HUMAN-PLATELETS EXERT CYTO-TOXIC EFFECT ON TUMOR-CELLS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 65  (5) , 1252-1255
Abstract
Monocytes are thought to play a role in host resistance to tumor cell growth in animals and humans. Platelets are known to be involved in tumor metastases. To investigate the interaction of these 2 cell types and their effect on tumor cells, human monocytes and platelets were examined using an in vitro monocyte-tumor cell cytotoxicity assay. Monocytes alone resulted in 32% .+-. 1.5 (mean .+-. SEM [standard error of the mean]) tumor cell kill. When platelets were added to monocytes in a 1:1 ratio, an increase in cytotoxicity to 61% .+-. 3.2 was observed. The cytotoxicity noted when platelets were added to a fixed number of monocytes and tumor cells was dependent on the number of platelets added. A decrease in cytotoxicity from 32% .+-. 1.5 to 12% .+-. 2.3 was observed when contaminating platelets were removed from monocyte preparations. Platelets added to tumor cells in the absence of any monocytes were also toxic, resulting in a maximum kill of 95% at a 4:1 platelet/tumor cell ratio. Secreted products of freshly isolated platelets may be responsible for much of the observed cytotoxicity, since supernatants from the platelets were toxic for tumor cells. Platelets pretreated with a cyclooxygenase inhibitor (ASA) or a lipoxygenase inhibitor had decreased cytotoxicity compared with untreated platelets. Products of platelet arachidonate metabolism are toxic for tumor cell lines. The role of the platelet must be considered when studying monocyte-tumor cell cytotoxicity.