Enhancement of chemotherapeutic effects by recombinant human granulocyte colony-stimulating factor on implanted mouse bladder cancer cells (MBT-2).

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) was administered intraperitoneally in combination with multidrug chemotherapy using methotrexate (M), vinblastine (V), doxorubicin (A), and cisplatin (C, or for the combination, MVAC) to C3H/He mice (5-week-old females) after experimental carcinoma, MBT-2, a transplantable transitional cell carcinoma of the urinary bladder had been implanted. The effects of therapy were studied. The animal groups consisted of: (1) control (no drug administration), (2) rhG-CSF (100 micrograms/kg/d, from days 8 through 42 after MBT-2 implantation, except for the days when MVAC was administered), (3) high-dose MVAC (2 mg/kg of M, 0.2 mg/kg of V, 2 mg/kg of A, and 4 mg/kg of C once a week for 3 weeks), (4) low-dose MVAC (one-quarter of the high dose), (5) high-dose MVAC with rhG-CSF, and (6) low-dose MVAC with rhG-CSF. In an in vitro system, rhG-CSF did not show any effect on the proliferation of MBT-2 cells or exert any influences on A's tumor proliferation-suppressing action on MBT-2. However, in an in vivo system, concomitant administration of rhG-CSF significantly enhanced the tumor-suppressing effect of the MVAC therapy, as did rhG-CSF alone. The greatest effect was observed in the group receiving high-dose MVAC plus rhG-CSF. These result suggested that rhG-CSF-stimulated granulocytes may exert antitumor activity on tumor cells severely damaged by chemotherapeutic agents at a relatively high concentration. The survival rate was improved to some degree even by administration of rhG-CSF alone. Although further study is required to elucidate the action mechanism of rhG-CSF, these results suggest that rhG-CSF may be useful clinically to enhance the activity of antitumor agents and not only through its ability to alleviate granulocytopenia or prevent its development.