Correlation between serum prostate-specific antigen and alpha-1-antitrypsin in men without and with prostate cancer

SERPINA1 long transcripts produce non-secretory alpha1-antitrypsin isoform: In vitro translation in living cells

SERPINA1 is a well-studied serpin gene due to its dramatic impact on human health. Translation initiation at the main SERPINA1 start codon produces the only known alpha1-antitrypsin (AAT) isoform intended for secretion. AAT performs essential functions by inhibiting proteases and modulating immunity. However, SERPINA1 expression at the level of translation is not sufficiently studied. Here we hypothesize that the main SERPINA1 ORF can be alternatively translated, producing a non-secretory AAT isoform by either masking or excluding a signal peptide. We defined SERPINA1 long mRNA isoforms specific for prostate (DU145) and liver (HepG2) cell lines and studied their individual expression by in vitro assay. We found that all long transcripts produce both glycosylated secretory AAT-eGFP fusion protein and non-glycosylated intracellular AAT-eGFP (initiated from an alternative AUG-2 start codon), with the proportion regulated by the SERPINA1 5'-UTR. Both fusion proteins localize to distinct cellular compartments: in contrast to a fusion with the secretory AAT accumulating in the ER, the intracellular one exhibits nuclear-cytoplasmic shuttling. We detected putative endogenous AAT isoform enriching the nuclear speckles. CONCLUSION: Alternative translation initiation might be a mechanism through which SERPINA1 expands the biological diversity of its protein products. Our findings open up new prospects for the study of SERPINA1 gene expression.

Can the Acute-Phase Reactant Proteins be Used as Cancer Biomarkers?

The association between the acute-phase reactant proteins (APRPs) and cancer has long been established. There have been numerous reports correlating altered levels of various APRPs with different types of cancers. However, researchers are often quick to dismiss the use of these APRPs as potential biomarkers for the diagnosis and monitoring of cancer because alterations in APRP concentrations are observed in a wide range of diseases. Recent progress in proteomics studies which profiled the serum proteins of cancer patients and those of normal individuals indicated that the altered APRP expressions were different for distinct types, subtypes, and even stages of cancer. Interestingly, these data are in agreement with those observed earlier using immunochemical and biochemical assays. In view of this compelling association of different patterns of APRPs with various types of cancers and in an apparent shift of paradigm, we present in this review some indications that APRP fingerprinting may be used as complementary cancer biomarkers.

GSEH: A Novel Approach to Select Prostate Cancer-Associated Genes Using Gene Expression Heterogeneity

When a gene shows varying levels of expression among normal people but similar levels in disease patients or shows similar levels of expression among normal people but different levels in disease patients, we can assume that the gene is associated with the disease. By utilizing this gene expression heterogeneity, we can obtain additional information that abets discovery of disease-associated genes. In this study, we used collaborative filtering to calculate the degree of gene expression heterogeneity between classes and then scored the genes on the basis of the degree of gene expression heterogeneity to find "differentially predicted" genes. Through the proposed method, we discovered more prostate cancer-associated genes than 10 comparable methods. The genes prioritized by the proposed method are potentially significant to biological processes of a disease and can provide insight into them.

Proteome Profiling of Urinary Exosomes Identifies Alpha 1-Antitrypsin and H2B1K as Diagnostic and Prognostic Biomarkers for Urothelial Carcinoma

MALDI-TOF spectrometry has not been used for urinary exosome analysis. We used it for determining UC biomarkers. From 2012 to 2015, we enrolled 129 consecutive patients with UC and 62 participants without UC. Exosomes from their urine were isolated, and analyzed through MALDI-TOF spectrometry. Immunohistochemical (IHC) analysis of another 122 UC and 26 non-UC tissues was conducted to verify the discovered biomarkers. Two peaks at m/z 5593 (fragmented peptide of alpha-1-antitrypsin; sensitivity, 50.4%; specificity, 96.9%) and m/z 5947 (fragmented peptide of histone H2B1K sensitivity, 62.0%; specificity, 92.3%) were identified as UC diagnosis exosome biomarkers. UC patients with detectable histone H2B1K showed 2.29- and 3.11-fold increased risks of recurrence and progression, respectively, compared with those with nondetectable histone H2B1K. Verification results of IHC staining revealed significantly higher expression of alpha 1-antitrypsin (p = 0.038) and H2B1K (p = 0.005) in UC tissues than in normal tissues. The expression of alpha 1-antitrypsin and H2B1K in UC tissues was significantly correlated with UC grades (p < 0.05). Urinary exosome proteins alpha 1-antitrypsin and histone H2B1K, which are identified through MALDI-TOF analysis, could facilitate rapid diagnosis and prognosis of UC.

Selenium-responsive proteins in the sera of selenium-enriched yeast-supplemented healthy African American and Caucasian men

BACKGROUND

Studies have shown that supplementation of adult men with selenium-enriched yeast (SY) was protective against prostate cancer (PCa) and also reduced oxidative stress and levels of prostate-specific antigen. Here, we determined the effect of SY supplementation on global serum protein expression in healthy men to provide new insights into the mechanism of selenium chemoprevention; such proteins may also serve as biomarkers of disease progression.

METHODS

Serum samples from 36 adult men were obtained from our previous SY clinical trial, 9 months after supplementation with either SY (247 microg/d; n = 17) or placebo (nonenriched yeast; n = 19).

