PBOX 6 is a pyrrolo-1,5-benzoxazepine (PBOX) compound, acts as a microtubule-depolymerizing agent and an apoptotic agent.

PBOX 6 is a potent apoptotic PBOX, but does not elicit a general toxic effect in a rat R2C Leydig cell line. PBOX 6 (0-25 μM, 16 h) results in dose- and time-dependent induction of apoptosis, and also causes DNA fragmentation at 10 μM in HL-60 cells. PBOX 6 (10 μM) induces apoptosis through activation of caspase 3-like proteases in HL-60 cells. PBOX 6 (10 μM) induces apoptosis and exerts an accumulation of cytochromec in the cytosol, but this effect is not triggered by oxidative stress, and is independent of peripheral-type benzodiazepine receptor (PBR) and NF-κB[1]. PBOX 6 (25 μM) induces apoptosis in MCF-7 cells through activation of caspase-7[2]. PBOX 6 (10 μM) induces the redistribution of cypA from the nucleus to the cytosol of the cell in K562 cells. PBOX 6 (10 μM) induces nucleocytoplasmic redistribution of cypA and pin1 through a JNK-dependent manner, also dependent on upstream activation of a trypsin-like serine protease, and this effect correlates with G2/M arrest in K562 cells[3].

[1]. Zisterer DM, et al. Pyrrolo-1,5-benzoxazepines induce apoptosis in HL-60, Jurkat, and Hut-78 cells: a new class of apoptotic agents. J Pharmacol Exp Ther. 2000 Apr;293(1):48-59. [2]. Mc Gee MM, et al. Caspase-3 is not essential for DNA fragmentation in MCF-7 cells during apoptosis induced by the pyrrolo-1,5-benzoxazepine, PBOX-6. FEBS Lett. 2002 Mar 27;515(1-3):66-70. [3]. Bane FT, et al. The microtubule-targeting agents, PBOX-6 [pyrrolobenzoxazepine 7-[(dimethylcarbamoyl)oxy]-6-(2-naphthyl)pyrrolo-[2,1-d] (1,5)-benzoxazepine] and paclitaxel, induce nucleocytoplasmic redistribution of the peptidyl-prolyl isomerases, cyclophilin A and pin1, in malignant hematopoietic cells. J Pharmacol Exp Ther. 2009 Apr;329(1):38-47.