The
insect growth regulator diflubenzuron (DFB), which may also inhibit growth of imaginal epidermal cells in insects, was studied for antitumor activity in two mouse
tumor models of epidermal origin. DFB inhibits
chitin deposition, but the mechanisms by which DFB controls
chitin deposition or regulates growth of insect epidermal cells are unknown. A single injection of 20 mg (800 mg/kg) of DFB into C57BL/6 mice with B16
malignant melanomas or AKR mice with skin
tumors (CA 1025) induced a rapid (24 h) decrease in
tumor volume in 78% and 66% of the
tumors, respectively. In contrast, 85% of the
melanomas and 91% of skin
tumors in control mice increased in volume during the same 24-h period.
Tumor volume decreased by as much as 55% for about 1% of the
tumors, but the median decrease was 20% for both types of
tumors. Since control
tumors concommitantly increased, DFB-treated
tumors decreased, relatively, to 60% of the volume of matched control
tumors. After the initial volume decrease, both types of
tumors resumed exponential growth resulting in an average growth curve delay, calculated for 12-14 days, of about 2.0 days. Subsequent treatment of
melanomas with DFB 24 h after the initial treatment resulted in a further decrease in relative
tumor volume to 40-50% of control
tumor volume and a growth curve delay of 2.6 days. The most effective regimen used was 5 daily, 20-mg doses of DFB.
Melanomas decreased to 40% of control
tumor volume after the third injection and the mean growth curve delay was extended to 4.3 days.(ABSTRACT TRUNCATED AT 250 WORDS)