Selenoprotein P in seminal fluid is a novel biomarker of sperm quality.

Hepatically-derived selenoprotein P (SePP) transports selenium (Se) via blood to other tissues including the testes. Male Sepp-knockout mice are infertile. SePP-mediated Se transport to Sertoli cells is needed for supporting biosynthesis of the selenoenzyme glutathione peroxidase-4 (GPX4) in spermatozoa. GPX4 becomes a structural component of sperm midpiece during sperm maturation, and its expression correlates to semen quality. We tested whether SePP is also present in seminal plasma, potentially correlating to fertility parameters. Semen quality was assessed by sperm density, morphology and motility. SePP was measured by an immunoluminometric assay, and trace elements were determined by X-ray fluorescence spectroscopy. SePP levels were considerably lower in seminal plasma as compared to serum (0.4±0.1 mg/l vs. 3.5±1.0 mg/l); Se concentrations showed a similar but less pronounced difference (48.9±20.7 µg/l vs. 106.7±17.3 µg/l). Se and Zn correlated positively in seminal fluid but not in serum. Seminal plasma SePP concentrations were independent of serum SePP concentrations, but correlated positively to sperm density and fraction of vital sperm. SePP concentrations in seminal plasma of vasectomized men were similar to controls indicating that accessory sex glands are a testes-independent source of SePP. This notion was corroborated by histochemical analyses localizing SePP in epithelial cells of seminal vesicles. We conclude that SePP is not only involved in Se transport to testes supporting GPX4 biosynthesis but it also becomes secreted into seminal plasma, likely important to protect sperm during storage, genital tract passage and final journey.

Selenoprotein-P is down-regulated in prostate cancer, which results in lack of protection against oxidative damage.

BACKGROUND: Oxidative stress plays a role in prostate cancer (PrCa) initiation and development. Selenoprotein-P (SepP; a protein involved in antioxidant defence) mRNA levels are down-regulated in PrCa. The main goal of our study was to assess whether SepP protects prostate cells from reactive oxygen species (ROS) in prostate carcinogenesis. METHODS: Modification of SepP levels and ROS conditions in C3(1)/Tag-derived cell lines representing prostate epithelial neoplasia (PIN) lesions (Pr-111, with high SepP expression); and invasive tumors (Pr-14, with very low SepP expression). RESULTS: Both Pr-111 and Pr-14 cells express ApoER2 (SepP receptor), which suggests that they may uptake SepP. Pr-14 cells had much higher ROS levels than Pr-111 cells and were highly sensitive to H(2)O(2)-mediated cytotoxicity. When SepP mRNA levels were knocked down with siRNAs in Pr-111 cells, a significant increase in ROS and cell growth inhibition upon H(2)O(2) exposure was found. Subsequent administration of purified SepP in the culture medium of these cells was able to rescue the original phenotype. Similarly, administration of SepP to Pr-14 cells was able to reduce ROS concentrations. Administration of flutamide decreased SepP mRNA levels whereas dihydrotestosterone or synthetic androgens induced SepP expression, indicating the importance of androgens for SepP expression. Immunohistochemical analysis using a PrCa tissue microarray further revealed that SepP protein was reduced in 60.8% prostate tumors compared to benign prostates. CONCLUSIONS: Levels of SepP in prostate cells determine basal ROS levels and sensitivity to H(2)O(2)-induced cytotoxicity. Deregulation of SepP during prostate carcinogenesis may increase free radicals, thus promoting tumor development and de-differentiation.

Frizzled1 is a marker of inflammatory macrophages, and its ligand Wnt3a is involved in reprogramming Mycobacterium tuberculosis-infected macrophages.

