Cysteinyl leukotriene receptor antagonists inhibit tumor metastasis by inhibiting capillary permeability.

We explored the possibility of the cysteinyl leukotriene receptor antagonists, pranlukast and montelukast, preventing tumor cell migration through both cerebral and peripheral capillaries. To study tumor cell migration through brain capillaries, male Fisher rats were cannulated via the cisterna magna under pentobarbital anesthesia. RCN9 cells labeled with a fluorescent marker PKH67 were intravenously administered following arachidonic acid administration into the subarachnoid space, and specimens of the central nervous system were collected every 30 min for 8 h. Arachidonic acid increased the fluid volume with elevated white blood cell and RCN9 cell counts. When given 2 h before arachidonic acid administration, pranlukast, but not montelukast, reduced the fluid volume and inhibited white blood cell and RCN9 cell extravasation through the brain capillary. In addition, a Lewis lung carcinoma metastasis model in mice was used to study the inhibitory effect of pranlu kast and montelukast against cancer cell extravasation through general capillaries. When mice were given food containing either pranlukast or montelukast, immediately after paw amputation, tumor metastasis was prevented by both drugs, and their survival was prolonged. These results show that pranlukast can inhibit tumor cell migration through both the brain and peripheral capillaries, whereas montelukast inhibits tumor cell migration only in the peripheral capillaries.