“Like verapamil (10 μM) itself, three of the other …, namely, S9788 (4 μM), flunarizine (20 μM) and quinidine (30 μM), resulted in … 3-fold sensitization of vinblastine against the parental CEM cells, and comparable effects were noted in … CEM/VM-1 cells, which were not cross-resistant to vinblastine.”