In vitro and in vivo antineoplastic activity of a novel bromopyrrole and its potential mechanism of action.
OBJECTIVE
Many bromopyrrole compounds have been reported to have in vitro antineoplastic activity. In a previous study, we isolated N-(4, 5-dibromo-pyrrole-2-carbonyl)-L-amino isovaleric acid methyl ester (B6) from marine sponges. Here, we investigated the in vitro and in vivo antineoplastic activity of B6 and its potential mechanism.


METHODS
The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine the in vitro antineoplastic activity of B6. Flow cytometry, western blot analysis and morphological observations were used to investigate its mechanism of action. A mouse xenograft model was used to determine its in vivo activity.


RESULTS
B6 inhibited the proliferation of various human cancer cells in vitro, with highest activity on LOVO and HeLa cells. B6 also exhibited significant growth inhibitory effects in vivo in a xenograft mouse model. Acute toxicity analysis suggested that B6 has low toxicity. B6-treated cells arrested in the G1 phase of the cell cycle and had an increased fraction of sub-G1 cells. In addition, the population of Annexin V-positive/propidium iodide-negative cells increased, indicating the induction of early apoptosis. Indeed, B6-treated cells exhibited morphologies typical of cells undergoing apoptosis. Western blotting showed cleaved forms of caspase-9 and caspase-3 in cells exposed to B6. Moreover, B6-promoted Ca(2+) release and apoptosis was associated with elevated intracellular Ca(2+)concentration.


CONCLUSIONS
B6 has significant antineoplastic activity in vitro as well as in vivo. It inhibits tumour cell proliferation by arresting the cell cycle and inducing apoptosis. With its low toxicity, B6 represents a promising antineoplastic, primary compound.
Xiong
Sheng
S
Biomedical R&D Center, Guangdong Provincial Key Laboratory of Bioengineering Medicine, National Engineering Research Center of Genetic Medicine, Guangzhou, Guangdong, China. xiongsheng@jnu.edu.cn
Pang
Hui-dan
HD
Fan
Jun
J
Ge
Feng
F
Yang
Xiao-xia
XX
Liu
Qiu-ying
QY
Liao
Xiao-jian
XJ
Xu
Shi-hai
SH
D000818:Animals; D000970:Antineoplastic Agents / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D005434:Flow Cytometry; D006367:HeLa Cells; D045782:Hemiterpenes; D056945:Hep G2 Cells; D006801:Humans; D007928:Lethal Dose 50; D008297:Male; D051379:Mice; D009369:Neoplasms / Q000188:drug therapy* / Q000473:pathology; D011161:Porifera / Q000737:chemistry; D011758:Pyrroles / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D013997:Time Factors; D047368:Tumor Burden; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D045782:Hemiterpenes; C550641:N-(4,5-dibromo-pyrrole-2-carbonyl)-L-amino isovaleric acid methyl ester; D011758:Pyrroles; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D002118:Calcium