RESULTS

Proteomic profiling using two-dimensional difference in gel electrophoresis followed by liquid chromatography-tandem mass spectrometry revealed a total of 1,496 candidate proteins, of which, 11 were differentially expressed in the SY group as compared with placebo. Eight proteins were upregulated [clusterin isoform 1 (CLU), transthyretin, alpha-1B-glycoprotein, transferrin, complement component 4B proprotein, isocitrate dehydrogenase, haptoglobin, and keratin 1] and three proteins were downregulated [alpha-1 antitrypsin (AAT), angiotensin precursor, and albumin precursor] by SY. All of the identified proteins were redox-sensitive or involved in the regulation of redox status. Because both AAT and CLU have been previously linked to PCa development, their identities were confirmed by two-dimensional Western blot analysis.

CONCLUSIONS

We identified AAT and CLU as potential candidate proteins involved in the mechanism of PCa prevention by SY. Collectively, proteins identified in this study might serve as potential new biomarkers for monitoring and comparing responses to selenium-based chemopreventive agents.

IMPACT

Proteomic analysis of serum might be useful for the early detection and monitoring efficacy of chemopreventive agents.

Prognostic potential of a PSA complex in sera of prostate cancer patients with alpha2-macroglobulin deficiency

We previously reported on a number of cases of metastatic prostate cancer (PCa) in which serum alpha2-macroglobulin (alpha2M) levels were markedly decreased to less than 20 mg/dl (alpha2M deficiency). In order to elucidate the relative proportions of free and a prostate-specific antigen (PSA) complex in PCa patients with alpha2M deficiency, we have assessed serum alpha2M and total PSA levels, and ratios of free PSA to total PSA (F/T ratios) at each stage of PCa. Moreover, the PSA reactivity profile was determined on fractionated serum specimens of PCa patients using high-performance liquid chromatography (HPLC) using a TSKG-3000 SWXL column. Measurement of alpha2M concentration was performed by laser-nephelometry. PSA levels were determined by enzyme immunoassay, free PSA by radioimmunoassay. In those PCa patients with alpha2M deficiency, serum alpha2M and F/T ratios were lower, whereas PSA levels were higher when compared with those PCa patients without alpha2M deficiency (P<0.05). PSA elution profiles on HPLC columns revealed two major peaks. The proportion of PSA-antichymotrypsin (PSA-ACT) increased, whereas the proportion of free PSA decreased in PCa patients with alpha2M deficiency as compared with those PCa patients without alpha2M deficiency. F/T ratios were significantly lower in PCa patients with alpha2M deficiency than in those PCa patients without alpha2M deficiency. PSA-ACT and F/T ratio may be useful for monitoring bone metastasis in PCa.

A systematic review of the association between circulating concentrations of C reactive protein and cancer

The objective of this study was to review and summarise the published evidence for an association between circulating concentrations of C reactive protein (CRP) and cancer through a systematic review. 90 discrete studies were identified. 81 (90%) were prevalent case-control or cross-sectional studies, and only 9 studies had a prospective design. In most prevalent studies, CRP concentrations were found to be higher in patients with cancer than in healthy controls or controls with benign conditions. Of the nine large prospective studies identified in this review, four reported no relationship between circulating CRP levels and breast, prostate or colorectal cancers, and five studies found that CRP was associated with colorectal or lung cancers. Most of the studies evaluating CRP as a diagnostic marker of cancer did not present relevant statistical analyses. Furthermore, any association reported in the prevalent studies might reflect reverse causation, survival bias or confounding. The prospective studies provided no strong evidence for a causal role of CRP in cancer. Instead of further prevalent studies, more large prospective studies and CRP gene-cancer association studies would be valuable in investigating the role of CRP in cancer.

Identification of differentially secreted biomarkers using LC-MS/MS in isogenic cell lines representing a progression of breast cancer

Proteins secreted (the secretome) from cancer cells are potentially useful as biomarkers of the disease. Using LC-MS/MS, the secreted proteomes from a series of isogenic breast cancer cell lines varying in aggressiveness were analyzed by mass spectrometry: nontumorigenic MCF10A, premalignant/tumorigenic MCF10AT, tumorigenic/locally invasive MCF10 DCIS.com, and tumorigenic/metastatic MCF 10CA cl. D. Proteomes were obtained from conditioned serum-free media, partially fractionated using a small reverse phase C2 column, and digested with trypsin for analysis by LC-MS/MS, using a method previously shown to give highly enriched secreted proteomes (Mbeunkui et al. J. Proteome Res. 2006, 5, 899-906). The search files produced from five analyses (three separate preparations) were combined for database searching (Mascot) which produced a list of over 250 proteins from each cell line. The aim was to discover highly secreted proteins which changed significantly in abundance corresponding with aggressiveness. The most apparent changes were observed for alpha-1-antichymotrypsin and galectin-3-binding protein which were highly secreted proteins from MCF10 DCIS.com and MCF10CA cl. D, yet undetected in the MCF10A and MCF10AT cell lines. Other proteins showing increasing abundance in the more aggressive cell lines included alpha-1-antitrypsin, cathepsin D, and lysyl oxidase. The S100 proteins, often associated with metastasis, showed variable changes in abundance. While the cytosolic proteins were low (e.g., actin and tubulin), there was significant secretion of proteins often associated with the cytoplasm. These proteins were all predicted as products of nonclassical secretion (SecretomeP, Center for Biological Sequence Analysis). The LC-MS/MS results were verified for five selected proteins by western blot analysis, and the relevance of other significant proteins is discussed. Comparisons with two other aggressive breast cancer cell lines are included. The protein with consistent association with aggressiveness in all lines, and in unrelated cancer cells, was the galectin-3-binding protein which has been associated with breast, prostate, and colon cancer earlier, supporting the approach and findings. This analysis of an isogenic series of cell lines suggests the potential usefulness of the secretome for identifying prospective markers for the early detection and aggressiveness/progression of cancer.