Scintillation scanning of malignant melanomas with radioiodinated quinoline derivatives

Abstract

Abstract The relative tissue concentrations of 14 C chloroquine were studied in 32 mice, 16 black and 16 albino, with, melanomas, at 24, 48, 72 and 96 hours after injection. An iodinated analogue of chloroquine, 4-(3-dimethylaminopropylamino)-7-iodoquinoline- 125 I (hereafter called 125 I NM-113), was synthesized, and the tissue distribution of radioactivity was then compared with that of 14 C chloroquine under similar conditions in 12 mice and in 5 hamsters with melanomas. The distribution of the same quantities of 125 I from Na 125 I was studied as a control in 12 pigmented mice with melanomas, and in 2 hamsters with melanomas. Further control animals consisted of 2 hamsters with melanomas given 100 μCi of 131 I in radioiodinated serum albumin (RISA) and in 2 hamsters 100 μCi of 197 Hg in chlormerodrin. Photoscintillation scans were performed on all hamsters with melanomas to demonstrate the location and extent of the malignant melanoma in the intact animal. The data demonstrated that a derivative of chloroquine has been synthesized and labeled with radioactive iodine without destroying the specificity of this quinoline for melanin. Furthermore, the lack of concentration of 125 I in melanin after Na 125 I and the markedly higher thyroidal 125 I concentration after Na 125 I indicate both that deiodination of 125 I NM-113 is insufficient to destroy its specificity and that the concentration of 125 I in melanin is specifically related to the labeled quinoline (NM-113). 131 I from RISA and 197 Hg from chlormerodrin also did not show specific uptake in melanin-containing tissues. The concentration ratio of 125 I from NM-113 in melanoma was sufficient in every instance to delineate the malignant melanoma by scintillation scanning.