[Antitumor effect of pirarubicin (THP) against human colon cancer transplanted into nude mice and the mechanism of cell cycle progression].

Pirarubicin (THP) is a derivative of adriamycin (ADM) which has been reported to have a lower cardiotoxicity than ADM. The authors investigated the in vivo antitumor effect of THP against human colon cancer cells (RPMI 4788) xenografted into nude mice. In the model of intra-abdominal carcinomatosis, intraperitoneal administration of THP (6 mg/kg) resulted in a significant prolongation of the survival compared with the saline control group (p less than 0.01). Intravenous administration of THP (8 mg/kg) significantly inhibited tumor growth compared with the saline control group. Labeling index with bromodeoxyuridine (BrdU) of RPMI 4788 tumors treated with THP was smaller than that in the control group. Mitotic index was also smaller in the group treated with THP. Labeling index with BrdU indicates the proportion of cells in the S phase. Thus, the tumor cells in both S and M phases have decreased after treatment with THP. This change in the cell cycle progression may be due to the accumulation of G2 phase similar to in vitro study. From these results, it was suggested that the change in cell cycle progression revealed in vitro might be caused by THP in vivo.