sFRP4 mRNA Research Articles

Membranous expression of secreted frizzled-related protein 4 predicts for good prognosis in localized prostate cancer and inhibits PC3 cellular proliferation in vitro.

Activation of the Wnt-signaling pathway is implicated in aberrant cellular proliferation in a variety of cancers. Secreted frizzled-related protein 4 (sFRP4) is a secreted protein with putative inhibitory activity of the Wnt-signaling cascade through binding and sequestering Wnt ligands. Because sFRP4 mRNA is overexpressed in prostate cancers (PCs), the aim of this study was to define the pattern of sFRP4 protein expression in normal and malignant human prostate tissue and to determine whether changes in expression were associated with disease progression and prognosis, as well as to define the phenotype of sFRP4-overexpression in an in vitro model of PC. Polyclonal antibodies were raised against a COOH-terminal peptide of sFRP4, characterized and used to assess sFRP4 protein expression in benign prostate tissue and 229 patients with clinically localized PC (median follow-up 77 months, range 1-156). In vitro studies of the function of sFRP4 overexpression were performed using PC3 cells transfected with sFRP4. Benign and malignant prostate tissue demonstrated cytoplasmic sFRP4 immunoreactivity, but there was a decrease in the expression of membranous sFRP4 in PCs compared with the hyperplastic lesions (P < 0.0001). Kaplan-Meier analysis revealed that patients whose PC expressed membranous sFRP4 in >20% of cells had improved relapse-free survival compared with those with </=20% membranous expression (P = 0.002). Moreover, membranous sFRP4 expression (P = 0.04) was an independent predictor of relapse when modeled with Gleason score (P = 0.006), pathological stage (P = 0.002), and pre-operative prostate-specific antigen levels (P = 0.004). In addition, in vitro studies demonstrated a decrease in the proliferation rate of PC3 cells transfected with sFRP4 when compared with the control PC3-empty vector cells (P < 0.0001). Decreased levels of phosphorylated glycogen synthase kinase 3beta in PC3-sFRP4 cells suggested that this phenotype is mediated by the "Wnt/beta-catenin" pathway. These data suggest that sFRP4 expression may be prognostic for localized PC, potentially as a consequence of an inhibitory effect on PC cell proliferation.

Expression and localization of secreted frizzled-related protein-4 in the rodent ovary: evidence for selective up-regulation in luteinized granulosa cells.

Secreted frizzled-related protein-4 (sFRP-4) belongs to a family of soluble proteins that have a Frizzled-like cysteine-rich domain and function as modulators of Wnt-Frizzled (Fz) signals. As several Wnts and Fz are expressed at defined stages of follicular development in rodent ovaries, these studies were undertaken to evaluate the hormone-regulated expression and localization of sFRP-4. In the mouse ovary, the expression of sFRP-4 mRNA was up-regulated in granulosa cells of large antral follicles after human chorionic gonadotropin administration and was also elevated in corpora lutea, as determined by RT-PCR and in situ hybridization analyses. In hypophysectomized rat ovaries, sFRP-4 expression was similarly induced by human chorionic gonadotropin and further up-regulated by PRL. PRL also stimulated the secretion of sFRP-4 protein from luteinized rat granulosa cells in culture. Therefore, regulation of sFRP-4 by LH and PRL may be important for modulating Fz-1, which is known to be expressed in periovulatory follicles, and Wnt-4/Fz-4, which are expressed in corpora lutea.

The role of sFRP4, a secreted frizzled-related protein, in ovulation.

Ovulation is a complex, multi-factorial event that involves the degeneration of a specific area of the follicular and ovarian surface via apoptosis. Many apoptosis related genes have been identified in the ovary. Secreted Frizzled Related Protein 4 (sFRP4) is a protein that appears to antagonize a molecular pathway for cell survival. sFRP4 gene expression is known to be upregulated with apoptosis in the ovarian corpus luteum. In this study, ovulation was hormonally induced in immature Wistar rats and their ovaries collected for analysis of apoptosis and sFRP4. TUNEL staining identified a greater amount of dying cells in the thecal layer of treated rat ovaries compared to controls. The results of 3'-end labelling revealed a significant increase (p < 0.01) in apoptosis at 12 hours following treatment compared to other time points and control. In situ hybridization exhibited a visible increase in amounts of sFRP4 mRNA expression in the thecal layers of follicles from treated rats compared to controls. Quantitative RT-PCR revealed no significant difference in sFRP4 expression levels between treated and control tissues although a clear trend towards an increase was observed in the treated group. This study demonstrates an association between sFRP4 and apoptosis in rat ovulation.

Differential expression of secreted frizzled-related protein 4 in decidual cells during pregnancy

During pregnancy, the uterus shows marked morphological and physiological changes under the regulation of ovarian steroid. To elucidate the molecular cues of these changes, we tried to identify the transcripts differentially expressed in the pregnant rat uterus by using the suppression subtractive hybridization method. Seven independent clones were isolated and one of the up-regulated genes was secreted frizzled-related protein 4 (sFRP4). sFRP4 contains a Wnt-binding domain and belongs to the secreted frizzled protein family whose members are assumed to function as modulators of the Wnt signal. The expression level of sFRP4 mRNA reached a peak in the pregnant uterus on day 12, when uterine decidualization was almost complete in the rat. In situ hybridization histochemistry revealed that sFRP4 transcripts were observed in the decidual cells. In addition, proliferating cell nuclear antigen (PCNA)-positive cells were shown to be overlapped in decidua, suggesting that sFRP4 mRNA expression was accompanied by the late phase of decidual cell proliferation. Moreover, sFRP4 and estrogen receptor-alpha transcripts were co-localized. Furthermore, we analyzed the regulation of sFRP4 by estrogen using 17 beta-estradiol-treated ovariectomized rats. sFRP4 mRNA was detected in the uterus at 48 h after estrogen treatment, especially in endometrial stroma where PCNA-positive cells were also observed. The results in this study led us to the notion that sFRP4 mRNA may be up-regulated after estrogen treatment in the late phase of uterine cell proliferation.

Place- and time-dependent expression of mouse sFRP-1 during development of the cerebral neocortex.

Wnts are a family of secreted proteins involved in multiple developmental mechanisms during nervous system development, including cell proliferation, cell migration, axon guidance and specification of cell positional information. We report here the expression of sFRP-1 mRNA, encoding a putative inhibitor of Wnt, in the developing mouse neocortex during the entire period when neurons for the neocortex are born. We show that sFRP-1 mRNA expression is spatially restricted to the proliferative zones during the period, when neurons are known to be generated in large numbers for the enlarging cortical plate.