Early prostate-specific antigen relapse after radical retropubic prostatectomy: prediction on the basis of preoperative and postoperative tumor characteristics

OBJECTIVES

This study was undertaken to distinguish between patients who will and will not benefit from a retropubic radical prostatectomy (RRP) for clinically localized prostatic carcinoma (PCa) on the basis of preoperative and postoperative tumor characteristics.

METHODS

Data of 318 consecutive patients who underwent RRP for clinically localized PCa were reviewed. Preoperative characteristics used included clinical stage, findings on transrectal ultrasonography, prostate-specific antigen (PSA) values, Gleason grade, number of positive biopsies, number of biopsies containing any Gleason grade 4 and/or 5 cancer, and number of biopsies with predominant (>50% of cancerous tissue) Gleason grade 4 and/or 5 cancer. Postoperative characteristics included pathologic stage, Gleason grade, margin status, cancer volume, and volume of Gleason grade 4 and/or 5 cancer. The impact on biochemical relapse after RRP were calculated by Cox regression and CART (classification and regression tree) analysis to establish low, intermediate, and high risk of recurrence.

RESULTS

Of patients who underwent RRP, 66% showed no evidence of relapse after a follow-up of 42 months. All preoperative and postoperative characteristics showed a significant association with biochemical relapse. Cox regression of preoperative characteristics showed the number of positive biopsies with predominant Gleason grade 4 and/or 5 cancer to be the most accurate predictor of failure (p < 0.0001), followed by the number of positive biopsies and PSA. CART analysis distinguished between four risk groups on the basis of the same characteristics as in the Cox regression. The low-risk group consisted of 232 patients (75.1%) and the high-risk group of 17 patients (5.5%); corresponding Kaplan-Meier curves showed a 2-year PSA-free survival rate of 97% for the low-risk group and 20% for the high-risk group. Cox regression of postoperative characteristics recognized the volume of Gleason grade 4 and/or 5 as the characteristic with the strongest association with biochemical failure. CART analysis distinguished between four risk groups, using the volume of high-grade cancer as the most influential characteristic. The corresponding Kaplan-Meier curves showed for the low-risk group (n = 79; 29.6%) a PSA-free survival rate of 96% after 42 months and for the high-risk group (n = 47; 17.6%) a 21% PSA-free survival rate after 42 months.

CONCLUSION

For preoperative and postoperative estimation of biochemical recurrence after RRP, a quantitative analysis of high-grade cancer, expressed by the number of preoperative biopsy cores containing high-grade cancer and the volume of cancer, proved to be the best predictor of relapse. CART analysis might be useful in advising patients for their best therapy options. However, defined characteristics of risk groups should be evaluated with new prospective data before they are used routinely.

Ultrasensitive detection of prostate specific antigen in the followup of 422 patients after radical prostatectomy

PURPOSE

We validated our ultrasensitive prostate specific antigen (PSA) assay based on lyophilization and 4-fold concentration of patient sera with the clinical long-term followup and according to histopathological characteristics of 422 patients treated with radical retropubic prostatectomy for prostate cancer.

MATERIALS AND METHODS

Each serum sample was divided into 2 aliquots for standard and 4-fold concentrated (ultrasensitive) detection. Samples were analyzed by the same unmodified DPC-Immulite PSA assay. Biochemical relapse was defined as an increase of at least 0.10 ng./ml. in native serum (equivalent to 0.025 ng./ml. in concentrated serum). Mean followup was 449 days (range 29 to 2,057). Kaplan-Meier analysis of standard and ultrasensitive detection results was done, and findings were correlated with pathological stage, Gleason grade, total cancer volume, Gleason grade 4 cancer volume and margin status. Significance of earlier detection in ultrasensitive versus standard detection was calculated with the log rank (Mantel-Cox) test with p <0.05 considered significant.

RESULTS

Of 442 patients 88 (20.8%) experienced biochemical recurrence. Of this cohort 28 (31%) demonstrated early failure on the ultrasensitive assay which was later confirmed on the standard assay, 37 (42%) had failure simultaneously on both assays and 23 (26%) had failure on the ultrasensitive but remained disease-free on the standard assay. Average time for ultrasensitive assay detection of recurrence was 288 days (standard 555). Kaplan-Meier analysis revealed significant advantages in earlier detection of recurrence with the ultrasensitive assay, and close correlation with pathological stage, Gleason grade, margin status and Gleason grade 4 cancer volume. Time advantages of ultrasensitive versus standard detection were greater for advanced cancers (pT3a/b or greater, Gleason 3 + 4 or greater) than for small, low grade tumors. All patients who had positive results on the standard assay had a previous (28) or simultaneous (37) positive ultrasensitive result. With standard detection 25% of all relapses were evident within the first year of surgery and with ultrasensitive detection the percentage increased to 85.7%. On both assays 334 patients remained free of biochemical recurrence.

