Study On Pharmacological Effects Of Anti - Tumor Drug S14161 And Its Derivative Compound BENC - 511 On Prostate Cancer

Objectives:PI3K/Akt signaling pathway is a major target for treatments of prostate cancer, and SI4161is a proven PI3K inhibitor that has been demonstrated to inhibit malignant cells such as leukemia and multiple myeloma. To improve its anti-cancer activity, we synthesized a serial of analogs based on the structural activity relationship. BENC-511, one of such analogs, displayed more potent inhibitory activity on PI3-kinases. Therefore, in the present study, we investigated the therapeutic effects of BENC-511on androgen-independent prostate cancers in comparison with S14161in both cell lines and xenograft models. This study will form a solid basis for the development of a novel anti-prostate cancer drug by targeting the PI3K signaling pathway.Methods:1. Cell proliferation of two androgen-independent prostate cancer cell lines PC3and DU145were analyzed by microscopy and MTT assays.2. Apoptosis of PC3and DU145induce by BENC-511and S14161were analyzed by flow cytometry and Western blotting;3. The modulation of the PI3K/Akt/mTOR signaling pathway was evaluated by Western blotting;4. Prostate cancer xenograft models were established by subcutaneous inoculation of PC3and DU145cells, respectively, in the right flank of nude mice. Mice were then orally administrated BENC-511or S14161. Tumor volumes and body weight were monitored every other day. Apoptosis and Akt activation in these tumors were also measured by Western blotting using specific antibodies;5. To evaluate the effect of PTEN on the anti-prostate cancer activity of BENC-511, PTEN expression was restored in a PTEN-deficient PC3cells by transfecting a PTEN plasmid into PC3cells followed by BENC-511treatment and Western blotting assay.Results: 1. S14161and BENC-511inhibited the proliferation of prostate cancer cells PC3and DU145in both time-and concentration-dependent manners. BENC-511was more potent in inhibiting prostate cancer proliferation and in inducing apoptosis in both cell lines. In comparison, PC3was more sensitive than DU145;2. Both BENC-511and S14161cleaved PARP and Caspase-3, which are the signature proteins of apoptosis, in both cell lines in a concentration-dependent manner. Consistent with the inhibited cell proliferation and induced apoptosis, more PARP and Caspase-3were cleaved in PC3cells, especially by the treatment of BENC-511;3. Both BENC-511and S14161downregulated the PI3K/Akt/mTOR signaling pathway. BENC-511and S14161inhibited the activation of Akt activated by EGF-1in both cell lines. Further studies demonstrated that both BENC-511and S14161inhibited the phosphorylation of both Akt, mTOR and p70S6K in24hrs, but did not downregulated the expression of the total Akt, mTOR or p70S6K proteins. Restoration of PTEN in PTEN-deficient PC3cells partly abolished apoptosis induced by BENC-511because PARP cleavage was decreased.4. The in vivo xenograft studies indicated that PC3and DU145tumor growth was inhibited by both compounds, and the average tumor sizes in BENC-511-treated groups were smaller than S14161-treated mice, which were smaller than that of the vehicle-treated ones. Western blotting assays revealed that Akt activation in the tunor tissues was inhibited by BENC-511and apoptosis was seen in these tumors after BENC-511treatment because PARP was induced to cleave.Conclusions:S1416and BENC-511can significantly induce apoptosis of both PC3and DU145cells by inhibiting the PI3K/Akt signaling pathway. BENC-511displays more potent activities against prostate cancer, especially in the PTEN-deficient prostate cancers which was demonstrated in both cell lines and xenograft models. Because of its potent anti-prostate cancer activity and low toxicity, BENC-511could be developed as a novel drug especially for the androgen-independent and PTEN-deficient prostate cancers.