A truncated precursor form of prostate-specific antigen is a more specific serum marker of prostate cancer

Prostate-specific antigen (PSA) is a widely used serum marker for prostate cancer (PCa) but has limited specificity for distinguishing early PCa from benign prostatic hyperplasia, because both PCa and benign prostatic hyperplasia release PSA into the serum. We have identified previously a truncated form of precursor PSA (pPSA) in prostate tumor extracts consisting of PSA with a serine-arginine pro leader peptide ([-2]pPSA) instead of the normally expressed 7 amino acid pro leader peptide. In the current study we developed monoclonal antibodies to detect [-2]pPSA and other isoforms of pPSA for Western blot analysis. PSA was immunoaffinity purified from 100 to 200 ml of serum from each of five men with biopsy-proven cancer and three biopsy-negative men, all with total PSA levels in the diagnostically relevant range near 10 ng/ml. The truncated [-2]pPSA was estimated to range from 25 to 95% of the free PSA in the five PCa samples but only 6-19% of the free PSA in the biopsy-negative men. Immunohistochemical studies showed positive staining for [-2]pPSA in PCa epithelium and that [-2]pPSA was enriched in cancer cell secretions. In vitro activation studies showed that human kallikrein 2 and trypsin readily activated full-length pPSA but were unable to activate [-2]pPSA to mature PSA. Thus, [-2]pPSA, once formed, is a stable but inactive isoform of PSA. Truncated [-2]pPSA may represent an important new diagnostic marker for the early detection of PCa.     

游离前列腺特异性抗原与总前列腺特异性抗原比值在前列腺癌鉴别诊断中的应用

 目的 探讨游离前列腺特异性抗原（fPSA）与总前列腺特异性抗原（tPSA）比值在前列腺癌（PCa）鉴别诊断中的意义。方法 采用电化学免疫发光技术对86例前列腺良性增生（BPH）45例PCa患者和60例健康男性体检者（正常对照组）血清fPSA和tPSA同时进行测定，并计算出fPSA／tPSA，进行统计分析。结果 BPH、PCa组tPSA水平明显高于正常对照组（P＜0.05）。PCa组和BPH组的血清tPSA差异亦有统计学意义，但当tPSA在4.0 ~ 10.0 μg／L范围时，PCa组血清fPSA／tPSA比值却明显低于BPH组（P＜0.01）。把fPSA／tPSA比值划分成8个区间，当fPSA／tPSA比值15 ％作为诊断灰区PCa诊断的临界值时，诊断的敏感性、特异性、阳性预测值、阴性预测值及正确诊断指数分别为72.8 %、67.5 %、62.5 %、82.2 %、50.2 %。结论 当血清tPSA处于诊断灰区时，联合检测fPSA／tPSA比值可明显提高tPSA对PCa早期诊断的特异性。     

Tumor markers in prostate cancer--clinical significance and future prospect of prostate specific antigen (PSA)

Prostate specific antigen (PSA), which has high organ specificity, is an excellent tumor marker that has played a significant role in the diagnosis and treatment of prostate cancer. Screening for prostate cancer using PSA is now widely employed in Japan, and increased detection of cases with organ-confined prostate cancer is hoped to result in a decreased number of cancer-specific deaths. Although PSA has also played a critical role in as a marker for staging, assessment of treatment, and recurrence of prostate cancer, many useless biopsies are performed due to its low cancer specificity. To increase the specificity in prostate cancer detection, PSA-related markers including PSAD (PSAPZD), PSAV, and age-specific PSA were advocated, and the ratio of free PSA to total PSA (% free PSA) is also used in a clinical setting. However, since those markers can not satisfactorily exclude benign prostate diseases, various molecular forms of PSA have been analyzed using proteomics and glycomics. Recently, it was demonstrated that plasma free PSA consisted of precursor PSA (pPSA) and other isoforms, suggesting that [-2] pPSA may be a helpful marker for prostate cancer. Our group reported that a sugar chain structure of PSA in the serum of prostate cancer patients is different from that of patients with benign prostate hyperplasia. The different sugar chain structure of PSA can be easily detected by a conventional method and is expected to be useful for differential diagnosis between malignant and benign prostate diseases.     

