Oral Administration of a Kampo (Japanese Herbal) Medicine Juzen‐taiho‐to Inhibits Liver Metastasis of Colon 26‐L5 Carcinoma Cells

We have investigated the inhibitory effect of oral administration of Juzen‐taiho‐to, a Kampo Japanese herbal medicine, on liver metastasis by the inoculation of a liver‐metastatic variant (L5) of murine colon 26 carcinoma cells into the portal vein. Oral administration of Juzen‐taiho‐to for 7 days before tumor inoculation resulted in dose‐dependent inhibition of liver tumor colonies and significant enhancement of survival rate as compared with the untreated control, without side effects. We also found that liver metastasis of L5 cells was enhanced in BALB/c mice pretreated with anti‐asialo GM1 serum or 2‐chloroadenosine, and in BALB/c nu/nu mice, compared to normal mice. This indicates that NK cells, macrophages, and T‐cells play important roles in the prevention of metastasis of tumor cells. Juzen‐taiho‐to significantly inhibited the experimental liver metastasis of colon 26‐L5 cells in mice pretreated with anti‐asialo GM(1) serum and untreated normal mice, whereas it did not inhibit metastasis in 2‐chloroadenosine‐pretreated mice or T‐cell‐deficient nude mice. Oral administration of Juzen‐taiho‐to activated peritoneal exudate macrophages (PEM) to become cytostatic against the tumor cells. These results show that oral administration of Juzen‐taiho‐to inhibited liver metastasis of colon 26‐L5 cells, possibly through a mechanism mediated by the activation of macrophages and/or T‐cells in the host immune system. Thus, Juzen‐taiho‐to may be efficacious for the prevention of cancer metastasis.