Cellular pharmacology of d-3-azido-3-deoxy-myo-inositol, an inhibitor of phosphatidylinositol signaling having antiproliferative activity

d-3-Azido-3-deoxy-myo-inositol (3AMI) is an inhibitor of the growth of v-sis-transformed NIH 3T3 cells but not of wild-type NIH 3T3 cells, whose effects may be mediated through the phosphatidylinositol-3′-kinase pathway. We studied some properties of the cellular pharmacology of 3AMI using high-specific-activity [³H]-3AMI. The uptake of [³H]-3AMI by wild-type NIH 3T3 and v-sis NIH 3T3 cells was similar. [³H]-3AMI was a substrate for phosphatidylinositol synthetase, with the maximal velocity (V_max) being 1.0 nmol min^-1 mg^-1 and the Michaelis constant (K_m) being 23 m M. Corresponding values obtained for [³H]-myo-inositol as a substrate were 5.5 nmol min^-1 mg^-1 and 3.2 m M. [³H]-3AMI was incorporated into the cellular inositol lipids of v-sis NIH 3T3 cells to a similar extent as that observed for [³H]-myo-inositol but was not incorporated into the inositol lipids of wild-type NIH 3T3 cells. The [³H]-3AMI incorporated by the v-sis NIH 3T3 cells was present in the phosphatidylinositol and phosphatidylinositol phosphate fractions but not in bisphosphorylated phosphatidylinositol. myo-Inositol antagonized the growth-inhibitory effects of 3AMI. The v-sis NIH 3T3 cells were found to be more sensitive than the wild-type NIH 3T3 cells to growth inhibition (without 3AMI) caused by the removal of myo-inositol from the medium. The results of the study suggest that 3AMI is an antimetabolite of myo-inositol. The relative sensitivity of v-sis NIH 3T3 and some other cells to 3AMI may be a reflection of increased myo-inositol requirements for the growth of these cells as compared with wild-type NIH 3T3 cells.