Evaluation of free-to-total prostate specific antigen ratio in the diagnosis of prostate cancer

It'sreportedthatfreetototalprostatespecificantigenration(f/tPSA)canprovidemorebenefitthanthesingleuseofprostatespecificantigen(PSA)inthediagnosisofprostatecancer(PCa).WemeasuredserumPSAandfPSAlevelsin62casesofbenignprostatichyperplasia(BPH)and40casesofPCausingradioimmunoassay,withpatients'agerange59y-89y.RESULTSPSA,fPSAandf/tPSAareshowninTable1.BoththesetwogroupsshowslinearcorrelationbetweenPSAandfPSA,correlationcoefficientofBPHis0.55(P<0.01),ofPCais0.44(P<0.01).Twoslopesha…     

The clinical utility of measuring total PSA, PSA density, gamma-seminoprotein and gamma-seminoprotein/total PSA in prostate cancer prediction

BACKGROUND: To evaluate whether serum total prostate-specific antigen (PSA), PSA density (serum total PSA level divided by prostate volume), gamma-seminoprotein and gamma-seminoprotein/total PSA ratio could predict prostate cancer (PCa) prior to biopsy. METHODS: A total of 316 consecutive patients who had undergone transrectal prostate biopsy and/or transurethral resection were examined. The prostate volume was determined by transrectal ultrasonography (TRUS) and the ability of the above-mentioned four variables to distinguish PCa from benign prostatic hyperplasia (BPH) was evaluated. RESULTS: PCa was detected in 61 cases. Receiver-operating characteristic (ROC) analysis revealed that both the PSA density and serum total PSA were the most useful predictors of PCa among the four variables. For the patients with a serum total PSA level of 4.1-10.0 ng/ml, PSA density was significantly more accurate than total PSA (p < 0.005). An optimum PSA density value of 0.18 was chosen as a cutoff because it showed the highest sum of sensitivity and specificity, 92 and 54%, respectively. Using this PSA density cutoff, the number of biopsies could have been reduced to 57 from 63% when compared with a PSA density of 0.15. CONCLUSIONS: PSA density was significantly more accurate than other variables in predicting PCa. To avoid unnecessary biopsies, the PSA density cutoff value of 0.18 would be recommendable for determining a prostate biopsy for Japanese males with a serum total PSA level of 4.1-10.0 ng/ml.     

Frequency of PSA-mRNA-bearing cells in the peripheral blood of patients after prostate biopsy

Transrectal ultrasound (TRUS) guided prostate biopsy is standard diagnostic procedure for prostate cancer (PCa). However, possibility of dissemination of cancer cells by biopsy is not negligible. To investigate this possibility, we examined prostate specific antigen (PSA)-bearing cells in peripheral blood of the 108 patients before and after prostate biopsy. Peripheral blood samples were obtained from 108 patients with elevated serum PSA (sPSA) levels, who had undergone sextant prostate biopsy using TRUS. The presence of PSA-mRNA bearing cells was examined using the nested RT-PCR method enabling detection of one LNCaP cell diluted in 1 ml of whole blood. Among 108 patients, 62 and 46 were diagnosed with benign prostatic hyperplasia (BPH) and PCa, respectively. PSA-mRNA was detected in 3 PCa cases but in no BPH patients before and after biopsy, and in 16 BPH (25.8%) and in 21 PCa (45.7%) patients only after biopsy (P< 0.01). The patients with positive mRNA before biopsy had higher sPSA (P< 0.001), and those after biopsy had higher sPSA and PSA density (PSAD) levels (P< 0.05). Positive PSA-mRNA cases had more cancer involved biopsy cores than the negative PSA-mRNA cases (P< 0.001). Although further investigations are needed, the present findings suggest that prostate biopsy might scatter prostate cells in the blood stream especially in cases with high sPSA and, thus, might contribute to tumour spreading in the cases of prostate cancer.     

