Identification of 'non-proliferating' B16 melanoma cells using monoclonal antibody (AD203) against the M1 subunit of ribonucleotide reductase.

Ribonucleotide reductase catalyses a critical reaction in DNA synthesis. Its M1 subunit is present during all proliferative phases of the cell cycle, but apparently not in the quiescent phase G0. We have used a monoclonal antibody (AD203) directed against the M1 subunit to distinguish immunocytochemically proliferating from non-proliferating cultured B16 mouse melanoma cells during exponential growth. The presumption that AD203 unstained cells constituted a non-proliferating fraction was tested by simultaneously counting the cells that failed to incorporate bromodeoxyuridine (BrdU) into DNA during a prolonged BrdU exposure. The proportion of cells which did not incorporate BrdU was found to correlate closely with the proportion not staining with AD203 and therefore presumably lacking the M1 subunit. The respective morphological features of AD203 stained and unstained cells were found not to differ significantly.