Human kallikrein 10: a novel tumor marker for ovarian carcinoma?

Methodology and Applications of Disease Biomarker Identification in Human Serum

Biomarkers are biomolecules that serve as indicators of biological and pathological processes, or physiological and pharmacological responses to a drug treatment. Because of the high abundance of albumin and heterogeneity of plasma lipoproteins and glycoproteins, biomarkers are difficult to identify in human serum. Due to the clinical significance the identification of disease biomarkers in serum holds great promise for personalized medicine, especially for disease diagnosis and prognosis. This review summarizes some common and emerging proteomics techniques utilized in the separation of serum samples and identification of disease signatures. The practical application of each protein separation or identification technique is analyzed using specific examples. Biomarkers of cancers of prostate, breast, ovary, and lung in human serum have been reviewed, as well as those of heart disease, arthritis, asthma, and cystic fibrosis. Despite the advancement of technology few biomarkers have been approved by the Food and Drug Administration for disease diagnosis and prognosis due to the complexity of structure and function of protein biomarkers and lack of high sensitivity, specificity, and reproducibility for those putative biomarkers. The combination of different types of technologies and statistical analysis may provide more effective methods to identify and validate new disease biomarkers in blood.

Diagnostic Accuracy of Serum Kallikrein-Related Peptidases for Ovarian Cancer: A Systematic Review and Meta-Analysis

OBJECTIVE

At present, considerable efforts have been made to identify new cancer-specific markers for ovarian cancer (OC) diagnosis and the kallikrein-related peptidases (KLKs) family is one of the most studied candidates. This meta-analysis aims to evaluate the pooled diagnostic value of serum KLK measurement for diagnosing OC.

METHODS

The Cochrane Library, PubMed, Excerpt Medica Database were searched for all relevant literature. The Quality Assessment for Studies of Diagnostic Accuracy tool was applied to assess the quality of enrolled studies. Statistical analysis was conducted by using Stata 13.0 software and Meta-Disc.

RESULTS

A total of 15 studies from 13 articles were considered eligible for inclusion in the present analysis. The following pooled parameters were calculated by using the bivariate model: sensitivity of 0.582 (95% confidence interval [CI], 0.517-0.644), specificity of 0.909 (95% CI, 0.833-0.952), positive likelihood ratios of 6.367 (95% CI, 3.330-12.172), negative likelihood ratios of 0.460 (95% CI, 0.388-0.546), diagnostic odds ratio of 13.831 (95% CI, 6.460-29.614), respectively.

CONCLUSIONS

Kallikrein-related peptidase seems to be a promising candidate biomarker in diagnosing OC, but the associated poor sensitivity of KLK individually may limit its value in clinical application. To resolve this problem, the combination of KLK and other markers may offer improved performance than a single marker.

Diagnostic value of KLK6 as an ovarian cancer biomarker: A meta-analysis

Kallikrein-related peptidase 6 (KLK6) is a new potential serum biomarker of ovarian cancer. The aim of the present study was to assess the diagnostic value of KLK6 systematically for ovarian cancer. All the selected studies regarding the changes of KLK6 in ovarian cancer were published prior to April 2015. Five studies involving 485 patients with ovarian cancer, 420 benign cysts and 245 healthy controls met the inclusion criteria. The value of sensitivity, specificity, positive-likelihood ratio (LR+), negative-likelihood ratio (LR-) and area under the receiver operating characteristic curve (ROC) were obtained. All these indices were used to evaluate the diagnostic value of KLK6 for ovarian cancer. The values of sensitivity, specificity, LR+ and LR- (95% confidence interval) of KLK6 were 0.50 (0.47–0.54), 0.91 (0.89–0.93), 7.20 (3.34–15.52) and 0.51 (0.43–0.62), respectively. The area under the summary ROC of KLK6 was 0.86. The index of Q* was 0.79. In conclusion, KLK6 showed high specificity for the diagnosis of ovarian cancer. It can improve the diagnostic accuracy of cancer antigen 125 (CA125). A combined panel of CA125 and KL K6 shows a high diagnostic efficiency for advanced ovarian cancer. Owing to the small number of studies and lack of samples, additional studies meeting the inclusion criteria are required to further analyze the diagnostic value of KLK6 for ovarian cancer.

Kallikreins - The melting pot of activity and function

The human tissue kallikrein and kallikrein-related peptidases (KLKs), encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Because of the broad spectrum of processes that are modulated by kallikreins, these proteases are the subject of extensive investigations. This review brings together basic information about the biochemical properties affecting enzymatic activity, with highlights on post-translational modifications, especially glycosylation. Additionally, we present the current state of knowledge regarding the physiological functions of KLKs in major human organs and outline recent discoveries pertinent to the involvement of kallikreins in cell signaling and in viral infections. Despite the current depth of knowledge of these enzymes, many questions regarding the roles of kallikreins in health and disease remain unanswered.

Function and clinical relevance of kallikrein-related peptidases and other serine proteases in gynecological cancers

Gynecological cancers, including malignant tumors of the ovaries, the endometrium and the cervix, account for approximately 10% of tumor-associated deaths in women of the Western world. For screening, diagnosis, prognosis, and therapy response prediction, the group of enzymes known as serine (Ser-)proteases show great promise as biomarkers. In the present review, following a summary of the clinical facts regarding malignant tumors of the ovaries, the endometrium and the cervix, and characterization of the most important Ser-proteases, we thoroughly review the current state of knowledge relating to the use of proteases as biomarkers of the most frequent gynecological cancers. Within the Ser-protease group, the kallikrein-related peptidase (KLK) family, which encompasses a subgroup of 15 members, holds particular promise, with some acting via a tumor-promoting mechanism and others behaving as protective factors. Further, the urokinase-type plasminogen activator (uPA) and its inhibitor PAI-1 (plasminogen activator inhibitor-1) seem to play an unfavorable role in gynecological tumors, while down-regulation of high-temperature requirement proteins A 1, 2 and 3 (HtrA1,2,3) is associated with malignant disease and cancer progression. Expression/activity levels of other Ser-proteases, including the type II transmembrane Ser-proteases (TTSPs) matriptase, hepsin (TMPRSS1), and the hepsin-related protease (TMPRSS3), as well as the glycosyl-phosphatidylinositol (GPI)-anchored Ser-proteases prostasin and testisin, may be of clinical relevance in gynecological cancers. In conclusion, proteases are a rich source of biomarkers of gynecological cancer, though the enzymes' exact roles and functions merit further investigation.

Overexpression of kallikrein gene 10 is a biomarker for predicting poor prognosis in gastric cancer

AIM: To analyze the expression of kallikrein gene 10 (KLK10) in gastric cancer and to determine whether KLK10 has independent prognostic value in gastric cancer.

METHODS: We studied KLK10 expression in 80 histologically confirmed gastric cancer samples using real-time quantitative reverse transcription-PCR and hK10 expression using immunohistochemistry. Correlations with clinicopathological variables (lymph node metastasis, depth of invasion and histology) and with outcomes (disease-free survival and overall survival) during a median follow-up period of 31 mo were assessed. Gastric cancer tissues were then classified as KLK10 positive or negative.

RESULTS: KLK10 was found to be highly expressed in 57/80 (70%) of gastric cancer samples, while its expression was very low in normal gastric tissues. Positive relationships between KLK10 expression and lymph node metastasis (P = 0.048), depth of invasion (P = 0.034) and histology (P = 0.015) were observed. Univariate survival analysis revealed that gastric cancer patients with positive KLK10 expression had an increased risk for relapse/metastasis and death (P = 0.005 and 0.002, respectively). Cox multivariate analysis indicated that KLK10 was an independent prognostic indicator of disease-free survival and overall survival in patients with gastric cancer.

CONCLUSION: KLK10 expression is an independent biomarker of unfavorable prognosis in patients with gastric cancer.

Clinical significance of kallikrein-related peptidase (KLK10) mRNA expression in colorectal cancer

OBJECTIVES

Colorectal cancer (CRC) is one of the three most common cancers in both genders. Even though several biomarkers are in use in diagnosis and prognosis of the disease, they are marred by limited specificity and sensitivity. The human kallikrein-related peptidase 10 (KLK10) gene is a member of the human tissue kallikrein family. Because prostate specific antigen (PSA), the best biomarker for detecting and monitoring prostate cancer, is a member of this family, many other members, including KLK10, have been widely examined as novel biomarkers for different cancer types. In previous studies, KLK10 has been proposed as a diagnostic biomarker for ovarian carcinoma, while its methylation on exon 3 has been proposed as a prognostic marker for early-stage breast cancer patients. The purpose of this study was to analyse KLK10 mRNA expression and examine its prognostic value and potential clinical application as a novel molecular tissue biomarker in CRC.

DESIGN AND METHODS

The study group consisted of 190 colorectal samples. Total RNA was extracted from pulverised tissues and cDNA was prepared by reverse transcription. KLK10 was amplified by real-time PCR. B2M was used as a reference gene and HT-29 cells as positive control.

