ABSTRACT
BACKGROUND: The purpose of our study was to show the apoptotic and anti-proliferative effects of phytosterols as distinct from cholesterol effects on prostate cancer cell lines, and also their differential expression of caveolin-1, and a prostate specific gene, PCGEM1. METHODS: PC-3 and DU145 cells were treated with sterols (cholesterol and phytosterols) for 48h, followed by trypan blue dye exclusion measurement of cytotoxicity and MTT cell proliferation assays, respectively. Cell cycle analysis was carried out microscopically, and by propidium iodide uptake using flow cytometry. Sterol induction of oncogenic gene expression was evaluated by RT-PCR. Apoptotic cells were identified by immunocytochemistry using DNA fragmentation method, and by annexin V adhesion using flow cytometry. RESULTS: Physiological doses (16microM) of these sterols were not cytotoxic in these cells. Cholesterol-enrichment promoted mitosis (54 and 61% by microscopy; 40.8 and 34.08% by FACS analysis in PC-3 and DU145, respectively) and cell growth (P<0.05), while phytosterols suppressed mitosis (29 and 35% by microscopy; 27.71 and 17.37% by FACS analysis in PC-3 and DU145, respectively), and significantly induced tumor-suppression (P<0.05) and apoptosis. We demonstrated for the first time that cholesterols upregulated the expression of PCGEM1 even in androgen-insensitive prostate cancer cell lines. Phytosterols reversed this effect, while upregulating the expression of caveolin-1, a known mediator of androgen-dependent proto-oncogene signals that presumably control growth and anti-apoptosis. CONCLUSIONS: Phytosterol inhibition of PCGEM1 and cell growth and the overexpression of caveolin-1, suggests that poor disease prognosis anchors on the ability of caveolin-1 to regulate downstream oncogene(s) and apoptosis genes. Sterol intake may contribute to the disparity in incidence of prostate cancer, and elucidation of the mechanism for modulation of growth and apoptosis signaling may reveal potential targets for cancer prevention and/or chemotherapeutic intervention. Sterol regulation of PCGEM1 expression suggests its potential as biomarker for prediction of neoplasms that would be responsive to chemoprevention by phytosterols.
Subject(s)
Cholesterol/pharmacology , Phytosterols/pharmacology , Prostatic Neoplasms/genetics , Prostatic Neoplasms/metabolism , RNA, Untranslated/drug effects , Apoptosis/drug effects , Caveolin 1/drug effects , Caveolin 1/genetics , Caveolin 1/metabolism , Cell Cycle/drug effects , Cell Line, Tumor/cytology , Cell Line, Tumor/drug effects , Cell Line, Tumor/metabolism , Cell Proliferation/drug effects , Cell Survival/drug effects , Cells, Cultured , Cholesterol/metabolism , Flow Cytometry , Gene Expression/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Humans , Male , Phytosterols/metabolism , Proto-Oncogene Mas , RNA, Long Noncoding , RNA, Untranslated/genetics , RNA, Untranslated/metabolismABSTRACT
T cell immunity protects against diseases caused by the obligate intracellular bacterium Chlamydia trachomatis. Incidentally, host inflammatory response that includes T cells appears to also contribute to the pathogenesis of chlamydial diseases such as trachoma and tubal factor infertility (TFI). Therefore, designing effective prevention strategies requires a delineation of immune processes responsible for pathology and those mediating immunity, and identification of the immunogenetic factors predisposing to complication development. The chemokine receptor CCR5 is crucial for T cell activation and function since its deficiency causes suppression of T cell response. We investigated the hypothesis that the clearance of genital chlamydial infection in CCR5-deficient mice could be delayed in the short term; however, a beneficial effect could include protection against inflammation-related complications such as TFI. In a translational study in humans, we investigated the effect of a functional 32 bp deletion in the CCR5 gene on the risk of developing tubal pathology in Dutch Caucasian women with immunologic evidence [i.e., immunoglobulin G (IgG) responses] of chlamydial infection. When genitally-infected wild-type (WT) and CCR5 knockout (CCR5KO) mice were evaluated for microbiologic shedding of chlamydiae, there was a greater intensity of infection and delayed resolution in the knockout mice. However, compared to WT mice, the fertility of infected CCR5KO mice (measured by pregnancy rate) was only mildly affected in the short term and unaffected in the long term (70% vs 30% reduction in the short term, and 50 vs 0% in the long term, respectively). Immunobiologic analysis revealed that the diminished capacity of CCR5KO to control acute chlamydial infection correlated with the relatively low chemokine [interferon-inducible protein 10 (IP-10) and regulated upon activation normal cell expressed and secreted (RANTES)] and cytokine (mainly interferon-gamma and tumor necrosis factor-alpha) expression corresponding to a poor early T-helper I response. However, the reduced incidence of complications in the CCR5KO mice appears to correlate with the low activity of long term inflammatory mediators. Besides, the translational studies in humans revealed that among patients with positive anti-chlamydial IgG responses, tubal pathology correlated with a low incidence of CCR5delta32 deletion (7%), while women without tubal pathology had higher incidence of the CCR5delta32 deletion (31%) as compared to controls (19%). Thus, in mice and humans the inflammation associated with CCR5 function may predispose to development of complications of chlamydial infection, such as TFI.
