Incorporation of an (125)I-labeled hexa-iodinated diglyceride analog into low-density lipoprotein and high specific uptake by cells of cervical carcinoma cell lines.

The feasibility of using low-density lipoprotein (LDL) to deliver cytotoxic drugs to tumor cells has been explored since the 1980s, when cells of a number of cancer cell lines were found to have higher LDL receptor activity than normal cells. Such differential uptake between tumor and normal cells may provide a unique opportunity to use LDL as a tumor-specific carrier of radiopharmaceuticals for the clinical management of cancer. In this study, an (125)I-labeled hexa-iodinated diglyceride analog, 1, 3-dihydroxypropan-2-one 1,3-diiopanoate (DPIP), was synthesized and incorporated into LDL using a fusion technique. It was found that approximately 500 [(125)I] DPIP molecules were incorporated into each LDL particle. Cells of three human cervical tumor cell lines, HeLa, SiHa and C-33A, were used to examine the cellular uptake of the [(125)I]DPIP-LDL conjugate. It was shown that the [(125)I]DPIP-LDL conjugate was specifically bound to and taken up by cervical tumor cells through an LDL receptor-mediated endocytosis pathway. The results suggest that LDL may be a selective carrier for delivering hydrophobic radiopharmaceuticals to cancer cells and particularly for the diagnosis of cervical tumors.