RESULTS

KLK10 expression was significantly higher in cancer tissues (P<0.001). Tumours of advanced TNM and Dukes' stage showed high KLK10 expression status (P=0.036; P=0.025). Patients with high KLK10 expression had a shorter disease-free and overall survival rates (P=0.014; P=0.020).

CONCLUSION

Our results suggest that KLK10 may serve as a new marker of unfavourable prognosis of colorectal cancer.

The relationship between tumor size and stage in early versus advanced ovarian cancer

BACKGROUND

Ovarian cancer has a different prognosis between early (I and II) and advanced stage (III and IV). The mechanism of disease progression is unknown, but patients with advanced disease may have a higher propensity for seeding of the abdominal cavity early in the disease process than those with early stage. Theoretically if this is so, then patients with advanced stage should have smaller sized tumors than patients with early stage.

METHODS

This was a retrospective chart review of patients in the tumor registry in 2003-2006. Patients had epithelial ovarian cancer, other cell types were excluded. Only cases with documentation of surgical and pathologic staging and measured dimensions on pathologic specimen were included. Patient stage and all available dimensions measured on diseased ovaries were recorded. The dimensions for each patient were averaged into a single dimension for that patient, and then these measurements were totaled and averaged.

RESULTS

There were 110 patients analyzed: 85 with advanced disease, 25 with early stage. The average measurement was 4.8 cm in advanced disease, and was 10.7 cm in early stage disease. This difference was statistically significant (p<0.001).

CONCLUSIONS

Overall, patients with early stage ovarian cancer have diseased ovaries that are more than twice as large as those found in advanced disease. This finding supports the fact that early versus advanced ovarian cancer are 2 separate disease processes. Early stage grows locally and does not disseminate, and advanced stage disseminates while the tumor is still relatively small. Theoretically there may be a factor that separates these 2 into different diseases, where advanced disease patients have a substance produced by their tumor that allows for early dissemination, and early stage lacks this substance and only grows locally. Basic science research comparing the tissue microarrays of early versus advanced stage disease may be able to identify this difference. If the difference is found, perhaps therapy can be targeted against this difference, and screening tests for advanced ovarian cancer can be improved.

Diagnostic value of serum kallikrein-related peptidases 6 and 10 versus CA125 in ovarian cancer

OBJECTIVES

To assess the diagnostic value of serum KLK6 and KLK10 in patients with ovarian tumor in comparison to serum CA125.

METHODS

Based on clinical and sonographic findings, 90 patients were consecutively recruited at the Gynecological Oncology Unit, Ain Shams University Maternity Hospital. Preoperative serum KLK6 and/or KLK10 were determined by enzyme-linked immunosorbent assay technique. The patients' final diagnoses were those of the histopathological reports.

RESULTS

There were 27 malignant versus 63 benign cases. Serum markers' diagnostic specificity and sensitivity were 80.3/72.7, 56.8/64.0, and 39.53/58.3 for CA125, KLK6, and KLK10, respectively. Combination of CA125 with either of the other 2 markers revealed diagnostic enhancement with KLK10 (85.37/73.00) but not with KLK6 (42.86/86.36).

CONCLUSIONS

In ovarian cancer, serum KLK6 and KLK10 may have much lower overall sensitivities than serum CA125. However, whereas serum KLK6 may improve the sensitivity of CA125, serum KLK10 may have the highest specificity among the 3 markers.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

The association with age, human tissue kallikreins 6 and 10 and hemostatic markers for survival outcome from epithelial ovarian cancer

PURPOSE

To assess known cancer biomarkers CA-125, human tissue kallikreins KLK6 and KLK10, hemostatic markers and age with 5-year survival outcome from epithelial ovarian cancer.

METHODS

Forty-one benign cyst cohorts and 83 patients diagnosed with ovarian cancer were recruited. The following assays were performed: fibrinogen, vWF antigen, D: -dimer, ATIII activity, tPA, PAI-1, uPAR, KLK6, KLK10 and CA-125. Follow-up visits of cancer patients of more than 60 months were noted. Data between those who survived past 60 months and mortality from cancer were analyzed.

RESULTS

Only 24 patients lived past 60 months, and 31 died (advanced stage n = 27). Those living past 60 months were significantly older and associated with similar pre-operative levels seen in benign cyst cohorts especially for KLK6, fibrinogen, vWF, AT levels despite upregulation of D: -dimer, CA-125 and KLK10. Ovarian cancer cohorts living past 60 months were younger than those who died within 12 months (n = 12). Mortality within 12 months was associated with older age, upregulation of KLK6, fibrinogen, D: -dimer, vWF, tPA antigen and reduced ATIII levels. Similarly, mortality within 36 months of disease showed older age with upregulation of CA-125, KLK6 D: -dimer vWF antigen and tPA antigen levels. Late stage cancer (III/IV) showed upregulated CA-125, KLK6, KLK10, D: -dimer and reduced AT compared to early stage cancer (I/II). The 5-year survival rate for early cancer was 80%, advanced 22.9% and overall 5-year survival rate was 43.6%.

CONCLUSION

Older age together with the novel biomarkers studied and their association with adverse outcome from epithelial ovarian cancer was seen especially within 12 and 36 months of disease. Those who lived past 60 months of disease showed similar pre-operative levels seen in benign cyst cohorts despite elevated D: -dimer, CA125 and KLK 10. An enlarged study is needed to confirm these findings.

Association of TMPRSS2 and KLK11 gene expression levels with clinical progression of human prostate cancer

AIM

The aim of this study was to analyze the clinicopathological characteristics of TMPRSS2 and KLK11 gene expression levels in human prostate cancer (PCa), and to evaluate their clinical significance in the progression of PCa.

METHODS

The expression of prostate-type and brain-type isoforms of KLK11 gene, and TMPRSS2 gene was analyzed by quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) in 63 PCa tissues. The correlation of TMPRSS2 and KLK11 gene expression with the clinicopathological characteristics and with the prognosis of PCa was subsequently assessed.

RESULTS

The mean values of TMPRSS2 (3.91 +/- 0.78 in PCa vs. 0.26 +/- 0.04 in normal prostate tissues) and both isoforms of KLK11 (prostate-type: 3.63 +/- 0.42 in PCa vs. 0.49 +/- 0.07 in normal prostate tissues; brain-type: 3.11 +/- 0.30 in PCa vs. 0.46 +/- 0.05 in normal prostate tissues) were significantly higher in cancer tissues compared with their normal counterparts. We found a significant positive correlation between TMPRSS2 expression and tumor stage (P = 0.02), Gleason score (P = 0.008), and tumor grade (P = 0.016). Regarding prostate-type KLK11, we identified a significant association between lower expression and higher tumor stage (P = 0.009), Gleason score (P = 0.01), and tumor grade (P = 0.006). No such association was seen with the brain-type isoform. The survival rate of the patients with TMPRSS2-high/KLK11-low expression was lowest (P = 0.003).

CONCLUSION

The results suggest that the up-regulation of TMPRSS2 gene and the down-regulation of KLK11 gene in advanced and more aggressive tumors may open the feasibility of being used as biomarkers distinguishing the tumor aggressiveness as well as novel prognostic indicators for PCa.

Over-expression of human kallikrein 11 is associated with poor prognosis in patients with low rectal carcinoma

AIM

The goal of this study was to analyze the expression of human kallikrein 11 (hK11) in low rectal carcinoma (LRC) tissues, as well as its association with the clinicopathologic features of LRC patients and its prognostic significance.

METHODS

Between January 1998 and January 2003, 126 patients with LRC were randomized to receive laparoscopic-assisted abdominoperineal resection (APR). Their hK11 expression levels were examined by immunostaining on paraffin-embedded tumor specimens. Then the association of hK11 expression with clinicopathologic characteristics and patients' prognosis was analyzed.

RESULTS

The positive degree of immunohistochemical staining in cancerous tissues (1.86 +/- 0.02) was higher than that in the control group (1.18 +/- 0.11, P = 0.008). Strong positive hK11 staining associated significantly with various clinicopathologic features, such as Dukes Staging (P < 0.001), histological differentiation grade (P = 0.003), CEA level (P = 0.01), lymph node metastasis (P < 0.001), and invasion depth (P = 0.002). Patients with weak hK11 positive expression showed better survival rates of 5-year follow-up than those with strong positive expression (80.85% for weak positive expression and 58.23% in strong positive expression, respectively; P < 0.01 for analyses). Using Cox regression analysis of the 126 patients, strong positive expression of hK11, Dukes Staging, lymph node metastasis, and invasion depth seemed to be independent prognostic indicators (P < 0.01, P = 0.02, P < 0.01 and P < 0.01, respectively).

