Preparation of a Monoclonal Antibody Specific for 1‐Methyladenosine and Its Application for the Detection of Elevated Levels of 1‐Methyladenosine in Urines from Cancer Patients

A monoclonal antibody specific for a modified nucleoside, 1‐methyladenosine, was prepared and characterized. This antibody, termed AMA‐2, reacts with 1‐methyladenosine and 1‐methyladenine but not with other nucleosides, particularly methylated adenosines other than 1‐methyladenosine and methylated guanosines, tested in this investigation. In our experiments, AMA‐2 was used in an enzyme‐linked immunosorbent assay (ELISA) system for the quantitation of the levels of 1‐methyladenosine in urine. Sensitivity was in the picomole range and accuracy was nearly equal to that of the high‐performance liquid chromatography (HPLC) assay system. Urinary levels of 1‐methyladenosine in healthy donors and patients with various advanced cancers were determined by the inhibition ELISA. The amount of 1‐methyladenosine in urine of 33 healthy donors was 1.91±0.66 nmol/μmol creatinine. In 54% (51/94) of patients, urinary 1‐methyladenosine was elevated above the mean plus 2 standard deviations for the healthy donors (3.23 nmol/μmol creatinine). In patients with leukemia, esophageal cancer, stomach cancer, colon cancer, and bladder cancer, urinary levels of 1‐methyladenosine were significantly elevated. In patients with leukemia, urinary 1‐methyladenosine levels changed almost in parallel with the change in the clinical response during chemotherapy. These results suggest that urinary 1‐methyladenosine might be useful in monitoring the effectiveness of therapy.