Wnt/Frizzled signaling, essential for embryonic development, has also recently been implicated in the modulation of inflammatory processes. In the current study, we observed a reciprocal regulation of the Toll-like receptor (TLR)/nuclear factor-κB (NF-κB) and the Wnt/ß-catenin pathway after aerosol infection of mice with Mycobacterium tuberculosis: whereas proinflammatory mediators were substantially increased, ß-catenin signaling was significantly reduced. A systematic screen of Fzd homologs in infected mice identified Fzd1 mRNA to be significantly up-regulated during the course of infection. In vitro infection of murine macrophages led to a strong induction of Fzd1 that was dependent on TLRs, the myeloid differentiation response gene 88 (MyD88), and a functional NF-κB pathway. Flow cytometry demonstrated an elevated Fzd1 expression on macrophages in response to M. tuberculosis that was synergistically enhanced in the presence of IFN-γ. Addition of the Fzd1 ligand Wnt3a induced Wnt/ß-catenin signaling in murine macrophages that was inhibited in the presence of a soluble Fzd1/Fc fusion protein. Furthermore, Wnt3a reduced TNF release, suggesting that Wnt3a promotes anti-inflammatory functions in murine macrophages. The current data support the notion that evolutionarily conserved Wnt/Fzd signaling is involved in balancing the inflammatory response to microbial stimulation of innate immune cells of vertebrate origin.

Non-canonical HIF-1 stabilization contributes to intestinal tumorigenesis.

The hypoxia-inducible transcription factor HIF-1 is appreciated as a promising target for cancer therapy. However, conditional deletion of HIF-1 and HIF-1 target genes in cells of the tumor microenvironment can result in accelerated tumor growth, calling for a detailed characterization of the cellular context to fully comprehend HIF-1's role in tumorigenesis. We dissected cell type-specific functions of HIF-1 for intestinal tumorigenesis by lineage-restricted deletion of the Hif1a locus. Intestinal epithelial cell-specific Hif1a loss reduced activation of Wnt/ß-catenin, tumor-specific metabolism and inflammation, significantly inhibiting tumor growth. Deletion of Hif1a in myeloid cells reduced the expression of fibroblast-activating factors in tumor-associated macrophages resulting in decreased abundance of tumor-associated fibroblasts (TAF) and robustly reduced tumor formation. Interestingly, hypoxia was detectable only sparsely and without spatial association with HIF-1α, arguing for an importance of hypoxia-independent, i.e., non-canonical, HIF-1 stabilization for intestinal tumorigenesis that has not been previously appreciated. This adds a further layer of complexity to the regulation of HIF-1 and suggests that hypoxia and HIF-1α stabilization can be uncoupled in cancer. Collectively, our data show that HIF-1 is a pivotal pro-tumorigenic factor for intestinal tumor formation, controlling key oncogenic programs in both the epithelial tumor compartment and the tumor microenvironment.

A biotin derivative blocks parasite induced novel permeation pathways in Plasmodium falciparum-infected erythrocytes.

The malaria parasite Plasmodium falciparum infects human erythrocytes, and it induces an increased rate of uptake into the infected cell of a range of solutes, including essential nutrients required for parasite development. Several models have been proposed for the mechanism(s) underlying parasite-induced solute uptake, each differing with respect to the site of entry into infected cells. We show that a biotin derivative that is excluded from non-infected erythrocytes gains access to infected erythrocytes via a pathway that is inhibited by compounds shown previously to block the pathways responsible for the increased uptake of solutes. The derivative was found to bind erythrocyte cytoskeletal proteins and to hemoglobin, providing evidence that the novel pathways are in the erythrocyte membrane and allow direct access of solutes to the erythrocyte cytosol. The derivative inhibited its own uptake and blocked the parasite-induced transport of other solutes. In whole-cell patch-clamp analyses, biotinylation of infected erythrocytes caused significant decrease in a parasite-induced outward rectifying conductance. In vitro, biotinylation of trophozoite-stage parasitized erythrocytes delayed parasite development. Treatment of infected cells in the final developmental stage abrogated the parasite's ability to complete development. The data are consistent with the novel pathways playing an important role in parasite growth.

Selenoprotein P status correlates to cancer-specific mortality in renal cancer patients.