CONCLUSION

hK11 may be another prognostic biomarker of LRC. Knowledge of hK11 expression in LRC tissues could contribute to the prediction of prognosis of LRC patients.

Phase II trial of single agent cetuximab in patients with persistent or recurrent epithelial ovarian or primary peritoneal carcinoma with the potential for dose escalation to rash

OBJECTIVES

Determine if cetuximab dose escalation to induce grade 2 rash correlates with anti-tumor activity and if sera-based markers could predict likelihood of response.

METHODS

Patients with persistent/recurrent ovarian or primary peritoneal carcinoma received an initial dose of cetuximab 400 mg/m(2), then 250 mg/m(2) weekly for two 3-week cycles. Patients who had stable disease (SD) and <grade 2 rash were dose escalated in 75 mg/m(2) increments every 3 weeks until grade 2 rash or to a maximum weekly dose of 400 mg/m(2). Pre- and post-treatment serum samples were evaluated for potential predictive markers of response.

RESULTS

One of 25 patients achieved partial remission (PR) and 9 patients had SD. The median progression free survival was 2.1 months; the 1-year survival rate was 54.8%. Rash (96%) was the most common drug-related adverse event. At first response assessment, 4 patients remained at 250 mg/m(2); 8 patients were dose-escalated to 325 mg/m(2); of these, 4 ultimately were increased to 400 mg/m(2). Patients with progressive disease (PD) were removed from the study. Ninety-two serologic markers were analyzed from 20 patients to identify markers associated with clinical activity and/or predictive of outcome. Pretreatment levels of twelve markers were significantly elevated in patients exhibiting PD versus SD or PR; however, changes in marker levels during the course of treatment were not significant indicators of response.

CONCLUSIONS

Single-agent cetuximab showed minimal activity in patients with recurrent ovarian cancer. Patients with elevated levels of 12 serologic markers at baseline were more likely to have earlier disease progression.

National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers

Background: Updated National Academy of Clinical Biochemistry (NACB) Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed.

Methods: Published reports relevant to use of tumor markers for 5 cancer sites—testicular, prostate, colorectal, breast, and ovarian—were critically reviewed.

Results: For testicular cancer, α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are recommended for diagnosis/case finding, staging, prognosis determination, recurrence detection, and therapy monitoring. α-Fetoprotein is also recommended for differential diagnosis of nonseminomatous and seminomatous germ cell tumors. Prostate-specific antigen (PSA) is not recommended for prostate cancer screening, but may be used for detecting disease recurrence and monitoring therapy. Free PSA measurement data are useful for distinguishing malignant from benign prostatic disease when total PSA is &lt;10 μg/L. In colorectal cancer, carcinoembryonic antigen is recommended (with some caveats) for prognosis determination, postoperative surveillance, and therapy monitoring in advanced disease. Fecal occult blood testing may be used for screening asymptomatic adults 50 years or older. For breast cancer, estrogen and progesterone receptors are mandatory for predicting response to hormone therapy, human epidermal growth factor receptor-2 measurement is mandatory for predicting response to trastuzumab, and urokinase plasminogen activator/plasminogen activator inhibitor 1 may be used for determining prognosis in lymph node–negative patients. CA15-3/BR27–29 or carcinoembryonic antigen may be used for therapy monitoring in advanced disease. CA125 is recommended (with transvaginal ultrasound) for early detection of ovarian cancer in women at high risk for this disease. CA125 is also recommended for differential diagnosis of suspicious pelvic masses in postmenopausal women, as well as for detection of recurrence, monitoring of therapy, and determination of prognosis in women with ovarian cancer.

Conclusions: Implementation of these recommendations should encourage optimal use of tumor markers.

Lectin-based electrophoretic analysis of the expression of the 35 kDa inter-alpha-trypsin inhibitor heavy chain H4 fragment in sera of patients with five different malignancies

A 35 kDa glycoprotein whose abundance was previously demonstrated to be enhanced in sera of patients with endometrial adenocarcinoma (n = 12), was isolated from pooled sera of three of the cancer patients using champedak galactose-binding lectin affinity chromatography in the present study. Subjecting it to 2-DE and MS/MS, the glycoprotein was identified as the O-glycosylated fragment of inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4). When compared to control sera (n = 17), expression of the 35 kDa ITIH4 cleavage fragment was demonstrated to be significantly enhanced in sera of patients with breast carcinoma (n = 10), epithelial ovarian carcinoma (n = 10), and germ cell ovarian carcinoma (n = 10) but not in patients with nasopharyngeal carcinoma (n = 13) and osteosarcoma (n = 7). The lectin-based electrophoretic bioanalytical method adopted in the present study may be used to assess the physiological relevance of ITIH4 fragmentation and its correlation with different malignancies, their stages and progression.

Early detection of ovarian cancer

Ovarian cancer is associated with an overall mortality of 75%, but can be cured in up to 90% of cases if diagnosed while still limited to the ovaries. Given the low prevalence of ovarian cancer in the general population, an effective screening strategy must not only have a high sensitivity for early-stage disease (>75%), but must also have a very high specificity (99.6%) to prompt no more than ten operations for each case of ovarian cancer diagnosed (positive predictive value [PPV] of 10%). Attempts to develop an effective screening strategy for ovarian cancer have utilized ultrasonography and serum tumor markers. Transvaginal sonography (TVS) and the serum marker CA125 have received the most attention to date. Used individually on a single occasion, neither of these approaches provides an adequate PPV and the cost of annual TVS is significant. Recent clinical trials have focused on serial monitoring of CA125 and the sequential use of a rising CA125 to prompt TVS in a limited number of women screened. Sequential monitoring of CA125 has significantly improved specificity of the assay in women over 50 years of age. The limited sensitivity of CA125 has, however, prompted a search for multiple serum markers that, in combination, would detect more than 90% of early-stage disease. Recent developments in genomic and proteomic research have identified a number of candidate biomarkers. Platforms have been developed that can assay more than 50 analytes in a few hundred microliters of serum. Panels of biomarkers have been discovered with high sensitivity and specificity for early-stage disease, but these require prospective validation. Several biomarkers have also been detected in urine, raising the possibility of a less expensive, more convenient screening test. Imaging techniques have been improved and mathematical methods developed that, in aggregate, promise to provide an effective screening strategy for ovarian cancer. In this review, we will assess the current status and describe future directions in ovarian cancer screening.

A multiparametric panel for ovarian cancer diagnosis, prognosis, and response to chemotherapy

PURPOSE

Our goal was to examine a panel of 11 biochemical variables, measured in cytosolic extracts of ovarian tissues (normal, benign, and malignant) by quantitative ELISAs for their ability to diagnose, prognose, and predict response to chemotherapy of ovarian cancer patients.

EXPERIMENTAL DESIGN

Eleven proteins were measured (9 kallikreins, B7-H4, and CA125) in cytosolic extracts of 259 ovarian tumor tissues, 50 tissues from benign conditions, 35 normal tissues, and 44 tissues from nonovarian tumors that metastasized to the ovary. Odds ratios and hazard ratios and their 95% confidence interval were calculated. Time-dependent receiver operating characteristic curves for censored survival data were used to evaluate the performance of the biomarkers. Resampling was used to validate the performance.

RESULTS

Most biomarkers effectively separated cancer from noncancer groups. A composite marker provided an area under the curve of 0.97 (95% confidence interval, 0.95-0.99) for discriminating normal and cancer groups. Univariately, hK5 and hK6 were positively associated with progression. After adjusting for clinical variables in multivariate analysis, both hK10 and hK11 significantly predicted time to progression. Increasing levels of hK13 were associated with chemotherapy response, and the predictive power of hK13 to chemotherapy response was improved by a panel of five biomarkers.

CONCLUSIONS

The evidence shows that a group of kallikreins and multiparametric combinations with other biomarkers and clinical variables can significantly assist with ovarian cancer classification, prognosis, and response to platinum-based chemotherapy. In particular, we developed a multiparametric strategy for predicting ovarian cancer response to chemotherapy, comprising several biomarkers and clinical features.

A proteome resource of ovarian cancer ascites: integrated proteomic and bioinformatic analyses to identify putative biomarkers

Epithelial ovarian cancer is the most lethal gynecological malignancy, and disease-specific biomarkers are urgently needed to improve diagnosis, prognosis, and to predict and monitor treatment efficiency. We present an in-depth proteomic analysis of selected biochemical fractions of human ovarian cancer ascites, resulting in the stringent and confident identification of over 2500 proteins. Rigorous filter schemes were applied to objectively minimize the number of false-positive identifications, and we only report proteins with substantial peptide evidence. Integrated computational analysis of the ascites proteome combined with several recently published proteomic data sets of human plasma, urine, 59 ovarian cancer related microarray data sets, and protein-protein interactions from the Interologous Interaction Database I (2)D ( http://ophid.utoronto.ca/i2d) resulted in a short-list of 80 putative biomarkers. The presented proteomics analysis provides a significant resource for ovarian cancer research, and a framework for biomarker discovery.

