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Conditioned medium from ras oncogene‐transformed nih 3T3 cells induces bone resorption in vitro
Author(s) -
Krieger Nancy S.,
Sukhatme Vikas P.,
Bushinsky David A.,
Sukhatme Vikas P.
Publication year - 1990
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650050209
Subject(s) - 3t3 cells , bone resorption , cathepsin , calcium , chemistry , in vitro , resorption , cell culture , microbiology and biotechnology , biology , endocrinology , biochemistry , transfection , enzyme , genetics , organic chemistry
Tumor‐associated hypercalcemia is due, in part, to enhanced osteoclastic bone resorption induced by soluble factors elaborated from malignant cells. ras transformation of NIH 3T3 cells results in a 50‐fold induction of cathepsin L mRNA and secretion of the corresponding protein. Since cathepsin L is an acid proteinase we asked whether conditioned medium from these cells would directly increase calcium release from bone in vitro. We tested conditioned medium obtained after 72 h culture of NIH 3T3 rar ‐ transformed cells (DT) or nontransformed NIH 3T3 cells (3T3) and identical medium not exposed to cells (Ctl). Incubation of either live or dead neonatal mouse calvaria for 48 h in DT‐conditioned medium increased calcium release compared to bones incubated with 3T3 medium. In both states the increased calcium release with DT medium was blocked by 0.25 mM E‐64, a general cysteine proteinase inhibitor, and 1 μM Z‐Phe‐Ala‐CH 2 F, a specific inhibitor of cathepsin L activity. Thus, conditioned medium from ras ‐transformed cells enhances calcium release in both live and dead bone. Since cathepsin L is the major protein secreted by these cells and the effect of DT‐conditioned medium is blocked by a specific inhibitor of cathepsin L, these studies suggest that this acid proteinase acts directly on bone mineral to enhance net calcium release