|Wang, Thomas - Tom|
Submitted to: Carcinogenesis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2001
Publication Date: N/A
Interpretive Summary: Prostate cancer is a leading cause of death in American men. One strategy for prevention of prostate cancer is to administer certain derivatives of vitamin A (retinoids) as chemopreventive agents. We exposed prostate cancer cells to one of these vitamin A derivatives, N-4-(hydroxyphenyl) retinamide, also known as 4- HPR. Compared to non-treated cells, 4-HPR treatment caused the prostate cancer cells to die through programmed cell death (apoptosis). The mechanism by which 4-HPR induced cell death was by reducing the synthesis of, cyclophilin D, a protein associated with normal function of mitochondria. This information will be useful to scientists who study the influence of diet on cancer.
Technical Abstract: To explore the mechanisms underlying the pro-apoptotic effects of the synthetic retinoid N-4-(hydroxyphenyl) retinamide (4-HPR) on LNCap human prostate cancer cells, we used the differential display-polymerase chain reaction(DD-PCR) technique to identify 4-HPR-responsive genes. RNA extracted from LNCaP cells that had been treated for 24 h with 4-HPR at a dose (2.5 uM) optimal for apoptosis induction was used for DD-PCR analysis using random primers. A differentially expressed 115-basepair(bp) fragment was cloned and sequenced, then identified in GenBank as having a high degree of homology with several members of the cyclophilin gene family. Northern blot analyses using specific probes for cyclophilin A, cyclophilin D, and the cloned 115-bp fragment were performed on RNA extracted from LnCaP cells and MCF-7 human breast cancer cells treated with 4-HPR, N-acetylcysteine(NAC, an anti-oxidant), 4-HPR plus NAC, cyclosporin A, R-1881 (a synthetic androgen), dehydroepian- drosterone, all-trans retinoic acid, or prednisone. 4-HPR down regulated the transcript detected by the 115-bp fragment. expression patterns detected by the 115-bp fragment and cyclophilin D probes were identical in response to each treatment; none of these treatments affected cyclophilin A expression. Furthermore, expression of mRNA transcripts detected by the 115-bp fragment and cyclophilin D probes correlated with the generation of reactive oxygen species (ROS), as detected by measurement of 2,7-dichlorofluorescein oxidation. Members of the cyclophilin gene family, such as cyclophilin D (a component of mitochondrial permeability transition pore previously linked with oxidative stress and apoptosis), may play a role in the ROS-mediated apoptotic effects of 4-HPR.