PSA and other tissue kallikreins for prostate cancer detection

Prostate cancer is the most common neoplasia of middle-aged men. Prostate specific antigen (PSA) is the first FDA-approved tumour marker for early detection of cancer and it is now in widespread clinical use. The discovery of different PSA molecular forms in serum (free PSA, PSA complexed with various protease inhibitors) in the early 1990s renewed clinical research to enhance the specificity of PSA. Also, the use of a homologous prostate-localised antigen, human glandular kallikrein 2 (KLK2) may further reduce the number of unnecessary prostate biopsies. More recently, promising data is emerging regarding molecular forms of free PSA (proPSA, BPSA, 'intact' PSA) and other members of the expanded human kallikrein family. These new findings may add substantial clinical information for early detection of prostate cancer.

Current management strategies for ovarian cancer

Epithelial ovarian cancer originates in the layer of cells that covers the surface of the ovaries. The disease spreads readily throughout the peritoneal cavity and to the lymphatics, often before causing symptoms. Of the cancers unique to women, ovarian cancer has the highest mortality rate. Most women are diagnosed as having advanced stage disease, and efforts to develop new screening approaches for ovarian cancer are a high priority. Optimal treatment of ovarian cancer begins with optimal cytoreductive surgery followed by combination chemotherapy. Ovarian cancer, even in advanced stages, is sensitive to a variety of chemotherapeutics. Although improved chemotherapy has increased 5-year survival rates, overall survival gains have been limited because of our inability to eradicate all disease. Technologic advances that allow us to examine the molecular machinery that drives ovarian cancer cells have helped to identify numerous therapeutic targets within these cells. In this review, we provide an overview of ovarian cancer with particular emphasis on recent advances in operative management and systemic therapies.

Human tissue kallikreins: the cancer biomarker family

Human tissue kallikreins (KLKs) are attracting increased attention due to their role as biomarkers for the screening, diagnosis, prognosis, and monitoring of various cancers including those of the prostate, ovarian, breast, testicular, and lung. Human tissue kallikrein genes represent the largest contiguous group of proteases within the human genome. Originally thought to consist of three genes, the identification of the human kallikrein locus has expanded this number to fifteen. These genes, and their encoded proteins, share a high degree of homology and are expressed in different tissues. Prostate-specific antigen (PSA), the most commonly known kallikrein, is a useful biomarker for prostate cancer. Several other kallikreins, including kallikreins 2 (KLK2) and 11 (KLK11) are emerging as complementary prostate cancer biomarkers. Along with these kallikreins, several others have been implicated in the other cancers. For example, KLK5, 6, 7, 10, 11, and 14 are emerging biomarkers for ovarian cancer. The identification of kallikrein substrates and the development of proteolytic cascade models implicate kallikrein proteins in cancer progression. This review describes the current status of kallikreins as cancer biomarkers.

Prevention and early detection of ovarian cancer: mission impossible?

Epithelial ovarian cancer is neither a common nor a rare disease. In the United States, the prevalence of ovarian cancer in postmenopausal women (1 in 2,500) significantly affects strategies for prevention and detection. If chemoprevention for ovarian cancer were provided to all women over the age of 50, side effects would have to be minimal in order to achieve an acceptable ratio of benefit to risk. This ratio might be improved by identifying subsets of individuals at increased risk or by bundling prevention of ovarian cancer with treatment for other more prevalent conditions. Approximately 10% of ovarian cancers are familial and relate to mutations of BRCA1, BRCA2, and mismatch repair genes. More subtle genetic factors are being sought in women with apparently sporadic disease. Use of oral contraceptive agents for as long as 5 years decreases the risk of ovarian cancer in later life by 50%. In one study, fenretinide (4-HPR) delayed development of ovarian cancer in women at increased risk of developing breast and ovarian cancer. Accrual to confirmatory studies has been prohibitively slow and prophylactic oophorectomy is recommended for women at increased genetic risk. Vaccines may have a role for prevention of several different cancers. Breast and ovarian cancers express mucins that could serve as targets for vaccines to prevent both cancers. Early detection of ovarian cancer requires a strategy with high sensitivity (> 75% for stage I disease) and very high specificity (> 99.6%) to achieve a positive predictive value of 10%. Transvaginal sonography (TVS) has achieved these values in some studies, but is limited by the cost of annual screening in a general population. Two-stage strategies that incorporate both serum markers and TVS promise to be more cost-effective. An algorithm has been developed that calculates risk of ovarian cancer based on serial CA125 values and refers patients at highest risks for TVS. Use of the algorithm is currently being evaluated in a trial with 200,000 women in the United Kingdom that will critically test the ability of a two-stage screening strategy to improve survival in ovarian cancer. Whatever the outcome, additional serum markers will be required to detect all patients in an initial phase of screening. More than 30 serum markers have been evaluated alone and in combination with CA125. Recent candidates include: HE4, mesothelin, M-CSF, osteopontin, kallikrein(s) and soluble EGF receptor. Proteomic approaches have been used to define a distinctive pattern of peaks on mass spectroscopy or to identify a limited number of critical markers that can be assayed by more conventional methods. Several groups are placing known markers on multiplex platforms to permit simultaneous assay of multiple markers with very small volumes of serum. Mathematical techniques are being developed to analyze combinations of marker levels to improve sensitivity and specificity. In the future, serum markers should improve the sensitivity of detecting recurrent disease as well as facilitate earlier detection of ovarian cancer.

Disease processes may be reflected by correlations among tissue kallikrein proteases but not with proteolytic factors uPA and PAI-1 in primary ovarian carcinoma

In epithelial ovarian cancer, the high mortality rate is usually ascribed to late diagnosis, since these tumors commonly lack early-warning symptoms, but tumor-associated biomarkers useful for prognosis or therapy response prediction are in short supply. However, members of the tissue kallikrein serine protease family, the serine protease uPA and its inhibitor PAI-1, are associated with tumor progression of ovarian cancer. Therefore, we used ELISA to determine uPA, PAI-1, and tissue kallikreins hK5-8, 10, 11, and 13 in extracts of 142 primary tumor tissue specimens from ovarian cancer patients and studied the strength of association between protein expression levels of these tumor tissue-associated factors. uPA, PAI-1, hk5, and hk8 were related to FIGO stage; hK5 expression was higher in FIGO III/IV than in FIGO I/II patient tissues. PAI-1 and hk5 differed significantly according to nuclear grading; expression of hK5 was higher in G3 than in G1/2 tumors. Associations between uPA, PAI-1, and the tissue kallikreins were weak. There were strong pairwise correlations within the cluster of tissue kallikreins hK5, 6, 7, 8, 10, and 11, but their bivariate distributions depended on nuclear grading. These results support the notion that several tissue kallikreins are co-expressed in ovarian cancer patients, substantiating the existence of a steroid hormone-driven tissue kallikrein cascade in this disease.

Human kallikrein 10, a predictive marker for breast cancer

Our laboratory is involved in identifying genes that can be used as early diagnostic or prognostic markers in breast cancer. We previously identified a gene (NES1) that is expressed in normal but not in transformed mammary epithelial cells (MECs). NES1 is located on chromosome 19q13.4 within the kallikrein locus and thus was designated as human kallikrein 10 (hK10), although we have been unable to detect any protease activity. Importantly, hK10 expression is decreased in a majority of breast cancer cell lines. Transfection of hK10 into hK10-negative breast cancer cells reduces the tumorigenicity. Using methylation-specific PCR and subsequent sequencing, we demonstrate a strong correlation between hypermethylation of hK10 and loss of mRNA expression. Further analysis showed that essentially 100% of normal breast specimens had hK10 expression, whereas 46% of ductal carcinoma in situ (DCIS) and the majority of infiltrating ductal carcinoma (IDC) samples lacked the hK10 mRNA. Importantly, hK10-negative DCIS diagnosed at the time of biopsy were subsequently diagnosed as IDC at the time of definitive surgery. It has been shown that hK10 protein expression is regulated by steroids. In addition to breast cancers, hK10 is downregulated in cervical cancer, prostate cancer and acute lymphocytic leukemia, whereas it is upregulated in ovarian cancers. These results point to the paradoxical role of hK10 in human cancers and underscore the importance of further studies of this kallikrein.

