INHIBITION OF MICROTUBULE ASSEMBLY IN TUMOR-CELLS BY 3-BROMOACETYLAMINO BENZOYLUREA, A NEW CANCERICIDAL COMPOUND

We have synthesized a new: compound, 3-bromoacetylamino benzoylurea (3 -BAABU), which showed strong cancericidal activity by inducing irrever sible mitotic arrest and subsequently apoptosis in human T cell leukem ic cells (CEM), human biphenotypic leukemic cells (SP), a human prosta te cancer cell line (PC-3), murine melanoma cells (B-16), and murine l ymphoma/leukemia cells (EL4) in vitro with an ID50 in the range of 0.0 13-0.07 mu g/ml (0.04-0.22 mu M). Treatment of tumor cells for 12-24 h with 3-BAABU resulted in mitotic arrest at prometaphase/metaphase/ana phase, with separation and dispersion of chromosomes and with the abse nce of mitotic spindle apparatus in cytoplasm, Treatment with 3-BAABU had no cytotoxic and mitotic blocking effect in normal human lymphocyt es, proliferating fibroblast cells (3T3), or proliferating myocardial cells (MOT). Cell cycle analyses showed that most treated leukemic cel ls accumulated at M phase 12 h after treatment. By the end of 48 h of treatment, the cells underwent apoptosis with DNA fragmentation. 3-BAA BU inhibited the assembly of microtubules from tubulin but did not int erfere with the disassembly of microtubules, The presence and the posi tion of bromine and urea groups on the benzoic ring are the determinin g factors for its inhibition of microtubule assembly. Replacing bromin e with chlorine yielded much less mitotic blocking activity and increa sed the ID50 40-fold. Substitution of the urea group with ethyl ester abrogated the activity of blocking mitosis but induced apoptosis. Movi ng the bromoacetylamino group from the 3-position to the 4-position re moved blocking activity for mitosis but induced necrosis. These result s suggest that 3-BAABU possesses a unique and functional structure and is a potential agent for cancer chemotherapy.