Clastogenic action of tumor promoter phorbol-12-myristate-13 acetate in mixed human leukocyte cultures

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Abstract
The tumor promoter phorbol-12-myristate-13-acetate (PMA) induces chromosomal aberrations in mitogen stimulated human lymphocyte cultures containing monocytes, polymorphonuclear cells (PMN) and platelets. Such cultures produce a diffusible clastogenic factor (CF) in response to PMA which causes aberrations in fresh blood cultures which have not been exposed to PMA. The contribution of monocytes, PMN and platelets to CF formation was studied. Pure lymphocyte cultures (containing no platelets and maximally 1% PMN and 2% monocytes) only produced CF when they were in contact with 1-18% .times. 106 monocytes attached to plastic during PMA treatment (18.5 .+-. 5.3% mitosis with aberrations for CF produced in the presence of monocytes relative to 6.0 .+-. 4% in their absence). They also produced CF of increasing potency upon addition of 0.25-5 .times. 106 PMN (20.5 .+-. 5.9% mitosis with aberrations for CF produced in the presence of 5 .times. 106 PMN). Cultures containing 5-10 platelets/lymphocyte also formed CF upon PMA treatment. Cultures of purified monocytes and PMN were capable of producing CF in the absence of lymphocytes. The presence of bovine erythrocyte CuZn superoxide dismutase during PMA treatment decreased the activity of the resulting CF under all conditions. Catalase prevented CF production from PMN. The presence of monocytes, PMN or platelets is apparently a prerequisite for CF formation by PMA. Neoplastic tissue is usually surrounded by inflammatory leukocytes. CF produced by these cells in response to tumor promoters such as PMA may induce chromosomal damage in the neighboring tumor cells.