CONCLUSIONS

Our ultrasensitive PSA assay is useful for early detection of biochemical relapse after radical retropubic prostatectomy. It not only provides the same accuracy as conventional PSA assays but also offers the advantage of detecting recurrence about 300 days earlier. Thus, long-term results of radical retropubic prostatectomy series can be calculated sooner. The clinical impact of this assay will be obvious once curative treatment options are available if applied at the earliest time of evident tumor recurrence.

Incidence of positive surgical margins after biopsy-selected nerve-sparing radical prostatectomy

OBJECTIVES

The selection criteria for a nerve-sparing radical prostatectomy (NSRP) are not thoroughly investigated and are based mainly on preoperative digital rectal examinations and intraoperative findings. At our institution NSRP is performed only on patients whose preoperative systematic sextant biopsy of the prostate showed only unilateral cancer. To prove the safety of these criteria, we analyzed the incidence of positive surgical margins and tumor progression rate in patients who were selected for an NSRP only by the result of the biopsy.

METHODS

Preoperative systematic sextant biopsies revealed unilateral cancer in 69 preoperatively potent men of 289 consecutive prostatic cancer patients (23.9%); contralateral NSRP was performed on these 69 patients. The prostate specimens were investigated by using a 3-mm step-section technique to identify positive surgical margins. Tumor progression was defined as a prostate-specific antigen (PSA) level greater than 0.4 ng/mL in the native and greater than 0.025 ng/mL in the suprasensitive postoperative blood test. Mean follow-up was 15 months (range 6 to 24).

RESULTS

In 69 patients who underwent NSRP, 11 positive margins (15.9%) were found. Only 3 patients (4.3%) had a positive margin on the nerve-sparing side. In 220 patients who underwent non-NSRP 59 positive margins (26.8%) were detected. PSA recurrence rate after 12 months was similar in patients with NSRP and non-NSRP. Analysis of systematic sextant biopsies gives safe selection criteria because in approximately 95% the surgical margin on the nerve-sparing side will be negative.

CONCLUSIONS

Basing the indication for an NSRP on the results of preoperative systematic biopsies was safe according to margin status and postoperative PSA, when all patients with tumor in one of the three biopsy cores of each side of the prostate were excluded from an NS technique on that side. Such a strict approach will exclude approximately 30% of patients from NSRP unnecessarily because of tumor findings on a prostate side where the cancer is still organ-confined. Less strict criteria, including patients with only well-differentiated cancer and a maximum of one positive biopsy on the evaluated side, seem to be as safe as the described selection. However, data on these patients need further evaluation.

Prostatic volume and ratio of free-to-total prostate specific antigen in patients with prostatic cancer or benign prostatic hyperplasia

PURPOSE

We correlated prostatic volume with the ratio of free-to-total prostate specific antigen (PSA) in serum from patients with prostatic cancer or benign prostatic hyperplasia (BPH) to evaluate how prostatic volume influences the ratio.

MATERIALS AND METHODS

We evaluated sera from 395 patients (mean age 65 years, range 45 to 88) with prostate cancer (239) or BPH (156) for total PSA, free PSA and ratio of free-to-total PSA. For detection of total and free PSA we used an Immulite free and total PSA assay. Prostatic volume was determined with transrectal ultrasonography. Prostatic volume in BPH and prostate cancer patients was divided into 10 ml. groups, and mean ratio of free-to-total PSA was calculated for each volume group and both diseases. For statistical analysis Mann-Whitney U and Kruskal-Wallis tests were performed in addition to calculation of sensitivity and specificity, and receiver operator curves for prostates 60 ml. or less and greater than 60 ml.

RESULTS

For BPH patients the mean ratio of free-to-total PSA was 14.64 to 25.14% without a close relation to prostatic volume. In prostate cancer patients a proportional increase from 8.45 to 19.37% in the ratio of free-to-total PSA with volume was found. Mann-Whitney U analysis revealed significant differences in prostate cancer versus BPH only in patients with prostates of 60 ml. or smaller (p = 0.0008 to 0.029). No significant differences were seen when prostate cancer and BPH patients with prostates larger than 60 ml. were compared (p = 0.082 to 0.868). Kruskal-Wallis test confirmed independence of the ratio of free-to-total PSA from prostatic volume in BPH patients (p = 0.285) but dependence in prostate cancer patients (p <0.0001). Sensitivity was higher in patients with prostates 60 ml. or smaller (86.72%) than in patients with prostates larger than 60 ml. (66%), and specificity was lower at 45.78 and 56.16%, respectively.

