Clinical implications of free-to-total immunoreactive prostate-specific antigen ratios.

OBJECTIVE: A study was performed to evaluate the free-to-total prostate-specific antigen (PSA) ratio for discriminating benign prostatic hyperplasia (BPH) or prostate cancer in the intermediate PSA range (2.0-10.0 microg/l) in patients referred for prostate evaluation. In addition, the relationship of free-to-total PSA ratio and tumor grade in prostatic cancer cases, implying a higher concentration of complex PSA in poorly differentiated cancer, was assessed for its predictive value of tumor aggressiveness at the time of diagnosis. PATIENTS AND METHODS: Seven hundred and sixteen patients referred to the out-patient clinics of two urological departments were included in this prospective study. Blood samples were taken for total immunoreactive and free PSA (IMMULITE) determinations prior to any manipulation. The patients were grouped according to their PSA levels: 2.0-4.0 microg/l, 4.0-10.0 microg/l, 10.0-20.0 microg/l and > or = 20.0 microg/l. All patients were categorized, after histological confirmation, as having BPH (n = 423) or prostate cancer (n = 293). In patients with cancer the tumor grade was also assessed. RESULTS: In patients with serum immunoreactive PSA levels in the 2.0-4.0 microg/l range, a free-to-total PSA ratio lower than 22% predicted the presence of prostate cancer with a sensitivity of 67% and a specificity of 63%. The positive- and negative-predictive values were 29% and 90% respectively. Receiver-operating characteristic curve analysis indicated a free-to-total PSA ratio of 22% to be the optimum discriminatory level in this low PSA range. For patients with a serum PSA level between 4.0 and 10.0 microg/l, the threshold ratio of 18% gave a sensitivity of 70%, a specificity of 70%, a positive-predictive value of 46% and a negative-predictive value of 87%. Men with a well differentiated grade of prostate cancer had higher free-to-total PSA ratios than those with less differentiated tumors (p = 0.01). CONCLUSIONS: Our data indicate that the free-to-total PSA ratio, in patients with prostatic disease and with PSA levels in the 2.0-10.0 microg/l range, gives a significant improvement in prediction of cancer over the total immunoreactive PSA value alone. Because of the correlation between a higher tumor grade and a lower free-to-total PSA ratio, this ratio may be helpful in assessing the risk of a poorly differentiated cancer.

Ultrasound-guided seminal vesicle biopsies in prostate cancer.

Invasion of prostatic adenocarcinoma into the seminal vesicles (SV) is generally accepted as an index of poor prognosis. The pre-operative identification of SV invasion is an important element in staging since it may alter subsequent treatment decisions. We studied the possibility of diagnosing SV invasion with two biopsies from the junction between the prostate and seminal vesicles. Also we studied the correlation of several prognostic factors with the risk of clinical stage T(1,2,3) prostate cancer patients of having cancer growth into the seminal vesicles. Consecutive patients referred for transrectal ultrasound (TRUS) and biopsy because of clinical suspicion of prostate cancer were examined. This staging procedure was evaluated in patients who underwent a pelvic lymphadenectomy and radical retropubic prostatectomy (RRP). In 83 out of 138 patients prostate cancer was detected whereas 55 patients had benign disease. In 44% of prostate cancer patients a positive SV biopsy was found. The accuracy of the biopsies adjacent to the junction of the SV and the prostate was 91%. The best predictors for SV invasion were tumor grade of the biopsy sample (P<0.001), serum prostate-specific antigen (PSA) (P<0.0005), PSA density (P<0.0005) and clinical stage (P<0.0005). No significance was found in the relation to seminal vesicle involvement with free/total (f/t) PSA ratio (P=0.588) for the prostate cancer group (SV+ and SV-). In a receiver operating characteristic curves analysis, PSA density was significantly more accurate for prediction of SV invasion than PSA or f/t PSA ratio. In five prostatectomized patients (and negative SV biopsy) no SV invasion was found in the final pathologic examination either. SV biopsy at the junction of the SV and prostate is accurate for staging with high efficacy and low morbidity. To predict SV invasion in prostate cancer patients, PSA density was more accurate than PSA or f/t PSA ratio. The determination of the f/t PSA ratio in patients with low and intermediate PSA levels (eg <15 &mgr;g/L) is not useful to estimation of the risk of seminal vesicle involvement. The combination of serum PSA concentration, PSA density, tumor grade from the biopsy specimens ad clinical stage provides the best prediction of SV invasion. These parameters are identical to the conventional predictors of pathology after RRP. SV biopsies may provide additional information; if one or both basal biopsies are positive, a clinical T(1,2) disease is altered to T(3). Hence SV biopsy is useful for selection of patients who might obtain good results from RRP for prostate cancer. Prostate Cancer and Prostatic Diseases (2000) 3, 100-106

Bioavailability of orally administered zinc, using Taurizine.

Zinc aspartate equivalent to 50 mg of elementary zinc, orally administered to seven normal healthy male volunteers in an enteric-coated tablet (Taurizine), gave no significantly increased plasma zinc levels, neither when this drug was taken in a fasting state nor during a lunch. The formulation of this tablet seems to obstruct the absorption of zinc.

Specific alterations of the EF-Tu polypeptide chain considered in the light of its three-dimensional structure.

