Dietary lutein modulates expression of prostate cancer biomarker genes in human prostate cancer cell line

Prostate cancer is the second leading cause of death from malignancies in men and is the most commonly diagnosed cancer in the United States. Epidemiological studies have shown the inverse relationship between consumption of various carotenoids and the risk of prostate cancer. Lutein is a fat-soluble, oxycarotenoid present in human serum and is also present in the liver, colon, lung and prostate tissues. Lutein is not synthesized by the human body and is primarily consumed from dark-green leafy vegetables such as kale and spinach, as well as from egg yolks, avocado, corn and fruits like orange and kiwi. Lutein has gained popularity through its role in preventing age-related macular degeneration (AMD). Anti-inflammatory activity of lutein has also been the focus of a number of in vitro and in vivo studies. Recently much attention has focused on the role of lutein against various cancers including prostate cancer, however no mechanism of action was determined.;Our objective is to determine whether lutein modulates prostate cancer biomarker genes in hormone refractory prostate cancer (PC-3) cell lines using Oligo GEArrayRTM DNA Microarray, which contains 263 genes involved in the progression and diagnosis of prostate cancer. PC-3 cells were treated with 10 muM non-toxic concentrations of lutein as determined by MTT cell viability assay. Isolated RNA was reverse-transcribed to cDNA, transcribed to cRNA and hybridized with microarrays. Microarray results demonstrated the down-regulation of epidermal growth factor receptor (EGFR), insulin-like growth factor 1 receptor (IGF1R), breast cancer gene 1 (BRCA1), cyclin dependant kinase 5 (CDK5), kallikrein 14 (KLK14) and prostate cancer antigen 3 (PCA3). Microarray results also showed the up-regulation of ras association domain family member 1 (RASSF1) and glutathione S-transferase pi 1 (GSTP1). Modulated genes were validated by Real-Time PCR and demonstrated down-regulation of IGF1R, EGFR, BRCA1, CDK5, KLK14 and PCA3 by 83%, 60%, 50%, 44%, 41% and 40% respectively. Similarly, up-regulated genes were also validated by Real-Time PCR and results showed GSTP1 and RASSF1 up-regulated by 82% and 70%. Modulated genes were further analyzed at the translational level using Western Blot. Among all the prostate cancer biomarker genes, IGF1R, EGFR and GSTP1 were most significantly modulated in Real-Time PCR analysis. Western blot analysis demonstrated that lutein treatment down-regulated the protein expression of IGF1R and EGFR by 40.4% and 33.1% while up-regulating GSTP1 by 30.0%. These results demonstrate the potential of lutein to modulate a number of key biomarker genes involved in human prostate cancer proliferation, differentiation, angiogenesis and apoptosis.