PURPOSE OF REVIEW: The molecular target of rapamycin, which is a member of the 
phosphoinositide 3-kinase related kinase family and a central modulator of cell 
growth, is a unique and prime strategic target for anticancer therapeutic 
development.
RECENT FINDINGS: The molecular target of rapamycin plays a critical role in 
transducing proliferative signals mediated through the phosphatidylinositol 3 
kinase and protein kinase B signaling pathways, principally by activating 
downstream protein kinases that are required for both ribosomal biosynthesis and 
translation of mRNAs of proteins that are essential for G1 to S phase traverse. 
By targeting the molecular target of rapamycin with high potency and 
specificity, the immunosuppressant and antiproliferative agent rapamycin 
inhibits signals required for cell cycle progression, cell growth, and 
proliferation. Both rapamycin and several rapamycin analogs with more favorable 
pharmaceutical properties have demonstrated impressive growth inhibitory effects 
against a broad range of human cancers in both preclinical and early clinical 
evaluations.
SUMMARY: This review discusses recent findings regarding the principal 
mechanisms of action of the rapamycins, the potential utility of these agents as 
anticancer therapeutics, clinical results to date, and developmental challenges 
that lie ahead.