Specific alterations of the elongation factor Tu (EF-Tu) polypeptide chain have been identified in a number of mutant species of this elongation factor. In two species, Ala-375, located on domain II, was found by amino acid analysis to be replaced by Thr and Val, respectively. These replacements substantially lower the affinity of EF-Tu.GDP for the antibiotic kirromycin. Since kirromycin can be cross-linked to Lys-357, also located on domain II but structurally very far from Ala-375, these data suggest that the replacements alter the relative position of domains I and II. The Ala-375 replacements also lower the dissociation rates of the binary complexes EF-Tu.GTP and the binding constants for EF-Tu.GTP and Phe-tRNA. It is conceivable that these effects are also mediated by movements of domains I and II relative to each other. Replacement of Gly-222 by Asp has been found in another mutant by DNA sequence analysis of the cloned tufB gene, coding for this mutant EF-Tu. Gly-222 is part of a structural domain, characteristic for a variety of nucleotide binding enzymes. Its replacement by Asp does not abolish the ability of EF-Tu to sustain protein synthesis. It increases the dissociation rate of EF-Tu.GTP by approximately 30%. In the presence of kirromycin this mutant species of EF-Tu.GDP does not bind to the ribosome, in contrast to its wild-type counterpart. A possible explanation is now open for experimental verification.

The elongation factor Tu.kirromycin complex has two binding sites for tRNA molecules.

The interaction of the polypeptide chain elongation factor Tu (EF-Tu) with the antibiotic kirromycin and tRNA has been studied by measuring the extent of protein modification with N-tosyl-L-phenylalanine chloromethylketone (TPCK) and N-ethylmaleimide (NEM). Kirromycin protects both EF-Tu.GDP and EF-Tu.GTP against modification with TPCK. Binding of aminoacyl-tRNA added at increasing concentrations to a solution of 40 microM EF-Tu.GDP.kirromycin complex re-exposes the TPCK target site on the protein. However, when the aminoacyl-tRNA concentration is raised beyond 20 microM, TPCK labeling drops again and is blocked completely at approximately 300 microM aminoacyl-tRNA. By contrast, addition of uncharged tRNA or N- acetylaminoacyl -tRNA enhances TPCK labeling of the protein over the entire tRNA concentration range studied. These data strongly suggest that kirromycin induces in EF-Tu.GDP an additional tRNA binding site that can bind uncharged tRNA, aminoacyl-tRNA, and N- acetylaminoacyl -tRNA. Support for this assumption is provided by measuring the modification of EF-Tu.GDP with the sulfhydryl reagent NEM. Moreover, NEM modification also indicates an additional tRNA binding site on EF-Tu.GTP.kirromycin, which could not be detected with TPCK. Mapping of the tryptic peptides of EF-Tu.GDP labeled with [14C]TPCK revealed only one target site for this agent, i.e., cysteine-81. Modification occurred at the same site in the presence and in the absence of kirromycin and uncharged tRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular properties of two mutant species of the elongation factor Tu.

The molecular properties of two mutant species of the elongation factor Tu (EF-Tu), derived from either tuf A or tuf B, have been studied. One, designated EF-TuAR, is the product of a kirromycin-resistant tufA gene. The other designated EF-TuBO is a tuf B product and is present in a kirromycin-resistant mutant of Escherichia coli (LBE 2012) also harbouring the EF-TuAR species. EF-TuAR has been isolated in homogeneous form as a single gene product from the mutant strain LBE 2045, in which the tuf B gene has been inactivated by an insertion of the bacteriophage Mu. EF-TuBO has been isolated from LBE 2012 together with EF-TuAR in a 1:1 mixture. Fractionation of this mixture of DEAE-Sephadex A-50 resulted in an enrichment of EF-TuBO of about 80%. The properties of EF-TuAR and EF-TuBO have been compared to those of a kirromycin-sensitive species designated EF-TuAS, which was isolated from LBE 2045 by transduction of wild-type tuf A. We show here that all three EF-Tu species are fully competent to sustain polypeptide synthesis. All also appear to interact normally with guanine nucleotides and EF-Ts. Only in the presence of the antibiotic do the following differences appear. (a) Kirromycin causes EF-TuAS (wild-type tuf A gene product) to be retained on, and thus block, the ribosome. (b) EF-TuAR fails to bind the antibiotic and thus is capable of protein synthesis in its presence. (c) EF-TuBO fails to sustain polypeptide synthesis upon binding of kirromycin. It does not, however, block the ribosome, so the strain harbouring both this protein and EF-TuAR (LBE 2012) is kirromycin resistant.

A mutant elongation factor Tu which does not immobilize the ribosome upon binding of kirromycin.

In the accompanying paper we have shown that polypeptide synthesis sustained by the mutant elongation factor EF-TuBO is inhibited by kirromycin. Here we have searched for the primary site of inhibition in the elongation cycle. It is demonstrated that in the presence of the antibiotic EF-TuBO can form a complex with aminoacyl-tRNA and GTP and that the complex is able to bind to ribosomes programmed with poly(U). Like its wild-type counterpart, EF-TuBO . GDP can form a quaternary complex with aminoacyl-tRNA and kirromycin but, unlike the wild-type quaternary complex, the mutant complex fails to associate with the ribosome. This explains the recessive nature of the tuf B mutation in cells producing kirromycin-resistant EF-TuA and EF-TuBO. It also suggests a mechanism for the inhibition by kirromycin of EF-TuBO-dependent polypeptide synthesis.

Genes VI, VII and IX of bacteriophage M13: identification of their products as minor capsid proteins.

In earlier work, two new minor capsid proteins of molecular weight 3500 (C-protein) and 11,500 (D-protein) were detected in M13 virions. To determine their genetic origin, differential amino acid labeling, amino acid analysis and Edman degradation analysis were performed on these proteins. The data demonstrate that D-protein is the product of gene VI whereas C-protein is composed of both the proteins specified by gene VII and the recently discovered gene IX. by selective labeling with arginine, the number of C and D protein molecules present in M13 virions was estimated to be 5 D-protein and approx. 6-8 C-protein molecules. From synthesis studies of C-protein in E. coli minicells which harbor either wt- or amber mutant RF molecules, evidence is presented that genes V, VII and IX form an operon.