A higher PSA-density cut-off level in patients with intermediate PSA values for the early detection of prostate cancer

The use of PSA-density (PSAD) as an indicator for prostate biopsy at intermediate PSA values has generated controversy. There are investigators who consider that the determination of PSAD is futile, and that it is better to do a prostate biopsy based on PSA values alone, TRUS (Transrectal Ultrasound) findings and/or DRE examinations. Asian countries, especially in the Far East, are considered to have a low incidence of prostate cancer (PCa). However, based on western references, we still measure PSA-density with a cut-off level of 0.15 to promote prostate biopsy in patients with intermediate PSA values (4.1-10.0 ng/ml). Our study aims to evaluate the usefulness of PSAD as an indication for biopsy in patients with intermediate serum PSA values. To evaluate the usefulness of this indicator, we conducted a retrospective study of 132 uncatheterized (to minimize potential bias) BPH and PCa cases that were hospitalized in our department between 1995-1997 (3 years). This group comprised 127 BPH and 5 PCa patients. Mean age was 66.1 +/- 7.69 years; mean PSA was 7.92 +/- 9.289 ng/ml; mean prostate volume was 54.1 +/- 26.72 cc; mean PSAD was 0.15 +/- 0.185. More specifically, there were 49 patients with intermediate PSA values (47 BPH & 2 PCa). The receiver operator characteristic (ROC) curve revealed an optimum cut-off level of 0.19. At this level of PSA density, the measured sensitivity was 100% with a specificity of 79%. We concluded that, in our uncatheterized patients (without retention) series, the PSAD cut-off level for prostate biopsy (0.19) was higher than that in the western world (0.12 or 0.15).     

ROC曲线分析波谱定量分析在前列腺癌中的诊断价值

目的：探讨MR波谱（magnetic resonance spectroscopy,MRS）定量分析方法在前列腺癌（prostatic carci-noma,PCa）诊断中的意义。方法：对所有疑诊PCa患者行前列腺磁共振波谱分析,酶联免疫法测定血清前列腺特异抗原（PSA）,经直肠超声测定前列腺体积,计算前列腺特异抗原密度（PSAD）,经超声引导下系统穿刺活检证实的71例良性前列腺增生患者和31例PCa患者,分别测量各个位置（胆碱＋肌酸）/枸橼酸盐[（Cho＋Cre）/Cit]的比值,并取均值。结果：前列腺穿刺阳性组的PSA、PSAD及（Cho＋Cre）/Cit的比值分别为23.73±19.06、0.62±0.42、2.33±0.66;前列腺穿刺阴性组的PSA、PSAD及（Cho＋Cre）/Cit的比值分别为8.61±4.47、0.15±0.13、0.73±0.39。阳性组的检测值均较阴性组高（P〈0.05）。PSA、PSAD及（Cho＋Cre）/Cit在ROC曲线下的面积分别为0.71、0.76、0.84。在保持93.5%的敏感性以上时,PSA、PSAD及（Cho＋Cre）/Cit的特异性是43.7%、63.4%和83.1%,（Cho＋Cre）/Cit较PSA、PSAD能更好地检出PCa。结论：MRS分析方法定量评价PCa的代谢改变,有助于PCa的早期诊断,同时结合PSA、PSAD更有助于前列腺癌诊断的特异性。     

Progression of prostate cancer: diagnostic and prognostic utility of prostate-specific antigen, alpha2-macroglobulin, and their complexes

We previously reported cases of advanced prostate cancer (PCa) in which serum alpha2-macroglobulin (alpha2M) levels were markedly decreased to less than approximately 50 mg/dl whereas serum prostate-specific antigen (PSA) levels were remarkably increased. These cases were not complicated with disseminated intravascular coagulation (DIC). In this study, we measured serum PSA and alpha2M in 108 patients with either benign prostatic hyperplasia (BPH) or PCa to elucidate the relationship between PSA, i.e. the serum protease derived from the prostatic tissue, and alpha2M, i.e. the protease inhibitor that was the most abundantly contained in serum. alpha2M was determined by ELISA, total PSA and PSA-alpha1-antichymotrypsin (PSA-ACT) by EIA, and free-PSA by RIA in 44 patients with untreated BPH and 64 patients with untreated PCa. The ready association of alpha2M and PSA was assessed using Western blotting to identify complexes of the two. Levels of total serum PSA correlated positively with those of PSA-ACT in PCa (r = 0.99, p < 0.001), and both levels increased with advancing stage of disease. In contrast, the serum-free PSA/total PSA ratio (free/total PSA) and alpha2M levels decreased as the disease progressed. However, only the free/total PSA ratio attained significant difference for localized cancer in stage T1,2 versus BPH (p < 0.05). In stage M1b PCa, in which serum PSA levels were very high, there was a negative correlation between the total PSA and alpha2M values (r = -0.57, p < 0.05). In addition, serum alpha2M levels tended to decrease with progression of PCa. Serum total PSA levels correlated tightly with serum PSA-ACT levels. It is suggested that PSA is usually complexed with ACT in the serum. Free/total PSA was useful for differential diagnosis between early cancer and BPH. Levels of serum alpha2M of less than 50 mg/dl in PCa patients may indicate a possibility of bone metastases.     