Selenium (Se) is an essential trace element for selenoprotein biosynthesis. Selenoproteins have been implicated in cancer risk and tumor development. Selenoprotein P (SePP) serves as the major Se transport protein in blood and as reliable biomarker of Se status in marginally supplied individuals. Among the different malignancies, renal cancer is characterized by a high mortality rate. In this study, we aimed to analyze the Se status in renal cell cancer (RCC) patients and whether it correlates to cancer-specific mortality. To this end, serum samples of RCC patients (n = 41) and controls (n = 21) were retrospectively analyzed. Serum Se and SePP concentrations were measured by X-ray fluorescence and an immunoassay, respectively. Clinical and survival data were compared to serum Se and SePP concentrations as markers of Se status by receiver operating characteristic (ROC) curve and Kaplan-Meier and Cox regression analyses. In our patients, higher tumor grade and tumor stage at diagnosis correlated to lower SePP and Se concentrations. Kaplan-Meier analyses indicated that low Se status at diagnosis (SePP<2.4 mg/l, bottom tertile of patient group) was associated with a poor 5-year survival rate of 20% only. We conclude that SePP and Se concentrations are of prognostic value in RCC and may serve as additional diagnostic biomarkers identifying a Se deficit in kidney cancer patients potentially affecting therapy regimen. As poor Se status was indicative of high mortality odds, we speculate that an adjuvant Se supplementation of Se-deficient RCC patients might be beneficial in order to stabilize their selenoprotein expression hopefully prolonging their survival. However, this assumption needs to be rigorously tested in prospective clinical trials.

Effects of selenium status and polymorphisms in selenoprotein genes on prostate cancer risk in a prospective study of European men.

BACKGROUND: Evidence for an association between selenium status and prostate cancer risk is still inconclusive. Anticarcinogenic effects of selenium are supposedly mediated through cellular protective and redox properties of selenoenzymes in vivo. We evaluated the association between serum selenium status and prostate cancer risk in a population with relative low selenium concentrations considering effect modification by genetic variants in selenoprotein genes. MATERIALS AND METHODS: A case-control study of 248 incident prostate cancer cases and 492 matched controls was nested within the EPIC-Heidelberg cohort. Baseline blood samples were analyzed for serum selenium and selenoprotein P concentrations and glutathione peroxidase activity. Genotyping was carried out for SEP15 (rs5859, rs540049), SEPP1 (rs3877899, rs7579), GPX1 (rs1050450), and GPX4 (rs713041). Conditional logistic regression was used to calculate adjusted odds ratios (OR) and 95% confidence intervals (95% CI). RESULTS: The OR for prostate cancer was 0.89 (95% CI, 0.79-1.01) per 10 µg/L increase of serum selenium concentration. This association was modified by rs1050450 (C>T) in GPX1 (P(interaction) = 0.03), with carriers of one or two T alleles having a significantly reduced OR of 0.87 (95% CI, 0.76-0.99). Furthermore, there was an association between rs7579 genotype in SEPP1 and prostate cancer risk (OR, 1.72; 95% CI, 0.99-2.98). CONCLUSIONS: Our results support a role of selenium and polymorphisms in selenoenzymes in prostate cancer etiology, which warrants confirmation in future studies. IMPACT: These findings might help to explain biological effects of selenium in prostate cancer development in order to overcome inconsistencies arising from former studies.

Reduced serum selenoprotein P concentrations in German prostate cancer patients.

Selenium (Se) is essentially needed for the biosynthesis of selenoproteins. Low Se intake causes reduced selenoprotein biosynthesis and constitutes a risk factor for tumorigenesis. Accordingly, some Se supplementation trials have proven effective to reduce prostate cancer risk, especially in poorly supplied individuals. Because Se metabolism is controlled by selenoprotein P (SEPP), we have tested whether circulating SEPP concentrations correlate to prostate cancer stage and grade. A total of 190 men with prostate cancer (n = 90) and "no evidence of malignancy" (NEM; n = 100) histologically confirmed by prostate biopsy were retrospectively analyzed for established tumor markers and for their Se and SEPP status. Prostate specific antigen (PSA), free PSA, total Se, and SEPP concentrations were determined from serum samples and compared with clinicopathologic parameters. The diagnostic performance was analyzed with receiver operating characteristic curves. Median Se and SEPP concentrations differed significantly (P < 0.001) between the groups. Median serum Se concentrations in the 25th to 75th percentile were 95.9 microg/L (82-117.9) in NEM patients and 81.4 microg/L (67.9-98.4) in prostate cancer patients. Corresponding serum SEPP concentrations were 3.4 mg/L (1.9-5.6) in NEM and 2.9 mg/L (1.1-5.5) in prostate cancer patients. The area under the curve (AUC) of a marker combination with age, PSA, and percent free PSA (%fPSA) in combination with the SEPP concentration, yielded the highest diagnostic value (AUC 0.80) compared with the marker combination without SEPP (AUC 0.77) or %fPSA (AUC 0.76). We conclude that decreased SEPP concentration in serum might represent an additional valuable marker for prostate cancer diagnostics.