1.70 A X-ray structure of human apo kallikrein 1: structural changes upon peptide inhibitor/substrate binding

Human kallikreins are serine proteases that comprise a recently identified large and closely related 15-member family. The kallikreins include both regulatory- and degradative-type proteases, impacting a variety of physiological processes including regulation of blood pressure, neuronal health, and the inflammatory response. While the function of the majority of the kallikreins remains to be elucidated, two members are useful biomarkers for prostate cancer and several others are potentially useful biomarkers for breast cancer, Alzheimer's, and Parkinson's disease. Human tissue kallikrein (human K1) is the best functionally characterized member of this family, and is known to play an important role in blood pressure regulation. As part of this function, human K1 exhibits unique dual-substrate specificity in hydrolyzing low molecular weight kininogen between both Arg-Ser and Met-Lys sequences. We report the X-ray crystal structure of mature, active recombinant human apo K1 at 1.70 A resolution. The active site exhibits structural features intermediate between that of apo and pro forms of known kallikrein structures. The S2 to S2' pockets demonstrate a variety of conformational changes in comparison to the porcine homolog of K1 in complex with peptide inhibitors, including the displacement of an extensive solvent network. These results indicate that the binding of a peptide substrate contributes to a structural rearrangement of the active-site Ser 195 resulting in a catalytically competent juxtaposition with the active-site His 57. The solvent networks within the S1 and S1' pockets suggest how the Arg-Ser and Met-Lys dual substrate specificity of human K1 is accommodated.

Proteomic tracking of serum protein isoforms as screening biomarkers of ovarian cancer

Epithelial ovarian cancer is the fourth leading cause of cancer death among women. Due to the asymptomatic nature and poor survival characteristic of the disease, screening for specific biomarkers for ovarian cancer is a major health priority. Differentially expressed proteins in the serum of ovarian cancer patients have the potential to be used as cancer-specific biomarkers. In this study, proteomic methods were used to screen 24 serum samples from women with high-grade ovarian cancer and compared to a control group of 11 healthy women. Affigel-Blue treated serum samples were processed either by linear (pH 4-7) or narrow range (pH 5.5-6.7) IEF strips for the first dimension. Proteins separated in first dimension were resolved by 8-16% gradient SDS-PAGE. Protein spots were visualized by SYPRO Ruby staining, imaged by FX-imager and compared and analyzed by PDQuest software. Twenty-two protein spots were consistently differentially expressed between normal and ovarian cancer patients by resolving proteins in a linear pH strip of 4-7 for the first dimension. Six of the protein spots, significantly up-regulated in grade 3 ovarian cancer patients (p < 0.05), were identified by MALDI-TOF MS and Western blotting as the isoforms of haptoglobin precursor. When serum proteins were resolved on narrow pH range strips (5.5-6.7), 23 spots were consistently differentially expressed between normal and grade 3 ovarian cancer patients. Of these, 4 protein spots significantly down regulated in grade 3 ovarian cancer patients (p < 0.05) were identified by MALDI-TOF MS and Western blotting, as isoforms of transferrin precursor. Increased expression of serum haptoglobin and transferrin was also identified in peritoneal tumor fluid obtained from women diagnosed with grade 2/3 ovarian cancer (n = 7). Changes in the expression of haptoglobin and transferrin in the serum of women with different pathological grades of ovarian cancer was examined by one-dimensional Western blotting method. Serum samples collected from women suffering from benign, borderline, grade 1, grade 2 and grade 3 cancer (n = 4 for haptoglobin and n = 5 for transferrin in each group) were analyzed and compared to the serum of normal healthy women. The mean serum haptoglobin expression in grade 3 ovarian cancer patients was fourfold higher than in the control subjects (p < 0.05). On the other hand, transferrin expression in grade 3 ovarian cancer patients was decreased by twofold than in normal healthy women (p < 0.05). Haptoglobin expression in the serum of cancer patients (n = 7) decreased following chemotherapy (six cycles of taxol/carboplatin). Concomitant with the decrease of haptoglobin, transferrin expression remained constant in four patients, but increased in three out of seven patients included in the study. Changes in serum expression of haptoglobin correlated with the change of CA 125 levels before and after chemotherapy. In conclusion, proteomic profiling of differentially expressed proteins in the sera of normal women compared to women with ovarian cancer can greatly facilitate the discovery of a panel of biomarkers that may aid in the detection of ovarian cancer with greater specificity.

New tumor markers: CA125 and beyond

A variety of biomarkers have been developed to monitor growth of ovarian cancer and to detect disease at an early interval. CA125 (MUC16) has provided a useful serum tumor marker for monitoring response to chemotherapy, detecting disease recurrence, distinguishing malignant from benign pelvic masses, and potentially improving clinical trial design. A rapid fall in CA125 during chemotherapy predicts a favorable prognosis and could be used to redistribute patients on multiarmed randomized clinical trials. Several studies now document that CA125 can serve as a surrogate marker for response in phase II trials. Serial measurement of CA125 might also provide a useful marker for monitoring stabilization of disease with cytostatic targeted therapeutic agents. The greatest potential for serum markers may be in detecting ovarian cancer at an early stage. A rising CA125 can be used to trigger transvaginal sonography (TVS) in a small fraction of patients. An algorithm has been developed that calculates risk of ovarian cancer based on serial CA125 values and refers patients at highest risk for TVS. Use of the algorithm is currently being evaluated in a trial with 200,000 women in the UK that will test critically the ability of a two-stage screening strategy to improve survival in ovarian cancer. Whatever the outcome, as 20% of ovarian cancers have little or no expression of CA125, additional serum markers will be required to detect all patients in an initial phase of screening. More than 30 serum markers have been evaluated alone and in combination with CA125 by different investigators. Some of the most promising include: HE4, mesothelin, M-CSF, osteopontin, kallikrein(s), and soluble EGF receptor. Two proteomic approaches have been used: one examines the pattern of peaks on mass spectroscopy and the other uses proteomic analysis to identify a limited number of critical markers that can be assayed by more conventional methods. Both approaches are promising and require further development. Several groups are placing markers on multiplex platforms to permit simultaneous assay of multiple markers with very small volumes of serum. Mathematical techniques are being developed to analyze combinations of marker levels to improve sensitivity and specificity. In the future, serum markers should improve the sensitivity of detecting recurrent disease as well as facilitate earlier detection of ovarian cancer.

Expression of the human kallikrein genes 10 (KLK10) and 11 (KLK11) in cancerous and non-cancerous lung tissues

Only one transcript for KLK10 was identified by RT-PCR in lung tissue, whereas KLK11 expressed at least four alternative transcripts. Quantitative analysis of KLK10 and KLK11 expression levels was assessed by real-time PCR, in a cohort of 47 patients with non-small-cell lung cancer (NSCLC). Expression levels of these genes were widely distributed in the population studied. Multivariate analysis revealed a correlation between KLK10 over-expression and the squamous cell carcinoma histotype (p=0.034). There was no correlation between gene expression and patient survival. Overall, both genes behaved similarly (p<0.001). These results suggest a co-regulation of KLK10 and KLK11 expression in lung and a lack of KLK10 suppressor role in NSCLC. Finally, our findings indicate that these genes are likely involved in normal physiology processes in bronchus.

The kallikrein world: an update on the human tissue kallikreins

Human tissue kallikreins (hKs) are attracting increased attention owing to their association with various forms of cancer and other diseases. Human tissue kallikrein genes represent the largest contiguous group of proteases within the human genome. There are many areas of kallikrein research that need to be further explored, including their tissue expression patterns, their regulation, identification of specific substrates, their participation in proteolytic cascades, and their clinical applicability as cancer biomarkers and therapeutic targets. In this review, we briefly describe the current status of kallikrein research and identify future avenues that will enhance our understanding of their function and involvement in human diseases.

Identification of new splice variants and differential expression of the human kallikrein 10 gene, a candidate cancer biomarker

The human kallikrein gene 10 (KLK10) is a member of the kallikrein gene family on chromosome 19q13.4. This gene was identified by its downregulation in breast cancer, and preliminary evidence suggests that it may act as a tumor suppressor. A computer-based analysis was performed on EST and SAGE clones from the Cancer Genome Anatomy Project and other databases. Experimental verification of differential expression of KLK10 in cancer was performed by PCR using gene-specific primers. The mRNA and EST analysis allowed the construction of the longest transcript of the gene and characterization of a 5' extension of the reported mRNA. In addition, seven new splice variants of KLK10 were identified. One of these variants, named KLK10 splice variant 3 (KLK10-SV3) which starts with a novel first exon, was experimentally verified. This variant is predicted to encode for the same protein as the 'classical' KLK10 mRNA, since the first exon is untranslated. One variant mRNA partially matches with the sequence of KLK10, while the rest of the mRNA matches with a portion of the polycystic kidney disease gene, found on chromosome 15. This variant could not be experimentally verified in either normal or cancerous tissues. There are 39 reported single nucleotide polymorphisms (SNPs) for the gene, in which three result in amino acid substitutions. SAGE analysis shows a clear upregulation of KLK10 in ovarian, pancreatic, colon, and gastric cancers. The gene is, however, downregulated in breast and prostate cancers. A three-fold decrease in expression levels was noted in actinic keratosis, compared to normal skin from the same patient. The differential regulation of KLK10 in ovarian and prostate cancers was experimentally verified by RT-PCR analysis. In addition, a significant number of clones were isolated from carcinomas of the head and neck. Fewer clones were found in carcinomas of the skin, brain and prostate. Orthologues were identified in three other species, with the highest degree of homology observed with the mouse and rat orthologues (42% in each). In conclusion new splice variants of the KLK10 gene were identified. These in silico analyses show a differential expression of the gene in various malignancies and provide the basis for directing experimental efforts to investigate the possible role of the gene as a cancer biomarker.

