Preferential cytoplasmic localization of p34(cdc2) in recurrent human squamous cell carcinoma after radiotherapy

Duration of the G(2)-phase delay and arrest after exposure to ionizing radiation is thought to influence radiosensitivity. The kinase activity of the p34(cdc2)-cyclin B complex and the p34(cdc2)-cyclin A complex is implicated in G(2)- to M-phase transition and in G(2)-phase arrest after exposure to ionizing radiation. We analyzed the expression level and the subcellular location of p34(cdc2), cyclin A and cyclin B in head and neck squamous cell carcinoma (SCC) tumors; samples were obtained from patients with locally nonrecurrent and recurrent tumors that had been treated by surgery and radiotherapy. No significant difference was noticed in cyclin A, cyclin B and p34(cdc2) expression. However, we noted a significant preferential cytoplasmic location of p34(cdc2) in recurring tumors compared to the nonrecurring ones (P <0.001). This abnormal location of p34(cdc2) occurs even in primary tumors in patients with recurring tumors, suggesting that a default in the activation of p34(cdc2) kinase could be implicated in clinical radioresistance. (C) 1997 by Radiation Research Society.