CONCLUSIONS

We have shown that the ratio of free-to-total PSA is influenced by prostatic volume in patients with prostate cancer. The ratio of free-to-total PSA provides useful information for differentiate BPH from prostate cancer in patients with small prostates but it is less useful in patients with larger prostates, probably because of the larger proportion of benign hypertrophic tissue.

Use of serum concentration techniques to enhance early detection of recurrent prostate cancer after radical prostatectomy

OBJECTIVES

We evaluated the clinical applicability of serum concentration techniques to enhance the detection of prostate-specific antigen (PSA) in men with recurrent prostate cancer after radical prostatectomy.

METHODS

We concentrated blood serum by lyophilization and ultrafiltration from female patients who had undergone cystoprostatectomy, "cured" patients who had undergone radical prostatectomy, patients without prostate cancer, and patients with prostate cancer treated with radiation or hormonal therapy. The primary study group consisted of 31 patients with recurrent disease after radical prostatectomy whose initial postoperative PSA fell to undetectable levels (less than 0.07 ng/mL) that later turned positive (0.07 ng/mL or more) by the Tosoh AIA 600 immunoassay run in the ultrasensitive mode. All serum samples of less than 0.07 ng/mL were concentrated by lyophilization or ultrafiltration.

RESULTS

Serum concentrated by lyophilization and filtration detected PSA recurrence significantly earlier than did unconcentrated serum in 29 of 31 patients (94%) and in 28 of 31 patients (90%), respectively. The mean advantage for the 29 patients was 362 days; for the 28 patients it was 383 days. The mean native PSA was 0.04 ng/mL (range 0.00 to 0.06) at the time of earliest detection by concentration techniques. Serum from female patients who had undergone cystoprostatectomy and "cured" patients who had undergone radical prostatectomy failed to concentrate, giving a test specificity of 100%.

CONCLUSIONS

Serum concentration is a specific and sensitive technique that provides a significant lead time of an additional 12 months in detecting cancer recurrence after radical prostatectomy when compared with nonconcentrated serum. Because the Tosoh assay, when run in the ultrasensitive mode, gave an additional lead time of 9 months at a residual cancer detection limit of 0.07 ng/mL, the combination of the Tosoh assay and serum concentration allows detection of a failed radical prostatectomy about 2 years earlier than does the Hybritech Tandem-R assay, which has a residual cancer detection limit of 0.2 ng/mL.

Effect of disruption of the enniatin synthetase gene on the virulence of Fusarium avenaceum

Production of the phytotoxic compound enniatin has been proposed to play a role during the infection process of plants by enniatin-synthesizing Fusarium species. Enniatins are cyclohexadepsipeptides synthesized by the multifunctional enzyme enniatin synthetase. To test the hypothesis that enniatin contributes to pathogenicity, enniatin-nonproducing mutants were constructed by gene disruption of the enniatin synthetase gene of a virulent Fusarium avenaceum strain. Four independent enniatin nonproducing mutants were characterized that did not express enniatin synthetase, as proved by RNA and protein blot analysis. The virulence on potato tuber tissue of the enniatin-nonproducing strains was significantly reduced compared with the virulence of the parent strain and three enniatin-producing transformants. Therefore, we conclude that enniatin production contributes to the virulence of Fusarium avenaceum.

Enniatin production by fusarium strains and its effect on potato tuber tissue

Several Fusarium strains produce the cyclohexadepsipeptide enniatin, a host-nonspecific phytotoxin. Enniatins are synthesized by the 347-kDa multifunctional enzyme enniatin synthetase. In the present study, 36 Fusarium strains derived from a wide range of host plants were characterized with respect to enniatin production in different media. Thirteen of these strains produced enniatins on one or more of these media. To determine whether enniatin production affected virulence, an assay on potato tuber tissue was performed. Seven enniatin-producing and 16 nonproducing strains induced necrosis of potato tuber tissue, so that enniatin synthesis is not essential for the infection of potato tuber tissue. The application of a mixture of enniatins to slices of potato tuber, however, caused necrosis of the tissue. Therefore, enniatin production by the enniatin-synthesizing strains may affect their pathogenicity. The enniatin synthetase gene (esyn1) of Fusarium scirpi ETH 1536 was used as a probe to determine if similar sequences were present in the strains examined. In Southern blot analyses, DNA sequences hybridizing with the esyn1 probe were present in all but two of the strains examined. In some cases, enniatin-nonproducing strains had the same hybridization pattern as enniatin producers.

