Endogenous prostaglandin production by established cultures of neoplastic rat mammary epithelial cells
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The production and release of prostaglandins (PGs) into the growth medium by established cultures of neoplastic, mammary epithelial cells derived from (a)N-nitrosomethyl-urea (NMU)-induced and (b) 7,12-dimethylbenz(a) anthracene (DMBA)-induced mammary tumors, was assessed using radioimmunoassay techniques.
Prostaglandin production was determined, to a considerable extent, by in vitro conditions and the tumor line analyzed. In medium supplemented with bovine calf serum (10%), NMU cells synthesized and released nanogram quantities of PGF2, PGE1, and PGF2α (6.7, 4.7, and 1.7 ng/106 cells per 48 h, respectively). Concentrations of the two stable protanoid metabolites, 6-keto-PGF1α and TXB2, were indistinguishable from controls. In cells derived from the DMBA-induced tumor (RBA cells), no net production of immunoreactive PGs was detected. In contrast, in media supplemented with fetal bovine serum (10%), both RBA and NMU cells synthesized and released nanogram quantities of PGE2 (1 and 4 ng/106 cells per 48 h, respectively).
PGE2 production by both NMU and RBA cells was inhibited by ibuprofen, an inhibitor of cyclooxygenase (EC 1. 14. 99.1). The pattern of PG inhibition by ibuprofen differed in the two cell lines. In NMU cells, a linear dose-response inhibitory pattern was discernable, whereas in RBA cells a biphasic pattern was observed; PGE2 levels incresed at low concentration of ibuprofen and then decreased at higher concentration. At 100 μg/ml ibuprofen, PG synthesis and release was inhibited by 90 and 100% and cell growth by 64 and 66% in NMU and RBA cells, respecively. There was no obvinous dse-response relationship between ibuprofen concentration and cell growth inhibition in either cell line.
These results underline the importance of the serum component of growth medium when analyzing PG production in vitro and suggest that the epithelial cell components of experimental mammary tumors are capable of producing physiogically relevant amounts of PGs.
Key wordsmammary tumor cell culture prostaglandin production
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