Human kallikrein 6: a new potential serum biomarker for uterine serous papillary cancer

PURPOSE

The discovery of novel biomarkers might greatly contribute to improve clinical management and outcomes in uterine serous papillary carcinoma (USPC), a highly aggressive variant of endometrial cancer.

EXPERIMENTAL DESIGN

Human kallikrein 6 (hK6) gene expression levels were evaluated in 29 snap-frozen endometrial biopsies, including 13 USPC, 13 endometrioid carcinomas, and 3 normal endometrial cells by real-time PCR. Secretion of hK6 protein by 14 tumor cultures, including 3 USPC, 3 endometrioid carcinoma, 5 ovarian serous papillary carcinoma, and 3 cervical cancers, was measured using a sensitive ELISA. Finally, hK6 concentration in 79 serum and plasma samples from 22 healthy women, 20 women with benign diseases, 20 women with endometrioid carcinoma, and 17 USPC patients was studied.

RESULTS

hK6 gene expression levels were significantly higher in USPC when compared with endometrioid carcinoma (mean copy number by real-time PCR, 1,927 versus 239, USPC versus endometrioid carcinoma; P < 0.01). In vitro hK6 secretion was detected in all primary USPC cell lines tested (mean, 11.5 microg/L) and the secretion levels were similar to those found in primary ovarian serous papillary carcinoma cultures (mean, 9.6 microg/L). In contrast, no hK6 secretion was detectable in primary endometrioid carcinoma and cervical cancer cultures. hK6 serum and plasma concentrations (mean +/- SE) among normal healthy females (2.7 +/- 0.2 microg/L), patients with benign diseases (2.4 +/- 0.2 microg/L), and patients with endometrioid carcinoma (2.6 +/- 0.2 microg/L) were not significantly different. In contrast, serum and plasma hK6 values in USPC patients (6.1 +/- 1.1) were significantly higher than those in the noncancer group (P = 0.006), benign group (P = 0.003), and endometrioid carcinoma patients (P = 0.005).

CONCLUSIONS

hK6 is highly expressed in USPC and is released in the plasma and serum of USPC patients. hK6 may represent a novel biomarker for USPC for monitoring early disease recurrence and response to therapy.

Human tissue kallikrein gene family: applications in cancer

Human tissue kallikrein genes, located on the long arm of chromosome 19, are a subgroup of the serine protease family of proteolytic enzymes. Initially thought to consist of three members, the human kallikrein locus has now been extended and includes 15 tandemly located genes. These genes, and their protein products, share a high degree of homology and are expressed in a wide array of tissues, mainly those that are under steroid hormone control. PSA (hK3) is one of the human kallikreins, and is the most useful tumor marker for prostate cancer screening, diagnosis, prognosis and monitoring. hK2, another prostate-specific kallikrein, has also been proposed as a complementary prostate cancer biomarker. In the past 5 years, the newly discovered kallikreins (KLK4-KLK15) have been associated with several types of cancer. For example, hK4, hK5, hK6, hK7, hK8, hK10, hK11, hK13 and hK14 are emerging biomarkers for ovarian, breast, prostate and testicular cancer. New evidence raises the possibility that some kallikreins are directly involved with cancer progression. We here review the evidence linking kallikreins and cancer and their applicability as novel biomarkers for cancer diagnosis and management.

Elevated fibroblast growth factor 23 in women with malignant ovarian tumors

OBJECTIVE

To determine whether fibroblast growth factor 23 (FGF23) concentrations are altered in women with ovarian cancers in which FGF physiology is known to be abnormal.

PATIENTS AND METHODS

Between May 2002 and September 2003 at the Mayo Clinic in Rochester, Minn, plasma or serum FGF23 concentrations were measured in 39 healthy women and in 14 with benign ovarian tumors, 14 with early-stage ovarian cancer, and 13 with advanced-stage ovarian cancer. Immunohistochemistry using anti-human FGF23 antibodies was performed on tissue from benign masses and advanced-stage tumors.

RESULTS

Serum or plasma FGF23 concentrations were significantly higher in women with advanced-stage ovarian cancer compared with concentrations in women with early-stage ovarian cancer or benign disease or in healthy women. A significant positive correlation was seen between serum iFGF23 and cFGF23 concentrations and stage of disease. Serum iFGF23 and cFGF23 concentrations were positively correlated with serum phosphorus among women with ovarian cancer. No patients with elevated iFGF23 or cFGF23 concentrations had hypophosphatemia. Immunohistochemistry detected FGF23 tissue staining in malignant ovarian cancer cells.

CONCLUSION

Serum or plasma FGF23 concentrations are elevated in patients with advanced-stage epithellal ovarian cancer without reductions in serum phosphate concentrations. The presence of elevated FGF23 concentrations in patients with an ovarian mass should suggest advanced-stage disease.

Human kallikrein 6 degrades extracellular matrix proteins and may enhance the metastatic potential of tumour cells

Human kallikrein 6 (hK6), a trypsin-like serine protease, is a newly identified member of the kallikrein gene family. Its involvement in inflammatory CNS lesions and in demyelination has been reported. Recent work has suggested that expression of this enzyme is significantly elevated in patients with ovarian cancer. We have identified many tumour cell lines that secrete hK6, but its physiological role is unknown. Here, we try to unveil the role of this kallikrein in the metastasis and invasion of tumour cells. We demonstrate that purified human recombinant hK6 can cleave gelatin in zymography and can efficiently degrade high-molecular-weight extracellular matrix proteins such as fibronectin, laminin, vitronectin and collagen. In Boyden chamber assays, we found that tumour cells treated with a neutralizing hK6 antibody migrate less than control cells. We conclude that hK6 might play a role in the invasion and metastasis of tumour cells and may be a candidate therapeutic target.

Human kallikrein 11: an indicator of favorable prognosis in ovarian cancer patients

OBJECTIVES

Human kallikrein 11 (hK11) is a secreted serine protease, highly expressed in hormonally regulated tissues, including the prostate and the ovary. Our preliminary studies indicate that hK11 may represent a diagnostic and prognostic biomarker for ovarian cancer. The aim of the present study was to examine the prognostic value of hK11 expression in ovarian tumors.

METHODS

Using our established immunofluorometric assay, hK11 levels were quantified (ng per mg of total protein) in 134 ovarian tumor extracts and correlated with various clinicopathological variables and outcome [progression-free survival (PFS), overall survival (OS)], over a median follow-up period of 42 months.

RESULTS

hK11 concentration in ovarian tumor cytosols ranged from 0 to 155 ng/mg of total protein, with a median of 1.45 ng/mg. An optimal cutoff value of 6.3 ng/mg was selected to categorize tumors as hK11-positive or negative. hK11-positive tumors were most often of early stage (Stage I/II) and grade (G1/G2) (P < 0.05). Univariate analysis revealed that patients with hK11-positive tumors had a significantly longer PFS (HR of 0.39, P = 0.005) and OS (HR of 0.44, P = 0.033). Cox multivariate analysis indicated that hK11 was an independent prognostic indicator of PFS (HR of 0.47, P = 0.042). Kaplan-Meier survival curves further confirmed that women with hK11-positive tumors have longer PFS and OS (P = 0.003 and P = 0.028, respectively). Also, a weak positive correlation was found between the expression levels of tissue hK11 and tissue CA125 (rs = 0.508; P < 0.001).

CONCLUSIONS

These results further validate our initial findings that hK11 is an independent marker of favorable prognosis in ovarian cancer patients.

Human kallikrein gene 11 (KLK11) mRNA overexpression is associated with poor prognosis in patients with epithelial ovarian cancer

PURPOSE

The purpose of this study was to examine expression levels of the human tissue kallikrein 11 gene (KLK11) in epithelial ovarian tumors and to identify the relationship between KLK11 expression and patient survival.

EXPERIMENTAL DESIGN

KLK11 mRNA expression was examined by semiquantitative PCR in 64 epithelial ovarian tumors (7 adenomas, 6 low malignant potential tumors, and 51 adenocarcinomas) and in 10 normal ovaries. Semiquantitative PCR results were correlated with clinicopathologic variables and overall survival. cDNA from human normal tissues and tumor tissues was also analyzed.

