Prostatic Neoplasms: Chen CY

Chen CS, Wang YC, Yang HC, Huang PH, Kulp SK, Yang CC, Lu YS, Matsuyama S, Chen CY, Chen CS. · Division of Medicinal Chemistry, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, USA. · Cancer Res. · Pubmed #17545612 links to  free full text

Abstract: This study reports a histone deacetylation-independent mechanism whereby histone deacetylase (HDAC) inhibitors sensitize prostate cancer cells to DNA-damaging agents by targeting Ku70 acetylation. Ku70 represents a crucial component of the nonhomologous end joining repair machinery for DNA double-strand breaks (DSB). Our data indicate that pretreatment of prostate cancer cells with HDAC inhibitors (trichostatin A, suberoylanilide hydroxamic acid, MS-275, and OSU-HDAC42) led to increased Ku70 acetylation accompanied by reduced DNA-binding affinity without disrupting the Ku70/Ku80 heterodimer formation. As evidenced by increased Ser(139)-phosphorylated histone H2AX (gammaH2AX), impaired Ku70 function diminished cellular capability to repair DNA DSBs induced by bleomycin, doxorubicin, and etoposide, thereby enhancing their cell-killing effect. This sensitizing effect was most prominent when cells were treated with HDAC inhibitors and DNA-damaging agents sequentially. Mimicking acetylation was done by replacing K282, K317, K331, K338, K539, or K542 with glutamine via site-directed mutagenesis, which combined with computer docking analysis was used to analyze the role of these lysine residues in the interactions of Ku70 with DNA broken ends. Mutagenesis of K282, K338, K539, or K542 suppressed the activity of Ku70 to bind DNA, whereas mutagenesis of K317 or K331 with glutamine had no significant effect. Moreover, overexpression of K282Q or K338Q rendered DU-145 cells more susceptible to the effect of DNA-damaging agents on gammaH2AX formation and cell killing. Overall, the ability of HDAC inhibitors to regulate cellular ability to repair DNA damage by targeting Ku70 acetylation underlies the viability of their combination with DNA-damaging agents as a therapeutic strategy for prostate cancer.

Zhu T, Guo J, Collins L, Kelly J, Xiao ZJ, Kim SH, Chen CY. · Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. · Br J Cancer. · Pubmed #17262078 links to  free full text

Abstract: It is known that polysaccharides extracted from the Phellinus linteus (PL) mushroom possess antitumour activity. We previously have demonstrated that high doses of PL render murine or human lung cancer cells susceptible to apoptosis. However, the molecular mechanisms of PL-mediated apoptosis have not been fully explored. In this study, we demonstrate that LNCaP cells expressing the androgen receptor (AR) are highly susceptible to apoptosis in response to treatment with high doses of PL. In this process, caspase 8 and its downstream effectors (such as BID), as well as ER stress-related, apoptotic signalling, are activated. In contrast, a moderate amount of apoptosis occurs in PC3 cells (that lack AR) after the same treatment, which does not activate ER-mediated apoptotic signalling. We also show that, in the process of PL-induced apoptosis, caspase 2 is induced in LNCaP cells, but not in PC3 cells. However, LNCaP cells that express a mutated AR or LNCaP cells treated with a caspase 2 inhibitor blocked ER stress-induced apoptotic signals. The magnitudes of the induction of apoptosis in these cells are comparable with what occurred in the PC3 cells. The data demonstrate that high doses of PL activate the AR-dependent and independent apoptotic pathways. Our study also suggests that caspase 2 is a key target in the determination of the susceptibility of prostate cancer cells to PL-induced apoptosis.

Kulp SK, Chen CS, Wang DS, Chen CY, Chen CS. · Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210-1291, USA. · Clin Cancer Res. · Pubmed #16951239 links to  free full text

