Increasing human serum ribonuclease activity is a concomitant phenomenon of ovarian carcinoma

A hybrid chimeric system for versatile and ultra-sensitive RNase detection

We developed a new versatile strategy that allows the detection of several classes of RNases (i.e., targeting ss- or ds-RNA, DNA/RNA hetero-hybrid or junctions) with higher sensitivity than existing assays. Our two-step approach consists of a DNA-RNA-DNA chimeric Hairpin Probe (cHP) conjugated to magnetic microparticles and containing a DNAzyme sequence in its terminal region, and molecular beacons for fluorescence signal generation. In the first step, the digestion of the RNA portion of the cHP sequences in presence of RNases leads to the release of multiple copies of the DNAzyme in solution. Then, after magnetic washing, each DNAzyme molecule elicits the catalytic cleavage of numerous molecular beacons, providing a strong amplification of the overall sensitivity of the assay. We successfully applied our approach to detect very low concentrations of RNase A, E. coli RNase I, and RNase H. Furthermore, we analyzed the effect of two antibiotics (penicillin and streptomycin) on RNase H activity, demonstrating the applicability of our strategy for the screening of inhibitors. Finally, we exploited our system to detect RNase activity directly in crude biological samples (i.e., blood and saliva) and in cell culture medium, highlighting its suitability as cheap and sensitive tool for the detection of RNase levels.

Secretion of ribonucleases by normal and immortalized cells grown in serum-free culture conditions

The requirement of serum in cell culture is a major limitation for studies on secreted ribonucleases (RNases) because serum contains a high amount of ribonucleolytic activity. Defined culture condition is thus of interest to improve our knowledge of the RNase biology. We report here that cells from three different types and origins, Chinese hamster lung fibroblasts, bovine smooth muscle cells, and human endothelium-derived EA.hy926 cells, proliferate consistently in the presence of a basal medium supplemented with bovine serum albumin, high-density lipoproteins, basic fibroblast growth factor, insulin, and transferrin. Using a new quantitative radio-RNase inhibitor assay, two distinct ribonucleolytic assays, and a radioimmunoassay against angiogenin, it is shown that RNases became apparent in media conditioned by cell monolayers. Both the hamster lung fibroblast and the EA.hy926 cell lines secreted larger amounts of RNase inhibitor-interacting factors and RNase activity than normal smooth muscle cells. The serum-free medium represents an alternative way to grow these cells and allows investigation of biosynthesis and functions of RNases in culture. It should be useful to identify and quantitate unambiguously specific members of the RNase family secreted by normal versus tumor cells in culture.

Serum ribonuclease activity in the diagnosis of pancreatic disease

The present study evaluated serum ribonuclease activity (SRA) in patients with inflammatory and neoplastic pancreatic diseases. RNase determination was carried out using t-RNA (T) from E. coli MRE 600 at pH 7.4 and polycytidylic acid (poly-C) (P) at pH 6.6 as RNA substrates with RNase A from bovine pancreas as reference enzyme. Healthy volunteers had a SRA of T: 160 +/- 12 and P: 482 +/- 24 ngeq/mL (mean +/- SEM (n]. In patients with acute interstitial pancreatitis (AIP), SRA was similar to healthy controls (T: 166 +/- 14; P: 474 +/- 30 ngeq/mL). Patients with acute necrotizing pancreatitis (ANP) had increased SRA (T: 278 +/- 49; P: 791 +/- 145 ngeq/mL, p less than 0.01, compared to controls). SRA values were also increased in patients with chronic pancreatitis (CP) with T: 224 +/- 15 ngeq/mL (p less than 0.01) and in patients with pancreatic carcinoma (PCA) with T: 331 +/- 35 (p less than 0.001 vs controls, p less than 0.01 vs CP). Increased SRA was detected in patients with renal insufficiency (T: 2576 +/- 195 ngeq/mL, p less than 0.001). Diagnostic discrimination between AIP and ANP was achieved in 69% using T-SRA (sensitivity 31%, specificity 88%), and in 78% using P-SRA (sensitivity 54%, specificity 92%). Discrimination between CP and pancreatic carcinoma was possible in 68% (sensitivity 67%, specificity 71%). The diagnostic value of serum RNase is limited because of its low sensitivity, but increased T-SRA above a cutoff of 250 ngeq/mL and increased P-SRA above a cutoff of 620 ngeq/mL are specific for detecting pancreatic necrosis in the absence of renal impairment. The kidney is a major site for SRA clearance.

Ovarian carcinoma: increase in clinical validity by simultaneous determination of SRA and CA 125

Ovarian carcinomas are distinguished by their polyclonality, i.e., heterogeneity and polymorphism of their tissue. There is no marker available complying with the clinical demands in the case of ovarian carcinoma regarding satisfactory sensitivity and specificity. Therefore, we have simultaneously determined two entirely distinct tumor markers, serum ribonuclease activity (SRA) and cancer antigen 125 (CA 125), recommended in the literature with respect to ovarian carcinoma. After evaluation by logistic regression analysis, we found a specificity of 93% together with a sensitivity of 97% for the simultaneous determination of SRA and CA 125 (37 ovarian carcinomas, 11 cases without pathological findings after treatment, 11 benign tumors of the ovary, 61 controls). The patients are not exposed to increased stress by this simultaneous determination method compared to the determination of a single marker. The increased clinical validity justifies the recommendation of routine simultaneous determinations of SRA and CA 125 for diagnosis and monitoring of patients with ovarian carcinoma.

Poly (C) avid ribonuclease estimation in patients with solid tumors. A critical evaluation

Activity of Poly (C) avid ribonuclease was estimated in sera of 129 patients with different malignancies. All patients had histologically verified carcinomas, normal renal function, and no signs of acute catabolic condition. Activity values were compared with those of normal subjects (U-test, Mann and Whitney) separately for each age decade and type of carcinoma. Patients with ovarian and bronchus carcinoma had statistically elevated activity values throughout all age groups. Colon carcinoma patients showed elevated values in most instances. In patients with pancreatic carcinoma a difference could be detected in only one age group (51-60 years of age). No significant elevation of enzyme activity was detected in carcinoma of the stomach and of the prostate. It is concluded that there are carcinomas leading to elevated ribonuclease activity, although the biological basis of this phenomenon is not understood. No special sensitivity nor specificity of ribonuclease elevation could be demonstrated in pancreatic carcinoma patients. Up to now the usefulness of ribonuclease estimation in prospective carcinoma detection remains questionable.