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[Induction of apoptosis in prostate cancer cell line PC-3 by BBSKE, a novel organoselenium compound, and its effect in vivo].

OBJECTIVE
To investigate the effects of BBSKE (1,2-[bis (1,2-benzisoselenazolone-3 (2H)-ketone)]ethane), a novel organoselenium compound, on the proliferation and apoptosis of the prostate cancer cell line PC-3, and to study its effect on the growth of prostate cancer in vivo.


METHODS
Prostate cancer cells of the cell line PC-3 was cultivated in media with different concentrations of BBSKE and cisplatin. The inhibition of proliferation was measured by colorimetric MTT assay. The morphologic changes were observed by fluorescence microscopy, DNA fragmentation was visualized by agarose gel electrophoresis, and the DNA degradation was determined by flow cytometry. Western blot analysis was used to identify the expression of bcl-2 and bax. The activity of caspase-3 was determined by a micro-ELISA reader. Mouse prostate cancer cells of the TRAMP-C2 line were cultured and then injected subcutaneously into 2 male C57BL/6 mice to establish the animal model. Then the 2 mice were killed to collect the cancer cells. Twenty-four mice were injected intraperitoneally with single cell suspension of TRAMP-C2 cell and then divided into 3 groups of 8 mice undergoing intraperitoneal injection for 7 days: BBSKE group (BBSKE was administered at the dosage of 25mg/kg/day), cisplatin group (cisplatin 2mg/kg/d was injected), and control group (pure solvent was injected). Three weeks after the mice were killed and the tumors were taken out to calculate the inhibition rate.


RESULTS
BBSKE inhibited the growth of the PC-3 cells dosage-dependently with a value of IC(50) of 17.90 micro mol/L after a 48 h exposure, higher than that in the case of cisplatin (15.00 micro mol/L). After exposure of PC-3 cells to BBSKE at the dosage of 20 micro mol/L for 48 hours the apoptosis rate was 26.32%, significantly higher than that of the control group (1.75%, P < 0.01). The expression of bcl-2 was decreased and the expression of bax remained almost unchanged along with the increase of BBSKE concentration. The activity of caspase 3 in the subgroup of BBSKE of the concentration of 5 micro mol/L remained almost unchanged, and was increased to 3.65 +/- 0.57 and 4.39 +/- 1.01 respectively in the BBSKE 10 micro mol/L and 20 micro mol/L subgroups, both significantly higher than that of the control group (both P < 0.05). In the in vivo experiment, the growth of tumor was significantly inhibited by BBSKE with an inhibition rate of 40% and the inhibition rate of the cisplatin group was 48%.


CONCLUSION
The novel organoselenium BBSKE inhibits the proliferation of PC-3 cell and promote its apoptosis, probably through downregulating the expression of bcl-2 and the activity of caspase-3. BBSKE also inhibits the growth of prostate cancer in vivo.