Abstract: PURPOSE: To assess the antitumor effects of a novel phenylbutyrate-derived histone deacetylase (HDAC) inhibitor, (S)-HDAC-42, vis-à-vis suberoylanilide hydroxamic acid (SAHA) in in vitro and in vivo models of human prostate cancer. EXPERIMENTAL DESIGN: The in vitro effects of (S)-HDAC-42 and SAHA were evaluated in PC-3, DU-145, or LNCaP human prostate cancer cell lines. Cell viability, apoptosis, and indicators of HDAC inhibition were assessed. Effects on Akt and members of the Bcl-2 and inhibitor of apoptosis protein families were determined by immunoblotting. Immunocompromised mice bearing established s.c. PC-3 xenograft tumors were treated orally with (S)-HDAC-42 (50 mg/kg q.o.d. or 25 mg/kg q.d.) or SAHA (50 mg/kg q.d.) for 28 days. In vivo end points included tumor volumes and intratumoral changes in histone acetylation, phospho-Akt status, and protein levels of Bcl-xL and survivin. RESULTS: (S)-HDAC-42 was more potent than SAHA in suppressing the viability of all cell lines evaluated with submicromolar IC50 values. Relative to SAHA, (S)-HDAC-42 exhibited distinctly superior apoptogenic potency, and caused markedly greater decreases in phospho-Akt, Bcl-xL, and survivin in PC-3 cells. The growth of PC-3 tumor xenografts was suppressed by 52% and 67% after treatment with (S)-HDAC-42 at 25 and 50 mg/kg, respectively, whereas SAHA at 50 mg/kg suppressed growth by 31%. Intratumoral levels of phospho-Akt and Bcl-xL were markedly reduced in (S)-HDAC-42-treated mice, in contrast to mice treated with SAHA. CONCLUSIONS: (S)-HDAC-42 is a potent orally bioavailable inhibitor of HDAC, as well as targets regulating multiple aspects of cancer cell survival, which might have clinical value in prostate cancer chemotherapy and warrants further investigation in this regard.

Collins L, Zhu T, Guo J, Xiao ZJ, Chen CY. · Department of Pathology, K522, Boston University School of Medicine, 80 East Concord Street, Boston, MA 02118, USA. · Br J Cancer. · Pubmed #16868541 links to  free full text

Abstract: It has been demonstrated that the Phellinus linteus (PL) mushroom, which mainly consists of polysaccharides, possesses antitumour activity. The mechanisms of PL against malignant growth remain unknown. The anticancer drug doxorubicin (Dox) has been shown to induce apoptosis via initiating a caspase cascade. In this investigation, we tested the effect of PL on Dox-induced apoptosis in prostate cancer LNCaP cells. We showed that PL or Dox, at relatively low doses, does not induce apoptosis in the cells. However, combination treatment with low doses of PL and Dox results in a synergistic effect on the induction of apoptosis. In this apoptotic process, caspases 8, 3 and BID are cleaved, and the addition of caspase inhibitor z-VADfmk completely blocks apoptosis. In addition, JNK is activated in response to PL or the combination treatment in LNCaP cells. The suppression of JNK partially inhibits the induction of apoptosis elicited by the co-treatment. These findings indicate that PL has a synergistic effect with Dox to activate caspases in prostate cancer LNCaP cells. Our study also suggests that PL has therapeutic potential to augment the magnitude of apoptosis induced by antiprostate cancer drugs.

Guo J, Zhu T, Xiao ZX, Chen CY. · Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. · J Biol Chem. · Pubmed #17573344 links to  free full text

Abstract: An understanding of the molecular pathways defining the susceptibility of prostate cancer, especially refractory prostate cancer, to apoptosis is the key for developing a cure for this disease. We previously demonstrated that up-regulating Ras signaling, together with suppression of protein kinase C (PKC), induces apoptosis. Dysregulation of various intracellular signaling pathways, including those governed by Ras, is the important element in the development of prostate cancer. In this study, we tested whether it is possible to modulate the activities of these pathways and induce an apoptotic crash among them in prostate cancer cells. Our data showed that DU145 cells express a high amount of JNK1 that is phosphorylated after endogenous PKC is suppressed, which initiates caspase 8 cleavage and cytochrome c release, leading to apoptosis. PC3 and LNCaP cells contain an activated Akt. The inhibition of PKC further augments Akt activity, which in turn induces ROS production and the accumulation of unfolded proteins in the endoplasmic reticulum, resulting in cell death. However, the concurrent activation of JNK1 and Akt, under the condition of PKC abrogation, dramatically augment the magnitude of apoptosis in the cells. Thus, our study suggests that Akt, JNK1, and PKC act in concert to signal the intracellular apoptotic machinery for a full execution of apoptosis in prostate cancer cells.