isochaihulactone and Prostatic-Neoplasms

The androgen receptor (AR) is a main therapeutic target for treatment of prostate cancer (PCa). The natural compound isochaihulactone (K8), which has a chiral center ring and two racemic forms (E-K8 and Z-K8), has anti-tumor effects on multiple cancer types both in vitro and in vivo. Here, we determined which form of K8 contains significant tumor cytotoxicity and examined how this form regulates AR expression in PCa cells and xenografts.. We chose the androgen-dependent human PCa cell line LNCaP and the androgen-independent cell lines DU145 and PC-3 to study the anti-tumor potency and AR regulation mediated by Z-K8. We measured cell viability and used flow cytometry, RT-PCR, and Western blotting. Growth inhibition in vivo was evaluated with an LNCaP xenograft animal model.. In LNCaP cells, Z-K8 significantly repressed cell proliferation, induced apoptosis, repressed AR mRNA and protein expression in a time-dependent manner, and induced JNK phosphorylation. Furthermore, treatment with a JNK inhibitor significantly abolished Z-K8-induced AR downregulation. Z-K8 did not significantly inhibit reporter gene expression of constructs containing the AR promoter when it contained a mutated Sp1 binding site. Z-K8 also showed anti-tumor effects in the xenograft animal model.. Z-K8 not only induced LNCaP apoptosis but also reduced AR expression. These results indicate that Z-K8 may be a potential anti-tumor drug for PCa therapy.

Topics: 4-Butyrolactone; Animals; Antineoplastic Agents; Apoptosis; Benzodioxoles; Cell Line, Tumor; Cytotoxins; Gene Expression Regulation, Neoplastic; Green Fluorescent Proteins; Humans; Male; MAP Kinase Signaling System; Mice; Mice, Inbred BALB C; Mice, Nude; Prostatic Neoplasms; Receptors, Androgen; Transcription, Genetic; Xenograft Model Antitumor Assays

We explored the mechanisms of cell death induced by isochaihulactone treatment in LNCaP cells.. LNCaP cells were treated with isochaihulactone and growth inhibition was assessed. Cell cycle profiles after isochaihulactone treatment were determined by flow cytometry. Expression levels of cell cycle regulatory proteins, caspase 9, caspase 3, and PARP were determined after isochaihulactone treatment. Signaling pathway was verified by inhibitors pre-treatment. Expression levels of early growth response gene 1 (EGR-1) and nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1) were determined to investigate their role in LNCaP cell death. NAG-1 expression was knocked down by si-NAG-1 siRNA transfection. Rate of cell death and proliferation were obtained by MTT assay.. Isochaihulactone caused cell cycle arrest at G2/M phase in LNCaP cells, which was correlated with an increase of p53 and p21 levels and downregulation of the checkpoint proteins cdc25c, cyclin B1, and cdc2. Bcl-2 phosphorylation and caspase activation were also observed. Isochaihulactone induced phosphorylation of c-Jun-N-terminal kinase (JNK), and JNK inhibitor partially reduced isochaihulactone-induced cell death. Isochaihulactone also induced the expressions of EGR-1 and NAG-1. Expression of NAG-1 was reduced by JNK inhibitor, and knocking down of NAG-1 inhibited isochaihulactone-induced cell death.. Isochaihulactone apparently induces G2/M cell cycle arrest via downregulation of cyclin B1 and cdc2, and induces cellular death by upregulation of NAG-1 via JNK activation in LNCaP cells.

Topics: 4-Butyrolactone; Anthracenes; Benzodioxoles; Blotting, Western; CDC2 Protein Kinase; cdc25 Phosphatases; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin B1; Cyclin-Dependent Kinase Inhibitor p21; Dose-Response Relationship, Drug; Early Growth Response Protein 1; Growth Differentiation Factor 15; Humans; JNK Mitogen-Activated Protein Kinases; Male; Mitogen-Activated Protein Kinase 8; Mitogen-Activated Protein Kinase 9; Phosphorylation; Prostatic Neoplasms; Proto-Oncogene Proteins c-bcl-2; RNA Interference; Signal Transduction; Tumor Suppressor Protein p53