PREFERENTIAL CYTOPLASMIC LOCALIZATION OF P34(CDC2) IN RECURRENT HUMANSQUAMOUS-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 activi ty of the p34(cdc2)-cyclin B complex and the p34(cdc2)-cyclin A comple x is implicated in G(2)- to M-phase transition and in G(2)-phase arres t after exposure to ionizing radiation. We analyzed the expression lev el and the subcellular location of p34(cdc2), cyclin A and cyclin B in head and neck squamous cell carcinoma (SCC) tumors; samples were obta ined from patients with locally nonrecurrent and recurrent tumors that had been treated by surgery and radiotherapy. No significant differen ce 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). Th is abnormal location of p34(cdc2) occurs even in primary tumors in pat ients with recurring tumors, suggesting that a default in the activati on of p34(cdc2) kinase could be implicated in clinical radioresistance . (C) 1997 by Radiation Research Society.