PSAD和游离/总PSA比值在前列腺癌诊断中的意义

 目的　比较研究前列腺特异抗原(PSA)、PSA密度(PSAD)和游离/总PSA比值(F/TPSA)在前列腺癌诊断中的价值。方法　41例前列腺增生和22例前列腺癌患者,术前用放免法测定血清PSA和游离PSA。所有患者经直肠腔内B超测出前列腺体积,求得PSAD,用t检验比较分析。结果　前列腺癌组的PSA、PSAD均显著高于前列腺增生组(PSA：46.3±33.8μg/Lvs7.04±6.91μg/L,P=0.000021;PSAD：1.43±1.21μg。L-1。ml-1vs0.14±0.15ng。ml-1。ml-1,P=0.000055)。两组的F/TPSA比值无显著差异(0.18±0.11vs0.22±0.18,P=0.34)。结果　PSA和PSAD是鉴别前列腺癌的良好指标,对于PSA可疑者,PSAD有助于区分前列腺癌和前列腺增生,本组游离/总PSA比值不能帮助鉴别诊断。     

Expression of soluble urokinase plasminogen activator receptor may be related to outcome in prostate cancer patients

The urokinase-type plasminogen activator receptor (uPAR) exists as a GPI anchored glycoprotein (Mr=50-60 kDa) on the surface of various cell types. This receptor can be bound by or cleaved by urokinase. The cleaved receptor, soluble urokinase-type plasminogen activator receptor (suPAR), with an Mr=35 kDa has no known physiological function and can be identified circulating in the blood of normal individuals. Although no function has been characterized, the soluble receptor has been reported to be of clinical significance. The objective of this study is to characterize novel serum markers that can be used for the early detection of prostate cancer and to predict patient prognosis. Thirty-nine patients at the University of Yaounde I, Yaounde, Cameroon, West Africa were examined for prostatic disorders. Of these, 46% were diagnosed with benign prostate hyperplasia (BPH), while 44% of the patients were diagnosed via biopsy with prostate cancer and graded accordingly. Here we show that serum from patients with BPH or prostate cancer contains elevated levels of suPAR. To examine the significance of suPAR as a diagnostic factor, we used a suPAR ELISA kit and compared these results with serum levels of prostate specific antigen (PSA), the current diagnostic marker for prostate cancer. PSA and serum suPAR levels in BPH and cancer patients were greatly elevated in the majority of patients, while others had undetectable levels of either. Serum levels of suPAR were high in cancer patients as well as, although to a lesser degree, in patients with BPH. Cancer patients who died during the follow-up period were found to have consistently higher serum suPAR levels than correlating serum PSA levels. These preliminary findings are the first evaluating serum suPAR levels as a possible diagnostic marker for the early detection of prostate cancer and for the prediction of patient prognosis.     

