The relationship of natural killer cells to metastasis of a transplantable prostate adenocarcinoma.

Natural killer (NK) cells have been proposed to play a significant role in the inhibition of metastasis. The prostate adenocarcinoma (PA-11) in the Lobund-Wistar (L-W) rat provides a unique model of spontaneous metastasis in which to study NK response. Cultured PA-11 tumor cells were shown to be resistant to NK lysis in vitro, and enhancement or inhibition of NK reactivity in vivo using drugs or antiserum did not change the rate or extent of metastasis evident at autopsy. Exposure to PA-11 tumor cells, supernatants from cultured tumor cells, or sera from rats with advanced PA-11 in vitro did not result in inhibition of NK activity. Exposure to PA-11 tumor cells in vivo also did not cause suppression of NK activity. These data indicate that, in the PA-11/L-W system, metastasis is independent of NK activity.