Effects of N1-guanyl-1,7-diaminoheptane, an inhibitor of deoxyhypusine synthase, on the growth of tumorigenic cell lines in culture.

N1-guanyl-1,7-diaminoheptane (GC7) is a potent inhibitor of deoxyhypusine synthase (DHS), the enzyme that catalyzes the first step in the hypusination of eukaryotic translation initiation factor 5A (eIF-5A). Since eIF-5A is the only known cellular substrate for DHS and GC7 has been reported to block the proliferation of CHO cells, it has been suggested that DHS may be a novel target for anti-cancer therapy. In the present study we investigated the antiproliferative effect of GC7 on several tumorigenic cell lines under various growth conditions. We found that this compound inhibits the proliferation of H9 cells in suspension culture and the growth of HeLa cells and v-src-transformed NIH3T3 cells under both anchorage-dependent and anchorage-independent conditions. Moreover, studies with NIH3T3 cells and v-src-transformed NIH3T3 cells show that GC7 inhibits the growth of both cell lines in monolayer culture with similar potency and could not reverse the transformed phenotype. In addition, the v-src-transformed cells grown under both anchorage-dependent and anchorage-independent conditions showed similar sensitivity toward GC7. These data indicate that GC7 acts as a general antiproliferative agent and does not appear to preferentially target tumorigenic cell types. Cell cycle analysis show that GC7 reduces the CHO-K1 cell population in the G1-phase of the cell cycle by 42% and increases the number of cells in the S-phase by 44%. This cell cycle distribution profile strikingly resembles the distribution of cells treated with puromycin. This result supports the hypothesis that the synthesis of a subset of proteins important for the S-phase progression of CHO-K1 cells might be dependent upon hypusinated eIF-5A. Thus the antiproliferative effect of GC7 appears to be related to its interference with the progression of cell cycle, which also provides a possible explanation for the lack of selectivity of GC7 between nontransformed and transformed cell types tested in this study.