URINARY-EXCRETION OF MODIFIED NUCLEOSIDES AS BIOLOGICAL MARKER OF RNATURNOVER IN PATIENTS WITH CANCER AND AIDS

Using boronate gel affinity chromatography and reversed-phase high-per formance liquid chromatography (RP-HPLC), a method for the simultaneou s determination of 12 urinary modified nucleosides has been developed. The RP-HPLC fractions were identified by ps chromatography/mass spect rometry analysis. The HPLC quantitation of urinary nucleoside levels b efore and after surgery of cancer patients suggested that urinary 5'-d eoxy-5'-methylthioadenosine and N-[(9-beta-D-ribofuranosyl-9H-purine-6 -yl) carbamoyl]-L-threonine (t6A) levels were helpful in monitoring th erapeutic effects in cancer patients. From the fact that molar ratios of urinary N2,N2-dimethylguanosine (m2(2)G)pseudouridine (PSI) and t6A /PSI in cancer patients were lower than those of normal or post-surgic al cancer patients, the increase of rRNA content in cancer tissues gro wing rapidly was estimated using the stoichiometric relationship betwe en the ratio of the number of residues of their modified nucleoside in RNAs and the proportion of rRNA to total RNAs in average tissues of w hole body. Furthermore, from the estimation of RNA turnover using urin ary nucleoside levels, it was found that the half-lives of rRNA rather than tRNA of patients with cancer and those of both RNAs in the case of acquired immunodeficiency syndrome (AIDS) were extremely short comp ared with those of the normal. Thus, we discovered that the selected u rinary modified nucleosides were very useful as a biological marker of whole-body RNA turnover in patients with cancer and AIDS.