We utilized the IND approach for investigating the three FAC analogs in human subjects to (a) assess the safety profile of the FAC probes in human subjects and (b) determine the bio-distribution of the three FAC analogs in cancer patients and evaluate whether the in vivo assay of dCK enzyme activity with PET in cancer patients correlated with the in vitro assays of dCK expression and enzyme activity from surgically excised cancer tissues. This evidence concerns the gene DCK and cancer.