Hydrogen peroxide formation and DNA base modification by tumor promoter-activated polymorphonuclear leukocytes

This report shows that generation of hydrogen peroxide (H₂O₂)by human polymorphonuclear leukocytes (PMN_s) activated wtihtumor promoters of varying potency as first and second stagepromoters correlates well with activities of these promotersin vivo. Those tested were 12-O-tetradeca-noylphorbol-13-acetate(TPA), a complete promoter, 12-0-retinoylphorbol-13-acetate(RPA), a synthetic TPA derivative almost devoid of first stageactivity in some strains of mice, and mezerein (Mez), a potentsecond stage and much weaker first stage promoter. Mez-stimulatedPMN_s produced up to four times less H₂O₂ whereas RPA-stimulatedPMN_s pro-duced up to 10 times less H₂O₂ than TPA-activated cellswhen used at concentrations between 0.5 and 15 nM to activate7.5–8.5 x 10 PMNs/ml. Phorbol, a non-promoter, was totallyinactive in this assay. Furthermore, the tumor pro-moter-activatedPMNs caused formation of 5-hydroxymethyl-2'-deoxyuridine (HMdU)and thymidine glycol (dTG) in DNA co-incubated with those cells.The amounts of modified thy-midines formed, particularly ofHMdU, correlated well with first stage tumor promoting efficacyand with the amount of H₂O₂ that was generated by promoter activatedPMNs. In comparison with TPA, Mez-or RPA-stimulated PMNs in-ducedformation of 25 or 70% less H₂O₂ and 30 or 75% less HMdU, respectively,under conditions favoring HMdU for-mation. Thus, formation ofeither H₂O₂ by tumor promoter-stimulated phagocytes or HMdUin DNA exposed to those activated cells may serve as a measureof potency as a first stage tumor promoter. Formation of modifiedbases such as HMdU in DNA might constitute the genetic changeimparted by the first stage tumor promoters.