Related Experiment Videos
Conditioned medium from ras oncogene-transformed NIH 3T3 cells induces bone resorption in vitro
N S Krieger1, V P Sukhatme, D A Bushinsky
1Nephrology Program, Pritzker School of Medicine, University of Chicago 60637.
Summary
Ras-transformed cells release cathepsin L, an enzyme that directly increases calcium release from bone. This finding offers insight into tumor-associated hypercalcemia mechanisms.
Area of Science:
- Biochemistry
- Oncology
- Cell Biology
Background:
- Tumor-associated hypercalcemia involves increased bone resorption by osteoclasts.
- Malignant cells release factors that stimulate this process.
Purpose of the Study:
- To investigate if cathepsin L, secreted by ras-transformed cells, directly enhances calcium release from bone.
- To explore the role of this enzyme in tumor-associated hypercalcemia.
Main Methods:
- NIH 3T3 cells were transformed with ras, leading to increased cathepsin L expression.
- Conditioned medium from transformed cells was applied to neonatal mouse calvaria (bone samples).
- Calcium release was measured, and the effects of cathepsin L inhibitors were assessed.
Main Results:
- Conditioned medium from ras-transformed cells significantly increased calcium release from both live and dead bone.
- This effect was blocked by a general cysteine proteinase inhibitor and a specific cathepsin L inhibitor.
- Cathepsin L is the primary secreted protein responsible for this bone resorption.
Conclusions:
- Secreted cathepsin L from ras-transformed cells directly acts on bone mineral.
- This action enhances net calcium release, contributing to hypercalcemia in cancer.
- Cathepsin L is a key mediator in tumor-induced bone resorption.