The extractive effects of n-butanol on the cell membrane have been extensively studied. Although shortterm effects of this alcohol were reported, a sustained action on tumor cells has not been described. It was previously shown that M3 mouse mammary adenocarcinoma cells pretreated with n-butanol exhibited a longer latency after subcutaneous inoculation into syngeneic mice. In the present study a short, 5-minute exposure of M3 cells to n-butanol (2.5% v/v) resulted in the complete inhibition of a secreted metalloproteinase activity of 105 kDa and a significant decrease in secreted urokinase (uPA) activity levels (p<0.01) measured in conditioned media after 72 hours of culture. Total cell-associated uPA activity of M3 control monolayers was composed of a membrane-bound (31%) and a cytoplasmic (69%) uPAfraction. In contrast, cell-associated uPA activity of n-butanol pretreated M3 cells was mainly composed of a cytoplasmic uPA fraction and an extremely low membrane-bound uPA fraction (<5%). Further, an impaired uPA receptor binding capacity in these monolayers was also observed (p<0.05). These findings suggest that reduced proteolysis of extracellular matrix components may lead to local changes in tumor stroma composition, resulting in an altered behavior of M3 adenocarcinoma cells when inoculated in vivo.

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