前列腺特异性抗原的检测对前列腺癌及前列腺增生的诊断意义

目的　探讨血清总前列腺特异性抗原 (t PSA)、游离PSA (f PSA)、PSA密度 (PSAD )及其f PSA/t PSA比值对前列腺癌 (PCa)及前列腺增生 (BPH )的诊断价值。方法　采用酶联免疫分析方法 (ELISA )检测未经治疗的 62例BPH患者和 2 4例PCa患者血清f PSA、t PSA水平 ,并计算f PSA/t PSA值和PSAD ,对检测结果进行统计学处理。结果　BPH组与PCa组的f PSA、t PSA水平均明显高于对照组 (P <0 .0 1) ;前列腺癌组的f PSA /t PSA值明显小于对照组及前列腺癌增生组 (P <0 .0 1) ;PCa组PSAD明显大于对照组和BPH组 (P <0 .0 1)。结论　检测f PSA/t PSA和PSAD比单一检测f PSA、t PSA可显著提高对PCa诊断的特异性及符合率 ,对前列腺体积较大的BPH和PCa患者 ,检测PSAD更有意义     

Value of free-to-total prostate-specific antigen ratio for detection and staging of prostate cancer

Background. We aimed to evaluate the clinical usefulness of measurement of the free-to-total (F/T) ratio of prostate-specific antigen (PSA) for the differentiation of prostate cancer from benign prostate hyperplasia (BPH) and for the staging of prostate cancer. Values for PSA density (PSAD) and PSAD adjusted to the transition zone volume (PSAD-T) were also evaluated in patients with mildly elevated PSA levels (4.1–10 ng/ml). Methods. Total and free PSA and the F/T ratio were determined in 80 men with prostate cancer and 48 men BPH before treatment. PSA levels were measured with a chemiluminescent enzyme immunoassay. Results. Patients with prostate cancer had a significantly lower F/T ratio than those with BPH. A cut-off value of 14% for the F/T ratio provided a positive predictive value of 81.6% and a negative predictive value of 65.4%. The F/T ratio did not differ between patients with clinically localized and metastatic prostate cancer. In patients with a PSA value of 4.1–10 ng/ml, a cut-off value of 14% for the F/T ratio provided a sensitivity of 66.7% and a specificity of 76.2%. Sixty percent of the missed cancer in patients with an F/T value of 14% or more could be rescued using the PSAD value. Conclusion. Measurement of the F/T PSA ratio has good sensitivity and specificity in distinguishing prostate cancer from BPH, especially in patients with a PSA level of 4.1–10 ng/ml. However, compared with serum PSA level, the F/T PSA ratio is not valuable for the clinical staging of prostate cancer. Received: June 23, 1999 / Accepted: September 22, 1999     

Identification of candidate prostate cancer biomarkers in prostate needle biopsy specimens using proteomic analysis

Although serum prostate specific antigen (PSA) is a well-established diagnostic tool for prostate cancer (PCa) detection, the definitive diagnosis of PCa is based on the information contained in prostate needle biopsy (PNBX) specimens. To define the proteomic features of PNBX specimens to identify candidate biomarkers for PCa, PNBX specimens from patients with PCa or benign prostatic hyperplasia (BPH) were subjected to comparative proteomic analysis. 2-DE revealed that 52 protein spots exhibited statistically significantly changes among PCa and BPH groups. Interesting spots were identified by MALDI-TOF-MS/MS. The 2 most notable groups of proteins identified included latent androgen receptor coregulators [FLNA(7-15) and FKBP4] and enzymes involved in mitochondrial fatty acid beta-oxidation (DCI and ECHS1). An imbalance in the expression of peroxiredoxin subtypes was noted in PCa specimens. Furthermore, different post-translationally modified isoforms of HSP27 and HSP70.1 were identified. Importantly, changes in FLNA(7-15), FKBP4, and PRDX4 expression were confirmed by immunoblot analyses. Our results suggest that a proteomics-based approach is useful for developing a more complete picture of the protein profile of PNBX specimen. The proteins identified by this approach may be useful molecular targets for PCa diagnostics and therapeutics.     

Binding of serum prostate antigen to concanavalin A in patients with cancer or hyperplasia of the prostate

The percentage of nonglycosylated prostate-specific antigen (PSA) was measured in the serum of 15 prostate cancer patients and 15 patients with benign hyperplasia of the prostate. The larger part of serum PSA in both groups was glycosylated, but while in carcinoma of the prostate the mean percentage of nonglycosylated PSA was 38.4 +/- 6.5, in benign prostate hyperplasia (BPH) only a mean of 14.2 +/- 4.3% of the PSA was nonglycosylated. These significantly higher results (p less than 0.001) suggest a different pattern of release of PSA from cancer cells and from hyperplastic or normal cells. Since in a part of the BPH we encounter elevations of PSA similar to the levels found in neoplasms, the degree of concanavalin A binding can provide an additional means in differentiating between benign and malignant lesions.     