RESULTS

KLK11 mRNA expression was detected in various human cancer tissues including breast, lung, colon, prostate, pancreas, and ovarian carcinoma. The mean value of relative KLK11 expression ratio was significantly higher in ovarian tumor samples than in normal ovary samples (compared with normal samples: adenoma, P = 0.0006; low malignant potential tumor, P = 0.0049; and carcinoma, P < 0.0001). No statistically significant associations between KLK11 mRNA expression level and clinical stage, histological type, or histological grade were observed. The log-rank test showed that high KLK11 mRNA expression and advanced clinical stage significantly correlated with poor patient survival (P = 0.0185 and P = 0.0043, respectively). High KLK11 mRNA expression and clinical stage remained significantly associated with overall survival (P = 0.0225 and P = 0.0202, respectively) after multivariate analysis.

CONCLUSIONS

KLK11 expression may play an important role in ovarian cancer development and act as an independent prognostic marker in ovarian cancer patients.

Human kallikrein 13 involvement in extracellular matrix degradation

The human kallikrein family is a group of 15 serine protease genes clustered on chromosome 19q13.4 and shares a high degree of homology. These proteolytic enzymes have diverse physiological functions in many different tissues. Growing evidence suggests that many kallikreins are differentially expressed in cancer and may play a role in metastasis. Human kallikrein gene 13 (KLK13) is a member of this family and codes for a trypsin-like, secreted serine protease (hK13) that is overexpressed in ovarian cancer patients. The aim of this study was to determine if hK13 can degrade extracellular matrix components. Recombinant hK13 was produced in yeast and purified using cation exchange and reverse-phase chromatography. The protein was used as an immunogen to generate mouse monoclonal antibodies. Enzymatic activity of hK13 was verified by using synthetic tri-peptide fluorogenic substrates and gelatin zymography. Active hK13 was incubated with biotinylated extracellular matrix (ECM) proteins and degradation was evaluated by Western blot analysis. hK13-secreting cancer cell lines were treated in a chemotaxis invasion chamber that was coated with various ECM proteins, to determine if hK13 plays a role in tumor cell migration and invasion. Assay with the synthetic substrates and zymography have shown that recombinant hK13 was enzymatically active. The Western blot results showed that hK13 was able to cleave the major components of the extracellular matrix. In the chemotaxis invasion chamber experiment, it was found that ovarian cancer cell lines that secreted hK13 and were treated with an hK13 neutralizing antibody migrated less than untreated cells. Human kallikrein13 may play a role in tissue remodeling and/or tumor invasion and metastasis. Targeting hK13 activity with neutralizing antibodies may have therapeutic applications.

The emerging roles of human tissue kallikreins in cancer

Human tissue kallikreins (hKs), which are encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Although primarily known for their clinical applicability as cancer biomarkers, recent evidence implicates hKs in many cancer-related processes, including cell-growth regulation, angiogenesis, invasion and metastasis. They have been shown to promote or inhibit neoplastic progression, acting individually and/or in cascades with other hKs and proteases, and might represent attractive targets for therapeutic intervention.

Proteomic-based identification of haptoglobin-1 precursor as a novel circulating biomarker of ovarian cancer

Screening for specific biomarkers of early-stage detection of ovarian cancer is a major health priority due to the asymptomatic nature and poor survival characteristic of the disease. We utilised two-dimensional gel electrophoresis (2DE) to identify differentially expressed proteins in the serum of ovarian cancer patients that may be useful as biomarkers of this disease. In this study, 38 ovarian cancer patients at different pathological grades (grade 1 (n=6), grade 2 (n=8) and grade 3 (n=24)) were compared to a control group of eight healthy women. Serum samples were treated with a mixture of Affigel-Blue and protein A (5 : 1) for 1 h to remove high abundance protein (e.g. immunoglobulin and albumin) and were displayed using 11 cm, pH 4–7 isoelectric focusing strips for the first dimension and 10% acrylamide gel electrophoresis for the second dimension. Protein spots were visualised by SYPRO-Ruby staining, imaged by FX-imager and compared and analysed by PDQuest software. A total of 24 serum proteins were differentially expressed in grade 1 (P<0.05), 31 in grade 2 (P<0.05) and 25 in grade 3 (P<0.05) ovarian cancer patients. Six of the protein spots that were significantly upregulated in all groups of ovarian cancer patients were identified by nano-electrospray quadrupole quadrupole time-of-flight mass spectrometry (n-ESIQ(q)TOFMS) and matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOFMS) as isoforms of haptoglobin-1 precursor (HAP1), a liver glycoprotein present in human serum. Further identification of the spots at different pathological grades was confirmed by Western blotting using monoclonal antibody against a haptoglobin epitope contained within HAP1. Immunohistochemical localisation of HAP1-like activity was present in malignant ovarian epithelium and stroma but strong immunostaining was present in blood vessels, areas with myxomatous stroma and vascular spaces. No tissue localisation of HAP1-like immunoreactivity was observed in normal ovarian surface epithelium. These data highlight the need to assess circulating concentration of HAP1 in the serum of ovarian cancer patients and evaluate its potential as a biomarker in the early diagnosis of ovarian cancer.

Human Tissue Kallikreins: Physiologic Roles and Applications in Cancer

Tissue kallikreins are members of the S1 family (clan SA) of trypsin-like serine proteases and are present in at least six mammalian orders. In humans, tissue kallikreins (hK) are encoded by 15 structurally similar, steroid hormone–regulated genes (KLK) that colocalize to chromosome 19q13.4, representing the largest cluster of contiguous protease genes in the entire genome. hKs are widely expressed in diverse tissues and implicated in a range of normal physiologic functions from the regulation of blood pressure and electrolyte balance to tissue remodeling, prohormone processing, neural plasticity, and skin desquamation. Several lines of evidence suggest that hKs may be involved in cascade reactions and that cross-talk may exist with proteases of other catalytic classes. The proteolytic activity of hKs is regulated in several ways including zymogen activation, endogenous inhibitors, such as serpins, and via internal (auto)cleavage leading to inactivation. Dysregulated hK expression is associated with multiple diseases, primarily cancer. As a consequence, many kallikreins, in addition to hK3/PSA, have been identified as promising diagnostic and/or prognostic biomarkers for several cancer types, including ovarian, breast, and prostate. Recent data also suggest that hKs may be causally involved in carcinogenesis, particularly in tumor metastasis and invasion, and, thus, may represent attractive drug targets to consider for therapeutic intervention.

Immunohistochemical localization of human kallikreins 6, 10 and 13 in benign and malignant prostatic tissues

Human kallikreins 6, 10 and 13 (hK6, hK10 and hK13) are expressed by many normal, mainly glandular tissues, including prostatic epithelium. Some kallikreins may function as tumor suppressors or are downregulated during cancer progression. The aim of this study was to evaluate the immunoexpression of these kallikreins in benign and malignant prostatic tissues and correlate their expression with prostate cancer (PC) prognosis. Included in the study were 25 cases of nonmalignant prostate and 179 cases of PC. Among them, 122 PC cases were immunostained for hK6, 94 for hK10 and 113 for hK13, respectively. The follow-up period for a subset of 68 patients who had undergone radical prostatectomy (RP) was 1-58 months (mean=13.4 +/- 1.7 and median=8.0 months). A cutoff value of 0.2 microg/l of serum PSA was established as a biochemical recurrence threshold. Follow-up information was available for 26/55 RP cases stained for hK6, 14/32 cases stained for hK10 and 25/59 cases stained for hK13. Gleason score (GS) 7 carcinomas were stratified as 7a and 7b, according to the primary grade. PC with GS 2-7a were histologically categorized as low malignant (LM) and PC with GS 7b-10 as high malignant (HM). The immunohistochemical method of streptavidin-biotin-peroxidase using monoclonal and polyclonal antibodies was performed. In the benign prostate and in prostatic intraepithelial neoplasia, a cytoplasmic immunostaining of varying intensity was evident. In PC, the immunoexpression of all kallikreins was decreased: 102/122 cases (84%) were positive for hK6, 73/94 (78%) for hK10 and 97/113 (86%) for hK13, respectively. A statistically significant difference in expression was found, in comparison to nonmalignant prostates (P=0.029, 0.009 and 0.045, respectively). Also, a positive correlation was observed between the immunoexpression of these three kallikreins. Concerning the histological grade, HM-PC expressed all three kallikreins with a slightly higher percentage than LM-PC: 79 vs 88% for hK6, 76 vs 79% for hK10 and 76 vs 92% for hK13. These differences were statistically significant only in the case of hK13 (P=0.024). Serum PSA did not correlate with kallikrein immunoexpression in PC. Furthermore, there was no significant correlation between kallikrein expression and pathological stage or recurrence, in the cases of RP. All three kallikreins are expressed in the nonmalignant and malignant prostate, with cancer tissues demonstrating slightly lower expression. Expression levels did not correlate with aggressiveness and they do not seem to have value for prostate cancer prognosis.

Development of an Immunofluorometric Assay and Quantification of Human Kallikrein 7 in Tissue Extracts and Biological Fluids

Background: Human kallikrein 7 (hK7), also known as human stratum corneum chymotryptic enzyme, is a chymotrypsin-like serine protease first identified in human skin extracts and predicted to be a secreted protease. The aim of this study was to develop a sensitive and specific immunoassay for hK7 and to examine the distribution of hK7 in tissue extracts and biological fluids.

