[Effects of cucurbitacin B on cell proliferation and apoptosis in Hep-2 cells].
OBJECTIVE
To investigate the mechanism underlying the anticancer activity of cucurbitacin B on human laryngeal cancer.


METHODS
Hep-2 cells were treated with different concentrations of cucurbitacin B for different time. MTT assay was used to evaluate cell proliferation. Flow cytometry with PI staining and fluorescent microscopy with Hoechst 33258 staining were used to estimate cell cycle distribution and cell apoptosis. Expression of p-STAT3, cyclin B1 and Bcl-2 proteins was evaluated by Western blot assay. In vivo inhibitory effects of cucurbitacin B on tumor growth was evaluated in a nude mouse xenograft model.


RESULTS
Cucurbitacin B inhibited cellular proliferation in a dose and time dependent manner (P <0.05 or 0.01). Flow cytometry analysis showed that treatment with cucurbitacin B resulted in accumulation of cells at the G2/M phase of the cell cycle and cell apoptosis in a dose and time dependent manner (P <0.05 or P <0.01). Marked morphological changes of cell apoptosis including condensation of chromatin, nuclear fragmentation and apoptotic bodies were observed clearly by Hoechst 33258 staining. Western blot analysis demonstrated that the expression of p-STAT3, cyclin B1 and Bcl-2 proteins was suppressed significantly. In vivo studies showed that the inhibitory rates on laryngeal squamous carcinoma xenograft model were 32.43%, 43.24% and 70.27% for lower, moderate and higher dosage group, respectively.


CONCLUSIONS
Cucurbitacin B inhibited cell proliferation and induced apoptosis of Hep-2 cells by suppressing STAT3 signal pathway, down regulating the expression of cyclin B1 and Bcl-2 proteins.
Liu
Tingyan
T
Department of Otolaryngology, Clinical Medical School of Hangzhou Normal University, Hangzhou, 310015, China.
Zhang
Meixia
M
Deng
Yihui
Y
Zhang
Hongliang
H
Sun
Chunyan
C
Yang
Xiaolin
X
Ji
Wenyue
W
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D056744:Cyclin B1 / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
C534699:CCNB1 protein, human; D056744:Cyclin B1; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D014315:Triterpenes; C041246:cucurbitacin B