6-Aminonicotinamide induces G1 arrest by elevating p27kip1 as well as inhibiting cdk2, cyclin E and p-Rb in IMR32 neuroblastoma cell line

Abstract The effects of 6‐aminonicotinamide (6‐AN) on viability of IMR32 neuroblastoma cells in the presence of ATP or NAD+ have been investigated. 6‐AN caused marked reduction in cell viability and similar observations were also made with cells treated with 6‐AN+ATP. However, cells treated with 6‐AN+NAD+ showed cell viability similar to untreated cells. Morphologically, 6‐AN and 6‐AN+ATP treated cells showed loss of neurites, polyhedric shapes, shrinkage of cell bodies and formation of lysed cells, while 6‐AN+NAD+ cells did not show any such changes. The flow cytometry analysis demonstrated that 6‐AN increased cell population in G0/G1 phase and decreased cell population in S and G2/M phase following a 72 h exposure. Western blot analysis showed that 6‐AN stimulated a substantial increase in the level of the cdk inhibitor p27kip1, but lowered the levels of cdk2, cyclin E and p‐Rb. However, cdc25A and p53R2 were not significantly affected. Immunofluorscence staining of p27kip1, cdk2, cyclin E and p‐Rb reve...