Low expression of cyclin D2 in G2/M-arrested and transformed proliferating Balb/3T3 cells

At present, the effect of cyclin D2 implicated in cell cycle regulation, differentiation, and oncogenic transformation is not fully confirmed. To better elucidate the role of cyclin D2 in controling the cell proliferation, cyclin D2 expression level was determined at the early initiation and promotion stages during the in vitro two-stage transformation process of Balb/3T3 A31 cells. N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)-induced G2/M-arrested cells expressed low level of cyclin D2 mRNA, while the contact-inhibited nonproliferating cells expressed high level of cyclin D2 mRNA. In the transformed proliferating cells at the promotion stage, cyclin D2 mRNA was not expressed. These data suggest that cyclin D2 expression may be associated with the type of growth arrest and nonproliferating state, but not with the cell proliferation and transformation.