ABSTRACT
Hexamethylmelamine (HMM) has previously been shown to be active against ovarian, breast and small cell lung cancer. However HMM dose not have aromatase-inhibitory activity. A newly developed HMM derivative, 2-N,N-dimethylamino-4, 6-bis (1-H-imidazol-1-yl)-1,3,5-triazine (SAE9), was found to have direct antitumor activity as well as aromatase-inhibitory activity. The direct antitumor activity on breast carcinoma cell lines (MCF-7, R-27 and MDA-MB-231) was assessed using the 3-(4,5-dimethylthiazol-2yl)-2, 5-diphenyl tetrazolium bromide (MTT) on cells growing in monolayer culture. The 50% inhibitory concentrations (IC50) of SAE9 were found to be approximately 10(-4) M for each cell line, roughly equivalent to those of HMM. When the aromatase-inhibitory effect was assessed using a human placental aromatase-inhibitory assay, the IC50 of SAE9 was 5.5 x 10(-7) M, which was superior to that of aminoglutethimide (AG) (3.8 x 10(-5) M). In a rat uterine growth model treated with androstenedione as the in vivo aromatase inhibition assay, SAE9 had an effect equivalent to that of AG. Since SAE9 has both antitumor and aromatase-inhibitory activity on breast carcinoma cell lines with estrogen dependency, this and similar non-steroidal aromatase inhibitors are thought to be promising for further study.