Highly conserved N-methyltransferases as an integral part of peptide synthetases

The methyltransferase portion of the N-methyl-peptide-synthetase gene, synthesizing enniatin from Fusarium sambucinum, was amplified with the polymerase chain reaction (PCR) using primers derived from the highly conserved sequences of the flanking peptide synthetase domain. The deduced amino acid sequence of the product shares high similarity to the 430 amino acid methyltransferase portion of enniatin synthetase of Fusarium scirpi and the corresponding portions of another fungal peptide synthetase catalyzing the biosynthesis of the N-methylated cyclopeptide cyclosporin. As the methyltransferase portions show only local similarity to motifs apparently conserved within methyltransferases, the segments of peptide synthetases involved in the biosynthesis of bioactive peptides represent a new class of S-adenosyl-L-methionine dependent methyltransferases.

Arrangement of catalytic sites in the multifunctional enzyme enniatin synthetase

Enniatin synthetase is an N-methyl peptide synthetase comprising 3131 amino acids. Catalytic sites of the 347-kDa multifunctional enzyme were mapped by N-terminal sequencing of substrate affinity-labelled enzyme fragments formed by proteolysis, and functional studies of purified enniatin synthetase fragments. An N-terminal 200-kDa fragment containing the cofactor 4'-phosphopantetheine was able to activate D-hydroxyisovaleric acid (D-HOiVl) as a thioester. The N-termini of two [14C]HOiVl-labelled enzyme fragments could be assigned to amino acid position 429 within the N-terminal conserved enniatin synthetase portion named EA. This portion of about 600 amino acids shares high similarity to microbial peptide synthetase regions. A 68-kDa L-[14C]Val-labelled enniatin synthetase fragment was localized at amino acid position 2294 within the second C-terminal conserved protein portion EB. Additionally enniatin synthetase was labelled with isovaleryl-L-[14C]Val, an analogue of the D-hydroxyisovaleryl-L-Val intermediate in enniatin biosynthesis. The N-terminus of a 30-kDa isovaleryl-L-[14C]Val-labelled enniatin synthetase fragment was mapped in a C-terminal segment of the protein portion EA. The same N-terminal sequence was obtained from a 60-kDa enniatin synthetase fragment modified with [3H]beta Ala, a constituent of the cofactor 4'-phosphopantetheine. This indicates the presence of the cofactor in this protein fragment. Localization of the methyltransferase function of enniatin synthetase in an amino acid portion integrated into region EB was achieved by N-terminal sequencing of a photolabelled S-[methyl-14C]adenosyl methionine 45-kDa fragment and the identification of a photolabelled peptide Asn-Leu-Asn-Pro-Gly-Leu-Asn-Ser-Tyr.

Bacterial expression of catalytically active fragments of the multifunctional enzyme enniatin synthetase

Enniatin synthetase catalyzes the biosynthesis of N-methylated cyclohexadepsipeptides. The 347 kDa enzyme is encoded by the esyn1 gene of Fusarium scirpi and contains two domains (EA and EB) homologous to each other and to regions of other microbial peptide synthetases. Parts of the esyn1 gene were subcloned in frame to a small lacZ gene portion of Escherichia coli expression vectors. Overproduced recombinant proteins showed a high tendency towards inclusion body formation and could be only partially dissolved in 8 M urea or 6 M guanidine hydrochloride. After renaturation, a 121 kDa recombinant protein representing the N-terminal conserved domain EA of enniatin synthetase was shown to activate D-hydroxyisolvaleric acid via adenylation. Similarly, a 158 kDa recombinant protein comprising the C-terminal conserved domain EB catalyzed the activation of the substrate amino acid (e.g. L-valine). Moreover, this protein could be photolabeled with S-[methyl-14C]adenosyl-L-methionine, (AdoMet) indicating the presence of the methyltransferase. Both functions, L-valine activation and AdoMet binding, could be assigned to a 108 kDa recombinant protein encompassing the A and the M segment of domain EB. The fact that a 65 kDa recombinant protein representing the M portion could be photolabeled, indicated the localization of the methyltransferase in this region. Three deletion mutants of the 65 kDa protein were shown to be inactive with respect to UV-induced AdoMet labeling.