Methods: Recombinant hK7 was produced in human embryonic kidney cells (HEK293T) and purified by a three-step column chromatographic procedure. The purified hK7 was injected into mice for antibody generation. A sandwich-type immunoassay was developed with the anti-hK7 monoclonal antibodies.

Results: The assay had imprecision (CV) &lt;10% through the dynamic range of 0.2–20 μg/L and had no detectable cross-reactivity from other members in the human kallikrein gene family. Highest concentrations were found in skin, esophagus, and kidney. hK7 was also found in amniotic fluid, ascites from ovarian cancer patients, breast milk, cerebrospinal fluid, saliva, seminal plasma, serum, sweat, synovial fluid, and urine.

Conclusions: This study describes the first ELISA-type immunoassay for hK7 protein quantification. hK7 is found many human tissues and in various biological fluids.

Human kallikrein 13 protein in ovarian cancer cytosols: a new favorable prognostic marker

PURPOSE

Human kallikrein 13 (hK13; encoded by the KLK13 gene) is a secreted serine protease expressed in endocrine tissues, including the prostate, testis, breast, and ovary. We have previously reported steroid hormone regulation of the KLK13 gene and its clinical value as a marker of favorable prognosis in breast cancer at the mRNA level. We hypothesized that hK13 may represent a potential biomarker for ovarian carcinomas.

PATIENTS AND METHODS

Using a newly developed enzyme-linked immunosorbent assay (ELISA), hK13 levels were quantified in 131 ovarian tumor extracts and correlated with various clinicopathological variables and outcome (progression-free survival [PFS], overall survival [OS]), over a median follow-up period of 42 months.

RESULTS

hK13 concentration in ovarian tumor cytosols ranged from 0 to 18.4 ng/mg of total protein. An optimal cutoff value of 0.13 ng/mg (67(th) percentile) was selected, based on the ability of hK13 values to predict the PFS of the study population, to categorize tumors as hK13-positive or negative. Women with hK13-positive tumors most often had early stage (stage I/II) disease, no residual tumor after surgery and optimal debulking success (P <.05). Univariate and multivariate Cox regression analyses revealed that patients with hK13-positive tumors had a significantly longer PFS and OS than hK13-negative patients (P <.05). Kaplan-Meier survival curves further confirmed a reduced risk of relapse and death in women with hK13-positive tumors (P =.007 and P =.002, respectively).

CONCLUSION

These results indicate that hK13 is an independent marker of favorable prognosis in ovarian cancer.

Kallikrein gene downregulation in breast cancer

Recent evidence suggests that many members of the human kallikrein gene family are differentially regulated in breast cancer and other endocrine-related malignancies. In this study, we utilised the serial analysis of gene expression (SAGE) and expressed sequence tag (EST) databases of the Cancer Genome Anatomy Project (CGAP) to perform in silico analyses of the expression pattern of the 15 human kallikrein genes in normal and cancerous breast tissues and cell lines using different analytical tools such as Virtual Northern blotting, Digital Differential Display and X-profiler. Our results indicate that at least four kallikrein genes (KLK5, 6, 8, 10) are downregulated in breast cancer. Probing eight normal and 24 breast cancer SAGE libraries with gene-specific tags for each of the above kallikreins indicated moderate-to-high expression densities in normal breast (27–319 tags per million; tpm, in two to five out of eight libraries), compared to no or low expression (0 – 34 tpm in zero to two libraries out of 24) in breast cancer. These data were verified by screening the EST databases, where all mRNA clones isolated for these genes, except for one in each, were from normal breast libraries, with no clones detected from breast cancer tissues or cell lines (with the exception of KLK8). X-profiler comparison of two pools of normal and breast cancer libraries further verified the presence of significant downregulation of expression levels of 4 of the kallikreins genes (KLK5, 6, 10, 12). We experimentally verified the downregulation of these four kallikreins (KLK5, 6, 8, 10 and 12) by RT – PCR analysis.

Favorable prognostic value of tissue human kallikrein 11 (hK11) in patients with ovarian carcinoma

Human kallikrein 11 (hK11/trypsin-like serine protease/TLSP, encoded by the KLK11 gene) is a member of the kallikrein family of secreted serine proteases. Recently, we developed a highly sensitive and specific immunoassay for hK11 and found that this protease is expressed in the prostate, stomach and trachea as well as in amniotic fluid and milk of lactating women. Elevated serum hK11 levels were found in 60% of men with prostate cancer and 70% of women with ovarian cancer. Also, hK11 expression was found to be under the regulation of steroid hormones, particularly estrogens, at the level of KLK11 transcription. We hypothesized that hK11 may be implicated in endocrine-related malignancies and serve as a novel prostate and ovarian cancer serological marker. The aim of our study was to examine if hK11 expression in ovarian tumors bears any prognostic significance. The concentration of hK11 (ng per mg of total protein) in 104 ovarian tumor cytosolic extracts was quantified and correlated with clinicopathologic variables and outcome over a median follow-up period of 67 months. Outcome was defined as progression-free survival (PFS) and overall survival (OS). hK11 concentration in ovarian tumor cytosols ranged from 0-21 ng/mg of total protein, with a median of 0.54 ng/mg. An optimal cutoff value of 0.54 ng/mg was selected to categorize tumors as hK11-positive or -negative. hK11-positive tumors were more frequently associated with early stage (Stage I/II) disease, pre-/peri-menopausal status and patients who exhibited complete or partial response to chemotherapy (p < 0.05). Univariate analysis revealed that patients with hK11-positive tumors had a significantly decreased risk of relapse with a hazard ratio (HR) of 0.45 (p = 0.007) and death (HR of 0.34, p = 0.005). Cox multivariate analysis indicated that hK11 was an independent prognostic indicator of OS (HR of 0.41, p = 0.025). Kaplan-Meier survival curves further confirmed that women with hK11-positive tumors have longer PFS and OS (p = 0.005 and p = 0.003, respectively). Similarly, in the subgroup of patients with grade 1-2 tumors, hK11-positivity was associated with higher OS in both univariate and multivariate analysis (HR of 0.23 and 0.17, p < 0.05). Finally, in women with optimal debulking after surgery (<1 cm residual tumor), hK11 positivity was associated with a slower disease progression. These results indicate that hK11 is a novel, independent marker of favorable prognosis in patients with ovarian cancer.

An overview of the kallikrein gene families in humans and other species: emerging candidate tumour markers

Kallikreins are serine proteases with diverse physiologic functions. They are represented by multigene families in many animal species, especially in rat and mouse. Recently, the human kallikrein gene family has been fully characterized and includes 15 members, tandemly localized on chromosome 19q13.4. A new definition has now been proposed for kallikreins, which is not based on function but, rather, on close proximity and structural similarities. In this review, we summarize available information about kallikreins in many animal species with special emphasis on human kallikreins. We discuss the common structural features of kallikreins at the DNA, mRNA and protein levels and overview their evolutionary history. Kallikreins are expressed in a wide range of tissues including the salivary gland, endocrine or endocrine-related tissues such as testis, prostate, breast and endometrium and in the central nervous system. Most, if not all, genes are under steroid hormone regulation. Accumulating evidence indicates that kallikreins are involved in many pathologic conditions. Of special interest is the potential role of kallikreins in the central nervous system. In addition, many kallikreins seem to be candidate tumor markers for many malignancies, especially those of endocrine-related organs.

Prognostic value of the human kallikrein gene 15 expression in ovarian cancer

PURPOSE

KLK15 is a newly cloned human kallikrein gene. Many kallikreins were found to be differentially expressed in ovarian cancer. Like other kallikreins, KLK15 is regulated by steroid hormones in cancer cell lines. KLK15 is upregulated mainly by androgens and to a lesser extent by progestins. The purpose of this study was to examine the prognostic value of KLK15 in ovarian cancer tissues.

MATERIALS AND METHODS

We studied KLK15 expression by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in 168 consecutive patients with epithelial ovarian cancer. Ten patients with benign ovarian tumors were also included in the study. An optimal cutoff point equal to the 50th percentile was defined based on the ability of KLK15 to predict progression-free survival and overall survival of the study population.

RESULTS

KLK15 expression levels were significantly higher in cancerous tissues compared with benign tumors. Kaplan-Meier survival curves showed that KLK15 overexpression is a significant predictor of reduced progression-free survival (PFS; P <.001) and overall survival (OS; P <.009). Univariate and multivariate analyses indicate that KLK15 is an independent prognostic factor for PFS and OS. A weak positive correlation was found between KLK15 expression and serum CA-125 levels.

CONCLUSION

KLK15 expression, as assessed by quantitative RT-PCR, is an independent marker of unfavorable prognosis for ovarian cancer.