Independent and synergic inhibition of verapamil and electric beam radiation on clonogenic growth in K562 and K562/ADM cell linesin vitro

It was first reported here that verapamil (VP) and electric beam radiation (EBR) were capable of inhibiting, independently or synergically, clonogenic growth in two kinds of K562 cell lines, adriamycin (ADM)-sensitive and ADM-resistant (K562/S and K562/ADM). Results showed that clonogenic rate (CGR) decreased by 3%–99.9% in the presence of dependent dose-ADM (3.8 μg/ml) in K562/ADM cell lines, while treated with 0.5μM–6μM of VP. VP was capable of potentiating radiosensitivity in K562/S and K562/ADM cell lines, whether before or after exposure of them to electric beam radiation, and significantly reduced CGR in these kinds of cell lines (P<0.01).