Cooperation of GATA-1 and Sp1 can result in synergistic transcriptional activation or interference

GATA-1 is a lineage-restricted transcription factor. Virtually all erythroid-expressed genes contain GATA recognition sites in their regulatory elements. Cotransfection/transactivation assays have revealed that, although GATA-1 as the only cell-restricted transcription factor is sufficient to activate some of the erythroid-specific promoters, not all such promoters are responsive, suggesting a requirement for cooperation with other factors. To study the interaction of GATA-1 with other transactivators, we analyzed sequence motifs of the human gamma-globin promoter as response system by in vitro transcription and by transfections into erythroid K562 cells or into heterologous Drosophila SL2 cells. GATA-1 alone did not activate the promoter. However, GATA-1 exerted an effect in concert with the ubiquitous transactivator Sp1. Depending on the factor concentrations and the sequence context of the cognate binding sites, this interaction could result in synergistic transcriptional activation or in interference. GATA-1 and Sp1 did not cooperate in DNA binding when tested in vitro. This suggests that the functional cooperation is mediated by protein interactions with additional factor(s) which transmit the activator signal. The Sp1-binding CCACCC motif was found to be critical for high activity of the gamma-globin promoter. This site overlaps with a recognition sequence for members of the NFI/CTF family. NFI did not transactivate, but it interfered with Sp1-mediated stimulation and hence with Sp1/GATA-1 cooperation. These data, together with phylogenetic evidence, suggest that the CCACCC region is likely to represent a regulatory switch element.

Molecular characterization of the enniatin synthetase gene encoding a multifunctional enzyme catalysing N-methyldepsipeptide formation in Fusarium scirpi

The gene encoding the multifunctional enzyme enniatin synthetase from Fusarium scirpi (esyn1) was isolated and characterized by transcriptional mapping and expression studies in Escherichia coli. This is the first example of a gene encoding an N-methyl peptide synthetase. The nucleotide sequence revealed an open reading frame of 9393 bp encoding a protein of 3131 amino acids (M(r) 346,900). Two domains designated EA and EB within the protein were identified which share similarity to each other and to microbial peptide synthetase domains. In contrast to the N-terminal domain EA, the carboxyl terminal domain EB is interrupted by a 434-amino-acid portion which shows local similarity to a motif apparently conserved within adenine and cytosine RNA and DNA methyltransferases and therefore seems to harbour the N-methyl-transferase function of the multienzyme.

Genetics of actinomycin C production in Streptomyces chrysomallus

Three distinct classes of mutations affecting the biosynthesis of actinomycin have been established in Streptomyces chyrsomallus by crossing various actinomycin-nonproducing mutants with each other by protoplast fusion. In crosses between members of different classes of mutations, actinomycin-producing recombinant progeny arose, whereas in crosses between members of the same class, no actinomycin-producing recombinants were seen. Biochemical examination of a number of mutants revealed that the expression of all actinomycin synthetases was reduced by about 1 order of magnitude in mutants belonging to class II. In mutants of class I, the specific activities of the actinomycin synthetases were comparable with those measured in their actinomycin-producing parents. Feeding experiments with 4-methyl-3-hydroxyanthranilic acid (4-MHA), the biosynthetic precursor of the chromophore moiety of actinomycin, with representative mutants of the three genetic classes revealed formation of actinomycin in minute amounts by mutants of class I. It is suggested that mutants belonging to class I are mutated at a genetic locus involved in the biosynthesis of 4-MHA. Mutants belonging to class II appear to carry mutations at a locus involved in the regulation of the expression of the actinomycin synthetases. The role of the locus in class III mutations could not be assigned. Mapping studies in S. chrysomallus based on conjugal matings revealed the chromosomal linkage of all three loci. Mutations belonging to classes I and III were closely linked. Their genetic loci could be localized in a map interval of the chromosomal linkage group which is significantly distant from the gene locus represented by mutations belonging to class II.

Genetic analysis in Streptomyces chrysomallus

A circular linkage map was developed for Streptomyces chrysomallus, a producer of actinomycin C. The map order of various marker loci was deduced from matings and to a minor extent from protoplast fusions. The map strongly resembles that of Streptomyces coelicolor A3(2). The recombination frequencies were low and highly variable (from 10(-9) to 5 X 10(-6]. Plasmid pIJ303 expressed its thiostrepton resistance gene in S. chrysomallus but did not promote chromosomal transfer or induce the Ltz+ phenotype. The data provide a background of genetics for investigations of antibiotic synthesis in this strain.