNA expression on tumorigenicity and metastasis.
Main Methods:
- Transfection of murine PAP2 cells with an inducible expression vector for antisense OPN RNA.
- Analysis of in vitro and in vivo OPN expression and tumorigenic properties.
Main Results:
- Two clones expressing antisense OPN RNA were identified.
- In vivo expression of antisense OPN RNA correlated with reduced tumor formation.
- Tumors that formed despite antisense OPN RNA expression had lost its expression.
Conclusions:
- Antisense OPN RNA expression is associated with reduced tumorigenicity in PAP2 cells.
- OPN may play a critical role in the development of tumors.