FIG. 7.

Lack of tumor-protective effect of a topically applied, 5× dose of PrC-210 to skin directly over the subcutaneous xenograft tumors in nude mice. Panel A: B16 melanoma cell and panel B: A431 epidermoid carcinoma cell xenograft tumors in nude mice were allowed to grow 3 days post-injection to small, subcutaneous plaques, and they were then exposed to increasing doses of external radiation from a Cs¹³⁷ source. Tumors were positioned within a 1.5 × 3.0 cm hole in a one-inch-thick lead plate for tumor irradiation. The radiation doses indicated by the respective arrows in panels A and B were chosen because they gave ~70% reduction in tumor growth rate, compared to unirradiated control tumors. In a subsequent experiment, either topical vehicle (50:30:20, ethanol:propylene glycol:water) or topical vehicle containing 1850 mM PrC-210 was applied 4 times in 2 h before irradiation. In panels C and D, no significant difference was seen (P > 0.05) between radiation ± in mice treated with topical vehicle or topical, 5X PrC-210 before tumor irradiation. There were 4 nude mice in each treatment group. Mean ± SE values are plotted.