Metabolic markers in blood can separate prostate cancer from benign prostatic hyperplasia

Background:

An individualised risk-stratified screening for prostate cancer (PCa) would select the patients who will benefit from further investigations as well as therapy. Current detection methods suffer from low sensitivity and specificity, especially for separating PCa from benign prostatic conditions. We have investigated the use of metabolomics analyses of blood samples for separating PCa patients and controls with benign prostatic hyperplasia (BPH).

Methods:

Blood plasma and serum samples from 29 PCa patient and 21 controls with BPH were analysed by metabolomics analysis using magnetic resonance spectroscopy, mass spectrometry and gas chromatography. Differences in blood metabolic patterns were examined by multivariate and univariate statistics.

Results:

By combining results from different methodological platforms, PCa patients and controls were separated with a sensitivity and specificity of 81.5% and 75.2%, respectively.

Conclusions:

The combined analysis of serum and plasma samples by different metabolomics measurement techniques gave successful discrimination of PCa and controls, and provided metabolic markers and insight into the processes characteristic of PCa. Our results suggest changes in fatty acid (acylcarnitines), choline (glycerophospholipids) and amino acid metabolism (arginine) as markers for PCa compared with BPH.     

分子标志物在前列腺癌早期诊断中的进展

较多的研究显示,血清PSA值指导前列腺癌(prostate cancer,Pca)早期诊断的优势不足,例如PSA值在4～10 ng/mL.时,Pca穿刺阴性率占70%～80%.然而,阴性的穿刺结果并不能完全排除肿瘤的存在.寻找敏感性和特异性更高的肿瘤生物标志物一直是Pca研究的热点.目前,PSA衍生物、PCA3、TMPRSS2:ETS、GSTP1、AMACR、COLPH2、EPCA和肌氨酸以及多瘤标的联合应用研究受到广泛关注.本文中我们综述了这些分子标志物的研究近况,展望了多瘤标组合在Pca早期诊断中的价值和应用前景,为Pca的早期诊断和预后监测提供参考.     

前列腺特异膜抗原对前列腺疾病的临床诊断意义

目的评价血清中前列腺特异膜抗原（PSMA）浓度对前列腺疾病的辅助诊断意义。方法采用Western印迹分析检测患者血清中PSMA的浓度,前列腺特异抗原（PSA）检测采用通用的免疫化学发光法检测。分析二者在不同分组中的浓度差异及相关性。结果前列腺癌患者的血清中PSMA浓度显著高于正常人群,良性前列腺增生和前列腺炎的患者则低于正常人群,而PSA浓度无论是前列腺癌还是前列腺良性病变均高于正常人。结论前列腺特异膜抗原浓度可以作为区分前列腺癌和良性前列腺增生的辅助诊断标志物。     

血清PSA联合PSAD检测对前列腺癌的诊断价值

目的:探讨血清前列腺特异抗原（PSA）、前列腺特异抗原密度（PSAD）对前列腺癌的诊断价值。方法:检测经病理确诊的57例前列腺癌、125例前列腺增生患者的血清PSA。经直肠超声测定其前列腺的体积（PV）并计算PSAD。结果:前列腺癌组患者的PSA、PSAD明显高于前列腺增生组(P<0.05)。PSA值在4.1-10.0,10.1-20.0,>20.0ng/ml区间时PCa诊断率分别为8.8%,36.8%,54.4%。前列腺癌组的ROC曲线图中PSAD的AUC值（0.682）高于PSA的AUC值（0.601）,当取PSAD≥0.18ng/（ml·cm3）时,敏感性为84.5%,特异性为78.6%。比较58例重复穿刺患者的PSA、PSAD,只有PSAD差异有统计学意义(P<0.05)。结论:PSA动态监测结合PSAD是重复穿刺的重要参考指标,PSAD是PSA对前列腺癌诊断的有益补充。