Recent advances in understanding the antineoplastic mechanisms of farnesyltransferase inhibitors

Farnesyltransferase (FTase) inhibitors (FTI) have broad anti-neoplastic actions targeting both cancer cells and mesenchymal cells involved in tumor angiogenesis. The small GTPases H-Ras, Rheb, and RhoB and the centromere proteins CENP-E and CENP-F are relevant targets of farnesylation inhibition; however, their relative importance in the antineoplastic effect of FTIs may vary in different cell types at different stages of the cell cycle and at different stages in oncogenesis. Three recent studies argue that Ras-independent and perhaps even FTase-independent properties are important to the antineoplastic action of this class of drugs. In mice, genetic ablation of FTase does not abolish the oncogenic activity of Ras, limiting the original conception of FTIs as an effective means to target Ras in cancer cells. FTase may not be the sole molecular target of these agents, and one study has suggested that FTIs act by targeting geranylgeranyl transferase II. Lastly, we have obtained evidence that induction of reactive oxygen species and reactive oxygen species-mediated DNA damage by FTIs may be critical for their antineoplastic action as a class. Together, these findings may alter thinking about how to apply FTIs in the clinic.