ABSTRACT
BACKGROUND: The androgen receptor (AR) plays an important role in the development and progression of prostate cancer. Functional AR expression persists in most cases of hormone-refractory prostate cancer and may play a role clinically in the progression from hormone-responsive to hormone-refractory or advanced prostate cancer. In order to combat the progression of this disease, one needs to identify new chemotherapeutic agents with novel mechanisms of action. MATERIALS AND METHODS: In this study, we attempt to clarify the molecular mechanism by which dibenzoylmethane (DBM), a beta3-diketone, inhibits the growth of androgen-responsive human LNCaP prostate cancer cells and down-regulates expression of the AR. To this end, we treated LNCaP cells with different concentrations of DBM to monitor function and expression of AR and an AR-associated protein. RESULTS: Previous studies showed that DBM could inhibit cell proliferation in LNCaP cells by arresting the cells at the G1 phase without causing cell death. Western blot and RT-PCR/Northern blot analyses showed a reduction in AR protein and mRNA expression by DBM in a dose-dependent manner. Furthermore, stable transfections of an androgen-independent human prostate cancer cell line, transfected with a full-length human AR cDNA sequence, showed that DBM down-regulated AR protein levels. DBM also inhibited the secretion of the AR-regulated tumor marker, prostate-specific antigen (PSA). Moreover, the relative binding affinity of DBM to AR was lower than that of the synthetic androgen R1881 (methyltrienolone) suggesting that DBM must suppress AR expression independent of an AR-DBM bound interaction. CONCLUSION: These data provide new insights into how DBM regulates AR function and cell growth, as well as providing promising evidence to support DBM as a chemotherapeutic agent for prostate cancer through suppression of the function of the androgen receptor.
Subject(s)
Androgen Receptor Antagonists , Antineoplastic Agents/pharmacology , Chalcones/pharmacology , Prostatic Neoplasms/metabolism , Cell Line, Tumor , Cell Proliferation/drug effects , Humans , Male , Prostate-Specific Antigen/analysis , Prostate-Specific Antigen/antagonists & inhibitors , RNA, Messenger/analysis , RNA, Messenger/metabolism , Receptors, Androgen/genetics , Receptors, Androgen/metabolismABSTRACT
This paper explores the use of proteomics as a tool for identifying protein species whose expression has been altered by dibenzoylmethane (DBM) in LNCaP cells. Although DBM, a constituent of licorice, has been shown to induce cell cycle arrest and regulate androgen receptor (AR) expression, the mechanism by which these events occur is unknown. To develop a better understanding of the effect of DBM on cancer cells, we analyzed changes in protein expression induced by DBM in LNCaP cells using two-dimensional (2-D) gel electrophoresis. The proteomic approach used to study LNCaP cells has lead to the analysis and identification of a number of protein species that increase or decrease as a result of exposure to DBM. In particular, twenty features were found to be differentially expressed in this study based on the quantitation of two separate 2-D-fluorescence difference gel electrophoresis analyses. Thirteen of these features were identified through mass spectrometric analysis. The intensity of 10 out of the 13 spots identified increased 2- to 3-fold in response to 25 micro M and 50 micro M DBM and the remaining three spots decreased 2-fold in response to the same DBM treatment. This study investigates proteomic changes induced by treatment of cells with DBM in order to develop a model for the mechanism by which DBM induces cell cycle arrest and represses AR expression.
