Through
free radical-mediated peroxidation,
cyclooxygenase (COX) can metabolize dihomo-γ-
linolenic acid (DGLA) and
arachidonic acid (AA) to form well-known bioactive metabolites, namely, the 1-series of
prostaglandins (PGs1) and the 2-series of
prostaglandins (PGs2), respectively. Unlike PGs2, which are generally viewed as proinflammatory and procarcinogenic PGs, PGs1 may possess anti-inflammatory and anti-
cancer activity. Previous studies using ovine COX along with spin trapping and the LC/ESR/MS technique have shown that certain exclusive
free radicals are generated from different
free radical reactions in DGLA and AA peroxidation. However, it has been unclear whether the differences were associated with the contrasting bioactivity of DGLA vs AA. The aim of this study was to refine the LC/MS and spin trapping technique to make it possible for the association between
free radicals and
cancer cell growth to be directly tested. Using a
colon cancer cell line, HCA-7 colony 29, and LC/MS along with a solid-phase extraction, we were able to characterize the reduced forms of radical adducts (
hydroxylamines) as the
free radicals generated from cellular COX-catalyzed peroxidation. For the first time,
free radicals formed in the COX-catalyzed peroxidation of AA vs DGLA and their association with
cancer cell growth were assessed (cell proliferation via MTS and cell cycle distribution via
propidium iodide staining) in the same experimental setting. The exclusive
free radicals formed from the COX-catalyzed peroxidation of AA and DGLA were shown to be correlated with the cell growth response. Our results indicate that
free radicals generated from the distinct radical reactions in COX-catalyzed peroxidation may represent the novel metabolites of AA and DGLA that correspond to their contrasting bioactivity.